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

This seems to be a good argument in favor of quite high efficiency speakers such as my 106dB/watt/meter horns.

Are you hoping to increase audio neurosis?

I think my 150lb speakers and umpteen voice coils are not heating up with my 10 wpc amp running at 1/3 power.  Efficient speakers and low power amps is my preference.  That said, a well designed speaker that runs on much higher current should have plenty of current capability.  For example.  Crossovers usually use 15watt resistors  for low current so they won’t heat up and change value.  

I never gave this much thought, intersting....I’m seemingly driving my Tannoy Eatons with 30 watts of Sugden class A, and I can’t get past 11 o’clock on most if not all material. Plenty loud for me and my room. 

@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.

 

 

what about low efficiency planar speakers like apogee scintilla, it seems like they would dissipate heat better.

It’s also part of the sound of interconnects.

Besides the problem of the given audio cable having it’s most perfect impedance at exactly one frequency and one frequency only.

Where all other frequencies are imperfectly handled and are converting to heat and distortion in the phase realm or time realm. smear. noise.

When we turn up audio systems, it is also happening in the cables (eg, preamp to power amp and speaker cables), where they get overloaded and they reach a certain threshold of distortion vs clean, and we hear it, like a crunchy noise or transient smear aspect. that’s cable screech and we all dislike it. A well designed cable has the least of it as is possible. Or some mud it up, and achieve being comfortable at the cost of all other aspects of signal clarity. All cables are compromises designed for the hearing of individuals with individual gear. That’s why there are so many brands and designs.

That is part of what we complain about when we say that passive preamps are not as good as active preamps.

The most linear of all in this area of technological challenge across all levels of loading, is the liquid metal audio cables. We’re talking a good minimum of a magnitude better, to the point that all complaints are pretty well entirely gone and people relax into realism. There is a reason that our now closed Hong Kong Distributor, who was active in and describable as the peak of the Hong Kong High end scene (no small thing, that!), called our best cables ’the biggest most important positive change in audio, of all time, in all technological areas of audio’. The only way to know if it is, or not...it is to try them out.

 

It's also difficult to imagine ahead of time as all things ever made utilize wire and solids. It’s a huge deal. Literally. How can one understand the existence of being a box when the lexicon of ’box’ and ’external to the box’ has never before been elucidated, whatsoever? Paradox. It’s simple. Just listen.

We also produced a liquid metal passive preamp, that threw those complaints about passive preamps out into the street, we banished them. Those who have tried it, and are chasing down the ghost dragon of perfection (it’s not a math problem! Careful!) ... tend to think it is superior to all preamps, passive or active (at any price).

PS, if you ask why were' not on everyone' slips and in every one's system(if we're so dang odd, like I say, pfffft...), well it is jungle out there ....and we don't have a million dollars to spend on advertising and reviews, so that we can make $100k on the vanishingly small group who do actually recognize and seek the best.

Not likely.

I don't care.

The Xover helps to relief stress high quality Xovers are one Big thing most mags don’t address unless spending over $20 k even then not top parts quality,

personally I have been  doing high  quality Loudspeaker upgrades for years, 

for example mode use $3 mox resistors ,or low cost ceramic , myself

Top quality$30 each Mundorf Ultra ,or Path audio resistors  and very low e noise capacitors , and quality large Copper open core or Foil inductors ,

many use cheap bobbin type ,or sledgehammer wire around amagnet  these inductors dissipate heat away from the driver , if you buy a quality loudspeaker, then most of these heat issues will be addressed .

@teo_audio 

 

When you say "it is also happening in the cables (eg, preamp to power amp and speaker cables), where they get overloaded and they reach a certain threshold of distortion vs clean, and we hear it" are you implying that electricity slows down or gets backed up in a cable if someone turns the volume up? 

Another case of "Something You Never Heard Of That Doesn’t Matter."

It is usually referred to as thermal compression—as music gets louder (more current flowing), the heating of the voice coil means that any increase in the signal level does not result in a proportionate increase in sound level because the heated wiring resists the current flow. This is the principle reason why high efficiency speakers tend to be more dynamic—far less thermal compression.

 

It’s also part of the sound of interconnects.

Not likely.
This sounds like a #metoo post where interconnects are suffering compression like speakers.
And it reads more like an advert for something not on topic nor germane to speaker compression.

 

Besides the problem of the given audio cable having it’s most perfect impedance at exactly one frequency and one frequency only.

Where all other frequencies are imperfectly handled and are converting to heat and distortion in the phase realm or time realm. smear. noise.

…

OK a 1v signal from a preamp with 600 ohms of output impedance will have < 0.002 W (If shorted).

Into a 100k ohm is almost no “work”/“power”.

 

All cables are compromises designed for the hearing of individuals with individual gear. That’s why there are so many brands and designs.

BS most cables are neutral.

 

That is part of what we complain about when we say that passive preamps are not as good as active preamps.

I found ^that^ pretty hard to believe,

The fact that the output impedance takes a thrashing at low levels is more likely the lion’s share of trouble.

The most linear of all in this area of technological challenge across all levels of loading, is the liquid metal audio cables. We’re talking a good minimum of a magnitude better, to the point that all complaints are pretty well entirely gone and people relax into realism. There is a reason that our now closed Hong Kong Distributor, who was active in and describable as the peak of the Hong Kong High end scene (no small thing, that!), called our best cables ’the biggest most important positive change in audio, of all time, in all technological areas of audio’. The only way to know if it is, or not...it is to try them out.

You distributor’s words should be that they are better than sliced bread. This is not unusual.

 

<Advertisement removed>

 

PS, if you ask why were’ not on everyone’ slips and in every one’s system(if we’re so dang odd, like I say, pfffft...), well it is jungle out there ....and we don’t have a million dollars to spend on advertising and reviews, so that we can make $100k on the vanishingly small group who do actually recognize and seek the best.

If the gear did all of ^that^, it would be nice.
Someone should try it.

What return policy is there?
If you can convince me, then it should get easier with less skeptical types.

===============

Back to thermal distortion of speakers, it is one of the things I look for,
The crossovers can take a thumping in addition to the speakers.

Probably the simplest example/change would be active cross overs.
Say we had a 30W amp, and if it is not clipping it is somewhere in the 1-5W RMS range. And at say 1W RMS there is typically 150 mW going to the tweeter
Now we turn up so it clips and we can get it to ~42w, and probably 20W is going to the tweeter.

So we do an active XO and the tweeter gets maybe 1W and the woofer has a bigger amp, and there is no actual passive XO to fry.

No, I don't care.  And I don't care if you care, either.  Problem solved.

There is a point (temperature wise) where equipment sounds the best. Most audiophilers don't overheat voice coils in their units. That is a problem KIDS have in sound competition. I have never had a problem with overheating parts. For me it's audiophile 101. "Protect your expensive (or inexpensive) equipment FIRST, everything else is next". I use small planars, you have to really abuse one to have them fail. If they blow I can't imagine what "that" someone's hearing is actually like. LOL no hearing insurance for that one.. Just Nose and Throat, no EARS.. 

@larryi +1

Link that works LS_Heat_Dissipation-Thermal_Compression

It also affects the XO frequency. See ieLogical the fly...

The argument for high efficiency is specious as they have light coils with thin wire, which heats faster with less current. And lighter diaphragms and weaker surrounds which give rise to other issues. And lousy bass from ported boxes...

As is the cable nonsense. The effect is so low as to be next to immeasurable.

Planars suffer almost not at all. Ditto 'stats.

The crossover issue is solved by using active XO, DSP and an amplifier per driver instead of stone age copper coils and foil and goo. Professional audio has been doing this for nearly 100 years!

The only time I had a heat problem is when my Carver amp went bonkers and before I could turn it off it had melted the varnish on the voice coil of the 2235H in my JBL B380 sub-woofer. 😊

@holmz +1

OMG, I from suffer TD and had no idea!

@johnk --

Thanks for starting this thread. 

"But do you care?"

Most certainly, but not for the reasons outlined by quite a few here about avoiding one's speakers going up in smoke. What's interesting to me is how thermal compression/-distortion can impact the sound at a much earlier juncture than speaker failure or overheating per se: with "thermal modulation," eloquently put into words by poster @audiokinesis ..

"During the recent "great recession", I spent most of my time over on the prosound side of things. Imo, there's a lot of validity to Mtrot's observation: "I'm beginning to think the ability of speakers to achieve that sense of dynamic "liveness" may be as or more important to a sense of realism than frequency response accuracy."

On the acoustics side, I take the word to mean unrestrained dynamic transients. Compression can come from amplifier clipping or loudspeaker thermal or mechanical limitations. I believe that the most common culprit in loudspeakers is "thermal modulation", a quick-onset compression that results from the near-instantaneous heating of the voice coil from a high-power transient.

On the psychoacoustics side, "slam" registers when a limbic system response ("fight or flight" startle) is triggered. It is a function of transient dynamics and raw SPL. If there's not much dynamic contrast, it doesn't come across as "slam". If there's good dynamic contrast but the sound pressure level is still soft, it doesn't come across as "slam".

From a loudspeaker design perspective, the solutions include high efficiency and/or large diameter (or multiple) voice coils. If a loudspeaker system is being pushed close to its RMS thermal rating on peaks, your peaks are softened and so is the emotion conveyed. If a loudspeaker system is just loafing along at fairly high SPL, it will deliver plenty of slam. That's why 5 watts into a 98 dB efficient speaker almost always sounds so much more lively than 200 watts into an 82 dB efficient speaker, even though "on paper" both are 105 dB capable.

Duke
dealer/manufacturer"

https://forum.audiogon.com/discussions/quot-slam-quot-what-is-it-is-it-really-accurate

The proof is in the eating of the pudding, as they say. 

@ditusa --

Thanks for provided article on the subject (and to @ieales for the link). 

"It is clear, however, that even the best transducers will power compress and yield less than desirable performance at the limits of their power capacity. It therefore makes the most sense to operate drivers well below maximum power to achieve desirable performance. The ideal operating level will track with power handling, and drivers with high power ratings and good shortterm capability (high T and low Rg) will be the best choice."

Indeed, "well below maximum power" says it clearly; it's about maintaining ample headroom, even at the highest SPL's to achieve the best sonic outcome, and so this is really not about the risk of frying one's speakers (though it may pertain more readily to pro installations) as much as it is sonic implications. 

Heat also affects passive cross-overs and in effect the sound from such passive speakers, which has been pointed to above, consequences that are happily avoided with active configurations. 

I am a big fan of efficient speakers.  I don't understand why manufactures make 4 ohm speakers for example.  I believe you need more power to drive them.  If that is the case, I would imagine this in turn creates more distortion.  Not sure if I understand this correctly.  Just an observation I have had.  I would think higher efficient speakers can create higher amounts of head room as well.

4Ω or 8Ω speakers are a myth.

Just look at the impedance curves on Stereophile. Some go from 2 to 20 and beyond.

SPL efficiency @ 1w or 2.83v is also highly suspect as few speakers are 8Ω @ 1kHz.

 

I think this heat issue may effect high frequencies most.

And it may be that the AG sold, “Deulund-Mundorf Ultra Speaker Purifiers” could be the solution to the heat issue. After 100++ hours of breakin they have had a profound effect on the soundstage and imaging. I now hear layers in a wide and deep soundstage and imaging has come into focus like never before.

These can be self made but the seller adjusts the values of the cap and resistor to match your speaker’s needs. 
This idea is not new. They are also known as Zobel Networks.

They only effect frequencies 12K and above. So above the crossover point of most.

Radically improved my listening experience.

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

 

 

Speaker testing often shows thermal compression at 86, 96 and 102 dB.
So if one is listening at 80-85 dB, and there is little or no thermal compression at 102dB, then that is ~20dB of dynamic range.

Hence it is something that, IMO, is worth considering as much as FR.
Along with the HD and IMD, it shows a lot to be concerned about.

@johnk        Does thermal distortion affect only coil powered cone type drivers?

If so, here's another good reason to go to panels.

Does any cone speaker manufacturer include cooling to reduce thermal distortion?

 

@tubebuffer    Can anyone understand what you are talking about?  I guess your system must affect your pubic hairs.  Is the answer to shave them all off?

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.

Thermal changes with power are much more likely to occur in your amp.

The article above is specific to voice coils which can heat up with high power (near rated power).  So I'm driving a pair of speakers with 800 wpc power handling with a 10 wpc amp.  I think I'll be ok.

Jerry

@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!

Pannels don't suffer from it but they have their own design limitations related to limited excursions, dipole effect cancellations, beaming, and pannel size reducing higher frequency. Nothings perfect.

We're not debating merits, we're talking about thermal distortion. 

+1 @ieales … another #metoo attempt, and this time trying to sneak in panels as a heat stroke sufferer.

Insignificant in properly designed loudspeakers. High efficiency helps keep distortion to a minimum.

Back when tubes were king, high efficiency speakers were very common because tube power was (and continues to be) expensive.

When solid state amps were commonplace, speaker efficiency started to go down.

The problem here is that it never helps to have an amplifier drive a speaker that is a difficult load and in particular low efficiency. The result will be higher distortion from the amplifier if nothing else, and that distortion usually manifests as higher ordered harmonics, to which the ear assigns the tonality of 'harsh and bright' and is keenly sensitive to their presence since it uses them to sense sound pressure.

So we've been hearing 'harsh and bright' for 50 years now. Some is the fault of amplifier design of course, but difficult to drive speakers don't help. 

So inefficient and low impedance speakers should be avoided if you want to get the most out of your amplifier dollar investment.

 

It's a question of balancing speakers and amplifiers.

If speakers are 86dB/2.83v/1m, then you better have at least 200wpc and preferably 400w good, clean undistorted power @ speaker minimum impedance.

Professional studios may have 1000wpc driving horn multiway speakers, usually without power eating passive XO.

Sadly, too many today have zero understanding of basic fundamentals and buy faceplates.

 

Modern high powered amps (400+ watts) that can run into a 1 ohm load can certainly burn pretty much any low impedance device up. How much heat is developed depends entirely on current flow which depends in part on the impedance of the load, lower impedance devices being more likely to heat up. How fast depends on the amount of heat sink is available for the device and how well it is ventilated. 

The most significant problem is not thermal distortion but failure of the device. Modern voice coils with Kapton formers are surprisingly tolerant. Although resistance does increase with temperature the effect is minimal. It might skew the frequency response of the speaker a little and decrease output or available power but it will not cause IM or Harmonic distortion. You can read about the effect here https://www.cirris.com/learning-center/general-testing/special-topics/177-temperature-coefficient-of-copper and here,  https://en.wikipedia.org/wiki/Power_compression#:~:text=In%20a%20loudspeaker%2C%20power%20compression,power%20of%20the%20audio%20amplifier.

Thermal compression can be a problem in large commercial concert systems. It is not a significant problem in home HiFi systems. It would best be characterized as inaudible. The sky is not falling and you need not go looking for 16 ohm loudspeakers. Take a deep breath and say,"OOOOOOOOHMMMMMMMM.... 

 

@atmasphere --

 

"Back when tubes were king, high efficiency speakers were very common because tube power was (and continues to be) expensive.

When solid state amps were commonplace, speaker efficiency started to go down.

The problem here is that it never helps to have an amplifier drive a speaker that is a difficult load and in particular low efficiency. The result will be higher distortion from the amplifier if nothing else, and that distortion usually manifests as higher ordered harmonics, to which the ear assigns the tonality of 'harsh and bright' and is keenly sensitive to their presence since it uses them to sense sound pressure.

So we've been hearing 'harsh and bright' for 50 years now. Some is the fault of amplifier design of course, but difficult to drive speakers don't help. 

So inefficient and low impedance speakers should be avoided if you want to get the most out of your amplifier dollar investment."

But what makes a speaker a difficult load also and not least involves the effects of passive cross-overs (unless this is implicit to what you're saying here, but it's unclear to me) in terms of their complexity and the (steep) phase angles presented, not to mention smearing of the signal here.

This is interesting due to observations I've made going from passive to active speaker designs (with the same speakers), where I've found going active with solid state amps makes for a sound more akin to the sonic imprinting of SET's; passive sounds more sluggish, heavier even and less resolved (but to some more pleasing this way), whereas active makes for a more transiently clean (less smeared), less grainy and more liquid and open presentation. Easier on the ears, and more fleshed out.

I'd have cherished the opportunity of using 16 ohm versions of the drivers used in my speakers (not least the compression driver, which is available in a 16 ohm version), having then both high efficiency, high impedance and passive filter-less speakers. I would assume though passive filters and their negation to be a similarly or even more important means of making the amp seeing into an easier load, certainly bypassing more complex passive filters. A "purer" low impedance load seems preferable to a higher ditto marred by steep phase angles, but I guess it also depends on the specific amp. 

I only turned it up for a minute!

@johnk actually I am going to walk back may earlier post.

If the crossover or other electronics in a planer speaker are not suffering compression, then it is entirely reasonable for you to have mentioned it.

so it’s a sage post,
 

apologies sir.

Crossover components most certainly can get hot enough for thermal compression to be an issue.  A friend of mine who repairs gear showed me a couple of inductors he took out of a pair of speakers that where played at a really high volume level.  Remarkably, the drivers were not blown, but the plastic formers for the inductors completely melted--what was left was a spool of wire sitting in a pool of plastic.

 

Can anyone confirm my lay understanding that Zobel Networks do, in fact, have a significant, if not great, effect on the SQ when applied correctly to a speaker?

AKA, “Deulund-Mundorf Ultra Speaker Purifiers” sold on AG.

k

It's a filter. Whether the correct one may be speculative.

Please pardon my ignorance, but I am confused by the references to liquid metal wires or liquid metal passive preamps.  What metal that is liquid at room temperature is used to make this equipment?  How is it contained so that it can't leak out?

Don't waste your time.

Eutectic bonding - Wikipedia

Like all cables, it has a sound. You have to drink the Kool-Aid.

This thread really separates the knowledgeable from the clueless. Happy listening 

@fiesta75, +1

ditusa,

Thank you for the interesting paper you attached to one of your postings.  I just got around to reading it and it is very interesting. 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.  I also did not consider that changes in Thiele-Small parameters also add to compression.  Finally, I might add that although the paper does not mention this, heating of the components in the crossover will add to compression.