I hade the chance to listen to two speakers: same XO, same Scan Speak Woofer, same ATC Mid dome
and a SS relelator soft or BE dome.
the BE dome was clearly better! more 3D, better resolution, clean heights.
for me BE is THE dome material.
P10, must have been an interesting looking box with the Deca and a Kef B200. Tough on the WAF though. 😀
Hi, tvrgeek
Good call on the Corning 705 !! I used various grades of those Corning products (701 to 704) with very good results. A great product to make your own sound absorbers, room treatments and speaker stuffing.
Good call on the Corning 705 !! I used various grades of those Corning products (701 to 704) with very good results. A great product to make your own sound absorbers, room treatments and speaker stuffing.
Amen to the Corning rigid fiberglass products.
I've made many panels, gluing various thickness sheets to thin luan ply, and then wrapping it with fabric.
One of my favorite finds has been pipe insulation, 24" diameter, 36" long.
Wrap with fabric, and cap the ends by gluing ply on them.
Bass traps, and double as incredibly strong, super lightweight stands. I've put 300lbs on them no problem.
I've made many panels, gluing various thickness sheets to thin luan ply, and then wrapping it with fabric.
One of my favorite finds has been pipe insulation, 24" diameter, 36" long.
Wrap with fabric, and cap the ends by gluing ply on them.
Bass traps, and double as incredibly strong, super lightweight stands. I've put 300lbs on them no problem.
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Hi, mark100
I never looked at the large diameter pipe insulation. I learned something new today !!!
Thanks for sharing, should help DIY' ers make some good corner bass traps !!!
I never looked at the large diameter pipe insulation. I learned something new today !!!
Thanks for sharing, should help DIY' ers make some good corner bass traps !!!
Hi Joe, yep, love learning something new.
Happens often for me, within this fine DIY audio hobby & generous community 🙂
Happens often for me, within this fine DIY audio hobby & generous community 🙂
note that pipe insulation is often made of very high density mineral wool, higher then is optimum, so it might be a good idea to have an eye on this and choose less dense versions
Why do you think the high density is an issue? For moderate thickness (up to 6") HD mineral wool (around 100kg/m3 or higher) does an excellent job.
With increased density it becomes more reflective, bbc did some studies showing this, i think others has done studies aswell
With absorptive material there's obviously an optimal range of density. Not dense enough and some of the sound will still pass through, hit the cabinet and reflect back. (And also vibrate the cabinet walls)
Too dense and you just reduce the volume of the enclosure and the surface of the "absorptive" material becomes the new boundary of the enclosure and you just lose box volume with no real gain.
Absorptive material in cabinets has two different functions though - dissipating standing waves, and isolation of internal sound waves from cabinet walls.
In the first case stuffing (open cell polyester etc) is more effective as the cabinet boundaries are low velocity high pressure points where absorption is not very effective, so you want the absorption material to be low density, high in volume and extend well into the middle of the cabinet where velocity is high - eg stuffing.
On the other hand if the objective is to provide isolation between the internal sound waves and cabinet walls you want a denser lining which is on the walls - while some of the sound will still reflect around inside it will act as a barrier to greatly reduce the cabinet panel vibrations and thus reduce spurious radiation from exterior cabinet walls. Carpet underfelt works well for this as it is fairly dense but not excessively so, and it has sufficient mass to act as a good isolation barrier. Because of the relatively high density I subtract the volume of carpet underfelt from the cabinet volume when calculating the effective cabinet volume.
In a bass reflex enclosure you can't use stuffing as the high volume low density stuffing greatly damps down the box Helmholtz resonance and as a result throws away most of the benefit of a bass reflex cabinet and essentially turns it into a lossy closed box, giving the performance of a much smaller box.
However you can and should still use thin dense lining on the walls like carpet underfelt as this provides a lot of isolation between the internal sound waves and cabinet panels reducing spurious output from the panels, without affecting the Helmholtz resonance too much, and the internal standing waves can potentially be dealt with in EQ. (Internal standing waves, as long as they don't cause panel vibrations actually cause very little effect on the far space response as they can only be heard if they can pass through the speaker cone and surround)
For a sealed midrange enclosure I would definitely use stuffing and possibly in addition lining, to get maximum damping of standing waves and maximum isolation to the other cabinet volume and the portion of the front panel belonging to the midrange enclosure. As with the bass reflex enclosure I would subtract the volume consumed by the dense lining (like carpet underfelt) from the box volume, but the volume consumed by a low density material like polyester is not subtracted.
Too dense and you just reduce the volume of the enclosure and the surface of the "absorptive" material becomes the new boundary of the enclosure and you just lose box volume with no real gain.
Absorptive material in cabinets has two different functions though - dissipating standing waves, and isolation of internal sound waves from cabinet walls.
In the first case stuffing (open cell polyester etc) is more effective as the cabinet boundaries are low velocity high pressure points where absorption is not very effective, so you want the absorption material to be low density, high in volume and extend well into the middle of the cabinet where velocity is high - eg stuffing.
On the other hand if the objective is to provide isolation between the internal sound waves and cabinet walls you want a denser lining which is on the walls - while some of the sound will still reflect around inside it will act as a barrier to greatly reduce the cabinet panel vibrations and thus reduce spurious radiation from exterior cabinet walls. Carpet underfelt works well for this as it is fairly dense but not excessively so, and it has sufficient mass to act as a good isolation barrier. Because of the relatively high density I subtract the volume of carpet underfelt from the cabinet volume when calculating the effective cabinet volume.
In a bass reflex enclosure you can't use stuffing as the high volume low density stuffing greatly damps down the box Helmholtz resonance and as a result throws away most of the benefit of a bass reflex cabinet and essentially turns it into a lossy closed box, giving the performance of a much smaller box.
However you can and should still use thin dense lining on the walls like carpet underfelt as this provides a lot of isolation between the internal sound waves and cabinet panels reducing spurious output from the panels, without affecting the Helmholtz resonance too much, and the internal standing waves can potentially be dealt with in EQ. (Internal standing waves, as long as they don't cause panel vibrations actually cause very little effect on the far space response as they can only be heard if they can pass through the speaker cone and surround)
For a sealed midrange enclosure I would definitely use stuffing and possibly in addition lining, to get maximum damping of standing waves and maximum isolation to the other cabinet volume and the portion of the front panel belonging to the midrange enclosure. As with the bass reflex enclosure I would subtract the volume consumed by the dense lining (like carpet underfelt) from the box volume, but the volume consumed by a low density material like polyester is not subtracted.
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i do not fully agree with you, with absorption in the box you want to absorb reflections and you want it for the isothermal process
for isolation you need a more dense material then compressed felt to the cabinet walls, thick layer of bitumen works great for this. the felt used by some famous builder may look good, like eye candy, but i think it is waste of effort and material
for isolation you need a more dense material then compressed felt to the cabinet walls, thick layer of bitumen works great for this. the felt used by some famous builder may look good, like eye candy, but i think it is waste of effort and material
What kind of box though ?
In a closed box yes, in a bass reflex box, no. You cannot use stuffing in a bass reflex box or take advantage of isothermal processes. The box must remain mostly empty.
I think you're confusing isolation with panel damping. Bitumen works by being a heavy lossy material that when bonded to the cabinet wall converts bending motion of the panel into thermal energy thus provides damping to panel resonances. Sand filled partially hollow panels is a similar idea.
A bitumen layer will provide a small amount of isolation as well as the panel damping but that's not its primary action as it's actually too dense to act as a lining or stuffing for standing waves.
Carpet underfelt does not mechanically damp bending of cabinet walls - it is not heavy enough and is only lightly bonded (tacked) into place. What it does provide is isolation of the acoustic wave from the panel - absorbing some of the energy and reflecting most of the rest away from the panel. The underfelt will vibrate slightly and in doing so reduce the excitation of the panel as it is decoupled from the panel.
So a bitumen layer will primarily damp the vibrations of the specific panel resonances while carpet underfelt will mostly reduce direct excitation of the panel by internal sound waves. These are two different methods of action.
Of course there is no reason why you can't combine the underfelt and bitumen as they are performing different roles, one is providing isolation and one mechanical damping of the panel.
Carpet underfelt is definitely not eye candy, (I don't see how it could be anyway as it's on the inside where it can't be seen...) I've used it on all my 2 and 3 way bass reflex systems and it works quite well with minimal effort and can be easily tacked or stapled to wood. When I say carpet underfelt I'm talking about 10mm thick real wool underfelt not synthetic rubber underfelt as is often found on carpets these days.
It doesn't absorb midrange standing waves as well as stuffing (since it's a lining at the low velocity point) so for a closed box (including a midrange cavity) I would use stuffing but for the main cabinet in a bass reflex I would use the wool underfelt.
Even if I used Bitumen or another constrained layer mechanical damping technique I would still use the wool underfelt in addition to that.
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i do not think this is true, yes for a closed box it is a lot easier to fill the box without that much care how it is done, for a reflex box it is a bit more complicated. a reflex box that reaches up in the midrange should definitely use absorption, but not done like for a closed box. for absorption mineral wool is excellent. low density synthetic wool is great for the isothermal process. boxes for low frequencies only, subwoofers, does not need damping but can take use of the isothermal process. low density synthetic wool which does not alter the resonance q but lowers the resonance frequency.
maybe so, but for soundproofing you need to lower the source sound level. you either use the volume control to lower the sound output or you add damping to lower the sound energy. thick layer of mineral wool is very effiecient to damp sound energy. a panel that vibrates needs mass to stop vibrate, bitumen is very good at this. i can not see what a dense felt underlay can do better at this? dense felt is good to absorb impact noise, and density is optimized to the impact force, i can not clearly see any advantage of this in a loudspeaker box
some builders takes a lot of pictures under the construction work. i see this only as a way of selling more of expensive materials