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#1
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On testing speakers
Here's an article that appeared in the Nov 2004 issue of
Test & Measurement World, on Floyd Toole's speaker performance tests. http://www.reed-electronics.com/tmwo.../CA475937.html -- -S It's not my business to do intelligent work. -- D. Rumsfeld, testifying before the House Armed Services Committee |
#2
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Steven Sullivan wrote:
Here's an article that appeared in the Nov 2004 issue of Test & Measurement World, on Floyd Toole's speaker performance tests. http://www.reed-electronics.com/tmwo.../CA475937.html They still haven't quite caught on to how to design a speaker. They are still restrained by standard "engineer think" as taught in college, with their anechoic chambers and measurements of direct field frequency response. Statements like "loudspeakers should be as neutral and transparent as possible, and technical measurements should be able to demonstrate whether they are or not" show no new thinking and no way out of the hole they're in. I had a continuing argument with Floyd Toole in the AES Journal about his CRC experiments on evaluating speakers. My main complaint was that he was only testing direct firing speakers, and drawing his conclusions based on only that type of speaker. He was living in this microcosm of real world speakers that were out there and making conclusions like "speaker preference corellates with smoothness of frequency response on axis, and how smooth it falls off when you go off axis." Plus, he was using a room that was too small, and too dead to bring out most of the off-axis consequences of speaker radiation patterns. Now look at their comment about speaker design in this article. "That's rubbish," said Toole. +/-3 db can be shrill, if a speaker's response exhibits a midrange rise from -3 dB to +3 dB, or honky, if it exhibits a +6-dB midrange peak in an otherwise flat response. In addition, a +/-3-dB range can include many troubling, audible resonance points. If you can't achieve a +/-3-dB spec, said Toole, "you're in deep trouble. +/-3 dB is a giveaway. +/-2 is better, and if you reach +/-1, well, you have my attention." But ultimately, he said, you don't need a single spec--"You need a graph!" I know from all of my experience and speaking with and reading many others, that the direct field response can be varied all over the place and doesn't matter much, except for lateral localization from the leading edge transients carried by the direct sound. Sean Olive goes on about the power response: " 'not very. In fact, the sound-power model suggests that if you turn a speaker around so it's facing a wall you'll have the same listening experience, and we know that's not the case.' Indeed, Olive has discovered a negative correlation between CU's results and listener preferences and has developed his own models (Ref. 2) that indicate what objective measurements best correspond to subjective listener preferences." He draws these conclusions based on his microcosm of listening to and testing only these direct firing speakers! One fellow, Devantier, found out that "The data he gathered (Ref. 3) demonstrated that direct sound and early reflections¡ªwhich aren't represented in a sound-power model¡ªare significant contributors to the sound and spatial quality of a loudspeaker and that these contributors must be represented in any objective model that purports to mimic subjective experience." But instead of using that information to design radiation patterns that take advantage of that, and believing that sound power response is not related to speaker preference, he concludes that consumer loudspeakers are a case "where you have a 4¦Ð environment and know you want to minimize room effects." They are doing all of these experiments, measuring all of these factors, but making conclusions without a model of subjective loudspeaker performance that correlates to live sound. They are assuming the "engineer think" model of "accuracy" and smooth frequency response, then doing experiments that prove only that factor, and drawing conclusions based on these entering assumptions. That is circular reasoning of the highest order. Take, as just one example, our discussion above of the sonic effect of Linkwitz's Orion design. Most contributors stated and knew that the dipolar pattern of the speaker contributed immensely to its sound, especially the soundstaging. A side benefit of this multi-directional pattern is that it makes the instruments sound more real, more detached from the speakers themselves, more right there in the room with you. This is an enormous realization, something that must be studied and taken into account in any loudspeaker research or design program. I don't think that the Canadians have caught on to that yet. To prove me wrong, I want to see some speakers coming out of Harman with radiation patterns other than direct firing, with all of the drivers on one side of the box. I don't really know if they do have such a thing or not - even maybe just a tweeter on the back a'la Snell, but I somehow doubt it. Someone please educate me if I'm wrong. Gary Eickmeier |
#3
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On 24 Feb 2005 01:03:13 GMT, Gary Eickmeier
wrote: A side benefit of this multi-directional pattern is that it makes the instruments sound more real, more detached from the speakers themselves, more right there in the room with you. This is debatable. You are describing a common and valid observation but how real or accurate that representation is is not yet verified. To prove me wrong, I want to see some speakers coming out of Harman with radiation patterns other than direct firing, with all of the drivers on one side of the box. I don't really know if they do have such a thing or not - even maybe just a tweeter on the back a'la Snell, but I somehow doubt it. Someone please educate me if I'm wrong. The Revel Ultima Studios and Salons from the Harmon conglomerate have a rear-firing tweeter "that flattens the 'in-room' response, resulting in superior 'air' and detail." Kal |
#4
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Gary Eickmeier Said:
To prove me wrong, I want to see some speakers coming out of Harman with radiation patterns other than direct firing, with all of the drivers on one side of the box. I don't really know if they do have such a thing or not - even maybe just a tweeter on the back a'la Snell, but I somehow doubt it. Someone please educate me if I'm wrong. I respond: Perhaps nobody wants to get involved in the likely lawsuit with Bose, should somebody else want to design a GOOD direct/reflecting speaker. |
#5
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Gary Eickmeier wrote:
Steven Sullivan wrote: Here's an article that appeared in the Nov 2004 issue of Test & Measurement World, on Floyd Toole's speaker performance tests. http://www.reed-electronics.com/tmwo.../CA475937.html They still haven't quite caught on to how to design a speaker. They are still restrained by standard "engineer think" as taught in college, with their anechoic chambers and measurements of direct field frequency response. Statements like "loudspeakers should be as neutral and transparent as possible, and technical measurements should be able to demonstrate whether they are or not" show no new thinking and no way out of the hole they're in. I had a continuing argument with Floyd Toole in the AES Journal about his CRC experiments on evaluating speakers. My main complaint was that he was only testing direct firing speakers, and drawing his conclusions based on only that type of speaker. He was living in this microcosm of real world speakers that were out there and making conclusions like "speaker preference corellates with smoothness of frequency response on axis, and how smooth it falls off when you go off axis." Plus, he was using a room that was too small, and too dead to bring out most of the off-axis consequences of speaker radiation patterns. Now look at their comment about speaker design in this article. "That's rubbish," said Toole. +/-3 db can be shrill, if a speaker's response exhibits a midrange rise from -3 dB to +3 dB, or honky, if it exhibits a +6-dB midrange peak in an otherwise flat response. In addition, a +/-3-dB range can include many troubling, audible resonance points. If you can't achieve a +/-3-dB spec, said Toole, "you're in deep trouble. +/-3 dB is a giveaway. +/-2 is better, and if you reach +/-1, well, you have my attention." But ultimately, he said, you don't need a single spec--"You need a graph!" I know from all of my experience and speaking with and reading many others, that the direct field response can be varied all over the place and doesn't matter much, except for lateral localization from the leading edge transients carried by the direct sound. Sean Olive goes on about the power response: " 'not very. In fact, the sound-power model suggests that if you turn a speaker around so it's facing a wall you'll have the same listening experience, and we know that's not the case.' Indeed, Olive has discovered a negative correlation between CU's results and listener preferences and has developed his own models (Ref. 2) that indicate what objective measurements best correspond to subjective listener preferences." He draws these conclusions based on his microcosm of listening to and testing only these direct firing speakers! One fellow, Devantier, found out that "The data he gathered (Ref. 3) demonstrated that direct sound and early reflections??which aren't represented in a sound-power model??are significant contributors to the sound and spatial quality of a loudspeaker and that these contributors must be represented in any objective model that purports to mimic subjective experience." But instead of using that information to design radiation patterns that take advantage of that, and believing that sound power response is not related to speaker preference, he concludes that consumer loudspeakers are a case "where you have a 4?? environment and know you want to minimize room effects." They are doing all of these experiments, measuring all of these factors, but making conclusions without a model of subjective loudspeaker performance that correlates to live sound. They are assuming the "engineer think" model of "accuracy" and smooth frequency response, then doing experiments that prove only that factor, and drawing conclusions based on these entering assumptions. That is circular reasoning of the highest order. No, because they're taking it one step further -- actual listening tests with actual listeners and actual speakers (AIUI, from different manufacturers, not just Harman/JBL). It may be that they aren't trying all the various speaker 'topologies' that are out there -- but it seem to me they're trying hard to draw reliable conclusions from the sample set they *do* use. Having not seen Olive's or Toole's actual papers from 2004, I can't say how much they've generalized their conclusions. Take, as just one example, our discussion above of the sonic effect of Linkwitz's Orion design. Most contributors stated and knew that the dipolar pattern of the speaker contributed immensely to its sound, especially the soundstaging. A side benefit of this multi-directional pattern is that it makes the instruments sound more real, more detached from the speakers themselves, more right there in the room with you. Perhaps, but, that conclusion hasn't been formalized nearly as rigorously as Olive/Toole's, has it? This is an enormous realization, something that must be studied and taken into account in any loudspeaker research or design program. I don't think that the Canadians have caught on to that yet. See above. To prove me wrong, I want to see some speakers coming out of Harman with radiation patterns other than direct firing, with all of the drivers on one side of the box. I don't really know if they do have such a thing or not - even maybe just a tweeter on the back a'la Snell, but I somehow doubt it. Someone please educate me if I'm wrong. I would only want to see that if Harman had in fact tested that speaker topology properly in their setup. If they do so and find the topology wanting, and can provide data indicating why this is so, I wouldn't expect them to sell such speakers. Has anyone asked Toole/Olive/etc *recently* if and why they aren't fans of non-direct radiator designs? -- -S It's not my business to do intelligent work. -- D. Rumsfeld, testifying before the House Armed Services Committee |
#6
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Gary Eickmeier wrote:
They are doing all of these experiments, measuring all of these factors, but making conclusions without a model of subjective loudspeaker performance that correlates to live sound. Neither is anyone else. What Harman is doing is trying to make loudspeakers that correlate to *something*--namely, listener preferences, determined with at least some scientific rigor. They are assuming the "engineer think" model of "accuracy" and smooth frequency response, then doing experiments that prove only that factor, and drawing conclusions based on these entering assumptions. That is circular reasoning of the highest order. Not circular at all, unless you can show that their subjective evaluation method predisposes test subjects to prefer accurate speakers. Now, it may be that they are only testing one type of speaker, and within that category accuracy correlates best with listener preferences. Perhaps if they threw some planars, the Orions, or Bose 901s into the mix, they'd discover that there are factors that outweigh accuracy in listeners' minds. (Perhaps, too, they already have. I don't think they reveal what speakers they test.) But somebody needs to do that work. To just say, "Unidirectional speakers aren't good, and therefore any test that shows them to be good is flawed" is to stand on very shaky ground. bob |
#7
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wrote in message ...
Gary Eickmeier wrote: They are doing all of these experiments, measuring all of these factors, but making conclusions without a model of subjective loudspeaker performance that correlates to live sound. Neither is anyone else. What Harman is doing is trying to make loudspeakers that correlate to *something*--namely, listener preferences, determined with at least some scientific rigor. They are assuming the "engineer think" model of "accuracy" and smooth frequency response, then doing experiments that prove only that factor, and drawing conclusions based on these entering assumptions. That is circular reasoning of the highest order. Not circular at all, unless you can show that their subjective evaluation method predisposes test subjects to prefer accurate speakers. Now, it may be that they are only testing one type of speaker, and within that category accuracy correlates best with listener preferences. Perhaps if they threw some planars, the Orions, or Bose 901s into the mix, they'd discover that there are factors that outweigh accuracy in listeners' minds. (Perhaps, too, they already have. I don't think they reveal what speakers they test.) But somebody needs to do that work. To just say, "Unidirectional speakers aren't good, and therefore any test that shows them to be good is flawed" is to stand on very shaky ground. Gary didn't say that. He said that Floyd Tool and his gang at Harmon have to the best of his knowledge limited themselves to unidirectional speakers. Therefore their conclusions are of necessity somewhat circumscribed, and it may be in fact that if bi-polar or omidirectional speakers were tested, and the test setup provided them the proper configuration and environment, that they may very well be preferred over "flat and neutral" direct firing speakers. At least he believes they will. Finally, he thinks the engineers at Harman are missing this possibility given their long developmental history of dealing with only unidirectional speakers. |
#9
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On missing the point -- I read the article in T&M when it showed up last
fall -- the point that the T&M authors make is that "golden ears" and trained "neophyte ears" have the same outcomes when it comes to the judging the merit -- it's all about the statistics. "Steven Sullivan" wrote in message ... Here's an article that appeared in the Nov 2004 issue of Test & Measurement World, on Floyd Toole's speaker performance tests. http://www.reed-electronics.com/tmwo.../CA475937.html -- -S It's not my business to do intelligent work. -- D. Rumsfeld, testifying before the House Armed Services Committee |
#10
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Harry Lavo wrote:
Gary ... said that Floyd Tool and his gang at Harmon have to the best of his knowledge limited themselves to unidirectional speakers. Therefore their conclusions are of necessity somewhat circumscribed, and it may be in fact that if bi-polar or omidirectional speakers were tested, and the test setup provided them the proper configuration and environment, that they may very well be preferred over "flat and neutral" direct firing speakers. At least he believes they will. Finally, he thinks the engineers at Harman are missing this possibility given their long developmental history of dealing with only unidirectional speakers. Based on Dr. Toole's own comments during a CEDIA presentation I attended, plus what I've inferred from reading this article, there is nothing about Harmon's experiments that specifically restricts them from including non-unidirectional speakers...and moreover, should they include non-unidirectional in their test, it appears quite clear that the criteria by which listener's find a speaker preferrable would also apply to all speakers regardless of their readiation pattern. In a pathetically oversimplified nutshell, Harmon/Toole is saying that the SUM of a speaker's direct response and the indirect room response should be smooth and (relatively) flat in order for listener's to find that speaker's sound appealing. So why shouldn't we believe the same will hold true for a speaker that just happens to intentionally put more energy off-axis? The listener will still perceive some direct sound, and the listener will still perceive the indirect room response. Based on Harmon's experiments the speakers (unidirectional, bipolar, omnidirectional, or whatever) whose SUMMED direct & indirect outputs are smoothest will be perceived as most pleasurable to listen to. Gary's complaint seems a bit of a strawman, IMHO. |
#11
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Gary Eickmeier wrote:
They are still restrained by standard "engineer think" as taught in college, with their anechoic chambers and measurements of direct field frequency response. I don't normally participate in these threads but your statements are such a misreprentation of the facts stated in our research findings that I must step in and correct you. I would encourage you to first read the AES papers instead of speculating on what speakers, rooms and measurements were used. The information is all contained in the references listed at the end of the Test & Measurement World article. We measure loudspeakers in anechoic chambers because it is the only place you can accurately measure and predict the qualities of the direct, early-reflected and reverberant sounds produced by the loudspeaker in a room. Neither in-room or sound power measurements can do this. In reference 5 of the T&MW story I developed and compared preference models based on in-room and sound power loudspeaker measurements. They both produced less accurate predictions of loudspeaker preference ratings than a model based on our set of spatially-averaged anechoic measurements. Contrary to your statements, the quality of the direct sound was found to be an important predictor of loudspeaker preference in addition to off-axis response and bass performance. Both sound power and in-room measurements cannot accurately show these things separately. Clearly the room acoustics/ speaker directivity are important variables that will be addressed in the next phase of research. Statements like "loudspeakers should be as neutral and transparent as possible, and technical measurements should be able to demonstrate whether they are or not" show no new thinking and no way out of the hole they're in. Wow! I have been telling our competitors something this for years. Please listen up competitors: qualities such as transparency, neutrality are all money-losing,outdated performance targets that "show no new thinking". Models that predict consumer preference ratings based on measurements are also a huge waste of time & money that will put you further into "the hole ". The money you save not fixing those nonlinearities can be redirected towards more important factors such as side-firing multi-directivity loudspeakers highly preferred by listeners... Hedraws these conclusions based on his microcosm of listening to and testing only these direct firing speakers! The generalized model I show in reference 5 was based on listening tests performed on 70 different loudspeaker models sampled from a wide range of prices, brands,countries of origin and directivity. While the vast majority were front-firing designs some designs included horns, dipoles, bipoles, side-firing/rear-firing tweeters, omni-directional patterns. Front-firing speakers represent the vast majority of most speakers sold; it's not "just a Canadian thing..", it's an International thing. Our test sample reflected this reality. Directivity was not a good predictor of preference, indicating that you need to get the frequency response correct first. A side benefit of this multi-directional pattern is that it makes the instruments sound more real, more detached from the speakers themselves, more right there in the room with you. This is an enormous realization, something that must be studied and taken into account in any loudspeaker research or design program. I don't think that the Canadians have caught on to that yet. The cause and effect for this are well-known. Wider-dispersion speakers can produce stronger side wall lateral reflections that create more decorrelated signals at the ears. This creates a sense of spaciousness and envelopment, also characteristic of rectangular shaped concert halls. I frankly do not see the need for side-firing patterns given today's 5.1 and 7.1 setups where the additional side surround speakers can produce the same envelopment cues, so long as the recording engineer puts them in the mix. There is another reason why multi-directional speakers are not so ideal. 99% of the recordings/films are mixed on direct radiator front-firing loudspeakers. In fact it is embodied in the music recording industry guidelines on how to record and mix surround music (see http://www.grammy.com/pe_wing/5_1_Rec.pdf). If consumers want to better hear what the artist intended then they would be wise to use similar speakers at home. Fortunately, most consumers already do. Cheers, Sean Olive Mananger Subjective Evaluation, R&D Group Harman International |
#12
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Gary Eickmeier wrote:
This is an enormous realization, something that must be studied and taken into account in any loudspeaker research or design program. I don't think that the Canadians have caught on to that yet. Then how do explan Mirage and Paradigm's current and/or previous bipolar/omnidirectional offerings, e.g. Mirage OM line or Paradigm Esprit BP? And Paradigm's current Reference and Signature surrounds have drivers on multiple sides. -- Jason Kau IS FOR EMAIL IS FOR SPAM http://www.cnd.gatech.edu/~jkau |
#13
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Steven Sullivan wrote:
Has anyone asked Toole/Olive/etc *recently* if and why they aren't fans of non-direct radiator designs? It is dated "31 January, 2002", but they write about that in http://www.harman.com/wp/index.jsp?articleId=120 http://www.harman.com/wp/pdf/Loudspeakers&RoomsPt1.pdf Pages 9 and following. -- http://www.mat.uc.pt/~rps/ ..pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC) Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94 |
#14
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Harry Lavo wrote:
wrote in message ... Perhaps if they threw some planars, the Orions, or Bose 901s into the mix, they'd discover that there are factors that outweigh accuracy in listeners' minds. (Perhaps, too, they already have. I don't think they reveal what speakers they test.) They don't reveal specifically which speakers they test, but they mention, in general terms, some kinds of speakers they have tested. Finally, he thinks the engineers at Harman are missing this possibility given their long developmental history of dealing with only unidirectional speakers. http://www.harman.com/wp/index.jsp?articleId=121 http://www.harman.com/wp/pdf/Loudspeakers&RoomsPt2.pdf Page 17: "Four expensive and highly regarded loudspeakers are evaluated in the shuffler room, in a double-blind test." "A Mountain Skyline: $5000/pr This speaker has a bunch of things going on. Clearly the designers didn t believe that flat was necessary, or they didn't know how to achieve it. Not only are the general trends not flat, but superimposed are peaks and dips suggesting resonances. The proof that they are resonances is in the fact that the patterns are repeated in all of the curves. The directivity is interesting, being zero up to 100 Hz (the woofer) and then abruptly rising to about 5 dB and hovering around that all the way to 20 kHz. Since 4.8 dB is the directivity of a dipole, we could suspect that this is a hybrid system with a panel loudspeaker operating above about 100 Hz. The woofer exhibits a significant bump and then rolls off below about 60 Hz. No subwoofing here." You can speculate which "highly regarded loudspeaker" costs about $5000/pr and has a panel loudspeaker plus woofer. -- http://www.mat.uc.pt/~rps/ ..pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC) Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94 |
#15
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Gary Eickmeier wrote:
wrote: Now, it may be that they are only testing one type of speaker, and within that category accuracy correlates best with listener preferences. Perhaps if they threw some planars, the Orions, or Bose 901s into the mix, they'd discover that there are factors that outweigh accuracy in listeners' minds. (Perhaps, too, they already have. I don't think they reveal what speakers they test.) But somebody needs to do that work. To just say, "Unidirectional speakers aren't good, and therefore any test that shows them to be good is flawed" is to stand on very shaky ground. Just a couple of quick observations for you to chew on: First, we are not "doing" accuracy with the loudspeaker end of the reproduction chain, in the same sense that we think of with amplifiers or sources. Suppose, for example, that we agree that reproducing a two channel recording using some signal processing and surround speakers sounds better than doing it with just two speakers. Many of you reading this would agree with that, so not too radical so far. But if we were to measure the resultant sound with any system you can think of, the frequency response and phase and timing of all of the room effects would drive the "engineer think" mind crazy. Second, they seem to be completely ignoring the Bose research that showed that power response IS extremely important, and that the spatial nature of sound is perhaps even more important than the frequency response as measured on axis in an anechoic chamber. Mark Davis's work, which led to an amazing speaker called the DBX Soundfield One, found that the audible characteristics of speakers are the dynamic radiation pattern and frequency response in all directions. That being the case, a speaker designer who didn't take radiation pattern into account in his design would be ignoring half of the factors that contribute to audibility of differences between speakers, or their relationship to the live event. The answer, as I have stated many times in this and other forums, is to focus on the image model of the live sound vs the reproduction. An image model is just a plan view of the speakers (or instruments) and all of their reflections, or reflected images, in the surrounding walls. If the image model of the reproduction soundfield can be made to come closer to that of the live situation, it will sound more like it, and therefore more real. To design speakers, therefore, you work backward from such an image model to the radiation pattern required to accomplish it. This makes the loudspeaker, in effect, an Image Model Projector, using the whole room and its surfaces to create its sound. I could tell this to the Harman people point blank, in so many words, and it would go right over their heads, because it doesn't jibe with anything they teach in engineering school. Well, that's a curious claim , because Toole et al. are *deeply* into surround sound these days. Apaprently it has not driven their 'engineer think' minds crazy. e.g. http://www.harman.com/wp/index.jsp?articleId=120 -- -S It's not my business to do intelligent work. -- D. Rumsfeld, testifying before the House Armed Services Committee |
#16
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John Walton wrote:
On missing the point -- I read the article in T&M when it showed up last fall -- the point that the T&M authors make is that "golden ears" and trained "neophyte ears" have the same outcomes when it comes to the judging the merit -- it's all about the statistics. So, who, pray tell, is missing the point? "Steven Sullivan" wrote in message ... Here's an article that appeared in the Nov 2004 issue of Test & Measurement World, on Floyd Toole's speaker performance tests. http://www.reed-electronics.com/tmwo.../CA475937.html -- -S It's not my business to do intelligent work. -- D. Rumsfeld, testifying before the House Armed Services Committee -- -S It's not my business to do intelligent work. -- D. Rumsfeld, testifying before the House Armed Services Committee |
#17
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I am still using a pair of DBX Soundfield One speakers. Each tower has
14 drivers. Four 10" woofers (one on each side), four mid range and 6 tweeters in a hex pattern. They provide a very airy and balanced sound by reflecting off of the walls. ---MIKE--- |
#18
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Jason Kau wrote:
Gary Eickmeier wrote: This is an enormous realization, something that must be studied and taken into account in any loudspeaker research or design program. I don't think that the Canadians have caught on to that yet. Then how do explan Mirage and Paradigm's current and/or previous bipolar/omnidirectional offerings, e.g. Mirage OM line or Paradigm Esprit BP? And Paradigm's current Reference and Signature surrounds have drivers on multiple sides. By "Canadians" I am just referring to the CRC research program, not Canadian speaker makers. I think the Mirages help prove my points. Gary Eickmeier |
#19
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Sean,
I would be more interested in your reaction to my second post, the one on the 24th at 9PM. It does a better job of bypassing all of the chit-chat and suggesting some avenues of research that are perhaps different from what you are used to. Also shows a picture of my speaker that I made some 15 years ago. And no, I am not trying to hawk something - I am basically a failed industrial designer (career got sidetracked in the Air Force during Viet Nam era) and am doing more with photography and video than audio. I haven't been able to pursue my big ideas because I don't know much about building, measuring, and re-building the damn things. My engineer friends aren't all that interested in developing someone else's ideas either. But I would be interested in your reaction to my ideas. I never could get Floyd's complete attention, because he was always so busy. I respect his vast knowledge and fastidiousness, but sometimes (back when I was into all this stuff) I wanted to just stand in front of him and say STOP IT! Stop all this conventional thinking about measurement, accuracy, resonances, directivity, decreasing the effects of reflections in rooms - reformat and reprogram. For your inspiration read the original Bose research paper, where they went into the concert hall and discovered the spatial nature of sound and its importance; read Mark Davis's paper on the Soundfield One; some of Dave Moulton's work, Art Benade's "From Instrument to Ear in a Room: Direct or Via Recording," and then, if you're not howling with laughter yet, my magnum opus at http://aes.org/publications/preprint...nts_search.cfm Finally, here is a paradigm for you to think about: take three perfectly omnidirectional loudspeakers into a good sounding concert hall. These will represent typical instruments or sound sources (perfect point source and all that). Place them at stage left, center, and right, run a series of test signals thru them so that you know exactly what is going into them - signals such as pink noise, impulses, and some steady tones. Measure everything you want about the resultant sound from back in a good seat in the audience, and also make a binaural recording from that spot. This is your reference source. Now record the output of that setup with typical modern recording methods such as John Eargle might use. This is your reference recording. Now, take that recording into a home type listening room and reproduce it with speakers of various designs, looking for which ones come closest to both the measurements taken in the concert hall of the original, and the binaural recording of the original. You can even make a new binaural recording of the playback and compare it with the original one. Measure the IACC with a binaural head at the listening position and graph it. Compare that with the concert hall measurement. Measure the direct to reflected ratios in the two spaces. All of these things are related mainly to audibility of differences between the live event and the playback, and NOT to accuracy as compared to a RECORDING. That is the difference in direction I would propose for your company or any other that wants to try something different from the same old same old. Of course, it has all been done before, but not everyone agrees with the type of speaker that resulted from it... Gary Eickmeier |
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