Are three channels better than two for stereo reproduction?

[terryforsythe]

I feel like it is very difficult to have a conversation about how my system sounds and what improvements can be made without having the people giving advice also listen to the system.

I don't know where you live, but if it is anywhere near me I would be willing to come check it out. Also, you could hear mine and get a sense for what it sounds like.

 

[MaxwellsEq]

Out of curiosity, do you think an anechoic chamber is the ideal listening environment?

I've listened to speakers in an anechoic chamber. It's not something I'd recommend. In one regard, it's a bit like someone playing an instrument in an open field (i.e. with no walls and ceiling). But your brain can't cope with what is quite an unnatural situation, probably because such "background silence" is simply unnatural (even in a field there is air movement). Maybe also perhaps because we ALWAYS experience a floor bounce in nature, even in the middle of a field with no walls or ceiling (no matter how absorbent the soil is).

Have you tried listening to your speakers outside? If not, you will be in for a shock.

but I eventually realized that stereo recordings are 2-dimensional, while real sound is 3-dimensional.

You only have two ears, but perceive height information through the way audio is routed around your head and pinnae! But also, in a relatively live and largish room with, say, a flautist playing, you hear the direct source, then the reverb off of all the walls, the floor and the ceiling and your brain does the mathematics in real time to understand the space and height information.

With only two microphones, the recording still manages to capture the the reverb off of all the walls, the floor and the ceiling and encodes it in the left and right channels as level and phase. Part of the challenge we have domestically is that the rooms we are in can dominate this fine timing/phase detail that's in the master recording, but, astonishingly, our brains seem to manage to understand the two rooms "superimposed".

 

[Robin L]

Are we sure this is an issue with my setup and not physical limitations of having two speakers? I feel like it is very difficult to have a conversation about how my system sounds and what improvements can be made without having the people giving advice also listen to the system. The reason I bring this up is because even if I move closer to the speakers (which lowers rear wall reflections), the image is still more stretched when not hard panned and the sweet spot becomes way smaller. I find it hard to believe that with just speaker positioning and acoustical treatment, I can have phantom images be as strong as real images, especially considering the acoustical interference at play with phantom images.
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From my experience, the room itself is a big part of the problem. I've had many different systems over five decades and right now is about as good as I've ever experienced as regards imaging. I might have simply lucked into to right positioning of speakers, the right speakers and the right position for listening. My speakers are 2-way towers (Infinity Primus 250), the tweeters are above my head, the center mid/bass driver is at ear level, the speakers are turned out, slightly off-axis. The center image is about as good as I have previously experienced, with the exception of dedicated 3.0 or 5.1 SACDs.

My understanding is that your speakers are exceptional. If I were in your shoes, I'd work with speaker placement a bit more before adding a third speaker.

 

[Blumlein 88]

Are we sure this is an issue with my setup and not physical limitations of having two speakers? I feel like it is very difficult to have a conversation about how my system sounds and what improvements can be made without having the people giving advice also listen to the system. The reason I bring this up is because even if I move closer to the speakers (which lowers rear wall reflections), the image is still more stretched when not hard panned and the sweet spot becomes way smaller. I find it hard to believe that with just speaker positioning and acoustical treatment, I can have phantom images be as strong as real images, especially considering the acoustical interference at play with phantom images.

In an earlier post you wrote your phantom imaging was pretty good and then described one that is not good at all. You can have very pinpoint phantom centers.

Try this test to see how your speakers do. Now a center may help, something about your setup might allow you to adjust for a good center without adding a speaker or whatever. But this test will give you an idea how well your imaging is with your set up.

Online LEDR™ Sound Test | Listening Environment Diagnostic Recording Test

Audio Test Tones : check your stereo system for correct imaging

www.audiocheck.net

These two other tests are worthwhile too.

Stereo Perception, Sound Localization & Auditory Cues

Describing the auditory principles behind Stereophonic Sound, through different audio examples.

www.audiocheck.net

Online Stereo Polarity (Phase) Sound Test

Checks your loudpeakers wiring.

www.audiocheck.net

 

[LowShelfFilter]

Try this test to see how your speakers do. Now a center may help, something about your setup might allow you to adjust for a good center without adding a speaker or whatever. But this test will give you an idea how well your imaging is with your set up.

Online LEDR™ Sound Test | Listening Environment Diagnostic Recording Test

Audio Test Tones : check your stereo system for correct imaging

www.audiocheck.net

The only one that doesn't sound correct at all is the behind one.

In an earlier post you wrote your phantom imaging was pretty good and then described one that is not good at all. You can have very pinpoint phantom centers.

The point of this thread was not to determine if my phantom images were "good enough," as this is only based on input from my end. It could be that you think the phantom centers in my system are very pinpoint. I wanted insight on a more conceptual level if LCR for stereo brings benefits.

Now, is "very pinpoint" to you the same as the real thing? If so, you must also take the position that imaging has nothing to do with tonality. Imagine you are in an anechoic chamber and hear someone's voice hard panned to the right, then hear it centered. If imaging and tonality are related, the difference in tonality caused by acoustical crosstalk and incorrect HRTF processing would also result in a difference in perceived image size.

 

[theREALdotnet]

Why do audio legends like Floyd Toole up-mix if stereo is so good and realistic?

Argument from eminence or authority is a logical fallacy. I for one have learned to take Toole’s proclamations with a big shovel of salt, they too often fly in the face of practical experience.

 

[theREALdotnet]

I'm leaning toward your room, or the speakers' placement in the room, as being the issue. You could experiment with different speaker positions and orientations (i.e., not pointed directly at you), and/or delve into room treatment.

Exactly. I find that placing speakers too close to side or front walls is a sure way of diminishing sound stage and imaging. I also find that in addition to wall distance, treating side and front walls with absorption and/or diffusion yields further improvement.

 

[JSmith]

Out of curiosity, do you think an anechoic chamber is the ideal listening environment? I

No, an anechoic chamber is "dead", as in all sound waves are absorbed and not reflected (well reflections are highly minimised anyway). They are for acoustic testing purposes, providing a controlled environment for same. One does not want a dead room for general listening, some reflected sound is beneficial...

I wanted insight on a more conceptual level if LCR for stereo brings benefits.

The source would need to be 3 channel, not 2... as has been mentioned.


JSmith

 

[PGansz]

Considering that two speakers cannot accurately reproduce a 3D acoustic event in the first place, would using a center channel summed to mono with LR playing normally provide for a superior/more realistic listening experience than just using LR? Please note that I am not referring to listening to three channel recordings, but rather up-mixing two channel recordings to three channels.

I am considering routing audio as such with a MiniDSP 2x4 product:
Output 1: Right Speaker (Right input channel)
Output 2: Left Speaker (Left input channel)
Output 3: Center Speaker (Right + Left input channels)
Output 4: Subwoofer(s) (Right + Left input channels)

From Floyd Toole's book, there are significant acoustic advantages to using a center channel. Are there any downsides to using LCR for stereo reproduction instead of LR?
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100% agree except I'll say that an ideal setup would be a 3.2 processor/pre amp. I find exceptionally stupid with modern day tools like klippel that anyone would prefer the sound power of stereo vs LCR combo. It makes zero sense to me.

Takes me back to the obvious choice; if no one is going to make one of those you might as well get a HT processor with streaming capability and a three channel purifi/icepower/hypex amp.

Unless budget is a problem in which case you suffer the consequences of that like anything else in life.

 

[LowShelfFilter]

No, an anechoic chamber is "dead", as in all sound waves are absorbed and not reflected (well reflections are highly minimised anyway). They are for acoustic testing purposes, providing a controlled environment for same. One does not want a dead room for general listening, some reflected sound is beneficial...

The source would need to be 3 channel, not 2... as has been mentioned.


JSmith

If you can downmix surround, why can't you upmix stereo? My understanding is that the optimal way to do it involves having the left and right channels only play difference signals while the center channel plays the mono part of the song. This way, mono content only plays through the center speaker too, as intended.

 

[dlaloum]

No, an anechoic chamber is "dead", as in all sound waves are absorbed and not reflected (well reflections are highly minimised anyway). They are for acoustic testing purposes, providing a controlled environment for same. One does not want a dead room for general listening, some reflected sound is beneficial...

The source would need to be 3 channel, not 2... as has been mentioned.


JSmith

Here is a contrarian perspective for you....:

If you want to use some of the simulated room/hall/venue systems, particularly the Yamaha ones, that were based on an extensive project of measuring listening spaces and performance spaces worldwide, then an array of surround speakers, driven by such a processor would work best in an anechoic space, as the necessary reflections are provided by the surround system and not the room.

In fact for these kind of systems to work at their best, it can be theoretically argued, that an anechoic space is the only way they could function as advertised!

But yeah, in the real world, not a good thing!

 

[LowShelfFilter]

If you can downmix surround, why can't you upmix stereo? My understanding is that the optimal way to do it involves having the left and right channels only play difference signals while the center channel plays the mono part of the song. This way, mono content only plays through the center speaker too, as intended.

Does anyone know if doing this is possible with a MiniDSP 2x4 HD?

 

[dlaloum]

If you can downmix surround, why can't you upmix stereo? My understanding is that the optimal way to do it involves having the left and right channels only play difference signals while the center channel plays the mono part of the song. This way, mono content only plays through the center speaker too, as intended.

Yes you can.

All the mixers, upmix stereo.

Of the current crop of "standard" mixers found ubiquitously on most AVR's.... DSU does the best job with stereo.
Some people love Auromatic as an alternate stereo upmixer.

Good stereo upmixers, will do very very little with the surround channel, but will use the center quite substantially.

Historically the best stereo upmixers have been Logic7 (later Logic16) and Dolby PLII - both are now "orphan" technologies.

Some of the upmixer options, are designed for wizz bang, impressive effects - look at the various "listening space" simulators... they take stereo and provide lots of surround (and height) effects.... mostly these do nothing constructive, although they can be fun.

 

[terryforsythe]

Does anyone know if doing this is possible with a MiniDSP 2x4 HD?

I believe so, using the equations @gnarly posted. See my post #58.

I know for sure the miniDSP Flex and SHD will do so, as well as CamillaDSP.

 

[JSmith]

If you can downmix surround, why can't you upmix stereo?

Of course one can... but you're creating a faux channel based on 2 channels.


JSmith

 

[LowShelfFilter]

Of course one can... but you're creating a faux channel based on 2 channels.


JSmith

What if it sounds better though? Isn't that what ultimately matters? And are you really creating a faux channel? It's still stereo. The side speakers only play difference content while the center speaker only plays what's supposed to be in the center anyway. It's a best of both worlds approach. It even improves imaging, as what comes from the center comes from a real speaker.

 

[dlaloum]

Of course one can... but you're creating a faux channel based on 2 channels.


JSmith

As opposed to creating faux phantom audio images?

Unless you are talking about binaural recordings and headphones, "stereo" (which does NOT imply 2 channels - but rather implies "solid" audio impressions) is an outcome - and one which extensive experimentation has shown can best create the requisite illusion of solidity through the use of 3 speakers.

 

[Todd68]

Here’s my two cents. If your priorities are for better coverage in multiple seats for HT, then surround sound or more than two channels is needed. But for most music or two channel recordings, I’d rather have a pair of stereo speakers that are capable of portraying excellent imaging and spatial cues. Then you must spend time with positioning (speakers and seating position) and at least some basic room treatments.

Watching movies with my setup, just two channels, sitting in the sweet spot I can hear well defined sounds coming from behind and overhead and you’d be fooled into thinking there’s surround speakers back there!

 

[theREALdotnet]

Here’s my two cents. If your priorities are for better coverage in multiple seats for HT, then surround sound or more than two channels is needed. But for most music or two channel recordings, I’d rather have a pair of stereo speakers that are capable of portraying excellent imaging and spatial cues. Then you must spend time with positioning (speakers and seating position) and at least some basic room treatments.

Yes, this why I have separate systems for both. A cheap and cheerful surround system in the living room for watching movies and TV, and a dedicated stereo listening room for music.

 

[LowShelfFilter]

I believe so, using the equations @gnarly posted. See my post #58.

I know for sure the miniDSP Flex and SHD will do so, as well as CamillaDSP.

I have a MiniDSP 2x4 Flex. Do you know where I am supposed to input the formulas?