Can one sit amplifier on top of subwoofer? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 10 Old 03-04-2015, 03:35 PM - Thread Starter
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Can one sit amplifier on top of subwoofer?

I just received my XPA5. I am pretty limited on space unless I mount tv on the wall. My subs are big enough to sit the amp on top of them if possible. What's the verdict om this?

I'm not against wall mounting my tv. This could be just a temporary solution until I get it mounted. Only thing negative is I would have to cut new wire to all the speakers.
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post #2 of 10 Old 03-04-2015, 03:42 PM
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I think you would be fine , but just to be sure maybe you could place some dense foam under each leg on the amp to isolate the unit to some extent.I had my Behringer 2500 on top of my sub for almost two years without any adverse effects.
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post #3 of 10 Old 03-04-2015, 03:49 PM
 
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Personally I wouldn't do it. Vibrations and solder points doesn't mix.
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post #4 of 10 Old 03-04-2015, 08:08 PM - Thread Starter
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I have seen others out there sub amps on top of their passive subs. I figured those style amps are a little more rugged.
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post #5 of 10 Old 03-05-2015, 05:59 AM
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Good practice says don't put anything on top of any speaker cabinet. I follow that practice myself. I will say that my 75 lb subwoofer doesn't vibrate much and putting an amplifier on top of it would probably be OK but the concept bothers me. I think I might do it if I had to but I don't have to.
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post #6 of 10 Old 03-05-2015, 06:32 AM
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You should be fine. As long as either one of your subs is large enough to physically accommodate the amp properly. The weight damping on the Sub from the amp should minimize any large or even micro vibration effects on either unit's electronics. My biggest concern would be for the sub top to be protected as suggested earlier, both for isolation and heat transfer over time from the bottom of the amp to the sub top surface.

Last edited by ClarkeBar; 03-05-2015 at 06:35 AM.
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post #7 of 10 Old 03-05-2015, 07:09 AM
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Can one sit amplifier on top of subwoofer?

People have been placing both tube and solid-state amplifiers on top of speaker cabinets for over 50 years without problems; and a good many operating at higher SPL's than you'll likely be using at home. Least someone point out the below pictures are of instrument amplifiers and not your subwoofer, an amplifier doesn't know if it's amplifying a CD/DVD or an instrument. The lowest note for a 5 or 6 string bass guitar with standard tuning is 30.868 Hz and the lowest organ note is 8.18 Hz.

If you pause and think for a moment, your subwoofer probably has an amplifier screwed to the side of the cabinet without any special insulation or cushioning other than a very thin rubber gasket to seal the cabinet. The worst that might happen is some damage to the cabinet finish via heat from the amplifier or marking from the rubber feet of the amplifier.
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post #8 of 10 Old 03-05-2015, 07:51 AM
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Quote:
Originally Posted by b curry View Post
Can one sit amplifier on top of subwoofer?

People have been placing both tube and solid-state amplifiers on top of speaker cabinets for over 50 years without problems; and a good many operating at higher SPL's than you'll likely be using at home. Least someone point out the below pictures are of instrument amplifiers and not your subwoofer, an amplifier doesn't know if it's amplifying a CD/DVD or an instrument. The lowest note for a 5 or 6 string bass guitar with standard tuning is 30.868 Hz and the lowest organ note is 8.18 Hz.

If you pause and think for a moment, your subwoofer probably has an amplifier screwed to the side of the cabinet without any special insulation or cushioning other than a very thin rubber gasket to seal the cabinet. The worst that might happen is some damage to the cabinet finish via heat from the amplifier or marking from the rubber feet of the amplifier.
but those bass guitar speakers are almost universally rolling off very sharply below say about 60 Hz (possibly the vintage era rolls off higher, and for sure it starts compressing far sooner than modern bass cabs (those were guitar speakers with an XMax of a very few mm . . . . ..) So what will happen with a speaker that is actually responding down to 30 or 20 Hz is poorly predicted based on amps sitting on bass guitar speakers. I wouldn't be terribly surprised to hear that even a typical commercial bass guitar cab shook off one of the new era of lightweight bass amps, if it was sitting on a "spongy" stage, played at high levels.

Frequent, and more knowledgeable than me, contributor Bill Fitzmaurice would, I think, suggest that a decently designed and built sub won't have much vibration in the speaker panels, so from that perspective not a big deal. But it depends on where you put the speaker. On a concrete-on-dirt slab, it'll sit still. In my living room, where the suspended floor is mightily flexible (a hard step in the dining room can be felt at the couch 15 or more feet away), the output of the sub (not it's cab) shakes the floor, which shakes the sub, since the sub is sitting on the floor. Even at my relatively low listening levels, it occasionally bucks off anything lightweight I put on it (like books or CDs etc), but I'd guess a 20 pound or more amp would sit still just fine. I wouldn't put a $10,000 sculpture on top of it, whatever the sculpture's weight, but the amp isn't likely to destroy its own value if it slips a quarter inch off one edge during, ummm, spirited playback.
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post #9 of 10 Old 03-05-2015, 10:33 AM
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Quote:
Originally Posted by JHAz View Post
but those bass guitar speakers are almost universally rolling off very sharply below say about 60 Hz (possibly the vintage era rolls off higher, and for sure it starts compressing far sooner than modern bass cabs (those were guitar speakers with an XMax of a very few mm . . . . ..) So what will happen with a speaker that is actually responding down to 30 or 20 Hz is poorly predicted based on amps sitting on bass guitar speakers. I wouldn't be terribly surprised to hear that even a typical commercial bass guitar cab shook off one of the new era of lightweight bass amps, if it was sitting on a "spongy" stage, played at high levels.
Maybe you missed the part where I referenced frequencies?

X-Max is but one parameter to consider and can be offset by the total number of drivers or the diameter of the driver(s) or both. Volume displacement, Vd, is necessary to create high SPL low frequency output; you have to move large quantities of air and that's where larger X-Max drivers facilitate smaller cabinets and WAF with modern subwoofers. There are other solutions to the same problem. As to the roll off and compression you speak of I can only say that I guess you've never experienced the thunder of a Hammond B-3 playing live in the days before arena based concerts. I've never had the pleasure of playing on a "spongy" stage before so, no comment here.

Quote:
Originally Posted by JHAz View Post
Frequent, and more knowledgeable than me, contributor Bill Fitzmaurice would, I think, suggest that a decently designed and built sub won't have much vibration in the speaker panels, so from that perspective not a big deal. But it depends on where you put the speaker. On a concrete-on-dirt slab, it'll sit still. In my living room, where the suspended floor is mightily flexible (a hard step in the dining room can be felt at the couch 15 or more feet away), the output of the sub (not it's cab) shakes the floor, which shakes the sub, since the sub is sitting on the floor. Even at my relatively low listening levels, it occasionally bucks off anything lightweight I put on it (like books or CDs etc), but I'd guess a 20 pound or more amp would sit still just fine. I wouldn't put a $10,000 sculpture on top of it, whatever the sculpture's weight, but the amp isn't likely to destroy its own value if it slips a quarter inch off one edge during, ummm, spirited playback.
Sounds like you need to invest in a new floor. I've a 700 lbs. Yamaha piano setting on my floor and there's no movement of the floor at all.

Back to the OP, I still think you're ok to set your amplifier on the sub cabinet.
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post #10 of 10 Old 03-05-2015, 02:19 PM - Thread Starter
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Originally Posted by ClarkeBar View Post
You should be fine. As long as either one of your subs is large enough to physically accommodate the amp properly. The weight damping on the Sub from the amp should minimize any large or even micro vibration effects on either unit's electronics. My biggest concern would be for the sub top to be protected as suggested earlier, both for isolation and heat transfer over time from the bottom of the amp to the sub top surface.
The sub is a 200lb JTR Cap S2, so it should support 80lbs pretty easy I would assume. I would definitely put some type of isolator pad on top of the sub.
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