If the enclosure is built and mounted properly, ie; it's sufficiently braced and bolted into the car, then I see no issue with mounting the amp to it.

Poorly made enclosures can flex enough to terminally shake an amp into fault (repaired more than I care to think about) but on a solid enclosure it's no worse than what it would see from ambient bass transmitted through the vehicle body and normal vibrations from the vehicles natural movement.

 

even a well built box that does not flex to the naked eye will still vibrate more than a separate mounting location in the car, you can't argue with physics. play your system and put your hand anywhere on the outside of your box, then put it on the floor the box is on and tell me if they feel the same. anything that is mounted to the box will not only get those vibrations but all of the normal ones from the car being in motion as well. amps are full of small electrical connections that can be broken. if you have no other choice i would at least use some kind of rubber spacing between the amp and box.

 

even a well built box that does not flex to the naked eye will still vibrate more than a separate mounting location in the car, you can't argue with physics. play your system and put your hand anywhere on the outside of your box, then put it on the floor the box is on and tell me if they feel the same. anything that is mounted to the box will not only get those vibrations but all of the normal ones from the car being in motion as well. amps are full of small electrical connections that can be broken. if you have no other choice i would at least use some kind of rubber spacing between the amp and box.

If your mirrors ain't shaken uU ' ve been taken

 

X2 ^^^^^^

I had talked with DB-R one time and he mentioned the same.

 

I'm redoing my Miata with the Audio Art stuff that I referenced in another thread. Anyway, currently in there I have a Q Logic 10" enclosure that I wrapped on three sides with 1/4 inch ply & installed with 4 90 degree brackets. I then attached my Xtant A4004 to the 1/4 inch ply. An MTX 250D is running the 10" Arc Audio 10D2 in that Q logic enclosure. I haven't had this in there for long but something is going on & maybe it's the vibrations from having that amp attached to the sub enclosure (basically). When I turn the music up & the sub hits...everything gets distorted & then it might make a high pitch sound through the speakers & it shuts down. It tries to power back up...but as the sub hits it craps out again. I am running, for now, a really crappy Pioneer head unit. Maybe I'll try getting that amp off of the enclosure & see if it helps. Does anyone think something else might be going on? The crappy HU may be to blame?

 

The amp is probably starting to suffer from fractured solder joints internally, it's very common on rca sockets, wiggle the rca connections on the amp while it's operating, it will be pretty obvious if that is the case.

 

I wouldnt mount the amp directly to the back of the box but maybe seperated with some nylon spacers or something to leave a space between bottom of amp and box...

but thinking about it more I am not going to do it. I have just seen boxes with compartments that were made to house amps and wondered if they had some kind of material for vibration in between

they make pads for a/c units to prevent vibrations from traveling into the building but they are not cheap...damping pads...but I am not going to risk all that.

 

I like the class AB amps for the components mounted on the sub box, prefer the class D amp on the seat back or mounted upside down from rear shelf

 

Vibration is bad for an amp, it all depends on how good the amp is. Lot of cheap amps today do not have the board screwed down, it hangs on the legs of the transistors. Some amps its all screwed down to the case and much less likely to fail.

Another thing is if you have to mount to a box, mount to the corners of the box they don't flex as much as the center of panels will. Build the box heavier or the amp mounting side thicker, etc. If you can mount amps someplace else, do it.

The previous 12s I had IB, they were quad 12s into the seat. I fit a kicker 700.5 between the four 12s and it just fit. I did have a brace up the baffle under the amp so it was strong there, but still it was similar to being mounted on a box being there in the middle of the baffle. I had no other place, I had to put it there. I did put isolators under it but they only do so much. Anyway it still works fine, I took it out and put 15s and different amps in, but I didn't like the idea of it being mounted like that since the quad 12s would shake the back of the car. For a box built right and not that much power I don't worry that much.

 

NEVER mount an amp to the back of enclosure. I also have came across quite a few amps that have failed due to being mounted to the enclosure. Even though many have gotten away with it (I have in the past) some have not. Id rather not risk any of my amps failing. Here is a pic of one of a current repair that may have been caused by mounting to an enclosure or lack of any mounting at all LOL .

 

As Therum said, you can do it, but I wouldn't - really not recommended.

Kelvin

 

It works best if you don't mount the box to the vehicle , hit railroad tracks around 35 mph and never pass up a chance to drive down dirt roads.

That's how I've been doing it for the last 25 years oke:

 

I've had amps mounted to my boxes before without issues. But I always build amp racks or mount them on the back of my seats now. Just as easy and a lot more peace of mind.

 

a possible serious death threat to an amp!

 

lol exactly! I am amazed at how many install places still do this

 

well, they can surely build it for u especially when u bought the amp from them! but with extra charges & a void warranty!

 

Oh man it looks just like it even the clips, I don't work on many pioneers. Have one a little class D and it works once in a while but most of the time it has more voltage on one rail iirc. Have to look up the IC and see what its doing that is far as I got before summer break lol. Most vibration issues I see are broken legs on the outputs sometimes rectifiers. Many cheap amps don't even mount the board it just hangs on the transistors.

 

I never have or ever will mount an amp to a sub box. Vibration will play hell on electronics.

 

If it's problematic to mount a car amp to the sub enclosure in an auto application because of vibration, why do pretty much all "indoor" (home theater and music) subwoofers have attached plate amplifiers?

 

Good point, but either their are design different (as soldering goes) and might have some type of isolators used to mount the board to the chassis. But thats just my dumb opinion,.

 

DONT DO IT. Unless you hate the amp. Most people think its cool or looks cool to mount an amp to the enclosure for what ever reason. No matter how well braced the box will still vibrate. I have stood (210lbs) on top of a sealed enclosure that was very small (-1cu ft) so no bracing was required and when I was on top it still vibrated objects that were placed on top of the enclosure.

 

I've built my share of home theater subs and all the plate amps I've used have the circuit board exposed to the inside of the box taking the full brunt of the back wave in addition to any enclosure vibration.

 

i guess "your share" is the same thing as "nearly all". good to know. it's a safe bet that the average car sub is seeing 500rms or more (and that number is growing every year - when i started eons ago 100rms to a sub was a lot and now subs laugh at it), just slightly more than a ht setup and what of the car vibrations?

 

All the home theater subs I've built have 300W or 500W amps. I select my drivers and enclosure design such that they don't really need any more power.

 

hooray!

 

so, if it's a small enclosure that has extra bracing, double-wall construction and mitered joints, and it's mounted extremely securely to the vehicle there shouldn't be an increase in failure percentages;/quote]

Very rare ^^^^

large enclosures with minimal bracing and single-wall construction with butted ends probably should not be used to mount an amp on.

The norm ^^^

 

so, if it's a small enclosure that has extra bracing, double-wall construction and mitered joints, and it's mounted extremely securely to the vehicle there shouldn't be an increase in failure percentages;/quote]

Very rare ^^^^


The norm ^^^

Well said. Also one person commented on it earlier. The plate amps found in home subs are designed as such. I would imagine precautions are taken to make sure that the amp does not fail due to parts falling out or cracked solder joints. I think that one of the biggest reasons for amp failure is indeed poor enclosure construction and mounting to the vehicle. Back in the day when I mounted my amps to the enclosure I didnt mount the enclosure itself to the car either. so it hung out back in the trunk of my 88 grand am. free to move and crash into whatever was in there. If you look at the picture you can see the cracked solder joints. But also take a look at the transformer windings. They have MINIMAL solder on them. While solder is not a good method of attaching heavy components like a transformer. But they could have put more there. I could see one of the windings comming loose and essentially blowing the amp up to the point where it wouldnt be cost effective to repair the amp. What I do to every amp that comes through is adding a few dabs of an adhesive (E3000) to the bottom of the transformer to help support it. To this one in perticular I removed the old solder and added enough new solder to enclose the hole. Also, when was the last time you hit a pothole in your house?

 

I'll bet you don't find a plate amp where the board is not mounted like many cheaper car amps, but I could be wrong. The plates I have seen the board is open so air pressure/waves should not affect it much, and without a power supply they are up to half the size of a car amp maybe without heavy transformers/inductors in the middle of the board. Lastly I've never seen a HT sub that would vibrate across the floor like many car boxes can, and note they are all built near square and pretty stout by a factory that can do it better. I've seen piles of dual sub boxes that vibrated nobody braces them for DIY except people into it. The last thing I want is extra weight in my car anyway, I use 3/4 ply unless I am laying the power to it and can't brace it well/etc. When I hear a difference I'll put mdf on it, but I rarely run big power. These kids with 600rms and more and home built boxes, they are amp killers.

 

it's not the air pressure, it's the vibration that is killing the amps.

if you've ever looked inside a Sparkomatic powered bass tube, it's a two channel chip amp running a DVC woofer and it's mounted inside the tube with the circuit board in the flow of the vent, unprotected and not really that well mounted, either.

the vibration that an amp mounted on an enclosure panel receives, is going to put momentum into the parts on the board, and set up vibrational modes in whatever frequencies the board itself is tuned to, because the board is a flexible piece that resonates at some frequencies more than others.

That's what is playing havoc with the solder joints, because as everybody knows, the solder is supposed to form the electrical junction between the board traces and the parts, not be the mechanical load bearing component!

With surface-mount technology, the loss of the leads and the greater contact area surface-wise makes it a much stronger, more reliable way to provide that load bearing component through the use of the solder, and amps that are designed this way are more durable over the long-term. I would guess that a lot of the failure rate in old school product came as a result of improper mounting and that would have been exacerbated by the sometimes lower quality of hand-soldering, although I have seen the case made that some wave-table product needed "touching up" so maybe it's variation in the parts to blame?

I don't buy the plate amp theory, I have a plate amp with the board barely mounted to the panel in perpendicular configuration, and I'm sure as I've seen plenty of plate amps with the same, that this configuration is superior in keeping vibration from affecting the parts on the board.

mounted on the flat, with risers, the board would act as a loading point for vibration to set up modal waves, but standing perpendicular to the loading inertia of the panel, the destructive forces aren't transmitted and the plate amp doesn't falter under vibrational stress.

I have a Kraco 8" tube that had so many hours on it the gain pot went bad and I replaced it. Its just an IC amp, I used it in rental cars and one of my own when I had no room for much else. The board was mounted 90 to the endcap, however that would be the only way they could have a cheap gain stick out the end. IIRC it was mostly mounted via an angle of aluminum that served as the heat sink. The port was under it and longer than the small board.

Not sure about SMD I never see the smaller thru hole have issues, what always breaks is the transistors on the sink or heavy parts like inductors and toroidals. In fact I would say heavy parts and the board moving from heavy parts and/or lack of mounting is the leading issues I have fixed in amps from vibration. Amps built the same way with the board screwed down better have fewer problems, newer amps with smaller components have fewer problems.

 

One other train of thought about HT subs is how often and for how long do you play them at the levels you play your car stereo. My guess is either your neighbors, the cops, or more than likely your spouse, LOL, will stop you well before you reach the time/intensity level that you subject your vehical amp to on a dailey basis.