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Matching amps to speaker efficiency

Posted by M3 lover (A) on October 7, 2020 at 09:43:57

Reading the post and comments below on the PASS X150.8 reminded me of a past experience.

For 19 years I owned and enjoyed Duntech Princess speakers. They were rated at 90 or 91 dB, so a little more efficient than an average model. However the owner manual recommended "at least 200 wpc for musical enjoyment". From my own experiences in auditioning amps over the years I was always puzzled by that relatively high efficiency rating. I suspected it was based upon ratings for the selected drivers rather than an actual measurement of the completed speaker.

My knowledge of electronics is very limited but I suspected I figured out why those speakers seemed to demand greater power than their efficiency rating would suggest. First, the 1st order crossover was very complex and so contained a number of parts. Not as bad as the link photo but the PC board was loaded. Second, the impedance curve dropped just below 3 ohms in the bass range. That had to demand a fair bit of power.

After trying numerous amps over the years I found two solutions that made the speaker come alive. I was using a pair of VTL 300 mono amps which were quite good. On a whim I borrowed a pair of VTL 225 monos and connected them for passively bi-amping. The speaker had a bi-wire option so I was still going through the internal crossover. That combination was amazing, but 4 amps and 32 output tubes was not practical for me. I finally settled on JC-1 mono amps rated at 800 wpc into 4 ohms. That was my final solution. Regardless if it seemed to be overkill for 90 dB speakers.

The moral of my story? You can't rely on speaker ratings when considering amp choices. You may need to research the speaker specs, and still experiment with amps.


"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho

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Edits: 10/07/20

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