Acoustic foam for a Sub in cabinetry

[genesis471]

Hi, I have a MK V-75II (sealed front firing sub, no ports) subwoofer enclosed in cabinetry. I have read that this is not the best but I don't have any choice based on room design. I am wondering what acoustical foam the article is speaking of below and where I can get it? I do have another sub in the back corner of the room, opposite of the MK in the cabinet. I am just trying to tune the system and know that the MK is doing exactly what is said below, so I want to try and correct that as much as possible so the sub doesn't distort as much, or at all.

Thanks for your help

-Mike
some details:
Klipsch Floor speakers in cabinetry
Klipsch Center speaker in cabinetry
Klipsch Surround speakers
Yamaha dual subwoofer - rear
MK subwoofer - front in cabinetry
Denon AVR-3805
Hitachi HDTV, also flush in cabinetry
Rectangle room - half below grade, drywall framed over concrete pony walls and carpeting, fully finished.



Tip #2: Bracing & Acoustics
If you must place a marketed subwoofer in cabinetry make sure the cavity where you are placing it is heavily braced and make sure that the cavity when lined with heavy acoustical foam is just big enough for your subwoofer to fit in. This will eliminate potential unwanted resonance from the cabinetry and the subwoofer. A little finish carpentry will be necessary here; sealed front firing subwoofers work best in this application but front ported front firing subs can work as well. Rear ported subwoofers are not recommended because of port huffing and obviously floor firing subwoofers are not recommended. I like to use subwoofers from manufacturers that use an external rack designed subwoofer amp That way I can get a super tight fitting subwoofer and have all the adjustments for the amp in the rack this also prevents the subwoofer amp from overheating.

 

[Jason Coleman]

This is probably more than you need, but it would certainly do the trick!

http://www.auralex.com/

Jason

 

[Votrax]

http://www.partsexpress.com/webpage.cfm?&Webpage_ID=3&DID=7&CAT_ID=48&ObjectGroup_ID=137&SO=2

 

[plhart]

Genesis471-

You want to use cheap foam padding which is usually closed cell foam that you can get at a cloth mart or upholstery shop. The purpose of the foam is only to hold the sub. Actually, your sub will be capable of a better impulse response the more tightly it is coupled to the cabinet. So bolting a 2x4 to the sub's cabinet and then into the holding cabinet so the whole sub is rigid is best.

"Acoustic" or open cell foam is not necessary for this application because you're not trying to absorb any of these low frequencies and the open cell foam wouldn't be thick enough to do much bass absorbing in any event.

You've "boxed" yourself in so to speak in that you're leaving no room for alternate sub placement. So the worst case scenario is that your sub will be in an exact null with respect to your listening position and it will hardly work as far as adequate bass output.

The best case scenario is if your sub's location couples well with the room and doesn't have a huge bass peak at a single frequency at the listening position. Chances are though that you will have some sort of peak which may lead to the dreaded one note bass syndrome.

This is why I'm an advocate of subs with single band parametric EQs built in or of add-on outboard parametric EQs. Both the latter devices may require additional expertise in calibration before the set-up can perform optimally.

 

[WmAx]

So bolting a 2x4 to the sub's cabinet and then into the holding cabinet so the whole sub is rigid is best.

Of course, in the event that the sub is rigidly coupled with the cabinet structure, he should also be concerned with the specific resonant properties of the cabinet and other structures that are rigidly coupled to this cabinet. Potentially, direct vibrational excitation can result in problematic response peaks due to these strcutures if resonant points are within the passband. I'm for the decoupled method; less potential complications. I sometimes mount full range speakers and subwoofers on shock absorberbant structures when used on wooden substructure floors. Sometimes the floor structures will have easily excited primary resonant frequency in the passband of the subwoofer. As for impulse response; I can not conceive of why a subwoofer should be required to produce the sharpest rising impulse except if this is just a technical objective.....

-Chris

 

[genesis471]

Thanks to all for the links and other interesting information. I will spend a little money and do some experimenting... hoping that something will do the trick!

-Mike