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Geddes on Directivity


Zilch

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It's not a technical paper, rather, marketing pap for his product(s), and I'm at considerable risk over there for saying as much. Still, it lays out his basic thinking about the subject.

Consider contributing to that thread, maybe, Howard.

And link us to the Davis papers here, please.... ;)

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Interesting that he does not acknowledge the work Mark Davis did when he was at dbx that dealt with the time/intensity tradeoff issue. A good technical paper should always have bibliographic references, and Davis published papers on that topic that pretty much set the standard.

Howard Ferstler

Not exactly time intensity trade off, but I'd spent a few days last week working out a spreadsheet for aiming a horn over an cinema audience. The intent was to have the horn's directivity offset the direct field drop from the first row to the last. the distance ratio was such that the back row was 2 1/2 times the front row distance so there was roughly an 8dB level difference that needed to be compensated for. We use a large theater system from JBL with a 90 x 40 horn that has decent response as much as 30 degrees down from on axis. Aiming the horn to the back puts the front row at that 30 degree angle (assuming the speaker height is right) and makes the audience levels much more even. The problem is even greater if you consider the left and right speaker and the level difference between one front corner of the audience and the opposite front corner. Here the distance ratios were more like 4 to 1 for a 12dB direct field difference. A pretty extreme toe-in would only partly compensate.

I do remember the Mark Davis paper and the inward facing polar curve he was able to achieve.

Good stuff.

David

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Interesting that he does not acknowledge the work Mark Davis did when he was at dbx that dealt with the time/intensity tradeoff issue. A good technical paper should always have bibliographic references, and Davis published papers on that topic that pretty much set the standard.

Howard Ferstler

Leakey published extensively on time-intensity trading and stereo image stabilization in 1959. Ben Bauer at CBS Labs popularized the subject with his oft-referenced 1960 AES paper, which also migrated into several hifi magazines.

-k

BTW- From some old NHT lit:

"Focused Image Geometry determines the 21-degree angle which defines the 1.5's unique cabinet, as well as the sound radiation pattern of the system. The irregular enclosure shape greatly increases the ratio of direct to reverberant sound, reducing side-wall reflections and concentrating sound energy in the listening area. The exact angles at which the sound from the speakers reaches the ears of centrally located listeners is calculated to create what is known in acoustics as minimum “inter-aural cross-correlation." This technique allows the Model 1.5 to properly recreate the natural acoustic ambiance and perspective contained in good recordings. In addition, the radiating axes of the left and right speakers are crossed, providing “time-intensity trading,” so that the stereo image remains focused and stabilized for a wider range of listening positions."

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Giskard's comment on LHF suggests that Geddes has tried to build an improved 4430.

We are on common ground here, but for his laying claim to owning the fundamental concepts originally developed by others.... :D

I suppose it is a good thing that others are trying to sell systems with integral CD waveguides. I am more suprised that a lot of pro product designers don't seem to know they exist and use much inferior horns. Also the mythology built up around inferior horns such as the Klipsch Tractrix style.

When we developed the 4430/35 there was some internal debate about "flat power response" and its benefits. I wrote the AES paper so I inserted my opinion that it was secondary but would give a benefit for he usual (misguided) EQ in the reverberant field: peaks and dips in the power response are EQed when you are beyond the critical distance, and put inverse dips and peaks in the more important direct field. I see that JBL marketing literature now makes a big deal about flat power response. I don't think flat sound power is, or ever was, the goal. I think the real issue is that, statistically few of us are on axis. Having well behaved response over a range of possible listening angles (say +-30 degrees) is a real benefit.

If better off axis response lets you do time intensity trading (or seating area level distance trading) then that is useful tool. I haven't found high toe-in to be a total fix for sitting off center, though.

David

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If the goal is to engineer sound systems that reproduce recordings that sound like live musical performaces, then IMO these theories have more holes in them than a wheel of Swiss cheese. I have not heard Geddes speakers but his theories ignore many facts about the way musical instruments produce sound and the resulting acoustic interactions of their sound fields in real spaces. I don't think it would take golden ears to know the sound of Geddes speakers (or anyone elses) from live music, just normal hearing and it would be sufficiently different to be obvious immediately. I also don't believe modern sound systems could duplicate the results of the LVR demos using AR speakers in the 1960s which is probably why nobody seems to ever try it even though the availability of high quality recording equipment is widespread and has plummeted in price to where anyone can afford it. Even those demos were not perfect and were highly contrived but they did come remarkably and surprisingly close especially considering how poorly those systems often reporduced commercial recordings when judged by the same criteria.

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It's not a technical paper, rather, marketing pap for his product(s)

I've written marketing pap for products, and the usual MO is to cite as much prior art as possible to help convince prospective customers that your product uses widely recognized and accepted "best practices" (for example, all that email spam you get that claims that some bit of snake oil is endorsed by Oprah or based on research by an unnamed university in Sweden).

Papers in which the writer appears to be claiming credit for the work of others is more likely marketing pap for the writer...

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When we developed the 4430/35 there was some internal debate about "flat power response" and its benefits.

You made a good call, obviously. :)

Even those demos were not perfect and were highly contrived but they did come remarkably and surprisingly close especially considering how poorly those systems often reproduced commercial recordings when judged by the same criteria.

The two are easily reconciled.

I found it particularly interesting that Geddes considers 90° to be "very narrow" directivity. I believe Howard and I agreed (a feat not casually achieved ;) ) that it was more like "medium".

Earl must think there is some marketing mileage to be garnered from that characterization, as I don't believe it is technically defensible. :D

Papers in which the writer appears to be claiming credit for the work of others is more likely marketing pap for the writer...

That is certainly a major element in this instance.

It's insulting, frankly; I made my point there, and admin apparently agreed.

[i also received a procedural warning.... B) ]

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You made a good call, obviously. :)

The two are easily reconciled.

I found it particularly interesting that Geddes considers 90° to be "very narrow" directivity. I believe Howard and I agreed (a feat not casually achieved ;) ) that it was more like "medium".

Earl must think there is some marketing mileage to be garnered from that characterization, as I don't believe it is technically defensible. :D

That is certainly a major element in this instance.

It's insulting, frankly; I made my point there, and admin apparently agreed.

[i also received a procedural warning.... B) ]

Since the type of music you told you you like "rock music" is invariably heard "live" from vast arrrays of loudspeakers manufactured by companies like Community Sound, JBL, Altec Lansing, etc. often at ear splitting levels, why does any of this matter. I'd think it would be all purely academic to you. Why not just buy the same speakers sports arenas and the like use for live concerts? THX certified systems should suit you to a tee.

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Since the type of music you told you you like "rock music" is invariably heard "live" from vast arrrays of loudspeakers manufactured by companies like Community Sound, JBL, Altec Lansing, etc. often at ear splitting levels, why does any of this matter. I'd think it would be all purely academic to you. Why not just buy the same speakers sports arenas and the like use for live concerts? THX certified systems should suit you to a tee.

You have me confused with that Kantor guy, apparently. ;)

Some technology originally developed for Sound Reinforcement has been found also suitably applicable to home use, constant directivity being a major one. Villchur and the other East Coast pioneers were themselves struggling to make it happen.

The bell which has not yet rung for you is that my mains, and the basis for much of my (and Geddes's) work for many years, were designed at JBL by our very own Speaker Dave 30 years ago.

[YOU know, the ones you said quite obviously suck, without ever having heard them, right here in this forum.... :D ]

When we developed the 4430/35 there was some internal debate about "flat power response" and its benefits. I wrote the AES paper so I inserted my opinion that it was secondary but would give a benefit for he usual (misguided) EQ in the reverberant field: peaks and dips in the power response are EQed when you are beyond the critical distance, and put inverse dips and peaks in the more important direct field. I see that JBL marketing literature now makes a big deal about flat power response. I don't think flat sound power is, or ever was, the goal. I think the real issue is that, statistically few of us are on axis. Having well behaved response over a range of possible listening angles (say +-30 degrees) is a real benefit.

I think we have to be careful and distinguish between flat vs. uniform power response. Flat power response implies flat DI, no? If so, that's generally acknowledged as being overly bright (see Toole), and we can be duly thankful that Villchur et al. never achieved their objective.... B)

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You have me confused with that Kantor guy, apparently. ;)

Some technology originally developed for Sound Reinforcement has been found also suitably applicable to home use, constant directivity being a major one. Villchur and the other East Coast pioneers were themselves struggling to make it happen.

The bell which has not yet rung for you is that my mains, and the basis for much of my (and Geddes's) work for many years, were designed at JBL by our very own Speaker Dave 30 years ago.

[YOU know, the ones you said quite obviously suck, without ever having heard them, right here in this forum.... :D ]

I think we have to be careful and distinguish between flat vs. uniform power response. Flat power response implies flat DI, no? If so, that's generally acknowledged as being overly bright (see Toole), and we can be duly thankful that Villchur et al. never achieved their objective.... B)

"You have me confused with that Kantor guy, apparently."

I don't think so. The two of you were quite in agreement about it. Why would anyone want to get an AR LST to sound like a JBL S-7, S-8, S-15 or an Altec VOTT? Those speakers have tweeters that will make your eardrums bleed before they burn out. Would have saved him a lot of trips back and forth to the AR parts counter if he'd bought them instead.

"Some technology originally developed for Sound Reinforcement has been found also suitably applicable to home use, constant directivity being a major one. Villchur and the other East Coast pioneers were themselves struggling to make it happen."

Not AR. Their philosophy was to achieve the widest high frequency dispersion possible. Villchur's and Alison's goals in this regard were diametrically opposite of controlled directivity.

"The bell which has not yet rung for you is that my mains, and the basis for much of my (and Geddes's) work for many years, were designed at JBL by our very own Speaker Dave 30 years ago. "

Who cares? Those who think those are better speakers wouldn't be here, they'd be posting on the Lansing Heritage site. Those speakers were designed for cinema sound and scaled down for home use. As high accuracy reproducers they had no credible claim to any of their products. At least not for acoustic instruments. As for reproducing the sound of "music" performed through other speakers including their own, well that would hardly be surprising since they were cut from the same bolt of cloth.

"[YOU know, the ones you said quite obviously suck, without ever having heard them, right here in this forum.... "

I've said that in achieving the goal of reproducing the sound of acoustical musical instruments, the one time ostensible goal and claim of high fidelity sound reproducing equipment manufacturers, virtually all speakers and sound systems on the market suck. Their design is utterly incompatible with achieving sound fields of similar characteristics to that made by musical instruments when judged on an objective and informed basis. Their failure is therefore not at all surprising. In fact their failure is so complete and consistant, they don't even bother making that claim anymore. Whatever they are supposed to be able to do, that isn't it. In fact it is they who have never heard real music and so many of them claim their sound is better than real music. Of course beauty is in the ear of the beholder but as a tehnical effort to reproduce a sensory stimulus created one way by other means, they have failed just as no video travelogue seen on a black and white television picture tube will convince anyone they are actually looking at the grand canyon no matter how contrasty and sharp it is.

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Not AR. Their philosophy was to achieve the widest high frequency dispersion possible. Villchur's and Alison's goals in this regard were diametrically opposite of controlled directivity.

I said constant directivity, and I am right. Get over it. ;)

Those speakers were designed for cinema sound and scaled down for home use.

Must you remain forever clueless? They are Studio Monitors, and were never sold for consumer use. :D

http://www.harman.com/EN-US/OurCompany/Tec...ations/4573.pdf

[Heads UP, Howard; somebody you know is there.]

I've said that in achieving the goal of reproducing the sound of acoustical musical instruments, the one time ostensible goal and claim of high fidelity sound reproducing equipment manufacturers, virtually all speakers and sound systems on the market suck.

Yes, we all know you have the secret to truly realistic sound reproduction, and also that you are keeping it to yourself.... B)

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I said constant directivity, and I am right. Get over it. B)

Must you remain forever clueless? They are Studio Monitors, and were never sold for consumer use. :D

http://www.harman.com/EN-US/OurCompany/Tec...ations/4573.pdf

[Heads UP, Howard; somebody you know is there.]

Yes, we all know you have the secret to truly realistic sound reproduction, and also that you are keeping it to yourself.... :)

And by what engineering device did Villchur incorporate in his designs to control directivity to suggest this was his goal? No horn loading, actually nothing. Then how do you draw this conclusion? Between AR LST and Alison's designs, their design tried to extend lateral HF dispersion to 180 degrees or as close as they could to get to it. Here's the ultimate controlled dispersion speaker for you Zilch. A tube with a speaker at one end and your ear at the other. When you are in line with it you get everything, when you're not, you get nothing.

Around 1967 or 1968 I met a salesman from Altec at a trade show who was very excited because he had just sold 56 pairs of VOTTs to Columbia Records to use for studio monitors. What's the difference, monitor speakers, theater speakers, they pretty much are useless for serious home high fidelity use. Monitors are often just scaled down theater speakers anyway. At least in the old days, they used to equalize them with calibrated microphones once a week. Today, audiophiles who have become sound engineers don't like their monitors being equalized. That might be one reason spectral balance of CDs is all over the lot and they sound so awful unless you compensate for each one. I'll bet some audio engineers are using their favorite home hi fi speakers as studio monitors.l

As for my own personal sound system, you have no way to find out about it anymore than Howard has to find out about yours. ;)

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Why would anyone want to get an AR LST to sound like a JBL S-7, S-8, S-15 or an Altec VOTT? Those speakers have tweeters that will make your eardrums bleed before they burn out. Would have saved him a lot of trips back and forth to the AR parts counter if he'd bought them instead.

Who cares? Those who think those are better speakers wouldn't be here, they'd be posting on the Lansing Heritage site. Those speakers were designed for cinema sound and scaled down for home use. As high accuracy reproducers they had no credible claim to any of their products. At least not for acoustic instruments. As for reproducing the sound of "music" performed through other speakers including their own, well that would hardly be surprising since they were cut from the same bolt of cloth.

I've said that in achieving the goal of reproducing the sound of acoustical musical instruments, the one time ostensible goal and claim of high fidelity sound reproducing equipment manufacturers, virtually all speakers and sound systems on the market suck. Their design is utterly incompatible with achieving sound fields of similar characteristics to that made by musical instruments when judged on an objective and informed basis. Their failure is therefore not at all surprising. In fact their failure is so complete and consistant, they don't even bother making that claim anymore. Whatever they are supposed to be able to do, that isn't it. In fact it is they who have never heard real music and so many of them claim their sound is better than real music.

Well, I guess I have to come to the defense of poor old JBL. Sure, an S7, S8 or Voice of the Theater are not the ultimate in transparency or freedom from coloration compared to what we have today, but then AR products from the same decade have been surpassed in those regards as well.

I was only with the company for a couple of years but I greatly admired their engineering (and still do). I don't know of any other company with as advanced transducers in terms of power handling and freedom from distortion. The 100 x 100 horn of the 4430 that Zilch refers to has the most amazingly well behaved and consistant horizontal and vertical polar curves of any transducer I have ever measured in 30+ years. The system was meant to be an advance on the S7 or 4300 series studio monitors that preceeded it, and it was.

These were studio monitors rather than theater speakers. Nothing wrong with theater speakers though. I'd recently spent an afternoon in the public library copying papers by Altec's John Hilliard from 1940's SMPTE journals. The level of engineering was very impressive. If you need the ouput to fill a cinema or auditorium then a small but accurate bookshelf speaker won't cut it.

"But what of accuracy reproducing acoustical instruments?" I think that was pretty good too, with the right models. I"m not a fan of the 4311/L100 generation but the L96, L112 and L150 and L250 got pretty good reviews as I recall. Usually with the odd preamble that "JBL, known for its rock and roll speaker has actually been able to design a product that suits all types of music." A bit like every Porsche 911 review has to end with "Porsche has finally been able to tame the viscious understeer that plagued its previous models."

I hang out here more frequently than at Lansing Heritage because I find the history of AR interesting. For a period of time they dominated the field in technical advances and product prominance. But only for a period and then other companies caught up and eventually surpassed their best efforts.

Sad that we have to fight this constant battle of "what 40 year old speaker is better than anything since", or "what idiots modern product designers are".

David

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And by what engineering device did Villchur incorporate in his designs to control directivity to suggest this was his goal?

We've discussed it many times right here in the kitchen, and the objective is quite clearly stated in the Allison/Berkovitz paper. You've been snoozing through most of this, quite obviously.

[Come back once you've figured it out and know the answer.... :D ]

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Two additional references that Geddes left out. And of course Allison did something along this line with the IC-20, although the super-wide dispersion of the midrange and tweeter drivers made the result less precise than what Davis achieved with the dbx Soundfield model. The Allison unit did reduce sidewall reflections, however. I believe your AR Magic speaker did some very interesting things with this approach, although I am not familiar with how it handled the time/intensity issue.

Howard Ferstler

Thanks, Howard.

Bauer's concepts were frequently discussed around the MIT lab where I worked as an undergrad, and where Mark worked as a PhD candidate. The loudspeaker design field was very cooperative and mutually supportive in those days, and so it's not so easy to establish a clear precedent. In fact, the dBx people sometimes used to come over to run curves in AR's chambers, and were assisted by AR people with a bit of the design math.

In terms of the MGC-1, I considered the image stabilization that came from T-I-uh-trading, to be a happy byproduct, not particularly a goal.

-k

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David,

I completely agree with this post, thanks.

I never worked there, but was honored to tour the JBL/Harman facilities five times between 1984 and 1987. (This was just after Keele, Perkins, et al, and just before the era of Toole, Olive, Button, etc.) It was a world-class speaker engineering group, certainly in very the top tier, and toward the driver-centric end of the spectrum.

"Sad that we have to fight this constant battle of 'what 40 year old speaker is better than anything since', or 'what idiots modern product designers are'." Amen!!

And sad that contemporary internet historians need to project such inter-company competitive hostility onto the audio industry.

-k

Well, I guess I have to come to the defense of poor old JBL. Sure, an S7, S8 or Voice of the Theater are not the ultimate in transparency or freedom from coloration compared to what we have today, but then AR products from the same decade have been surpassed in those regards as well.

I was only with the company for a couple of years but I greatly admired their engineering (and still do). I don't know of any other company with as advanced transducers in terms of power handling and freedom from distortion. The 100 x 100 horn of the 4430 that Zilch refers to has the most amazingly well behaved and consistant horizontal and vertical polar curves of any transducer I have ever measured in 30+ years. The system was meant to be an advance on the S7 or 4300 series studio monitors that preceeded it, and it was.

These were studio monitors rather than theater speakers. Nothing wrong with theater speakers though. I'd recently spent an afternoon in the public library copying papers by Altec's John Hilliard from 1940's SMPTE journals. The level of engineering was very impressive. If you need the ouput to fill a cinema or auditorium then a small but accurate bookshelf speaker won't cut it.

"But what of accuracy reproducing acoustical instruments?" I think that was pretty good too, with the right models. I"m not a fan of the 4311/L100 generation but the L96, L112 and L150 and L250 got pretty good reviews as I recall. Usually with the odd preamble that "JBL, known for its rock and roll speaker has actually been able to design a product that suits all types of music." A bit like every Porsche 911 review has to end with "Porsche has finally been able to tame the viscious understeer that plagued its previous models."

I hang out here more frequently than at Lansing Heritage because I find the history of AR interesting. For a period of time they dominated the field in technical advances and product prominance. But only for a period and then other companies caught up and eventually surpassed their best efforts.

Sad that we have to fight this constant battle of "what 40 year old speaker is better than anything since", or "what idiots modern product designers are".

David

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Can we plot the effective AR3a Directivity Index from the measured in-room power response given in Fig. 34 and the total power at Fig. 17a of the Allison/Berkovitz paper?

Here's the composite response from 250 Hz up; I don't know what to do with the frequencies below there:

http://www.classicspeakerpages.net/IP.Boar...ost&id=4705

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"Porsche has finally been able to tame the viscious understeer that plagued its previous models."

David

Horrors!! A terrible gaf! I meant Oversteer!

David

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Can we plot the effective AR3a Directivity Index from the measured in-room power response given in Fig. 34 and the total power at Fig. 17a of the Allison/Berkovitz paper?

Here's the composite response from 250 Hz up; I don't know what to do with the frequencies below there:

http://www.classicspeakerpages.net/IP.Boar...ost&id=4705

That is an averaged in-room curve, likely measured a little beyond the critical distance of a number of living rooms. (For others, critical distance is the distance from the source in a reverberent field or room where the direct field and reverberant field just equal each other.) As such it is some blend of direct response, avereaged over a range of near-on-axis angles and power response as modified by each living rooms RT vs. frequency (actually mean alpha vs. F).

For D.I. you need a power response curve and an axial frequency response. Axial curve minus power response curve equals D.I. curve. I think think both curves have been published amongst the Allison papers, so it should be possible.

David

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How fortunate for people who make musical instruments they don't have to worry about lateral reflections or directivity index. Why is that? Oh yeah, musical instruments don't propagate sound laterally or vertically. Funny, of all the violin makers I've spoken with, not one ever touted the superior directivity index of his violins. What do you suppose the directivity index of this instrument is?

http://artsbeat.blogs.nytimes.com/2009/10/...ion/#more-46647

Or these?

http://www.steinway.com/steinway/catalogue/models.shtml

What a rare privilege I had to be able to hear the ex-Kochanski so many times in so many places including in my own home. It's a sound you never forget. I can say with extreme confidence that there isn't now and never has been a commercially sold electronic sound reproducing system that could come close to duplicating that sound except in an anechoic chamber where this remarkable musical instrument would sound horrible. To begin to understand why it sounds the way it does, you'd have to measure its amplitude versus spectral output at every angle in every plane under a wide variety of playing conditions. When you compare that to comparable data for ANY loudspeaker ever sold commercially, it becomes immediately obvious through inspection why the loudspeaker can't possibly sound like the violin. This would be the minimum just to build a machine that would sound like it, were it standing side by side with it. To build one that sounds the way it does in the audience when its being played on the stage of a concert hall, this would only be the starting point. Then you'd have to understand exactly what the acoustics of the hall does to that sound before it reaches your ears. To engineer that, you'd not only have to duplicate all that, you'd have to incorporate the acoustics of the room you're listening in into the design of the machine since you can't ignore it or defeat it.

By comparison to this task, the state of the art of the sciences of acoustics and electronic sound recording and playback engineering is a primitive black art. The expectation that results could be successfully achieved applying it are about as likely as midieval scholars who contemplated how many angels can dance on the head of a pin have of successfully launching a manned mission to the moon.

This is the mathematical problem I solved 36 years ago and whose implimentation I've been experimenting with ever since. My United States Patent was only one example of applying that model.

The good news I suppose if there is any is that the dumbing down of the public has been so effective that most people have no idea what these instruments or real music should sound like let alone care. It is remarkable how many students who come here to study string instruments or piano have never heard even a recording of a single piece of classical music let alone a live performance of one.

The bad news is that with such ignorance of the joy the beauty of the sound that real music can bring, or even the pale facsimile our recording technology is limited to, the standard sound system for most people is an mp3 player with ear buds and anything beyond the small speakers designed for desktop computers is considered overkill. The audio equipment market except for home theater has become a dwindling niche market which will probably suffer a major shakeout. Considering its failure to truly advance and technically innovate and the astronomical prices it asks for its output, that is long overdue.

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For D.I. you need a power response curve and an axial frequency response. Axial curve minus power response curve equals D.I. curve. I think think both curves have been published amongst the Allison papers, so it should be possible.

If we assume the axial response is flat with both controls advanced to max as stated in the literature, we should be able to approximate it.

2-pi axial is Fig. 5.

[The 4-pi axial curve (Fig. 9) is kinda "messy...." :D ]

Edit: From Toole, P. 379:

Sound power is intended to represent all the sounds arriving at the listening position.

Directivity index (DI) is defined as the difference between the on-axis curve and the sound-power curve. It is thus a measure of the degree of forward bias -- directivity -- in the sound radiated by the loudspeaker.

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What a speaker should do is input acoustic energy as smoothly into a room as possible. Whether it does that involves controlled, narrow directivity or wider angled, but still controlled directivity will depend upon the philosophical approach (and of course competency) of the designer. And whether the result of either approach satisfies the listener will depend upon the taste of that listener. Some like one type; some like the other type, and both individuals may be very competent themselves as listeners. The key is to have the speaker at the very least deliver smooth (and probably flat, although a downward slope towards the treble usually is beneficial, as is a mild elevation at the bass end) sound, with a decent bandwidth and distortion low enough to not have harmonics muddy the result.

+3 dB. :D

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Well, it is preposterous to even think of a loudspeaker reproducing the radiation pattern of a violin. Even if it could do it (and a weird design that sucker would have to be), it would then be unable to reproduce the radiation pattern of a trumpet or piano. Obviously, some kind of radiation-pattern compromise will be required.

What a speaker should do is input acoustic energy as smoothly into a room as possible. Whether it does that involves controlled, narrow directivity or wider angled, but still controlled directivity will depend upon the philosophical approach (and of course competency) of the designer. And whether the result of either approach satisfies the listener will depend upon the taste of that listener. Some like one type; some like the other type, and both individuals may be very competent themselves as listeners. The key is to have the speaker at the very least deliver smooth (and probably flat, although a downward slope towards the treble usually is beneficial, as is a mild elevation at the bass end) sound, with a decent bandwidth and distortion low enough to not have harmonics muddy the result.

As for absolutely and subjectively perfect duplicating the sound of a real-world, acoustic-instrument concert hall, well, I rather doubt that even your system could do that, given that we have a huge variability in recording quality from source to source. I think we can get a decent enough simulation to satisfy critical listeners, even though there is no way an audio rig can do a perfect job.

You seem to be mixing apples and oranges with some of your comments. You obviously think your sound-processor design will get us closer to realism, but at the same time you rail about the inadequacies of speaker design. Frankly, I think that speaker design these days and even for the past few decades has been pretty good, with the main limitation to absolutely realistic playback with an audio system involving two things: (1) recording quality and techniques and (2) the room/processor design and interface. Recording quality (at the beginning of the chain) is kind of hamstrung by the continued favoring of two channels (certainly, this is easier for engineers to deal with) and the room/processor design and interface situation (at the other end of the chain) is hamstrung by the nature of typical home-listening rooms, as well as financial limitations involving very complex processing and the need for lots of speakers to do the job. Whatever, no processor can overcome all of the limitations we have with most living-room layouts.

Frankly, I think you are being pretty unfair to the engineers out there who work to deliver the goods as best they can, given the impossible to solve nature of the problems. You make them sound like knuckle-dragging medievalists. As for your patent and research, something like that may have great potential (if it is as much like the Yamaha approach as you have indicated before, then obviously it has to be pretty good), but if that potential is not realized in practice the whole thing becomes worthless.

Howard Ferstler

Howard;

You tell me that this problem is unsolveable. Not merely that there is a point of diminishing returns but that there is a point beyond which no further return can be obtained.

You tell me that one problem is the variability of the source but what meager means were once incorporated in equipment to compensate for those variables have largely been removed from what purports to be the best of it.

You tell me that another problem is the acoustics of the listening room but there has been no serious engineering effort to deal with that problem on its own terms. Every effort to negate or defeat it has failed dismally.

The fact remains that on a scale of 0 to 100 where 0 represents never being able to convince a blindfolded listener with normal hearing acuity that he is hearing live music and not a reproduced recording and 100 means convincing him of that just about every time, the state of the art is still at 0. I contend it is not because the problem can't be solved but because it isn't even well understood.

Yet what purports to be the best available equipment has escalated from the price of a new car to the price of a new house. And you tell me that the engineers who design this stuff are doing a fine job. By what line of reasoning do you arrive at this conclusion?

"Frankly, I think you are being pretty unfair to the engineers out there who work to deliver the goods as best they can, given the impossible to solve nature of the problems. You make them sound like knuckle-dragging medievalists."

I think it is you who are being unfair...to the knuckle-dragging medievalists. They never claimed or suggested for one moment they'd ever get to the moon.

BTW let me clarify something. I contend that one Yamaha DSP unit exploited a loophole in my patent and in effect infringed on one aspect of it by duplicating the capability to generate an important algorithm. It meets that criteria by the most minimal margin possible and is the least effective embodiment of it. That means that it barely meets the specified criteria. In fact for virtually anyone it would be extremely difficult if not impossible to exploit it without additional knowledge. That algorithm is only one of many aspects of the invention. That is only an academic matter now. The patent expired a long time ago, that model is no longer manufactured, and as far as I can tell, all subsequent models made by both Yamaha and others do not perform similarly.

What a high fidelity sound systems "should do" is play recordings in a way that sound like real music to most people at least some of the time...especially when it costs as much as a house.

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