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Can someone help me with this?I am doing some research on 3 channel stereo. I have read several times in the past that stereo reproduction was experimented on three channels very early on (before 1950, if I remember correctly), but that two-channel stereo was implemented for practical reasons.
Is there a starting point (web site, book, etc) to understand better the issues involved, any actual experiments conducted, published, etc?
The purpose is to experiment three high resolution (24/96kHz)channel versions of some stereo recordings (left, center, right), and make some comparisons with the same recordings at the same sample rates.
Any thoughts about channel allocation and phase issues?
Any help will be much appreciated.
I'll send my results to whoever is interested.Best
Eric
PS: Obviously, this is for a DVD-Audio project. I also posted this message on the Propeller Head forum, so this is the same message.
Follow Ups:
as the center will be a mismatch for 95% of the systems out there (mine included, of course). The center channel is a pet peeve of mind as it is not practical for me to put a speaker identical to and in between the mains, placed exactly where the TV would be. At least the recording folks ought to think about redirecting significant bass information away from the center given the wimpish centers most people are using. And no, I do not want to do BM for hi-rez).This would only work if I had separate HT and 5-channel hi-rez music rooms. This won't work for my pocketbook.
Research seems to support 3C as being better then 2C. One of the original tests was performed by W.B Snow (Bell Laboratories) in 1933. The goal was to reproduce a live concert for an audience 141 miles away. After much experimentation, it was determined that 3C was 'satisfactory'. Snow had thought that a 'curtain' of mics/speakers (1:1) would be optimum. The LP later undid 3C stereo by bring 2C stereo to the masses. So today when we think of stereo as being 2C, it is really just decades of exposure to 2C stereo.Now you bring up the point of the center channel being a problem due to the placement of the tv. This is true but the tv between your L/R speakers is causing problems with the stereo image anyway so it is difficult to have your cake and eat it too. One of my more significant upgrades for sound was to ditch the tv from between the speakers. Flat panel TVs are becomming a little less expensive and the cost will continue to drop - not yet a cost effective solution.
As this is a DVD-A forum, I will add that having excellent DVD-A recordings that place most of the information in the front 3C will bring us closer to an ideal. The 2C mix (preferably not mix-down) will provide backwards compatibility for those that need or prefer it.
than information going to a center channel. I have heard that 3C might be better than 2C but I have not heard this for myself. I agree that TV may be screwing up the soundstage, even though my TV is recessed 3 feet behind the speakers. I'm thinking about large flat panel TV but I've the impression reliability issues could be significant since I tend to have ESPN and CNN on all the time.BTW, doesn't that center speaker also screw up your stereo soundstage ?
No arguement on the rears containing ambient information. I'm just not a fan of the "sitting with the band" mixes. I guess the ideal would be for a third mix (such as AIX provides) so everyone could be happy.My left & right speakers are about 7' apart. All three front speakers are 10.3" wide x 13.8" deep. Compare this to a box 34" wide x 24" deep and you can see the tv was much more of an problem for me. Your set up with the tv recessed 3' the problem may be much less.
What I have done is place my screen higher then the speakers. This allows my center to be where it should be at the same height as the main speakers. It has only been a couple of days that I have had the center of the same type as the main speakers and the difference is not subtle. I'm still working on placement but so far the center is a couple of inches back of the main speakers.
Don't worry, I doubt it will have any impact on the music industry :)I am using small (cheap) identical speakers, so it's easier for me.
However, you raised an interesting point, which is the allocation / reallocation of bass information.
I hadn't thought about that...Best
I have done a little scanning of material of this type in the past. I do remember an artical where it was demonstrated that 3C was better then 2C for stereo reproduction. I believe Meridian has taken that idea in their Trifield processing which converts 2C into 3C. Many people enjoy Trifield but it seems critical that the three delivery channels are of the same quality.http://www.meridian-audio.com/lib_pap.htm
Ambisonic may provide you with information too. The recording process is different but "Super Stereo" fakes Ambisonic from 2C material.
http://personal.riverusers.com/~manderso/
I use a Meridian processor and have been attempting to get to the point where Trifield would work for me. I'm close now but still have a mismatch on the center channel (amp). The effect of Trifield is a more spacous sound with a larger sweet spot. As I do not enjoy 'center of the band' DVD-A MC using Trifield from the 2C track on hi-res should give me the best of both.
I'll post the results + the experiments here.
Maybe you will want to compare the Meridian Trifield against 3 discrete channels (on DVD-A), I'll let you know if it works.Thanks again
Best
to play back a good DVD-A MC mix where the front 3C carries the majority of the information compared to the same DVD-A 2C mix using Trifield. The 2C is higher res but the MC doesn't have the extra processing. I cannot, as of yet, as my 568 has not yet been upgraded to the 568.2 where I can accept MC.It will be interesting to hear how your experiment goes.
Rod.
It is possible to test the 2C stereo version at different resolutions on DVD-A... unless the Meridian digitizes / upsamples everything?I'll post my progress.
There was an interesting response on the Propeller Head Plaza already.
The original concept dates back to 1930Best
Eric
Meridian equipment leaves everything in the digital domain as long as possible. Even the analog inputs have a ADC so that all processing is done in the digital domain (Vinal purists shudder here) Output can be via the DAC for analog (my setup) or digital for speakers with their own DAC such as Meridians.
I can control when upsampling is applied.
We could write a letter to Meridian explaining that this is an experiment to compare TriField against true 3CH stereo, how it would be conducted, and that you need a MCH setup for the experiment. They will be interested, I'm sure, and they have probably done it a thousand times themselves.I think you'd have to send the equipment back after a while, though...
Best
The current 800 conveys all info (including MCH DVD-A) to the current 861 in digital form. Therefore, comparisons between derived 3 channel (trifield), 3-out-of-5.1 channels and high-rez 2 channel do not require any additional conversions, only different processing in the 861. I have not (yet) done such a directed comparison but I have found, in casual comparisons, that trifield is often preferred to stereo.
If anyone knows of a DVD-A with both MCH and 2CH where the MCH mix uses only the front 3CH this test would be easy to perform (Okay, so I'll have to convince Meridian into upgrading my processor purely for the sake of science ;-). My bet is be on the MCH... I'll post this on a Meridian user forum to see if anyone is interested in running the test.Clarification: the current 500 series also conveys digital information between devices. The 'analog input' comment was to point out that Meridian processes everything in the digital domain therfore requiring ADC on analog input.
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