I have used the panels on the back wall of a couple of pair of Fostex FE167E based bookshelf reflex. And was happy with them by themselves and they seemed to keep the detail while getting rid of the harshness problems of an empty box. But when I lined the rest of the walls with normal stuffing they sounded muted and not very detailed.
The deflex panels and some very light intermittent stuffing here and there on the walls was pretty much the best initially. Any additional stuffing mutted the detail.
But on the last pair though I put deflex panels on the back and Wispermat on the sides. This was by far the best. Seems odd since this seems counter to the experience in the same speaker design when I adding "stuffing" lining to the walls.
I have continued to use Whispermat for the next couple of pairs of speakers I built (without the deflex panels andd have been very happy with the results.
Wispermat is a foam+dampening mat similar to the Blackhole concept (but much cheaper). It is a commercial product for sound reduction. One has to buy at least a large sheet per order . I have used the sheet on three pairs of bookshelf speakers and still have some left. I'll bring some to the NWWA DIY if any one wants to check it out.
Here is what got me interested in Whispermat.
http://home.new.rr.com/zaph/audio/whispermat.html
The deflex panels and some very light intermittent stuffing here and there on the walls was pretty much the best initially. Any additional stuffing mutted the detail.
But on the last pair though I put deflex panels on the back and Wispermat on the sides. This was by far the best. Seems odd since this seems counter to the experience in the same speaker design when I adding "stuffing" lining to the walls.
I have continued to use Whispermat for the next couple of pairs of speakers I built (without the deflex panels andd have been very happy with the results.
Wispermat is a foam+dampening mat similar to the Blackhole concept (but much cheaper). It is a commercial product for sound reduction. One has to buy at least a large sheet per order . I have used the sheet on three pairs of bookshelf speakers and still have some left. I'll bring some to the NWWA DIY if any one wants to check it out.
Here is what got me interested in Whispermat.
http://home.new.rr.com/zaph/audio/whispermat.html
Electron:
How would you say impact on detail is on all-whispermat versus all-deflex? For me, on this project price is not a very big issue. Not because I'm rich, but because it's small 10 liter monitor speakers using very expensive drivers, thus there is no need to make cost compromises in dampening material..
I am planning on a quite thin enclosure structure though, to keep the monitor size down, using a sandwich of 6mm MDF/1mm viscoelastic glue/1mm lead/1mm viscoelastic glue/1mm lead/1mm viscoelastic glue/6mm MDF (total thickness of 18mm) and would also like my dampening material to consume as little space as possible, still with an absolute minimum of sacrifices.
Dampening material volume taken into consideration, would you say I am looking at the Spectra Deflex panels?
How would you say impact on detail is on all-whispermat versus all-deflex? For me, on this project price is not a very big issue. Not because I'm rich, but because it's small 10 liter monitor speakers using very expensive drivers, thus there is no need to make cost compromises in dampening material..
I am planning on a quite thin enclosure structure though, to keep the monitor size down, using a sandwich of 6mm MDF/1mm viscoelastic glue/1mm lead/1mm viscoelastic glue/1mm lead/1mm viscoelastic glue/6mm MDF (total thickness of 18mm) and would also like my dampening material to consume as little space as possible, still with an absolute minimum of sacrifices.
Dampening material volume taken into consideration, would you say I am looking at the Spectra Deflex panels?
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Rocky said:
I do not really have a direct comparison because I have not done and all deflex version. The all Whispermat version I have done is a different speaker with less detailed drivers so I don't have analytical data. So "unencumbered by the facts, I will speculate".
It seems to me that the Deflex panels and the Whispermat likely has different properties at different frequencies. So a mix is certainly appealing. It would seem that the deflex panel only would be somewhat suspect.
Whispermat only seems to work well. John Krutke uses it in his Seas L15RLYP / 27TFFC System. I believe these are generally regarded as drivers with a lot of detail, and the speaker seems to have gotten good reviews at DIY events.
http://home.new.rr.com/zaph/audio/audio-speaker12.html
Supporting evidence for this approach also is the Blackhole only implementations of some very well regarded designs (example MBOW1).
Whether or not the Whispermat is thicker than the Deflex panel depends on whether or not you are counting the foam layer or not. If you are not counting the foam and just the damping layer then it is thinner than the Deflex panel.
I would worry that an all Deflex panel lining would only get at some frequencies. Again, speculation on my part. If I was not going to try a mix and was chosing one or the other, I would go with all Whispermat because this kind of approach seems reasonably well proven in these kinds of boxes.
By the way here is a note from the building instructions of the MBOW1 that might be pertinent:
"Do not run the BlackHole all the way to the front baffle. Leave at least an inch bare so that it does not interfere with the woofer's backwave."
Forgive me for putting up such a critical point of view, but why would the Whispermat/blackhole reveal any more detail than conventional bitumen stuffing? despite the inner polyurethane layers, their outter foam layer still damp soundwaves in the usual stuffing manner? No?
Making the assumption I would find the whispermat fit for my project (I read the article, so I assume I can compare it to the BlackHole 5), And would follow the advice of leaving 1 1/2 inch space at the front baffle, would this 1 1/2 inch space (+ the front baffle), in your opinion, have a benefit of a non-foam polyurethane layer like the Deflex mat?
Making the assumption I would find the whispermat fit for my project (I read the article, so I assume I can compare it to the BlackHole 5), And would follow the advice of leaving 1 1/2 inch space at the front baffle, would this 1 1/2 inch space (+ the front baffle), in your opinion, have a benefit of a non-foam polyurethane layer like the Deflex mat?
Some uf us regard the deflex panels as basically a con.
Reputable DIY retailers like Falcon Acoustics in the UK refuse to sell it.
Basically because it doesn't do what is says on the tin.
For reflex box's quality acoustic foam lining is best.
(Presuming you regard the lead damping as enough
mechanical damping of the enclosure walls.)
Bulk filling, Polyfill, Dacron etc can be used away from the port
exit to affect box airspace Q and bass damping to an extent.
sreten.
Reputable DIY retailers like Falcon Acoustics in the UK refuse to sell it.
Basically because it doesn't do what is says on the tin.
For reflex box's quality acoustic foam lining is best.
(Presuming you regard the lead damping as enough
mechanical damping of the enclosure walls.)
Bulk filling, Polyfill, Dacron etc can be used away from the port
exit to affect box airspace Q and bass damping to an extent.
sreten.I have used the deflex panels in the past. I covered the entire ineer walls of the midrange cabinet in a three way system. I used it with a Podszus/Gorlich 5"driver in a 5l closed enclosure.
In my experience only deflex wasn't enough, so I used a small amount of sheepwool to stuff the volume. That worked pretty well. The Deflex did some positive things to the sound, it sounds less muffled then a completly stuffed enclosure. If it is worth the high cost, I don't know. For me the improvements where not of such order that I had to use it again in my next speakers.
My experience is that a cabinet with to much stuffing sounds dull and very "hifi" . If you really need so much stuffing that's an indication that something is wrong with the cabinet design in the first place. Remember that about 90% of all the enclosure designs you see at the store are designed on aestetic backgrounds, not on acoustics.
Currently I'm using open baffle speakers, without any damping at all so I haven't tried some of the newer stuff lately.
In my experience only deflex wasn't enough, so I used a small amount of sheepwool to stuff the volume. That worked pretty well. The Deflex did some positive things to the sound, it sounds less muffled then a completly stuffed enclosure. If it is worth the high cost, I don't know. For me the improvements where not of such order that I had to use it again in my next speakers.
My experience is that a cabinet with to much stuffing sounds dull and very "hifi" . If you really need so much stuffing that's an indication that something is wrong with the cabinet design in the first place. Remember that about 90% of all the enclosure designs you see at the store are designed on aestetic backgrounds, not on acoustics.
Currently I'm using open baffle speakers, without any damping at all so I haven't tried some of the newer stuff lately.
In my situation they seemed to have an effect because I had to change the amount of fill lining once I put the Deflex panels on the back wall. The "Fresnel" shape certainly seems like hype but it is hard to believe the material does not dampen resonances of at least certain frequencies, albeit mostly mechanical.
But as reported it apears the the Deflex panel is not enough on it's own to replace the effects of stuffing/foam for their purposes.
My experience could have been:
1) real effect- it required change is fill after adding the Deflex panels
2) Placebo effect (of course they sound at least $11 per speaker better!).
I probably will not incorporate the panels routinely but if I do another pair of the Fostex bass reflex design I would use them so as to not “change the recipe”.
But as reported it apears the the Deflex panel is not enough on it's own to replace the effects of stuffing/foam for their purposes.
My experience could have been:
1) real effect- it required change is fill after adding the Deflex panels
2) Placebo effect (of course they sound at least $11 per speaker better!).
I probably will not incorporate the panels routinely but if I do another pair of the Fostex bass reflex design I would use them so as to not “change the recipe”.
sreten said:
Sreten, Electron;
I see the deflex is not as ideal as it appears in their data.. So sreten's trusted advice is using acoustic foam. As far as I understand, this in some aspect resembles Electrons experiences too, as the Black Hole/Whispermat is a layered composite, featuring polyurethane acoustic foam on top..
What seem to keep details high in the "dampening sandwich mats" such as BH5 and WhisperMat is their utilizing of a thin air barrier film on top of the foam, thus increasing air flow in the box. As I understand it, this will mean that for me to obtain the correct volume, I cannot count the foam in as box space, umm?
If I am correct so far, I like the idea. I will have benefits of foam damping, yet not the usual downsides in loss of detail. The target driver is Thiel Ceramics, so attention to details is crucual.. It is my reason for choosing the driver. As you might have seen on the previously posted pic, 90 degree angles is avoided to reduce corner reflections. However, I could still use some (again Spectra Dynamics) CornerBlocks (massive polyurethane) in each corner. Recommendable?
Electron; My biggest concern now would be is how thick this Whispermat you utilized was? it seems available in several calibres, I want to keep it compact, yet not underdo it...
Also, will there be a beneficial effect by adding a lead layer inside the box? weight is not an issue... size is...
One more thing: Wich frequencies does the whispermat excel at? My monitor will be -3dB @ 44Hz, and is crossover point is at 3150Hz. 24dB/oct slopes.. Is this whisperthing my ideal choice, or should I maybe make my own sandwich using bitumen sheets and a film on top (i have some thin plastic film on spraybox that I could use)?
Thanks so far
Rocky said:
Whispermat is a barrier (dense rubbery mat) - foam combination. The barrier (mat) goes on the cabinet side and the foam the interior of the cabinet. Blackhole5 is more complex as it has two thinner layers of foam with a layer of other material in between. Both have foam that faces the interior of the cabinet. So I don't think that there is increased airflow in the box as you describe.
Their main attribute is that they have a foam structure that seems to work by reducing reflections within the cabinet etc. and a mechanical damping material that reduces mechanical resonances of the cabinet.
http://www.e-speakers.com/products/blackhole5.html
Here is the recommendation from the Seas L15RLYP / 27TFFC System page (hushcloth is the nabm of the Whispermat foam layer. It is a fine grained foam.):
"I used Whispermat 2 (WM2) on the back and the sides near the back, and Whispermat 1 (WM1) on the sides near the front, on the driver side the the shelf brace. The WM2 had 1" hushcloth, a mass loaded barrier layer and 1/4" isolation layer. The WM1 had a 1/2" hushcloth and a mass loaded barrier layer. The WM1 had to be glued in place with 3M 90, but the WM2 was just pressed into place in the back, with the size cut so pressure holds it in place. "
To save money I just bought the WM1. I figured if it was not sufficient on the back wall I could add something such as more foam etc.
I don't think people tend to count foam or lining the walls with polyfill as taking up cabinet volume. The heavy barrier parts would though. Blackhole seems to count about ¼” as "taking up volume".
Don't know the answers to the other questions.
Rocky,
It seems to me you have to seperate the mechanical damping
of the walls and the acoustic damping of the resonant airspace.
Mechanical damping is achieved by damping layers, structural
foam can be used to increase effective wall thickness and as
you say will reduce internal volume.
Your walls appear to be stiff enough to me so adding damping
without reducing volume too much is the way to go, extra lead
lining sounds like a good idea to me.
IMO with the amount of lead composite mechanical / acoustic
damping products are not needed. You should line the box
with acoustic foam, unless you regard a "lively" midrange
that is due to airspace resonances a good thing, I don't .
sreten.
It seems to me you have to seperate the mechanical damping
of the walls and the acoustic damping of the resonant airspace.
Mechanical damping is achieved by damping layers, structural
foam can be used to increase effective wall thickness and as
you say will reduce internal volume.
Your walls appear to be stiff enough to me so adding damping
without reducing volume too much is the way to go, extra lead
lining sounds like a good idea to me.
IMO with the amount of lead composite mechanical / acoustic
damping products are not needed. You should line the box
with acoustic foam, unless you regard a "lively" midrange
that is due to airspace resonances a good thing, I don't
. sreten.
sreten said:
Sreten,
Can you elaborate on your comment on foam increasing effective wall thickness. Do you mean the addition of foam gives similar characteristics to making the walls out of thicker material? For example 1" instead of 3/4" MDF. Or are you saying that the interior volume is now the same as if the foam was say MDF.
I am used to thinking that the job of the foam is to attenuate a certain range of frequencies bouncing inside the box so that standing waves do not affect cone movement, generally in the mid range. Lower frequencies ignore the foam but then their longer waves are not as much of a problem in normal box sizes.
I am not used to thinking the foam changes the perceived box size. Here is this statement about Blackhole5 that implies they do not count the foam portion as volume:
"Blackhole 5 is 1.375" thick, but it only displaces 0.250" of incompressible air. " (Whatever that means
)You can make a pad out of a damping layer and structural
foam, the purpose of the foam is to stiffen by increasing wall
thickness, with another layer of acoustic foam added.
Acoustic or open cell foam is entirely different to structural foam.
The part of the pad made of structural foam has a real
volume, the part made of acoustic foam does not.
sreten.
foam, the purpose of the foam is to stiffen by increasing wall
thickness, with another layer of acoustic foam added.
Acoustic or open cell foam is entirely different to structural foam.
The part of the pad made of structural foam has a real
volume, the part made of acoustic foam does not.
sreten.
Just done some checking :
BH5 does not contain structural foam.
It has 1" of acoustic foam, which slightly increases internal volume.
The other 3/8" uses open cell foam to decouple a layer of
damping and also has a damping layer for the wall proper,
or so they say. I'm not convinced about the decoupling
but I'd say the thin foam layer makes the amount of
damping for its weight more effective.
Whispermat doesn't contain structural foam either,
IMO the basic sheet is the same as using vinyl floor tiles.
However IMO a suspended vinyl layer between sheets of
foam would not work well on the scale of speaker cabinets.
So were's the stuff I've seen with structural foam ?
sreten.
BH5 does not contain structural foam.
It has 1" of acoustic foam, which slightly increases internal volume.
The other 3/8" uses open cell foam to decouple a layer of
damping and also has a damping layer for the wall proper,
or so they say. I'm not convinced about the decoupling
but I'd say the thin foam layer makes the amount of
damping for its weight more effective.
Whispermat doesn't contain structural foam either,
IMO the basic sheet is the same as using vinyl floor tiles.
However IMO a suspended vinyl layer between sheets of
foam would not work well on the scale of speaker cabinets.
So were's the stuff I've seen with structural foam ?
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