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RE: Zu Soul Supreme sensitivity

Posted by RGA (R) on June 1, 2017 at 17:47:23

In Reply to: RE: Zu Soul Supreme sensitivity posted by Dave_K on June 1, 2017 at 08:15:18:

Well that's fair enough. The AN E, DeVore and Tekton won't compete with the big horns on ease of drive - that's for sure.

Although Peter Qvortrup answered some of this in the High Efficiency forum:

Only 39 posts so get out the popcorn for those interested in how they measure and that other magazines achieve the results stated by the manufacturer.

"By the way, Martin Colloms asked me the exact same question when he reviewed the AN system 3 - 4 years ago, as he also had difficulty believing the efficiency rating, I showed a quick if somewhat simplified example of how we arrive at the stated efficiency ratings, which is done by combining 2 far field sound pressure measurements to get a room power response which is then used to calculate the efficiency, backwards so to speak.

Martin clearly agreed with the published 96dB/watt efficiency figure having tested the AN-E/SEC Silver, as he does mention in the review.

So here is a brief outline of the procedure, using the highly sensitive system we also use to match the drivers to the crossover and the reference, to get a near perfect match within pairs and to the reference,

1.) With the speakers in the correct corner loaded position, we take two sound pressure measurements at two different output power levels in two positions, using a broadband complex waveform (music), plus a series of sweep tones 15Hz to 25kHz, why use two different powe levels you may ask?

The reason for this is that I have found that many speakers appear to have an optimised behaviour at 2.83 volt input and their efficiency drops disproportionally if presented with less and in some cases more power, why this is, is a whole different question.

2.) We repeat this procedure at 3, 4 and 5 meters, using two speakers and a 2A3 or 45 and a 300B SET amplifier, each time noting the voltage output power from the amplifier and the corresponding sound pressure level.

We then compare to two reference speakers of "known" efficiency, measured the traditional way (as JA did with ours), then repeat the way we measured our speakers, compare the difference in efficiency at listening distance, average for distance and then work their room energy efficiency backwards so to speak.

We add/subtract the difference between these reference speakers and ours to get the figure we publish.

Inconvenient?

Yes, but it gives a far better and more accurate measure of what the real power transfer and equivalent sound pressure level is, and therefore closed to what the actual efficiency of the speaker is likely to be in situ in room, because if you take a 1.5 watt amplifier and you can get 100dB plus out of a speaker measured at 1 meter before audible clipping, then the speaker must be more than 92dB efficient, wouldn't you say..."

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Edits: 06/01/17

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