Stuffing a cab with foam

ESchapESchap Frets: 1428

I've got an old WEM closed back 1x12" cab which no matter what amp I use it with, or speaker I put in, it sounds "boxy" at volume. (Latest attempt is a Celestion Gold). 

It's a fairly big cab for a 1 x 12, I believe that it could be originally bought in 2 x 10 format as well, hence the size.  Its all 15mm ply, including the baffle.

What would the effect of packing it with foam be?  and what type of foam?

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Comments

  • A voice somewhere from my distant past thinks that something like carpet underlay attached to the inner faces and BAF wadding* lightly filling the inner space will deaden inner reflections and also make the cab acoustically "bigger" and more inert.  On the other hand I could be completely wrong, it was all so long ago - not sure if that helps.

    (BAF wadding* is a loose "spongy" acrylic fibre material used in lots of other things too)

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  • ICBMICBM Frets: 71960
    edited December 2013
    You can get acoustic wadding for hi-fi and PA cabs - that will almost certainly work better than foam, which would have the effect of making the cab effectively smaller... probably what you don't want if it sounds boxy already.


    Looking at the seller's location I have an idea where that may have come from, too ;).


    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • ecc83ecc83 Frets: 1591
    edited December 2013
    ICBM is right in that you need acoustic wadding "BAF" to do a proper job or the ultimate hi fi stuffing, long fibre wool but this must be well teased out and loaded at the correct value of gramms per cu centimetre (I kid you not!) .

    The sad fact is tho' that none of this will work! The Infinite Baffle principle can only be applied to very low resonance cones* (C 20Hz) with very long and linear cone excursions. Guitar speakers are neither and stuffing the box will simple reduce the overall sensitivity. 

    The only solution that might work is to remove about 1/3rd of the back panel area and make it an open cab.

    *Unless you have a fekkin' ENORMOUS box! This is how they got a 1/2 decent bass response pre the I.B. cab. 12inch woofers in 8cuft reflex cabinets!

    Dave.
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  • Aye, that's the stuff ICBM.  BAF stood for Bonded Acrylic (or acoustic) Fibre IIRC.

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  • ESchapESchap Frets: 1428

    Thanks to all for the suggestions. 

    Hmm ... two votes against stuffing.  I'm sure you're right.  Trouble is with the back off the cab all together it doesn't sound any better, well, perhaps a little.   I take it that having a 1/3 gap open back is quite different to a 100% open back?

    Not got much of a clue with this "acoustics" stuff, though I'd like to have ... Any recommendations for reading material on the subject would be much appreciated. 

     

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  • ecc83ecc83 Frets: 1591
    Aye, that's the stuff ICBM.  BAF stood for Bonded Acrylic (or acoustic) Fibre IIRC.
    Bonded Acetate Fibre is the stuff that will do nothing but make the speaker quieter and dimmer.

    Dave.
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  • ChrisMusicChrisMusic Frets: 1133
    edited December 2013
    Cheers for the update ecc83, I wasn't sure how it affects the acoustic properties of guitar cabs.   :)

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  • ecc83ecc83 Frets: 1591
    ESchap said:

    Thanks to all for the suggestions. 

    Hmm ... two votes against stuffing.  I'm sure you're right.  Trouble is with the back off the cab all together it doesn't sound any better, well, perhaps a little.   I take it that having a 1/3 gap open back is quite different to a 100% open back?

    Not got much of a clue with this "acoustics" stuff, though I'd like to have ... Any recommendations for reading material on the subject would be much appreciated. 

    AFAIK there is no published data about the "design" of guitar speaker cabs, probably because they are almost all "cut and try" . If there was a particular size/design then all gitacbs would have long ago converged to it. Look at nearfield monitor speakers? For a given cone size they are all about the same cabinet volume. 1x12s differ by a factor of at least 2 in cab volume (and 10 to 1 in price!) . 

    Then, virtually all the high (100dB) sensitivity drivers have a resonance at 75-80Hz. The box will push this up to around 90-110Hz and that and its harmonics could be the reason for the boxiness. Something like a Greenback at 55Hz might be better but then you will loose some headroom and power handling capacity. 

    Last thought. Have you tried the cab in another room? Could your space that is "honky"!??

    Dave.

     


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  • 57Deluxe57Deluxe Frets: 7329
    I read through this and took your advice... the 1x10 Turkey tasted shite though...
    <Vintage BOSS Upgrades>
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