That's exactly how my band splits our signals, too. (At least for the L1's - the B1's vary from system to system - some have a single, some a double).

3 mics go left, 3 go right. We love it.

quote:

Originally posted by Mike Early:
The difference between two towers and four as I use them is night and day ... I have never heard any cancellation ... with the four towers ... when I run the four towers and eight subs the increase in output is awesome and it goes from a DJ rig to a concert sound system and I do not hear any type of phase sound issues ... I use two towers and eight subs all the time so I know the difference between that and the four towers and eight subs...

I'm musing on a little experiment in my head, and I'm wondering if audible "phase cancellation/coloration" is most pronounced with one common signal and ONLY two sound sources (e.g.: 2 L1's)...


As Chris-at-Bose noted, pre-mixed "stereo" music does not (usually) consist of unique, distinct two channels of sound; a lot of the sound is "mixed" so that it spatially sounds like it is somewhere in between the two L & R speakers -- very little, if any, is 'panned' hard L & R. (bear with me ... I've got two thought streams running in parallel here ...)

I suspect that a whole lot of the "muddiness" of a single live acoustic source run through two L1's (behind the performer, run as dual mono) has much to do with the fact that there are THREE sound sources, not just two.

As was noted in another thread (by DanS, as I recall), there often is an apparent stereo effect when you have two live performers using one L1 ... conjecture is that the weaker "live" sound gets to the ears before the amplified sound, and that first-arriving sound from the performers is what generates the stereo effect in the brain.

However, if you add another (3rd), nearly identical amplified sound arriving with a slightly different time and phase from the other amplified sound (because it is coming from a different physical position), then the ears/brain get "confused" as to what is coming from where ... especially because the differences in arrival-time/phase/amplitude will vary with frequency (pitch) of the sound.

Now ... back to Mike's setup with FOUR sound sources -- and none of them "live".

I have no doubts there are phase cancellations going on all over the place -- but because there are FOUR distinct sources, it is not at all likely that all four sources will consistently "cancel" each other out in any one physical location -- even outdoors (indoors you get to add in all the wall, floor, and maybe ceiling reflections, too! ... which makes any "standing pattern of cancellation" even less likely).

Picture, if you will, two stones thrown separately into a still pond. (This is the classic physical analogy for phase cancellation.) You can see in the spreading circles of waves places where the waves "interfere" with each other, resulting in some spots on the surface which are different than most of the rest of the surface. Those "spots of interference" have a pattern which is quite visible, distinct, and predictable. That is, a casual observer will be able to see a number of places where the waves are consistently higher -- or lower -- than they are elsewhere on the pond's surface.

However, if you throw in 4 stones, well .... while the resulting "interference" may be theoretically predictable, there will be little, if any, apparent pattern of that "interference". That is, you will see a delightfully complex pattern of waves, but you would be hard-pressed to find any spot on the surface where the waves are consistently higher or lower than they are elsewhere on the surface.

When you add in the fact that the "stereo" music is driving somewhat different (but not too different) signals to each pair of L1's -- well, maybe it isn't so suprising that it "sounds good", not bad.

So, while the "dreaded dual mono" may still be something to avoid for clarity of sound -- particularly with live acoustic sources (e.g.: voice or acoustic instrument) -- more than two might not be so bad.

Chris hows that test coming along?

Mike,

Just curious, do you remix? Add reverb, delay or other effects?

This is a very interesting thread, thanks to all for sharing.

Oldghm

No I run flat out of my mixer with no added effects.

Hey Mike,
Did you use any PackLites with your B1's?

I did a demo with them and they are great but since I own 4 towers I simply use the 3rd PS1 to power the 4 extra subs when I use 2 towers and 8 subs.

I`m really interested in trying something like this. How do you think 1 L1 and 6 or 8 B1s on each side would compare with your set up?

I use 2 L1's and 8 subs often and it sounds great!

Is garyj talking more that 4 B1s per L1?

Would there be a benifit in increasing the ratio of L1s to B1s to 1/6 or 1/8? I think that is what garyj is asking.

Anyone done that?

Yes, I`m interested in the "optimum" ratio of subs to L1s for bigger halls to outdoor situations. Actually, I was talking about going with what used to be called the extended bass package on each side (Pre Packlite). Per side, that would be an L1 B2 system plus an extra power stand with 6 additonal subs (just to use all the available power. This is in contast to the 2L1s + 4 subs per side that Mike Early used above which also uses all the available power...PEACE

quote:

Originally posted by garyj:
Yes, I`m interested in the "optimum" ratio of subs to L1s for bigger halls to outdoor situations. Actually, I was talking about going with what used to be called the extended bass package on each side (Pre Packlite). Per side, that would be an L1 B2 system plus an extra power stand with 6 additonal subs (just to use all the available power. This is in contast to the 2L1s + 4 subs per side that Mike Early used above which also uses all the available power...PEACE

Three considerations:

1) What ratio would you use with conventional speakers between the bass amps' wattage and the combined mid-high amps? 1:1? 2:1? 3:1? bass:upper So, keep in mind that each pair of B1's is 250 watts, while a single L1 is 500 watts. Thus 4 B1's gives a 1:1 ratio, based on pure amp wattage.

2) The dispersion (spread of the sound field) is different between the L1 and the B1's; the L1 has less "drop off" with distance than the B1's. So, outdoors particularly, you may want more at the bottom end to balance the L1 than you might need with conventional speakers.

3) It's always easier to "turn down the bass" than it is to scramble for a way to get more.

Dan,

Thanks for your comments. I don`t really know anything about conventional setups. Seems like 1:1 is reasonable(and that`s why they came out with the Pack Lite?). I`ll just have to try some experimental setups one day and see what works best?

Listening test report:

On Wednesday June 7 a group of us-at-Bose set up in our performance lab a stereo system of 4 L1s and 8 B1s in the same arrangement shown in the photo by Mike Early at the beginning of this thread. We listened to four variants of this system without moving any speakers, just by turning things off or re-wiring inputs to the PS1s.

• 1) Mike’s full setup with all 4 L1s and all 8 B1s, called here “4+8”. Left channel is fed to the two left PS1s, right channel to the two right PS1s. All gains equal and preset 00. (It is important to match levels on all 4 L1s. We did this by listening to two at a time, standing equidistant from the pair and tweaking levels in mono until the image was centered. First we did this with the left two, then the inner left and right ones, then the right two. Once they were all matched this way, we turned them all on for the tests.)
  
• 2) Turning off the outer two L1s and their double bass packages gave a standard DJ stereo setup of two double-bass line arrays, called here “2+4”.
  
• 3) A quad bass DJ stereo setup with the same inner two line arrays, using the outer two PS1s to drive only the extra pairs of B1s, called here “2+8”. You would get the same result if you drove the extra B1s with Packlites instead.
  
• 4) One double-bass package alone, called here “1+2”.

With these four arrangements, we did two separate listening experiments, one for stereo pre-recorded material and one for live vocals from a microphone. We were mostly listening for any vocal interference problems that might come from distributing signals to multiple speakers. Here is what we heard.

1.) Compared pre-recorded stereo material on 2+4 vs. 2+8 vs. 4+8

• 2+4 -- Very good sound quality, as expected. Also very good if we try preset 57 here, as many DJs do. Now that we’re concentrating on vocal interference, we notice that all the vocals are compromised a little by this effect as soon as we move off the centerline. It’s less significant once we get out to the side. This seems to be a normal problem with all stereo loudspeakers that we’ve taken for granted all along. It’s one reason stereo doesn’t sound as good when you’re not in the middle.
  
• 2+8 -- Essentially the same results as 2+4, but of course it can reach louder levels than the 2+4 on bass-heavy material.
  
• 4+8 -- Mike is right to praise this system. It sounds tonally very good and is capable of producing a truly ferocious amount of clean sound. We do hear some interference in the vocals across the whole front, and it’s spread a little wider than with the 2+4. The level difference between out front and to the side was a little more than the 2+4. None of these differences prevented us from really enjoying the over all sound.

2.) Compared live microphone vocals on 4+8 vs. 2+4 vs. 1+2

• 4+8 -- sounds like PA
  
• 2+4 -- sounds like PA
  
• 1+2 -- sounds like it’s alive! A living person with a mighty voice. This reminds us of why we have always encouraged live performers to each have their own single line array.

----------------------------------------

In my previous post, I was excited by the anticipation of learning something new, and now we have. Here are our conclusions:

• The minor degradation of midrange interference off the centerline probably cannot be avoided when recorded stereo material is played on any speakers. This is one of the compromises of the stereo format itself.
  
• The interference of 4 L1s playing stereo is not much more significant than two L1s, so it is fine to use four in stereo when needed to produce enough level for recorded music.
  
• For live sources, the interference of multiple speakers can be completely avoided by not distributing any source to more than one speaker.
  
• Exception: true "distributed systems". To cover a single very wide or irregular area, it may be necessary to space your L1s, using a 20-50 foot spacing between them (6-15m). In the installed sound world, this is known as a distributed system. In this case, you should send the same signals to all the widely spaced L1s. If the source is stereo, it is common practice to combine L&R for distribution in such a system.

These conclusions clear up the apparent discrepancy between Mike’s good results and our suggestion that sources not be distributed. We stand by our suggestion for live sources, but there is no way to prevent interference with recorded stereo, so four speakers vs. two is not a critical issue in that case. We are happy to have people use this 4+8 arrangement for pre-recorded stereo in cases where you need more sound than 2+4 or 2+8 can provide.

Thanks very much for discovering and promoting this, Mike. It goes beyond what we thought the system could do. This is a beautiful example of the fact that the forum benefits Bose as well as our customers.

Chris
[8/2/06: added exception for distributed systems]

This message has been edited. Last edited by: Chris-at-Bose,

Thank you Chris! (and to all the others at-Bose) who participated.

I really appreciate the time you put into investigating and clarifying this for us.

OK, so when I switch to backing tracks, I'll need 3 units. Left and Right for the recorded music and center for the Live voice.

Seriously, this is great info that will be referred to often, I suspect ST has already listed this in the Users' guide, thanks.

Oldghm

What service by Chris-at-Bose!!!!!!!!!!

And extremely interesting even to the non-DJs, I'm so happy to have finally noticed and read thru this thread (after a few horrible days in Harmony Central).

Thanks Chris & Mike!

This message has been edited. Last edited by: Drumr,

Many thanks as others have mentioned to the BOSE staff for testing this setup. It's great that you are willing to test these configurations for us. It's great that you have confirmed Mikes findings.

I never did get time to test this myself, so I am very happy to see the test from Chris. I'm sure he was much more meticulous than I would have been too. I don't think I'll ever have an occasion to need that much reinforcement for pre-recorded music, but it's good to know there's an option. There are so many variables in the environment that it's amazing we can get the good sound we do.

My thanks goes out to Chris at Bose. Not only did he and the Bose staff go through extensive testing on my 8 x 4 Bose PAS configuration, Chris went beyond that and called me. We talked for almost an hour. I have been a DJ for 15 years and always have had the good fortune of booking large events and have always needed more than two speakers on a stick.
In over 1,100 events I've gained an ear for good sound and bad. I have had speaker configurations that produced cancellation and weird stuff. But when I fired up the 4 towers and 8 subs for the first time I knew I had something great.
I have since DJ'd many events with this large set up and it is simply a wall of sound. On June 21st, I will be DJing a outdoor Country Idol Contest for 1500 people and this good news that Chris has delivered, has not only confirmed that my ears are still working, but most importantly, my $9,000 investment was well spent. Without a doubt, this Bose PAS system has turned out to be the very best I have ever owned for many different reasons. Intense sound, weight, image, and flexability. If you are a DJ and you do not own this system and you do not DJ in my area . . . go get it!