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Which speakers are the Classical Music Pros using?

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tuga

tuga

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I don't mind close micing. It definitely sounds different, with a lot more "zing" to the timbre of the instruments. Though it can still sound natural and realistic, the sound one hears on stage with the musicians.

I can understand why a musician might enjoy the sound presentation of close mic’ing, or even a music lover who doesn’t attend live music performance on a regular basis, but for a regular used to listen from the audience that “zing” and the extra detail sound somewhat forced or fake.
 

youngho

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The problems with close mic'ing are that it picks up mechanical sounds and mouth noise which are not audible from the audience and also that it changes the timbre of instruments and vocals by favouring particular ranges over of others due to the radiation pattern which changes depending on the notes being played:

The other weekend, I had the opportunity to hear Jennifer Koh play several of the Bach sonatas and partitas for solo violin in the Isabella Stewart Gardner Museum courtyard. I sat in a different place for each one, the last time sitting on steps less than estimated twenty feet away about 45 degrees between the scroll and F holes. In contrast, most solo violin performances that I’ve attended have been where I sat lower than the level of the violinist. I felt that the timbre was close to that of her recording, so I wondered if the recording microphones were placed higher than a seated listener position...

Anyway, the point I was trying to make was that it's very often not simply a matter of reproducing what the microphone(s) "heard," including ambiance cues. For some recordings, I wonder if the engineer might be trying to create an experience of the musician's perspective, like with many piano recordings having stereo spread (and in the case of violin, there's the element of bone conduction that changes the performer's perception of their own playing).
 

youngho

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The neurological components that get used when attending a live music performance are not the same neurological components that are used to listen to recorded music at home. Neurologically speaking, it's like tuning to a different communication channel, not just from FM1 to FM2, but from FM to being chased by elephants to floating in space. You can't 'build' the former out of the latter components. It's like trying to build a bicycle out of mechanical clock parts: the best you can do is something really poor, whereas you could have used those parts to make a really good mechanical clock. It's the wrong goal. It has nothing to do with purity: it is just the wrong idea altogether.
I would be curious to see what references you can provide to support these specific statements, outside of the visual and possibly tactile aspects of the live music experience being absent from non-video music recordings. I was only able to find two possibly related ones.

Music therapy live versus recorded
Inter-brain coherence predicts popularity of violin video (note that this was not a live performance, but the inter-brain coherence has been linked to other live activities besides attending a live music performance, both vis-a-vis the relationship with a performer and with other audience members, but note that controversy regarding mirror neurons does exist, anyway, can also take a look at this Scientific American article)

I contacted the second author of this review on neurobiology and music to see if there were additional references he could provide. Not related, but also interesting: reading music vs listening to it and predictive activity when listening to notes vs rests

As far as analogies, I would compare this more to the experiencing of listening to someone face-to-face in-person as opposed to on the phone. There should be significant overlap in terms of the parts of the brain used for the latter as in the former, while activity in other areas would be different. Otherwise, I don't know what other "neurological components" you're thinking about.

I wonder if @Kal Rubinson would be willing to discuss further.

Young-Ho
 
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MRC01

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I can understand why a musician might enjoy the sound presentation of close mic’ing, or even a music lover who doesn’t attend live music performance on a regular basis, but for a regular used to listen from the audience that “zing” and the extra detail sound somewhat forced or fake.
For close miced recordings that are excessively bright, I find a simple EQ softens the edge: -2 dB @ 1250 Hz Q=0.5, low pass shelf.
 

Kal Rubinson

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I wonder if @Kal Rubinson would be willing to discuss further.
Not at this time. I cannot do so without learning more about the issues.
 

GXAlan

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The saving grace was that we kept on publishing the results of our investigations for our competitors to read and learn from - thank you Sidney Harman (RIP).

1. Was that approach something you had to request, or did Sidney Harman bring up the idea of continuing to publish?

2. One of the things that Sidney Harman was a big advocate of was having research, design and manufacturing in a single location for the fastest transfer of ideas to product and to allow cross pollination between the groups.

Do you have any stories that you can share of how something went from a discovery in your lab to a product?

3. One particular question I had was when Revel went from rear firing tweeters in the first generation speakers to a more traditional setup in the current generation products. Are there certain rooms where the added energy is helpful?


If the research had continued, no doubt we would have eventually addressed the matter of just how important the shapes of the off-axis frequency responses are, as a factor separate from the smoothness (absence of resonances).

4. Are there any university groups still involved in this field of study? Or as home audio market has dwindled has academic interest also slowed down?

5. Given the ready availability of tools like the Klippel to analyze speakers without an expensive anechoic chamber, and the fact that a handful of billionaires are audiophiles, what sort of endowment would it take to actually set up an lab to continue some of your work in this space? Asr is Amir‘s retirement hobby but imagine a 501c3. (Is this a $10M or a $100M effort?)

6. Last, any comments on the JBL Paragon? Both for its sound in its era and today, if the constraint was furniture of similar proportions (i.e. a single speaker instead of two separate towers).

Thanks for all of your input in this forum.
 

krabapple

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But there’s of course another side to post-processing: the vast majority of records with classical music have the impossible task of giving the listener the impression she/he is in a concert venue - a task only possible by technical manipulation.
Hardly impossible...if you record and play back in multichannel.

The 'impossibility' stems from sticking to 2-channel, which has *never* been more than adequate.
 

Kvalsvoll

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Just a quick comment to make an important point - loudspeaker systems should be measured in the far field - i.e. at 2 m or more. The one meter "distraction" originated with the old sensitivity metric of "one watt in at one meter" - now 2.83v in at 1 m. When that sensitivity is measured, it correctly should be measured at 2 m or more and then calculated back to what it would be at 1 m. Only single transducers, small ones at that, can be reliably measured at 1 m.
Important, because difference 1m to 2m can be quite significant, such as a typical floorstander will have significant path length differences going from 1m to 2m. Mapping near-field scan measurements of such speakers to different observation distances will reveal that this is the case.

And - no, this is not an indication of a compromised design, the speaker can still produce a completely coherent, seamless integration at the listening distance it was designed for.
 

rdenney

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I am not sure that I fully understand your questions but I'll give it a go.

The study used three different speakers: one monopole with wide-ish directivity, one monopole with narrowing directivity and one dipole with narrow constant directivity.
...

...
I am not questioning the importance of smooth directivity in reverberant, untreated rooms. Directivity is on the one hand a matter of taste and on the other a way to control how your speakers interact with the room. From my understanding and experience, and even taking into account that it is ultimately a matter of taste, wide directivity is, like omni, not suitable for narrow rooms (unless you like it).

You probably agree that the most significant difference between mono and stereo is the latter's ability to produce phantom source localisation and multi-dimensional spatial presentation (soundstage). These stereo effects result from using two speakers (and idealy a 2-mic 2-channel recording) but there seems to be some conflict between obtaining image "sharpness" and increasing "spaciousness". D'Antonio and others seem to agree that early reflections are damaging to both image "sharpness" and the "reconstruction" of the original venue acoustics (when there was one) and that is my experience too. And even though ultimately it's a matter of preference, if (you find that) early reflections are damaging then wide directivity does not make sense unless the room is very wide.

In regard to your cellist analogy there is a very concrete difference in goals between a musical instrument and a sound reproduction device or system, the former creates sound and the later reproduces recorded sound. Unless the cello was close mic'ed or recorded outdoors the mic will have picked up ambience cues. If your room's acoustic footprint is too strong (a reflective room, or wide-directivity speakers which interact more with the listening environment) it will overlay itself to or mask the recorded ambiance and mess it up. Whilst the result of this interaction may sound pleasing with pop/rock studio mixes it is in my view and/or for my taste damaging with classical music.

The point of Toole's research is that people are able to adapt to room effects unconsciously while timbre errors not so much. I agree that strident early reflections can cause some confusion in the sound, but it seems to me that using speakers with narrow directivity is a second-best way to deal with that. And given that there is no way to address those reflections in the bass region, the result of the narrow field is that the speakers will only have the correct timbre in line with the tweeter beam, and will tilt bass-heavy (and boomy) outside the sweet spot. This is unacceptable to me--sometimes I play along with recordings and I'm not even in front of the speakers when I do so--I want to preserve reasonable timbre (though I'm not a perfectionist on that in that use case).

In a PA system, I might have a different objective--for example to support the clarity of the spoken word in a reverberant room, or to minimize the beaming of the PA speakers into the microphones. For that, I want a speaker with controlled directivity. But I'm not expecting timbral purity in that case. My church is an example. Musicians love it--the RTA60 is in the several seconds range. For the sorts of music played in our (traditional) church, that kind of reverberation is welcome (as long as we can minimize obvious echo, and despite the abundance of echo surfaces, we seem to have been lucky in that regard). But for speech, the bass reverberation blurs the consonants and intelligibility suffers at distances greater than about 15 feet. It depends on the voice, of course--our rector's voice lacks bass boominess and has a high penetration quality in the middle frequencies, and his voice can punch through the reverberation about as well as the sound system I designed (using the tiny JBL CBA-50 line-array speakers, by the way, which have good directivity control, particularly in the critical vertical pattern). But some people who speak don't have that voice training and the system greatly improves intelligibility. But that's not the objective for listening to music at home.

My own room actually minimizes first reflections at the listening position, one way or the other. On the right, the direct reflection is at the top of a cabinet with a lot of knick-knacks on it that disperse the sound it would seem, plus an open doorway that eliminates much of the wall reflection surface. On the left, the only reflective surface that visible as a first reflection is the short end of a grand piano, which is a pretty small target. And there's usually a music stand in front of it that scatters the reflection away from the LP. The ceiling slopes up as it leaves the wall behind the speakers, and there is no first reflection surface in front of the speakers unless the LP is six feet higher than it is. The floor is carpeted with a rug on top of that, plus a bit cushy ottoman in front of the LP chair. Coffee tables are to the side where they belong. The only first-reflection surfaces to worry about are behind the speakers and behind the listening position, but even the latter is only partial, being divided by the side of a staircase to an open loft area. So, lots of space but no many reflection points. Believe me, I have no problem with spatial imaging if it's there in the recording.

My point in bringing up the cellist is that the sound field it produces includes a range of cues that help the listener understand it. One is the collection of reflected sounds, their strength and how much they are delayed--this of course changes dramatically depending on where the listener is sitting. Another is the size of the sound source with respect to the distance to the listener. Yet another is the stereo image created by two microphones, if indeed two microphones are used, and this varies quite a lot based on how they are arranged. The first two can be greatly affected by the speaker's timbral accuracy--those cues will be upset by resonances in the speaker, whatever their source, it seems to me. The last one is mostly about what's in the recording. Toole's suggestion and his data seem to show that speakers that get the first two right will get the third right, and speakers that get the first two wrong won't be helped by the third. But part of timbral accuracy needed by the first two is that reflected sounds have a timbral relationship to the direct sound that is believable, and that seems to me the point of wide directivity. Toole also suggests that the stereo effect of left and right microphones separated into left and right channels can overpower our sense of those timbral effects, making it difficult to identify which speakers are actually good at delivering a believable collection of reflected sounds.

Classical instruments were designed for reverberant acoustic environments, and are evaluated by their owners in reverberant acoustic spaces.

Back to topic: If I wanted to record classical music for home playback, I'd record to gather necessary data, and then target the mix and mastering using speakers like those that are used for home playback, in rooms like those in homes. That's for the same reason that when I target the color and contrast on a digital photo for display on a particular device, I use settings that emulate that device (and do so after a careful calibration process), and if possible I validate on the device itself. If I lack control over the viewing device, I'm careful not to do anything that really depends on a particular device to look right, or that corrects an error only in my working device. I've invested in basic testing and calibration equipment for that purpose, but I don't see the same level of care in calibrating audio in the recording chain.

Rick "who does not want a recording to sound like it does on stage" Denney
 

rdenney

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That is a nice looking horn.

Edit: Ha! You weee talking about the horn, not the tuba. I agree!


Thank you. Truth to tell, it was getting rather grotty lately, and last week I ragged it out for the first time in about five years. Silver-plate looks wonderful when polished, but it doesn't stay that way. By the way, the instrument is a Hirsbrunner HBS-193, hand-made by one of the leading makers in the world and far better than I deserve. Only a couple of dozen of these have been made since they started making them easily a century ago. More expensive than Salon2's, less than Willson WATT Puppies (or whatever they are called).

Rick "whose insurance premium just about doubled when bringing this one home" Denney
 
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Floyd Toole

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1. Was that approach something you had to request, or did Sidney Harman bring up the idea of continuing to publish?

2. One of the things that Sidney Harman was a big advocate of was having research, design and manufacturing in a single location for the fastest transfer of ideas to product and to allow cross pollination between the groups.

Do you have any stories that you can share of how something went from a discovery in your lab to a product?

3. One particular question I had was when Revel went from rear firing tweeters in the first generation speakers to a more traditional setup in the current generation products. Are there certain rooms where the added energy is helpful?




4. Are there any university groups still involved in this field of study? Or as home audio market has dwindled has academic interest also slowed down?

5. Given the ready availability of tools like the Klippel to analyze speakers without an expensive anechoic chamber, and the fact that a handful of billionaires are audiophiles, what sort of endowment would it take to actually set up an lab to continue some of your work in this space? Asr is Amir‘s retirement hobby but imagine a 501c3. (Is this a $10M or a $100M effort?)

6. Last, any comments on the JBL Paragon? Both for its sound in its era and today, if the constraint was furniture of similar proportions (i.e. a single speaker instead of two separate towers).

Thanks for all of your input in this forum.
"Was that approach something you had to request, or did Sidney Harman bring up the idea of continuing to publish?"

As a research scientist I was a bit of an anomaly in the context of this large manufacturing company, many people thought I was an academic, detached from their world. In fact, at the National Research Council of Canada (not a university!) my research had led me into intimate interactions with several loudspeaker designers and manufacturers - for about 20 years by then - all very much real world. They were benefitting from the guidance of my research, renting the NRC anechoic chamber and custom measurement equipment to design their products, and using the double-blind listening test to verify their efforts. It was the beginning of the Canadian loudspeaker industry which I am proud to see is still prospering.

I was hired because of what I knew, and that came about as a result of applying the scientific method to investigations of the unknown. Doing it required engineering facilities that were lacking at Harman and subjective evaluations that were more than the sighted opinions of the designer and a few management-level people. "More bass, more treble" was not an uncommon parting statement from marketing types. It was insulting to some serious efforts by engineers, and it is easy to see why loudspeakers in the marketplace varied so enormously in sound quality.

Nobody could remember a blind, much less a double-blind listening test ever having been done at Harman. "We are professionals" was the reason they could not be biased. Sean and I managed to get several of them to participate in a test of their objectivity:
Toole, F. E. and Olive, S.E. (1994). “Hearing is believing vs. believing is hearing: blind vs. sighted listening tests and other interesting things”. 97th Convention, Audio Eng. Soc., Preprint 3894. It was a wake-up moment for all but one engineer, who persisted in avoiding having his standing as a "golden ear" tested. I was a corporate officer and had no line authority over engineers employed by the brands. I could only suggest, and to the brands what mattered most was sales.

In discussions in this forum it is clear that some participants just don't realize what a rudimentary state the loudspeaker design was in back in the 1970s and 80s. Measurements were primitive. One of the most prominent high-end loudspeaker companies of the day had only a 1/3-octave real-time analyzer to do room curves - an approximation to no useful data at all. Real decisions were made in informal listening sessions, all sighted - all possible subjective biases in place - and some while "under the influence" (smile). I felt I had created an oasis of calm and sanity, where if the objective is to design a good sounding, neutral timbre, loudspeaker it was possible to do so with confidence - as well as to deviate knowingly from that if it is felt that the market desired it.

Soon there were discussions about continuing the research at Harman so that we could refine what was known and expand new knowledge into areas that were beneficial to our products. I asked for, and got, permission to set up a Corporate Research Group to create new knowledge - not new products. A key component to research is the public sharing - a give and take - of knowledge; presenting and publishing scientific papers. Remarkably, it was not a big issue, and Sidney Harman agreed that we could publish. I sensed he felt that it would add to the image of the corporation, separating us from our competitors. He was right, but not in the domain of consumer audio which was improving, but remained significantly confused by "incomplete information" about products, with a skepticism that science and measurements had anything to do with music, soundstage and imaging, air, tight bass and "resolution". It was totally different in the area of automotive audio. This was a rapidly growing sector of our business (about 10% of $0.5M when I joined, and about 75% of about $7B including infomatics when I retired). Automobile engineers respect science, knowledge and facts - they listened intently at my presentations to a "who's who" of the automobile industry over the years.

I immediately hired Sean Olive, my colleague at the NRC in Canada, and a bit later Todd Welti, an educated and experienced acoustician. Sidney authorized millions of dollars of investment in engineering facilities, anechoic chambers (2 pi for transducers and 4 pi for systems) all set up for high resolution measurements and calibrated to low frequencies. Up to date computers and modeling software, a scanning laser interferometer, transducer parameter and distortion measuring apparatus all added insight and capability. New listening rooms were created for double-blind testing, a unique positional-substitution one being the most useful. The listening room cannot be eliminated but it can be rendered a constant factor in comparison tests.

Over the years several smart engineering interns went through the research group and ended up in prominent engineering jobs in Harman and with our competitors. It is a "life changing" experience to witness how reliable and strong the connection is between measurements and double-blind listening tests. Allan Devantier, another Canadian from the NRC period, had a successful career at Harman, being responsible for some of the best designs by Infinity, and co-creator (with Charles Sprinkle, another believer in science, now with Kali) of the JBL Pro M2, a benchmark design. After a brief stay in my research group where he collaborated with Todd Welti on an active multi-subwoofer solution called Sound Field Management, Allan now heads up Samsung's audio engineering activity, and has an updated version of all of the Harman measurement and evaluation capabilities. Samsung later purchased Harman, mainly, I think, because of the access it provides to the automotive industry. Harman operates substantially independently, though - as least as I understand things. I retired in 2007, and remained on a consulting retainer until 2019.

"3. One particular question I had was when Revel went from rear firing tweeters in the first generation speakers to a more traditional setup in the current generation products. Are there certain rooms where the added energy is helpful?"

It was conceived, I believe, as a product differentiator with a rational reason to exist. However, in real rooms its benefits were not clear. One reason is that air attenuation sets in above about 1 kHz and is substantial with increasing distances (Section 10.6 in the 3rd edition). Just do some ray tracing in normal rooms and it is clear that any sound that has reflected once or twice has not only undergone some loss at the reflecting boundary but has lost energy to air attenuation. Result the spectrum of the reflected sound field rolls off at high frequencies. This rear-mounted tweeter had little chance of changing that - but in principal it is logical if measured power response is a consideration.

"4. Are there any university groups still involved in this field of study? Or as home audio market has dwindled has academic interest also slowed down?"
In general universities lack the necessary measurement facilities, listening facilities, and budgets to prepare for serious efforts in this area. As can be seen in discussions in this and other audio forums, many people have moved on from pure stereo, enjoying the benefits of processed (upmixed) or real multichannel movies, music videos and music - always with the opportunity to revert to stereo. Those who by choice or circumstances remain in the stereo domain, still seek something that the two-channel format cannot deliver, and endless debates ensue.

Audio has evolved, and decent sounding baby bluetooth loudspeakers responding to voice commands can deliver tolerable tunes in every room in a house. Headphones abound, and even I enjoy listening to music or podcasts while walking or flying. Sean Olive - now Dr. Sean Olive - continues his research but the emphasis is now on headphones. His contributions are profound, again the result of patient, time and effort consuming blind tests and valid measurements, all published for the world to absorb.

Yes there are a few university efforts ,mostly as I observe, in England, Europe and Canada, and largely engaged in multichannel applications. When I last visited McGill University in Montreal, one of the contributors, all of the post graduate projects that were demonstrated to me involved multiple - more than 5 or 7 - channels. Stereo was very much a "been there done that" issue. But as I see it, the big questions about loudspeakers have substantially been answered, and money to support the motivations to explore second-level and lower issues, especially those applicable to purist stereo, is not abundant.

"5. Given the ready availability of tools like the Klippel to analyze speakers without an expensive anechoic chamber, and the fact that a handful of billionaires are audiophiles, what sort of endowment would it take to actually set up an lab to continue some of your work in this space? Asr is Amir‘s retirement hobby but imagine a 501c3. (Is this a $10M or a $100M effort?)"

A nice fantasy. A few years before I left the NRC I arranged a non-profit collaboration between a consortium of Canadian audio manufacturers and the NRC. It was necessitated by budget cuts at the NRC, a federal government organization, and science was losing favor among politicians (sound familiar?). It was the first collaboration between industry and government research in Canada at the time. Klippel (who was employed for a period in my research group BTW) measurement systems are simply minor miracles from my perspective - real hard science at work. Nevertheless, anechoic chambers still have advantages: a quiet background against which to evaluate non-linear distortions being one, but also it can be a permanent setup into which very different loudspeakers can be introduced and measured with minimal fuss But to answer your question, it depends on the cost of the real estate, its location, the ability to find competent researchers and their cost, the measurement equipment, the subjective evaluation venues and apparatus. Setup: less than $10M - pocket change for the 1%, but would it provide the necessary gratification?

"6. Last, any comments on the JBL Paragon? Both for its sound in its era and today, if the constraint was furniture of similar proportions (i.e. a single speaker instead of two separate towers)."

The JBL Paragon was a simply beautiful piece of furniture - impressive if one is into art-deco/Scandinavian style decor as I am. I have a story. When I was a PhD student at Imperial College in London, I tried to continue my audio hobby interest, but had no budget and no place to set up a system. I followed developments and went to an audio show at the Russell Hotel - tiny rooms typical of British hotels of the era. I had no pretensions about my ability to judge sounds, I could only say what I liked, or not. I went in with some strong expectations, such as: Quad ESL should be superb - "massless diaphragm" eh?, Tannoy, with its concentric design should reflect good engineering - point source, eh?, and so on. Reality set in quickly, and I discovered that simplistic views and marketing claims are a different thing. The Quad indeed sounded good, the ticks and pops of the LPs were reproduced with finesse, and the music sounded pleasing, but it seemed to have problems playing loud when people asked for the volume to be turned up beyond "polite". The Tannoy sounded horrible, shrill, penetrating, ugly. I was crestfallen. So I embarked on a wide survey of what was on display. One room had a JBL Paragon. It went almost from wall to wall in the tiny room. and was elevated to near ear level because of the listening distance. It could play indecently loud, crystal clear, impressive indeed. It seemed to have a distinctive sonic "personality" which was not totally endearing, but there was more to it than that. I returned a few times to try to pin down what that demo had that others lacked. When I poked around I opened a closet door and lo and behold there was a monster half-inch two track 15 inch-per-second Ampex tape recorder. That was it! Master-quality program material! Everyone else was using LPs with all of the inherent distortions, noise, frequency response inconsistencies and dynamic limitations.

So what did I find attractive? The KEF Concord, a new product from a new company seemed to have something going for it. I got to know Raymond Cooke, the owner/desingner, and wangled a price reduction "for research" - tongue in cheek. As explained in Section 18.1 in the 3rd edition with measurements, I wasn't completely wrong, and the speakers never made it into my home as purchased. Raymond and I remained friends, visiting back and forth for several years. Through him I subsequently got to know Laurie Fincham then head of engineering at KEF, who remains a friend here in California, having been hired into Harman via Infinity, then moved to THX. I also got to spend quality time with Peter Walker of Quad, extensively touring the facility, sitting in "his" chair where he "voiced" his loudspeakers, and drinking good Scotch with him in his large living room with a pair of ESL-63s providing the tunes. He was a fine person, nice, unpretentious, and very capable.

In its day the Paragon might have been sonically competitive, but it was far from neutral. One sat in the Harman corporate office while I was there - silent, elegant, a lovely piece of audio sculpture.
 
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MRC01

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I can understand why a musician might enjoy the sound presentation of close mic’ing, or even a music lover who doesn’t attend live music performance on a regular basis, but for a regular used to listen from the audience that “zing” and the extra detail sound somewhat forced or fake.
I don't actually enjoy or prefer that close-miced sound. It is too bright and zingy for my taste. I prefer the sound from the 1st row seats. In fact, when I try out different instruments I record them from 10 feet away because it sounds so different. An instrument that sounds nice to me while playing, is often too dead sounding from 10 feet away and doesn't project. Conversely, one that sounds the way I like at 10 feet away sounds too bright, zingy, edgy to me while playing. That's one reason musicians have multiple instruments.

My point was that the close-miced sound is at least natural or realistic, in the sense that is how music actually does sound from a certain perspective. So I find it an acceptable approach to recording even if it's not my favorite. While it sounds artificially bright and edgy to people who are more familiar with the audience perspective, it's nowhere near as artificial and edgy as over-processed modern recordings.
 

Sancus

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A recording engineer with a lot of acoustical music experience, Mark Waldrep, has unequivocally stated that close-mic multi-mic recording enables much more enjoyable recordings when played back. The absence of close mics simply cripples the potential final result.

For stereo-only? The previously mentioned award-winning 2L classical/jazz recordings aren't close-mic'd and they're some of the best multi-channel ones I've heard. There are also close-mic'd multi-channel albums I like a lot but they're definitely not on the same level of immersiveness.
 

Duke

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"3. One particular question I had was when Revel went from rear firing tweeters in the first generation speakers to a more traditional setup in the current generation products. Are there certain rooms where the added energy is helpful?"

It was conceived, I believe, as a product differentiator with a rational reason to exist. However, in real rooms its benefits were not clear. One reason is that air attenuation sets in above about 1 kHz and is substantial with increasing distances (Section 10.6 in the 3rd edition). Just do some ray tracing in normal rooms and it is clear that any sound that has reflected once or twice has not only undergone some loss at the reflecting boundary but has lost energy to air attenuation. Result the spectrum of the reflected sound field rolls off at high frequencies. This rear-mounted tweeter had little chance of changing that - but in principal it is logical if measured power response is a consideration. [emphasis Duke's]

Thank you for posting so much information here, and in particular about the rear-firing tweeters. Very interesting... if I understand correctly, the intention was to improve the spectrum of the reflected sound field, but presumably the rear-firing tweeters failed to make a worthwhile improvement because the additional short-wavelength energy was being attenuated too much by the air.

Figure 7.20 (third edition) shows the similarity between the direct and reflected spectra of the highly successful Mirage M1s, so arguably Revel's original intentions were not misguided.

Do you recall if there were any perceptual downsides to the rear-firing tweeters?

Pardon my ignorance about upmixing - is the high frequency energy in the signal sent to the surround speakers rolled off a bit to simulate the effects of air attenuation over a much longer reflection path?
 

Floyd Toole

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Thank you for posting so much information here, and in particular about the rear-firing tweeters. Very interesting... if I understand correctly, the intention was to improve the spectrum of the reflected sound field, but presumably the rear-firing tweeters failed to make a worthwhile improvement because the additional short-wavelength energy was being attenuated too much by the air.

Figure 7.20 (third edition) shows the similarity between the direct and reflected spectra of the highly successful Mirage M1s, so arguably Revel's original intentions were not misguided.

Do you recall if there were any perceptual downsides to the rear-firing tweeters?

Pardon my ignorance about upmixing - is the high frequency energy in the signal sent to the surround speakers rolled off a bit to simulate the effects of air attenuation over a much longer reflection path?
"Do you recall if there were any perceptual downsides to the rear-firing tweeters?" No.

" is the high frequency energy in the signal sent to the surround speakers rolled off a bit to simulate the effects of air attenuation over a much longer reflection path?"

It makes sense to do so, as it would be high frequency information, especially transients, that is most likely to create unwelcome, unrealistic, distractions. Some of it will happen naturally in the separation of correlated and uncorrelated information. Presumably much of the uncorrelated stuff has propagated over distances. Beyond that I don't know.

Any amount of front soundstage sound that directly makes its way into the upmixed surround channels cannot be good, even with a modest delay. The following illustrations are from the 1st and 2nd editions: Figures 7.1 and 5.2. It is based on the best information I could find at the time. It shows that envelopment - what we are most interested in for upmixing, mainly involves middle frequencies. Add to this that to be perceptually effective the delays need to be substantially greater than can be generated naturally in small rooms. My memory of the original (RIP) Lexicon Logic 7 upmixer is that it did an excellent job of separating the soundstage from the surround sound. My current Auro3D isn't as good, but I find it better than my current alternatives. I keep its contribution at a vey low level. Most people would not notice that it is on - except when I turn it off the performance, whatever it is, shrinks. Still, nothing beats real multichannel.


Figure 7.1 logo rev.jpg

Figure 5.2 reflection effects rev.jpg
 

Sancus

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My current Auto 3D isn't as good, but I find it better than my current alternatives.

If you haven't already seen it, you might be interested in the patent for Auromatic. Though, my understanding is that it has an incomplete description of the modern algorithm which also includes some additional psychoacoustic processing that is not mentioned in the patent.

I'm no expert but it sounds like Auro adds simulated reverberation calculated from the input signal as opposed to extracting ambience which is the approach that several other upmixers take(I'm fairly sure Dolby Surround and DTS Neural X attempt to do this).

Considering these are all proprietary, and could have many unlabeled versions out in the wild, it's definitely very difficult to figure out how they work.

Pardon my ignorance about upmixing - is the high frequency energy in the signal sent to the surround speakers rolled off a bit to simulate the effects of air attenuation over a much longer reflection path?

People sometimes complain that Auro3D/Auromatic boosts bass(which is true; it does to some extent depending on your strength setting) but I've often wondered if this is an intentional psychoacoustic compensation for the total effect of adding reverberation in the surrounds and heights.
 

richard12511

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What is the point of determining how good a speaker’s spatial performance is in mono if it will never be used as such?

And although I agree with the possible interpretation that stereo dulls the ability to discriminate spatial differences in my view such differences are only valid for single speaker listening and ignore the fact that a single speaker will be positioned very differently in the room from when used in a stereo pair. And because it is located further from the side walls in mono and close to them in stereo the spatial quality in mono cannot even be transferred to stereo.
I think both interpretations are valid interpretations of the provided data. From mono to stereo, the Rega went from 1st to 2nd, KEF from 2nd to 1st, and Quad from distant 3rd to very close 3rd. We would need more data(presumably Harman has it) to say which interpretation is more valid than the other. While I personally tend to lean more towards your interpretation(given the data we have), I have to assume that Dr. Toole's interpretation is based on far more data than what is shown to us. If I had to bet on one being correct, I'd have to bet against my own intuition here.

wide directivity speaker rates higher in terms of spatial quality in mono because when positioned equidistant to the side walls it will interact more with them than narrow or narrowing directivity ones.

This is definitely true for me. Rating purely the "Spacial" component, I rate wider dispersion higher in mono, and medium or narrow dispersion higher in stereo.

For mono listening, I prefer the spatial presentation of my Revels far more than I do my JTRs(narrow dispersion) or Genelecs(medium dispersion). The Revel throws a wider soundstage and disappears much better, which are the 2 components of how I rate "spatial" quality from 1-10.

In stereo, I actually rate the Revel the worst of the 3. The Revel still disappears a bit better, and it still throws a wider soundstage, but, it now does worse on the (new) third component, which is the tightness of the phantom center image. This may just be a personal preference, but I love tighter phantom imaging more than I love wider soundstage, excluding some types of symphonic music. For certain types of symphonic music, I actually enjoy a more diffuse phantom image, as it sounds closer to what I hear at live symphonic events.

A year or two ago I blinded the Genelec 8030c against the Revel M105, but only in stereo. I really wish I had done a subsequent mono test to see if the results changed. The Genelec won the stereo test, but I'm pretty confident the Revel would win a mono test. The reason I think this is twofold:

1. Tonality is almost identical, so it's gonna come down to the "Spatial" rating
2. The Genelec slightly won(imo this is why it won) because of the spatial component, which was due to the tighter phantom image it throws. I'm somewhat guessing this is why it won based on why I prefer it, and comments from the listeners. A common comment in favor of the Genelec was something like "this one sounds more like the singer is there in front of you". In mono, though, I actually rate the Revel higher for its spatial representation. There is no phantom image anymore, and the narrower dispersion makes it clearer that the sound is coming from a speaker right in front of you, which means the Genelec doesn't "disappear" as well as the Revel.

I definitely plan to redo this experiment and more, which is why I purchased the 3 way ABX Comparator by Van Alstine(though I still haven't had a chance to use it :().

One thing that may be the cause of some difference is: "What question are you trying to answer with this blind test?". Are you trying to find which speaker sounds best with "average" placement/toe-in? Or, are you trying to find which speaker sounds best with "optimal" placement/toe-in? I think the Harman research was aimed more at answering the former, whereas my tests were aimed more at answering the latter.

For answering the first question, the way Harman does it(speakers in same spot with same toe-in) makes the most sense, as user room placement and toe in will likely be all over the place. Doing it like this does definitely bias the results towards wider dispersion, and Dr. Toole has even mentioned this too. But, Dr. Toole also brings up the great point that this bias is not really a bad thing, as placement insensitivity is an inherent advantage of wide dispersion. My Revels sound great without much setup at allb at almost any position. Sure, you can optimize it a bit(maybe 10%?) by messing with toe-in, but they pretty much always sound great. My JTRs on the other hand are much more finicky. They go from sounding bad to sounding amazing just by adjusting the toe-in a bit.

For answering the second question, you would need to first find the optimal position and toe-in for each speaker under test, and then design a machine that can quickly place each speaker in that optimal position and orientation. Such a machine would likely be much more expensive and complicated, and maybe isn't answering the question that is most important to a manufacturer. The way we handled this was by spending a few days prior to the event finding the optimal placement/toe-in for each speaker, and then marking those positions with color coded tape for each speaker. On test day, when the listener called for the switch, we had two people to move the current speakers out of the way, and two people to move the new speakers into the color coded position/angle. It seemed to work really well, but requires a good number of people, and also our switch times weren't 3 seconds or less like the Harman switcher is(I'm hoping the ABX comparator can assist with this).

Anyways, glad to see Dr. Toole participating here, and this is something I'm super curious to see more research about. A loudspeaker like the Beolab90 would perhaps be an excellent test subject. Maybe the "wide" or "omni" mode is preferred in mono? Maybe the "narrow" mode is preferred in stereo? To truly answer this mono vs stereo debate for myself, I need the ability to hold the FR component as a constant, and let dispersion width be the only variable.
 

youngho

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Not at this time. I cannot do so without learning more about the issues.
Thanks. Getting to see my first live in-person music performance since before COVID (I'm not counting my kids' music practice) felt really intense. It was interesting to compare my memory of Jennifer Koh's recording with her live performance (sometimes with my eyes closed), then later to do the reverse. The cognitive activites of simply enjoying the performance versus trying to critically listen to the timbre/acoustic felt very different. This felt relevant to Toole's discussion about audio professionals and their preferences. I also found a similarly interesting discussion here.
 

youngho

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Thank you for posting so much information here, and in particular about the rear-firing tweeters. Very interesting... if I understand correctly, the intention was to improve the spectrum of the reflected sound field, but presumably the rear-firing tweeters failed to make a worthwhile improvement because the additional short-wavelength energy was being attenuated too much by the air.
Kevin Voecks comments here, combined the off-axis measurements shown here (particularly above ~7 kHz, note crossover frequency for rear tweeter was 8 kHz), lead me to conclude that your overall interpretation for the original intention was correct ("uniform power response"), but then read here to see his explanation for the elimination, which differs from your subsequent speculation.
 
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