3 Speakers For Stereo Content?

[Kal Rubinson]

More on topic, would Dirac be able to calibrate a 3 speaker stereo system? Kind of a Dirac noob still.

Should not be a problem.

 

[DVDdoug]

The simple "matrix" method of L+R = Center means left-only and right-only signals are also sent to the center speaker (attenuated). And of the "center" audio still goes to the left & right speakers. It's not "correct" but it's simple, clean, and predictable.

The old ProLogic 'movie mode steering" does unpredictable things with regular stereo. More advanced DSP methods are likely to also be unpredictable.

 

[SadMonster]

The simple "matrix" method of L+R = Center means left-only and right-only signals are also sent to the center speaker (attenuated). And of the "center" audio still goes to the left & right speakers. It's not "correct" but it's simple, clean, and predictable.

The old ProLogic 'movie mode steering" does unpredictable things with regular stereo. More advanced DSP methods are likely to also be unpredictable.

This makes sense to me but I feel like it would mess with a lot of stereo effects. Maybe it’s best we just live with the 2 channels…

 

[KSTR]

My understanding was RME ADI-2 DAC had only two independent channels, how would the C be assigned then? Please excuse my dumb questions.

There are no dumb questions ;-)
The trick is that
L' + R' = (L - R/2) + (R - L/2) = (L+R)/2 = C
And the L' and R' can be generated by setting the stereo width to a certain level, for stereo width > 1 (again, I'll have to look that up for the RME)

That is, you can get the center channel by mixing the L' and R' output passively (with something like ~3kOhm resistors) and the only need a factor of two applied to it as mixing only gives the average (L' + R')/2 = C/2. Often, you want to trim the center level anyway.
One could also just dim down the L' and R' to 0.5x channel to obtain the same balancing of levels. This is actually somewhat preferable as then the impedances match (thus the gains will, regardless of input impedance) and the gain for the power amps is the same, easy to use with an AVR.

The passive resistor-based solution therefore looks like this, using 6 pcs. 3.3kOhms resistors:
- Voltage divider 1:2 for the L' and R' output from the DAC.
- 1:1 Mixer for C, using the L' and R' output, before the voltage divider.
- Set up the L' and R' generation digitally, using said plugin (remember to apply the /1.5 scale factor to avoid any chance of clipping), or use a stereo width control if the DAC has one.

The test if the matrix is correct is simple. Create a test signal where the right signal is the copy of the right signal, but half the level (50%, 6.02..dB -- 6.0dB is NOT correct here). Then the output from R' channel must be zero, and the output from the C and L' channel is the same, 3L/4.

A signifigant property is that for trinaural all three speakers alway produce sound execpt for the rare cases when R = L/2 and vice versa, that is, signal panned exactly half-way to the side.

 

[ob1]

@KSTR, I am very grateful for your detailed answer and for your excellent contribution, in general, to ASR. If ever you have any other information pertaining to this subject, I am thoroughly interested. Many thanks again!

 

[mhardy6647]

You might want to do a search for "Dynaco Derived Center Channel". It's primitive, but it's cheap. I like it. Some people don't. Jim

FWIW -- the only "Dynaco" processing trick I know of was Hafler's "derived rear channel" (using out of phase signals), which has been discussed elsewhere on these august fora.
Mind you, I am not sayin' that you're not correct, but I am skeptical (I get like that). I will do a search anon, but gotta run now.

FWIW^2: Paul Klipsch used to recommend a "mixed to mono" derived center channel to fill in the hole left in the middle by a pair of K-horns in a large room That's what Cornwalls (and Heresys) were for, from his point of view! "Center speaker" outputs werent' all that uncommon on consumer hifi products of the early stereo era, in fact (HH Scott and EICO, e.g., had models with built-in schemes to feed mono to a

 

[DonH56]

Dynaco (Hafler) stereo circuit: https://patents.google.com/patent/US3417203A/en

Paul Klipsch said he designed the Heresy as a center-channel speaker. He and a number of others felt three channels were needed for hi-fi listening but ultimately the world used only two.

 

[KSTR]

@KSTR, I am very grateful for your detailed answer and for your excellent contribution, in general, to ASR. If ever you have any other information pertaining to this subject, I am thoroughly interested. Many thanks again!

I feel very honored, thank you.
Atm I'm not running trinaural at home, actually I don't have even have a speaker setup, for pandemic-related home-office space issues, so I'm on headphones only. But that will change hopefully soon...

 

[SadMonster]

So I just realized that I think I can just add a 3rd powered speaker to my setup by having my MiniDSP DDRC24 output both the left and right channel to a 3rd output on the MiniDSP at the same time for a physical center channel.

Still, there‘s no way to get the positioning for it decent because the TV is blocking where the 3rd speaker should be. Also no space for a third subwoofer to passthrough to the speaker to make it full range. Maybe one day I’ll get a bigger place to live and I’ll be able to set something cool up!

My TV actually has an option to output to Optical while playing on the built in TV speakers still so I kind of have an option already for 3 channel stereo….

 

[abdo123]

A little off topic but the improvement in clarity from Dirac is so big that I imagine if your budget for a stereo is 1000 or less, you would be better off with half your budget going to Dirac and the other half going to cheaper speakers versus just getting 1000 dollar speakers which might be a little better than the 500 dollar speakers.

I think I would rank the improvement on par with 2 subwoofers instead of 1.

More on topic, would Dirac be able to calibrate a 3 speaker stereo system? Kind of a Dirac noob still.

if something else is generating the 3 inputs then yes, but I don’t think any Dirac enabled device can do the necessary calculations to generate the channels on its own.

I know a MiniDSP cannot.

 

[abdo123]

So I just realized that I think I can just add a 3rd powered speaker to my setup by having my MiniDSP DDRC24 output both the left and right channel to a 3rd output on the MiniDSP at the same time for a physical center channel.

Still, there‘s no way to get the positioning for it decent because the TV is blocking where the 3rd speaker should be. Also no space for a third subwoofer to passthrough to the speaker to make it full range. Maybe one day I’ll get a bigger place to live and I’ll be able to set something cool up!

My TV actually has an option to output to Optical while playing on the built in TV speakers still so I kind of have an option already for 3 channel stereo….

This is not a proper center, not even close.

it’s fun but it’s basically the same as having both optical and TV internal speakers working at the same time.

 

[SadMonster]

This is not a proper center, not even close.

it’s fun but it’s basically the same as having both optical and TV internal speakers working at the same time.

Do you think it’d be worth adding a powered and centered sound bar with both the left and right channels playing on it at the same time Dirac corrected? Or should I give up on the dream till I get a better place to live and stick with my nice stereo setup?

I feel like the ghetto physical center would be worse than my very nice stereo illusion center.

 

[abdo123]

Do you think it’d be worth adding a powered and centered sound bar with both the left and right channels playing on it at the same time Dirac corrected? Or should I give up on the dream till I get a better place to live and stick with my nice stereo setup?

I feel like the ghetto physical center would be worse than my very nice stereo illusion center.

i think you should get an AVR with dolby pro logic because the point of having a center channel is so people sitting anywhere in the room horizontally have a proper center.

nothing provided in this thread comes close to a proper up mixing algorithm.

 

[KSTR]

i think you should get an AVR with dolby pro logic because the point of having a center channel is so people sitting anywhere in the room horizontally have a proper center.

True for TV watching maybe, but for music playback?

 

[mhardy6647]

View attachment 132920

of course, this forum doesn't have the "embarrassed" emojum for me to use in reply, so this'll have to do.




Thanks for savin' me the googlage.

For the record, here're a couple of Col. Klipsch's recommended/suggested center channel "hacks"
http://assets.klipsch.com/files/Dope_740700_v14n4.pdf

klipsch%20doh%20line%20level%20mono by Mark Hardy, on Flickr



klipsch%20line%20level%20mono by Mark Hardy, on Flickr


EDIT: Here's a typical early 1960s "consumer" solution: this is the slightly unusual (abstruse) loudspeaker connection panel from the redoubtable EICO ST70.
https://community.klipsch.com/index.php?/topic/107945-eico-st-70-brain-fart-help-needed/

 

[dasdoing]

"true" 3 channel stereo will not work on a extract center channel basis. a signal inbetween the center and left speaker will be played by both of them for example.

something like this

CS=(L+R)-root of (L-R)*(L-R)
LS=L-R (while negative values are not allowed; are 0)
RS=R-L (while negative values are not allowed; are 0)

 

[KSTR]

"true" 3 channel stereo will not work on a extract center channel basis. a signal inbetween the center and left speaker will be played by both of them for example.

Trinaural is not a replacement for actual 3-channel content. It's a 3-speaker projection mechanism for 2-channel content, and IHMO a better one than standard stereo. And proper trifield is even better than trinaural.

 

[SadMonster]

Trinaural is not a replacement for actual 3-channel content. It's a 3-speaker projection mechanism for 2-channel content, and IHMO a better one than standard stereo. And proper trifield is even better than trinaural.

What do you think of my idea of getting a sound bar outputting combined left and right channel to act as my center for stereo content? I could put it above the TV

 

[KSTR]

something like this

CS=(L+R)-root of (L-R)*(L-R)
LS=L-R (while negative values are not allowed; are 0)
RS=R-L (while negative values are not allowed; are 0)

These equations refer on the time-domain stream, the actual voltages present? If so, they only produce gross nonlinear distortion!

 

[KSTR]

What do you think of my idea of getting a sound bar outputting combined left and right channel to act as my center for stereo content?

If it follows the matrixing rules layed out it may work, as far as working along trinaural procces is the goal.