Padding in Closed Back guitar cabs?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by aortizjr, Dec 10, 2004.

  1. aortizjr

    aortizjr Member

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    Hi...

    Just curious mainly... I think that Marshall 1960 series have insulation inside. I have opened up Bass cabinets and noticed padding inside the cab.

    However, my open back cabs have no padding. I haven't looked at some of my other closed back cabs.

    Anyway is padding closed back guitar cabs standard? If not what are the effects to running padded vs unpadded?
     
  2. KLB

    KLB Member

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    Placing sound absorbing material inside a closed cab will help absorb the back wave from the speaker, reducing the cabinet resonance. Depending on your tone goals, this may or may not be what you want. Best to experiment. An overly damped (sound absorbed) cab can sound thin and weak.

    Most closed back guitar cabs do NOT have sound absorbing material. Virtually ALL high-fi audio cabinets do.
     
  3. aortizjr

    aortizjr Member

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    Interesting...

    Would the type of wood also be something to consider?

    For instance if your guitar cab is made from a tone wood like birch or pine, you want it to resonate more. So no padding.

    But if it is say MDF or some other cheapy plywood, use padding so it won't resonate the bad tone?

    Hence why perhaps most HiFi cabs never mention the wood used, but guitar cabs pretty much always do. Now of course I am not a big HiFi guy. But that is just my observation in general low-mid range HiFi purchses for Home Entertainment.
     
  4. KLB

    KLB Member

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    Sometimes, bare (tone)wood with no sound absorption is the best tone for a particular amp, speaker and guitar combination. I have a little ported 1x12 made from birch that is unfinished. It sounds much bigger than the size. If it were bigger, it might get too boomy, with the bass notes ringing too long.

    Trial and error is the fun part of this hobby!

    The best sounding audio speakers I've heard were $50K a pair, made by California Audio Technologies. They use CORIAN for the cabinets! Each speaker weighs 300 lbs.

    Cheers
     
  5. Lonely Raven

    Lonely Raven Member

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    I used to hand build Hi-Fi speakers for 3 watt tube amps
    and grew up with the resonance is bad crowd. So going to
    guitar amps where resonance is good confused me at first.
    I get it now.

    The cab resonates which helps give some of that 3d projection
    and can accentuate or diminish certain frequencies.

    Now, my confusion is....if you build a guitar cab that resonates,
    but put an SM57 in front of the cone to record it, doesn't that
    pretty much negate any advantages in your hand made
    antique pine guitar cab?
     
  6. sundaypunch

    sundaypunch Member

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    I have a blonde Fender Bassman with the 2x12 cabinet. I've played it both with and without padding. I tend to like it better without it. Just pull the screws and try it with some insulation inside. You can easily A/B it within a few seconds to see what the tonal difference is.
     
  7. aeolian

    aeolian Member

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    The speaker is very highly affected by the enclosure it's mounted in. Just as the reactive load of a speaker affects the sound of an amp, the cabinet is part of that reactive load. For instance, in a ported cab, where the cab resonates, it forces the impedance of the speaker very high. Below that frequency, the impedance drops far below the nominal.

    Internal reflections come back and hit the cone. This tries to drive the cone to move together with those waves. The relatively wimpy cone of a guitar speaker can actually have small areas of it vibrating due to sound from inside the cabinet rather than the primary force from the voice coil.

    The hi-fi guys go to great lengths (even sacrificing kitchen counters) to make these effects go away. But the right combination can be magic for a guitar.
     
  8. KLB

    KLB Member

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    As mentioned in an earlier post...

    A couple of years ago, I lucked into a homebuilt 1x12 modeled on the Bogner cube, but about 1/2" deeper and with a 2x10" oval port on the bottom back third. It is unfinished 3/4" birch all sides, with a 1/2" baffle. No absortion inside, either.

    Something about the size and material makes this cab resonate musically with just about every speaker/amp combination I've tried. It is especiallly juicy with a Fuchs FAT-S1 driven by a Fuchs ODS 50 and humbucker guitar.

    Sorry, but the maker isn't able to build any more. I heard he lost his woodworking shop as a result of a divorce. Ouch!
     
  9. Matt Gordon

    Matt Gordon Senior Member

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    I have a Mesa Recto Standard 4X12 with no material inside and for some reason its still a pretty tight sounding cabinet.
     
  10. Randy

    Randy Member

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    I built a pair of ISO cabs for recording and covered every interior surface with eggcrate foam thinking it would sound better to mic in a 'dead' space, but now I'm wondering if a little more reflection might sound better. Thing is the back wall is only about 20" from the speaker and the side walls are only 3-4" from the speaker edge (it's 18" X 18" X 30").

    Anyone have any ideas on what might work best in this setup?
     
  11. aestus

    aestus Member

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    Anybody know what the resulting change in tone would be if you lined the inside of your cab with either egg crates or wavy foam on the inside of a marshall 1960 type cab? I have already done this to my cab, but I forgot how my cab sounded before I lined the insides with the egg crate type foam. I initially did it, because an audio engineers said it would beef up my sound and may the low end frequencies even bigger. He says the wavy type pattern inside the cab tricks the cab into thinking it's bigger and thus gives bigger bass response. I do note that my cab is a bit "drier" sounding compared to other Marshall cabs.

    I wonder if anyone else has done this and what are their opinions on it are?
     
  12. kannibul

    kannibul Member

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    My 1960A that I bought had no padding.

    I added some, and it made it sound better.
     

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