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Acoustic Stuffing/Foam

Discussion in 'Amps and Cabs [BG]' started by Rockbobmel, Feb 18, 2003.


  1. Rockbobmel

    Rockbobmel Supporting Member

    What happens when you really stuff your cabinets with egg crate foam or stuffing material?? Will it make the lows clearer or deeper??
     
  2. CS

    CS

    Dec 11, 1999
    UK
  3. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Actually that thread is for a completely different product. That thread is talking about a ashphalt based deadener that they use to stop things vibrating and/or trap unwanted noise. It weighs a proverbial tonne. It doesn't absorb sound but instead bounces it back in the direction in which it came.

    The stuffing material Rockboby's asking about is the lightweight foam found inside many cabinets that absorbs sound. It's primary job is to prevent standing waves. If a particular frequency bounces around the cabinet, it will increase in volume with each bounce but may not leave the cabinet. It'll just get louder and louder till it stuffs your sound up.

    The other job of the foam is to tighten up the bottom end, makeing sound fuller and less hollow. It increases the efficiency of the porting.

    I'm still learning about cab design so if one of the guru's would like to chime in here it would be great.
     
  4. Rockbobmel

    Rockbobmel Supporting Member

    I changed the title.
     
  5. BruceWane

    BruceWane

    Oct 31, 2002
    Houston, TX
    Depends on how far you go with it..........lining some of the interior walls of the cab will reduce standing waves and will help to tighten up the sound; the added clarity, in my experience, does help most cabs to sound a bit deeper. It's probably just a matter of the sound being more defined, less flabby, than actually boosting the lows.

    I like to use the insulation they use under automobile carpet (often called "jute" in the upholstery biz) for this application. Very "dead" without being thick or heavy. No itchiness like fiberglass insulation. You can get it at any auto upholstery shop. A decent heavy duty stapler will tack the stuff in place. It's pretty hard on scissors, so don't borrow anybody's good sewing scissors to cut it.

    Now, if you actually go beyond lining and get into stuffing the cab with acoustic filler, you are in effect making the cab larger. The more stuffing, the bigger the cab "seems" to the speaker, up to a point. How this affects your sound depends on the speaker and cabinet volume/tuning. If the cab is actually smaller than the speaker is designed for, making the box appear larger will help the low end; if the cab is the correct size already, making it appear larger will generally cause the sound to get muddy (group delay will get too great).

    Most bass guitar cabs are a little smaller than they ought to be, so it's worthwhile to try either dampening or stuffing out......it's cheap and completely reversible.

    Acousta-Stuf is specifically made for this.........

    Info on Acousta-Stuf
     
  6. So if I pack my EB-HD212 to the gills with "Acousta-stuf" it will extend deeper +bigger??
     
  7. BruceWane

    BruceWane

    Oct 31, 2002
    Houston, TX
    Not neccessarily........like I said -

    "if the cab is the correct size already, making it appear larger will generally cause the sound to get muddy (group delay will get too great)."

    - but it's worth a try; either approach (dampening standing waves or stuffing to add cab size) is cheap and entirely reversible.

    Since you can't tell if your box is too small unless you have the theile-small parameters for the drivers - and most cabinet manufacturers won't give you those specs - all you can do is try it.
     
  8. Rockbobmel

    Rockbobmel Supporting Member

    I saw the AcustaStuf in PartsExpress. The subwoofer that is pictured in the catalog hows some egg crate dimple foam. I know my cab has about 1 1/2" around the interior, but I'll try using more. And as you said it is reversable.
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    that dimple foam is good, looks trick, but it's megga expensive compared to the the white foam. Here in Oz, that dimple foam if $14 per square and you'd need at least 5 squares. The white stuff is $10 per roll and a roll does a whole cabinet.
     
  10. Rockbobmel

    Rockbobmel Supporting Member

    What about the bedding mattress tops? Ain't it the same? I think you can get em at a sporting goods store too..?
     
  11. To the best of my knowledge: this is only valid for a closed cabinet. A ported cabinet will not gain from stuffing, because it is already gaining a lot from the porting. The gain from the stuffing is in the exact same frequency area as the port tuning, and porting is a far better method of extending the low end.
     
  12. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    I've used those before with good success (and cheap prices). I think they will kill reflections from high frequency drivers but I'm not sure they do much to extend bass response.
     
  13. etherealme

    etherealme Supporting Member

    Jun 26, 2007
    Louisiana
    Can anyone chime in on their experience using this stuff? Not so much concerned about how well it will clear up tone (I'm convinced in that realm) but the details on attaching to inside of cab, does it stick or require adhesive or staples, and how much to buy to do approximately a 23" x 18" cab.

    Thanks in advance. Many a search done...:smug:

    I'm going to use this on a double 4" tube ported birch single 15" cab where the dimensions are correct for the size driver I'm installing. I'm not worried about increasing the perceived dimensions for the driver either; just want to try out the differing tone when dampened..
     
  14. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The answer to the original post is that all cabs should be fully lined with an inch to two inches of foam or polyester batting, which absorbs midrange reflections. Without it midrange response will be very ragged. It has no effect on the lows. With a sealed cab that's too small stuffing it with damping can lower the Q of the system, which can tame a boomy response. It does not make the cab perform like a larger box would, though.
     
  15. etherealme

    etherealme Supporting Member

    Jun 26, 2007
    Louisiana
    Thanks a bunch for clarifying that aspect, Bill. Gotcha. It's the midrange exactly that I'm trying to absorb. I'm glad you mentioned ALL cabs should be fully lined too!

    Anyone with experience applying acousta-stuf want to chime in on the particulars regarding attaching to inside of cab? Does it stick or require adhesive or staples, and how much to buy to do approximately a 23" x 18" cab??

    Acousta-stuf
     
  16. bobcruz

    bobcruz

    Mar 10, 2004
    Alameda, CA
    I can't help with your question concerning applying the stuff, but you can save a bunch of money by buying your polyfill stuffing at a fabric store. Same stuff and I think it may come in sheets that would be easier to spray-glue or staple into place.
     
  17. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    AcoustaStuff is a mass, and doesn't work well for lining cabs. Foam or batting is much easier to work with, and you can get it at Walmart.
     
  18. etherealme

    etherealme Supporting Member

    Jun 26, 2007
    Louisiana
    Thanks guys!

    Now we have a whole thread with even more valuable information on the topic. :D