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

  1. Back To Top    #11
    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: Amp rack sharing a surface with sub enclosure - decoupling?

    Quote Originally Posted by DubScientist View Post
    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)
    These feet list an ideal weight amount which is really important. You can use any damping pad or foam or whatever product but if the durometer/stiffness doesn't match the weight of your amplifier, then it won't work very well.

    If you can, try to use a product that lists an ideal weight or a range of weights per isolation foot. Divide the amplifier's weight to 1/4 and that's how much weight each foot should be supporting.

    Quote Originally Posted by geolemon View Post
    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.
    This exactly!

    Here's another place to look:

    https://www.mcmaster.com/isolation-m.../height~1-2-1/
    Last edited by Justin Zazzi; 05-28-2021 at 07:53 PM.
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

  2. Back To Top    #12

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

    Well, I sure wouldn't arbitrarily select a vibration isolation material! That's a guarantee for failure.

    I think this topic is simultaneously easier and harder than it could/should be.

    First thing is first. Just to clarify, why are you trying to isolate vibration in a car? it's an impossible task! It's like trying to make a "good ground" in a car. People have dedicated their entire careers to the topic...

    That said, I think I would take the following approach:

    1. What vibration am I trying to isolate? There are two factors: frequency, and amplitude. This topic is "success criteria". Am I trying to isolate all vibration down to DC? or am I only at risk above 50 Hz? 500 Hz? And what kind of reduction do I need? 50%? 100%? I need to be realistic about what I *need*. Car amps are meant to handle vibration! So, with that in mind, what exactly are you trying to solve? Do you expect your mounting location to subject the amps to more vibration than they can handle? And the subwoofer is directly responsible for that vibration as opposed to the roads, engine, etc? It's REALLY important here to be specific as possible, or else the rest falls apart. (or you're just being qualitative, in which case any arbitrary solution is just fine because it's just a "feel good")

    2. Baseline. What's the existing vibration? You can do this with any dummy box you have laying around, or whatever your source of vibration. As with all things, "there's an app for that"! I use "accelerometer" for iphone (logo is the letter G with a blue background". You can mount the iphone where the amps will go using a cheap mount that securely sets the iphone in place. Heck, you can use rubber bands if it is direct-contact. Whatever the means, you can collect vibration data. This will give you a good sense of the frequencies you are subjected to, and the amplitude is 100% arbitrary since you are just looking for a % reduction.

    3. Material selection. Testing phase, you can use whatever mockup is needed. anti-vibration posts, springs, weatherstripping, etc etc etc. Re-mount to simulate the rack and re-measure.

    That will get your your anti-vibration material. After that, it's just construction and beer.

    I suspect you will get where you want to be by using layers of CCF and adhesive between the mounting surface. But it depends on the design (this would require flat-mounted amps, not vertical).

  3. Back To Top    #13

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

    One note on the "feel good". Back competing IASCA (2010 and 2011 I believe), I was leaving points on the table because my amps were not "fan cooled". Never mind that wasn't needed at all. I added an arbitrary fan with a speed control for ambient noise reduction and made a big deal about it in the presentation.

    It was a TOTAL feel good. Everything about it was rather stupid. But I got full points out of it for show, and no one could touch my install scores.

    Moral of the story is feel good can be OK, so long as it's appropriately known as such.

    --------------------

    But I suspect feel good is not what you are going for here. So I think you can go full-data on it, particularly since you probably already have the needed sensor in your pocket right now.

  4. Back To Top    #14

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

    Chris, have you checked out my latest install? If you are ditching your spare, it may give you ideas without wasting space, I didn't flatten any surface to install gear or raise my floor.

    Though I didn't install a 12W7 either....

  5. Back To Top    #15

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

    Not yet - but now I will!

    The original thought was yes - ditch the spare, use the space - 50% toward the sub box, 50% the amp rack.

    Original thought was to split that horizontally, since I really only need a 4" height for that. Use everything beneath it for sub airspace.
    That would require decoupling though.

    I think my new idea is to split it half and half vertically. I can then use the tire well bolt to hold the sub box in place.
    On the amp rack side, I thought I'd have wasted space below the rack in the well, but I think I have an idea for that -

    And if I didn't miscalculate, the three DLS CC amps and miniDSP C-DSP 8x12 (and power distribution) will fit in that half-space.

    I'll check out your tire well install now.

    Sent from my LM-G820 using Tapatalk

  6. Back To Top    #16

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

    ...or I won't lol
    Shoot me a link, if you don't mind. Not finding any build logs here or DIYMA.

    Except for the one thread you didn't start way back in '08 after cracking up the Civic.
    And it wasn't the trunk that caught my eye - but those KICKS! So good.

    Sent from my LM-G820 using Tapatalk

  7. Back To Top    #17

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

    went WAY simpler this time around

    https://www.caraudiojunkies.com/show...ht=whiterabbit

    But I never see anyone install a BOX under the spare tire well. Which is strange when you think about it since that's exactly what the OEMs are doing! It technically solves some of your issues.

    But perhaps more interesting is the cantilevered amp rack which, if feasible solves a couple of your concerns, specifically space efficiency and vibration resistance. May not work in your application, but worth considering.

    If you never saw the mazda, that one was pretty slick too. Same subwoofer, but I KEPT the spare because it had an ID of 15", so I made an AP enclosure in the tire well, then plunked the spare on top of it like a speaker grille. I had my cake and ate it too (but the amps had to go somewhere else, crammed under the dash above the steering column)

  8. Back To Top    #18

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

    That's very cool! I definitely love the way the well area turned out. Never would have thought "chalkboard paint". In your case, you are a bit more like my "plan B" - your amps are next to, not on the box. Yours are mounted to the car (and so cleanly - great job wire hiding).

    So here's the start of the sub box -
    It's actually going to be firing up into the hatch glass, but tucked into the cavity as much as possible - I want all my hatch space!

    So in the one photo I marked up - for this "ditch the spare" plan, I'll cut some of that wood away and frame and 'glass up the yellow area for the lower area of the box. Green is for amp rack. Red might be big enough for a tire pump/slime/patch kit.

    The other photo with the tape measure I took today - note the foam blocks that space the hatch floor up. Should be able to keep the floor about factory height. Did I say "I want all my hatch space" yet?

    Sent from my LM-G820 using Tapatalk

  9. Back To Top    #19

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

    Gotta be honest, i think a 12w7 is the wrong sub for the aesthetic application. I could see something smaller like a 10w7 or 8w7’s. Or flatter like a 13tw5. The foam blocks are a godsend for sure

    That foam looks super thick. If we ignore the sub for a moment, would ALL the electronics fit in the “wings” area around the spare and still let the floor fit at normal height?

  10. Back To Top    #20

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

    The foam is thick, because the Sport hatch has a center exit exhaust that the other models don't - that pushes the spare tire up, and with it the hatch floor. That makes it even more motivating to reclaim and reuse that wasted space, to me.

    The 12W7 isn't at all a choice based on cosmetics, it's the joy of surprising your passengers with the highest displacement (other than the 13w7, but I don't own one of those) sealed sub on the planet, on command - while having XBL^2-like BL and suspension consistency.

    I actually think that flange-less design looks much smoother than most. Sitting on top a 'glass waterfall, I think I can make it look good. I may even need to have an adapter, the W7 cutout is slightly smaller. I was planning on a nice surround-sized roll diameter matching rounded adapter, and likely the same shape roll-over at the top of the waterfall. Could create an art-deco look, even.

    What won't look as good are my GTi 12 or other standard subs - but that's ok when it's time to play with those.

    EDIT - Actually I was going to mention earlier-
    Part of my thinking with the original plan (box below, amp rack above) was that the sub itself is so remotely located away from where the actual amp rack is, and I was planning on a PVC "tunnel" to rigidly still anchor the box using the factory spare bolt hole, that it wouldn't quite be the same as building a rectangular box and mounting amps on a side wall, at any rate. But this plan to have the amps on one side, box on the other - that still allows me to anchor it rigidly, actually have an easier-to-build sub enclosure, and just inherently decouple them by truly having them separate.
    Last edited by geolemon; 06-05-2021 at 02:43 PM.

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