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Bose use Genelec

hyperplanar

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For fun and to counterbalance unscientific anti-Bose.

+/- 0.1 dB driver matching (Source: a page claimed to be from a magazine, purchased for fun at a very cheap price at ebay. I do not guarantee that this ad is real.)
View attachment 113970

The wording comes off a bit intentionally ambiguous to me, is it not possible that what they are saying here is the measurement system has 0.1 dB accuracy? If so, that has no bearing on the tolerances of the drivers, just that they can measure them that precisely.
 

skyfly

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The wording comes off a bit intentionally ambiguous to me, is it not possible that what they are saying here is the measurement system has 0.1 dB accuracy? If so, that has no bearing on the tolerances of the drivers, just that they can measure them that precisely.

I also felt the vagueness you mention.

This interpretation is possible: Bose measurement system can display -0.1, 0.0, 0.1, 0.2, 0.3 dB, etc., but not -0.05, 0.00, 0.05, 0.10 dB, etc., nor -0.01, 0.00, 0.01, 0.02 dB, etc. With that measurement system, they can choose various tolerance values: 0.1, 2.3 or even 5.8.

In such a vague situation in reading, we use common sense and the context.

Is a sound pressure level measuring equipment with 0.1dB resolution something engineers think impossible? Of course, not.
Hence, combined with the previous paragraph about coil winding precision, the interpretation is that Bose' choice of tolerance value is +/- 0.1 dB (probably not channel imbalance, merely the raw drivers to be put into one channel).
 

skyfly

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The wording comes off a bit intentionally ambiguous to me, is it not possible that what they are saying here is the measurement system has 0.1 dB accuracy? If so, that has no bearing on the tolerances of the drivers, just that they can measure them that precisely.

You are right. I need to correct my claim. Bose did not reveal the driver tolerance figure that "engineers would have thought impossible."

If "+/- 0.1 dB" is the tolerance figure for driver matching, they would not write "the net result is . . matching."

[coil winding precision]
+ [computerized quality control procedures (the 0.1 dB figure appears here)]

-> the net result is the degree of acoustical matching "most engineers would have thought impossible" (the driver matching tolerance figure was not revealed).

Lawyers could still earn money if Bose 901 driver matching was not excellent compared to the industry standard at the time of advertisement. In addition to the tolerance level itself, the cost to achieve the tolerance level (or the price of 901 system for consumers) would be considered in the court, too.
 

hyperplanar

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Is a sound pressure level measuring equipment with 0.1dB resolution something engineers think impossible? Of course, not.
Hence, combined with the previous paragraph about coil winding precision, the interpretation is that Bose' choice of tolerance value is +/- 0.1 dB (probably not channel imbalance, merely the raw drivers to be put into one channel).

Hmm, being able to consistently obtain measurements with 0.1 dB accuracy (not resolution) is actually pretty difficult, as far as I understand. I forgot the exact post, but while reading about the frequency response measurement accuracy of the Klippel system, the consensus seemed to be that +-1.5 dB between measurements taken on different systems is considered to be good. In other words, up to 3 dB of variation from the ground truth is currently acceptable in measurements, so if Bose managed to get that down to 0.2 dB, then that is indeed impressive. The whole debacle that went on about the inconsistencies in the KH80 measurements is what sprung to mind.
 
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