We should reject hard-to-drive speakers more often

If we are talking about the original Apogee true ribbon 1 Ohm speakers, this would be news to me.

Technically Atmasphere is correct, they use the aluminum panel as the voice coil

the reasons for thermal compression in actual voice coil speakers can't possibly apply here.

Hence my use of the word 'possible'... In the case of a magnetic panel speaker like the Apogee, the 'voice coil' for lack of a better term can be heated.  It seems to me that would take some power. If it heats, then less current can be applied because the impedance is higher. That's what causes thermal compression. The thing about thermal compression is that it can happen with individual bass notes; IOW the 'voice coil' is heating and cooling dynamically with the music. If the speaker is using a magnetic principle then this can happen. How much it happens is a different matter.

While Atmasphere is correct in saying that it is possible to achieve thermal compression in planar-magnetic drivers, in practical terms it really doesn’t happen much, at least not in larger drivers. Being involved with Analysis planar-ribbon speakers for almost 2 decades, I have witnessed some very informative testing. In one test the bass panel was subjected to considerable power at low frequencies to test thermal saturation and the mechanical integrity of the adhesives used. Even beyond its usable max excursion practically no heat was generated (short term). The very thin aluminum foil with considerable surface area is essentially self cooling. This test was extreme.

I would not call the planar foil a coil because it’s not, at least not in the case of the Analysis design.

Some compression occurs in planar drivers, including ESLs, because the membranes are stretched across a frame. The mechanical impedance is not linear. The greater the excursion the more power is needed. Analysis speakers address this mechanically induced compression by using a rubber surround. The design is quite effective in reducing compression. Other ways around this inherent quality is by using VERY large panels or subwoofers.

To the OP, I think people like what they like for a variety of reasons. Some people like large aluminum boxes with tons of power because they think they are cool, others like tube amp with exposed tubes because they think they are cool. Some people are fulfilling their audio dreams from a time before they had the money to buy their dream gear. There are valid arguments for high and low efficiency speakers. There are also trends.

Personally I lean toward high efficiency speakers. Our Apollo series OB line array speakers are high efficiency for several practical reasons, mainly because HE speakers always sound much more lively (linear dynamic contract) to me. Live music sounds lively. It’s one of the main elements that creates the experience. We will be showing our Apollo 9s at AXPONA using 300B amps if anyone wants to hear high efficiency OB line arrays.

Nope!

get an amp that has enough power and you will be fine

sunfire amps

sanders magtech

odyssey monos platinum parts for low Ohm speakers

The very thin aluminum foil with considerable surface area is essentially self cooling. This test was extreme.

That was kind of where I was going with that. 99% of the surface area of the conductor is directly exposed to air, unlike an actual coil where you may have multiple layers of windings or the former acting as insulators.

Some compression occurs in planar drivers, including ESLs, because the membranes are stretched across a frame. The mechanical impedance is not linear.

True for all drivers, except perhaps the massive fan subwoofers. I think the difference in measurement/thinking about thermal compression vs. mechanical is that thermal compression changes the behavior of the speaker in time, sometimes within milliseconds, while mechanical compression is always there, until you blow the driver. :)

I do think it’s odd audiophiles have fixated on thermal compression, specifically, as being the only one that matters, though I do agree that higher efficiency drivers seem to be at an advantage here.

There’s a reason JBL professional drivers are so expensive, and one of the main reasons that is that they are built specifically to avoid thermal compression even at constant power levels that would make most audiophile systems weep.

"Some compression occurs in planar drivers, including ESLs, because the membranes are stretched across a frame. The mechanical impedance is not linear."

True for all drivers, except perhaps the massive fan subwoofers. I think the difference in measurement/thinking about thermal compression vs. mechanical is that thermal compression changes the behavior of the speaker in time, sometimes within milliseconds, while mechanical compression is always there, until you blow the driver. :)

As a mechanical compression artefact this is hardly true for all drivers. Dynamic drivers have suspensions, and the "stretch" of a membrane here wouldn't occur in a way comparable unless the suspension iself is (getting close to being) mechanically edged out. 

I do think it’s odd audiophiles have fixated on thermal compression, specifically, as being the only one that matters, though I do agree that higher efficiency drivers seem to be at an advantage here.

Question is when, and perhaps not least how thermal compression starts becoming prevalent and an actual audible effect. Thermal 'modulation' may be a better term to explain or correlate what happens sonically; thermal compression impacts SPL envelope and ultimately driver failure, but it also appears to dull transient cleanliness and snap at a much earlier juncture as a very dynamic phenomena. 

There’s a reason JBL professional drivers are so expensive, and one of the main reasons that is that they are built specifically to avoid thermal compression even at constant power levels that would make most audiophile systems weep.

Other pro brands would do equally well, and at a cheaper price, but yes pro drivers are simply on another level here.