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Apr 03, 2004

A few months ago, I commented on Bose’s new Personalized Amplification System. Yesterday I attended a GBC-ASA meeting at Bose’s headquarters in Framingham, where a senior product manager explained the speaker development process and some of its features. The presentation was followed by a live performance by a seven-piece blues band using the system.

The talk was interesting, if not technical (anyone who has ever been to a Bose presentation knows they tend to be geared toward marketing). The speaker talked about the history of live music amplification, and some of the problems that have cropped up. Eventually, the state-of-the-art for live music amplification came down to what Bose dubs the “Triple System”: backline speakers, stage monitors, and PA speakers.

Unfortunately, this system means that artists on stage and audience members generally hear different mixes. This makes it much tougher for the band to play off each other, or to adjust their own performance for the crowd. Furthermore, the directional characteristics of the monitor and backline speakers can make it difficult for band members to hear themselves on their monitors. To compensate, a band member might turn up her monitor. The next band member can’t hear his monitor, so he turns it up, and so on. Now the sound man in the audience has to turn up the PA system to compensate for reflections from the monitors, and we’re left with the common problem of the sound mix being too loud.

Bose decided to attack the problem by using a line source speaker (they use the term “Cylindrical Radiator”) placed behind the band to act as monitor, backline, and PA. The narrow vertical directivity of the array, as well as the 3 dB SPL reduction per doubling of distance means that the soundfield on stage and in the audience is fairly uniform. The band can hear themselves at a reasonable volume, while the audience can hear the mix to which the band is playing.

I have to admit, using line-source speakers in this application is innovative. Again they key is supplying a uniform sound field, and in that sense, the speakers do a very good job. Normally you hear the amplified sound come from the PA speakers mounted at the sides or above the stage. This means that the sound your hear at a live event comes from a different location then the band on stage. With the Bose speakers placed behind each band member, you could actually close your eyes and hear where each member was standing on stage. This was a first for me for a live amplified event.

I will say that I was a little disappointed in the low-end produced by the bass modules (note that Bose doesn’t refer to them as subwoofers). But overall, I think the speakers represented an improvement over the typical live sound system.

During the presentation, the speaker implied that Bose invented their column source speaker. As I’ve mentioned before, line-source speakers have been around for some time, so they’re nothing new. But using them for live sound reinforcement is an interesting application (for the record, I don’t closely follow the sound reinforcement field, so if this has been done before, please let me know). Now there may actually be an innovation in the engineering of the speaker - one colleague suggested that Bose may have applied some sort of electronic or digital time-alignment to improve the performance of the line array. Hopefully we can get one of the engineers to a GBC-ASA or BSA meeting to discuss the engineering behind the speaker.

But in the end this product can help live music sound better, and that’s a good thing.


You may have seen car commercials touting “Quiet Steel.” The Seattle Post-Intelligencer has a brief article describing it’s benefits. It looks like the material is using a form of constrained-layer damping to reduce structure-borne vibration.

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