The Centre channel: what signal gets sent to it? How demanding compared to Left and Right?

[fieldcar]

Listening on average (more than a few second) at 110dBSPL(A) is madness and a sure way to bring permanent damage to your ears. The long term average SPL is different to session averages we normally talk about in audio forums. It is sad that the grave risk of loud listening is still not properly understood even after we read stories about many 70s rock stars went deaf. The damage is irreversible and cumulative. I urge everyone to read what US CDC will say about loud music listening.

Agreed. This (and I'm getting older ) is why I don't go to rock & EDM concerts anymore. Way too loud, and a lot of the times, the speakers & venue acoustics just don't sound that great. Most of the SPL I experience is infrasonic from the LFE channel, and I don't think it does any harm. I'm certain that I'm nowhere near dangerous levels during normal movie watching and music listening experience. Just like @amirm, I'm only doing these loud benchmarks for no more than 10-15 seconds maybe few times a year. It's solely done to validate my configuration and system performance.

 

[sarumbear]

Agreed. This (and I'm getting older ) is why I don't go to rock & EDM concerts anymore. Way too loud, and a lot of the times, the speakers & venue acoustics just don't sound that great. Most of the SPL I experience is infrasonic from the LFE channel, and I don't think it does any harm. I'm certain that I'm nowhere near dangerous levels during normal movie watching and music listening experience. Just like @amirm, I'm only doing these loud benchmarks for no more than 10-15 seconds maybe few times a year. It's solely done to validate my configuration and system performance.

I agree. Meanwhile, unless it is semantics there is no LFE in music. Live music reproduction is even mono!

 

[fieldcar]

I agree. Meanwhile, unless it is semantics there is no LFE in music. Live music reproduction is even mono!

Hehehe. Unless it's one of those awful bass test "songs". 20Hz boi!

 

[gene_stl]

At its origin, stereo meant 3 dimensional - stereo recording and playback was a system that allowed the reproduction of space and depth - it had no implication of 2 channels.

Bell Labs public demonstrations of Stereophonic sound in 1933, were 3 channel - and for quite a while the optimal "stereo" system was 3 channel.

The move to two channel, was driven by the primary recording medium, and the ease of reproducing two channels via the two walls of the vinyl groove on a record.

Still the optimal way to reproduce stereo remains... 3 channel.

A few years back, Martin Logan was demonstrating 3 channel stereo using a Bryston SP2 set to Dolby PLII to extract the center channel - by all accounts it was excellent. (and after those demo's many tried with different processors to achieve similar results... but even with a specified decoder, it proved to be very implementation sensitive)

Meridian have Trifield - which achieves the same result.

3 Channel stereo was always the optimal alternative - and now with our home theatre based systems, we have the opportunity to make it reality, make it mainstream.

Sadly, I am unsure what current generation decoders will do with decoding 2 channels into 3 (or 3.1/3.2/3.3) - PLII seems to no longer be on most AVR's, and I have no idea how good (or bad) the current "Dolby family" iteration (Dolby Surround ) is.

As I upgrade and update my two channel stereo to multichannel , one of the things I am looking forward to the most is listening to a bunch of classic Mercury and 35mm tape rereleases on SACD that have three channel stereo. Even though some were recorded in the 1950s. I keep collecting them when I run across them. A three channel stereo recording of Jascha Heifetz. Yummm!

 

[More Dynamics Please]

Regarding the Bell Laboratories stereo research in the 1930s, experimentation was done with both 2 and 3 channels. Home audio recordings of the era were all on vinyl disks that could only accommodate 2 separate channels in the V groove so that became the home stereo standard. Film makers on the other hand could fit more than 2 channels on film so the movie industry adopted 3 channels with a center for stereo sound tracks. Had home audio in the 1930s been recorded on a medium that didn't limit stereo to 2 channels it's possible that 3 channels would have become the home audio stereo standard.

 

[KMO]

3 Channel stereo was always the optimal alternative - and now with our home theatre based systems, we have the opportunity to make it reality, make it mainstream.

Sadly, I am unsure what current generation decoders will do with decoding 2 channels into 3 (or 3.1/3.2/3.3) - PLII seems to no longer be on most AVR's, and I have no idea how good (or bad) the current "Dolby family" iteration (Dolby Surround ) is.

I'm with you. With 3 speakers covering the front, the mixer (automatic or human) has more flexibility on how to put stuff in front of the listener. Not only do they have a position control, they have a width control.

Many multichannel music mixes will quite deliberately manipulate the width by choosing which elements to send to C, which to send to L+C+R, and which to send to L+R. Some vocalist overdubs might be centre-only, for example, clearly distinguishing them tonally from the main vocals in L+C+R.

Even in the Atmos world, Atmos objects have width. If a small object is positioned between real speakers, it's forced to phantom, and hence be wider than ideal.

The centre front position is really important, hence why it shouldn't only be reproducible by a phantom. We want to have a width control there, not force things always wide.

I'm also on PLIIx, and a great fan, and sceptical of Dolby Surround. It does have a "centre spread" toggle, which I gather is equivalent to flipping between "0" and "3 or 4" in Dolby Pro Logic Music's "centre width". But that's the only control.

PLII wasn't brilliant at doing less than 5 channels itself, mind. I gather LFE is routinely thrown away with anything less than 5 speakers in a lot of systems, so 3.1 with LFE isn't possible.

 

[sarumbear]

Regarding the Bell Laboratories stereo research in the 1930s, experimentation was done with both 2 and 3 channels. Home audio recordings of the era were all on vinyl disks that could only accommodate 2 separate channels in the V groove so that became the home stereo standard. Film makers on the other hand could fit more than 2 channels on film so the movie industry adopted 3 channels with a center for stereo sound tracks. Had home audio in the 1930s been recorded on a medium that didn't limit stereo to 2 channels it's possible that 3 channels would have become the home audio stereo standard.

There were no 2-ch home recording for more than decade after those tests. Multi channel was available as early as mid 40s in cinemas with Fantasia. It took another decade for stereo to arrive to homes.

 

[sarumbear]

I'm with you. With 3 speakers covering the front, the mixer (automatic or human) has more flexibility on how to put stuff in front of the listener. Not only do they have a position control, they have a width control.

Many multichannel music mixes will quite deliberately manipulate the width by choosing which elements to send to C, which to send to L+C+R, and which to send to L+R. Some vocalist overdubs might be centre-only, for example, clearly distinguishing them tonally from the main vocals in L+C+R.

Even in the Atmos world, Atmos objects have width. If a small object is positioned between real speakers, it's forced to phantom, and hence be wider than ideal.

The centre front position is really important, hence why it shouldn't only be reproducible by a phantom. We want to have a width control there, not force things always wide.

I'm also on PLIIx, and a great fan, and sceptical of Dolby Surround. It does have a "centre spread" toggle, which I gather is equivalent to flipping between "0" and "3 or 4" in Dolby Pro Logic Music's "centre width". But that's the only control.

PLII wasn't brilliant at doing less than 5 channels itself, mind. I gather LFE is routinely thrown away with anything less than 5 speakers in a lot of systems, so 3.1 with LFE isn't possible.

Where do you buy those 3-ch material? Otherwise, you are being the artist and re-mixing the music.

 

[krabapple]

I have seen a couple of comments in general discussions on ASR recently that the centre channel requires a more 'muscular' speaker than the left and right speakers.

Nonsense.

I would say what's 'required' is that it be timbrally matched to the Left and Right. (and those should be good speakers too)

For maximum utility as an good-sounding anchor for people sitting well off the central axis, it should have good horizontal dispersion characteristics too.

 

[KMO]

Where do you buy those 3-ch material? Otherwise, you are being the artist and re-mixing the music.

There's quite a large catalogue of multichannel material available on SACD, DVD-A, Blu-ray and increasingly on streaming services - Atmos is being pushed quite hard now. Quadraphonic Quad is a good place to start, despite the centre-unfriendly name. It covers all multichannel formats. (There are a lot of 4.0 quadraphonic reissues out there too, aside from the newer 5.1 or Atmos, and the really old 3.0).

My last pick-up was the 5.1/7.1/Atmos mix of the Beatles' Let It Be, accompanying the new Peter Jackson film.

That's fairly typical in being remixed from the original master stems primarily into Atmos, with the 5.1 mix somewhat manually crafted alongside that. The 7.1 version I'm playing is largely an automated Atmos downmix (but produced during authoring, rather than by the receiver, as it's a backwards compatibility layer).

 

[krabapple]

Exclusively 3-channel releases exist but are comparatively rare. Most are classic orchestral recordings on Mercury 'Living Presence' , RCA 'Living Stereo', et al. A smattering a classic jazz multichannel releases are sourced from 3 channel masters too (e.g Kind of Blue). Some of the jazz releases have 'room ambience' added as rear L and right content so that the rear channels of a surround system have something to do.

Aside from that of course nearly every other multichannel format music release apart from straight quad reissues has some content mixed to the center channel.

 

[sarumbear]

There's quite a large catalogue of multichannel material available on SACD, DVD-A, Blu-ray and increasingly on streaming services - Atmos is being pushed quite hard now. Quadraphonic Quad is a good place to start, despite the centre-unfriendly name. It covers all multichannel formats. (There are a lot of 4.0 quadraphonic reissues out there too, aside from the newer 5.1 or Atmos, and the really old 3.0).

My last pick-up was the 5.1/7.1/Atmos mix of the Beatles' Let It Be, accompanying the new Peter Jackson film.

If you noticed I asked for 3-ch not immersive audio, which is different to the argument of 2 or 3 ch playback. There is very few immersive encoded music done by the artists themselves. Almost all that is available by the record labels without the artist in control. I like to hear what the artists agreed for release. For instance most early The Beatles albums were in mono. Thankfully many agrees with me and the anthology was released in mono as well.

I can’t make myself to change what the artist intended.

 

[Newman]

What would the term be for the highest perceptual/experienced SPL of a highly dynamic audio track in the same way that a decibel meter has a 1.0s averaging period?

Probably “Max” on the SPL meter.

 

[krabapple]

If you noticed I asked for 3-ch not immersive audio, which is different to the argument of 2 or 3 ch playback. There is very few immersive encoded music done by the artists themselves. Almost all that is available by the record labels without the artist in control. I like to hear what the artists agreed for release. For instance most early The Beatles albums were in mono. Thankfully many agrees with me and the anthology was released in mono as well.

I can’t make myself to change what the artist intended.

The Beatles surround remixes were done with the permission of the surviving Beatles (and the estates of the other two).
Obviously the same holds for Pink Floyd. It also holds for lots of other bands whose albums have been remixed to 5.1 in the modern era for rerelease -- Queen, Yes, Jethro Tull, Steely Dan come to mind offhand. (A fair number also had artist-approved 'quad' release versions back in the day)

The bulk remixing of various individual songs for Atmos is a different, and much more recent, thing,

And again, there are original 3-channel recordings, most dating from before 1960, that have been (since the appearance of SACD and other surround disc media ) released in 3-channel playback formats.

 

[fieldcar]

Probably “Max” on the SPL meter.

While that's true, I was mainly talking about what the term would be for when an individual, not an SPL meter, are experiencing sustained high volumes. I guess "long envelope maximum SPL with perceptual A-weighting" doesn't roll off the tongue like "peak volume". But in the end, it was all an exercise in pedantry and semantics.
We have fun here sometimes.

 

[Sancus]

Almost all that is available by the record labels without the artist in control. I like to hear what the artists agreed for release. For instance most early The Beatles albums were in mono. Thankfully many agrees with me and the anthology was released in mono as well.

I can’t make myself to change what the artist intended.

I think the other way to look at it is that the audio engineers are also part of the creative process.

Personally I don't much care what the artists intended, though, just what sounds best to me. Otherwise I wouldn't EQ albums that sound overly bright nor would I seek out uncompressed versions of music that the artists intentionally released overly(to me) compressed.

If I had access to the multitracks and could do my own surround mixes I absolutely would do that too.

 

[maverickronin]

Death of the author..err...artist.

There's a can of worms...

 

[fieldcar]

I think the other way to look at it is that the audio engineers are also part of the creative process.

Personally I don't much care what the artists intended, though, just what sounds best to me. Otherwise I wouldn't EQ albums that sound overly bright nor would I seek out uncompressed versions of music that the artists intentionally released overly(to me) compressed.

If I had access to the multitracks and could so my own surround mixes I absolutely would do that too.

The optimist in me would say that Atmos music may be that step in the right direction, as I'd assume it's comprised of object based audio stacks. Imagine having sliders for dynamics/compression, panning width, room reverb, and a full EQ for every song.

...It's never going to happen.

 

[audio2920]

A center channel will give you a much correct localization when sitting to either side of the sweet spot.

I agree. I'm sorry if it seemed I was implying a center is detrimental in itself. (Although a bad center channel may be worse than no center channel)

I just meant the "center" came in to existence in movies when stereo became a thing, but it really didn't work in cinema so Dolby introduced the LtRt matrix and it's been with us ever since.*

When I say "less need" I don't mean that there isn't benefit in a consumer setup, it's just that if you've ever listened to straight L/R in a cinema you'll know the phantom image is hopeless, so in a good home setup, the advantage is less than in a cinema.

(*edit: commercially and to the mass market I mean. No doubt there were systems pre-dating this, but nothing I would consider a real standard like Dolby)

 

[sarumbear]

I think the other way to look at it is that the audio engineers are also part of the creative process.

Part means the artist is still involved.

Personally I don't much care what the artists intended, though, just what sounds best to me. Otherwise I wouldn't EQ albums that sound overly bright nor would I seek out uncompressed versions of music that the artists intentionally released overly(to me) compressed.

If I had access to the multitracks and could do my own surround mixes I absolutely would do that too.

I respectfully but vehemently disagree. Artists' work are sacrosanct. They should be protected and their work left untouched. Without them there will be no society.