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Trinaural decoding equations for 3 speaker stereo matrix ?
Trinaural decoding equations for 3 speaker stereo matrix ?
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Old 25th July 2013, 09:00 AM   #161
Elias is offline Elias  Finland
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So, are we going to have some measurement results soon ?
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Old 25th July 2013, 05:39 PM   #162
ro9397 is offline ro9397  United States
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Originally Posted by Elias View Post
So, are we going to have some measurement results soon ?
Well...my friend George and I both own Trinaural. I use my system daily, while George awaits home remodel and new speakers coming before I assemble his system.

Sorry, no scope etc, here.

I've not read read the entire thread, but plan to. I would consider supplying a Trinaural for testing. I'd have to insure EJ @ W4S has replacements available and frankly I could not afford the risk of loss so someone would have to prepay fully refundable deposit equal to my replacement cost (wholesale dealer cost, $2500 msrp last checked a few months ago).

What is the consensus desire for members to replicate Trinaural? Opamps, passive transformers...?

I love the idea of DIY Trinaural but relevant questions arise. What is estimated parts cost for the basic functionality, L/R input, LCR output?

I presume each member desires a different mix of Trinaural's OEM features. IMO at least one non-OEM feature seems critical, a Stereo/Trinaural switch with unity gain (IOW overall system output stays constant when switching between Stereo and Trinaural).

OEM features:

3.1 HT bypass
Balanced outputs
Unbalanced inputs
Noise rotary volume/off switch
Center channel level screw adjustment
Noise generator to balance Center level
Noise routes to LCR via 3-position toggle
LCR toggle switch: Fullrange/active HP crossover
Subwoofer rotary level, significant output @ minimum setting
HP/LP active crossover in-phase 2nd order @ 80 Hz, LP always on

I agree with Kal Rubinson, who does not understand James' strong recommendation against comparing stereo to Trinaural. I disagree with James' warning that it takes a week or two to adjust to Trinaural. Finally, I disagree with James who says leave the C Ch level alone once it is set: I enjoy a remote multi channel line preamp with remote trim of C Ch and Bass level.

A glaring, egregious Trinaural fault is no switch to compare Stereo/Trinaural, preferably with unity system gain between the two.

I tend to agree with Jim Smith on two criticisms, though I solved both to my satisfaction:

As mentioned earlier, C Ch quality seems slightly different and less pure vs. LR. I solved this by raising my C Ch speaker 4cm and no other change (highly refined Dynaudio Esotec 2-way MT above 80 Hz).

Smith suggested that Trinaural processing for spaced omni recordings ala Telarc (RIP) is just wrong. Independently before I read Smith's opinion, my practice was greater attenuation of C Ch level playing Telarc and other spaced omni recordings. The following is also interesting, and goes directly to Smith's criticism: with proper C Ch level (about -4dB on my preamp, system is unity gain LCR including Trinaural C Ch trim pot) Trinaural still blows away Stereo. So Smith was right, but wrong after solution applied.

I very much thank Smith for the above criticisms, which clarified problems and their solutions. OTOH, I personally found his remaining criticisms laughable coming from someone who charges several thousand dollars for home stereo setup and who used to import $100k speakers: Trinaural requires more space (yeah, and those Tannoys you love and your old horns are small?), requires more cost, requires another channel of amplification, etc, etc. Every one of those criticisms apply across the audio board to every single advancement except the extra channel.

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Last edited by ro9397; 25th July 2013 at 06:07 PM.
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Old 25th July 2013, 06:04 PM   #163
ro9397 is offline ro9397  United States
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Originally Posted by Elias View Post
So, are we going to have some measurement results soon ?
Your website has a great wealth of information and data, even on 3-ch matrix.

Have you built a decoder yet based on your new so-called ideal matrix? How fun would it be to compare to Trinaural!

I'm awful with math while you are obviously quite adept with it. Have you translated the Austrian Trinaural DIY site, and if so: did they post the Trinaural equations? How do they compare to your own ideal matrix?

Very glad to find this thread, and especially your contribution. As mentioned earlier, I've had no interest in stereo for almost seven years now.

If only James was alive. 'Twould be so much fun to show him your math and get his cantankerous replies, expletives and all!

I remember at one CES James insulting a Merdian engineer for their outdated test gear! I quickly slithered away....at least he made up for his outrageous personality with understated clothing...NOT!
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Old 25th July 2013, 07:01 PM   #164
Elias is offline Elias  Finland
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Originally Posted by ro9397 View Post
What is the consensus desire for members to replicate Trinaural? Opamps, passive transformers...?

I love the idea of DIY Trinaural but relevant questions arise. What is estimated parts cost for the basic functionality, L/R input, LCR output?

Now, until further confirmation about Trinaural equations are revealed, we must rely on what was available from other Diyaudio members. The decoding matrix coefficients were given earlier in this thread as

Ls = L - 0.5 R
Cs = 0.5(L + R)
Rs = R - 0.5 L

Parts cost ? How much a wire costs ?
(Of course you'll need three speakers, but that cost does not count, even if it's 50% more expensive than 2 speaker stereo).

This is what I've been using. It fulfills the above matrix coefficients.

Click the image to open in full size.



Quote:
Originally Posted by ro9397 View Post
If you want free easy solutions to improve performance stop visiting here!
I think quite the contrary This is the place to visit for easy solutions to improve stereo performance
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Old 25th July 2013, 07:21 PM   #165
ro9397 is offline ro9397  United States
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Jim Smith made one other criticism, that Trinaural setup diagram alters LCR spectral balance: C Ch speaker is on-axis, LR cross-fire 12" IFO centered listener. It's possible this did not occur to the inventor, he ignored it in the design, and employed no compensation in the design. The opposite is also possible, that this spectral change occurred to the designer and he employed some compensation in the design.

Possibly the qualitative difference I noticed and mentioned earlier (LR more highly refined sound vs. C) might be related to the above. Possibly slightly more toe-in than recommended would solve the problem (my solution was to elevate the C Ch 4cm).
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Old 25th July 2013, 07:31 PM   #166
ro9397 is offline ro9397  United States
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Sorry I'm not yet up to speed. Is your matrix line level or speaker level? Diagram appears to be speaker level, but I just have no idea, sorry!

I can ask my friend who builds countless amps and DAC to test Trinaural. Maybe you could PM or email me specific questions for him to answer.

I'll finish reading and get up to speed to not waste member's time.
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Old 25th July 2013, 07:46 PM   #167
ro9397 is offline ro9397  United States
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Originally Posted by bzfcocon View Post
...Are there actually 3-speakers solutions that do NOT assume that the center speaker is identical to L and R ? The approach sounds promising and I would like to test it, but not if it means another bulky loudspeaker in the middle. How about if the center would only reproduce >100Hz, would the concept still work and would it change the matrixing ?

Interesting thread, btw.
For me the only two bass reproduction systems in domestic space (below 80 Hz) are Distributed Array (four subs) and Double Bass Array. I employ the former. The latter costs at least twice as much and ideally requires subs installed semi-permanent in-wall.

This works perfectly with Trinaural, requiring the main LCR speakers cover only above 80 Hz, hence they do not need to be large full range floor standers.

Trinaural instructions allow C Ch speaker to be different from LR but if so C Ch must be better in quality not worse compared to LR. My experience validates the above claim. When I tried it the speakers employed same drivers but different quantity mid bass and planar mids.
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Old 25th July 2013, 09:29 PM   #168
ro9397 is offline ro9397  United States
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I'll confirm later, but meanwhile: is it likely that speaker grounds are common on my 2003-2004 vintage Pioneer VSX-D912 HT receiver, with pure analog chip power amplifier output stage? (Earl Geddes' preferred amp once upon a time...superb into the correct load). Can I confirm by simply turning off power and checking continuity with Ohmmeter?

As soon as I confirm I'll happily compare performance with Elias' circuit vs. Trinaural. I promise to have an open mind. My speakers full range cutoff in the mid 40s.
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Last edited by ro9397; 25th July 2013 at 09:36 PM.
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Old 26th July 2013, 12:48 AM   #169
Lynn Olson is offline Lynn Olson  United States
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I should mention in passing the comb-filter coloration that appears in 2-speaker playback with centered sources can be alleviated with quite low Center levels, possibly as low as:

Center = Left 0.223 + Right 0.223, which is 10 dB lower than the usual pan-pot level of Center = Left 0.707 + Right 0.707 (assuming Left = 1.0 and Right = 1.0)

If the primary aim of the Center speaker is to reduce coloration on vocals, as opposed to greater image stability, the optimum Center level may indeed be lower than the usual recommendations.

What I am not sure of is the effect of Center level on image depth; this is where three symmetrical loudspeakers with identical diffraction signatures and crossovers may be necessary for image stability and reduced listening fatigue. (The one sure sign of incorrect multichannel setup is more listening fatigue than straight 2-speaker stereo.)

If the depth begins to suffer, that may be a sign that the Center level is too high for that particular recording ... annoyingly, with modern recordings sourced from studios all around the world, it might be necessary to adjust Center levels on a track-by-track basis.

In practice, both user adjustable Center level and moderate degree of Center-channel EQ may desirable (preferably on a remote). For example, a slight degree of HF rolloff starting at 5~8 kHz might be necessary to subjectively timbre-match the Left and Right speakers; even though all speakers might measure identically, remember that your ears have a different spectral response for sounds arriving directly in front versus phantom images created from speakers that are 20 to 30 degrees off-center. What you need is a subjective tonal match, preferably made with a pink-noise source, for all L, C, and R image locations, and all intermediate locations in between.

Last edited by Lynn Olson; 26th July 2013 at 01:02 AM.
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Old 26th July 2013, 01:10 AM   #170
ro9397 is offline ro9397  United States
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Quote:
Originally Posted by Lynn Olson View Post
I should mention in passing the comb-filter coloration that appears in 2-speaker playback with centered sources can be alleviated with quite low Center levels, possibly as low as:

Center = Left 0.223 + Right 0.223, which is 10 dB lower than the usual pan-pot level of Center = Left 0.707 + Right 0.707

If the primary aim of the Center speaker is to reduce coloration on vocals, as opposed to greater image stability, the optimum Center level may indeed be lower than the usual recommendations.

What I am not sure of is the effect of Center level on image depth; this is where three symmetrical loudspeakers with identical diffraction signatures and crossovers may be necessary for image stability and low listening fatigue.

If the depth begins to suffer, that may be a sign that the Center level is too high for that particular recording ... annoyingly, with modern recordings sourced from studios all around the world, it might be necessary to adjust Center levels on a track-by-track basis.
As dedicated Trinaural devotee for 6+ years, I agree with the last sentence. Strangely, the inventor specifically instructs users to never alter C Ch level once it is "properly" set.

I remotely trim C Ch and Bass level (below 80 Hz, Distributed Array with proprietary setup instructions available for public use), and presume such trimming really must be done with a remote for efficiency and convenience. I feel quite sure the dearth of affordable transparent remote 3-ch (or more) line preamps contributed to low Trinaural acceptance. The inventor's instructions (above) and also the lack of Stereo/Trinaural A-B switch also contributed.

I think it noble of Kalman Rubinson to recently recommend Trinaural to stereo devotees at AA.

Sorry to repeat, but my center image and spatial effects, even in stereo, are so good that every time I switch off the Trinaural and toss a blanket over the C Ch speaker, I still have to physically walk up to the C Ch speaker to confirm it is off. Listeners would likely qualify performance as exemplary in that specific area.

But still, switching back to Trinaural instantly shames the stereo format. Compared in this way, the label "phantom" most definitely applies to C Ch image and spatial effects in stereo.
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Last edited by ro9397; 26th July 2013 at 01:16 AM.
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