Are three channels better than two for stereo reproduction?

[terryforsythe]

For both the Left and Right outputs, you need to enable both input 1 and input 2, then you need to use a Biquad filter to invert one of the input channels according to the miniDSP development team, as explained below:

For example, assume that input 1 is left channel input and input 2 is right channel input. Also assume output 1 is left channel output, output 2 is right channel output, output 3 is center channel output, and output 4 is subwoofer output.

For output 1, you will enable both input 1 and input 2, use a biquad to invert input 2, then use the gain settings to set the parameters. For example, if using EP optimal (see post # 57), you will set the gain for input 1 to 0.8333 and the gain for input 2 to 0.1667.

For output 2, again you will enable both input 1 and input 2, use a biquad to invert input 1, then again use the gain settings to set the parameters. For example, if using EP optimal, you will set the gain for input 1 to 0.1667 and the gain for input 2 to 0.8333.

For output 3, enable both input 1 and input 2, and set the each gain to 0.5720 if using EP optimal.

For output 4, enable both input 1 and input 2, and set the each gain to 1.

The above assumes all three speakers are equidistant from your listening position, e.g. arranged in a semi-circle. If they all are in the same plane, you will need to reduce the gains for output 3 and add time delay to compensate.

It looks like presently you use output 3 for a sub. You probably will need to run both subs from output 4, for example using an RCA splitter.

I also played with CamillaDSP to see how to implement it there. The mixer would like like the following:

It is showing "Config has errors" because my I/O module is configured for 2-channel output. I would need to reconfigure it for 4-channel if I were to implement this.

 

[LowShelfFilter]

For both the Left and Right outputs, you need to enable both input 1 and input 2, then you need to use a Biquad filter to invert one of the input channels according to the miniDSP development team, as explained below:

View attachment 382501

For example, assume that input 1 is left channel input and input 2 is right channel input. Also assume output 1 is left channel output, output 2 is right channel output, output 3 is center channel output, and output 4 is subwoofer output.

For output 1, you will enable both input 1 and input 2, use a biquad to invert input 2, then use the gain settings to set the parameters. For example, if using EP optimal (see post # 57), you will set the gain for input 1 to 0.8333 and the gain for input 2 to 0.1667.

For output 2, again you will enable both input 1 and input 2, use a biquad to invert input 1, then again use the gain settings to set the parameters. For example, if using EP optimal, you will set the gain for input 1 to 0.1667 and the gain for input 2 to 0.8333.

For output 3, enable both input 1 and input 2, and set the each gain to 0.5720 if using EP optimal.

For output 4, enable both input 1 and input 2, and set the each gain to 1.

I think there may be some confusion. I am not aware of a way to invert a specific input channel within the output channel settings. I believe this can only be done through the global input channel settings.

 

[terryforsythe]

I think there may be some confusion. I am not aware of a way to invert a specific input channel within the output channel settings. I believe this can only be done through the global input channel settings. Is there a way to specify an input channel to invert in an output channel biquad?

I haven't played around much with the biquads in my miniDSP, I just use the PEQs. You probably should reach out to miniDSP and ask them. I have reached out to them before and they were pretty responsive. I got an answer back in a day or two.

If there is not a way to invert the different input channels for the different output channels, then I stand corrected and the miniDSP units may not work for your purpose.

If that is the case, CamillaDSP probably is the way to go. I run it on a Raspberry Pi. It let me selectively invert the input channels using the green +/- icons on the right. See the screenshot in my post above.

 

[terryforsythe]

I think there may be some confusion. I am not aware of a way to invert a specific input channel within the output channel settings. I believe this can only be done through the global input channel settings.

Actually, you could use a miniDSP HTx. It has 8 analog inputs and 8 analog outputs. You could use RCA splitters to feed the left channel into inputs 1 and 2, and feed the right channel into inputs 3 and 4. Then you could use biquads on the global inputs to invert inputs 2 and 4.

 

[Holmz]

That reminds me that I need to find a 3 channel cartridge.

 

[rank]

Once accustomed to quadraphony, listeners found it difficult to return to two channels. Hence the success of home cinemas and other SACDs (unfortunately sold for far too much money). So...

 

[Hear Here]

More than one person noted that it sounded like the singer was actually standing in the middle of the room.

If you don't get that impression with a 2 speaker system, there is something wrong with the system. Speakers inappropriately chosen or poorly set up.

Not only should you hear the singer typically unambiguously dead centre (close your eyes and Norah Jones or whoever is sitting on your equipment rack singing just for you), but also the instrument closest to the singer will appear a little left or a little right with other instruments' positions equally identifiable. That's the impression good hi-fi should offer - that of being in the front row with live musicians at a number of positions at different angles.

 

[terryforsythe]

That reminds me that I need to find a 3 channel cartridge.

Or just read some science literature pertaining to audio, e.g., Floyd E. Toole, Sound Reproduction, 3rd ed., Section 7 (2018).

 

[LowShelfFilter]

Actually, you could use a miniDSP HTx. It has 8 analog inputs and 8 analog outputs. You could use RCA splitters to feed the left channel into inputs 1 and 2, and feed the right channel into inputs 3 and 4. Then you could use biquads on the global inputs to invert inputs 2 and 4.

Since I exclusively use toslink to send audio to my MiniDSP, and it would be convenient to do so with this device, couldn't I do something like this using dual TRS to XLR or dual RCA to XLR cables?

Left Speaker: Output 1 (Input 1) + Output 2 (Input 2) and flip polarity of output 2
Right Speaker: Output 3 (Input 1) + Output 4 (Input 2) and flip polarity of output 1
Center speaker: Output 5 (Input 1 + Input 2)

How would I extract the exclusively mono content and only have that play from the center though?

 

[terryforsythe]

Since I exclusively use toslink to send audio to my MiniDSP, and it would be convenient to do so with this device, couldn't I do something like this using dual TRS to XLR or dual RCA to XLR cables?

Left Speaker: Output 1 (Input 1) + Output 2 (Input 2) and flip polarity of output 2
Right Speaker: Output 3 (Input 1) + Output 4 (Input 2) and flip polarity of output 1
Center speaker: Output 5 (Input 1 + Input 2)

How would I extract the exclusively mono content and only have that play from the center though?

I'm not sure that would work well without an external op amp to do the signal combination and buffering. RCA shields are grounded. When you flip polarity of one channel and then connect it to the other you would create a short to ground.

If you want use a digital I/O I think CamillaDSP is the way to go.

 

[LowShelfFilter]

I'm not sure that would work well without an external op amp to do the signal combination and buffering. RCA shields are grounded. When you flip polarity of one channel and then connect it to the other you would create a short to ground.

If you want use a digital I/O I think CamillaDSP is the way to go.

I could probably get a cheap toslink DAC and split the outputs into the MiniDSP. The part I am not able to figure out though is how to make the center channel only play mono content, as in content that is present in both channels minus difference content.

 

[Holmz]

Or just read some science literature pertaining to audio, e.g., Floyd E. Toole, Sound Reproduction, 3rd ed., Section 7 (2018).

What music is mixed for 3 channel?
Does that mean I need a 3 channel amp etc.
An, lastly… I do not recall seeing many 3 cup headphones. (But there are probably cups for triorchids.)

 

[dlaloum]

What music is mixed for 3 channel?
Does that mean I need a 3 channel amp etc.
An, lastly… I do not recall seeing many 3 cup headphones. (But there are probably cups for triorchids.)

I know weird right.... you only have 2 ears and yet surround has 7 (or more) channels - maybe you need 7 cup headphones?

 

[Holmz]

I know weird right.... you only have 2 ears and yet surround has 7 (or more) channels - maybe you need 7 cup headphones?

Yeah but 7 channel mixing for HT is a thing.
Is 3 channel mixing a thing?

 

[JSmith]

JSmith

 

[Chrispy]

Yeah but 7 channel mixing for HT is a thing.
Is 3 channel mixing a thing?

Why would they mix for 3.1? They already do for 5.1 and 7.1 etc and you can generally limit that with your avr.

 

[dlaloum]

Yeah but 7 channel mixing for HT is a thing.
Is 3 channel mixing a thing?

Not needed - a good L / C / F setup, will appropriately decode the imaging from a traditional well recorded stereo 2 channel - resulting in excellent imaging and depth.

The objective is to provide a "window" on a sonic event, happening in front of the listeners (note the plural) - and the best recording methods of the 1930's to 1960's achieve that admirably, and can be assisted with a center channel (used appropriately!).

Later, more surrealistic mixes, make the entire imaging, and "window on the event" perspective moot... as they create an entirely artificial soundscape.... But given the artificiality of the product, there can be substantial debate about what constitutes high fidelity reproduction in such cases.

Stereo as originally intended, and for which there was substantial research in the early 20th century, is optimal with 3 (or more) front speakers.... and its objective is a "solid" 3 dimensional auditory representation of an even happening in front of the listeners, as if listening to a live even through a very large open window.
The 2 speaker approach can achieve this illusion admirably, but only for a very limited listening area (sweet spot), where additional speaker channels, with appropriate setup / processing, can maintain that illusion for a large listening area encompassing many listeners. No "head in a vice" effect.

 

[Robin L]

What music is mixed for 3 channel?
Does that mean I need a 3 channel amp etc.
An, lastly… I do not recall seeing many 3 cup headphones. (But there are probably cups for triorchids.)

When stereo first appeared in the late 1950s, classical recordings were mixed for three channels. As I pointed out in post #4 in this thread, RCA, Mercury and Everest made three-channel masters with the assumption that they would eventually appear in some three-channel format for the home. They did in the early 2000s as 3.0 SACDs.

 

[terryforsythe]

What music is mixed for 3 channel?
Does that mean I need a 3 channel amp etc.
An, lastly… I do not recall seeing many 3 cup headphones. (But there are probably cups for triorchids.)

Clearly you did not read the suggested literature. If you read it, as well as posts by @LowShelfFilter in this thread, you will gain understanding at why @LowShelfFilter is investigating the subject.

This forum is Audio Science Review. Science is both a body of knowledge and a process. To ignore a body of knowledge because it does not conform to one's own pre-conceived biases and to scoff the process of investigating that body of knowledge is anti-science.

 

[dlaloum]

What music is mixed for 3 channel?
Does that mean I need a 3 channel amp etc.
An, lastly… I do not recall seeing many 3 cup headphones. (But there are probably cups for triorchids.)

An extract from:

Alan Blumlein and the invention of Stereo - EMI Archive Trust

Alan Blumlein was a senior sound engineer at EMI’s Central Research Laboratories (CRL) on the Hayes factory site. He joined the company when Columbia and The Gramophone Company merged in 1931. Over his lifetime he was a prolific inventor, developing huge technological advances within the sound...

www.emiarchivetrust.org

"He started by abolishing the idea that two loudspeakers represented the listeners’ two ears and instead sought to re-create the features of the sound field including directional information."

So the first thing to consider, is we are trying to reconstruct a sound field...

The work of Snow, Fletcher and Steinberg at Bell Telephone Labs - was where the 3 channel stereo setup was developed as part of their research on recreating sound fields...

Here is another reference and an extract from:

https://acousticstoday.org/wp-content/uploads/2018/06/The-New-Age-of-Sound-Gabrielle-E.-O%E2%80%99Brien.pdf

The Grand Unveiling ofStereophonic Sound

On the evening of April 27, 1933, Harvey Fletcher welcomeda distinguished crowd at Constitution Hall in Washington,DC. Under the auspices of the National Academy of Sciences, an audience of presidential advisors, senators, andcongressional representatives gathered for a musical performance. On the stage were three loudspeakers. Stokowskiwas stationed at a control panel in the hall (Figure 4). Hismusicians remained in their rehearsal room in Philadelphiaawaiting their cue.In the rst act of the show, the audience listened to a scenewired from Pennsylvania to Washington. On the le-handside of the stage in Philadelphia, a handyman constructeda box with a hammer and saw. From the far right, anotherworker proered suggestions to his friend. “So realistic wasthe eect that to the audience the act seemed to be takingplace on the stage before them. Not only were the soundsof sawing, hammering, and talking faithfully reproduced,but the auditory perspective enabled the listeners to placeeach sound in its proper positions, and to follow the movements of the actors by their footsteps and voices,” wrote anobserver (Fletcher, 1992, p. 184). Next, a soprano sang Coming rough the Rye as she weaved across the stage in Philadelphia. At Constitution Hall, the phantom of her voice “appeared to be strolling on the stage” (Fletcher, 1992, p. 184).e show ended with an unforgettable duel in the dark between two trumpet players separated by more than a hundred miles. e two traded licks from their opposite postsin Constitution Hall and the Academy of Music in Philadelphia. But the audience was none the wiser. “To those in theaudience there seemed to be a trumpet player at each sideof the stage before them. It was not until aer the stage waslighted that they realized only one of the trumpet playerswas there in person” (Fletcher, 1992, p.184). The crowd was in awe.