A question that probably has an answer that is way beyond my scope of understanding:

[Ryan.]

I've been trying to do a lot of reading on sound and all that from the links you guys give me and ones I can find on my own.

 

One thing about my show the other night has been bugging me. I could not for the life of me get the kick to sound good. But a few months ago with the same set up I made it sound great.

 

The ONLY thing that I did differently (now that I think about it) is I had the subs pointed across the dance floor.

 

I've read a little about how you can have speakers cancelling each other out? Is this possibly what happened?

 

Last time I had a nice hard kick to the chest bass drum, not over powering, but you could feel it in the dance beat, and this time it was just a wimpy woof.

 

Any thoughts?

[Coaster]

 

I had the subs pointed across the dance floor.

 

 

um, really? what? huh?

 

how about some information.

[Ryan.]

Hahah, sorry. That was vague I guess.

 

Well I told my guys to set up the mains so they crossed across the dance floor. (So they weren't pointed straight at the back wall to avoid the slap back? )

 

Anyway, they set the subs crossed too, which I've never done before, and since that was really the only thing I was doing different, I thought it might be the answer.

 

Hell, I dunno.

[bnelly428]

yes unless you changed the polarity of one of the subs there could be a good amount of cancellation.

 

not sure what you mean by crossed, but most speakers have an dispersion angle (correct term) of >65 70 degrees. So you can turn the speakers in a little but dont need to a great deal. IMO

[Ryan.]

The line of sight of the speakers was definitely crossed at a 90 degree angle.

 

Thats funny that you mention polarity, because as the show it was the first time I even noticed the switch controlling polarity. I didn't do use it though.

[kmart]

One thing to keep in mind is that even if the PA was set exactly the same way, a change in heads/tuning of the kick drum, different beater in the pedal, etc. by the drummer could all have an impact as well.

 

Exactly the same is only so when EVERYTHING is exactly the same.

[dennis a]

 

most speakers have an dispersion angle (correct term) of >65 70 degrees. So you can turn the speakers in a little but dont need to a great deal. IMO

 

A single sub has a "dispersion angle" of 360*....angling it in a bit will do very little.

 

Dennis

[modulusman]

Try changing the polarity switch on one of the subs while music or the kick drum is being played. If it is louder then you got it right. This could change every time you set-up your gear.

[Ryan.]

 

One thing to keep in mind is that even if the PA was set exactly the same way, a change in heads/tuning of the kick drum, different beater in the pedal, etc. by the drummer could all have an impact as well. Exactly the same is only so when EVERYTHING is exactly the same.

 

 

I thought about that, but even then I would think I'd at least be able to EQ those types of changes for the better, but who knows... I guess try, try again.

[Ryan.]

Changing the polarity on one sub doesn't affect the top standing on it?

[Coaster]

dont point subs at each other. put down the bong.

[Craig Vecchione]

 

Changing the polarity on one sub doesn't affect the top standing on it?

 

 

What sub, what top, what amps, what crossover, and where is the polarity swtich?

[Ryan.]

QSC 153s over 181s. Active.

 

Polarity switch is on the sub itself.

[Ryan.]

I don't smoke pot!

[dennis a]

 

Changing the polarity on one sub doesn't affect the top standing on it?

 

Changing the polarity of a sub will affect the phase relationship between it and the mid/hi cabinet sitting on top of it....and probably the mid/hi on the other side of the stage....and probably the sub on the other side of the stage...

[Coaster]

 

I don't smoke pot!

 

 

that may be the problem:confused:

[Ryan.]

 

that may be the problem:confused:

 

 

Most likely. Its lonely being a drug free musician.

[Ryan.]

 

Polarity switch is on the back of both subs

[Craig Vecchione]

 

Changing the polarity of a sub will affect the phase relationship between it and the mid/hi cabinet sitting on top of it....and probably the mid/hi on the other side of the stage....and probably the sub on the other side of the stage...

 

 

 

Which may or may not be a bad thing, depending on the room and how you've set up.

[Ryan.]

 

Which may or may not be a bad thing, depending on the room and how you've set up.

 

 

So basically though, just don't point the subs across eachother? And if I'm still having issues, play with the polarity settings to try and fix?

[Craig Vecchione]

Polarity switch is on the back of both subs

 

Does it affect the signal being passed through to the midhigh? My assumption is 'no', but as usual, "it depends".

[Ryan.]

So just for a little learning lesson here... if it was the crossing of the subs that caused the issue, what is the reason?

 

The sound waves crash into each other or something? Cross-mojo-lation?

 

Whats the science behind it? I will accept a lmgtfy answer...

[Coaster]

phase

[Ryan.]

Ha, I just googled phase cancellation. But that didn't get me much. Any better keywords?

[Craig Vecchione]

 

So just for a little learning lesson here... if it was the crossing of the subs that caused the issue, what is the reason? The sound waves crash into each other or something? Cross-mojo-lation? Whats the science behind it? I will accept a lmgtfy answer...

 

 

Identical sound waves directed at each other in the same phase will cancel at the midpoint of their source. What you'll hear at that point is lower volume. Move in either direction, and volume will increase as you hear one speaker or the other as you approach that speaker.

 

Identical sound waves directed at each other but 180 degrees out of phase will reinforce each other. Volume will be relatively even as you move from one speaker to the other.