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live sound - mono or stereo?

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live sound - mono or stereo?

Postby calmposer a » Wed Nov 21, 2012 7:41 pm

I've been curious about this for a while - trying to move around large venues / festival stages to see whether the engineers use any stereo imaging whatsoever.

My impression so far (as well as gut feeling) is that they don't, as these spaces (whether closed or open) are so large, that no listener would be able to perceive an image like this.

It's crucial for me right now to understand this as I'm programming a live show - would you do a mono summing of stereo samples or stereo keyboard instruments? Any further thoughts anyone? :headbang:
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Re: live sound - mono or stereo?

Postby shufflebeat » Wed Nov 21, 2012 7:55 pm

I used to use a stereo chorus pedal and short 'room' stereo delay on acoustic guitar. Both effects sounded much better in stereo as well as taking up much less space in the picture, leaving other instruments better defined.

Over a couple of months I did some gigs where the PA was set up in mono. As soon as I switched into stereo the sound disappeared into itself. Since then I've changed my settings to allow me the option of running the FX in mono.

It works but doesn't sound half as good

In most cases I'd run one side rather than summing the outputs to avoid "cancelling" side effects
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Re: live sound - mono or stereo?

Postby Wimek » Wed Nov 21, 2012 9:49 pm

in the early nineties I was live sound engineer for two bands, a heavy metal and a pop band. They played in small venues (200-400 persons). Back then I didn't mix into full stereo, but I did use the stereo image to separate some instruments a bit. (example: two guitars, one a bit panned left, the other a bit panned right) On the positive side the result was a less congested mix, on the negative side for people on the sides some instruments were less prominent in the mix...

Your question about large venues makes me wonder... Thinking about a festival in Torhout (Belgium) I've been to, I can't imagine mixing in stereo on a field for 60000 people. However, maybe it could work in halls of a few thousand people...

Let's hope somebody in this forum has got the right experience , you made me curious now!
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Re: live sound - mono or stereo?

Postby Mike Stranks » Wed Nov 21, 2012 10:22 pm

Virtually all of the time I mix in mono for the reasons touched on - with a dispersed audience then there's comparatively few that would hear a balanced/equal stereo image.

The only exception is with a solo guitarist I work with who always wants a stereo sound-system to make maximum impact with the ping-pongs and other 'wide' effects he uses. These are so obvious that most people in the room can hear them even if quite off to one side. Of course, said musician also wants a stereo (reversed) foldback system in order to hear what's happening with the effects himself. Interestingly when he's played at a couple of the larger and more prestigious venues in the UK and his management put his 'stereo' requirement in the rider those venues have come back with a 'no can do'!
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Re: live sound - mono or stereo?

Postby hollowsun » Wed Nov 21, 2012 10:50 pm

Back in the day when I was working almost every night mixing for live bands, I worked in 'moreo' or 'steno' - that is, a narrow stereo mix that's kind of almost mono but not ... panpots no more than 10-o-clock and 2-o-clock, at a push in a smaller venue, maybe with DI'd synths, perhaps 9<>3-o-clock.

There are a lot of (ahem) 'stereo' effects, etc., that just collapse in mono, hence my reason for maintaining some stereo.

Your call though and it might/will vary from venue to venue.
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Re: live sound - mono or stereo?

Postby Dave Rowles » Wed Nov 21, 2012 11:12 pm

Mike Stranks wrote:Interestingly when he's played at a couple of the larger and more prestigious venues in the UK and his management put his 'stereo' requirement in the rider those venues have come back with a 'no can do'!

Meh, that's just laziness. I know a lot of venues probably don't have a desk that will do proper stereo auxes, but all you need is 2 aux sends and you can fake a stereo monitor system.
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Re: live sound - mono or stereo?

Postby Sam Spoons » Wed Nov 21, 2012 11:42 pm

I remember in the early '70's car stereo manufacturers telling us the car was the perfect environment for a stereo audio sysyem as everybody was sitting in a fixed position!!!....... No, I didn't get it then and still don't now. I guess it's a good analogue of a live audience where the listeners are in widely different parts of the stereo image, Hi Fi buffs (and mix engineers) calculate their sitting position to within a few tens of centimetres to maintain that elusive stereo image and from the right position 'stereo' can be amazing. Elsewhere it can detract from the performance. Interestingly an experienced engineer friend said that with a loud backline he may mix the guitar to the right of the singer (or visa-versa) louder in the left hand PA stack just so the audience that side can hear him as intended.
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Re: live sound - mono or stereo?

Postby seablade » Thu Nov 22, 2012 3:50 am

The vast majority of systems, even though they may LOOK stereo, are in fact mono coverage. To properly implement a true stereo system you need to have complete coverage of each channel to every seat in the house, which as you noticed is very difficult to do in many venues.

Does this stop some engineers from trying to run in stereo? Not at all, but some seats won't hear part of the show and as a result is generally not a good idea.

As such running in mono is more common than you might think, and yes when I did touring I would modify stereo or mono depending on the venue. I suspect many engineers follow the same strategy.

If your system is capable of true stereo coverage, then yes by all means mix in stereo and most will. If not however mix in mono.

By the way, there are rules that help predict how well a stereo image will translate to various seats in the house, and a proper system design will be done with these rules in mind. There are limitations to difference in volume and arrival time that must be respected to maintain stereo imaging, but obviously the larger the difference the worse the image tends to translate.

It's funny, you can actually maintain a stereo image in a section covered by a mono delay depending on the system design(Provided of course the main FOH is in stereo). Our ears are funny things;)

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Re: live sound - mono or stereo?

Postby TheChorltonWheelie » Thu Nov 22, 2012 7:37 pm

calmposer a wrote:I've been curious about this for a while - trying to move around large venues / festival stages to see whether the engineers use any stereo imaging whatsoever.

Some definitely do, I've done a few tributefest/Glastonbudget concerts and they were stereo. However, the channels weren't panned full left/right, they were at 10:00am/2:00pm at most, so it's a half-way house. The issue is obviously that hard-panned left signals can't be heard by the far right, and vice versa, and in all truth you're unlikely to hear the stereo effect given the distance between each speaker bank.

On smaller gigs we do use stereo, but then the left/right banks are no more than 25/30ft apart, with an audience depth of around 40ft, so it does work to a certain degree.
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Re: live sound - mono or stereo?

Postby damoore » Thu Nov 22, 2012 10:36 pm

A Leslie sounds better in stereo. You don't really care about "image" - what matters is the motion, which you lose entirely in mono. I saw Jimmy Smith on his last tour playing through two Leslie's mic'd at 180 degrees and in mono in the FOH you couldn't hear the Leslie effect at all! I could see him hitting the half moon switch but any sense of change of speed was totally absent.
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Re: live sound - mono or stereo?

Postby seablade » Fri Nov 23, 2012 1:00 am

damoore wrote:A Leslie sounds better in stereo. You don't really care about "image" - what matters is the motion, which you lose entirely in mono. I saw Jimmy Smith on his last tour playing through two Leslie's mic'd at 180 degrees and in mono in the FOH you couldn't hear the Leslie effect at all! I could see him hitting the half moon switch but any sense of change of speed was totally absent.

There is no difference between 'image' and 'motion' in this context, they are the same thing.

In a system not capable of stereo, you won't have motion, it will sound like it is getting louder and softer only, half the time not hearing it at all pretty much.

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Re: live sound - mono or stereo?

Postby calmposer a » Mon Dec 03, 2012 12:39 am

Thank you shufflebeat, Wimek, Mike Stranks, hollowsun, Sam Spoons, Seablade, and TheChorltonWheelie for the interesting replies!

From this I have learnt the following:

1. If possible to make any component work in mono rather than stereo then do this (true for both musicians and engineers).

2. If present, any stereo image in a live context will be narrow.

Thanks! :headbang:
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Re: live sound - mono or stereo?

Postby Hugh Robjohns » Mon Dec 03, 2012 11:05 am

There is more than one way to achieve a stereo effect. Pan pots work by splitting a signal into two (left and right) and apportioning different levels to each side. The image appears to come from the louder side, with about 16dB of difference being sufficient to create the illusion of being fully panned.

However, panning can also be achieved using different time delays on equal volume signals on both channels. A couple of milliseconds of delay is enough to push an image well off to one side for anyone standing on the centre line.

This method wouldn't be acceptable for records or broadcasting because of mono compatibility issues, but it can be useful in a live sound situation where there is no electrical summing of the two channels. Anyone standing between the two speaker arrays will therefore hear a reasonable stereo effect, but -- usefully -- anyone standing well off to the side still hears every source at the intended mix level regardless of where they are standing relative to the speakers...

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Re: live sound - mono or stereo?

Postby seablade » Mon Dec 03, 2012 3:16 pm

Hugh Robjohns wrote:There is more than one way to achieve a stereo effect. Pan pots work by splitting a signal into two (left and right) and apportioning different levels to each side. The image appears to come from the louder side, with about 16dB of difference being sufficient to create the illusion of being fully panned.

However, panning can also be achieved using different time delays on equal volume signals on both channels. A couple of milliseconds of delay is enough to push an image well off to one side for anyone standing on the centre line.

This method wouldn't be acceptable for records or broadcasting because of mono compatibility issues, but it can be useful in a live sound situation where there is no electrical summing of the two channels. Anyone standing between the two speaker arrays will therefore hear a reasonable stereo effect, but -- usefully -- anyone standing well off to the side still hears every source at the intended mix level regardless of where they are standing relative to the speakers...

hugh

This is absolutely correct, but it should be kept in mind, in larger systems especially, that just because you have stereo coverage up front(Or Pseudo stereo, in this case), doesn't mean you don't still have mono fills for delay fills or front fills so if you do this, you need to make sure that you don't sum these signals to mono in the matrix for the various fill locations.

Every system has trade offs. Probably the most difficult to achieve in this aspect is having a system capable of providing the appropriate delays that Hugh mentioned, you can do it with some tricks on most digital consoles that have input delays(Split the inputs to seperate channels, route each channel to only one side, and affect the delay on the input for each channel), but to get a true solution where you can delay at each matrix crosspoint is much higher end and costly;)

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Re: live sound - mono or stereo?

Postby Hugh Robjohns » Mon Dec 03, 2012 4:05 pm

seablade wrote:...Or Pseudo stereo, in this case...

There is nothing 'pseudo' about creating stereo images using time delays between channels. It is a perfectly valid and proven technique which just happens to have a different set of advantages and disadvantges to the more familiar level-difference technique. The results at the ear, and the way the brain interprets the signals are very similar.

...you need to make sure that you don't sum these signals to mono in the matrix for the various fill locations.

Very good point. However if using one of the more advanced digital consoles, the time-delay panning can be performed on the group outputs with the matrix feeds taken pre-pan. It is do-able given the appropriate technology -- although admittedly a lot more of a faff in most consoles! ;)

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Re: live sound - mono or stereo?

Postby seablade » Mon Dec 03, 2012 4:41 pm

Hugh Robjohns wrote:
There is nothing 'pseudo' about creating stereo images using time delays between channels. It is a perfectly valid and proven technique which just happens to have a different set of advantages and disadvantges to the more familiar level-difference technique. The results at the ear, and the way the brain interprets the signals are very similar.

Correct, my intention wasn't to say that it was any worse of a stereo image, just a different one. Both acoustic shadows and time delays can provide stereo image, even better if you can do both together, and even frequency based shadowing to simulate the shadowing that happens via our pinnae even play into this. Of course all these combine to form HRTF, which essentially mimics how we hear sounds and determine where they come from obviously.


Very good point. However if using one of the more advanced digital consoles, the time-delay panning can be performed on the group outputs with the matrix feeds taken pre-pan. It is do-able given the appropriate technology -- although admittedly a lot more of a faff in most consoles! ;)

hugh

True but that makes it very difficult to differentiate your panning between instruments as well as you are limited to your pairs of groups. Again all different ways to accomplish something is all, each with their own benefit or detraction.

I will also say that I am in the midst of setting up a new system for my primary space and may give the delay based panning a run in it as it is appropriate for FOH in this space, so my point isn't to detract from it. But I will also be doing a split broadcast mix and FOH mix, with a capable digital console at FOH anyways, and since the fill system is likely to be stereo as it is only front fills I don't have to worry as much about possible detractions as I would in a straight theatrical setting for instance:) But I am designing said system myself and will be in charge of overseeing all mixers on it anyways so I have a bit more flexibility in making sure only techniques I know work are used:)

By the way one other possible downside of this method has to do with arrival times, it is possible in the wrong situations you can have areas of your audience that actually don't image the sound at all, but instead hear your speakers as two separate entities, which is far worse than hearing in mono, but that depends on arrival times of the sounds and delays added in taking it past the window where we here it as a singular source.

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Re: live sound - mono or stereo?

Postby p.dakin » Mon Dec 03, 2012 5:30 pm

I system tech (design and setup up the speaker system for the band's engineer)for a large majority of my working career, and I'd say about 80-90% of major engineers mix in stereo and a stereo system MUST be supplied. However as mentioned, panning is subtle around 50-60% at the max reaches.
However there are ways to give quite a high percentage of the audience members a "stereo-mix" experience.

For allot of the shows I work on, I have traditional L/R speakers (just slightly more of them :D), however I then have in-fills, center-fills, near out-fills, far out-fills and then delays on big big shows.

With all these extra fills, you have a large percentage of the audience towards the front of the venue hearing only the main L or R speakers, but also hearing a partial element of one of the multiple other fill speakers. If one of these partial fill speakers is alternative to the main hang that they can hear, then the audience member will get a subtle stereo image. Its not a traditional stereo image with elements centred, however it is stereo as some thing are over to one side and others are to the other and panning FX move.
Its not perfect by any means, and if done badly sounds 100 times worse, than if you just had mono everywhere. It doesn't always work depending on the venue and acoustics.. but I always give it a shot.

Once you move further away from the "fill" speakers coverage, you should (hopefully) come under the coverage of both the major L/R elements and should hopefully then receive a form of stereo mix again.
Obviously depending on your location, will determine what sort of stereo image you hear, however as long as the stereo mix is being used to evoke space and movement, rather than mearly hard panning as "the instrument outputs stereo.." then the audience should hear every instrument. Its not perfect and if the mix was mono, then everyone would hear a similar sound/mix, however as mentioned some instruments can only really be appreciated in stereo.
So I try to aim to deliver a form of stereo, possible at the detriment of a perfect "mix/balance" to deliver a audio experience that's exciting; dynamic and has movement.

However after the 2nd pint, 99% of audience would be hard pressed to even name the lead guitarist, let alone tell you which side of the PA he was panned!

As long as you can hear the vocal.. my job is basically achieved!

I saw Radiohead many years ago and was off to one side, Johhny Greenwood's (guitarist) big solo came up (he was on opposite side to me).. it was a little too quite for my liking, however I knew it was coming from the opposite side to me and I could easily hear it.. I was hearing a stereo mix, even off to one side, but as I was too far to one side his solo was too quiet. I moved into middle of venue... Mix was perfect.

So that's really the crux of the argument. What do you prefer, a mix that's possibly duller (less exciting, not dull in EQ terms), static, possibly congested but balanced or a mix that's less congested and moves around the venue?
There's no real right answer as different people like different things and you can't please everyone.. that's why cheap seats where invent! :headbang:
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Re: live sound - mono or stereo?

Postby damoore » Mon Dec 03, 2012 6:01 pm

seablade wrote:
damoore wrote:A Leslie sounds better in stereo. You don't really care about "image" - what matters is the motion, which you lose entirely in mono. I saw Jimmy Smith on his last tour playing through two Leslie's mic'd at 180 degrees and in mono in the FOH you couldn't hear the Leslie effect at all! I could see him hitting the half moon switch but any sense of change of speed was totally absent.

There is no difference between 'image' and 'motion' in this context, they are the same thing.

In a system not capable of stereo, you won't have motion, it will sound like it is getting louder and softer only, half the time not hearing it at all pretty much.

Seablade

Not at all - you don't have to mix to a position - everything can remain centered - so you don't have the problem with parts of the audience getting a different mix. That is the difference. Of course people well off axis probably won't hear any motion, unless its from reflections, but you are not degrading their sound compared to what they would be hearing in mono.


In this particular case they were using two mics on each Leslie (at 180 degrees) and mixing to mono so they lost most of the volume changes as well. You should only use that mic placement if you are going to run stereo. I have no idea if the Leslies were phase locked - presumably the motors will remain phase locked if you start them in the same position and make sure they remain electrically connected to each other at all times. If not, that would further reduce the effect.
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Re: live sound - mono or stereo?

Postby seablade » Mon Dec 03, 2012 6:10 pm

damoore wrote:
Not at all - you don't have to mix to a position - everything can remain centered - so you don't have the problem with parts of the audience getting a different mix. That is the difference. Of course people well off axis probably won't hear any motion, unless its from reflections, but you are not degrading their sound compared to what they would be hearing in mono.

Stereo isn't just mixing to a 'position' it also covers motion as a result, it is inherit in it. You can't have motion without movement, and to move it has to track in stereo, and image just reflects where in the stereo field you hear something at that moment. If you are using two mics on a leslie and panning them appropriately so that the sound travels then you are doing a stereo micing and should reproduce it in stereo if possible with a full stereo coverage system. Your example reflects this perfectly;)

There are many things that sound better in stereo, we as humans with two ears like the sound of stereo better than mono. A Leslie is just an example of something that doesn't translate well to mono at all.

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Re: live sound - mono or stereo?

Postby DanR » Thu Dec 13, 2012 12:08 am

As a keyboard player and soundman for my function band I always run my Mackie active rig in stereo which I suppose it automatically is being four powerered cabs.
Can't have my Korg Triton Extreme playing in mono! It's packed with fat stereo samples and would be a waste in mono.
The audience though would have to be in the 'sweet spot' to notice and doubt that many do.
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