Thermal Distortion your loudspeaker most likely suffers from it. But do you care?

 Matching the type of speakers with the best amplifier makes a huge difference. 

I concur.

Mike

Welcome to the real world of ’power compression’. JBL ^{[ 1 ]} has performed tests showing that power compression can reduce output by anything from 3dB to 7dB from the expected SPL at elevated temperatures. Seven Decibels!

Two article just came to mind!

Mike

https://sound-au.com/articles/pwr-vs-eff.htm#s

Your welcome!  

@larryi

Not only does heat affect the voice coil, to the extent the heat gets into the magnetic structure, flux is affected which further adds to thermal compression.

Yes That is one of the many reason for using ALNICO in permanent magnet speakers, it's impervious to heat so it's flux is not affected by the change in temperature.

Finally, I might add that although the paper does not mention this, heating of the components in the crossover will add to compression.  

You are correct I think you can fix that with an active crossover. 😁

But prior to all that, the industry moved away from field coil to permanent magnets, not because permanent magnets were better, but because they were cheaper as well!

That is correct.

@holmz +1

@johnk Said,

Thermal Distortion is audible and measurable

I agree!

I thought about thermal distortion (TD) some 45+ years ago. My speakers are designed to have a power linearity of < 1 dB of SPL compression output from 1 watt to 100 watts and their efficiency is 2.7 %.

Mike

Here is a good article on the subject.

@larryi +1

@carlsbad Said!

Just to be clear.  there is never enough current in an interconnect to heat it up and change its electrical properties.

Same with speaker wires unless they are drastically undersized.

You sir are correct!

@fiesta75, +1

This gentleman understood the importance of speaker efficiency. See link below

Enjoy! That's what it's all about! 😎

Mike

http://www.lansingheritage.org/html/jbl/reference/technical/efficiency.htm

''Alnico magnet’s were/are sometimes prone to demagnetize:''  Yes!

My understanding is: The JBL LE15A 15'' Alnico woofer has a top plate of more then 1/2 an inch thick, short coil, long magnetic gap, the flux density in the voice coil gap is 11000 gauss, hence it will not demagnetize itself when hit hard with high level input power. That's one of the reason why its considered to be the best vintage 15'' Alnico woofer JBL ever made. Also Alnico is the best for making permanent magnet speaker drivers, Alnico stability and resistance to back EMF is really good. JBL engineers discovered that more then 75 years ago. That is the reason why JBL chose Alnico 5dg magnet for the JBL1501Al-2 woofer, not Ferrite nor Neodymium. Enjoy! That's what it's all about! 😁 

IMO Ferrite is basically a lousy magnet material for speakers but it is cheap and readily available. 

Mike

''The new 1500Al used in the S9800 can take continued pulses of 5000 watts and loose no more than 1%. The test can only be done a few times before the coil is destroyed, but the magnetic assembly is totally stable.''-Greg Timbers JBL engineer

http://www.lansingheritage.org/html/jbl/specs/pro-comp/2215.htm

http://www.atma-sphere.com/en/resources-common-power-amplifier-myths.html

@larryi,

The interesting thing about Alnico magnets and compression is that some theorize that the particular sound of Alnico magnet speakers is that they are actually subject to more compression than other magnet types because flux density is lower under dynamic conditions when the voice coil is excited.

I think they are confusing dynamic instabilities within the voice coil with compression, I could be wrong. Also, JBL uses Alnico 5dg magnets. The 4dg and 3dg magnets are lower in strength as some design require less strength. Just when you thought you had perfect sound. LOL 😎See link below: Suspension Bounce as a Distortion.

Mike