I want to transforming two vintage passive speakers, into active speakers.
To do so I intend to use:
My question
Both the Amp and the PSU will produce heat. And the inside of the speaker casing is completely filled with damping material. The PSU has a case to keep the damping material away from components. And I will make a case to protect the Amp too. But will this get too hot or not, since the speaker enclosure is air tight?
To do so I intend to use:
- Two Mono amplifiers (one for each speaker) producing 50 watts.
- An AC/DC PSU to drive amplifiers.
My question
Both the Amp and the PSU will produce heat. And the inside of the speaker casing is completely filled with damping material. The PSU has a case to keep the damping material away from components. And I will make a case to protect the Amp too. But will this get too hot or not, since the speaker enclosure is air tight?
- Does anyone have experience with building these two components in a fully/air closed speaker box?
- Can this be done, or do I need other precautions?
In a fully closed enclosure, the only practical means for heat removal is by conduction, no fans, pipes or radiators possible. However, if the heatsink is installed facing the outside, that would allow convection and radiation to subsequently take over.
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My speakers have 4 x 80W amps fitted. Under quiescent conditions they consume about 10-15 watts. This is sufficient to make the heatsinks feel slightly warm. If played at moderate volume, say 75db or so, then the heatsinks get noticeably warmer. If played at “party” levels >100db then the heatsinks get to hot to hold for more than about half a second. This is with heatsinks that are mounted externally, so you can see the fins on the back of the cabinet.
I use TDA7293, so class AB. I cannot recommend internal mounting only for this class of amplifier as the heat would just build up with only maybe a reflex port to vent the heat, or none.
A low power class D amp with an efficient SMPS might be a possibility, but the heat has to go somewhere eventually.
Pano has a thread that has been running for decades at this point that suggests that a couple of watts is really all the power you need for domestic listening, 10 watts is really rather loud on my system with 88db/W drivers in a small room, so a very low power solution might work for you.
I use TDA7293, so class AB. I cannot recommend internal mounting only for this class of amplifier as the heat would just build up with only maybe a reflex port to vent the heat, or none.
A low power class D amp with an efficient SMPS might be a possibility, but the heat has to go somewhere eventually.
Pano has a thread that has been running for decades at this point that suggests that a couple of watts is really all the power you need for domestic listening, 10 watts is really rather loud on my system with 88db/W drivers in a small room, so a very low power solution might work for you.
Unlikely given it isn't a sensible thing to do. As others have said a heatsink needs to be on the outside of a sealed speaker for it to work unless the cabinet is made of metal and can itself conduct heat and act as a heatsink. What material have you used for your round speakers?
It is unwise (and possibly dangerous) to place a heat generating source inside an airtight wood box filled with insulation. If the source dissipates 5 W of heat, maybe its ok... but 50 W makes me very uncomfortable.
Perhaps build the speaker with a false bottom. The electronics could go in the bottom with some ventilation holes. Viewed from the outside, the electronics would be completely hidden.
Perhaps build the speaker with a false bottom. The electronics could go in the bottom with some ventilation holes. Viewed from the outside, the electronics would be completely hidden.
If you want to stick with 50W amps, why not build all 4 amps into one chassis that just looks like a normal stereo and use 2 pair speaker wires?
No added clutter and joy of active speakers!
No added clutter and joy of active speakers!
I don't think there is need for heat concerns, with any kind of reasonable airspace around the plate amp.
Just keep some distance from your dampening material..
A giant SpeakerPower 6000w into 2 ohms requires 2 cu ft of airspace...you can bet that buggar puts out some heat!
No idea how to translate that into the airspace a couple of 50 watt-ers need, but can't imagine they need much.
I allocated about 10 L of airspace for the minidsp Pwr-Ice 250's I've used, 2x250 into 4 ohms. No issues, even with hard running.
All that said, I do not like plate amps anymore....they sound like a good idea, but end up being a pain in the butt...locking up the plateamp and the speaker they are used in, into a marriage that I often end up wanting to break up, ......either to alter the speaker or repurpose the plate amp.
Just keep some distance from your dampening material..
A giant SpeakerPower 6000w into 2 ohms requires 2 cu ft of airspace...you can bet that buggar puts out some heat!
No idea how to translate that into the airspace a couple of 50 watt-ers need, but can't imagine they need much.
I allocated about 10 L of airspace for the minidsp Pwr-Ice 250's I've used, 2x250 into 4 ohms. No issues, even with hard running.
All that said, I do not like plate amps anymore....they sound like a good idea, but end up being a pain in the butt...locking up the plateamp and the speaker they are used in, into a marriage that I often end up wanting to break up, ......either to alter the speaker or repurpose the plate amp.
Proper experimenting is recommended. I would dummy load the amp and measure how hot hot it might run under worst case conditions.
Dedicated poly stuffing should not burn.
Dedicated poly stuffing should not burn.
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1) What two components?
You did not give the model of the amp/psu or the heat radiating surface area of the drivers and enclosure. Amplifiers could be less than 50% efficient up to over 90%, big difference between potentially dissipating 5 watts or 25 watts of heat.
Big difference putting 25 watts of heat in a sphere of 1 liter or 10 liters.
2) To answer whether it could be done without roasting components depends on the amplifier's heat sinks, operating temperature range, quiescent draw, duty cycle of the music, and efficiency of the drivers- need more information.
That said, a vintage passive speaker would only have a single speaker cord entering it, installing an internal amp would require both AC and audio input cords entering- it would look less "vintage" than locating the amplifier & PSU externally.
Air tight enclosure is not that bad, wood is not a perfect insulator and surface is all of the cab surface, that helps.
Remember voice coil turns >95% power input into heat, which is more than what power amp dissipates, yet we mount speakers inside sealed enclosures all the time. 😎
But an inside wholly stuffed with fiberglass or similar is terrible.
As of:
Closest solution would be to cut a square opening in the back, say 10*10cm, cover it with a flat Aluminum sheet, and mount new power amp from inside. That way you have a minimalistic but functional heat sink with at least one face exposed.
You can paint that metal sheet black or brown, whatever matches your cabinet back.
Use 1.6-2 mm Aluminum.
Remember in any case you would at least need a 5*7 cm metal/plastic plate to mount input connector and mains cable, so enlarging it a little and turning it into a heat sink is a good compromise.
Remember voice coil turns >95% power input into heat, which is more than what power amp dissipates, yet we mount speakers inside sealed enclosures all the time. 😎
But an inside wholly stuffed with fiberglass or similar is terrible.
As of:
What you "want" is irrelevant, you can't beat Physics 😎
Closest solution would be to cut a square opening in the back, say 10*10cm, cover it with a flat Aluminum sheet, and mount new power amp from inside. That way you have a minimalistic but functional heat sink with at least one face exposed.
You can paint that metal sheet black or brown, whatever matches your cabinet back.
Use 1.6-2 mm Aluminum.
Remember in any case you would at least need a 5*7 cm metal/plastic plate to mount input connector and mains cable, so enlarging it a little and turning it into a heat sink is a good compromise.
I have put 500W in closed cabinets in PA applications.
As long as you can remove the heat, it's not to much of a big deal.
Although, ideally you already want to make two separate compartments to get everything nice and sealed.
But in a scenario that everything is closed up in a wooden cabinet, no I would not recommend doing that.
In most designs it's not to hard to come up with a solution to have a aluminium plate + heatsink on the back that looks totally out of place.
Other option is to find a nice high efficient Class-D amplifier.
I don't know what kind of speakers we are talking about, but in most home hifi applications, a few watts continues is already A LOT.
Use a 95% efficient class D amplifier and an efficient switching power supply to minimize the heat. Mount them on a metal plate that covers one interior wall of the speaker.