Tube Amps, Magnapans and Impedance

I don't know whom at Magnepan you talked to, but the 3.7 "6-8 ohms throughout the audible range"? Nope, it is 4 ohms over most that range, dropping to 3 ohms at some frequencies.

The original version of the Tympani T-I (which I owned in the 70's) was a nominal 8 ohm load, but Magnepan re-engineered later Tympanis to 4 ohms (my Tympani T-IVa are), and all subsequent Maggies have been as well.

Fortunately the load is---unlike ESL's---almost purely resistive. It's not a difficult load, but Maggie lack of sensitivity coupled with it's modulus of impedance (the fancy term ;-) makes it a power sponge. While tube amps do work with Maggies, high-power tube amps are costly to buy and own. Low sensitivity/impedance loudspeakers eat power tubes for breakfast, lunch, and dinner. Lovers of Maggies and tube amps solved that dilemma in .6 and earlier models (which have parallel cross-overs) by bi-amping---using a high power amp on the bass driver, a medium on the midrange drivers and tweeters. In the .7 models Magnepan switched to series cross-overs, which cannot be bi-amped without surgery on the speaker.

Points well taken, thank you. Guess its time for a higher powered amp!

I think there are a lot of things besides amp/impedance matching that goes into our enjoyment, or lack of, a combination. The closest I could find were these measurements from Stereophile:

https://www.stereophile.com/content/magnepan-magneplanar-mg36r-loudspeaker-measurements

Speaking only about impedance matching, a speaker like this may have a slightly depressed mid-treble with a high output impedance amplifier. Is that bad? Well, depends on your room a great deal. You might have already tuned the room to compensate by making it less absorptive than you would have otherwise. Another thing to keep in mind is the amplifier’s output impedance. It may very well be complementary to the speaker’s and cancel out, or be a lot less reactive than you think.

With an ESL however, with an impedance curve that goes straight down, a solid state amp can really ensure you aren’t completely missing out on the treble.  My point here is that Maggies and ESLs are different beast and if you are happy don't let impedance curves make you unhappy alone.  ESL's however tend to be really good candidates for SS amps, but yes, there are exceptions.

So, no, changing is not a must. It will probably give you a different presentation and your judgement will tell better than armchair guessing based on the impedance curve of the speaker alone.

buy a new or used beast you can return, hear, keep or return.

Of course, my experience only:

There is something very right about Maggies and a good tube amp(s). Much is always made about Maggies liking a lot of power. There is some truth to that; however, “liking” is not the same as needing; and “needing” is in good part determined by one’s sound priorities and listening habits. What I mean is, the sound that “3” series Maggies and a good tube amp in the 100 W range produce will be, for me, usually superior to what I have heard from most mega watt SS amps.

To my ears, Maggies’ inherent sound benefits tremendously from the plush dimensionally of a good tube amp that will also impart a bit of juiciness to the timbre of instruments. With SS amps the sound tends to be too timbraly dry, in my experience. I’m not talking about departure from what many consider “accuracy”, but actually bringing the sound closer to the sound of real. I know there will be disagreement about this point, but that is my experience having lived with MG3A’s for many years. My point with all of the above is that if you don’t need extremely loud (subjective) sound levels, be careful about switching to a SS “higher powered amp”; if that is your plan. You wrote:

**** I stipulated that it is good electrical practice to match the load to the amp ****

This comment goes to all the above and to the importance of, when all is said and done, basing your decision on LISTENING.

One of the amps that I drove my MG3A’s with before settling on a pair of Manley 100/200 tube mono blocs (which I still use) was the tubed Berning 2100. A fine amp that had a choice of transformer impedance taps. In spite of the theoretical electrical “advantage” of using the 4 Ohm or 6 Ohm taps, the Maggies sounded much better on its 8 Ohm taps. Yes, on the 4 Ohm taps there was a VERY SUBTLE sense of SLIGHTLY more powerful and better controlled bass, but the overall sound was cloudy and with less dimensionality than on the 8 Ohm taps. A clear (😉) choice for me. Btw, my Manley’s are switchable between 100W in “triode” and 200W in “ultra linear” modes. On the Maggies, with the exception of somewhat more powerful bass, with half the “power” the sound in triode mode was infinitely better.

Good luck and don’t be too swayed by theory, but by what your ears tell you.