mhelin

M/S stereo playback system
« on: September 22, 2007, 07:00:02 AM »
The more I think about it, the more it makes sense:
http://cas.umkc.edu/theatre/sound/msrec/msrecording.htm

You can use a regular stereo amplifier, got to build the M/S encoder though. You can also use the balance control on stereo amp to control the soundfield depth.


clintrubber

M/S stereo playback system
« Reply #1 on: September 22, 2007, 07:55:07 AM »
Nice idea  :grin:

Not sure how it would hold up in practice though, say a living room where you have set up speakers 'about right' both for the couch as well as for the dining table. Sitting at the table & using this method you might be getting a relatively roaring M-speaker further away and the softer diff-info from the nearest S-speaker closer to your ear. Same for the couch-area.

I figure a subwoofer & two satellites(sp?) might work better then, giving more 'juice' from the S-speaker (noticed how 'mono' some records can be ?)

But still looks like a nice idea for 'less compomised' speaker-setups though.

JohnRoberts

M/S stereo playback system
« Reply #2 on: September 22, 2007, 10:20:59 AM »
Back in the '80s I sold a "delay enhanced surround system" . The rear channels were quite simply a delayed version of L-R. By adding enough delay that the sound sources from the front speakers always arrive before the closer rear speakers, you keep the images firmly located in front of you.  

This is similar to the early Dolby movie surround system but they band-limited their surround channel and applied some NR.

This L-R+delay was quite effective at extracting ambience from good stereo recordings, while suppressing mono information in the surround speakers.  

JR
Cancel the "cancel culture", do not participate in mob hatred.

JohnRoberts

M/S stereo playback system
« Reply #3 on: September 22, 2007, 01:32:19 PM »
Quote from: "mediatechnology"


I seem to recall an early fake "quad" setup in the 70's that also had conventional L and R speaker arrangements but the two rear speakers, in series, were connected to the two + amp outputs to also present the difference component in the rear.


IIRC that was the Hafler/Dynaquad approach. Without delay the rear speaker location could be problematic. Pointing the speakers up in the air or bouncing off a wall gained some free delay and diffused the rear speakers as individual sources.

JR
Cancel the "cancel culture", do not participate in mob hatred.

mhelin

M/S stereo playback system
« Reply #4 on: September 22, 2007, 03:22:50 PM »
Quote from: "mediatechnology"
mhelin: You can fashion a simple M/S encoder this way:

http://www.ka-electronics.com/forum/php/viewtopic.php?f=6&t=15



THAT1240 seems to be available here for £2:
http://www.profusionplc.com/pro/gex/pcatdtl0?ipartno=THAT1240P08-U

I'd like to try the M/S speakers in my "home theatre" (which is also my "home studio"). The distance from the couch to the 2 meter wide screen is less than 3 meters so depending on where you sit the difference in sound is moderate (as the distance to both speakers is not equal). Also the current speakers are now on way of the drum set and I'd like to move them (speakers, not the drum set)  to ceiling as well as the main speaker in the M/S system (which I'd like to build), which would also doubles as a (mono) karaoke & small PA-speaker for rehearsals.

Actually here in Finland in 60's there was an engineer Tapio Köykkä who invented a kind of M/S surround sound system which he called "ortoperspekta" ( http://www.kolumbus.fi/epap/voimaradio/ortoperspekta/ortoperspekta6.html ). In the schematics shown there are secondaries of a pair of tube amps. I think that in addition the other channel has to inverted before the power amp for the system to work correctly. The 82k must be a typo.
--
Mikko

TedF

M/S stereo playback system
« Reply #5 on: September 25, 2007, 10:51:42 AM »
Some of you guys might have noticed my involvement with this subject.... I've been working on it for the last 2 years; there's a fair bit of info on my airsound website (www.airsound.net).
Certainly there's a huge future for this thinking, Alan Blumlein suggested in 1931 that 2-speaker listening is imperfect; just how imperfect you can only appreciate after listening at length to a different system, and then go back to conventional 'stereo' and be horrified by the phase and filter effects on your ears, things we get used to!
My 'Airsound' business is very commercial, operated by my marketing and PR people, but at the same time, it is founded on honest principles of physics and I welcome friendly debate!
The theatre sound idea of generating a spatial signal across the auditorium is an interesting one, I think I would still prefer to generate the spatial fields adjacent to the main loudspeaker, it would be more comfortable for the audience, but I'm very happy to be persuaded otherwise.
Where the 'Airsound' system (my implementation of a sum and difference system) is particularly effective is in small home HiFis, and in Surround sound systems for home theatre..... where the extreme 'ping-pong' effects are actually unnecessary, unwanted and blatantly annoying;  a sweeter spatial image is infinitely preferable. :grin:

mikep

M/S stereo playback system
« Reply #6 on: September 25, 2007, 01:08:31 PM »
fender was selling a guitar amp a few years ago with built in effects and an M-S stereo configuration... an open baffle speaker at 90 degrees to the main driver.  sounded cool IIRC.  I use M-S processing alot in my mastering adventures.

SSLtech

M/S stereo playback system
« Reply #7 on: September 25, 2007, 01:50:42 PM »
Look into ambisonic playback... Same thing with MORE than one axis.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Jim Zuehsow

M/S stereo playback system
« Reply #8 on: September 25, 2007, 03:14:09 PM »
Ok, let's see if I got this right. I set up a 5.1 ADAM nearfield system in my mix area so I could get the most accurate mix environment possible. Now we have people designing speakers with matrixes to eliminate the exact placement of sound so as to provide a more pleasent spacial effect. Why do I even bother to mix things with any concern for placement, since it will never be heard as the producer and artist wanted.
Most of these were abominations and sounded pretty bad. Remember years ago when Leslie tried to sell home speakers with rotating baffles to "distribute" the sound? Then there was Bose with their system, where you couldn't really tell where a sound was located. Then Polk designed a system which "cross-mixed" signals to the left and right speaker. I used to call that MONO! I've heard the Dolby system which simulates surround using 2 speakers. Not very convincing to me. Bose also has the same thing. I want the "ping-pong" effect, if that's what I'm trying for, and certainly don't want some synthetic matrix system determining what I hear.
Years ago, I heard a system using a pair of Maggies in front and back with the back pair being driven by a AudioPulse digital delay. It sounded very realistic on some material, and totally wrong on others. Still, the straight 2 channel stereo from the front pair sounded just fine.
I've also heard true Ambisonic playback, and built several of the decoders from Wireless World back in the 70's. That seemed to be the best solution, and I am somewhat sorry it never caught on.
Any speaker system that "changes" the sound to make it less accurate in either tone, placement, level, etc., is just plain wrong in my book. Since all playback systems are wrong to some extent, I try to choose the lesser of the evils and go with the system which gives me the most honest version of what it's fed, and accept the output, warts and all.
The concept of using M/S decoding for playback destroys any semblance of what the original program sounded like. It's great for recording, depending on the acoustics of the location, and when decoding to left and right for the mix, you can make artistic choices as to the "size" of the stage, and how the performance is "meant" to be heard. I see modifying this parameter to be equally bad as someone who has their tone controls cranked full on, "because it sounds better".

Jim Zuehsow
Eagle's Nest Studio
Eagle River, Alaska

SSLtech

M/S stereo playback system
« Reply #9 on: September 25, 2007, 05:11:08 PM »
Again, a guiding pronciple of Ambisonics is that playback systems can be set up to reproduce to the best of their abilities...

With this "Fake-M/S"version you do at least get a 'hard center'... Works well for offcenter listening. In THAT sense, it's not actually necessarily a 'smaller' sweet spot...

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.


SSLtech

M/S stereo playback system
« Reply #10 on: September 25, 2007, 06:20:20 PM »
Sorry... -I meant the original link; -but perhaps both, actually.

Depends on how you define the 'sweet spot'. It's a handy term to use, but in fact conventional stereo is particularly unforgiving, and other approaches can in fact be more so.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Jim Zuehsow

M/S stereo playback system
« Reply #11 on: September 25, 2007, 07:12:24 PM »
Keith is right, in a sense that traditional stereo is ungorgiving, but that is usually due to the invironment the speakers are in. Whether in a livingroom or a control room, I have found it essential to have a symetrical setup. I've been in many control rooms that were built with no thought given to how the room was affecting playback. For instance, a friend's control room has a sliding patio door off the left side of the console which is the machine room, and it's angled in such a way that anything hitting it goes around the room and comes in delayed to your right ear. He put a RPG on the back wall, but that didn't solve the problem in that room.
Some rooms are live-end/dead-end, and people think that solves all problems. It doesn't, if the room is still lop-sided. Back at the first commercial studio I worked at in 1961 the control room was about 8 feet wide and 24 feet long with a big old Altec 604 hung from the ceiling on the left side on chains. You had to sit sideways to mix anything there. About 4 years later, I stopped back there, and sure enough, old Wally had gone stereo, and hung another 604 on the right side on chains. They pointed directly at each other, spaced about 10 feet apart. He asked me to sit down and give a listen while he played back a tape. It was like having on a giant pair of headphones! I asked him how in the hell he managed to mix on these things, and he said he could because he was used to how they sounded.
Still, the factor of the room cannot be discounted in any playback system, and it seems most people make concessions regarding the acoustics of their listening space, either to pacify a spouse, or due to lack of money.
Wood floors are wonderful and can add a bit of life and warmth to a room. It is very important to strike a balance between treatments of a room. This will usually help to make the so-called "sweet spot" a little wider. But really, it is the culmination of so many elements, from the speakers used to the style of furniture, that all contribute to how successful an area is for sound reproduction.

Jim Zuehsow
Eagle's Nest Studio
Eagle River, Alaska

NewYorkDave

M/S stereo playback system
« Reply #12 on: September 25, 2007, 09:21:49 PM »
Your first commercial studio gig was in 1961?

I think you've just won the Prodigy-Pro "Elder Statesman" award   :wink:

bcarso

M/S stereo playback system
« Reply #13 on: September 25, 2007, 11:26:46 PM »
Let's see... I think I was working then too, but only for my father during the summer.  The enforcement of child labor laws was a bit more lax in those days.

Jim Zuehsow

M/S stereo playback system
« Reply #14 on: September 26, 2007, 03:48:31 AM »
Quote from: "NewYorkDave"
Your first commercial studio gig was in 1961?

I think you've just won the Prodigy-Pro "Elder Statesman" award   :wink:


Hey! watch it buddy! It was my senior year in highschool and I went to work at Super Recording in Glenellen, IL. The owner, Wally Super, was the uncle of my best friend, and that's how I got the job. Wally had worked for Columbia from the mid 1930's until he opened his own place in 1953. He had a big old W/E console and several lathes and a bunch of Ampex 300's and a complete Ampex tape duplicating system. When I got out of the Army, I went to see him and he set up a meeting with a friend of his at Columbia in Chicago, which led to me getting hired, and eventually working at Columbia in LA, until the union lockout in 1972, when we all lost our jobs. Bummer!
So yes, I guess I have been at this a while, owning and operating a studio in some manner for the past fourty some years. Of course I do have a straight gig too as a technician for AT&T (since they seem to have plenty of money) and work at the Eagle River Gateway Earth Station, where my duties include taking care of everything from Sonnet fiber systems to doing satellite uplinks all over the place. Still, pro audio is my mistress.

Jim Zuehsow
Eagle's Nest Studio
Eagle River, Alaska

Jim Zuehsow

M/S stereo playback system
« Reply #15 on: September 26, 2007, 02:26:00 PM »
Quote from: "NewYorkDave"
Your first commercial studio gig was in 1961?

I think you've just won the Prodigy-Pro "Elder Statesman" award   :wink:


That's just a nice way of saying "Geezer" I think!

Jim Zuehsow
Eagle's Nest Studio
Eagle River, Alaska


 

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