Note: Posts collected from "Beyond the Ariel" thread (I hope this is OK for everybody).
I hope we can start a serious, fruitful but relaxed(!) discussion, maybe even users (if there are any reading this forum) of the MilesTech ("Multisonic Imager") or Bongiorno ("Trinaural") devices can give some input.
- Klaus
Originally posted by dobias
Gentlemen,
I don't recall seeing center speakers discussed in this (lengthly) thread.
I would like to spread out my OB speakers for furniture placement reasons. What are the pros & cons about using a center OB speaker?
If it is a reasonable addition, I remember(from my younger years)there were various ways to wire it, all with different disadvantages. Any wiring suggestions?
dobias
Originally posted by KSTR
Regarding driving of a three speaker setup which still is "normal stereo" in the preceived sound (actually it is usually quite better -- gives a more convincing illusion -- than 2-speaker-stereo), you might want to try what is known as "optimum linear matrix" and, in a more specific form, "trinaural". Properly set up, there are no**) disadvantages except that you need some time to get accustomed to the new and somewhat different soundfield represention -- kind of similar to effect of boomy bass one has gotten so used to until the first OB speaker was heard... now one knows what "boomy" really means, and after hearing OLM you will know what "scattered" means...
See Us.Pat.#5610986 (via http://pat2pdf.org), and the following websites:
http://www.milestech.com
http://www.ampzilla2000.com/trinaural.html
You need an additional line level hardware and three amplifiers. A purely passive approach at speaker signal levels using xformers might be possible, but will be quite hard to construct it as a really good working solution.
I don't know if there are any drawbacks from using OB speakers, but maybe there are -- at least there are asymmtrical (in time) reflections because the distance to front/rear wall is not the same for all three speakers.
EDIT: **) there are some disadvantages with recording tricks (HTRF based phantom localization way beyond the speaker baseline, laterally and, to a lesser extent, vertically) that rely on the use of the conventional stereo triangle, for example "Q-Sound"
- Klaus
Originally posted by dobias
Klaus,
Thank you very much for the information. As luck would have it, Mike Miles has his business a few hundred miles away here in Michigan.
I'll be in contact with him to work out the most inexpensive setup for me. I would like to have it work with my stereo amp but I'm willing to add an amp to have it work well.
It may be awhile before I can work it out but I'll let you know how it worked.
Do you have such an arrangement?
Frank
Originally posted by KSTR
Hi Frank,
Not in an actual simple working condition (ahem, the 3rd identical speaker that is needed). But I have tested it thoroughly (I also tested/measured one of the hardware devices available), working up on the theory (which has some roots way back in time, see the papers of A.D.Blumlein, and, more recently, M.Gerzon) and investigating many possible arrangements with a DAW-Software (digital audio workstation) and a multiple output soundcard (I have 24 channels, no lack of channels therefore ;-). The hardest part was, because of not having three identical speakers, trying to make them "equal" (small active monitors and a conventional passive floorstander) by use of allpass filters to correct for the different xovers and of course some EQing to get at least first order aproximations of identical responses. While severly compromised by the dissimilar speakers, these tests were nevertheless extremly promising, and quite a few people have tested "the real thing" with the processor (J.B.'s) and 3 identical full-ranging speakers (which really is very important, the typical home-cinema center is often not sufficent). Not everyone would find himself satisfied with the difference in the stereo representation, but those who did will most certainly never switch back. The stable soundstaging even with considerable head movement/turn and the overall increase in "spatial resolution" by a percieved order of magnitude is really stunning (@naysayers, this is not marketing bla-bla, I have no relationship with any company or any other interest other than to promote all this because im really convinced of it, in theory and in practise. It's a just another way of projecting stereo information into the room, another reproduction paradigm).
Currently, I'm saving money for a bigger overall system upgrade and might meanwhile try some cheap single-driver OB's in that setup to test if there is any conflict -- as I'm a true fan of open baffle speakers I can only hope there isn't, no tradeoff to be considered then...
Originally posted by Lynn Olson
Not a bad a idea to start a thread on high-quality 3-speaker stereo. I read Patent #5610986 carefully, and was dismayed to see no definition of the matrix itself, which is a crucial part of the invention. I hold three patents myself, and I know the patent office frowns on partial disclosure - trade secrets and patents are two different ways of protecting intellectual property, and are not to be commingled. I'm not a patent attorney, but that's what they told me. I was told to choose one of three methods: public disclosure in a magazine (creating prior art, thus precluding other patents), trade secrecy with rigorous NDAs for all concerned, and patenting - and not to mix them up.
The lack of disclosure of the 2 -> 3 matrix (which I noted was a static, not dynamic, matrix) makes it hard to tell from a straightforward Gerzon 2 -> 3 system, which dates back to the late Seventies. The Gerzon patents have all expired (along with my own, see #4018992), making them fully-disclosed prior art. I regret to say I do not see full disclosure in #5610986, which seems to invalidate the whole concept of patenting - there should be enough information in the patent so the device can be re-created by one "skilled in the art". Well, I see no mathematical coefficients, just vague descriptions of sum-and-difference networks - which are part of every matrix decoder without exception.
Actually, there's a fair amount of controversy of the correct way to derive the center channel, depending on the goals of the playback system. If the goal is to reduce the amount of comb-filter coloration of centered soloists (which is quite noticeable compared to monophonic single-speaker playback), it doesn't take much level to accomplish this - a phase and dispersion-matched Center speaker 12 dB down will do the job. If a smooth, equal-energy soundstage is desired, then more Center signal is required - but raising the level of the Center speaker also degrades the resolution of far-left or far-right signals due to crosstalk (the center signal is still present, and only a few dB down, when a L-only or R-only signal is on the recording).
This crosstalk is always there with any static matrix - which is why dynamic matrix systems were and are used for Sansui QS Vario-Matrix, Shadow Vector SQ, CBS Paramatrix SQ, Dolby Pro-Logic I, and Dolby Pro-Logic II. Once you go to dynamic playback matrices, of course, then the whole issue of image-shifting and maintaining constant reverberation energy raises its head - not to mention suitably-chosen attack and decay time constants for dynamic matrix (typically 1~3 mSec attack and 20~50 mSec decay).
Going back to static-matrix systems - which probably have the least coloration and odd-sounding dynamic artifacts - the requirement for phase, amplitude, FR, and dispersion-matching for every loudspeaker become quite severe, since there is never very much signal separation with any kind of input signal. With only 3~6 dB of separation between any pair of speakers - at the very most - then small differences between speakers become very important. Of course, even with full-discrete signals, it's still important, but only for the phantom images (and the reverberant content).
Originally posted by KSTR
Hi Lynn,
Um, I'm a bit bewildered from your comments to be honest. I for one had no difficulty to find the required matrix formulae in the patent, albeit they are not written in classic matrix form. It's all right on the front page:
Lout = Lin - m*Rin
Rout = Rin - m*Lin
Cout = (1-m)*(Lin+Rin)
In the more general form one replaces (1-m) with another factor n and then we have all degrees of freedom in useful 2-to-3 linear revectorizing (as it is put sometimes). With these two factor I played a lot, and found, confirming the results of Mr.Miles and Mr.Bongiorno, that both factors at ~0.5 gives the best results (and, btw before I learned about the Miles patent). I also have two working circuits and some ideas for "high-end" circuit variations.
I hope we can start a serious, fruitful but relaxed(!) discussion, maybe even users (if there are any reading this forum) of the MilesTech ("Multisonic Imager") or Bongiorno ("Trinaural") devices can give some input.
- Klaus