June 21, 1997

School of Computer Science
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213

The Editor
P.O. Box 5529
Santa Fe, NM, 87502-5529

Dear Editor:

In the spirit of sharing inexpensive tweaks that drastically improve sound quality, we thought you might be interested in the wonderful tweak we discovered for the Cambridge SoundWorks-brand amplified speaker system.  We expect it is also applicable to other subwoofer/satellite systems.

As computer science graduate students, we spend considerable amounts of time at work in front of computer displays.  Many students in our department, including ourselves, use satellite/subwoofer systems such as the Cambridge for high quality music listening in this case. Typically, a satellite is placed on either side of the display to achieve a good near field stereo effect.

Being tweakers, we have done the obvious things to improve the sound, such as enhancing the active crossovers with polypropylene capacitors, improving the fill and stiffness of the subwoofer enclose, and Monster Cabling everything.

In an effort to improve imaging, one of us (Paul) decided to try to raise the satellites several inches from their normal desktop position so that they could fire horizontally.  Since no stands exist for this purpose, he had to improvise.  Filled soup cans did the trick nicely.  Imaging improved drastically - the whole sound-stage snapped into focus remarkably well.  Sure, it still wasn't the same as listening to my carefully position Acoustats at home, but it was a vast improvement.

Imaging and overall frequency response immediately improved with the new soup cans. On the Reiner recording of Scheherazade, the image of the orchestra just snapped into place, with each group clearly "visible" on the sound-stage. In addition, the mid-bass response of the system improved considerably. Cellos in the orchestra that were muddy before were clearly audible now. On the Columbia gold CD of Kind of Blue, the instrumental lines separated better than ever, with Coltrane's tone cutting through the rhythm section.

Since it worked so well for Paul's setup, I decided to try the soup can tweak myself.  In my setup, using the identical Cambridge Soundworks system, with the same prior tweaks applied, the effect was far less pronounced.  Intrigued, I investigated more thoroughly, and found that the only difference was the type of soup in the cans.  I borrowed Paul's soup cans and, sure enough, heard the same wonderful improvement that I had heard on Paul's system.

Being scientists in training, Paul and I decided to do a small measurement study of the effect of the contents of soup cans.  We conducted an informal A/B comparison study using eight kinds of food products packaged in standard sized soup cans.  The sample size was 17 randomly selected individuals from the 30 that responded to a request posted on our in-house Zephyr messaging system.

In each trial, the individual compared unopened  cans filled with the current food product selection to the default can, which was filled with distilled water (density 1g/ml), and rated the food product on a integer scale of 1 to 5, where 3 signified equivalence to the default can, while 1 and 2 meant the test can was
inferior and 4 and 5 indicated that the test can was superior. Neither the test subject, nor the tester knew which can contained the food product or what that product was.  Each individual judged each of the food products in this manner.

In each trial, the music played was the first 1.5 minutes of Boney M's Rah Rah Rasputin, at an average measured level of 70 dB (class A weighted) at the listener position of precisely 0.5 meters from the front of a Digital 21 inch display and equidistant from the satellite speakers, which were aimed directly at the listener position.  The following table summarizes our results:

Notice that there seem to be two sweet spots, one at ~0.80 g/ml and the other at 1.15 g/ml.  This clearly warrants further research. Variance seems to be all over the map, which is perhaps not surprising given the qualitative nature of audio.

We encourage your readers to experiment with food cans of different densities in order to find what sounds ideal to them.  We both have upgraded to cans of chocolate syrup.


Peter A. Dinda
Paul Placeway

ps. Please note that the opinions expressed in this letter are our own and do not express the opinions of CMU or SCS in any way.