Some time back I posted in here regarding lack of a sweet spot when using a
pair of IPL transmission line speakers. I never did resolve the problem and
just lived with it...until now. I've just bought a pair of Behringer B2301
near field reference monitors and the difference is astounding. I'm hearing
high resolution and detailed images both spatially and acoustically with
these speakers. Which makes me wonder...IPL speakers are quite high spec and
I would not have expected so much difference, especially with my ancient
ears. I haven't done any proper A/B tests. The speakers are not even in the
same room, for example. But there must surely be a problem with the IPL
units.

IPL speakers come in kit form...is it possible that I have gotten incorrect
phasing to one or more drivers? The bass drivers are correct...is there an
easy way to check the others without disassembling them (a chore)? Any other
ideas/suggestions?

In article , TonyL
wrote:
Some time back I posted in here regarding lack of a sweet spot when
using a pair of IPL transmission line speakers. I never did resolve the
problem and just lived with it...until now. I've just bought a pair of
Behringer B2301 near field reference monitors and the difference is
astounding. I'm hearing high resolution and detailed images both
spatially and acoustically with these speakers. Which makes me
wonder...IPL speakers are quite high spec and I would not have expected
so much difference, especially with my ancient ears. I haven't done any
proper A/B tests. The speakers are not even in the same room, for
example. But there must surely be a problem with the IPL units.

IPL speakers come in kit form...is it possible that I have gotten
incorrect phasing to one or more drivers? The bass drivers are
correct...is there an easy way to check the others without
disassembling them (a chore)? Any other ideas/suggestions?

Problems with imaging may have nothing to do with the nominal frequency
response of the speakers. May be due to other factors like their radiation
pattern, colouration due to other parts vibrating, how this all interacts
with your room's acoustic, etc, etc.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 22/03/2012 17:31, TonyL wrote:
Some time back I posted in here regarding lack of a sweet spot when using a
pair of IPL transmission line speakers. I never did resolve the problem and
just lived with it...until now. I've just bought a pair of Behringer B2301
near field reference monitors and the difference is astounding. I'm hearing
high resolution and detailed images both spatially and acoustically with
these speakers. Which makes me wonder...IPL speakers are quite high spec and
I would not have expected so much difference, especially with my ancient
ears. I haven't done any proper A/B tests. The speakers are not even in the
same room, for example. But there must surely be a problem with the IPL
units.

IPL speakers come in kit form...is it possible that I have gotten incorrect
phasing to one or more drivers? The bass drivers are correct...is there an
easy way to check the others without disassembling them (a chore)? Any other
ideas/suggestions?

You're supposed to be able to tell by placing the speakers face to face,
swapping the connections to one, and playing a mono source.
So one driver pushes while the other pulls, and there is little output.
If one midrange is inverted, there will be lots of output.
I never tried it myself. It might not work for HF where the wavelength
is short.

--
Eiron.

Eiron wrote:

You're supposed to be able to tell by placing the speakers face to
face, swapping the connections to one, and playing a mono source.
So one driver pushes while the other pulls, and there is little
output. If one midrange is inverted, there will be lots of output.
I never tried it myself. It might not work for HF where the wavelength
is short.


Yes, that is exactly how I determined that the bass drivers were correctly
phased. But I agree that this might not work well with the midrange and hf
drivers.

Jim Lesurf wrote:

Problems with imaging may have nothing to do with the nominal
frequency response of the speakers. May be due to other factors like
their radiation pattern, colouration due to other parts vibrating,
how this all interacts with your room's acoustic, etc, etc.


Thanks Jim,

I did do some experimenting with positioning and room acoustics with no real
improvement. As individual speakers the IPL units sound fine...just no
proper imaging as a pair. Somebody emailed me suggesting that the ribbon
tweeters used could be the problem....does this make sense? Could they have
a narrow or uneven radiation pattern?

If an MF or HF driver were wired incorrectly could this explain the lack of
image?

My fully assembled Behringer monitors cost less than half of the IPL driver
kits (enclosures not included) and yet sound so much better...must be a
reason...

On 23/03/2012 10:00, TonyL wrote:
Jim Lesurf wrote:

Problems with imaging may have nothing to do with the nominal
frequency response of the speakers. May be due to other factors like
their radiation pattern, colouration due to other parts vibrating,
how this all interacts with your room's acoustic, etc, etc.


Thanks Jim,

I did do some experimenting with positioning and room acoustics with no real
improvement. As individual speakers the IPL units sound fine...just no
proper imaging as a pair. Somebody emailed me suggesting that the ribbon
tweeters used could be the problem....does this make sense? Could they have
a narrow or uneven radiation pattern?

If an MF or HF driver were wired incorrectly could this explain the lack of
image?

My fully assembled Behringer monitors cost less than half of the IPL driver
kits (enclosures not included) and yet sound so much better...must be a
reason...


I had some Dynaudio floor standers and bookshelf speakers - model 40 and
70 I think. Used the same drivers (maybe the bass on the 70 was an inch
bigger). The small speakers sounded *much* better in terms of imaging
and especially bass. I think the extended bass of the larger speakers
served to muddy the dispersion of the sound (or some such!).

In my case I think the room size (about 15' x 12') conspired against the
larger speaker too.

Rob

In article , TonyL
wrote:
Jim Lesurf wrote:

Problems with imaging may have nothing to do with the nominal
frequency response of the speakers. May be due to other factors like
their radiation pattern, colouration due to other parts vibrating, how
this all interacts with your room's acoustic, etc, etc.


Thanks Jim,

I did do some experimenting with positioning and room acoustics with no
real improvement. As individual speakers the IPL units sound
fine...just no proper imaging as a pair. Somebody emailed me suggesting
that the ribbon tweeters used could be the problem....does this make
sense? Could they have a narrow or uneven radiation pattern?

I can't comment on the specific speakers, and the difficulty is that the
cause could be one or more factors from a long list! However speakers whose
radiation pattern varies a lot with frequency may well give a poorer image
than ones with patterns that are similar over a wide frequency range.

This also depends a lot on the room acoustic, etc. Fairly obviously, if you
lived in an anechoic chamber the radiation patterns of the speakers would
become irrelevant. :-)

Above all said, our ears may be particularly sensitive to the band in the
few kHz region as that is where our ear lobes, etc, produce direction
dependent effects we then use as one 'imaging' cue. So if the two speakers
had noticable different behaviours in that sort of region, it would be a
candidate for upsetting the imaging. This may not be the speaker units.
Might be a panel or part of one speaker resonating whilst the other speaker
is OK.

If an MF or HF driver were wired incorrectly could this explain the lack
of image?

Possibly if it causes marked peaks or dips in the few kHz range. That can
also affect timing of what reaches you. I can't be sure though. In my
experience poor imaging tends to come from room problems or the speakers
having poor patterns.

My fully assembled Behringer monitors cost less than half of the IPL
driver kits (enclosures not included) and yet sound so much
better...must be a reason...

This may also be a reason why not everyone loved the IPL designs. I never
heard them for long enough to really say, though.

FWIW personally, I tend to find a lot of low bass also affects imaging. But
that may be a personal sensitivity. The point here is that LF will shake
the HF sensors in your ears, and the sensors are non-linear. So perception
is quite complex. { Massive understatement warning! :-) }

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

The way I checked the polarity of mine was to half-wave rectify a sine wave
and using that as a signal source, play it and then, using a microphone,
check on a 'scope which way up was the flat bit. It took a certain amount of
messing about with the EQ on the microphone mixer to get a clear image, but
it worked fine in the end.

S.

"TonyL" wrote in message
...
Eiron wrote:

You're supposed to be able to tell by placing the speakers face to
face, swapping the connections to one, and playing a mono source.
So one driver pushes while the other pulls, and there is little
output. If one midrange is inverted, there will be lots of output.
I never tried it myself. It might not work for HF where the wavelength
is short.


Yes, that is exactly how I determined that the bass drivers were correctly
phased. But I agree that this might not work well with the midrange and hf
drivers.

Hey Serge, sounds good. Any asymmetrical signal source would do, I guess.
Thanks.

Serge Auckland wrote:
The way I checked the polarity of mine was to half-wave rectify a
sine wave and using that as a signal source, play it and then, using
a microphone, check on a 'scope which way up was the flat bit. It
took a certain amount of messing about with the EQ on the microphone
mixer to get a clear image, but it worked fine in the end.

I can't comment on the specific speakers, and the difficulty is that
the cause could be one or more factors from a long list! However
speakers whose radiation pattern varies a lot with frequency may well
give a poorer image than ones with patterns that are similar over a
wide frequency range.


Understood.

This also depends a lot on the room acoustic, etc. Fairly obviously,
if you lived in an anechoic chamber the radiation patterns of the
speakers would become irrelevant. :-)

Above all said, our ears may be particularly sensitive to the band in
the few kHz region as that is where our ear lobes, etc, produce
direction dependent effects we then use as one 'imaging' cue. So if
the two speakers had noticable different behaviours in that sort of
region, it would be a candidate for upsetting the imaging. This may
not be the speaker units. Might be a panel or part of one speaker
resonating whilst the other speaker is OK.


Yes. Interestingly, my wife has better hearing than me...frequency-wise. But
she is very poor at locating the direction of sound sources. I am pretty
good at that.


This may also be a reason why not everyone loved the IPL designs. I
never heard them for long enough to really say, though.


What I like about them is the clean bass. Unlike many ported designs, the
bass is not overly obtrusive..to the extend that some have commented that is
is somewhat lacking. But it certainly is there given an appropriate source.

FWIW personally, I tend to find a lot of low bass also affects
imaging. But that may be a personal sensitivity. The point here is
that LF will shake the HF sensors in your ears, and the sensors are
non-linear. So perception is quite complex. { Massive understatement
warning! :-) }


Thanks, I think I know where to start looking now....when I get around to
it. My main interest right now is my new Behringer monitors :-)