@tvrgeek wrote:
Thermal compression happens to all drivers, high sensitivity or low. How much depends on how well the motor can dissipate heat.
It happens to all drivers regardless of sensitivity, yes, but obviously at different stages; all things being equal a 10dB gain in sensitivity means a given SPL has less heat build-up in that voice coil than the lesser sensitive variant being it handles 10x less power. To boot the more sensitive driver, typically a pro segment ditto, has better power handling with a larger diameter voice coil and usually better gap cooling, so it’s not even an "all things being equal" scenario but rather one that generally favors the more sensitive driver as well with regard to heat dissipation.
For example, fero-fluid may dissipate heat better and have lower thermal compression ( re increasing with temp) but it is not without other issues that can effect perceived dynamics.
True, on both accounts, but here the basis of comparison is other tweeters with similar-ish sensitivity, where ferrofluid-using variants may see an advantage in regards to power compression "fatigue" for a given SPL. (At a panel discussion some 30 years ago with the late Hother Bak of Dali, he argued ferrofluid could have resonant damping qualities in the voice coil, but they ultimately worked towards avoiding ferrofluid in their tweeters due to, as you put it, "other issues")
Same goes for the flexibility of the suspension, that can actually get "looser" with heat for less compression. Drivers are a combination of parameters, some working in opposite directions giving a better all things considered performance than any one part looked at in isolation.
This is an interesting field of discussion. Question is if there’s basis for speculating into mechanical "compression" at lower SPL’s with more stiffly suspended pro drivers. They are, some of them, thought to be less adept sonically at lower volumes, only to open up with more prodigious SPL’s - which is their intended target range anyhow. Myself I’ve invested some effort into selecting my particular pro cinema speakers and knowing their drivers in these regards, but usually high efficiency speakers are known for their great low-SPL capabilities, coming-to-life and overall attentiveness here. Some guys, like Devon Turnbull of Ojas, are keen on selecting rather low power handling, high efficiency pro driver designs of yore with their lighter voice coil assembly, overall moving mass and higher compliance, matching them up with low powered and topologically simple tube amps. The rationale likely being (if it doesn’t simply come down to a preference based on listening only): why all that power handling (and amp power capacity) from pro drivers with their high efficiency for use in a domestic environment? Devon finds some of the modern pro drivers "lethargic" sounding compared to the older designs he prefers, and while in certain contexts at least his views here are not without merit, I don’t entirely agree with him.
However, all things considered, thermal compression is most likely a wash between technologies. Other factors already mentioned ae greater.
It’s not that complicated. Pragmatically speaking sensitivity and power handling are the primary factors, and ones that have direct implications on dynamic capabilities. And as already mentioned, passive crossovers is a factor as well.
