Behringer active crossover
 

I ordered a Behringer 3-way active crossover...

http://www.behringer.com/CX3400/index.cfm?lang=ENG

....on Sunday, and it arrived yesterday. I've set it up for phase 1 of the
tri-amping project - splitting the top/mid from the bass. The following is
what I wrote last night in an email to a couple of mates. (For those that
don't already know, the Arcam Alpha is an original Mk1 version, and the
valve amp is a Maplin Millennium 4-20 kit that I built a few years ago.
Speakers are Kef B139/B110/T27 in home-brew reflex boxes with DN12
crossovers, and source is CD through a Meridian 203 DAC.)

---------------------
Currently, the Cyrus 2 is driving the bass, and I'm using the Arcam Alpha
for the top/mid. I disconnected the wires going to the bass driver, and
soldered them to binding posts - they are directly connected to the Cyrus,
with no passive crossover components between amp and speaker. The top/mid
are still being driven through the original Kef passive crossover, including
the bits that cut off the bass frequencies to the mid driver.

The Kef crossover frequency between bass and mid is 400Hz, but I've found
that setting the active crossover to this gave me a rather muddy sound on
the upper bass. Initial tweaking would suggest that something around
120-200Hz gives a better balance - need to play with this more.

Initial impressions are that the bass is more solid, and that the overall
sound is tighter. I'm surprised at the little Arcam Alpha - it's doing a
much better job with the top/mid than I expected. Gwyneth Herbert was quite
striking - she was bang in the middle of the speakers and very 'present' -
getting this with most music. Everything seems more 'coherent'.

There's a feeling that there's more low bass, but playing the test CD I made
with the sequence of single frequencies would suggest otherwise - the
noticable roll-off from about 60-70Hz downwards is still there. Whether the
roll-off will be as pronounced when the bass drivers are reboxed (and
doubled up) remains to be seen - I suspect there will still be losses at the
really low end, so I think some sort of EQ will eventually make its way into
the bass end.

Just swapped over to the valve amp after spending the last few hours using
the Arcam - it definitely has better resolution. There's more detail, and
everything sounds a bit more real, more 'open' - a better impression of the
acoustics of the recording room on some Sinatra tracks. The Arcam does seem
to put a veil over the sound. The problem with the valve amp is that it
doesn't produce its best at higher volumes - it seems to struggle a little
where the Arcam was coping better. The difference was apparent when I tried
Bailero by yon mezzosoprano at a fair old volume - her voice was a bit
roughish sounding through the Arcam, but more shouty through the valve amp
(it was this track that led me to change to the valve amp - the Arcam was
clearly not coping). Keeping the volume below the limits of the top/mid
amps, however, the valve amp kicks the **** out of the Arcam.

About the only downsides so far are a rather big pile of equipment, and a
fourth plateful of spaghetti hanging out the back. And the row of LEDs on
the crossover - these pro audio peeps need LEDs to tell them stuff about the
gear when in dark venues, but I could happily do without them. I'm thinking
of moving the power amps, the crossover, and the DAC out of the way (maybe
onto the corner of the desk), since I only really need the CD player, the
pre-amp and the Telewest box to be visible and easily accessible.

So far, then, the crossover looks like being a plus, with the potential for
being a serious improvement when the rest of the kit is sorted out.
---------------------

Been looking at more Behringer stuff this evening, and their Feedback
Destroyer thingy looks interesting - it also functions as a stereo 12-band
parametric EQ. Maker's product page is here...

http://www.behringer.com/DSP1124P/index.cfm?lang=eng

It's a DSP jobbie and, from what I can gather, each band can be set to any
frequency, and at 1/60th octave increments, no less. If it can function
slely as an EQ (ie, feedback-killer function switched off) I'm thinking of
getting one for the purpose of sorting out the bass response - it would go
between the crossover and the bass amp. Does anyone have any experience with
this bit of kit?


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

"Wally" wrote in message
...
I ordered a Behringer 3-way active crossover...

http://www.behringer.com/CX3400/index.cfm?lang=ENG

...on Sunday, and it arrived yesterday. I've set it up for phase 1 of the
tri-amping project - splitting the top/mid from the bass. The following is
what I wrote last night in an email to a couple of mates. (For those that
don't already know, the Arcam Alpha is an original Mk1 version, and the
valve amp is a Maplin Millennium 4-20 kit that I built a few years ago.
Speakers are Kef B139/B110/T27 in home-brew reflex boxes with DN12
crossovers, and source is CD through a Meridian 203 DAC.)

---------------------
Currently, the Cyrus 2 is driving the bass, and I'm using the Arcam Alpha
for the top/mid. I disconnected the wires going to the bass driver, and
soldered them to binding posts - they are directly connected to the Cyrus,
with no passive crossover components between amp and speaker. The top/mid
are still being driven through the original Kef passive crossover,
including
the bits that cut off the bass frequencies to the mid driver.

The Kef crossover frequency between bass and mid is 400Hz, but I've found
that setting the active crossover to this gave me a rather muddy sound on
the upper bass. Initial tweaking would suggest that something around
120-200Hz gives a better balance - need to play with this more.

Initial impressions are that the bass is more solid, and that the overall
sound is tighter. I'm surprised at the little Arcam Alpha - it's doing a
much better job with the top/mid than I expected. Gwyneth Herbert was
quite
striking - she was bang in the middle of the speakers and very 'present' -
getting this with most music. Everything seems more 'coherent'.

There's a feeling that there's more low bass, but playing the test CD I
made
with the sequence of single frequencies would suggest otherwise - the
noticable roll-off from about 60-70Hz downwards is still there. Whether
the
roll-off will be as pronounced when the bass drivers are reboxed (and
doubled up) remains to be seen - I suspect there will still be losses at
the
really low end, so I think some sort of EQ will eventually make its way
into
the bass end.

Just swapped over to the valve amp after spending the last few hours using
the Arcam - it definitely has better resolution. There's more detail, and
everything sounds a bit more real, more 'open' - a better impression of
the
acoustics of the recording room on some Sinatra tracks. The Arcam does
seem
to put a veil over the sound. The problem with the valve amp is that it
doesn't produce its best at higher volumes - it seems to struggle a little
where the Arcam was coping better. The difference was apparent when I
tried
Bailero by yon mezzosoprano at a fair old volume - her voice was a bit
roughish sounding through the Arcam, but more shouty through the valve amp
(it was this track that led me to change to the valve amp - the Arcam was
clearly not coping). Keeping the volume below the limits of the top/mid
amps, however, the valve amp kicks the **** out of the Arcam.

About the only downsides so far are a rather big pile of equipment, and a
fourth plateful of spaghetti hanging out the back. And the row of LEDs on
the crossover - these pro audio peeps need LEDs to tell them stuff about
the
gear when in dark venues, but I could happily do without them. I'm
thinking
of moving the power amps, the crossover, and the DAC out of the way (maybe
onto the corner of the desk), since I only really need the CD player, the
pre-amp and the Telewest box to be visible and easily accessible.

So far, then, the crossover looks like being a plus, with the potential
for
being a serious improvement when the rest of the kit is sorted out.
---------------------

Been looking at more Behringer stuff this evening, and their Feedback
Destroyer thingy looks interesting - it also functions as a stereo 12-band
parametric EQ. Maker's product page is here...

http://www.behringer.com/DSP1124P/index.cfm?lang=eng

It's a DSP jobbie and, from what I can gather, each band can be set to any
frequency, and at 1/60th octave increments, no less. If it can function
slely as an EQ (ie, feedback-killer function switched off) I'm thinking of
getting one for the purpose of sorting out the bass response - it would go
between the crossover and the bass amp. Does anyone have any experience
with
this bit of kit?

Never used the DSP1124 but I have a http://www.behringer.com/DSP8024/

great value for money!

Ben

Behringer active crossover
 

Just bought another amp so going back to passive bi-amping, then maybe later
on could bypass
internal speaker crossovers. Just how much work is involved dialling in
crossovers on the rack unit? Ruark Epilogue speakers

I know Bryston make a active crossover..

http://www.bryston.ca/crossel.html

Pretty expensve though..

Behringer active crossover
 

In article , Wally
wrote:
I ordered a Behringer 3-way active crossover...

[snip]

The Kef crossover frequency between bass and mid is 400Hz, but I've
found that setting the active crossover to this gave me a rather muddy
sound on the upper bass. Initial tweaking would suggest that something
around 120-200Hz gives a better balance - need to play with this more.

The 'crossover frequency' specified for most speakers is a fairly 'nominal'
value. Also, if you are simply splitting the links I assume the internal LP
and HP filters in the speakers are still in the signal paths. Thus the
'best' setting for your active crossover/filter may be quite different to
that specified for the speaker when used 'normally'.

Initial impressions are that

[big snip]

If you can make up CDs of test sinewaves, etc, and have access to a
reliable sound pressure meter, then it would be interesting to see to what
extent the differences you hear correlate with any changes in overall
frequency response being produced by the active crossover, differences in
gain of the two power amps, and effects of the output impedances of the
amps.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

Jim Lesurf wrote:

The 'crossover frequency' specified for most speakers is a fairly
'nominal' value.

Yup, I can appreciate that.


Also, if you are simply splitting the links I assume
the internal LP and HP filters in the speakers are still in the
signal paths. Thus the 'best' setting for your active
crossover/filter may be quite different to that specified for the
speaker when used 'normally'.

No links as such - 3-way speakers with the bass drivers disconnected from
the passive crossovers and wired straight to the bass amp. The remaining
two-way pair are still connected to a single amp, going through the full
3-way crossover (with the LF output open circuit).

I'm thinking of converting to the two-way Kef crossover for splitting the
B110 and T27 (this version has no high-pass element on the B110 cct, since
the B110 is acting as bass and mid in a two-way set up). The B110 is in its
own IB sub-enclosure within the main cabinet. Do you think this is worth
pursuing, or would there be some sort of 'conflict' of B110 roll-off in the
sub-enclosure, compared with the 24dB/octave low-pass that the active
crossover applies to the bass driver?


If you can make up CDs of test sinewaves, etc, and have access to a
reliable sound pressure meter, then it would be interesting to see to
what extent the differences you hear correlate with any changes in
overall frequency response being produced by the active crossover,
differences in gain of the two power amps, and effects of the output
impedances of the amps.

Urrr..., I can make test CDs of sine waves. :-) (With a bit of software I
had on my old computer - would need to find it and reinstall.) Don't have a
sound pressure meter, I'm afraid. I suppose the Cyrus 2 has more gain than
the valve amp. I think their input sensitivities are roughly similar
(200-300mV for full power). The valve amp (20-ish Watts) is set to half
volume, the Cyrus (50W) at about '3', and the gains/cuts on the active
crossover are all set to 0dB. This seems to produce a balanced sound. The
overall volume is controlled by a preamp.

It's all calibrated with the indubitably dubious power of the human
lug-'ole - but it's my lug-'ole, and that's the one that matters. :-) My
impression of the Behringer is that it's essentially flat - without a set of
before and after measurements, I'm assuming that the feeling of better
clarity and improved bass is down to having more power available, and
perhaps splitting bass and mid/top to separate amps.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

Nath wrote:
Just bought another amp so going back to passive bi-amping, then
maybe later on could bypass
internal speaker crossovers. Just how much work is involved dialling
in crossovers on the rack unit? Ruark Epilogue speakers

Very little, it would seem - connect the stuff up, select the right mode,
set all the gains to 0dB, tweak the crossover frequency(ies) until it sounds
right. Note that the Behringer uses XLR connectors - you'll need adapters if
you want to connect to kit that uses phono sockets.


I know Bryston make a active crossover..
http://www.bryston.ca/crossel.html
Pretty expensve though..

I'm very impressed with the Behringer so far - I half-expected some
softening of the detail, but, if anything, it all seems a touch better.
Amazing value at 90 quid delivered.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

Ben wrote:

Never used the DSP1124 but I have a http://www.behringer.com/DSP8024/

Can't find it in the UK price list - what does it cost?


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

"Wally" wrote in message
...
Ben wrote:

Never used the DSP1124 but I have a http://www.behringer.com/DSP8024/

Can't find it in the UK price list - what does it cost?


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

£90-£110. Used to EQ your sub, but can be used full-range EQ as well.

Behringer active crossover
 

Nath wrote:

£90-£110. Used to EQ your sub, but can be used full-range EQ as well.

The DSP1124 is about 70-90 quid, but doesn't seem to have that RTA
calibration thingy. From what I can gather, you connect a mic to the 8024,
hit a few buttons, and it sets up the graphic to give a flat (or
otherwise-specified) response? I wasn't really thinking of full-range EQ,
just the bass, which was why I thought the 1124 would be a better idea - the
12 parametric bands can all be bunched at the low end. That said, the 8024
looks like it might do the business anyway, given that it has 3 1/60th
octave parametrics as well. It also has better specs...

-------------------------
8024:
Bandwidth 20 Hz to 20 kHz (+0/-0.5 dB)

Signal to Noise Ratio 103 dB unweighted, 22 Hz to 22 kHz

THD+N 0.004 % @ 1 kHz / +4 dBu

Crosstalk -103dB, 22 Hz to 22 kHz

-------------------------
1124:
Bandwidth 20 Hz to 20 kHz, -3 dB

Noise 94 dB, unweighted, 20 Hz to 20 kHz

THD 0.0075 % typ. @ +4 dBu, 1 kHz, Gain 1

Crosstalk -76 dB

-------------------------

Could you suggest a UK supplier for the DSP8024? Google doesn't seem to be
revealing any.



--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

Lots of info here about 1124p, it is used for LF EQ'ing..

http://www.snapbug.ws/bfd.htm

if you want more advanced PEQ for full-range, also checkout 2496.

http://www.behringer.com/DEQ2496/index.cfm?lang=ENG

Behringer active crossover
 

Nath wrote:
Lots of info here about 1124p, it is used for LF EQ'ing..

http://www.snapbug.ws/bfd.htm

Looks interesting - I'll have a better read later, but I'm currently feeling
that the 8024 might be the better (more transparent?) bit of kit, if the
specs are anything to go by.


if you want more advanced PEQ for full-range, also checkout 2496.

http://www.behringer.com/DEQ2496/index.cfm?lang=ENG

Too pricey. :-)


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

In article , Wally
wrote:
Jim Lesurf wrote:

Also, if you are simply splitting the links I assume the internal LP
and HP filters in the speakers are still in the signal paths. Thus the
'best' setting for your active crossover/filter may be quite different
to that specified for the speaker when used 'normally'.

No links as such - 3-way speakers with the bass drivers disconnected
from the passive crossovers and wired straight to the bass amp. The
remaining two-way pair are still connected to a single amp, going
through the full 3-way crossover (with the LF output open circuit).

IIUC the above means that the HF signals now go through the same network as
before, but with the LF speaker disconnected from that network.

Two comments on that:

1) If the LF speaker was previously connected via that network, it may now
be producing a different frequency response than before.

2) Removing the impedance of the LF speaker from the network may also
change the response of the network/HF speakers.

Hence in addition to other factors, the changes indicated above may change
the frequency response of the system.

I'm thinking of converting to the two-way Kef crossover for splitting
the B110 and T27 (this version has no high-pass element on the B110 cct,
since the B110 is acting as bass and mid in a two-way set up). The B110
is in its own IB sub-enclosure within the main cabinet. Do you think
this is worth pursuing, or would there be some sort of 'conflict' of
B110 roll-off in the sub-enclosure, compared with the 24dB/octave
low-pass that the active crossover applies to the bass driver?

Not sure what might be meant by 'conflict'. However the B110 and its
enclosure presumable have a given frequency response and set of
resonances, etc. Just driving directly from a flat amp with a LP roll-off
may not deal with this. Hard to say as I'm afraid I don't know the
specifics of the actual arrangement. Rolling away the HF will avoid things
like cone breakup resonances. However in the region where both the LF and
HF speakers are active their outputs will combine and this will also have
effects that will be quite specific to the individual arrangement.

The above is a long-winded way of daying "Dunno". :-)

TBH though, personally I would not embark on speaker development/design
without having access to some kit to measure the response, etc. There are
simply too many variables and potential problems which I'd find too hard to
disentagle simply 'by ear'.

If you can make up CDs of test sinewaves, etc, and have access to a
reliable sound pressure meter, then it would be interesting to see to
what extent the differences you hear correlate with any changes in
overall frequency response being produced by the active crossover,
differences in gain of the two power amps, and effects of the output
impedances of the amps.

Urrr..., I can make test CDs of sine waves. :-) (With a bit of software
I had on my old computer - would need to find it and reinstall.) Don't
have a sound pressure meter, I'm afraid. I suppose the Cyrus 2 has more
gain than the valve amp. I think their input sensitivities are roughly
similar (200-300mV for full power). The valve amp (20-ish Watts) is set
to half volume, the Cyrus (50W) at about '3', and the gains/cuts on the
active crossover are all set to 0dB. This seems to produce a balanced
sound. The overall volume is controlled by a preamp.

The problem here is not just that the two power amps may have different
gains. They may also have different output impedances. In particular if the
valve amp has a 'high' output impedance this will produce a different
frequency response to an amp with a 'low' output impedance.

It's all calibrated with the indubitably dubious power of the human
lug-'ole - but it's my lug-'ole, and that's the one that matters. :-)
My impression of the Behringer is that it's essentially flat - without a
set of before and after measurements, I'm assuming that the feeling of
better clarity and improved bass is down to having more power available,
and perhaps splitting bass and mid/top to separate amps.

Alas, I have my doubts that the reason you assume is the correct one.
Unless the amps were seriously current limiting I doubt that the biamping
will have had very much effect on the power levels available. Could you
hear previously clear signs of clipping?

The problem is that the changes you perceive may simply be due to you
altering the overall frequency response. This seems particularly likely
(and your assumption unlikely) if you hear the benefits at moderate to low
sound levels as well as at peak levels.

If the results sound better to you, that is fair enough as you have a
result you prefer. For that your lug-ole is king.

However it means that if that *is* the reason, then similar results might
be obtained by much cheaper and easier means. This may not matter to you at
this point, but if it were the case, knowing this might save others time
and money. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

"Jim Lesurf" wrote in message
...
In article , Wally
wrote:
Jim Lesurf wrote:
..
It's all calibrated with the indubitably dubious power of the human
lug-'ole - but it's my lug-'ole, and that's the one that matters. :-)
My impression of the Behringer is that it's essentially flat - without a
set of before and after measurements, I'm assuming that the feeling of
better clarity and improved bass is down to having more power available,
and perhaps splitting bass and mid/top to separate amps.

..
If the results sound better to you, that is fair enough as you have a
result you prefer. For that your lug-ole is king.

However it means that if that *is* the reason, then similar results might
be obtained by much cheaper and easier means. This may not matter to you
at
this point, but if it were the case, knowing this might save others time
and money. :-)

I'm not in a position to give any results yet, but I am experimenting along
the lines of Wally's ideas. For me they were a necessity because of the
need to fill a larger room. I was not able to get the power I needed from
a single twin amp so decided to try out using three. I have a Behringer
3400 XO and so far am very pleased. Its not there acoustically. I'm using
a Cyrus preamp feeding the XO which drives two InterMn500W
amps, one for two-way Mordaunt-Short floorstanders for the mid
and one for the sub. I am about to use two tweeters run off a NAD
amplifier in addition to the two in the MSs. The MS top will be rolled off.
I
don't know what crossover frequency I will use. And yes, I will be
assessing by ear. If I don't get what I want after playing I'll hook
up a sig gen and use a level meter to find out what's wrong with the
response curve.

It'll be a week or so. I'll post anything useful that I discover.

Peter Scott

Behringer active crossover
 

In article , Peter Scott
wrote:


I'm not in a position to give any results yet, but I am experimenting
along the lines of Wally's ideas. For me they were a necessity because
of the need to fill a larger room. I was not able to get the power I
needed from a single twin amp so decided to try out using three.

I have doubts that bi or even tri amping should usually make a big
difference to the sound levels you can obtain. This assumes, though, that:

1) Your initial amp wasn't current limiting due to the parallel loads of
the speakers.

2) You aren't using the active xover to avoid large losses in the initial
passive xover arrangements in the speakers.

If either of the above were the case, then the following comments may not
apply...

For getting the biggest possible increase in peak power you'd have to get a
situation where the vectors (voltages) of the bandsplit signals were all in
phase and of the same sign and amplitude. In this extreme case you might
get a peak improvement of x9 in power. i.e. less than 10dB, which in terms
of audibility tends to be regarded as impying you would never get more than
an apparent doubling in peak level.

However in practice I suspect you will find that almost all the time the
vectors are neither in phase nor of equal size. Thus the increase in
available power is likely to be much less than the above.

FWIW I did some analysis of the peak levels of band-divided musical signals
from CD when looking at clipping and tweeters (some pages on this on the
'Scots Guide' site). Can't be sure, but I'd be surprised if in general you
got much more than a few dB of sound level increase before occasional
clipping. i.e. not much more than the smallest change that is clearly
noticable.

You may, however, get an apparent increase if the frequency response
changes as that may affect the audibility and the audible impression
conveyed. However as with Wally's experiments, if this is the case, then
similar results might be obtained more easily.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

Jim Lesurf wrote:

IIUC the above means that the HF signals now go through the same
network as before, but with the LF speaker disconnected from that
network.

Yup. Well, mid and high still go through the network, and bass bypasses it.


Two comments on that:

1) If the LF speaker was previously connected via that network, it
may now be producing a different frequency response than before.

Okay. Maybe that would explain why the bass seemed a bit muddy (and a bit
too loud) when the active crossover was set to 400Hz. Would it be fair to
say that the low-end roll off (70Hz downwards) would still be more
influenced by the cabinet/room?


2) Removing the impedance of the LF speaker from the network may also
change the response of the network/HF speakers.

Hence in addition to other factors, the changes indicated above may
change the frequency response of the system.

Righto. Very interesting...




Not sure what might be meant by 'conflict'.

I mean a mismatch in the roll-off of the B110 in its sub-enclosure, compared
with that imposed on the B139 by the active filter (the B110 is set up as a
mid driver and the IB enclosure is quite small - I don't know what the
resonant frequency of the midrange system is, but I suspect it's rather
higher than that of the driver itself, which is 38Hz). Aren't the slopes
supposed to be similar in terms of dB/octave?


However the B110 and its
enclosure presumable have a given frequency response and set of
resonances, etc. Just driving directly from a flat amp with a LP
roll-off may not deal with this. Hard to say as I'm afraid I don't
know the specifics of the actual arrangement. Rolling away the HF
will avoid things like cone breakup resonances. However in the region
where both the LF and HF speakers are active their outputs will
combine and this will also have effects that will be quite specific
to the individual arrangement.

Not sure we're talking about the same thing - the B110 is acting as a
midrange driver. Its LF response is rolled off both by the HP portion of the
passive crossover and the size of its sub-enclosure. The B139 is being
driven by a flat amp with a LP filter before it. The LF signal to the B110
is also being restricted by the bass/mid crossover frequency in the
Behringer. However, switching off the bass amp and tweaking the active xover
freq reveals that it has a little effect on the B110 below about 250-300Hz;
from about 200Hz downward is only very slight. In other words, the
now-redundant bass/mid parts of the passive crossover could be causing the
roll-off on the B110, or its sub-enclosure, or a combnation of both. What
I'm wondering is, would it be a good idea to remove the passive xover
components and have only the sub-enclosure acting to roll off the B110s bass
response? I appreciate that, without knowing the specifics, this might not
be answerable. :-)



TBH though, personally I would not embark on speaker
development/design without having access to some kit to measure the
response, etc. There are simply too many variables and potential
problems which I'd find too hard to disentagle simply 'by ear'.

The way I see it, I can always undo the changes I make. If I don't like a
change, I can revert to the previous configuration.


The problem here is not just that the two power amps may have
different gains. They may also have different output impedances. In
particular if the valve amp has a 'high' output impedance this will
produce a different frequency response to an amp with a 'low' output
impedance.

The spec for the Cyrus 2 quotes 0.08 ohms, can't find a number for the valve
amp. FWIW, I've always felt that both amps have a similar character to the
sound - ie, pretty clean and flat when used within their available headroom.
By contrast, both amps are substantially better than the Arcam Alpha -
they're much closer to each other than either is to the Arcam.


... I'm assuming that
the feeling of better clarity and improved bass is down to having
more power available, and perhaps splitting bass and mid/top to
separate amps.

Alas, I have my doubts that the reason you assume is the correct one.
Unless the amps were seriously current limiting I doubt that the
biamping will have had very much effect on the power levels
available. Could you hear previously clear signs of clipping?

When each was used to amplify the full range, the Cyrus was louder than the
valve amp, and stayed clean for longer. However, they both reached a point
where I felt the sound became unpleasant to listen to. Whether or not that
was clipping, I'm not sure - to me, that term denotes what you get when a
guitar amp is turned up to the point where it sounds like a chainsaw. I
don't let the hifi get anything like that bad, so I'm not sure it's clipping
that I'm hearing, or some other effect. I sometmes wonder if the speakers
themselves were being overloaded, but I don't think this would be likely in
the case of the valve amp - the Cyrus can easily match it in terms of
in-room volume, and stays cleaner as it does so.


The problem is that the changes you perceive may simply be due to you
altering the overall frequency response. This seems particularly
likely (and your assumption unlikely) if you hear the benefits at
moderate to low sound levels as well as at peak levels.

I haven't listened much at low volumes since I added the active crossover
(rather, only had it on as background music and not been paying attention).
Generally, though, I think it still sounds cleaner.


If the results sound better to you, that is fair enough as you have a
result you prefer. For that your lug-ole is king.

However it means that if that *is* the reason, then similar results
might be obtained by much cheaper and easier means. This may not
matter to you at this point, but if it were the case, knowing this
might save others time and money. :-)

Maybe that depends on what is causing the change in frequency response. The
overall aim of this is to add headroom to be sure that the amplification
isn't a factor at high volumes, and to possibly improve the fidelity by
removing the passive crossovers. It started with the plan to double up the
bass drivers by converting them to a pair of isobaric enclosures - it seemed
that the easiest way to account for the change in impedance at the bass end,
but not at the mid or top, was to split the amplification up. I then thought
that, if I'm going to bin the passive crossovers at the bass end, then it
might not hurt to bin them altogether.

It would be fair to say that my curiosity has been piqued, and I'm quite
happy to the follow the tri-amping route just to find out what it sounds
like.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

In article , Wally
wrote:
Jim Lesurf wrote:
[snip]


Two comments on that:

1) If the LF speaker was previously connected via that network, it may
now be producing a different frequency response than before.

Okay. Maybe that would explain why the bass seemed a bit muddy (and a
bit too loud) when the active crossover was set to 400Hz. Would it be
fair to say that the low-end roll off (70Hz downwards) would still be
more influenced by the cabinet/room?

Hard to be sure. However the above seems plausible. In general the LF
roll-away at frequencies below 50-100 Hz region does tend to be dominated
by how easily the speaker can produce pressure variations in the room.
Ideally, an infinite baffle speaker in an airtight room with no leaks and
firm walls would allow a response down to dc.! :-) In practice, though, the
LF response will depend on how much air pressure change the room will
experience for a given cone movement once you are below the lowest room
resonance.

FWIW my experience here is limited, but it is that there are two problems
which may combine if you are unlucky. One is the basic room pressure
resonance which will probably be somewhere below 100Hz. The other is the
'mechanical' resonance of the speaker cone mass/compliance which will also
be somewhere below 100Hz. If the two are at a similar frequency they may
produce a particularly severe 'boom', and the bass may fall away rapidly
below this. Which is 'more significant' will depend on the details of your
situation.

With the sub I use in my living room I can measure a change in the peak
frequency and level if I open/close the room door.

IIUC commercial subwoofers employ an amp with a correction network to try
and iron out some of the speaker effects and give a more extended response.
You'd need to experiment to determine what was required for a given system.


Not sure what might be meant by 'conflict'.

I mean a mismatch in the roll-off of the B110 in its sub-enclosure,
compared with that imposed on the B139 by the active filter (the B110 is
set up as a mid driver and the IB enclosure is quite small - I don't
know what the resonant frequency of the midrange system is, but I
suspect it's rather higher than that of the driver itself, which is
38Hz). Aren't the slopes supposed to be similar in terms of dB/octave?

Not sure. The amount of output (sensitivity) will vary in a different way
to the actual drive levels. With HF speakers you need to avoid LF as the
excursions might cause problems. With LF speakers you avoid HF as it can
excite cone resonances. So the degree of attenuation required depends on
different factors as well. However I'm not a speaker designer so don't know
much about the details of practical designs.


However the B110 and its enclosure presumable have a given frequency
response and set of resonances, etc. Just driving directly from a flat
amp with a LP roll-off may not deal with this. Hard to say as I'm
afraid I don't know the specifics of the actual arrangement. Rolling
away the HF will avoid things like cone breakup resonances. However in
the region where both the LF and HF speakers are active their outputs
will combine and this will also have effects that will be quite
specific to the individual arrangement.

Not sure we're talking about the same thing - the B110 is acting as a
midrange driver. Its LF response is rolled off both by the HP portion of
the passive crossover and the size of its sub-enclosure. The B139 is
being driven by a flat amp with a LP filter before it. The LF signal to
the B110 is also being restricted by the bass/mid crossover frequency in
the Behringer. However, switching off the bass amp and tweaking the
active xover freq reveals that it has a little effect on the B110 below
about 250-300Hz; from about 200Hz downward is only very slight. In other
words, the now-redundant bass/mid parts of the passive crossover could
be causing the roll-off on the B110, or its sub-enclosure, or a
combnation of both. What I'm wondering is, would it be a good idea to
remove the passive xover components and have only the sub-enclosure
acting to roll off the B110s bass response? I appreciate that, without
knowing the specifics, this might not be answerable. :-)

Afraid I have to go along with your final comments. :-) I don't know
enough to say for sure.

TBH though, personally I would not embark on speaker
development/design without having access to some kit to measure the
response, etc. There are simply too many variables and potential
problems which I'd find too hard to disentagle simply 'by ear'.

The way I see it, I can always undo the changes I make. If I don't like
a change, I can revert to the previous configuration.

Yes. The snag, though, is the phenomenon I tend to call "lost in space".
This is where there are many variables you can fiddle with, or which alter
out of your control. This means as you change some things you sometimes
don't know what is really happening, or if some other slight change would
be desirable, etc. This is worse when working entirely 'by ear' as your
reactions will vary according to how you feel and your 'recent'
experiences, and affected by the unreliability of memory.

The problem here is not just that the two power amps may have
different gains. They may also have different output impedances. In
particular if the valve amp has a 'high' output impedance this will
produce a different frequency response to an amp with a 'low' output
impedance.

The spec for the Cyrus 2 quotes 0.08 ohms, can't find a number for the
valve amp.

Afraid I don't know any figures for the valve amp you mentioned. However if
you look in reviews, values when quoted are often of the order of 0.5 Ohms
or more. i.e. somewhat larger than the value for your Cyrus,


... I'm assuming that the feeling of better clarity and improved bass
is down to having more power available, and perhaps splitting bass
and mid/top to separate amps.

Alas, I have my doubts that the reason you assume is the correct one.
Unless the amps were seriously current limiting I doubt that the
biamping will have had very much effect on the power levels available.
Could you hear previously clear signs of clipping?

When each was used to amplify the full range, the Cyrus was louder than
the valve amp, and stayed clean for longer. However, they both reached a
point where I felt the sound became unpleasant to listen to. Whether or
not that was clipping, I'm not sure - to me, that term denotes what you
get when a guitar amp is turned up to the point where it sounds like a
chainsaw. I don't let the hifi get anything like that bad, so I'm not
sure it's clipping that I'm hearing, or some other effect. I sometmes
wonder if the speakers themselves were being overloaded, but I don't
think this would be likely in the case of the valve amp - the Cyrus can
easily match it in terms of in-room volume, and stays cleaner as it does
so.

Hard to say, but if the sound becomes unpleasant at high levels then I'd
expect that to be due to some mix of:

1) Amp clipping (voltage) or current limiting

2) Speaker distortions

3) Amp distortion levels rising with output levels

With 'traditional' valve designs (1) and (3) may be factors, but can't
really say without more details.

[snip]

If the results sound better to you, that is fair enough as you have a
result you prefer. For that your lug-ole is king.

However it means that if that *is* the reason, then similar results
might be obtained by much cheaper and easier means. This may not
matter to you at this point, but if it were the case, knowing this
might save others time and money. :-)

Maybe that depends on what is causing the change in frequency response.

Yes. Indeed, there are some good reasons for feeling that an active
crossover and 'direct drive' of the speaker units can be optimum. But this
then may well require the crossover to also do some other alterations to
cater for any inherent variations in sensitivity with frequency of the
speaker units. However it is difficult to say without more specific
measured data.

My concern here is that people may buy relatively expensive active
crossovers and bi- or tru-amp, but then get result which could have been
obtained more easily and cheaply with a slightly better amp and a tweaked
speaker or room acoustic. Hence I am inclined to be wary of this without
suitable measurements, etc.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

"Jim Lesurf" wrote in message
...
In article , Peter Scott
wrote:


FWIW I did some analysis of the peak levels of band-divided musical
signals
from CD when looking at clipping and tweeters (some pages on this on the
'Scots Guide' site). Can't be sure, but I'd be surprised if in general you
got much more than a few dB of sound level increase before occasional
clipping. i.e. not much more than the smallest change that is clearly
noticable.

You may, however, get an apparent increase if the frequency response
changes as that may affect the audibility and the audible impression
conveyed. However as with Wally's experiments, if this is the case, then
similar results might be obtained more easily.


I don't know if this is relevant, but the Behringer allows you to delay each
frequency band with respect to the others by up to 2 ms. This is intended
to pull speakers back into phase when one is further back than another.
Would this help with the potential problem you described?

I'm waiting for Studio Spares to deliver the connectors before I
can hook up the amp for the tweeters. Gnash, gnash!

Peter Scott

Behringer active crossover
 

In article , Peter Scott
wrote:

"Jim Lesurf" wrote in message
...
In article , Peter Scott
wrote:


FWIW I did some analysis of the peak levels of band-divided musical
signals
from CD when looking at clipping and tweeters (some pages on this on
the 'Scots Guide' site). Can't be sure, but I'd be surprised if in
general you got much more than a few dB of sound level increase before
occasional clipping. i.e. not much more than the smallest change that
is clearly noticable.

You may, however, get an apparent increase if the frequency response
changes as that may affect the audibility and the audible impression
conveyed. However as with Wally's experiments, if this is the case,
then similar results might be obtained more easily.


I don't know if this is relevant, but the Behringer allows you to delay
each frequency band with respect to the others by up to 2 ms. This is
intended to pull speakers back into phase when one is further back than
another. Would this help with the potential problem you described?

Sorry, I'm not clear which specific problem you are referring to above. Can
you remind me?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

"Jim Lesurf" wrote in message
...
In article , Peter Scott
wrote:



I don't know if this is relevant, but the Behringer allows you to delay
each frequency band with respect to the others by up to 2 ms. This is
intended to pull speakers back into phase when one is further back than
another. Would this help with the potential problem you described?

Sorry, I'm not clear which specific problem you are referring to above.
Can
you remind me?

OK Wrong word. I meant the fact that you might not get as great an
increase in perceived power as you might expect.

Peter Scott

Behringer active crossover
 

Jim Lesurf wrote:

Hard to be sure. However the above seems plausible. In general the LF
roll-away at frequencies below 50-100 Hz region does tend to be
dominated by how easily the speaker can produce pressure variations
in the room. Ideally, an infinite baffle speaker in an airtight room
with no leaks and firm walls would allow a response down to dc.! :-)
In practice, though, the LF response will depend on how much air
pressure change the room will experience for a given cone movement
once you are below the lowest room resonance.

Well, I don't have an ideal environment, or speakers, so I think I'm going
to the Behringer digital parametric EQ shop... :-)


FWIW my experience here is limited, but it is that there are two
problems which may combine if you are unlucky. One is the basic room
pressure resonance which will probably be somewhere below 100Hz. The
other is the 'mechanical' resonance of the speaker cone
mass/compliance which will also be somewhere below 100Hz. If the two
are at a similar frequency they may produce a particularly severe
'boom', and the bass may fall away rapidly below this. Which is 'more
significant' will depend on the details of your situation.

The way I see it, the only thing measurements will tell me is whether sound
I like has an even response, or a bumpy one. :-)


With the sub I use in my living room I can measure a change in the
peak frequency and level if I open/close the room door.

That's interesting - I'll bear that in mind for when I start doing bass EQ.


IIUC commercial subwoofers employ an amp with a correction network to
try and iron out some of the speaker effects and give a more extended
response. You'd need to experiment to determine what was required for
a given system.

That's pretty-much the plan. Now that the bass is separate from the rest, I
think my next step is to get the parametric gizmo and try doing some EQ on
the low end. I'd like to see how much improvement can be had from the
present set up, before I look into building new bass cabinets. (Before
someone tells me that I might not need it by then, I would like to mention
that I am already aware of this possibility.)


Not sure. The amount of output (sensitivity) will vary in a different
way to the actual drive levels. With HF speakers you need to avoid LF
as the excursions might cause problems. With LF speakers you avoid HF
as it can excite cone resonances. So the degree of attenuation
required depends on different factors as well. However I'm not a
speaker designer so don't know much about the details of practical
designs.

Okay, Fairy Nuff. :-)


Yes. The snag, though, is the phenomenon I tend to call "lost in
space". This is where there are many variables you can fiddle with,
or which alter out of your control. This means as you change some
things you sometimes don't know what is really happening, or if some
other slight change would be desirable, etc. This is worse when
working entirely 'by ear' as your reactions will vary according to
how you feel and your 'recent' experiences, and affected by the
unreliability of memory.

I appreaciate the somewhat non-scientific approach you're talking about, and
I admit that that's kinda what I'm doing. However, it's not so much about
the small incremental changes, it's the overall change that results from the
whole tri-amping thing. Using the active crossover to split the bass from
the rest of the system is just the first stage. I fully intend to get rid of
the passive crossovers, put the bass drivers into better boxes in an
isobaric configuration, equalise the limitations of the bass system and room
out of the equation as much as I can, and pile on the watts to be sure that
straining amplifiers aren't a factor.

Once it's got to that stage, *then* I ask myself if it's an improvement over
what I started with, establish what limitations there may be, and look into
ways of improving it further if I think that's warranted. I know I'll be
relying on memory of the previous configuration, but I have had these
speakers most of the last 25 years - they're the one thing in my system that
has never changed, so I reckon I'm pretty familiar with their sound. In
other words, aside from the memory aspect, which I think is mitigated, the
thing that I'm seeking to test is the difference between the old set up and
the tri-amped one. It'll be interesting to note the effects of the changes
that are made along the way to get to that point, but it's really the end
result that I want to check out.


Afraid I don't know any figures for the valve amp you mentioned.
However if you look in reviews, values when quoted are often of the
order of 0.5 Ohms or more. i.e. somewhat larger than the value for
your Cyrus,

I never did do an A-B comparison when I got the Cyrus - I just changed out
the valve amp and got on with it. My impression at the time was that the
fidelity of each amp was very similar - very difficult to separate them,
other than the Cyrus being capable of producing more clean volume. I don't
know what effect a higher o/p impedance would likely have.


Maybe that depends on what is causing the change in frequency
response.

Yes. Indeed, there are some good reasons for feeling that an active
crossover and 'direct drive' of the speaker units can be optimum. But
this then may well require the crossover to also do some other
alterations to cater for any inherent variations in sensitivity with
frequency of the speaker units. However it is difficult to say
without more specific measured data.

It strikes me that the basic principle is sound. I can't claim that the
drivers have a flat response in their working bandwidths, but I'm not aware
of the Kef passive crossovers having stuff in them to smooth out any
howlers. I stand to be corrected, but I gather they're basically dividing
networks.


My concern here is that people may buy relatively expensive active
crossovers and bi- or tru-amp, but then get result which could have
been obtained more easily and cheaply with a slightly better amp and
a tweaked speaker or room acoustic. Hence I am inclined to be wary of
this without suitable measurements, etc.

Cost is a factor, but, while I'm not willing to pay audiophile prices, I'm
willing to spend a bit to get a marked improvement over what I see as the
current system's shortcomings, which are primarily messy, uneven bass with
too much roll-off, and not enough clarity when played up loud. There's also
a curiosity factor, in that I want to see what difference is to be had by
eliminating the crossovers and driving the speakers directly.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

"Wally" wrote in message
...
Been looking at more Behringer stuff this evening, and their Feedback
Destroyer thingy looks interesting - it also functions as a stereo 12-band
parametric EQ. Maker's product page is here...

http://www.behringer.com/DSP1124P/index.cfm?lang=eng

It's a DSP jobbie and, from what I can gather, each band can be set to any
frequency, and at 1/60th octave increments, no less. If it can function
slely as an EQ (ie, feedback-killer function switched off) I'm thinking of
getting one for the purpose of sorting out the bass response - it would go
between the crossover and the bass amp.


Surely any DSP kit needs to go in the digital part of the system, i.e.
between the CD player and the DAC...?

Behringer active crossover
 

Rich Wilson wrote:

Surely any DSP kit needs to go in the digital part of the system, i.e.
between the CD player and the DAC...?

Why? I presume it has an ADC and DAC built in - if it's running some
algorithm on the digital stream between those two stages, then that's
digital signal processing, isn't it?


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

In article , Peter Scott
wrote:

"Jim Lesurf" wrote in message
...
In article , Peter Scott
wrote:



I don't know if this is relevant, but the Behringer allows you to
delay each frequency band with respect to the others by up to 2 ms.
This is intended to pull speakers back into phase when one is
further back than another. Would this help with the potential
problem you described?

Sorry, I'm not clear which specific problem you are referring to above.
Can
you remind me?

OK Wrong word. I meant the fact that you might not get as great an
increase in perceived power as you might expect.

OK. No, the ability to delay is unlikely to affect this very much - unless
the delays were so great as to disrupt the music.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

In article , Wally
wrote:
Jim Lesurf wrote:


FWIW my experience here is limited, but it is that there are two
problems which may combine if you are unlucky. One is the basic room
pressure resonance which will probably be somewhere below 100Hz. The
other is the 'mechanical' resonance of the speaker cone
mass/compliance which will also be somewhere below 100Hz. If the two
are at a similar frequency they may produce a particularly severe
'boom', and the bass may fall away rapidly below this. Which is 'more
significant' will depend on the details of your situation.

The way I see it, the only thing measurements will tell me is whether
sound I like has an even response, or a bumpy one. :-)

It can also provide you with information which can be studied and used to
indicate which further steps might (or might not) lead to further
improvements, perhaps more marked than so far obtained.

It can also provide a basis for you and others to assess if some other
methods might yeald similar results with less fuss or expense, etc.

Hence appropriate measurements, correctly interpreted, can tell you more
than you assume. :-)

[snip]


Afraid I don't know any figures for the valve amp you mentioned.
However if you look in reviews, values when quoted are often of the
order of 0.5 Ohms or more. i.e. somewhat larger than the value for
your Cyrus,

I don't know what effect a higher o/p impedance would likely have.

Depends on the speakers. However it can produce a change in the frequency
response via interaction with the speaker impedance.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

"Jim Lesurf" wrote in message
...
In article , Peter Scott

OK Wrong word. I meant the fact that you might not get as great an
increase in perceived power as you might expect.

OK. No, the ability to delay is unlikely to affect this very much - unless
the delays were so great as to disrupt the music.

Is phase (delay) not an issue in whether one speaker cancels or reinforces
another? As I understand it two speakers next to each other and in
phase should produce 3dB gain.

Peter Scott

Behringer active crossover
 

In article , Peter Scott
wrote:

"Jim Lesurf" wrote in message
...
In article , Peter Scott

OK Wrong word. I meant the fact that you might not get as great an
increase in perceived power as you might expect.

OK. No, the ability to delay is unlikely to affect this very much -
unless the delays were so great as to disrupt the music.

Is phase (delay) not an issue in whether one speaker cancels or
reinforces another? As I understand it two speakers next to each other
and in phase should produce 3dB gain.

Alas, its not quite that simple. :-) [This response is a favourite one
for academics. ;- ]

The first point is to clarify what is meant by the phrase "next to each
other". I take this to mean "effectively equidistant from the listening
position".

Real speakers have a finite non-zero size, so the above also implies that
we can specify the point or plane from which their output seems to come
when heard from such a location.

In practice, as soon as we move to other locations the phase/time
relationship will change. Thus the result varies around the room. At high
frequencies quite small changes in location w.r.t. the speakers can affect
this. This arises due in part to the change in location altering the
relative lengths as you'd expect. However a less well-known effect is that
the nominal location of the effective source may also change. Real speakers
are unlikely to be point or plane sources in their actual radiation
behaviour and directional properties.

The results in practice will also probably be significantly affected by
reflected/reverberant sounds reaching the listening location via wall
reflections, etc.

If we ignore all the above complications and assume two speakers, each
radiating *in phase* at the same level then the result at a listening
location equidistant from both is a *6dB* rise. Not 3dB.

This is because we have to add the 'vectors' or pressure levels and the
sound power rises in free space as the square of this. Bit like double the
voltage implying four times the power.

However *averaged around the room* the level may rise by around 3dB. In
some places the rise will be more than 3dB, in others less than 3dB.
Indeed, there may well be places where the level *falls* when two speakers
are used as in some places the phase relationship may produce a partial (or
even near-total in principle!) cancellation!

This is due to the variations in phase relationship with listening
location. Can't be more specific without a lot of case-specific details.

When using a pair of speakers with a cross-over the results are much more
complex as the phase relationships vary with frequency, both due to the
crossover actions, and due to the inherent properties of the two speakers.
The result may well phase 'lead' the output from one speaker and 'lag' the
other so that the actual sum is much the same - at the normal/expected
listening locations - as if just one had been used with a flat response.
Again this depends on the details of the situation.

Hence what we get may be nothing like either 6dB or 3dB. Depends on the
details.

In practice, the speaker designer is probably trying to get a given
response, but has to worry about the user-choice of speaker and listening
locations and room acoustics all being outwith his control, and varying
from one user to another. Thus the designer has to make a 'guess' as to
what will suit enough people to make a speaker a commerical success!

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

"Jim Lesurf" wrote in message
...
In article , Peter Scott
wrote:

Hence what we get may be nothing like either 6dB or 3dB. Depends on the
details.

In practice, the speaker designer is probably trying to get a given
response, but has to worry about the user-choice of speaker and listening
locations and room acoustics all being outwith his control, and varying
from one user to another. Thus the designer has to make a 'guess' as to
what will suit enough people to make a speaker a commerical success!

Thanks for clarifying that. The more you think about it the more of a
compromise loudspeaker design is. Bit like designing a vehicle that might
run
on a road or perhaps on fields or up mountains, or maybe on water or.....
This must also be true for high-end speakers unless the designer exactly
specifies the room, speaker positions and surfaces. Going back to another
discussion perhaps there ought be a test criterion along the lines of
'performs well in a wide range of environments'? This might prove to
be a crucial, if not *the* crucial, factor for speakers.

In my question I was thinking of a simpler matter. According to Behringer
two speakers next to each other, so acting as a single point-source, would
show 3dB gain at low frequencies. I should have specified the frequency.
This region is on my mind because I'm pondering what to do about
the design for a sub-woofer. B says you need four drivers for 6dB.
Clearly this will not be the perceived gain throughout the listening
area but just that near the speakers.

Peter Scott

Behringer active crossover
 

In article , Peter Scott
wrote:

"Jim Lesurf" wrote in message
...

[snip]


Thus the designer has to make a
'guess' as to what will suit enough people to make a speaker a
commerical success!

Thanks for clarifying that. The more you think about it the more of a
compromise loudspeaker design is. Bit like designing a vehicle that
might run on a road or perhaps on fields or up mountains, or maybe on
water or.....

Yes. FWIW When I worked at Armstrong mumble-mumble years ago I used to
get into conversations and work with a speaker designer[1] who developed
the Armstrong 602 speaker. This rapidly convinced me that designing
commercial speakers for domestic use is an absolute nightmare. Designing
amps is child's play in comparison. :-) A lot of the design decisions tend
to be based on experience and judgements of what will be most acceptable to
a given target audience of customers.

[1] Bill Perkiss. Came to Armstrong from Goodmans. Wonder what happened to
him after he left Armstrong?...

This must also be true for high-end speakers unless the designer exactly
specifies the room, speaker positions and surfaces.

The advantage of the 'amateur' is that they generally only have to develop
speakers for their own use, to suit themselves and their listening room.
The disadvantage is that they may lack to experience and knowledge and test
kit of a professional.

Going back to another discussion perhaps there ought be a test criterion
along the lines of 'performs well in a wide range of environments'? This
might prove to be a crucial, if not *the* crucial, factor for speakers.

The problem here is defining the relevant set of conditions and then
testing them all. This brings up once again that magazines and reviewers
generally simply don't have the time, money, skills, etc, to do this on a
routine basis.

In my question I was thinking of a simpler matter. According to
Behringer two speakers next to each other, so acting as a single
point-source, would show 3dB gain at low frequencies. I should have
specified the frequency. This region is on my mind because I'm pondering
what to do about the design for a sub-woofer. B says you need four
drivers for 6dB. Clearly this will not be the perceived gain throughout
the listening area but just that near the speakers.

I am not sure why they say the above. There are some other complications
which I didn't mention, though... :-)

One is that the pressure variations produced by one speaker may 'push on'
the other, thus altering its ability to move.

In general, conventional 'cone in a box' speakers have movements that are
mass-controlled. So the main force limiting their movement when driven is
that required to accellerate their mass. The air load is relatively small,
so they tend not to be affected much by the presence of a second unit.

However the same may not be the case at LF as the main force opposing
movement becomes the springiness of their support, and the air inside and
outside the cabinet.

Hence - for example - if two speakers are sharing the same box, at LF, and
the LF compliance (springiness) is mainly that of the air support, then
they might affect each other quite noticably. Even in different cabinets
they may do this.

The division between 'mass controlled' and 'compliance controlled' tends to
occur at the basic resonance frequency of the speaker system. For LF
systems this is typically well below 100Hz somewhere.

But I am not clear why this would mean the result would be a 3dB increase.
It only obviously implies that it may not be 6dB. I'd expect the results to
depend on the specific details of the situation.

Would need more information to know what B are specifically referring to
and why they say the change is 3dB. Or perhaps someone else can explain why
B say this?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

Jim Lesurf wrote:

The way I see it, the only thing measurements will tell me is whether
sound I like has an even response, or a bumpy one. :-)

It can also provide you with information which can be studied and
used to indicate which further steps might (or might not) lead to
further improvements, perhaps more marked than so far obtained.

It can also provide a basis for you and others to assess if some other
methods might yeald similar results with less fuss or expense, etc.

Hence appropriate measurements, correctly interpreted, can tell you
more than you assume. :-)

Okay. See thread on driver resonances in isobaric pairings. :-)

I'm not averse to measuring, as such. I'm just not terribly sure how to go
about it, and not hugely keen to spend piles of cash on it. For example, I
found a sound level meter in Maplin, but it's 70 quid - and only goes down
to 300Hz.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

Wally wrote:
Jim Lesurf wrote:

The way I see it, the only thing measurements will tell me is
whether sound I like has an even response, or a bumpy one. :-)

It can also provide you with information which can be studied and
used to indicate which further steps might (or might not) lead to
further improvements, perhaps more marked than so far obtained.

It can also provide a basis for you and others to assess if some
other methods might yeald similar results with less fuss or
expense,
etc.

Hence appropriate measurements, correctly interpreted, can tell you
more than you assume. :-)

Okay. See thread on driver resonances in isobaric pairings. :-)

I'm not averse to measuring, as such. I'm just not terribly sure how
to go about it, and not hugely keen to spend piles of cash on it.
For
example, I found a sound level meter in Maplin, but it's 70 quid -
and only goes down to 300Hz.

I saw that, and find it surprising as well.

We seem to have mo-better alternatives in low-cost SPL meters in the
states.

Example:

http://www.technika.com/navpage/a10

Here's a survey of UK products:

http://www.noisenet.org/Noise_Instrumentation.htm

Here's almost exactly what I use, UK sourced:

http://www.cornwallelectronics.co.uk...7b6e4a07222d7e

Behringer active crossover
 

"Wally" wrote in message
k...
Jim Lesurf wrote:

The way I see it, the only thing measurements will tell me is whether
sound I like has an even response, or a bumpy one. :-)

It can also provide you with information which can be studied and
used to indicate which further steps might (or might not) lead to
further improvements, perhaps more marked than so far obtained.

It can also provide a basis for you and others to assess if some other
methods might yeald similar results with less fuss or expense, etc.

Hence appropriate measurements, correctly interpreted, can tell you
more than you assume. :-)

Okay. See thread on driver resonances in isobaric pairings. :-)

I'm not averse to measuring, as such. I'm just not terribly sure how to go
about it, and not hugely keen to spend piles of cash on it. For example, I
found a sound level meter in Maplin, but it's 70 quid - and only goes down
to 300Hz.

CPC does some that have a bigger range and at a good price.

http://cpc.farnell.com

Peter Scott

Behringer active crossover
 

"Jim Lesurf" wrote

If we ignore all the above complications and assume two speakers, each
radiating *in phase* at the same level then the result at a listening
location equidistant from both is a *6dB* rise. Not 3dB.

I thought that was only if they were reproducing the same signal.

"In phase" may imply that - how can they be in phase if they are reproducing
different signals - but I think some people take "in phase" to simply mean
wired correctly.

Tim

Behringer active crossover
 

A couple of things regarding crossovers...

1. Manufacturers and customers often confuse polarity and phase.
Phase is frequency dependent; polarity can be changed with a switch or
leads reversal.

2. The best way to set up your triamplified system with electronic
crossover would be to beg or borrow two items:

An electronic test setup, whether it be MLSSA, TEF, Smaart, et al.
This will allow you to watch the adjustment of your parameters in near
real time, visually see the true capabilities and limitations of the
enclosure/loudspeaker system and adjust your crossover accordingly.

Prior to testing, procure one of the Thiele Small loudspeaker enclosure
design packages that include the speaker parameters of the components
you own. This will quickly get you in "the right ballpark".

Good luck.

Behringer active crossover
 

wrote in message
ups.com...
A couple of things regarding crossovers...

1. Manufacturers and customers often confuse polarity and phase.
Phase is frequency dependent; polarity can be changed with a switch or
leads reversal.

2. The best way to set up your triamplified system with electronic
crossover would be to beg or borrow two items:

An electronic test setup, whether it be MLSSA, TEF, Smaart, et al.
This will allow you to watch the adjustment of your parameters in near
real time, visually see the true capabilities and limitations of the
enclosure/loudspeaker system and adjust your crossover accordingly.

Prior to testing, procure one of the Thiele Small loudspeaker enclosure
design packages that include the speaker parameters of the components
you own. This will quickly get you in "the right ballpark".

Good luck.

Very useful advice. Thanks. My experience so far with
tri-amping is all good. I now have a system that is a lot
closer to what I want. Its just that the lights dim when I
switch it on! This is with using a car sub and some not
particularly high-spec tweeters. It is strange to hear the
effect of increasing, for example, the high treble. The
whole band moves up rather than an increase in slope
as you used to get with simple tone controls.

Now I've got to do the difficult bit and decide on the sub.

Peter Scott

Behringer active crossover
 

In article , Tim Martin
wrote:

"Jim Lesurf" wrote

If we ignore all the above complications and assume two speakers, each
radiating *in phase* at the same level then the result at a listening
location equidistant from both is a *6dB* rise. Not 3dB.

I thought that was only if they were reproducing the same signal.

The context of the discussion from which the above quote is snipped was
that the two speakers were being driven from the same source (signal)
albiet with a crossover that may affect the amplitude/phase relationship.
The "ignore all the above" indicated that the crossover, etc, didn't change
the phase relationship so the two units were being driven with the same
signal in time alignment.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Behringer active crossover
 

wrote in message
ups.com...
A couple of things regarding crossovers...

1. Manufacturers and customers often confuse polarity and phase.
Phase is frequency dependent; polarity can be changed with a switch or
leads reversal.

2. The best way to set up your triamplified system with electronic
crossover would be to beg or borrow two items:

An electronic test setup, whether it be MLSSA, TEF, Smaart, et al.
This will allow you to watch the adjustment of your parameters in near
real time, visually see the true capabilities and limitations of the
enclosure/loudspeaker system and adjust your crossover accordingly.

Prior to testing, procure one of the Thiele Small loudspeaker enclosure
design packages that include the speaker parameters of the components
you own. This will quickly get you in "the right ballpark".

Good luck.

Please excuse if this is a repeat. I cannot see the message I
posted but everyone else could. This has happened before.

Very useful advice. Thanks. My experience so far with
tri-amping is all good. I now have a system that is a lot
closer to what I want. Its just that the lights dim when I
switch it on! This is with using a car sub and some not
particularly high-spec tweeters. It is strange to hear the
effect of increasing, for example, the high treble. The
whole band moves up rather than an increase in slope
as you used to get with simple tone controls.

Now I've got to do the difficult bit and decide on the sub.

Peter Scott

Behringer active crossover
 

In polarity with a DC signal with the speaker occupying the same space,
the 6 dB differential is absolutely correct. With a complex phase
signal, which many commerically available loudspeakers being
non-coherent at best and which differ slightly between even sequential
serial numbers, the issue thus becomes significantly more complex.

This can be demonstrated with two stacked identical loudspeakers fed
identical, but with a relative polarity reversed, signal. This was one
of Don Davis's favorite tricks in his Syn-Aud-Con training sessions.

One of the easiest ways a non-technical person can evaluate a speaker
for obvious phase anomalies is to playback a full bandwidth swept
sinewave at a relatively low level. These are available on dozens of
commercial test CDs. If you hear "birdies", you have a phase problem
at that particular reproduction frequency. A birdie is immediately
obvious, sounding something akin to a Looney Tunes cartoon sound
effect. BEE-OOO-WOOP.

To the best of my experience (I've tested many), only some of the
planar electrostatic and plasma speakers have truly decent full
bandwidth phase responses over the majority of their bandwidth while
not exhibiting compensatory frequency anomalies. A few (a handful)
dynamic speakers from truly capable designers are also on the market.

This is where digital filtering (once it is fully understood) will
eventually take over the commercial signal processing market- the
theory being eventually we will be able to alter frequency without
requisite phase anomalies as happens in the analog world.

To listen to a high quality reproduction system with excellent phase
response is a truly great experience. It does transport you to a
different world, not unlike viewing a real painting masterpiece. A
picture in the book can only bring back memories of the original at
best.

That being said, the major thrust in the commercial market today is not
reproduction (including phase) accuracy- note how many commentators
marvel at higher bandwidth iPod iterations while exclaiming the virtues
of its near perfect performance. One wonders just how many Stax
headphones are actually connected to iPods in this world.

I'm sure we'll have to wait this trend out. Ten years ago 44.1 kHz
sampling on a CD was not good enough and we eventually ended up with
competing DVD Audio and SACD audio products. How an iPod sampling
(generally sourced a 44.1 CD and then heavily compressed) at 128kbps or
even 320k reaches perfection pushes the world of the illogic back to
flogiston theory. Mind you the DVD Audio bit rate is 9.6 MEGAbits per
second.

One of these days I hope I'll read a review of an iPod's technical
performance using high end test equipment. It would be great to see
bandwidth, polarity, phase, THD+Noise, S/N ratio, etc.

Yet I digress...

Behringer active crossover
 

Arny Krueger wrote:

We seem to have mo-better alternatives in low-cost SPL meters in the
states.
...
Here's almost exactly what I use, UK sourced:

http://www.cornwallelectronics.co.uk/? ...

Thanks for the links, Arny. Just found a local supplier of the digital
version of this one (the peak hold feature looks useful), so I'll be off out
soon to get it.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Behringer active crossover
 

Peter Scott wrote:

CPC does some that have a bigger range and at a good price.

http://cpc.farnell.com

See reply to Arny - the Tandy/RadioShack ones seems to get a lot of good
opinion for measuring SPL on a budget, so I'll be getting one of the 40 quid
digital display jobbies.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk