Amp module inside of sub port?

J

Jack Arnott

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Jan 29, 2011
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Hey all, I have a project where I am doing a 12" sub, 600 watts/96db with two satellites. Either 6.5"+ .63", or 8" coaxial.
I have an amp module (Marani) to power all of this. I know that the convention is for the module to have it's own chamber, both for heat reasons, and for compression/expansion, so as not to rattle the components in the module. BUT, the module would fit very nicely in the port chamber. (Which is rectangular, and on one side of the box.) This would be helpful for several reasons.
1) Space, two birds with one stone.
2) Convenience, as it would be easier for me to have the controls on the side, instead of on the back where they traditionally go.
3) Cooling. It seems to me that in the port, the air is not compressed, but more just moving. This would cool the amp.
(This also seems to me to be the biggest potential for contention. As in, my thoughts about the air moving vs. being compressed.)
4) I know, I know, I would have to recalculate the port, for what is in there, but this seems minor. Unless having asymmetrical ingredients in the port would be a problem.

Thoughts? Regards, Jack
 
Re: Amp module inside of sub port?

Jack Arnott said:
1) Space, two birds with one stone.
2) Convenience, as it would be easier for me to have the controls on the side, instead of on the back where they traditionally go.
3) Cooling. It seems to me that in the port, the air is not compressed, but more just moving. This would cool the amp.
(This also seems to me to be the biggest potential for contention. As in, my thoughts about the air moving vs. being compressed.)
4) I know, I know, I would have to recalculate the port, for what is in there, but this seems minor. Unless having asymmetrical ingredients in the port would be a problem.
Click to expand...
Jack,

1) OK.
2) Good.
3) If the port is properly sized, the air in a port should not really have much of a net air flow, the slug of air should be moving back and forth, sucking back in any heat just expelled. Depending on the heat sink design of the amp, it may be better off in a vertical position completely exposed to the outside air (side or back mount) than in a "tunnel". SPL (and vibration) in the port would be similar to the inside of the cabinet at Fb.
4) The best port shape to eliminate turbulence (which is a good thing for amp and speaker cooling, but bad in terms of "port compression") is a symmetrical flared port, in other words, a partial restriction in the center of the port. You could possibly use your amp in the center of the port with "ramps" on either side.

A diagram of the specific Mariani module you are going to use would be helpful.
 
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Re: Amp module inside of sub port?

Art Welter said:
3) If the port is properly sized, the air in a port should not really have much of a net air flow, the slug of air should be moving back and forth, sucking back in any heat just expelled.
Click to expand...

Thanks Art, here is a link to the amp. http://www.marani-proaudio.com/dettprodotti-SP2SA2/95_71/eng/

Above is the only part I am not sure of. I realize there will be no net air flow, but won't the slug dissipate heat when it is outside the port, and gain heat when inside? (Isn't that the reasoning to the port fins on the JBL Eon?)

PS, just to be clear, the outer panel, heat sink, and connectors etc. would still be on the outside of the cabinet. The part inside the port would be the "guts".
 
Re: Amp module inside of sub port?

It seems like this discussion came up before, but maybe over at that other place.

As others have noted the air inside a port is stagnant so while it may wiggle back and forth it doesn't really move. A friend and design engineer at Peavey came up with a clever (patented) approach using two ports, where the port exhibited an asymmetrical resistance to air flow direction. By alternating this directional air flow bias between the two ports, a net "in" and net "out" air circulation can be established to move hot air out of the box.

Another technique, also requiring two ports, is to place one hi near the top of the cabinet, and the other low. Natural convection will cause hot air to exit via the high port, and draw cool air into the low port. The ports can be placed in opposite corners so there is always a hi and lo port for both vertical and horizontal speaker placement.

JR
 
Re: Amp module inside of sub port?

So if I am not dissipating any heat, is the converse true?
That I am not introducing any to the speaker chamber. (This would be enough of a win for me.)
 
Re: Amp module inside of sub port?

Jack Arnott said:
So if I am not dissipating any heat, is the converse true?
That I am not introducing any to the speaker chamber. (This would be enough of a win for me.)
Click to expand...
As JR points out, about half the heat would go in, half out, but since heat travels towards cooler air, the port would provide a better channel for getting rid of heat than in the speaker chamber.

That said, considering much of the heat of the amp is dissipated through the panel mounted on the outside of the cabinet, and the speaker produces approximately 90 times more heat per watt than the amp, from a heat standpoint the location is not very important, except the exposed amp "guts" will probably collect more dust in the port than inside the main chamber, and dust reduces heat exchange.
 
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