Interview about Measurements with Pearl Sibelius Speaker Designer

[Mr. Widget]

I own a pair of Sibelius speakers. They are excellent, with a very flat, neutral "uncolored" response and an incredibly detailed soundstage. The sound is natural and musical without any hint of brightness or distortion at all frequencies (down to 38hz). I think it's the absence of a crossover, a great full range driver, and the finely tuned solid 1 1/2" French Oak cabinet that allows you to hear all the details, even at low volume. I listen to a lot of rock and jazz, as well a some classical, and can say that they sound fantastic on all types of music. As long as you aren't looking for front-row rock concert volume, they wont disappoint.

I appreciate your chiming in. I realize your comments are purely subjective, but at the end of the day, speakers are built for listening. Measuring them is critical for speaker designers and great for reviewers, but I am sure many here have found devices that measured better than another and yet were a disappointment. Subjectivity is not useless.

 

[ctrl]

but I am sure many here have found devices that measured better than another and yet were a disappointment. Subjectivity is not useless.

It is quite possible that a speaker with very good measurement results sounds subjectively worse to you than a less well-designed speaker with better fine tuning.
The well designed speaker should be relatively easy to fix with a little EQ - the opposite case would be much more difficult or impossible to realize.
Therefore, it is always an advantage if the speaker designer has so much experience and knowledge to realize both (good subjective sound and good objective measurements), because then the speaker is most flexible to use.

More details about the design process of a loudspeaker and why complete measurements are important (using the example of SP and PIR) can be found here in the discussion of an interview with the Dynaudio designer.

One problem, however, is how "better measurement" is defined. Unfortunately many equate a flatter on-axis frequency response with "better", which is total nonsense if the off-axis behavior of the speaker is not known (if we exclude obvious things like a 10dB hump or similar).
Also in the conversation, it seems like both of them are always talking about on-axis FR, which is not enough to describe a speaker, especially a single drive unit speaker.

One can point this out a hundred times (this was one reason for the introduction of the CTA-2034-A standard) in the next discussion it will be said again there is a flat measuring speaker that did not sound good! Gotcha!

And I think Harley was simply saying that once he found what he felt was the best balance between neutral and frequency extension he considered his speaker ready for the market.

From the designer's point of view, this is certainly an understandable position.
He also said:

yes i'm applying to science, so when mark designed our drive cone for our loudspeaker ... there are nine parameter we took into account...but there comes a time when you have to stop and actually you build your enclosure and then you use your ears...

I found this a bit strange, because after the selection of the driver, the real design work begins and you simulate which enclosure shape and driver position is as optimal as possible and to be able to predict how which changes will have an impact. Only then the first prototype is built. But maybe he just forgot to mention this.

and compared two completely different things:

...there is no violine maker...or flute marker or guitar maker that goes into an anechoic chamber with an oscilloscope make sure that everthing is flat.

How wrong this analogy is does not need to be explained further.

There is already a slight antipathy to measurements expressed, also in his anecdote about the design of a speaker with the best possible flat frequency response that sounded like rubbish.
This all sounds a bit like an old-school designer for whom nothing else exists besides the on-axis FR which serves as a reference point and one can only trust your own ears - which is not wrong, but does not tap into the potential of today's measurement, software and simulation possibilities.


To demonstrate this, we can simply simulate how the Sibelius will probably measure from about 300-400Hz.
To do this, take the manufacturer's on-axis half-space measurement of the Mark Audio Alpair M10 Gen. 3 (should correspond more or less to the driver of the Sibelius) and simulate the influence of the baffle under free-field conditions (using VCAD software).


The low frequency behavior is not simulated. The Sibelius seems to use a transmission line concept to extend the low frequency reproduction. That is why a comparison is made in the interview of organ pipes, which are also "lambda/4" resonators. Since unwanted resonances from the TL port are always transmitted as well, the FR will turn out more wavy in the low-mid frequency range - beside the extended low frequency range.

Simulated FR for Sibelius deg0-20-40

With this concept, the on-axis frequency response is not decisive for the sound impression in the listening room. If the LS would be tuned to a flat on-axis FR, the LS would sound lifeless and dull, because then SP and PIR would drop too steeply to high frequencies from about 4kHz. With complete measurements, we could assess how even the radiation of the loudspeaker is and locate possible frequency ranges to be observed in particular.

The simulations also help assess how changes in enclosure shape or driver position are likely to affect the system (without building a prototype for every design).
normal width or 300mm width

 

[HarmonicTHD]

I appreciate your chiming in. I realize your comments are purely subjective, but at the end of the day, speakers are built for listening. Measuring them is critical for speaker designers and great for reviewers, but I am sure many here have found devices that measured better than another and yet were a disappointment. Subjectivity is not useless.

Subjectivity is valid (and only valid) to the individual. Who is to argue about what one prefers. However many make the mistake of trying to generalize their personal preference and claim without facts that it should be valid for everyone else.

This goes so far that some companies prey on gullible consumers, feeding them unsubstantiated stories and try to get their money for something objectively useless.

 

[Mr. Widget]

This goes so far that some companies prey on gullible consumers, feeding them unsubstantiated stories and try to get their money for something objectively useless.

Shall we discuss IEC power cords? Speaker cables with integrated RLC networks that have all manner unpredictable consequences? There is so much BS out there and millions of dollars being spent on the emperor's new clothes... then again, if it makes the purchaser happy. What's the real harm?

 

[Mr. Widget]

One problem, however, is how "better measurement" is defined.

Agreed... much progress has been made in the last two decades, but even with the most thorough suite of measurements, I don't think we are capturing everything.

Then there is the room. As we all know, a loudspeaker designed using the best science to measure well in an anechoic environment will still sound different in every other room.

And back to subjectivity. At the end of the day, the recording industry doesn't have practical standards. Recordings are made with subjective decisions made by professionals with their own notions of correctness working in different rooms with different systems all over the world. So what is accuracy?


Regarding Harley's comments equating his speaker design with musical instrument building. I have to believe he is speaking metaphorically and not literally. A pipe organ pipe plays one note, and musical instruments intentionally color the sound. He seems to be intelligent enough to understand that. I think he is trying to explain the grosser concepts without losing much of the audience in the weeds. ASR is not his audience.

 

[amirm]

Shall we discuss IEC power cords? Speaker cables with integrated RLC networks that have all manner unpredictable consequences? There is so much BS out there and millions of dollars being spent on the emperor's new clothes... then again, if it makes the purchaser happy. What's the real harm?

That happiness didn't come free. Money was spent on it which could have been put to real use elsewhere. The happiness is also temporary as it has no foundation in reality. You get a temporary high and then it dissipates.

In society we enact laws against many products like above. That we just test products that point out the truth should sit well with everyone. But you disagree?

 

[Mr. Widget]

That happiness didn't come free. Money was spent on it which could have been put to real use elsewhere. The happiness is also temporary as it has no foundation in reality. You get a temporary high and then it dissipates.

In society we enact laws against many products like above. That we just test products that point out the truth should sit well with everyone. But you disagree?

I guess I don't see the difference between buying an expensive watch or a piece of jewelry and buying what you and I may consider ridiculous audio bling. I gather you may think the claims put forth by some manufacturers are verging on criminal.

Testing products and publishing object truths about those products is wonderful and extremely helpful... that said, back in the '70s virtually every ad in the stereo magazines were filled with numbers and specifications. These were often verified by objective third parties, however those specifications and performance capabilities often were of little significance.

I am not suggesting that is the case here, but (this is where we possibly disagree) I do not feel we have yet arrived to a point where we can objectively quantify enough of the performance characteristics of digital or analog electronics or speakers to get the full picture from measurements alone. This is where subjective listening comes in. Ideally in a controlled setting and better yet in a double blind controlled setting. If you have ever spent time in Harman's speaker shuffler double blind room, it is quite an experience and destroys many preconceived notions.

 

[NTK]

If you have ever spent time in Harman's speaker shuffler double blind room, it is quite an experience and destroys many preconceived notions.

Amir had done it twice.

Research Project: Infinity IL10 Speaker Review & Measurements

Too funny, I still have these as side surrounds. They are way too high and mounted on the wall with “pivot” ball mounts so I am able to point them somewhat. I couldn’t tell you what year I bought them but I can tell you it was from Circuit City since I got them at a deep discount. (One wouldn’t...

www.audiosciencereview.com

 

[amirm]

I guess I don't see the difference between buying an expensive watch or a piece of jewelry and buying what you and I may consider ridiculous audio bling.

When you buy a watch or jewelry, you know what you are getting. And said product's effect doesn't disappear a few minutes later. You can wear these for years to come to add beauty and fashion. No one ridicules them either. An audio tweak product that does nothing to your sound, doesn't remotely serve that purpose. Yes, there is some "audio voyeurism" that comes from showing off thick cables and such but hardly anyone would buy them for that strict purpose. And there are plenty of such tweaks that don't look pretty or are even visible.

 

[amirm]

Testing products and publishing object truths about those products is wonderful and extremely helpful... that said, back in the '70s virtually every ad in the stereo magazines were filled with numbers and specifications. These were often verified by objective third parties, however those specifications and performance capabilities often were of little significance.

This site proves the reverse. Abandoning those specifications and verification of the same allowed all kinds of people to get into this business and produce products that should not be there if data and common sense about it existed. The industry has regressed back to wild west selling fool's gold left and right for multiples of real thing!

I recently tested a $20,000 DAC that had the same "ESS IMD Hump" that even cheap DACs have resolved. You are telling me that this is a good thing? If the company had measured it and looked the wealth of data we have other DACs here, the extra distortion would not have been there.

You are also forgetting the fact that objective data allows you to spend far less money to get top class performance. Without us measuring DACs for example, you would have thought that you need to spend thousands of dollars on a DAC when a $150 delivers impeccable performance.

Net, net, we are solving a problem that the industry has created by abandoning objective verification of product performance. Such did not exist in 1970s as sanity still existed in audio.

 

[amirm]

I am not suggesting that is the case here, but (this is where we possibly disagree) I do not feel we have yet arrived to a point where we can objectively quantify enough of the performance characteristics of digital or analog electronics or speakers to get the full picture from measurements alone. This is where subjective listening comes in. Ideally in a controlled setting and better yet in a double blind controlled setting. If you have ever spent time in Harman's speaker shuffler double blind room, it is quite an experience and destroys many preconceived notions.

It is a fallacy that measurements need to provide the full picture to be useful or even critical. Nothing in life is produced that way. Yet, technology advances and adoption is massive in scale. Measurements easily quantify bad products. And put the wind behind performance of a speaker when they are good.

Ultimately audio has a broken architecture in that the capture process does not comply with any standard. So there will never be the case that you fully know what is right when it comes to tonality. Fortunately immense enjoyment can be had without achieving that perfection.

I have been in Harman speaker shuffler room twice. It is a great experience. Fortunately you don't need to be there to follow the research that connected the preferred speaker there with measurements. So many people are blindly buying speakers, headphones and IEMs as a result of our objective work and vast majority are quite happy. This is all we can hope for.

 

[Mr. Widget]

This site proves the reverse. Abandoning those specifications and verification of the same allowed all kinds of people to get into this business and produce products that should not be there if data and common sense about it existed. The industry has regressed back to wild west selling fool's gold left and right for multiples of real thing!

Even back then there was a lot of "wild west" with people designing some pretty whacky solutions to nonexistent problems simply because they could show a graph of it... I don't think times have changed all that much. The vocabulary has changed and perhaps the level of outrageousness has, but a certain portion of the population wants to "believe" and a certain percentage of the population wants to capitalize on that.

Regardless, I think you are misunderstanding me. I am in no way discounting the relevance of objective measurements, but am saying that you should keep an open mind and listen as well as measure.

Talking DACs for example, I think the digital portion of most DACs are essentially identical, but the analog sections are where they differ. This would relate to how we hear (perceive) analog distortion products including phase which is more telling than the percentage of distortion.

 

[Mr. Widget]

Ultimately audio has a broken architecture in that the capture process does not comply with any standard. So there will never be the case that you fully know what is right when it comes to tonality. Fortunately immense enjoyment can be had without achieving that perfection.

I have been in Harman speaker shuffler room twice. It is a great experience.

Here we are 100% in agreement.

Coincidentally I have experienced the Harman room twice myself.

 

[ctrl]

Agreed... much progress has been made in the last two decades, but even with the most thorough suite of measurements, I don't think we are capturing everything.

German rudeness: Of course, we capture everything. The measuring microphone records air pressure fluctuations - that's all there is.

I would agree with you if you mean that we cannot bring the information from the impulse response one hundred percent into agreement with the subjective rating of a loudspeaker.
We obtain 72 impulse responses from the hor and ver measurement of a loudspeaker (at 10° step size). From each measurement we can determine FR, phase frequency response, group delay, decay. Can measure multitone distortions (HD, IMD,...) and measure harmonic distortion separately. Perform compression test,...

I don't know what you did last summer, but I know what you're thinking, "what about sound stage that can't be measured". The information about this is contained in the measurements, the difficulty is to interpret this data. Have explained this here with more details.

Then there is the room. As we all know, a loudspeaker designed using the best science to measure well in an anechoic environment will still sound different in every other room.

Agree with you, but what is the consequence of this? A not well designed ignoring-science-because-no-need-for-measurements speaker will still sound different in every ...
This is a true statement, a truism that is often cited, but ultimately without consequence. In the average of listening rooms, the "better" designed speaker with less "errors", will sound better.

When discussing such statements, the next step is usually to list individual cases or borderline cases where certain speakers are superior, such as a narrow-radiating horn for Elsa's ice palace. I would then agree and say that individual cases do not bring us any further...

I am in no way discounting the relevance of objective measurements, but am saying that you should keep an open mind and listen as well as measure.

Totally agree with you.
I just don't know what you mean by "listen as well", my translation program spits out German words I've never seen before. I have a measurement microphone and speakers, so I make measurements - don't have the slightest clue what else there is to do, maybe do double measurements to be sure?

If, as with the Sibelius, a full-range driver with more than 2-3'' size is used, the on-axis FR may no longer be tuned flat. The listening window, on the other hand, could be relatively flat again. One can not rate such a concept with the standards of a conventional 2- or 3-way LS.

With an open mind, however, one must also name the weaknesses of such a concept, which in the case of the Sibelius, for example, would be the severe break-up resonances above 3kHz. Each resonance has a settling and decay time. It can then take ten or more oscillation periods until the resonance is damped by -30dB.

Here is the infinite baffle CSD measurement of the Alpair 10 Gen. 2:

Source: Hobby Hifi 2011-3

 

[Mr. Widget]

Of course, we capture everything. The measuring microphone records air pressure fluctuations - that's all there is.

True... but consider this analogy. In investigating a crime with blood as evidence, 40 years ago blood type was about the only information available to us. Today we have DNA sequencing as an available tool. Instead of eliminating 40% or a bit more of the population based on blood type, now we can identify an individual.

Today we can study the performance of a loudspeaker way beyond the simple on-axis frequency measurements taken 40 years ago, but the captured air pressure you refer to may hold additional secrets that we are yet to discover. Maybe not, but that is what I meant.

I don't know what you did last summer, but I know what you're thinking, "what about sound stage that can't be measured". The information about this is contained in the measurements, the difficulty is to interpret this data. Have explained this here with more details.

As it turns out I was experimenting with imaging last summer. ;-)

Thanks for the link, it is very interesting! I agree completely that correlation between what we perceive and what we have measured is key. I find it interesting that the industry has told us that time alignment was the key to imaging, or rounded corners of the baffles, or adding drivers for wider dispersion, or tightly controlled dispersion... I am sure that I am missing a few, but at the end of the day while all of these things will affect the imaging to greater or lesser degrees and can be measured in vertical and horizontal FR measurement plots, controlling the reflections in the room are in most cases are even more important.

Unfortunately that is too messy and not always an easy fix. Most consumers want to buy a solution. They want to believe speaker X, or cable Y, or amplifier Z, or power cord X' will solve my problems.

In the average of listening rooms, the "better" designed speaker with less "errors", will sound better.

Absolutely!

I just don't know what you mean by "listen as well", my translation program spits out German words I've never seen before. I have a measurement microphone and speakers, so I make measurements - don't have the slightest clue what else there is to do, maybe do double measurements to be sure?

I guess I wasn't clear. I meant that listening is as important as careful and thorough measurements.

With an open mind, however, one must also name the weaknesses of such a concept, which in the case of the Sibelius, for example, would be the severe break-up resonances above 3kHz. Each resonance has a settling and decay time. It can then take ten or more oscillation periods until the resonance is damped by -30dB.

As you know, every speaker design is a series of compromises. Using a single driver certainly limits options.

 

[ctrl]

us that time alignment was the key to imaging, or rounded corners of the baffles, or adding drivers for wider dispersion, or tightly controlled dispersion... I am sure that I am missing a few, but at the end of the day while all of these things will affect the imaging to greater or lesser degrees and can be measured in vertical and horizontal FR measurement plots, controlling the reflections in the room are in most cases are even more important.

Once someone develops a reliable design concept for "best imaging", he or she will have a competitive advantage

I guess I wasn't clear. I meant that listening is as important as careful and thorough measurements.

Sorry, I thought it was worded sarcastically enough that the paragraph wouldn't be misunderstood even without an irony smiley.
I agree with you one hundred percent and have never said otherwise.

It is so stereotypical that if you think simulations and measurements are the best basis for a good loudspeaker design, it is assumed that listening to the loudspeaker comes too short and people keep reminding you not to forget to listen to the loudspeaker.
In my DIY speaker designs, I usually spend months fine tuning until the XO is fixed.

 

[RickS]

Have always been skeptical about Mark Audio drivers. While @ctrl linked to the driver spec sheet above, one might miss that the posted FR is supplied on a scale that is more than twice the industry standard. For that matter, NO off-axis measurements are shown. Here is the driver on-axis shown with more typical scaling:

Seems worth noting that this driver is not starting out with anything close to flat on-axis. If the off-axis might redeem this driver, would expect that they would be highlighting it in the data sheet. Instead, no measurements are provided. Despite visual appearances, it does have a low fS and claimed Xmax of 7.5 mm. When you start to push it for bass, the large excursions are going to drive up distortions in the upper frequencies though.

So you might be able to coax some bass from it, but there is a fair bit of work to do to improve the response overall and Pearl Acoustics does not seem to provide any proof of their effort in that respect. For that matter, the posted interview appears to have more data regarding microphone frequency response than it has on their speakers. The claimed frequency is 38-20 kHz without any specified tolerance. Speakers are always tradeoffs, but either a lot more money has to be invested to get this driver to behave or you are simply getting a speaker with a set of questionable compromises.

For more than $5000 for a pair of Sibelius SGs, would want a solid try before I buy opportunity!

 

[tuga]

It is quite possible that a speaker with very good measurement results sounds subjectively worse to you than a less well-designed speaker with better fine tuning.
The well designed speaker should be relatively easy to fix with a little EQ - the opposite case would be much more difficult or impossible to realize.
Therefore, it is always an advantage if the speaker designer has so much experience and knowledge to realize both (good subjective sound and good objective measurements), because then the speaker is most flexible to use.

That is fine in theory, but very few audiophiles use EQ. and many audiophiles who listen to vinyl refuse to pass their precious analogue signal through an A/D and D/A stage.

 

[Mr. Widget]

That is fine in theory, but very few audiophiles use EQ. and many audiophiles who listen to vinyl refuse to pass their precious analogue signal through an A/D and D/A stage.

Wasn't the birth of the "High End" when tone controls left the preamp.

 

[amirm]

That is fine in theory, but very few audiophiles use EQ. and many audiophiles who listen to vinyl refuse to pass their precious analogue signal through an A/D and D/A stage.

Their loss...