Centre, speaker - twin drivers, use one enclosure or two separateenclosures side by side?
 

On 12/11/2014 10:12 PM, Peter Chant wrote:
Cheap adjustable hole saw has arrived. It it works it will pay for
itself in saved hassle in one use. However, if baffle is a min of a
foot wide one wavelength between front and back will be at over 400Hz,
so roll off will be quite high. I wonder if I can put the speakers in a
scrap piece and temporarily fix a larger sheet so I don't have to drill
my nice unsullied sheet of ply!


Speakers installed on an off-cut of kitchen worktop as an open baffle.
Surprised how well that works - could even here the low bits in 'LFO'!
I have a feeling a some sort of enclosure will make it more space friendly.

Centre, speaker - twin drivers, use one enclosure or two separateenclosures side by side?
 

On 12/10/2014 06:15 AM, Woody wrote:
Just as a thought, have you considered trying one or both
speakers (series or parallel) on an open baffle to see what
they sound like? If you are not wanting bass then a piece of
wood maybe a foot or so square might be a starting point?

I once tried it with a drawer from an old dresser which had
a thicker than might be expected floor panel. Worked
surprisingly well.


Have done that. Two bass / mids mounted with tweeter on a piece of
kitchen counter top. Mid-woofers in series but with 2x6.8uF cap across
one. Somehow it sounds a bit 'boxy'. Mid range seems accentuated. I'll
have to wire the drivers in parallel and see what happens. I wonder if
this is an effect of the baffle arrangement or a fundamental limitation
of the drivers.

Centre, speaker - twin drivers, use one enclosure or two separateenclosures side by side?
 

Peter Chant wrote:


Have done that. Two bass / mids mounted with tweeter on a piece of
kitchen counter top. Mid-woofers in series but with 2x6.8uF cap across
one.

** Wow, so he took my suggestion seriously after all.


Somehow it sounds a bit 'boxy'.


** LOL - an open plain baffle can sound a bit "woody" if it is made from ply or pine.

Mid range seems accentuated.

** Gee - a lack of low bass will do that ...

I'll
have to wire the drivers in parallel and see what happens.

** It will be 6dB louder and have even more midrange.

I wonder if
this is an effect of the baffle arrangement or a fundamental limitation
of the drivers.


** Trying to balance and passively equalise a home brew *two way* speaker by ear alone is a near impossible task - I know cos I have tried many times.

Since you cannot adjust the mid frequency level independently, you have to be damn lucky with your choice of drivers. However, with a three way design, options for tweaking the response really open up.

A couple of years back, I picked up a pair of old AR2axs for A$100. These are a three way design with a really primitive x-over and cheaply made drivers that had deteriorated to the point of useless. The money got me two, nice looking cabinets of about 45 litres volume.

I stripped them both out and started again with three Peerless drivers chosen to have similar dB/watts and in sizes to fit the existing baffle cut outs. The chosen woofer's response was modelled in the same volume box using WinISD and it was near perfect.

So, I purchased a 10 inch woofer, 4 inch midrange and 1 inch soft dome with a big mounting plate. The new mid got its own 2 litre enclosure, made from a thick cardboard port tube running back to front- which also helped to stiffen the front baffle. The original AR mids were "sealed back" types, just like old fashioned paper cone tweeters - yuck.

Much effort and time was spent on the passive x-over which was externally connected to the box until I felt no further improvement was possible. Testing was done first with sine waves and then 1/3 octave pink noise using a Rode calibrated SPL meter. Further testing was done with an AKG CK2 condenser mic and 4 cycle sine wave bursts observed on a scope - a very informative technique for revealing colouration and one which works well inside a room.

X-over frequencies ended up at 450Hz and 2.2kHz with 3dB of attenuation for mid and tweeter. I bought a 4 ohm tweeter to make sure it would have enough level to match the woofer cos you sure as heck do not what to have to attenuate that.

The tweeter's HP filter is 18dB/octave while the others are all 12dB/octave.. The x-over uses three air cored inductors and five 250VAC rated poly caps plus a couple of big bi-polars for the woofer. The mid enclosure was stuffed tight with damping material and sine wave burst testing showed there were virtually no internal echoes emerging.

The new speakers are use mainly for watching DTV and DVD movies - so had to sound natural on speech and they do.

FYI: My previous speakers were Quad ESL57s which I had used for over 20 years - they needed major restoration work done by an expert, so I sold them to a guy who was willing to finance getting that done.


..... Phil

Centre, speaker - twin drivers, use one enclosure or two separate enclosures side by side?
 

Just for info I've been having a play with a Behringer Ultracurve Pro
DEQ2496.

Basically a dual channel equaliser. It has a built in pink noise generator
and mic input, and using those will auto eq a speaker system. Quite
remarkable given the low price.

--
*My wife has a slight impediment in her speech. She stops to breathe.

Dave Plowman London SW
To e-mail, change noise into sound.

Centre, speaker - twin drivers, use one enclosure or two separate enclosures side by side?
 

In article ,
Bob Latham wrote:
Basically a dual channel equaliser. It has a built in pink noise
generator and mic input, and using those will auto eq a speaker system.
Quite remarkable given the low price.

I've often thought about this kind of digital processing and my
understanding of what happens is obviously a bit limited as digital
processing AFTER the volume control looks a bit dodgy to me. I'm not
saying I'm right, I don't know but it worries me because....

Ideally, for best noise etc results, you'd use it before the volume
control. Of course, not all pre-amps have this facility.

--
*Indian Driver - Smoke signals only*

Dave Plowman London SW
To e-mail, change noise into sound.

Centre, speaker - twin drivers, use one enclosure or two separate enclosures side by side?
 

In article , Bob Latham
wrote:
In article , Dave Plowman (News)
wrote:
Just for info I've been having a play with a Behringer Ultracurve Pro
DEQ2496.

Basically a dual channel equaliser. It has a built in pink noise
generator and mic input, and using those will auto eq a speaker
system. Quite remarkable given the low price.

I've often thought about this kind of digital processing and my
understanding of what happens is obviously a bit limited as digital
processing AFTER the volume control looks a bit dodgy to me. I'm not
saying I'm right, I don't know but it worries me because....

Assuming you set the sensitivity of the DAC input such that the dac
*just* does not clip when your playing the loudest recording you have at
the loudest you'll ever play it, what happens to the quality of
quantisation when you play a quietly recorded piece with volume turned
down?

Have to give the usual engineering answer "It depends..." :-)

e.g. The 851C I use employs a 'digital' volume and balance control. However
it converts all inputs to 384k / 24bit. So for most of the digital source
material most people will have, a 'good' system of this kind would allow
the output quantisation noise level to remain defined by the source
material for a modest amount of level scaling downward.

I expect some more modern systems will duly use a mix of higher internal
rates and either more bits per sample or heavily noise-shaped 'DSD' sic.
But the argument comes out much the same from a theoretical POV.

But of course in *reality* if you wind down the level more and more, then
eventually the signal/noise will start to suffer. Just a question of when
that starts to happen.

Bear in mind, though, that the chances are that even 24bit audio files you
may obtain will be likely to have a background noise or quantisation level
that is rather higher than implied by 24 bit range. And such a range is
likely to be well beyond what you'd experience in most normal homes.

The real problems with digital 'EQ' for room and speaker are more
complicated. It depends on the details of what you need to 'correct'. The
most obvious example being a room or speaker response that has a narrow and
deep dip somewhere. That implies needing to boost any signals at the
frequency quite a lot. Which may then clip the DAC... or clip the following
amps, etc. Consider the implications of a 20dB 'dip' for example. You'd
have to wind down the general volume by 20dB to avoid the clipping problems
which could be caused by boosting some components by 20dB before the room
and speaker which had a corresponding 20dB drop.

And some room/speaker problems are almost unfixable by such means as
"measure the frequency response, then 'invert it' to get a flat result".

So its reasonable to expect such an EQ to give you some improvements. How
much, and at what point you encounter problems, depends entirely on the
details of the case.

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

Centre, speaker - twin drivers, use one enclosure or two separateenclosures side by side?
 

Jim Lesurf wrote:


The real problems with digital 'EQ' for room and speaker are more
complicated. It depends on the details of what you need to 'correct'. The
most obvious example being a room or speaker response that has a narrow and
deep dip somewhere.

And some room/speaker problems are almost unfixable by such means as
"measure the frequency response, then 'invert it' to get a flat result".


** Best thing you can do is to EQ the speakers themselves outdoors in the back garden. Suggest you put the pair side by side and the test mic in the central position, about 2 metres away.

( If you have Quad ESL63s or the like, just forget it, you cannot improve perfection)

Nothing an EQ can do will fix a poor listen room but human ears do learn to listen through some of the defects in a room given time - but a reverberant room is a dead loss from the outset. Means a typical room with bare walls & ceilings,large glass windows etc. Polished wood floors are an abomination, sound wise.


FYI:

Best listening room I or anyone I know ever experienced belonged to a friend of mine living nearby in Sydney. Prompted by suggestions from myself and some telephone advice from an acoustics expert - his 5m x 10m x 3m lounge room was as follows.

1. Timber floor over joists, covered in shag pile carpet and underlay = dead to low, mid and high frequencies.

2. Double brick cavity walls covered in short pile carpet from floor to ceiling on 3 sides, bookshelves full of books on the fourth = dead to mid and high frequencies.

3. Large timber frame covered in carpet and underlay strung 0.3m under the plaster on joist ceiling covering about 50% of the area - hung above the listening position.

4. Heavy curtains covering the two small windows.

5. Listening position was 4 metres away from the rear wall and speakers about 3 metres in front of that.

6. House in a quiet cul-de-sac with tolerant neighbours.

Result was nearly anechoic, anyone who spoke facing away from the listener was hard to hear. Hand claps made *no* audible echo.

The room had stacked Quad ESL57s and a twin KEF B139 sub - parked against the rear wall.

Good recording sounded *spectacular*, with a clarity and the full original ambience you only usually get to hear with electrostatic headphones.

In that room, I was able to also audition Yamaha NS1000s and Magnaplaners, not at the same time though.

The Yamahas sounded remarkably similar to one pair of ESL57s but could not beat two pairs when played loud. The Quad's sound was then very noticeably cleaner.

The Magnaplanars sounded just awful, poor sales dude who brought them over for a demo that evening was reluctant to bring them inside after few minutes spent listening to the stacked Quads.

My friend spent about the same money improving his room as he had on one pair of Quad ESL57s - about $1000 in 1979. His only new purchase after what was a Sony CD player in 1983 - after he had a good listening session with my CDP101 of course.

The idiotic notion that the CD format was a lemon was rife in those days.


.... Phil

Centre, speaker - twin drivers, use one enclosure or two separate enclosures side by side?
 

Phil Allison wrote:
Jim Lesurf wrote:


The real problems with digital 'EQ' for room and speaker are more
complicated. It depends on the details of what you need to 'correct'. The
most obvious example being a room or speaker response that has a narrow and
deep dip somewhere.

And some room/speaker problems are almost unfixable by such means as
"measure the frequency response, then 'invert it' to get a flat result".



When the DiAppolito MTM configuration was first thought up, the odd or even
order crossover was selected to provide maximum range of dispersion. His
was vertically mounted. Then decided it was better to narrow dispersion by
changing order of crossover, to minimize ceiling floor bounces. I always
went for maximum dispersion, especially in horizontal mounting. I like to
move around a bit. The drivers natural phase change must be entered in the
crossover order, at selected crossover frequency.

Greg

** Best thing you can do is to EQ the speakers themselves outdoors in the
back garden. Suggest you put the pair side by side and the test mic in
the central position, about 2 metres away.

( If you have Quad ESL63s or the like, just forget it, you cannot improve perfection)

Nothing an EQ can do will fix a poor listen room but human ears do learn
to listen through some of the defects in a room given time - but a
reverberant room is a dead loss from the outset. Means a typical room
with bare walls & ceilings,large glass windows etc. Polished wood floors
are an abomination, sound wise.


FYI:

Best listening room I or anyone I know ever experienced belonged to a
friend of mine living nearby in Sydney. Prompted by suggestions from
myself and some telephone advice from an acoustics expert - his 5m x 10m
x 3m lounge room was as follows.

1. Timber floor over joists, covered in shag pile carpet and underlay =
dead to low, mid and high frequencies.

2. Double brick cavity walls covered in short pile carpet from floor to
ceiling on 3 sides, bookshelves full of books on the fourth = dead to mid
and high frequencies.

3. Large timber frame covered in carpet and underlay strung 0.3m under
the plaster on joist ceiling covering about 50% of the area - hung above
the listening position.

4. Heavy curtains covering the two small windows.

5. Listening position was 4 metres away from the rear wall and speakers
about 3 metres in front of that.

6. House in a quiet cul-de-sac with tolerant neighbours.

Result was nearly anechoic, anyone who spoke facing away from the
listener was hard to hear. Hand claps made *no* audible echo.

The room had stacked Quad ESL57s and a twin KEF B139 sub - parked against the rear wall.

Good recording sounded *spectacular*, with a clarity and the full
original ambience you only usually get to hear with electrostatic headphones.

In that room, I was able to also audition Yamaha NS1000s and
Magnaplaners, not at the same time though.

The Yamahas sounded remarkably similar to one pair of ESL57s but could
not beat two pairs when played loud. The Quad's sound was then very noticeably cleaner.

The Magnaplanars sounded just awful, poor sales dude who brought them
over for a demo that evening was reluctant to bring them inside after few
minutes spent listening to the stacked Quads.

My friend spent about the same money improving his room as he had on one
pair of Quad ESL57s - about $1000 in 1979. His only new purchase after
what was a Sony CD player in 1983 - after he had a good listening session
with my CDP101 of course.

The idiotic notion that the CD format was a lemon was rife in those days.


... Phil

Centre, speaker - twin drivers, use one enclosure or two separate enclosures side by side?
 

In article ,
Phil Allison wrote:
Nothing an EQ can do will fix a poor listen room but human ears do learn
to listen through some of the defects in a room given time - but a
reverberant room is a dead loss from the outset. Means a typical room
with bare walls & ceilings,large glass windows etc. Polished wood floors
are an abomination, sound wise.

Crikey. I actually agree 100% with you. Must be Xmas. ;-)

--
*Born free - taxed to death *

Dave Plowman London SW
To e-mail, change noise into sound.