Anybody ever do this and if not, why not?

Hey. IIRC, "they" say that the soundwaves will crash into each other in the middle and cancel each other out and you will become invisible. Something like that. Don't know why. And don't know why guitarists don't care about this phenom; they all seem to want to rock stereo rigs. My last pedal is in stereo, going into a pair of MB210s, but what does that matter when they are stacked? I may try this too. At least at a rehearsal.

If it turns you invisible, please post vid clips. Thanks.

--Bomb

 

it works better for guitar because their wavelengths are shorter and don't bump into each other nearly as bad as bass freqs. in order for it to work optimally, you have to have as much space between them as your lowest wavelength, which on a bass tuned to E, is something like 28 ft. that's why pa subs are usually clustered or there is only one...to prevent that from happening. i know some bassists do it and like it, but i figure why tempt fate.

 

Bomb has a point. If you separate bass speakers more than a quarter wavelength (two feet or so), their sound waves interfere with each other and cause nodes of higher and lower SPL. It looks kinda like this. Note the positions of the speakers together (Fig. 38) and then, say, 26 feet apart (Fig. 44). The diagrams are for 50 hz and 100 hz.

 

I did that ALL the time, not so much now. And to my and the bands ears it sounded great! No canceling. I had a funky rig, a Dynaco ST-70 stereo tube power amp (still have) and a Dynaco stereo pre, two 1x 15 altec cabs set on each side of the drummer. I ran a Y cord into the pre, one side straight, other with a MXR phase 90! MAN once THAT ALL got going it was STAY AWAY FROM THE BROWN ACID TIME! Maybe we didn't notice the canceling BECAUSE OF THE BROWN ACID?

 

Well, with indoor venues, you have tons of boundaries, so reflections probably fill in the gaps.

 

That's the issue I had years ago with my Eden Metro Combo (behind me) and the MBX210 wedge shaped cab in front of me.

Actually it was advertised to be used like that by Eden at the time.

 

Is that why the sound man never puts the bass into both sides of the PA system or the monitors on the other side of the stage? Oh wait....

 

Not possible.
This applet shows what happens when you have two sources, with every possible combination of distance, frequency etc.
http://www.falstad.com/wavebox/

The best result is seen when you click the 'setup' to single sources, be it point, pinhole, line or slit. You see the resulting red and green representations of the wave's positive/negative phase as uniform in the listening area. With any of the multiple source options things get all muddled up. Moving the frequency slider to the left, for lower, shows what happens to the lows when you have cabs separated. Moving it to the right, for higher frequencies, shows what happens to the mids and highs when drivers are mounted side by side in the same cab.

 

listen, if they're smart, they either use only one sub, cluster the subs in one spot, or they separate them out far enough where their lowest wavelengths won't cause comb filtering. and if they're smart, they'll roll the lowest freqs off the bass in the monitors.

 

To keep stage volume down, my bass runs through the monitor cabs in addition to my backline cab.

I can say from experience that with this setup, my "sound" changes radically if I move even a few feet in any direction. And it's NOT just the difference in cabs.

 

Also to note: putting the same signal though left and right speakers isn't stereo, stereo stuff is seperate for each side.

 

They do it (put subs on both sides of the stage - I know you're being facetious) because not many venues can accommodate centered subs. They just live with the fact that some people in the audience are not going to hear much bass, and some are going to hear too much.

 

A question for Bill F.: If you center two direct-radiating subs (in this case, JBL PRX518S) is it beneficial to arrange them facing in toward each other, similar to the way you recommend doing it with horn-loaded subs?

 

clustering to one side when you can't center them will work pretty well, too, and certainly better than splitting them when you don't have the room.

 

Almost right...

Exactly right.

Guitar wavelengths are shorter/smaller, so when they interfere, they only make the guitar players brain invisible.

Randy

 

I've done this, but in the opposite circumstance; where bass volume on stage was so low, and the stage so wide, that the guitarist couldn't hear the bass well enough. So the loudest cab was behind me; the other cab was behind the guitarist.

Without PA support, I wouldn't want to do this, for reasons already mentioned.

 

I believe what "they" are talking about here is a phenomenom called "comb filtering". This is one of the advantages of line array pa systems vs. clusters in concert audio.

 

BROWN ACID?

 

+1 I'll have to try this at our next house concert, party. We were having trouble with subs. So center or one side, yes?