Price

[Madmike2]

I have spent an hour or so going through posts and i cant seem to get a handle on size and such. So here is a straight question.

Is it possible to have chip amps 'inside' sealed enclosures to make active speakers or do they have to be exposed somewhere.

 

[Russ White]

Sure, the amp itself can be inside a sealed enclosure, but you will want to make sure you have adequate heatsinking. One good way to do this is to make the heatsink itegral with your design is a way that the fins are exposed to the outside air.

 

[Madmike2]

I can make cutsto fit it. the enclosures are already made. I am trying to get back money from my initial exburant spending spree. I have read all over this forum that chip amps are as good as any store bought SS amps available until you get into the big buck stuff. SO if i can pawn off some stuff for cash back so i can DEQX then that would be fantastic.

I want to go active on all the speakers, that way all i need outside is a pre amp and crossover, which i seem to already have

top part is morel MW166 with a Hi-Vi ribbon RT8II and then there is a middle 8 inch for mid bass in its own enclosure. and the bottoms are a pair of enclosures containing 2 D10.8 10 inch subs each. Which i will obviously have to plate amp. But will the chip amps produce enough juice for the mid bass ? I know it will be enough for midrange and tweeter.

 

[cowanrg]

i had at one time thought of making a small box that would house the amp and power supply. this box would attach to the back of a speaker, over the speaker terminals, thus not altering the volume of the speaker, and allowing it to be free to "breathe".

if you had an enclosure that was slim enough, it wouldnt change the overall depth of the speaker much at all.

or, if you wanna be super cool, build speaker stands with amps built in. a power cord comes out the bottom and little pig-tail leads come out at the top and connect to the speaker. you would have plenty of real estate to build whatever inside the stand, not to mention sufficient cooling.

 

[Madmike2]

Unfortunately i wont have stands. Although that sounds like a great idea. I have three enclosures that stack. That way if something is off or badly built i only have to do a new design for that enclosure. Strictly modular baby. Bass Mid-bass Mid-High.

 

[Mr Evil]

Amps inside the enclosure are ideal, since you can then use extremely short wires to the speakers, effectively eliminating any effects they may have.

 

[G4ME]

Just as long as you have decent signal wires, personally I would go with speaker wire instead of expensive long runs of RCAs

 

[carlosfm]

Amps inside the enclosure are ideal, since you can then use extremely short wires to the speakers, effectively eliminating any effects they may have.

Right.
And you can even avoid speaker terminals, which are a bunch of unuseless metal.
The amp can be on an isolated compartment, located on the bottom of the speaker.
The wiring is internal, soldered on the amp and on the drive units.

Just as long as you have decent signal wires, personally I would go with speaker wire instead of expensive long runs of RCAs

As long as you have a low output impedance preamp, you don't need expensive interconnects.
No, let me put it this way: you don't need expensive interconnects.
It is much better to have as short as possible speaker cables.

 

[Madmike2]

You guys are forgetting about heat ?

I wont be using 5 watt amps guys. the top amp for the mid highs is at least 25 watts the mid bass surely has to be more then that for any reasonable amount of output and 'oooomph' and the plate amps are like 350 for the subs.

higher frequencies require less power i know but still, 5 watts wont really do it for me. SO attaching them to the speaker itslef in a sealed enclosure just dosent seem practical to dumb old me .

 

[Mr Evil]

It's quite practical to use a heatsink as part of or even all of one side of the box. Or, as has been mentioned already, put all the electronics in a self-contained enclosure attached to the speaker enclosure.

 

[carlosfm]

higher frequencies require less power i know but still, 5 watts wont really do it for me. SO attaching them to the speaker itslef in a sealed enclosure just dosent seem practical to dumb old me .

You can have the heatsinks on the outside (exposed).

 

[Variac]

Yuup! and many plate amps have heatsink fins on the outside. Apez jr has some at decent prices

 

[Madmike2]

Ya plate amp isnt a problem. I know how they work i was misunderstanding you all i guess. I envisioned these little chip amps all bottled up inside my enclosures dying from a lack of fresh cool air

 

[Mr Evil]

...I envisioned these little chip amps all bottled up inside my enclosures dying from a lack of fresh cool air

If the power is low enough then it is possible to do that. In fact the speakers I last built have no particular external heatsinking, but the measured temperature is well within maximum limits. You need to do careful thermal resistance calculations of course.

 

[cowanrg]

i shouldnt see it as a problem if they had a heatsink external to the speaker, like a plate amp has or something.

but, i would dare say, even a chip amp in a sealed speaker box, sitting in the cabinet would be "ok". it will still have convection cooling because its still in free air. and the drivers should create a bit of turbulance. however, the air will heat up eventually and create less of a convection effect.

 

[DC Dave]

If you are worried about heat, why not make some small plate amps using the LM3875 (or whatever chip you want) and mount the plates to the back of the box.

The biggest component will be the transformer which can be mounted off the plate in the box on the bottom. This way you can mount your power and input jacks to the bottom of the plate and have room for a suitable heatsink above them that is exposed to the outside air.

A 1/8" thick plate 4" x 5" should work with a 4" square 3/4" thick heatsink mounted to it.