Making your equipment quieter using quieter fans and other methods

Of course it's always nice to have a separate equipment room off of the control booth in a recording studio, but we don't always have that luxury. Here are a few suggestions you might try. Proceed at your own risk. You will violate all kinds of warranties when you attempt these, and of course, your mileage may vary.

The fan that came in my Blue/white G3 Macintosh is Delta Electronics, Sensflow, WFC1212B (600-5914), 12 VDC, 0.44A.

I put the G3 in a Marathon rack, which came with the following fan. Sunon, KD1212PTS1-6A, 12VDC, 5.4W.

Marathon says they put in NMB Technologies, 4710NL-04W-B30, 80 CFM, 35 dBA.

I felt that the fan was too loud, so I searched for a quieter fan.

I replaced this fan with NMB Technologies, 4710NL-04W-B10 D00 , 50 CFM, 25 dBA. I bought this fan from Newark Electronics.

It is much quieter, and the fan output temperature is between 80 and 85 degrees F. If you try to cram extra hard drives or a CD-R in addition to the CD-ROM, you might need the original fan. The more heat-producing stuff you cram in the computer, the bigger fan you need.

The fine folks at Marathon Computer helped me with this "unauthorized" project. I am very pleased with the results and thank them for their unofficial support.

Another alternative is to remove the fan altogether. This will not be easy if the fan is built into the power supply. Then attach a flexible hose to the place on the computer where the air exhausts. You can use the kind of hose used to vent clothes dryers or to vent a bathroom fan. The hose must be attached securely to the computer. You might find a sheet metal flange that fits the tubing that can be attached to the computer case. Or you could use a lot of duct tape. Run the tubing into another room and put a fan in that end of the tube. Make sure the fan is pulling the air through the computer, then through the hose. You could use a 120V fan and remote the power to the same power strip that controls your computer. This fan will need to have a larger flow capacity (100 CFM or larger, (Radio Shack 900-2520)) than the one you removed from the computer. This is because you are pulling more air. The best way to tell if the fan is pulling enough air is to measure the air as it exhausts the computer case. Check the temperature with the old fan in place, and then check it with the new fan/hose combination. Check the computer with the hard disk spinning fast like recording or playing a large audio or video file. This will check it in the extreme heat conditions. I have found my fan output temperature to be around 80 to 85 degrees F. 90 degrees is fairly hot, and over 100 degrees F would be really bad. Make sure you check the temperature at the computer, and not at the end of the hose. The air will cool off as it travels through the hose.

You could build a box to put your computer and other noisy equipment in. I built mine out of dense 3/4-inch particleboard (MDF - Medium Density Fiberboard). You could make it out of plywood, but the denser the material, the more sound is trapped inside. Brick would be very nice, but it's not as easy to work with, and I wanted to be able to move the box if I move. Sheetrock (drywall) is great too, but is gets a little messy to work with. The dense particleboard has really fine particles. If it weighs twice as much or more than the same size piece of plywood, then you have the good stuff. It comes in 4-foot by 8-foot sheets and takes at least two people to carry it.

Make sure your box is large enough to hold your computer and other gear. Allow for extra room around the equipment for air circulation and cable space.

I put a 4.7" 120 VAC fan in the box to keep the air flowing. I later replaced it with a 80 CFM fan that runs on 12V DC. It's the one that originally came in the Marathon rack. I'm giving it 9 VDC to make it run slower and quieter. (You can do this with DC fans. AC fans must run at the rated voltage. You have to change the frequency of the AC to make them run slower.) The inside temperature is between 72 and 80 degrees. The air is pulled from the large cavity in the box by the fan pulling the air up vertically. The air then goes across a short wide cavity across the top of the box. Thus the fan is about three feet away from the room, which helps to buffer the fan sound. The air intake is at the bottom of the same end of the box. I use the air intake to pass cables into the box. You could always use the hose and remote fan trick also.

Here is the front of my Quiet Box. Notice the Indoor/Outdoor digital thermometer above the case, next to the CD/Cassette unit. I put the "outdoor" probe inside the Quiet Box with the computer fan blowing on it. This way I can see the room temperature and the computer temperature at any time. It also shows the humidity in the room, which I control with a dehumidifier and a humidifier.

Here is the front shelf that is in front of the fan tunnel. The shelf is 3 1/2" tall and 14" deep. My CD-R sits on this shelf. The SCSI cable goes down through a hole just behind the CD-R.

Here is the back with the cover on. Note the straps I grab and pull to open the case. The cover is just force-fit. The carpet covering has plenty of friction.

Here is the back side with the cover open.

Here is the end with the air inlets and the air outlet. The inlets are both 1 1/2" by 6 1/2". The air outlet is 6" by 3".

Here is a view of the inside of the air intake. A panel makes the air go up vertically before it enters the case. This helps keep sounds from passing through the opening. The cables pass through the air intake opening.

A view of the insides.

The fan is mounted horizontally to blow the air straight up into the fan tunnel that runs across the back of the case. The fan tunnel is 3 1/2' tall and about 9' wide.

I had my box carpet covered (for under $100) by a local speaker cabinet builder. It's about three feet long and about two feet high and two feet deep. The removable cover is press fit into one side.


Quiet PC

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Gary Stadler's drawing

Erik Forsberg's home-made box

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