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Thread: Amp rack sharing a surface with sub enclosure - decoupling?

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    Amp rack sharing a surface with sub enclosure - decoupling?

    This is just one of those compromises related to maximizing my system while minimizing it's footprint, keeping all the utility that led me to fall in love with this car. Looking for suggestions on keeping my amps isolated from the vibrations - and there will be vibrations. It's a sealed box, I'll probably be running my 12W7, but also have a GTi 12 and a few XBL^2 prototypes and a Brahma 12. Something with monster excursion will be shaking things up.

    Looking for ideas on how to facilitate this plan without shaking the coils off my amp's circuit boards:

    Here's what happened -
    I started down the path of framing out that box - it started with a plan to 'glass a box into the cavity behind the rear wheel on the passenger side, and flowing into some empty area below the hatch floor to one side of the spare tire. I was planning to use the mirror of that empty area on the driver side for my amp rack - but it's really not much space. Fitting a DSP and finding 11 channels of amps that will all fit in about a 10" x 20" rectangle is... ambitious.

    Epiphany - lots of cars these days don't have a spare tire. "Hey, I could work in a pump/slime/plug emergency kit and ditch my spare!"

    First thought was to just make the box use half the tire space on the passenger side, and I'd have half the space on the other side. It's still an option, it just results in an odd-shape floor that I'd have to build a flat surface over - it basically wastes half the tire well below. So as soon as you start thinking about using that space for the sub box also...

    Second thought happens: I could have both a larger box and larger amp rack by 'glassing the spare tire well ALL the way across - then I need to mount the amp rack on top.
    If I go this route - yes, the sub itself is way on the passenger side and this is technically just one wall of the box, but I'm concerned about vibrations.

    I've inadvertently got a lifetime supply of CCF (anyone need any? ) - I thought one option might be to bond CCF to the sub box, then bond 1/2" birch ply to that. The downside to that is that I just added nearly an inch to the height of this stack that I'm trying to keep at stock-hatch height. I'm also not sure I'd trust CCF adhesive to stay bonded to wood over the long haul.

    Does anyone have any good suggestions for decoupling an amp rack?

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    Noob TheTodd's Avatar
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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

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    Not necessarily those exact ones but something similar?

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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    Yes - but I think the issues with those are they'd actually add more space than CCF and absorb less low frequency energy (I say that without knowing what they are made of).

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    Noob TheTodd's Avatar
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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    Aaaah... yeah. Didn’t think that all the way through I guess.

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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    Oh no, that actually made me think - those look like a bit like skateboard bushings, which come in different durometers (softness/hardness).
    Instead of decoupling the amp rack, maybe I could install the amps with bushings or rubber washers of a certain durometer, both below and above the mounting holes of the amp, so that the screw was really holding the bushings in place, and the bushings were holding the amp.
    Or maybe, both - a CCF layer and amp rack bonded to it, and then some rubber bushings to further isolate the amp from the rack.

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    Owner BigAl205's Avatar
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    Re: Amp rack sharing a surface with sub enclosure - decoupling?


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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    This is made for subwoofer boxes.... https://www.svsound.com/products/sou...olation-system
    It actually works super well. My SVS subwoofer box may violently shake but the surface where the box is sitting will not shake as much. It comes with 1/4"-20, 6 mm and 8 mm screws for mounting to the bottom of the subwoofer's enclosure.
    Some people use it for other purposes (under turntables or expensive CD players).
    It just works super well for those items because it's the right material/design. However it probably won't work for @geolemon's application because it's only bolted on one side (amp will be loose, not attached, not safe in a vehicle) and those are huge thick cylinders/balls.

    Maybe 4 or 8 horizontally placed springs attached to the amp's board might work(?)

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    Noob DubScientist's Avatar
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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    Here's another one for the hat:

    https://www.quietpc.com/acoustifeet

    They're adhesive backed pads. I use them on my external hard drives, my book shelf speakers, and on one of my home theater subs. They come in soft (Shore A 20) and firm (Shore A 30)

    And here's a chart of the Shore hardness scale:

    https://www.smooth-on.com/page/durom...ardness-scale/

    I also second Sorbothane. I bought a few 12" x 12" sheets to make isolation rings for my mid basses and mid ranges:

    https://www.isolateit.com/products/s...ea081fb8&_ss=r

    They might have other products that'll suit your application better.
    HU: Pioneer P99 RS
    Front stage: HAT L1 V2, L3s, L8SEs
    Subs: Image Dynamics IDQ15 D2 v2 in sealed 1.25 cu ft enclosure
    Amps: JL HD 600/4 for tweeters & midrange / JL 600/4 for midbasses (bridged) / JL HD750/1 for subs

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    Senior Member jrwalte's Avatar
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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    I like those SVS pads. Added them to my subwoofer and it helped a lot. Stopped the second story floor from vibrating and rattling things like my return vent.

    But they're meant to float on the surface you are isolating from the vibration source...so not sure how that would help in a car when your equipment needs to be mounted and not floating.

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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    The Sorbothane is interesting to think of - the feet are good ideas too, but all options obviously I'm going to end up spacing my amp rack up higher. So we'll see - I'll take some measurements and see if my height concerns are unfounded.

    I wonder how the Sorbothane would compare to my thought of using a layer of CCF... just make a sandwich with no hard parts... And thinking about that more, maybe a solid layer actually ISN'T best. Like imagine driving your car with four springs - now imagine driving it if it had a whole layer of springs, all connected. Would be stiff as a brick.

    So maybe those fancy feet (or maybe the cheap feet) would be good. I don't know if I have the weight - I'm not suspending the sub box, that will be solidly bolted down via the spare tire nut. So possibly that alone will actually brute-force damp the vibrations in that portion of the box - but wouldn't want to risk it.

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