I had a little high sensitivity loudspeaker epiphany yesterday

mhardy6647

So, I rose to the bait in a thread Someplace Else (ahem, AA, ahem) on the subject of open baffle loudspeakers (which I am not even particularly enamored of) -- more to the point, a sub-discussion about sensitivity vs. efficiency as a measure of loudspeaker performance.

One of those things where I knew better than responding once -- but then I responded to another response, and again, and... well, what can I say? I get like that sometimes.

The two parameters do address the same interesting characteristic of a loudspeaker -- how much do you get out for what you have to put it? Sort of like MPG for an I/C engine automobile. I quipped that SPL (which, in all seriousness, is probably easier to intuit and more meaningful in the great scheme of things) probably won out over efficiency in specs because the measured numbers in the former case just look better. 90 dB SPL (at 1 meter for 1 watt input power) sounds like a lotta SPLs. Spec'ing the same speaker's efficiency as (ca.) 0.3% sounds a whole lot less impressive.

But then, finally, I got to thinkin' about efficiency. A hifi enthusiast may be all thrilled about the SPLs s/he can get out of his/her big fancy 85 dB sensitive speakers with his/her 1000 wpc amplifier. Concert hall realism! Sledgehammer dynamics! Thrilling soundstage! Transparency! This rhetorical loudspeaker has an efficiency of -- about 0.2%.

... and that means that, of those 1000 watts goin' into it, 2 watts' worth of sound is coming out (which is, make no mistake about it, a lotta sound!). But those other 998 watts? They're being dissipated as heat by the VCs of the drivers and the crossover components. They are wasted watts.




source: https://community.klipsch.com/index.php?/topic/112812-speaker-sensitivity-and-speaker-efficiency/

Efficiency is independent of SPL output (at least in theory!). It just is what it is. Listenin' loud, listenin' soft, 98% of the amplifier power goin' into the loudspeaker is being just plain ol' wasted in a speaker with 85 dB sensitivity.

Given that, it's kind of remarkable that Yankees perfected the acoustic suspension loudspeaker, isn't it?

lightman1

Still snowed in, Doc?......

mhardy6647

No, it was nice this weekend -- but Mrs. H is co-leading a birding trip down in Texas. Why, could you tell?

audioluvr

lightman1 wrote: »

Still snowed in, Doc?......

LMFAO!

verb

So Doc I'm thinking about this efficiency thing, and I look at the mass of the moving parts of the speakers.

Is it just the materials Klipsch chooses to use (less weight) which would be easier to drive? Can't be the whole story.

VC or enclosure design?

Are their drivers fundamentally that different from the rest of the industry?

dago

Doc,
I have a little theory of my own, which is kinda like yours, but in reverse.

Take a 2 watt flea amp and put it on some 85 efficient speakers and see what you get. Better yet, make it multiple driver big speakers at 85 efficiency rating and slap 2 watts on them.

Claiming 998 watts are wasted is a bit of a stretch. Just sayin'....

Theory is just that, theory....real world applications differ at times. Besides, you should be thinking in current, not watts.

kharp1

Its interesting to look at individual specs and debate what it means and what it translates to, and, we can all have our favorite spec we look at first, or favor, as some sort of tell-tale, but, I like to think it it all matters in the grand scheme.

How does the amp match with those super efficient speakers...do they sap the control of the amp? So many things come in to play when talking about audio components, or, electrical circuits in general.

As always, thanks for the in depth break down. Always good info to ponder from mhardy.

dago

The chart doesn't say if they were using sine waves as a measuring stick, or actual music, big difference.

F1nut

You should all know by now that you need 200wpc no matter what.

Clipdat

F1nut wrote: »

You should all know by now that you need 200wpc no matter what.

Yeah. *eyeroll*. That couldn't be further from the truth.

That 200wpc bs is some of the worst audio related advice I've ever read, proudly proclaimed in countless posts in various threads on this forum. What a huge disservice to casual readers/lurkers or people trying to get into the hobby.

BlueFox

Clipdat wrote: »

F1nut wrote: »

You should all know by now that you need 200wpc no matter what.

Yeah. *eyeroll*. That couldn't be further from the truth.

That 200wpc bs is some of the worst audio related advice I've ever read, proudly proclaimed in countless posts in various threads on this forum. What a huge disservice to casual readers/lurkers or people trying to get into the hobby.

Really? That bad?

Clipdat

BlueFox wrote: »

Really? That bad?

Yes. Jesse and I are on the same page here. We're talking about a certain member who likes to proudly preach that you need at least 200wpc.

mhardy6647

... and who is relatively unlikely, I reckon, to click on this thread



So, I'm glad to see some chatter here! The issue on the table is philosophical -- reproducing music requires work (in the physical science sense of the term) to be done. The bulk of that work may be done by the amplifier or by the transducer (loudspeaker). In truth, early in the history of sound reproduction by electronic amplification, amplifier power was expensive and limited; it is now cheap. The former restriction required efficient loudspeakers; the latter permits inefficient loudspeakers. The philosophy of designers of the former is quite different than the latter, even though both should pursue the same goal (real-sounding reproduction of acoustic waveforms, particularly music)!

It is completely possible to product outstanding sound by either approach; and the dynamic range of sound that the human auditory system can cope with means that even efficient loudspeakers require a fair amount of power on tap to produce real sounding (as opposed to realistic) dynamics.

I would liken the philosophical argument to automobiles. There is a place for the Dodge Hellcat, but also for the Caterham Seven* (or a Morgan, if you prefer)... and both are niche products. Most folks are happy with a Camry

______________
* Sticking strictly with the efficiency metaphor, perhaps a better comparison would be the Hellcat and a Tesla Model S.

dago

mhardy6647 wrote: »

... and who is relatively unlikely, I reckon, to click on this thread



So, I'm glad to see some chatter here! The issue on the table is philosophical -- reproducing music requires work (in the physical science sense of the term) to be done. The bulk of that work may be done by the amplifier or by the transducer (loudspeaker). In truth, early in the history of sound reproduction by electronic amplification, amplifier power was expensive and limited; it is now cheap. The former restriction required efficient loudspeakers; the latter permits inefficient loudspeakers. The philosophy of designers of the former is quite different than the latter, even though both should pursue the same goal (real-sounding reproduction of acoustic waveforms, particularly music)!

It is completely possible to product outstanding sound by either approach; and the dynamic range of sound that the human auditory system can cope with means that even efficient loudspeakers require a fair amount of power on tap to produce real sounding (as opposed to realistic) dynamics.

Now there is the Doc I know.

Yes reproducing music, not sine waves, takes work, current, if we are talking inefficient speakers. Getting multi-driver big inefficient speakers to start and stop on a dime turning those dynamic transient responses found in music takes some juice.

Very efficient speakers take little, especially single driver speakers like horns. There is a place, and application for everything in audio, from 2 watt flea powered amps, to the monster 1000 watters.

Claiming that 998 watts is wasted, without the specific parameters used, is a bit misleading in my book, if we are to take that chart at face value.

mhardy6647

dago wrote: »

mhardy6647 wrote: »

... and who is relatively unlikely, I reckon, to click on this thread



So, I'm glad to see some chatter here! The issue on the table is philosophical -- reproducing music requires work (in the physical science sense of the term) to be done. The bulk of that work may be done by the amplifier or by the transducer (loudspeaker). In truth, early in the history of sound reproduction by electronic amplification, amplifier power was expensive and limited; it is now cheap. The former restriction required efficient loudspeakers; the latter permits inefficient loudspeakers. The philosophy of designers of the former is quite different than the latter, even though both should pursue the same goal (real-sounding reproduction of acoustic waveforms, particularly music)!

It is completely possible to product outstanding sound by either approach; and the dynamic range of sound that the human auditory system can cope with means that even efficient loudspeakers require a fair amount of power on tap to produce real sounding (as opposed to realistic) dynamics.

Now there is the Doc I know.

Got that first cup of coffee onboarded, that's why

Yes reproducing music, not sine waves, takes work, current, if we are talking inefficient speakers. Getting multi-driver big inefficient speakers to start and stop on a dime turning those dynamic transient responses found in music takes some juice.

Very efficient speakers take little, especially single driver speakers like horns. There is a place, and application for everything in audio, from 2 watt flea powered amps, to the monster 1000 watters.

Claiming that 998 watts is wasted, without the specific parameters used, is a bit misleading in my book, if we are to take that chart at face value.

It does indeed. It's just reflecting on what actually happens to most of that juice that got me... musing. Loudspeakers are transducers, changing electric power into acoustic power. It is really, truly, true. Just as in a Carnot Cycle engine (e.g., your basic Hemi), any power not invested in useful work is lost as heat (in the broadest sense -- wasted kinetic energy). Therodynamics. Itsa da law. (to paraphrase Beakman).



EDIT: Full disclosure -- a single ended, direct heated triode amplifier is pretty darned inefficient, too! My stereo SE 2A3 amp consumes about 130 watts and puts out about 7 watts from the speaker outputs. That's an efficiency of 5.4% Quite a bit better, though (one or two orders of magnitude), than, say, [EDIT] a Wilson Audio Sofia.
https://www.stereophile.com/content/wilson-audio-sophia-series-3-loudspeaker-measurements

In all seriousness, yes, absolutely --one can get there (hifi Nirvana), either way. Taste, and philosophy, are only factors -- road signs along the path.

mhardy6647

Work transfers energy from one place to another or one form to another.
In physics [not just in physics!], power is the rate of doing work, the amount of energy transferred per unit time.
The unit of power is, then, joules [the SI unit of energy] per second.
However, we usually refer to a one joule per second as the “watt.”

adapted from https://www.quora.com/What-is-the-relationship-between-work-energy-and-power (because it was handy!)

When it comes to electricity, Power = voltage x current (if the "power factor" is 1)
The load impedance factors into the relative need for voltage (E) vs. current (I) according to Ohm's Law.
E = I * R (R is "impedance" in the case of AC waveforms, i.e., music!)

The relationship between acoustic power and SPL (i.e., volume... which is the end game when it comes to loudspeaker work) is actually, kinda sorta, deterministic.

The big difference is that power is an absolute kind of thing; intensity (in this case, SPL) varies with distance.

It is written:

Sound power or sound power level has nothing to do with the distance from the sound source.
Thinking helps: A 100 watt light bulb is emitting constantly the same power.
That is really the case - no matter if in 1 m, in 10 m, or even in 100 distance.
These emitted watts don't change with distance. They stay in the source.
Sound power is the distance independent cause of this, whereas sound pressure is the distance-dependent effect.

source: http://www.sengpielaudio.com/calculator-soundpower.htm

Rule of thumb: A full-scale symphony orchestra (think: Beethoven's Ninth Symphony scale) playin' at full tilt (what's that? fffff?) produces about 1 watt of acoustic power. The SPL in a concert hall, of course, will vary depending upon the distance of the measuring gizmo from the orchestra.

mhardy6647

I enjoyed this.
YMMV>

https://www.galaxyaudio.com/education/efficiency-vs-sensitivity

K_M

verb wrote: »

So Doc I'm thinking about this efficiency thing, and I look at the mass of the moving parts of the speakers.

Is it just the materials Klipsch chooses to use (less weight) which would be easier to drive? Can't be the whole story.

VC or enclosure design?

Are their drivers fundamentally that different from the rest of the industry?

They use drivers that are similar to or much closer to "Pro sound" drivers. With all the compromises and attributes.

Klipsch Heresy, low excursion, lacks deep bass, but has highish efficiency.
Eminence (pro-sound) woofers are often recommended as upgrades to the stock woofer in these, as they have similar efficiency etc.

Cerwin Vega, MTX, Peavey, Some EV stuff also similar.

mhardy6647

http://techtalk.parts-express.com/forum/tech-talk-forum/56544-do-crossovers-get-hot/

As Dirty Harry Callahan might say:

Now, you've gotta ask yourself one question. Now why did that crossover get that hot? Go ahead, punk. Make my day.

motorstereo

Good question; how does a crossover get destroyed like that? I had a pair of 103db efficient Peaveys that also had one crossover that looked similar to that one..... burned beyond recognition. My guess is alcohol, high powered pro amp and damaged hearing in pretty much that order.

ALL212

Looks like the sandcast resistor had an issue...

I've rebuilt a couple pair of Dahlquist DQ-10's. It wasn't uncommon to find a couple of those resistors had overheated, 4 ohm 15watt wire wounds. I had one pair that had almost burned through the crossover base. In one extreme case the inductor formers had bubbled and melted.

Is this due to the amp being over driven into clipping and DC being present on the board? Or just a very high powered amp running Van Halen's Eruption?