Speaking of LF phase cancellation

[Dogoth]

I had an interesting theory sent my way recently. I wanted to run the validity of it by the folks here and see what you think.

 

It pertains to using both a direct and a mic'd speaker of a bass cab. I always thought it was superfluous in most cases but could see a case where FX or overdrive (natural compression) might be desirable in the mix.

 

The theory that was put forth was that by inverting the polarity of this mic (probably with a short delay to time align it with the FOH speakers), you could in effect cancel out the sound of the bass cab in the house thereby having a clean direct signal to manipulate as desired. Wouldn't this just wreak havoc with your own direct signal as well (assuming it is polarity correct)? Has anyone ever heard of this technique? I don't mix FOH often but given the chance I might experiment.

 

Let me know what you think (is it a waste of time?).

 

thanks

[Dookietwo]

 

I had an interesting theory sent my way recently. I wanted to run the validity of it by the folks here and see what you think. It pertains to using both a direct and a mic'd speaker of a bass cab. I always thought it was superfluous in most cases but could see a case where FX or overdrive (natural compression) might be desirable in the mix. The theory that was put forth was that by inverting the polarity of this mic (probably with a short delay to time align it with the FOH speakers), you could in effect cancel out the sound of the bass cab in the house thereby having a clean direct signal to manipulate as desired. Wouldn't this just wreak havoc with your own direct signal as well (assuming it is polarity correct)? Has anyone ever heard of this technique? I don't mix FOH often but given the chance I might experiment. Let me know what you think (is it a waste of time?). You could in certain areas lower the bass coming from stage in relation to bass coming from the subs. You will find they will both cancel. I believe you will also find it will give the bass player on stage a lot of problems as well. Its better to get the subs and the bass players rig IN alignment then out. When the bass player has a loud rig on stage that is big enough to compete with the sub / full range system I always first check the polarity between the subs and stage rig. Reverse the polarity and ask the bass player which sounds better to him/her. More often than not when they say it sounds best it also combines better in the room. (Think smaller rooms, 150-400 or so people rooms) If myself and the bass player can hear no difference it could mean the subs and bass gig could be 90 or 270 degress out in are listen areas. If this is the case I sometimes will add 3ms or so to the channel and try the polarity switch again. thanks

 

 

 

You could in certain areas lower the bass coming from stage in relation to bass coming from the subs. You will find they will both cancel. I believe you will also find it will give the bass player on stage a lot of problems as well. Its better to get the subs and the bass players rig IN alignment then out.

When the bass player has a loud rig on stage that is big enough to compete with the sub / full range system I always first check the polarity between the subs and stage rig. Reverse the polarity of the incoming signal and ask the bass player which sounds better to him/her. More often than not when they say it sounds best it also combines better in the room. (Think smaller rooms, 150-400 or so people rooms)

If myself and the bass player can hear no difference it could mean the subs and bass gig could be 90 or 270 degress out in are listen areas. If this is the case I sometimes will add 3ms or so to the channel and try the polarity switch again.

The location will be a moving target for your bass cancelation and of course the Neg phase from the Microphone put through the FOH speakers to cancel the bass players rig will also cancel the Positive signal coming from the Direct Box. I find that when the bass players rig and the sub system are in phase it gives the best sound through out the room and the best sound for the player. When the size of the room is such as it can be noted.

 

Dookietwo

[dboomer]

Forget the theory ... it's very complicated and mostly not correct the way it was stated.

 

As always (when faced with a polarity switch) ... push the button. If it sounds better then leave it, if it's worse, switch it back. Most of the time it will make very little is any difference.

[agedhorse]

Another "trick" that has just a little validity amongst a lot of bad stuff.

[Dogoth]

Thanks for your response.

 

I pretty much thought it was a usless idea (probably apt to do more harm than good) but I was told about it by a seasoned engineer for a national act and didn't want to say "that sounds like BS to me" at the time (this kind of response tends to be aproductive :-). I could see where you might just want to cancel some of the bass off stage by doing this (we recently had a guy who was playing through TWO Ampeg VSTs and still wanted bass in the dual 15" the side fills - it was insane).

 

I couldn't however see how it could work with an in phase DI in the mix as well. I'm not afraid to flip phase occasionaly to see if it sounds better (I do this (plus a lot of HPF) with drum OHs occasonaly as it can cancel the LF bleed). It's easy enough to flip it back if it doesn't work.