Designing soundproof cabinet for loud amplifiers

[Trdat]

I'm in tuned enough about soundproofing, general STC rating basics on how sound travels and how to attenuate sound.

Unfortunately, I bought a very cheap Chinese amp which runs two fans full time. I want to make a small soundproof cabinet but what I am confused about is if make a hole and put a fan on the cabinet wouldn't the sound leak from that air hole?

I mean what's the point of a soundproof cabinet if its not totally sealed...? How do people make soundproof cabinets if a fan is needed.

 

[Vini darko]

I'm in tuned enough about soundproofing, general STC rating basics on how sound travels and how to attenuate sound.

Unfortunately, I bought a very cheap Chinese amp which runs two fans full time. I want to make a small soundproof cabinet but what I am confused about is if make a hole and put a fan on the cabinet wouldn't the sound leak from that air hole?

I mean what's the point of a soundproof cabinet if its not totally sealed...? How do people make soundproof cabinets if a fan is needed.

Might it not be cheaper and easier to either get quieter fans or just chuck a resistor in line and slow them down?
Edit : If a box is prefered. A basic T line at the back may damp noise and allow for air flow.

 

[solderdude]

I'm in tuned enough about soundproofing, general STC rating basics on how sound travels and how to attenuate sound.

Unfortunately, I bought a very cheap Chinese amp which runs two fans full time. I want to make a small soundproof cabinet but what I am confused about is if make a hole and put a fan on the cabinet wouldn't the sound leak from that air hole?

I mean what's the point of a soundproof cabinet if its not totally sealed...? How do people make soundproof cabinets if a fan is needed.

In my previous home I had a dedicated listening room that resonated at 50Hz The amps that hummed I placed in the adjacent room. Just drilled holes in the wall for that and ran cables through them.

 

[Trdat]

Might it not be cheaper and easier to either get quieter fans or just chuck a resistor in line and slow them down?

Lol! That did cross my mind but not sure how to do it. But I am sure I can find someone who can help me.

Its a 400watt PA amp, I use it for front left right YouTube watching so it shouldn't get too hot. I was considering just disconnecting the fans but don't want to take the risk.

What do you recommend? Would a different fan make that much difference? Or would it be better to just slow them down? They are extremely loud and it seems its because of there speed but not too sure.

 

[Trdat]

In my previous home I had a dedicated listening room that resonated at 50Hz The amps that hummed I placed in the adjacent room. Just drilled holes in the wall for that and ran cables through them.

Unfortunately I don't have that luxury, matchbox apartment with all my gear 3 meters in front with my TV. I will definitely, have a separate room in future for amplifiers and a separate listening room. Currently, I can hear my heater and computer, very faintly but its there, you want to quell the extra sound.

But this Chinese amp is loud!! Thanks for idea, I still thinking how I can manage that and the best so far is to put my fan orientated amps in my draws which works really well. But this amp can be heard from the open back.

I want to close the back of the draw but need a hole for the fan, and curious how hot it will get in a tiny draw with no much ventilation? And hazarding a guess that enough foam should alleviate most of the sound problem before it gets out of the hole....

 

[Vini darko]

Apologies for the crude quick sketch.

 

[pozz]

@RickSanchez mounted fans directly in his AV cabinet IIRC.

Perhaps you could look into replacing the fans in the amps. From experience with computers I'd say the main difference with aftermarket fans is that the spectrum of the noise is shifted lower, besides having better, quieter construction in general.

 

[Vini darko]

In order to know what would need to be done to slow the fans I would need to see the way they are connected. For quieter ones the PC world has many options.

 

[Trdat]

Apologies for the crude quick sketch.
View attachment 100480

So my understanding is that the sound is dampened through the maze it exists. Hence the length of the opening.

 

[Trdat]

In order to know what would need to be done to slow the fans I would need to see the way they are connected. For quieter ones the PC world has many options.

Well, the main thing is that it is possible so I can take it to the local guy(although I am DIY guy, work like this is really cheap where I live, might as well just get someone to do it) and see what can be done, and while I am at it and its open I can grab the size and find a quieter fan. Appreciate it!

 

[Vini darko]

Well, the main thing is that it is possible so I can take it to the local guy(although I am DIY guy, work like this is really cheap where I live, might as well just get someone to do it) and see what can be done, and while I am at it and its open I can grab the size and find a quieter fan. Appreciate it!

That sounds like the best option.

 

[Vini darko]

So my understanding is that the sound is dampened through the maze it exists. Hence the length of the opening.

Yes thats how it works. I called it a T line but it's a folded vent. My mistake (a real T line has no vent)

 

[Trdat]

Yes thats how it works. I called it a T line but it's a folded vent. My mistake (a real T line has no vent)

The space seems tight, and realistically my potential project will be small as well. Would that outlet be enough to ventilate the amp properly?

 

[RickSanchez]

As @pozz mentioned I went the route of external fans on my A/V cabinet which houses a bunch of fanless equipment that runs hot:

• https://www.audiosciencereview.com/...nt-racks-and-a-v-furniture.13100/#post-393179
• https://www.audiosciencereview.com/forum/index.php?threads/ac-infinity-cooling-fans.13424/

Lots of options on the fans from AC Infinity but the key is the Controller 8 thermostat. It controls multiple fans in multiple "zones" independently, which means only the fans that need to run will run. But it also allows you to set the temp thresholds for when the fans kick in. Admittedly the Airplate S5 fans that I have create a bit of background hum when they're on, but the top shelf of my cabinet (AVR + DVR) has to get pretty hot for the fans to kick on. And those S5s are still a lot quieter than most standard equipment fans. (The Aircom S8 fan I have for my old Harman Kardon amp is completely quiet; I can only hear it when no music is playing and I've got my ear to the fan.)

Both of my fans are set as exhaust fans, but you can also set up an airflow system with one fan as an intake and one as an exhaust.

 

[Berwhale]

Take a look at this example of PC power supply muffler and test results.... Fan Mufflers - Overclockers

In my PC I just use a decent Corsair PSU with a pretty quiet fan and lots of expensive, but very quiet Noctua case fans, I also use a PWM controller to slow them down and make them even quieter.

I have also replaced the 'screaming' 40mm Delta fan in a Cisco 24 port managed network switch with a Noctua equivalent to great effect. You might consider changing the fans in your cheap chinease amp. If it's got a 'fan grill' that is simply a bunch of holes stamped in the case, you may want to cut it out and replace it with a proper chrome wired grill (the sharp edges on stamped grills are a considerable source of fan noise).

Do you have a link to the amp you bought?

 

[Trdat]

As @pozz mentioned I went the route of external fans on my A/V cabinet which houses a bunch of fanless equipment that runs hot:

• https://www.audiosciencereview.com/...nt-racks-and-a-v-furniture.13100/#post-393179
• https://www.audiosciencereview.com/forum/index.php?threads/ac-infinity-cooling-fans.13424/

Lots of options on the fans from AC Infinity but the key is the Controller 8 thermostat. It controls multiple fans in multiple "zones" independently, which means only the fans that need to run will run. But it also allows you to set the temp thresholds for when the fans kick in. Admittedly the Airplate S5 fans that I have create a bit of background hum when they're on, but the top shelf of my cabinet (AVR + DVR) has to get pretty hot for the fans to kick on. And those S5s are still a lot quieter than most standard equipment fans. (The Aircom S8 fan I have for my old Harman Kardon amp is completely quiet; I can only hear it when no music is playing and I've got my ear to the fan.)

Both of my fans are set as exhaust fans, but you can also set up an airflow system with one fan as an intake and one as an exhaust.

Thanks for your input. This can be another option, in which I switch off internal fans and add two fans on the cabinet. But I need to be sure that the two fans in the cabinet will be quieter.

 

[Trdat]

Do you have a link to the amp you bought?

https://www.sinbosen.com/pid1828921...small-1U-stereo-digital-karaoke-amplifier.htm

Can you send me a picture of a proper chrome wire grill option? Your saying that this option will be quieter than the cheap fan in the amp...? I think its easy changing it, I can easily find an option that fits and the connection is the same as far as I know.

 

[Trdat]

Another question, today I just put the amp in my wooden cabinets(general) draw to check to see how much it attenuates sound(not bad there is potential) and how hot it gets. And of course without proper ventilation(there was a air hole at the back small one) it got pretty hot but I could put my hand on it so not extremely hot.

My question, is there any way I can add heat sinks and where would I put them? Can it just be on top of the aluminum case or it needs to be inside near the caps or power supply? There isn't much space inside but I thought ill ask anyway...

 

[Berwhale]

It looks like it already has decent chrome wire fan guards already...

*edit* Actually, I think this is the wrong photo, the picture on the page you linked to shows four internal 40mm fans...

No wonder it's loud!

The problem is that this is a 1U rackmount unit (1U = 1 3⁄4 inches or 44.45mm), so you can only fit a 40mm fan in there which means it has to run fast and loud to move enough air to cool what's inside. There are several approaches to mitigate the issue:

1. Replace the 40mm fan(s) with more expensive, quieter fans - I needed a 5V fan for my Cisco switch and used this one: Noctua NF-A4x20 5V, Premium Quiet Fan, 3-Pin, 5V Version (40x20mm, Brown): Amazon.co.uk: Computers & Accessories

2. Put a bigger, slower, and therefore quieter fan somewhere else on the case. For example, you could cut a 4" hole in the top of case with a tank cutter and mount a 120mm fan on top. This is not usually an option for kit mounted in a rack

3. Remove the 40mm fans from inside the case and Mount a bigger fan (the bigger the better), on the outside of the case using fan adapters like this: 40mm to 80mm Fan Adapter Converter 2 sides alligned change mounting PC Modding | eBay

For all of the above options, you will need to find out the specs of the existing fans so you can match the airflow with what ever you replace them with.

 

[Berwhale]

Another question, today I just put the amp in my wooden cabinets(general) draw to check to see how much it attenuates sound(not bad there is potential) and how hot it gets. And of course without proper ventilation(there was a air hole at the back small one) it got pretty hot but I could put my hand on it so not extremely hot.

My question, is there any way I can add heat sinks and where would I put them? Can it just be on top of the aluminum case or it needs to be inside near the caps or power supply? There isn't much space inside but I thought ill ask anyway...

I would assume that there are sufficient heatsinks within the amp on the parts that matter. I would concentrate your efforts on maintaining airflow through the case and getting the hot air out of the draw (and cooler air in).