Muffling the X32 Fan

Mitigating the noisome pestilence of the Behringer X32's fan

I bought my Behringer X32 in April 2012, and its fan sound had never bubbled up into my consciousness until March 2016.  I explain this as a matter of improvements to the noise floor of my studio. Since 2012, I have installed 1/2-inch (12mm) thick inner glass panes to reduce the intrusion of noise (birds, lawnmowers) into the studio, and I moved the Mac Pro into a closet that’s 7 feet away from my mix position. 

 

Concurrently with those improvements, I became aware of a distinct whine from the X32 when the room temperature approached 80 degrees Fahrenheit (27-C).  At initial power on, and when the room temperature stayed at 75-F, the fan speed stayed down, and the whine was below my threshold of awareness. But as things heated up, it became annoying.  I measured the case temperature with my laser sensor, and used a measurement microphone with the X32’s RTA to verify what I was hearing. 

 

The hottest part of the case is near the top just behind the graphic display. When that spot is 84-F or more, the fan speed increases, and a 520-hz whine ensues. That pitch is just a little flat of the C above middle C, and really bugged me!  After some directional sleuthing, I was able to confirm that the primary direction of the whine is upward through the top the X32. 

 

When I wrote to Behringer tech support, the friendly reply recommended that I clean the fan with some compressed air.  I did that, but there was no dust anywhere on the fan. Later, when I opened the case, I was pleasantly surprised to find that there was no dust inside either.  Their next recommendation was to send the unit to them.  Although I still have the original shipping box, my out-of-warranty situation compelled me to consider how much I was willing to spend to fix a soft flat C whine.  The answer is $10. 

 

First, I tried the free option. I cut a 6-inch diameter hole in the wooden support panel under the X32.  The theory was that the improved airflow would reduce heat buildup within the box and allow the fan to stay in its low RPM range.  That new hole didn’t change anything at all.  On a side note, the fan is quite a high-specification device. It’s a 120mm, 24-volt part that’s rated at 60,000 hours.  While 12-volt 120mm fans are readily available, 24-volt fans are rare. It clearly was time to get inside the box. **

 

For those that don’t know me, I’ve had my hands in quite a few machines over the years.  Before I became a data networking consultant, I was a computer technician in the Wall St area for 7 years. Outside of the data center, in one of my favorite mechanical projects, I built a 350 cubic inch Chevy V8 engine, installed it in a 1974 Datsun 260Z 2+2, and built several specialized circuits to integrate it into the car’s tachometer, temperature gauge, etc. I have also made other specialized circuits and cables for cars and homes.  My resume is available upon request. For this problem, nothing had to be invented. Moreover, the X32 is easy to open, and beautifully laid out inside. I decided to go for it. 

 

For $9.99, a one square foot piece of GTMAT Quadro sound deadening material can be had from the fine folks in Hutto, Texas. You can find it on eBay. The Quadro product is a four-layer design with a 0.004-inch (0.1mm) aluminum sandwiched between thick (and sticky) butyl 0.060-inch (1.5mm) rubber, supplemented by a top layer of 3/16 (5mm) dense closed-cell foam.  It’s a very effective implementation of constrained layer and mass loading sound deadening concepts. 

 

As you can see in the cell phone pictures at the left that were never intended for publication, I made a paper template of the doghouse that encloses the fan.  After adding a suitable gap at the boundary of each paper piece, a single piece of the Quadro material was cut to match.  Keep in mind, the nuts that hold the doghouse in place are 5.5mm.  Most kits don’t have that size, and a socket or nut driver with that size is essential to prevent foul language and blood pressure spikes. 

 

There’s good clearance between the X32 circuit boards and the Quadro after it’s applied to the doghouse, but that extra 3/4-inch strip of material pictured at the lower edge of the doghouse did not remain in the final implementation. Although there was no real pressure, that extra strip could touch the bottom of the circuit board above it, and there was nothing more than a neurotic benefit to having it there in the first place. If you do this mod, don’t do that.

 

I know you’re hoping for a dramatic ending with car chases, explosions, and a helicopter rescue. All I’ve got for you is silence. There’s a soft swoosh from the X32 if I allow the room temperature to get up to 80-F. Below that, I’ve estimated/measured [won’t bother to describe the process] the noise floor at my working/listening position to be 15dB SPL while the X32 is operating.  The sharp-eyed readers perusing the gallery pictures will see the 1-inch thick Owens-Corning 703 fiberglass pad below the X32. The pad is wrapped in polyester felt, and the feet of the X32 sit on 1/4-inch (6mm) thick plexiglass squares to ensure good spacing between the pad and the underside of the X32.

 

A new mixing table is under construction. The plan is to include symmetrical granite work surfaces, integrated speaker stands for the Adam A7X’s, and a home-built pair of Auratone knockoffs using 4.5-inch Celestion drivers.  The guests and I will be hearing the speakers, and not hearing the X32.

**

All disclaimers of responsibility apply.  I am merely reporting what I did. I am not recommending any specific action for you, and whatever you do to your X32 is completely your autonomous decision, and your responsibility. 

- Ted Gary of TedLand

June 25, 2016

 

 

 

 

 

 

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