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AudioAcoustics

Serving the Acoustics Community Since 1994

Cross-Spectrum Acoustics Inc. offers Sound & Vibration Consulting Services

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Aug 25, 2009

During the summer between my junior and senior years in college, I stayed on campus to work at the MIT Acoustics and Vibration Laboratory. One of my friends had a fairly decent audio system which included a Sony ES-series CD changer. For various reasons he didn’t have time to pack up his stuff before leaving campus for the summer, so I held on to his stuff for a few weeks until he could come back to pick it up. He had a better CD player than I had (at the time I was using a Pioneer CLD-S201 combo player as CD player) so I installed his Sony unit into my stereo as the CD player and continued to use my Pioneer as a laserdisc player.

At the time I believed that, once you got above ~$100 price point, most CD players essentially sounded the same and while you probably could measure differences in performance from unit to unit, the differences were not likely to be audible. My experience that summer disabused me of that notion. One afternoon, I came into my dorm room and popped in the Lion King soundtrack (which I was very familiar with at that point) and laid town on my bed to relax a little. When the music came on, I literally jumped out of bed - I was hearing things on the CD that I hadn’t heard before. I did some further A/B testing (evening cajoling some friends into performing some double-blind tests) to demonstrated to myself that I was hearing differences. That was a real eye-opener for me. I had a similar experience recently when I upgraded from a first-gen iPod Nano to a 4th-gen iPod Classic and also realized they sound different.

This past Sunday, the Boston Audio Society hosted a presentation by Roy Gregory of Nordost, a manufacturer of high-end (meaning “very expensive”) power and interconnect cables. I, like many people in the field who come from technical backgrounds, dismissed claims from high-end cable manufacturers as complete lies designed only to separate fools from their money. I came to the meeting expecting to have a good laugh at Nordost’s expense.

Mr. Gregory put on a demonstration in the Goodwin’s High End large listening room where he played demo tracks through a high-end audio system (SACD transport and Verity Parisfal loudspeakers). The system at the start used the factory power cables and interconnects by MIT. He then substituted various cables, first playing a demo after replacing the power cables (same audio material), and then playing another demo after replacing the interconnects and speaker cables.

Demo room at Goodwin's High End

To my complete shock, I heard a difference! The biggest difference I heard was when Mr. Gregory replaced the power cables, but I also heard (or at least I think I heard, see below) minor differences when the interconnects and speaker cables where changed.

This was, to say the least, quite disturbing.

Now this wasn’t exactly a scientific experiment. First of all, the test was not blind, we could see the cables being changed. Furthermore, it took several minutes for the cables to be switched out, so aural memory plays a role here. Add in the fact that I wasn’t familiar with the source material and Mr. Gregory did his best to point out what we should be listening for (which I did my best to ignore) and what we have is a test that is anything but conclusive. Still, I expected to hear no differences during the demonstration which I figured would bias me to not hearing differences and yet I heard differences.

So what does that mean? Am I ready to go out and spend four-figures on audio cabling? Uh, no. But until I can subject myself to more proper testing, I’m probably not going to dismiss cable differences as casually as I have in the past. Now the actual explanations behind those differences is another matter….

I should mention that Nordost is sponsoring some research into the why’s and how’s of these audio differences with respect to their products. They passed out some material that showed some of the measurable differences between cables (which I won’t try to summarize here) and Mr. Gregory claimed that more rigorous research is ongoing with results that might be presented in an AES meeting. I can’t wait to read the paper.


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Aug 19, 2009

Before you read this entry, I would ask that you take a page from Carly Simon and please realize that this post is not about you. This post is based on 15 years of field experience and I’m not trying to denigrate or call out any particular client, I’m just trying to give a little perspective of one of the difficulties of being in the field that may not be readily apparent to non-acousticians. Thanks for your understanding and patronage!

Dear Valued Clients:

I have been truly blessed to work for great clients. You hire me to solve your problems (thanks!), you give me support, you listen to me, you pay me well, you may me promptly (most of the time); at times you’ve even fed me, housed me, and helped lug my equipment up stairs and across fields. I truly appreciate the opportunities you’ve given me and in return I do my best to solve your problems.

I do have a small nit to pick with some of you. Again, you pay me well to address your concerns and I can certainly understand that you (as the client) might want to observe my field work to ensure that I am properly addressing your concerns. That’s perfectly fine - when the cable guy comes to my home or the mechanic is working on my car, I also want to watch over their shoulders to make sure I get what I’m paying for. I get that, I really do.

However, when I am working in the field, it is often to collect sound and vibration data using various instruments (sound level meter, digital recorders, accelerometers, etc). You need to understand is that my equipment does not have the ability to discriminate between sounds that I want to measure, and accidental sounds that you may make the course of your observations. If I’m trying to make a background noise measurement per MassDEP requirements and you’re talking on your cellphone right next to the microphone, the noise-level data I’m collecting will not have anything to do with actual background levels. Instead, I will have accurate data about the sound levels from your half of the cellphone conversation. I can’t make sound insulation measurements while you’re moving furniture. Same goes for sneezing, asking me questions, walking on dried leaves, etc. In the same vein, if I’m trying to measure ambient vibration levels and you are walking around, all I’m measuring is the floor vibration caused by your footfalls.

If your activity contaminates my measurements, I am forced to either redo the measurement or (in cases when I can’t make new measurements) attempt to salvage what I can from the fouled data. This increases the time and effort required for the analysis. It also reduces the accuracy and usability of the data. In other words, it makes it harder for me to do what you’re paying me to do, and if may negatively affect the case I’m trying to build for you.

If you must observe my work, you are welcome to, as long as you do it quietly and peacefully. If you just have to take that important call, please go back to your office and let me do what I do best. I will be grateful, and you will be one step closer to getting your desired outcome.

Thank you for your patience and understanding.

Sincerely, Your Friendly Neighborhood Acoustical Consultant


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