The quick answer: The weaker the amp, the more its output in the frequency domain will look like the impedance curve.
The under appreciated impedance curve
One thing that a lot of audiophiles don't look at or don't know how to interpret is the impedance curve. I call it the honesty curve too.
Of course, most audiophiles know to look for high imepedance speakers for tubes, and that low impedance speakers are going to be more amplifier demanding.
I also look for:
One speaker which breaks both of these rules was just reviewed at Stereophile, the Wilson Yvette.
https://www.stereophile.com/content/wilson-audio-specialties-yvette-loudspeaker-measurements
Like all things, there are no absolutes but these are the things I look for in a speaker. What do you look for in the impedance curve?
Of course, most audiophiles know to look for high imepedance speakers for tubes, and that low impedance speakers are going to be more amplifier demanding.
I also look for:
- A drop in impedance at 100 Hz at or below 3 Ohms - Indicates "amplifier sensitive"
- A ragged magnitude instead of simple, clearly defined humps. If the impedance is ragged it indicates highly equalized components.
One speaker which breaks both of these rules was just reviewed at Stereophile, the Wilson Yvette.
https://www.stereophile.com/content/wilson-audio-specialties-yvette-loudspeaker-measurements
Like all things, there are no absolutes but these are the things I look for in a speaker. What do you look for in the impedance curve?
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The under appreciated impedance curve Under appreciated?? I don’t think so, to those that find/look and know how to use it. I believe "it" together with the combined "-phase angle" curve (EPDR) if hard to drive, "becomes the no1 criteria" to selecting the right amp to get the very best from that particular speaker. Probably that’s why it’s the 1st thing John Atkinson measures in Stereophile. Cheers George |
I do think that the community at large does not appreciate how much we can learn.I second that. That doesn't mean to be an accusation of anyone in particular.More more it's talked about, the more they'll make a effort to at least try understand them. For those how wish to understand impedance/-phase graphs using Ken Kantor's easy simulated speaker loading. https://www.stereophile.com/reference/60/index.html https://www.stereophile.com/content/measuring-loudspeakers-part-one-page-6 Cheers George |
Bruce Thigpen stated in his discussion on the design of his magnetic-planar driver, the Linear Field Transducer (LFT), that he could make it with any nominal impedance he chose. Bruce says he chose 4 ohms for the LFT-3, LFT-4, and LFT-6 so as to enable the power amp driving them to provide them with as much power as they are capable of producing (assuming the amp is solid state, of course. SS amps produce more power into lower impedances than into higher. Most tube amps are the opposite.). He doesn’t say why he chose 8 ohms for the LFT-8 (and improved incarnation the -8a and current -8b), but by virtue of it being a nominal 8 ohm speaker, the LFT-8/a/b is more suitable for use with a tube amp than are the magnetic-planar driver 4 ohm Magnepans. By the way, if bi-amped, the LFT-8b’s magnetic-planar midrange driver and ribbon tweeter themselves presents an almost purely resistive 11 ohm load to the power amp, and are therefore an excellent candidate for use with a tube design. |
- 19 posts total