Speaker sensitivity vs SQ

First, thanks to @b_limo for posting the DeVore video. I hadn’t seen that before and it is the best explanation of the relationship between sensitivity and impedance I’ve ever seen.

Several good answers to the original OP question but I wanted to add my own experience. For some reason I’ve been attracted to the sound of low sensitivity speakers for as long as I’ve had this hobby. It goes back to a pair of Large Advents that I bought in the 70’s after I heard a friends AR speakers. In a trend that has lasted my whole audiophile life, I invested in amplifiers that would drive difficult speakers. After I got my Advents I bought the biggest Marantz receiver they made (2325). Then I upgraded to an Adcom GFA 555.

When I upgraded the Advents in the early 90’s I listened to over a dozen models and I definitely preferred the less sensitive candidates. I settled on a pair of Mirage M3si which have an 87 db sensitivity. Then I upgraded my amp to a Krell KSA 300S. A few years ago I snapped up a pair of Thiel CS6 that a friend had for sale. These speakers driven by my monster Krell make some of the best sound I have ever heard anywhere.

When I went to AXPONA and the Tampa Show in 2018 I realized that I seemed to prefer speakers with lower sensitivity over those that were very sensitive. I didn’t hear a setup using a single ended tube amp that I lusted after. And I concluded that horn speakers aren’t my thing. They do some things very well but overall they just didn’t light my fire. But I can completely understand why some people love them.

My point here is that the sound resulting from the tradeoffs that low sensitivity speakers incorporate appeals to me for some reason. For the last 40 years I have been willing to invest in the amplification to drive these speakers and I’ve never regretted my decisions. Bottom line, high sensitivity or low sensitivity is not better or worse, it’s one of the many design decisions that speaker engineers make. Once they go a certain direction they optimize their design for the sound they want and sometimes that leads to low sensitivity and low impedance. I happen to be one of those audiophiles who is willing to suffer the cost and back problems of having an amp that will drive these things.

@erik_squires , thank you very much for that information on Siegfried Linkwitz's tone burst tests!    

I was aware of the article in Stereophile years ago which "debunked" short-term thermal compression, but the methodology in the test was flawed because it looked at the average compression over time, rather than the rapid-onset compression that Linkwitz's test reveals.    

"Bigger voice coil, more ventilation, lower power dissipation result in lower dynamic compression."    

That's my understanding as well, but JBL went a step further in their M2 studio monitor:  They use an alloy in the woofer's voice coil whose resistance stays essentially constant as it heats up.  I'm not sure whether they did this for the compression drivers' dual voice coils as well.  Anyway that seems to me like a brilliant idea which would be especially welcome in high-end audio speakers where efficiencies are lower and therefore voice coils are smaller.  

For the record, my own priorities are much more focused on speaker/room interaction, and the types of drivers which do what I want in that area just happen to be fairly high efficiency.  

Duke

That’s my understanding as well, but JBL...

@audiokinesis

Heh, I almost referenced JBL’s work in pro systems, as it’s among the most well documented and easy to find. Interesting 3rd way to skin this proverbial cat.

Also, I can’t type at all!

weather = whether

Also, while I believe it was Dr. Linkwitz, I cannot for sure remember, and I hope he doesn’t haunt me with bad crossover phase matching if I am mistaken in attribution. I do however remember the oscilloscope output very clearly. It was quite convincing.

While I do not need anywhere near JBL monitor style output, choosing tweeters with high power handling and very low measurable compression was a big goal for me.

I should point out that we should not attribute thermal compression to what might also be bad acoustics. Very reflective environments will have similar audible results, in at least as similar as you can type about them. A lot of bad / compressed treble complaints I’ve seen on audiogon were addressed with better room treatments. Was it excess reflection, or better treble/bass balance, or did the improvement in sound quality lead to turning down the knob, therefore reducing tweeter power dissipation? Really hard to say unless we are measuring. I sure could not explain in words how to hear a difference. :)

Best,

E

@erik_squires wrote: 

" I should point out that we should not attribute thermal compression to what might also be bad acoustics. Very reflective environments will have similar audible results, in at least as similar as you can type about them. A lot of bad / compressed treble complaints I’ve seen on audiogon were addressed with better room treatments. Was it excess reflection, or better treble/bass balance, or did the improvement in sound quality lead to turning down the knob, therefore reducing tweeter power dissipation? Really hard to say unless we are measuring. I sure could not explain in words how to hear a difference. :)" 

Your observation makes total sense to me. 

Dynamic contrast can be viewed as a "signal-to-noise-ratio" thing, and to the extent that undesirable/excess reflections raise the effective in-room "noise floor", they reduce the system's dynamic contrast.  I suspect this may be more common and/or often of greater audible significance than the short-term thermal compression revealed by those tone-burst tests. 

This "signal to noise" ratio thing has implications for the sense of envelopment as well:  The further down in level we can still detect the reverberation tails on the recording, the stronger the perception of the recording venue's hall ambience.  (This isn't the only thing that matters for "envelopment" to take place, but imo it's one of them.)  

The ear/brain system classifies reflections as such based on their spectral content, so imo it makes sense for absorption to be broadband, such that the spectral balance of the reflections is largely preserved (assuming they were spectrally correct to begin with).  If the spectral content of the reflections is skewed too much, they are no longer classified by the ear/brain system as "signal", and so they become "noise". 

Duke

Greg Timbers:

Q: How has the sound of speakers changed over the years? Many yearn for the speakers of the past over those of today… what has changed? Distortion, materials, focus on sound characteristics?

A (by Mr. Timbers): Speakers have generally become smoother, more 3-dimensional and much smaller. This means that they are less dynamic on the whole and rather toy like compared to good stuff from the 60s and 70s. Unlike electronics, miniaturization is not a good thing with loudspeakers. There is no substitute for size and horsepower. Nothing much has changed with the laws of physics in the last 100 years so what it takes to make dynamic life-like sound is unchanged. There have been some advances in magnet materials and a bunch of progress in adhesives but not much else. The cost of a 70s system in today's economy would be considered unaffordable and the system would be deemed unnecessarily huge. The large highly efficient systems of old came at a time when 15 – 30 watts of power was the norm. Today's stuff would choke on those amplifiers. Now that power is cheap, size and efficiency has been thrown out the window because you can always apply more power. Unfortunately, more power does not make up for lack of efficiency. Today's speakers range between 0.1% to maybe 0.5% in efficiency. (On a good day) 60s and 70s stuff was more like 1% to 10%. With most of the losses gong to heat, turning up the power on a small system with small voice coils and poor heat management is definitely not equivalent to a large high efficient speaker.

It is true that the response of many of the old systems was a bit ragged and generally less attention was put in the crossover networks because simplicity generally means higher through-put. However, the big Altec's, JBL's, Klipsch's and Tannoys of the day would still fair well today with a little modernization of the enclosures and crossovers.

Today's multi-channel home theater setups let a bunch of small toy loudspeakers and a sub or two sound pretty big and impressive to the average Joe. I think speakers have mostly become a commodity and small size and price are what counts the most now. The few high-end brands left are struggling for market share in this age of ear buds.

https://positive-feedback.com/interviews/greg-timbers-jbl/