Yes or should I take the route of Brian's funny picture?
I have quite a few old Dayton-Wright ESL elements sitting around and some old matching transformers, HV power supplies, meagohm resistors, rubber gloves, fiberglass tools, prayer beads, etc.
Seems like a feasible concept to mingle L and R panels in a middle speaker. The ESL drivers would simply take their drive from their respective HV and high-signal sides (quite different from doing the forbidding series-parallel impedance arithmetic when adding cone drivers).
In the absence of a dedicated center amp, hard to control loudness or do EQ.
The three speakers might have 20 6x15 inch ESL driver-panels arranged like this:
L L L -- L R L R --R R R
L L L -- L R L R --R R R
or the middle like:
L L R R
L L R R
The 6-driver black frame below, built in 1978 and waiting to come back to life, has outside size 28x44 inches, on the surface of a cylinder.
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For a lot of TV, you'd be better off without any sound... and I'm not just thinking of the chemistry fun we had back in the 60s watching TV with the sound off.
If you read Toole, there are many places spread around where he gives solid evidence that a physical center speaker in a stereo system does a lot of good for the sound at sweet-spot listening and more so for groups.
Certainly you are not intending to drive every panel with the full frequency range. How will you distribute the treble frequencies in that arrangement?
Rudolf
Harumph, certainly not!!!
Interestingly, each of these panels do the treble up to dogs-ear range far better than Mike Wright's later XG models with the welding gas bag. Hear that, Quad users? The XG models, up to 15kV, no kidding, do 65-8kHz pretty good using 10 iterations of just this one style of panel - and an extra ceramic horn tweeter was added for the top end. Compared to cone systems with odds and ends of cardboard and aluminum shaking out the sound, it is very elegant.
When used last, crossed at 140 Hz, 24 db/8ave to mixed bass. They have great big air gaps, eh.
While I was as happy as could be back then (ESL fans overlook many flaws in choosing to live with ESLs), now that I am in the wiser company of this forum, I am not sure how they'd sound to my ears today in the lower range.
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Gawd, microphones hate that kind of set-up!
Well, my old panels in the picture above sounded really great, esp. driven directly by a high-voltage Sanders-like amp. So is there any evidence that kind of "interference" is an issue for human ears?
In many places, Toole denies the importance of comb-filter phenomena. Maybe I am wrong to grab that by way of analogy but seems the same kind issue that looks terrible in theory or on graphs, but happens not to be audible.
Beaming is an important issue but all kinds of fixes - like my cylinder.
The hi-fi biz has a long history of fixing flavor-of-the-month obstacles while ignoring main issues.
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When Toole denies the importance of comb-filter phenomena, it is almost always with regard to reflections. I don't see any place where he discusses the interference of multiple identical direct sources. Page 147/148 in Sound Reproduction comes closest IMHO.
True enough, as best as I can recall. But I can still appeal to the analogical and inspirational value of his dismissal of lots of horrible theoretical concepts that have no aural impact.
But it may surprise you that I am not over-awed by the iron-grip of "laws" based on modeling.
Can you answer this about the interference or filter concepts applied to multiple drivers. Does the model assume the sound arises from a point source?
Hard for me to imaging some sort of "hard" interaction happening between two ESL drivers (or even cone drivers) that are 6 x 15 inches. And if the impact of interaction is smeared all over the frequency map, hard to imagine anybody (but a mic) can hear it except on test tones. Needs explaining.
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Yes, a wonderful, deep, very sophisticated examination of 3-channel sound. Much too deep for me
Funny thing, when he addresses how to play stereo (ummm, the stuff we get on our radios and CDs, eh) using 3 speakers, he says clearly enough, golly, the best way is to take L and R and just add-em-together Klipsch style and pump into the center speaker.
I also found it re-assuring when (in 1990) he thinks about how to place your center speaker in the middle of the TV, he says, good move is to use two flanking center speakers (my practice and works nice).
Quote:
Originally Posted by Bigun
My HT set up is 5.1 but I haven't yet connected the centre channel for want of a short cable. .......
I see a centre channel as problematic for placement. .......
Two votes for skipping the center....
---------------------------------------------------
Gentlemen,
There is more to life than Home Theater and television (much more ....)
There are reasons to add a center channel for an old-fashioned hobby called listening to music. We used to call it "stereo" back in the old days.
The implementation is different than the HT type of center channel (level and bandwidth), but it can do some remarkable things for stereophonic effect when enjoying music.
Please read the earlier posts.
Originally Posted by Bigun
My HT set up is 5.1 but I haven't yet connected the centre channel for want of a short cable. .......
I see a centre channel as problematic for placement. .......
Two votes for skipping the center....
---------------------------------------------------
Gentlemen,
There is more to life than Home Theater and television (much more ....)
There are reasons to add a center channel for an old-fashioned hobby called listening to music. We used to call it "stereo" back in the old days.
The implementation is different than the HT type of center channel (level and bandwidth), but it can do some remarkable things for stereophonic effect when enjoying music.
Please read the earlier posts.
That doesn't seem to be what he said AT ALL.
Gerzon wrote: "The problem of reproducing 2-channel stereo over three loudspeakers turns out to have some reasonable solutions – although the results are obviously not as good as full 3-channel stereo. For narrow stage widths, 2-channel material can simply have its left and right channels panned (using 3-channel panpots) to the desired positions but this solution works poorly for wide stage widths, especially when one wishes to fill the whole stereo stage."
The "narrow stage width" that Gerzon describes is consistent with what I quoted from Holman in my previous post.
In the next paragraph, he wrote: "We have discovered some remarkably effective linear 2- channel 3-speaker decoding matrices capable of improved image stability for non-central listeners and improved image sharpness for central listeners, as compared to ordinary 2-speaker reproduction, and to prior proposals, eg the Bell/Klipsch 'bridged centre channel' method, for 3-speaker reproduction of two channels."
Because the sentence is a little complicated, let me insert some ellipses to make it easier to parse: "We have discovered some remarkably effective linear 2-channel 3-speaker decording matrices capable of improved image stability...and improved image sharpness...compared to...prior proposals, eg the Bell/Klipsch 'bridged center channel' method."
Furthermore, later he wrote "Two-channel stereo material, such as from sound effects recordings, library music, stereo microphones or commercial music recordings, can be mixed into a 3- channel programme either by restricting it (by means of 3-channel panpots) to a small part of the stereo stage, or by using suitable 2×3 matrix decoders as described earlier. The latter option does tend to give less good image quality than true 3-channel material, and has the problem that it must be made compatible with 3-channel decoding from the 3-channel mixed programme."
Gerzon was indeed prescient on many issues. Funny thing, what he said was clear enough, but golly, pumping a combined L+R signal into the center channel speaker is definitely NOT the best thing when aiming for center-enhanced stereo, at least if "improved image stability" and "improved image sharpness" and "wide stage widths" are desirable.
In the next part, he says, "In either case, the [dual center channel] speakers must be provided with psychoacoustically optimised feeds adapted to the specific layout in use in order to get an optimised image illusion. Naively-chosen speaker feeds will not work well."
I dare not ask how the dual channel feeds were "psychoacoustically optimised." Using the same signal to drive both center channels with identical signal would be to choose "naively."
Not related to Bentoronto's jaunty misrepresentations of Gerzon's and Toole's ideas, a diametrically opposite approach to Moulton's setup would be Airsound: airSOUND Technical Description
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Say, "jaunty misrepresentations"... pretty strong language there. On the other hand, what would be nice way for me to say you are "selective" in what you choose to quote to serve your own purposes, which I am not too clear about.
Gerzon says about the Bell/Klipsch method, "but it does seem to offer a good second-best option to true 3-channel stereo." Didn't think you needed to quote it in your long flame?
We shouldn't forget that whatever it is that youngho is advocating and which might be the first-best option of the ultra-engineer Gerzon, is something nobody makes and/or you can't afford. Not a really good option for most people, I'd say.
About taking me to task for advocating dual center speakers flanking a big screen, I am not sure what profound shortcoming youngho has found. He seems to be saying, "be sure not to have 35 dB noise protectors in your ears while setting up." I agree completely and really sorry I didn't emphasize this very important point in boldface type in my very brief and jaunty post.
Frankly, any day of the week, I'd rather be accused of being "jaunty" than being "selective" with my evidence.
Yes, in theory there just possibly might be better if exceedingly complex systems (that few people have ever heard let alone evaluated) that will create a better signal to the center channel than the simple resistor mixer that Paul Klipsch recommended.
Gerzon says about the Bell/Klipsch method, "but it does seem to offer a good second-best option to true 3-channel stereo." Didn't think you needed to quote it in your long flame?
We shouldn't forget that whatever it is that youngho is advocating and which might be the first-best option of the ultra-engineer Gerzon, is something nobody makes and/or you can't afford. Not a really good option for most people, I'd say.
About taking me to task for advocating dual center speakers flanking a big screen, I am not sure what profound shortcoming youngho has found. He seems to be saying, "be sure not to have 35 dB noise protectors in your ears while setting up." I agree completely and really sorry I didn't emphasize this very important point in boldface type in my very brief and jaunty post.
Frankly, any day of the week, I'd rather be accused of being "jaunty" than being "selective" with my evidence.
Yes, in theory there just possibly might be better if exceedingly complex systems (that few people have ever heard let alone evaluated) that will create a better signal to the center channel than the simple resistor mixer that Paul Klipsch recommended.
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Thanks for including that, but again you left off the complete sentence: "We hope to be able to publish both the theory and methods of such 3-speaker decoding of two channels in the near future but it does seem to offer a good second-best option to true 3-channel stereo."
"It" here does NOT refer to the Bell/Klipsch method, but rather the "remarkably effective linear 2-channel 3-speaker decoding matrices" that Gerzon discovered. Pronoun troubles, jaunty misrepresentation, or being overly "selective"?
Right, because upcoding algorithms more sophisticated than L+R are not available for a very affordable cost, like those from Harman, Audyssey, Dolby, Neural (for compressed audio), etc.
In my first post in this thread, I wrote: "Incidentally, Holman also has a few paragraphs [in his book "Surround Sound"] on the problems associated with dual center channel speakers." Here is the complete reference: "Surround Sound Up and Running" by Tomlinson Holman.
You may get a sense of what Toole might say about dual centers from reading the section in his book on simple MTM center channel speakers. If there is more than one row of listeners with vertically spaced dual centers, or if the single row is not on-axis, then the problems will quickly become apparent as one moves even slightly off-axis, and the reflections off the floor and ceiling will be dissimilar in terms of spectral content to the original, which is undesirable. In the case of horizontally spaced dual centers, a similar problem will arise in the lateral plane.
Toole distinguishes between comb filter effects induced by reflections (preferably of similar spectral content to the original signal) and acoustical interference from multiple sources (as in stereo, also MTM center channel speakers).
Also, I think Dantheman referred to a section on setting the center channel speaker higher than the left and right. This was in reference to speech intelligibility where the left and right were playing extraneous noise, and the benefits were less significant in listeners were normal hearing. Look at the fourth complete paragraph on page 164 for reasons to set the front three levels similarly.
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The airSound article is interesting, I've seen this before in other places but never heard one of these units. I think it merits further exploration, in a way it places the emphasis on the centre channel too.
Anybody heard one of these ?
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