I'm convinced that if I really ever NEEDED to have a stereo system again, I will buy a second Bose PAS. It's just that good and THAT easy.
As it is ..... most of my venues do not benifit from the stereo field, and since I monitor through the kb speakers (in stereo)at least I always hear the stereo signal in my face. In the immediate area near the stage, stereo DOES enhance some things, but so far - having the wide dispersion, clear sound and terrific range of the Bose tower has been a superior choice for me.

Next time I am in a situation that can "show off" the stereo spread, I might try to see how the system sounds by using my JBL/Sub setup as the other half of the field. It'll consist of the Roland Sub and 2 stacked EONg2 10s on top. That'll make a small tower on the other side. Hmmmmmm......

(I know it's just more "fluff" .... I definatly don't need it yet)

Not to convince you otherwise or anything, but the benefit of stereo isn't just what comes out of your stage monitors but what the audience hears. The stereo audio reduces phase cancellation that is inherent with all summed audio outputs, and it forces separate portions of your audio to reflect within the room from various angles towards the audience. I find that stereo adds a great amount clarity to the overall sound because of the phase reduction.

The only way to test and prove this to yourself is to run a stereo PA system in a room and try playing music from a CD player and/or your keyboard through it both in mono and stereo and see if it makes a difference to your ears when sitting where the audience sits.

Hey guys,

I thought this was a nice article on the subject.

http://www.mcsquared.com/mono-stereo.htm

mike

Uncle Dave,

How well do you think the PAS would work in a 250 person Church? I'm not thinking of music here but as a voice PA for the preacher. In order to get acceptable volume levels from the pastor we have to sit right on the edge of feedback. Also the people that are hard of hearing say they can hear but not understand. Do you think it would add any clarity over a conventional PA?

Tom

Yes it was - thanks for posting it. While the author makes a strong argument for mono in this article, he/she leaves out any consideration of phase cancellation in summed audio outputs from stereo instruments like keyboards. They also don't discuss something I call the "mono myth" - no band is truly able to perform in mono unless they are all vertically piled on one another. Just by the natural arrangement of the instruments on stage, be it a small band or an orchestra and especially the latter, there is a natural stereo audio spread. The acoustics of the room then reflect those sounds and blend them.

We all have two ears, not to belittle anyone with trouble hearing, and the only natural way for us to hear the exact same thing in both ears is for a single sound source to be coming from straight ahead, directly overhead, or directly behind the listener. Otherwise we listen for two distinctly different sounds, which is probably why our ears are on either side of our head instead of being planted on the front of our heads like our eyes. So I would argue that stereo sound is the most natural way for us to listen to music because it's the most natural way for it to be presented. As a one-man-band I'm aware that I am being compared to traditional bands when I perform, so I want the most natural and comparable sound possible. My keyboard sounds best in stereo so that's the way I've chosen to amplify it - if my competition chooses to perform in mono (they often do) then so much the better for me.

Hey Jim,

What exactly do you loose when there is phase cancellation due to summing the outputs of stereo instruments? I know you loose direction or placement or soundstage along with some effects but does the original sound source change? In other words, you play a grand piano sound, the original signal is stereo, and if you were to sum the stereo outputs, it no longer sounds like a piano or sounds like a very sick piano or whatever?

This whole mono-stereo thing can really perplex me (if I let it). I had a whole slew of questions back when Roel was helping Terry out with is mono-stereo recording issues. But I held back...Tech-talk doesn't always appear to be popular here.

If you've got the time to explain, I'll definitely listen.

mike

The Yamaha P120 and P90 "stage piano" do not have any mono piano samples, so if you don't plug it into a true stereo system live you get a rather thin, edgy, attack only type sound in mono. It's a dilema
So I am thinking thin mono Bose PAS won't be suitable and that I may have to go with a pair of Bose 802s or a pair of Italian FBT 10" powered cabinets to keep the piano in stereo and avoid the phase cancelation that stereo piano samples get when put through mono.


[This message has been edited by rintincop (edited 02-09-2004).]

In keyboards, the most common side-effect of phase cancellation is when you perceive some notes on your keyboard to be louder than others or if you hear an unintended chorusing or flanging effect.

In layman's terms, phase-cancellation means that when a sound is played along with an inverted phase of itself, the two signals cancel each other out. All audio signals are airwaves that move up and down, so by adding a slight delay to a signal, you change when the up/down movement happens. If the "up" hits at the same time as the "down" does of the same sound, the result is silence. This principle is what is used in the noise-cancelling headphones by Bose and others: a microphone picks up the ambient sound and then combines that sound with a phase-reversed copy of itself in the actual headphone sound so that you hear no ambient sound at all. Some companies are even trying to design new car mufflers based on this principal. Here's a link to another non-technical explanation with diagrams.

We often hear audio phasing, sometimes called chorusing or flanging, used as an audio effect when a small amount of delayed signal is added back with the original signal. I'm sure you've heard recordings that used a flanger where the sound seems to thin until it nearly disappears and then comes back (if you haven't then listen to the bridge in the Doobie Brothers song "Listen To The Music" where the singer says "like a lazy flowing river"). As the signal gets closest to optimum cancellation, the sound reduces in volume and sounds like it's being "choked off" only to return as the phase-cancellation passes.

A phase inversion occurs whenever a minutely delayed copy of a sound is recombined with it's original sound. This can happen in keyboards when the left/right stereo signals are combined into mono. It's never perfect cancellation (which would result in silence), but it's usually pretty noticible... certain notes on the keyboard won't have their usual full tone while others will seem to jump out.

Hope that helps...

[This message has been edited by The Pro (edited 02-09-2004).]

Thanks Pro!

I've got comments but they'll have to wait (work calls).

mike

I think the PAS will shine in a church for voice ! It's so clear and present, in all areas of the room.
Remember, I used to be a big supporter of stereo, but this system is changing things. The benfits outweigh the negitives in almost every venue so far. It all depends on placement. I can definatly see how a second tower could be a nice addition, but not that often.

Greetings! I'm new here and had a long post that I was going to enter under a new topic, but this looks like a good place for it so I'll drop it in:

Stereo patches / Live Music / Mono vs. Stereo

Sorry about the long, multi-topic heading, but these issues present a dilemma for keyboard players. For the sake of simplifying, I’ll make some generalizations. If this has already been hashed over I apologize – I haven’t seen the thread.

The conventional wisdom among live sound professionals is that, generally, for live music, a mono system sounds better than stereo to most people in the audience. This is mainly due to fact that many people are located much closer to one speaker bank than the other. Depending on how much closer to one speaker, the sound they hear doesn’t have the desired imaging, seems to lack “information” and may be noticeably out of phase. For these people, a mono signal would sound better, ideally with the speakers arranged in a mono stack in the center of the stage. A mono system would not have to be a single centrally located stack to sound better, but that’s another topic and I am not too interested in it because…

I know that the stereo patches on my S90 don’t sound nearly as good in mono. When I listen to the sound through stereo monitors or headphones the sound is so wonderful and rich – that is how I would want the instrument to sound like live, only louder. Do I have to choose between mono, which will sound acceptable to everyone, or stereo that will sound great to those in the center, but poor to those not in the sweet spot?

I think there may be a way to allow the full expression of the stereo patches while avoiding many of the problems with stereo PA setups, but I am curious to hear what the rest of you think. Suppose you connect your synth to a stereo PA / two speaker system but instead of going for the usual wide separation of speakers, keep them closer together. After all, some of the most effective stereo patches on my S90 simulate what is generally a point source of sound like an EP, synth, organ or a leslie set-up . I can hear the effect of that spinning horn and a wide separation isn’t necessary and in fact sounds less like the original instrument or leslie. Wide separation is mainly important for pan effects and for imaging. Imaging is really more of a studio/recording consideration that is problematic in live shows as mentioned above.

It seems that in smaller venues where its power is sufficient a Motion Sound KP200S would be an ideal set up. You get true stereo sound from two channels. Yet the speakers are close enough together to eliminate the problems caused by separation. The amp features a control to allow you to enhance the stereo separation effect, if desired. This technology would give the listener the perception of wider separation but without the major problems of true wide separation – the sound is coming from speakers that are side by side. I have not heard the KP200S yet, but I am curious as to how good the sound is from various locations in the audience. I’m sure it sounds great in the sweet spot, on axis with the speaker, just as a PA system does. The sound pros concede that stereo sounds better than mono for the folks who are equidistant from widely separated speakers. But how does the KP200S sound as you move off axis? Any other thoughts?

Another fragment of the "what do I lose with summed mono outputs" there was a time when all you got was a chorus button (e.g. Yamaha PF10) and the basic instrument was mono. The effect was added "normal" to get one stereo channel and "inverted" to get the other. The chorus effect was very pleasant in stereo but totally disappeared in "summed mono". I dont think this happens much these days.

I'm a big fan of stereo, and sincerely believe that it sounds far superior to mono, especially at large venues. For the small jobs, though, nite clubs, etc, it realy does not make a lot of difference. I do not believe the sound of mono is quite as rich and full, however, the audience doesn't seem to know, or for that matter give a damned!

Gary

This is why the sound of the KP-200s is hard to describe - I think a lot of people have the general idea but hearing it is another matter. Once you engage the amp's stereo spatial enhancer, you alter the sound in a way known as "psychoacoustics" and the sounds seem to come from places where no speaker is. The room reflections are also altered and you hear different aspects of the sound coming from places other than the amp. However you still hear pretty much all of the sound whether you are "on-axis" or not. Remember again that when listening to a normal band it's quite difficult to get a seat that is always "on-axis" anyway, so you are nearly always in less than perfect listening circustances anyway and there is only so much you can do.

I disagree with Gary: I think stereo makes a greater difference in smaller and more intimate environments than larger ones. Most people today are used to good close-quarters stereo music, be it from their car or their TV or their bedside radio.

My Yamaha P120 and my Yamaha P90 digital pianos have only stereo piano samples, no mono piano samples. When playing through a mono sound systm, my Yamaha stereo piano sounds, and other brands too, suffer and become thin, edgy and almost all attack. This is the case for most stereo sample keyboard sounds. When the left and right samples are summed on top of each other into mono their is an out of alignment problem that causes a chorusing and phase cancelation effect.

Liam,

This may well be the case for a single instrument player or for a synth player who is playing single timbre notes. Even with a real piano, where you get some physical separation of sound, the amount of such separation is quite small, though definitely noticeable when you are close up.

The majority of people in this forum are playing Arranger keyboards, which simulate
the entire bands. When you listen to the band, hearing it from a single source sounds unrealistic They can not possibly all be in the very same spot physically. Having proper stereo separation goes a long way to adding realism to the sound of our instruments.

Regards,
Alex

Well actually it was my understanding that mono was genreally considered to sound better for full bands, not just single instruments. Do those of you who use arranger keyboards encounter any problems playing a stereo rig with with wide separation? I am really curious about the potential of the KP200s to overcome these problems. Or have you found any other effective ways to address them?

The 'ONLY' reason I have to run out stereo, is because, as a performing musician who features 'acoustic piano' playing, the top acoustic piano patches on Yamaha PSR keyboards all require a true 'stereo image' to sound decent. Going out mono results in effects phase cancellation, resuslting in a thin unacceptable acoustic piano sound. If it weren't for this, going out Mono would be fine with me for my gigs. - Scott