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quieting a pro amp


tlag
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Hi, long-time reader, first-time poster here.

Have a Powersoft K10 DSP I've been really happy with for sub duty, *except* for the fan noise in my DIY TV stand/cabinet. Starts out ok, then gets annoyingly loud as things warm up.

The cabinet is 24" deep, 3/4" pine top/bottom, 1/2" Baltic ply sides, sliding 1/4" acrylic doors, and open back, inch or two from wall. So with the depth of the K10 and wires out back, not much free fore/aft room. But 11" interior height available.

Can hear it through the acrylic doors, so laminated glass doors might help?

Kinda thinking the overall best way to quiet this thing down would be to replace the squirrel-cage blower with some larger, quieter fans, meaning new enclosure or existing enclosure mod.

Has anyone done anything like this? I know about quiet PCs, but this is more of a higher-velocity/-pressure type system as is, so larger fans would need some ducting into the narrow tunnel. Can I even get there from here?

Would appreciate any experiences or insights; thanks!

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Someone who is familiar with or owns the amp can chime in here if necessary, but my first thought is that a rack-style amp like that is probably designed for ventilation at both the back and front. Your cabinet is probably not providing sufficient ventilation with the doors closed.  This might (depending on the amp design) cause the fans to ramp up a lot more than they would.

So one option (that you may not like) would be to remove the acrylic doors.  Though this might give a louder result, even with the fan speed staying lower, it should help the amp(s) and other equipment cool better.  Another option would be to install large/quiet rack fans in a strategic location to better circulate air within the cabinet.  This might take careful observation of the airflow and experimentation to get right.  And of course, I don't know how much the amp fans are responding to temperature.

Keeping electronics cool is always a good idea when you've spent a lot of money on them as heat is one of the primary factors that shortens electronics lifespan.

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I'm not 100% sure about the cooling system in the K line, as the radial fans don't give a great insight on air flow, but if you took those out and mounted a few 80mm fans to the heatsinks (with the fans blowing air up), leaving the top panel off, or better: making cut outs for the fans, the cooling would likely be better and very quiet. If you don't want to cut holes into the top panel, make something out of acrylic for example. That guides the cold air through the components and the hot air ventilates through the fans in the top.

Keep in mind that this solution will require additional dust filters at any point where air can be sucked into the amp (like the holes in the back after removing the og fans).

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Funnily, net noise level at listening position is roughly equivalent, doors open vs. closed, slower vs. faster fan. Probably subjectively a bit worse open, as there's higher-frequency content. I think the equipment's happy enough with doors closed, as average power level isn't high at all, and the fan never gets nearly as fast as it does right at power-on. The conservatively-programmed thermal cutoff has never tripped. Used to use a 1RU fan plate/controller with remote probe which showed max. cabinet ambient to be maybe 100F or so. The little 40mm fans were noisy and useless in the cabinet, though, open or closed.

But SME, you're right, it's probably well worth trying some bigger fans to flow the whole cabinet before elective surgery on the amp.

peniku8, it's been a while since I cracked the case, but provided there's some access to the cooling path from the top, that sounds like a low-impact way to proceed as well.

Hmm... why not both? :)

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I'm not a fan of operating long-term with the chassis open.  The chassis may establish necessary air currents for certain components.  There's also the risk of foreign objects getting in and shorting things.  And also if something goes *poof*, the chassis makes it much less likely that your house will catch fire.

 

Good luck to you whatever you decide.

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8 minutes ago, SME said:

I'm not a fan of operating long-term with the chassis open.  The chassis may establish necessary air currents for certain components.  There's also the risk of foreign objects getting in and shorting things.  And also if something goes *poof*, the chassis makes it much less likely that your house will catch fire.

 

Good luck to you whatever you decide.

That's why I suggested making a new top plate if he doesn't want to cut to original one. The layout of the heatsinks make cooling like that really easy and efficient. The fans just need to touch the fins to turn the heatsinks into closed-off paths for the airflow. If theres too much of a gap, the fans will draw air from the sides and cooling won't be efficient.

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The K10 seems to require quite strong front to back airflow directed  past the components that generate heat.  The best solution would be to relocate the amplifier and run cables.  Or perhaps  removing the stock fans and constructing some kind of manifold that pulls air through the original flow path but using large low RPM fans.   However as this this amp has high 2nd hand value you might be best just replacing it with an amp thats intrinsicly quiet.  Speaker power has been previously reported to be quiet and offers comparable output power

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Unfortunately, no easy location to which to relocate amp. And definitely using the DSP for parametric and shelving EQ, which Speaker Power doesn't seem to offer.

Have confirmed cabinet interior remains room temp even as fan spools up audibly several minutes after power up with no input. So simply venting the cabinet wouldn't help much at idle and low power.

Thinking low-hanging fruit is to replace acrylic door with laminated glass. Supposed to be worth maybe 5-10dB attenuation.

Next is probably to fab a new top, maybe sloped, with axial fans venting toward rear, existing fan outlets taped off. Not gonna be pretty, but hopefully effective.

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