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Critic's Corner Discuss a review. Provide constructive feedback. Talk to the industry. |
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Critic's Corner Discuss a review. Provide constructive feedback. Talk to the industry. |
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Acoustic system resonators: recently reviewed at 6moons :http://www.6moons.com/audioreviews/acousticsystem/resonators.html
The promotional brochure (http://www.fastaudio.com/download/Ac_System_2004_EN.pdf) states that during playback these tiny (and expensive) cups add those harmonic overtones which had previously been lost in the recording process. Quite an amazing act if you actually don’t know what part of the overtones has been lost. Remains to be seen if any overtones have been lost at all, obviously no evidence is provided for that statement.
Further, these cups are, as outlined in the review, resonating at specific (overtone) frequencies, the sound these devices emanate therefore no longer merges with the direct sound (no precendence effect any more) and have therefore to be considered as secondary sound sources. Secondary sound sources: are we talking hifi here or what?Some (not all) speaker designers put efforts into getting rid of speaker cabinet edge diffraction, because the diffraction locations on the front baffle are secondary sound sources par excellence which cause interference effects (enhancement, cancellation) and hence coloration.
Some (not all) audiophiles put efforts into treating first reflections points in their room because first strong reflections, although not being considered as secondary sound sources, can cause coloration.
The first question now is “who would want deliberately place secondary sound sources in his/her listening room?†The promotional brochure states “one of the most unbelievable high fidelity productsâ€. How could an item that ADDS information to what is present on the record be classified as high fidelity?
The second question is “how loud has a secondary sound source to be in order to be audible, what are the thresholds?â€
The third question is “if these cups really do act as secondary sound sources, any object that has the capability to resonate at audible frequencies (Acoustic system resonators are allegedly tuned by ear!) will do that trick, so why spend large amounts of money (the 6moons reviewers had $8000 worth of cups in their room). Where is the evidence that only cups of that dimensions and metallurgical compositions are effective, but nothing else? Franck Tchang’s patent btw. allows for quite a range of dimensions (1 to 10 cm diameter) and compositions (30-50% silver (silver cups), 65-85% gold + 10-20% silver (gold cups)).
The fourth question is “how is it possible to tune the cups by ear?†The resonance frequencies of the various cups have been determined (German audio mag Stereoplay, using laser interferometry) to be at
30 kHz (secondary resonances at 6 and 15 kHz) for gold
20 Khz for special gold
19 Khz for platinumTuning by ear at 6 and 15 Khz would appear to be possible (if you are young enough), but frequencies around and above 20 kHz???
The fifth question is “in order to excite resonance there must be a exciting source signal of about the same frequency, how can a CD (or LP) excite resonance above 20 Khz?????
The sixth question is “if certain harmonic overtones have been lost during the recording process and are hence not present on the CD (or LP), how can they excite the cups at their specific resonance frequencies in order to re-constitute these frequencies?â€
The seventh question is “what about masking effects, within the critical bands and due to upward spread?â€
The eigth question is “during Stereoplay’s lab tests the cups were placed about 20 inches in front of the speaker within the direct sound field. During normal use, the cups are placed somewhere outside the direct sound field and at distances greater than 20 inches. Even if there’s signal above 15 kHz on the CD of useable (read audible) magnitude, how high is the sound level at these frequencies at the off-axis location of the cups, taking into account the further fact that all tweeters are beaming at those frequencies? Is it enough to excite the cups to resonance?â€
The 6moons review states that one can learn a lot from the French patent bureau: I’ve read the patent and it does not contain any background information (e.g. room acoustics, perception issues) whatsoever. In this particular case you don’t learn anything from that patent other than what’s necessary for drafting the claims.
Since any object that can resonate (in the audible range) will do the trick, I placed a cup made from gold/silver, a small silver bell, a small tin sphere between and behind the speakers and on the right wall (the latter in the hope to generate an asymmetric image shift), just like it was done in the review. I used excerpts from the EBU SQAM CD
http://www.ebu.ch/en/technical/publications/tech3000_series/tech3253/index.php
and tracks from Chesky’s Jazz Sampler vol. 1 (JD37) which also contains the LEDR
http://www.stereophile.com/reference/772/index.html
test tracks. I could not hear any effect whatsoever.
I also tried the “wonder-where-the-bass-has-gone†feature described in the review, the bass remained as solid and thunderous as always. Maybe it is because such tiny cups are completely invisible for low-frequent sound waves? Next time somebody will claim that such devices can serve the purpose of eliminating room modes!
Now these little thingies cost a lot more than the average audio tweak, but that fact did not stimulate the reviewers to have a closer look. No attempt to find out how they work, if at all. Why didn’t they ask acoustics and perception experts for an educated opinion and/or for some measurements. No, yet another “we rely on what we hear†review.
As German distributor Fast Audio says : “Scientific explanations are very complex, particularly in the case of the resonators, as they have to define the relationship between low-level overtones, diffusion effects and psycho-acoustic perception. Luckily the quality of these products is easy to appreciate without knowledge of the background theory.â€
Yeah, great, no explanation. As usual.
And another rave review. As usual.
Klaus
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Topic - Acoustic system resonators review – another case of “Believing is hearing� - KlausR. 02:51:09 09/18/06 (1)
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