A Broad Discussion of Speakers with Major Audio Luminaries

[Jack B]

This has been one of the dilemmas in psychoacoustic investigations - differences can be heard (the phenomenon is "real") but preferences are not statistically reliable (the phenomenon is common in everyday life, and it is at least somewhat normalized). We live in rooms and reflected sound is part of everything we hear, even conversing across a table distorts the amplitude and phase of voice sounds, ever changing as we move around, leaning forward or back, standing, sitting, etc. Measurements indicate horrendous acoustical interference effects - amplitude and phase variations - but we are not conscious of any of them.

In recordings all these variables get "fixed" in time, we have no means of separating what is a characteristic of the sound source from that which has been added by the recording environment or the playback apparatus. The recordings are not binaural, dummy head, with head-movement-compensated playback, allowing us perceptually to perceive the sound source in its environment. The direct sound from the source to the mic and all reflections are simply added together. So we end up having discussions of the present kind.

An ABX test can reveal whether there is an audible difference. It is blind, so the result can be trusted. But it does not scale the magnitude of the perceived difference. It is there, but how significant is it in real world listening contexts? That is a much more difficult question to answer. The "laboratory" demonstrations use signals deliberately selected or electronically generated (like clicks or impulses) to magnify any possible audible effects, These are as "fast" as any real or synthesized kick drum, but they may or may not duplicate the spectrum of that signal. The perception may be different, but the effect, if there, should be audible. Then the question is: which one is preferable? That is a different question and it introduces the further question of what did it sound like to the creators? It is art.

All this brightens many an otherwise dull day . . .

Dr. Toole, your insight and wisdom will Always brighten my day.

 

[Jack B]

In the ballpark of 93dB, but that naturally comes with a gradually-deployed high-pass filter, increasing the lower extension to 55Hz at full throttle. It was not my favorite bass in terms of quality, with a hint of boominess, nevertheless impressive.



It is not only highpass filters of dynamically increasing cutoff frequency, but also some narrow band-selective limiters (reducing the bands which cause highest excursion), soft-knee compressors or alike to make the bass ´fatter´ over time before the system runs out of power of excursion capacity. Most of such systems seemingly rely on passive radiators, not closed or vented box designs.



Interestingly, I see more and more ´non-traditional-hifi´ consumers tending to active speakers, oftentimes with built-in network capabilities. Interestingly, the majority of such popular products (like B&O, Bose, Sonos, Blusound, KEF, Technics, Marantz, Devialet etc.) relies on either closed-box designs with a whole lot of power, or vented boxes. Both is coming with certain limitations in very compact designs, and seemingly use dynamic DSP only to a certain degree, so I never really met an impressive performance-to-size ratio.

As all of these components used in portable speakers, exist in the OEM sphere and are seemingly not as expensive (otherwise they would not end up in $200 or $300 products), I wonder why they are not more frequently used in more expensive yet compact active stereo speakers for home use.

?Maybe for the same reason that "hi-fi purists" eschew such things as tone controls?

 

[livinon2wheels]

Most audible resonances in most loudspeakers originate in transducers. Cabinet bracing is part of competent design, using scanning laser vibrometers to identify vibrations that radiate sound - not all do. The knuckle test does not work. Heroic cabinet materials and elaborate bracing schemes are mostly marketing handles.

Parametric equalization based on anechoic data can effectively eliminate audible resonances in loudspeakers. In-room curves cannot provide the evidence. This is why active loudspeakers, incorporating DSP are advantageous.

However, steady-state room curves are the definitive evidence for identifying and attenuating room resonances, which everybody deals with and which account for about 30% of our overall sound quality ratings. Rooms are arguably the weakest link in the sound reproduction process, and I am not talking about reflections.

I think it is fair to say that all countries have done their share of stuffing boxes with drivers and inventing stories to sell them. Several countries have also made some very fine, neutral loudspeakers. Thanks to the Canadian taxpayer supporting the NRC effort and HARMAN International continuing it - both allowing the research to be published for the world to see - there are now clear guidelines for designing timbrally neutral loudspeakers. That some companies do it better than others is a measure of engineering competence. If others choose to ignore the science - it is a free world and business is business. The scientific facts are real and will not go away.

But it is evident from Amir's and Erin's excellent measurements, and others to be found on www.spinorama.com there are many loudspeaker manufacturers the world over who are not only aware of the guidelines but who are following them. The average sound quality of loudspeakers is definitely going up. Unfortunately, we are still saddled with stereo as the default medium - if one is speaking of weak links.

I'm pleased you are enjoying my book. The 4th edition will be quite different, with new insights.

Dr. Toole, I have read most of your book with thankful thoughts for your efforts. It is perhaps the most common sense approach to understanding all the things that go into making a sound system approach the reality of the recording session. That said, I wonder if you have had the opportunity to listen to speakers produced by a little company in Utah called Tekton. And if so what does your educated ear think about their products?

 

[RexrothPigeon]

Dr. Toole, I have read most of your book with thankful thoughts for your efforts. It is perhaps the most common sense approach to understanding all the things that go into making a sound system approach the reality of the recording session. That said, I wonder if you have had the opportunity to listen to speakers produced by a little company in Utah called Tekton. And if so what does your educated ear think about their products?

Have you seen this?

Tekton Troubadour Speaker Review

Tekton Troubadour Speaker

www.erinsaudiocorner.com

 

[livinon2wheels]

Aside from the speakers performance in the clip you posted above, I find the creator's behavior who requested the above review to be done by Erin to be a bit of a problem. I have always maintained if you offer equipment up for review and testing you need to put on your big boy panties and accept what the reviewer says because, hells bells, you asked them to do it. If you cannot accept that some tester might actually not like it, then don't seek reviews. Just my two cents. But since this has happened now at least twice that I know about and possibly more...it calls into question all the glowing reviews done on their products and makes me want to seek out an unapologetically honest review of their larger products. If all of these positive reviews out there about their speakers were somehow spot picked for their positivity and glowing recommendation, we as consumers need to be apprised of this fact so we can make our choices accordingly. I am trying to get to the truth of the matter before buying or not buying. So far, I am no closer to the answer than I was two weeks ago.

 

[amirm]

I find the creator's behavior who requested the above review to be done by Erin to be a bit of a problem.

A bit? He threatened to sue me and Erin. And had made the same threat against another reviewer who sadly took down that review.

Here is my review of one of the Tekton speakers that led to that. https://www.audiosciencereview.com/forum/index.php?threads/tekton-m-lore-speaker-review.48732/

 

[livinon2wheels]

I was unaware of the extent of the problem between you two Amir. I knew there had been a threat but didn't know from whom the threat came. Now I am putting 2 and 2 together. You have given me confirmation of the extent of the problem and I cannot express my disbelief at the reaction. Even if your review had been overly negative ( I have not read the review as of yet ) there is no reason to threaten lawsuit over a review. It is simply an opinion expressed by one person that he apparently sought out. Be careful what you ask for, right? Ok just went and scanned thru the review and I can see why did not give it a favorable review. My opinion is, if anyone cares, that if you want better reviews, make a better speaker. Good reviews, like many things in life, are earned, not just given away

 

[respice finem]

@amirm Which would, for me, be reason enough to avoid the brand altogether.

 

[RexrothPigeon]

I was unaware of the extent of the problem between you two Amir. I knew there had been a threat but didn't know from whom the threat came. Now I am putting 2 and 2 together. You have given me confirmation of the extent of the problem and I cannot express my disbelief at the reaction. Even if your review had been overly negative ( I have not read the review as of yet ) there is no reason to threaten lawsuit over a review. It is simply an opinion expressed by one person that he apparently sought out. Be careful what you ask for, right? Ok just went and scanned thru the review and I can see why did not give it a favorable review. My opinion is, if anyone cares, that if you want better reviews, make a better speaker. Good reviews, like many things in life, are earned, not just given away

We'd all better be careful what we say or he might send his lawyers after us!

/s

 

[Arindal]

Maybe for the same reason that "hi-fi purists" eschew such things as tone controls?

Sounds implausible to me, as similar kind of DSP hardware and routines like limiter and dynamic bass boost as well as powerful amps, are in fact implemented in some compact active home speakers. They are just combined with certain bass drivers and enclosure concepts (CB or vented) that the outcome is not as impressive.

I wonder if you have had the opportunity to listen to speakers produced by a little company in Utah called Tekton. And if so what does your educated ear think about their products?

I am not Dr. Toole, have not heard the speakers in question, and I am in general cautious with preemptive assumptions on sound quality solely based on measurements. But in this case I would assume that something is deeply flawed with the design in general, well recognizable in Erin's graphs. Positioning several tweeters and midranges operating at short wavelengths with horizontal offset or quite some distance between each other´s diaphragm leads to all sorts of funny effects.

 

[Newman]

there is no reason to threaten lawsuit over a review. It is simply an opinion expressed by one person that he apparently sought out.

As I recall Tekton's threat was over Amir's measurements. I don't recall him threatening to sue Amir for his opinions. Just FYI.

 

[Raya]

Something to remember is that the eardrum/3-bones system is a high pass filter itself that acts much like (assuming stapes reflex is not activating) a first order highpass filter with its knee at about 600 to 700 Hz, person depending.

This very serious attenuates very low bass signals, under 100Hz or so (well, it works above that, of course, but when you get under 100Hz or so, and it's still dropping at approximately 6dB/octave, the attention builds up very fast, obviously.

With very, very low frequencies (say 10-20Hz narrowband noise) and a clean (large volume enclosure with a huge driver, we built two a while ago, but we don't find any practical use) subwoofer, you can feel the pressure change on your chest and abdomen well before you even realize it's a sound you're hearing. Such signals may or may not be bad for you, but they don't even get to the cochlea in any substantial way.

Most subwoofers also create audible harmonics, you really can't do much with a smaller enclosure, even with positional feedback, as far as I've seen, to prevent that. Consider, for instance, a run of the mill 15" dayton "max" sub. Put it in a 15x15x15 enclosure, and you find that the interior volume changes enough during extension and compression (way over the 120 to 140dB SPL limit for linearity in air) to make an even order distortion system. This is why a lot of the "small, powerful" subwoofers can be quickly located, which should not be the case, because of audible harmonics above 90 hz or so. Even if most of the distortion is below 90 Hz, if the phase of the harmonics lines up on the cochlea, the CNS manages to help you locate this. (note, this is not like a 'steady tone' at one frequency, which isn't going to 'locate' anything, nor is it a variation in phase across the two ears, which again is audible, but which does not appear to provide directional sensation, only spatial sensation)

Yeah, people are complicated.

As to "loudness" (meaning the sensation level, not the power in the soundfield, please), adding harmonics is a way to increase the loudness of anything quite substantially. While low frequency bass may not be too terrible for the ear, high loudness means you are exercising a LOT of inner hair cells, and that does appear, although I have no clinical examples, to be bad for your continued hearing. I don't know any really clear work on this, annoyingly. Lots of confusion between effects, time exposure, etc, but not great data to grab on to.

Oh, and Floyd, indeed the "snap" in the forest is a classic example of how our auditory system is set heavily to the "detect more events, and therefore making more false events happen" side of things, probably because ducking when it's not necessary costs very little in evolutionary terms, and not ducking when the club is coming down can be extremely, um, painful, at least.

Edited to add about LF effects:

Oh, and to low frequency SPL: Consider barometric pressure changes. Yes, those are milliHz or microHz frequencies, but consider how big those change are. If you remember, approximately 194dB SPL is "1 atmosphere" amplitude. Driving from Estes Park Colorado to the Rocky Mtn National Park visitor center at the top is about a 3PSI change, if I recall correctly (it certainly lacks enough O2 for this human, let me tell you, wheeze wheeze). https://www.mide.com/air-pressure-at-altitude-calculator note, check your units FIRST!

3/14.7 = .2 .2 is about -6 db. If you didn't have your ear drum and eustachean tubes, you'd be dealing with a constant 188 dB stimulus at about 1/3600 Hz. Yeah, that eardrum is a useful thing, that.

Oh- this is new to me! “120 to 140dB SPL limit for linearity in air”
Could you please clarify? Is this a physics of sound thing I am unaware of, or a biological limit?

 

[j_j]

Oh- this is new to me! “120 to 140dB SPL limit for linearity in air”
Could you please clarify? Is this a physics of sound thing I am unaware of, or a biological limit?

Physics. Air is not a linear medium when driven hard enough.

 

[Newman]

PV=nRT

(the lines are isotherms)

 

[bmc0]

PV=nRT

Additionally, sound speed depends on pressure which causes cumulative, frequency-dependent distortion as the wave propagates. The faster-moving peaks "pile up" against the troughs, gradually distorting the waveform toward a sawtooth-like shape (also known as a shock wave).

 

[j_j]

Additionally, sound speed depends on pressure which causes cumulative, frequency-dependent distortion as the wave propagates. The faster-moving peaks "pile up" against the troughs, gradually distorting the waveform toward a sawtooth-like shape (also known as a shock wave).

That's only at high levels. Various references report 140dB or 120dB, but use different standards for "how much distortion". I know that for a while we had a cavity designed at Bell Labs to actually create mass flow at 140dB SPL at about 400Hz. It would blow fluff around in a circle inside the contraption rather spectacularly. It had an old Altec 4-ohm, 4 inch phenolic diaphragm horn driver pushing it, and push it did! Had to run about 10 watts into the driver.

Horn throats often have much higher levels than the actual output at the horn mouth, that's why they call them "compression" drivers, and some of that is perhaps thought to be the "horn sound", although resonances could be involved as well. (I vote for more resonances except at high level with Altec and JBL drivers.)

On the other hand, air pressure is secondary in terms of speed of sound to temperature, which can create remarkable differences between -10C and 30C.
Humidity also plays a role, but more in dispersion.

https://sengpielaudio.com/calculator-speedsound.htm is handy that way.

-10C is about 225 m/s
30C is about 349 m/s

Which is a big difference indeed.

Humidity has more effect on high frequency propagation.

at 20C, 0% humidity, 10,000 Hz 1.7 dB/100 meters
at 20C, 20% humidity, 10,000 Hz, 24 db/100 meters

Calculation method of absorption of sound by atmosphere air damping dissipation absorbtion high frequencies attenuation sound during propagation outdoors outdoor - sengpielaudio Sengpiel Berlin

Damping of air of high frequencies acoustics calculation of absorption of sound by the atmosphere outdoor absorbtion - Eberhard Sengpiel sengpielaudio

sengpielaudio.com

Air is far from a perfect propagation medium.

 

[bmc0]

That's only at high levels.

Yes, I thought that was clear enough but I could have specified.

Horn throats often have much higher levels than the actual output at the horn mouth, that's why they call them "compression" drivers

True, and the propagation distortion I mentioned is often the dominant source of nonlinear distortion in HF compression drivers above a couple kHz.
I agree that resonances being more significant than nonlinear distortion in so-called "horn sound" at domestic levels is probably correct. Compression drivers in well-designed waveguides/horns can sound very good despite their rather high 2nd harmonic.

 

[j_j]

True, and the propagation distortion I mentioned is often the dominant source of nonlinear distortion in HF compression drivers above a few kHz.
I agree that resonances being more significant than nonlinear distortion in so-called "horn sound" at domestic levels is probably correct. Compression drivers in well-designed waveguides/horns can sound very good despite their rather high 2nd harmonic.

Yes. Because of the nature of air, the first distortion is 2nd order, which also causes some mass flow that can 'decenter' the driver if it's not properly handled. Some 2nd order distortion in a bandlimited system isn't too bad. The "resonance" thing came directly from the A7. Imagine that!

 

[bmc0]

Some 2nd order distortion in a bandlimited system isn't too bad.

The frequency dependency also means that difference tones become lower in level as their frequency decreases (20dB/decade) which probably helps reduce audibility vs a non-frequency-dependent nonlinearity.

 

[dagfinn]

75-80dB SPL (which equates to 96db SEL).

This is totally wrong and misunderstood by me. Thanks to @Thomas Lund for clearing that up.