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In Reply to: RE: Orchestral-sized events are the worst "live reference" posted by josh358 on October 24, 2010 at 12:30:00
Toole has tried to correlate objective measurements with subjective listener preference. He found that a particular behaviour of amplitude response (on and off-axis) is preferred in blind listening tests. What he says is that there is no need to spend big money in order to obtain this preferred behaviour, hence the price figures indicated.
What is state of the art in loudspeaker design? In Toole's book its flat response on-axis and smooth behaviour off-axis. To that add a clean waterfall plot and correct time alignment. That whole package possibly cannot be made for $800, especially if on top of that you want high SPL with low distortion.
Klaus
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That's exactly the problem I have. As far as I know, it isn't possible to make a loudspeaker that covers the whole audio range, has smooth on-axis response and good dispersion, and plays cleanly at a level that's adequate to reproduce all performances of un-amplified acoustical instruments at that price. Also, while Toole's criteria are good ones insofar as they go (although as I think he himself points out, it's an open question whether time alignment is necessary to the reproduction of music as opposed to test signals), I don't think they're the only criteria that affect loudspeaker performance. For example, state-of-the-art imaging and soundstage depth are difficult to achieve: arguably only a few esoteric line sources do it, or come close, without compromising maximum output. Similarly, there are issues of non-linear distortion, diaphragm breakup, and room interactions. In the absence of acoustical room treatment, dipoles and cardioids seem to have certain advantages. The upshot is that state-of-the-art reproduction seems to remain the province of large, expensive, and esoteric devices -- ribbons, line sources, large electrostatics, and dynamics that use exotic cone and cabinet materials and construction and servo woofer control. What's more, there doesn't seem to be a loudspeaker, no matter how elaborate or refined, that's state-of-the-art in every respect.
Not at that price range, no. But you don't need to pay astronomical prices either. In my opinion the speakers of the link below come close to the ideal. They use waveguides and DSP, no magic ingredients.
Time alignment: whilst not absolutely necessary, it makes a difference, even to the tin ear that I am :-)
"State-of-the-art imaging", what exactly is that and how do you know that the speakers are delivering those particular goods? What is the reference when judging imaging?
Soundstage depth: this would relate to distance perception in rooms. Nielsen in AES paper 3069 references some of the relevant literature. His introductory comments are quite interesting: "Sound reproduced through a normal set of stereo loudspeakers or a pair of headphones often lacks the impression of depth. This may be due to improper recreation of the oroginal sound field at the listener's ear. However, it may also be because the perception of depth by the hearing is not as good as we expect it to be. A reproduction cannot be better than the reality."
State-of-the-art reproduction: it would appear that only wave field synthesis is capable of recreating the original sound field, but that's a technology I'm not at all familiar with and anyway, there seems to be a problem in terms of home user acceptance.
Klaus
Blumlein refers to the reproduction of depth in his original stereo patent, and I've seen a stereophonic demonstration film he made in the 30's in which the speaker's distance from the microphone is reproduced to spectacular effect. That affect won't occur to any significant degree with a monophonic recording. So while I think it's probably the future of sound reproduction, wave field synthesis isn't necessary to create a sense of depth in the stereo sweet spot, beyond the crude approximations of stereophony, anyway (MS stereo is really first order WFT with a single sample).
Room reflections seem necessary for this. In fact, according to Toole, first-order Ambisonics in an anechoic chamber didn't provide any sense of front-back localization at all! The same is true of headphone reproduction of conventional stereo recordings, which also lacks any contribution from the HRTF. That being the case, it's not surprising that it doesn't reproduce front-back perspective. That can be introduced in headphone listening with head tracking and real-time room and HRTF emulation -- see the latest issue of Stereophile for an interesting example.
To the best of my knowledge, very little is known about the psychoacoustical basis of depth perception. Toole's book, for example, essentially says "We have no idea." The reproduction of depth has something to do with recorded ambiance and listening room reflections, and it seems to be best reproduced by loudspeakers with uniform polar frequency and, according to one source, phase response.
AFAIK, to reproduce depth, two things are required: recorded reflections, and the ability to reproduce it in the listening room at an angular separation from the loudspeakers. Headphones and anechoic chambers don't satisfy these criteria. Neither does a loudspeaker with non-uniform frequency or phase response -- the issue here is apparently that the brain must be able to relate the reflections to the original source to interpret them as reflections or, perhaps, that spectral distortions introduced by the reproducer or room interfere with the brain's ability to localize the sound and gauge the acoustic on the basis of comb filtering and the HRTF.
The speakers in your link measure beautifully, and I'm all in favor of the use of DSP in loudspeakers. IMO, the high end industry is hopelessly stick-in-the-mud when it comes to the application of new technology. But, and it's a big but, I don't think a handful of measurements can completely characterize the audible performance of a speaker. The measurements aren't comprehensive enough and don't entirely reflect behavior in an actual listening room, and even if they were and they did, our understanding of psychoacoustics is too primitive to correlate the measurements completely with what we hear.
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