No one is questioning that. I have stated clearly my adherence to the importance of cavity damping. What I am saying is, perform the requirements in order of importance. Top to bottom and as a package. Damping has little value until the cabinet deficiencies are corrected. I am seeing cart before the horse advice here.
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It actually adds substantial resistance particularly when compared to no-fill airspeed near the center of a box.
It’s a great way to reduce depth of field, but it almost always looks better in decay plots. The common response from listener’s is that a typically stuffed cabinet “sucks the life out of the drivers”. It makes less of an audible difference if the passband is only at lower freq.s, the higher in freq. you go the worse it is though there are drivers that display this result far less than others (usually those with high Rms and low Qm and drivers with stiff surrounds in general - though these drivers typically don’t have very good depth reproduction regardless).
However in the case of a vent entrance (about 1” away from port) it’s worth it to reduce upper freq. resonances.
Note: I actually advocate a fair amount of absorption in-box, just not where it’s usually placed.
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Without measurements, not convinced, though from some of Altec's/Heathkit's similar damping schemes I believe it's a more broadband approach to my preferred pioneer's modest cab wall, 'critical' vent damping.
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It's also not my experience with dampening a ported speaker. You quickly loose 3-4dB of port efficiency with so much dampening, also when there is a direct path between driver and port. The losses in the backvolume simply rise a lot (that's what we need against the resonances) and the port can't work at full potential.
Nevertheless it's better to loose 2dB and have no resonances as keeping it ringing.
Nevertheless it's better to loose 2dB and have no resonances as keeping it ringing.
Well I should keep my mouth shut regarding ported speakers, since I gave up on them long ago. I could never get the sound I wanted from them. So I defer to the expertise of those people who actually build bass reflex boxes today...
Because of room resonances.
Try loudspeaker placement in the room.
It's worth the effort.
At some other box places and listening position the resonances are less or gone.
Try loudspeaker placement in the room.
It's worth the effort.
At some other box places and listening position the resonances are less or gone.
For large(-ish) ported boxes I still like acoustic foam tiles best.
At 10cm thickness decent ones have an absorption coefficient of 0.93 at 200Hz (93% absorption) and >1 above 250Hz.
Below that they are quite ineffective which is basically what you want in ported box. Most important is directly behind the driver where I sometime double up with a thinner pyramid tile. AS4_DataSheet.pdf
Easy to cut and mount too. I use this stuff to fix them:
908 Black Jack DPM | Bitumen & Roofing Supplies UK | Everbuild
In fact I paint the entire inside of my boxes with that because a layer or two of heavy rubber never hurt the performance of any cab.
At 10cm thickness decent ones have an absorption coefficient of 0.93 at 200Hz (93% absorption) and >1 above 250Hz.
Below that they are quite ineffective which is basically what you want in ported box. Most important is directly behind the driver where I sometime double up with a thinner pyramid tile. AS4_DataSheet.pdf
Easy to cut and mount too. I use this stuff to fix them:
908 Black Jack DPM | Bitumen & Roofing Supplies UK | Everbuild
In fact I paint the entire inside of my boxes with that because a layer or two of heavy rubber never hurt the performance of any cab.
Big time! This was the way I damped medium/high voltage wound rotor motor starter 32" x 32" x 90" cabs made from welded up 10 ga CRS where it takes angle iron and boiler plate to brace, damp.
It smells a bit like a freshly tarmac'd road when you apply it but it dries to a totally odourless black. It is kinda dark brown when wet.
Water-based so no fumes to worry about.