Fun with Phase Cancellation

[RawDepth]

I recently recorded a live band during an outdoor gig. Due to the drummer's tight setup, the only spot I could squeeze in a top snare drum mic was only a few millimeters away from the HiHat cymbals. Even though I used a super cardioid mic, the top snare track still had tons of harsh, shrilly HiHat all through it. (The bottom snare mic was no problem.) After the gig I lost almost a full night's sleep wondering how I was going to EQ out all of that offensive HH yet, preserve the attack of the snare. It finally hit me in the morning. Phase tricks, my dear Watson!

Every good soundman should know that when two like signals oppose each other and are out of phase, they cancel. All I had to do was make a duplicate of the snare track (without the snare,) and reverse the phase. Filtering out the snare was easy with a limiter because the "snare hit" peaks were high above the HiHat peaks. So, I made a copy of the track, ran the limiter plugin, hit the phase button on the mixer, and botta boom botta bing, it was goodbye HiHat.

Well, a closer listen revealed that it was still ruining the sound of the drum somewhat. (I am picky about my snare mixes.) After tweaking for a while, it sounded "okay" but, I ended up bagging the whole idea and using an expander instead, but hey, my lame invention did work.

I suppose I could keep the idea in my bag-of-tricks for something special someday. I just thought I would share my adventures with you guys.

RawDepth

 

[boingoman]

I've used that same technique when trying to clean up recordings of lectures and things. I EQ out the vocal range and reverse polarity. A good thing to know is that the amount of cancellation depends on the relative volume of the tracks. If they are the same volume, you get maximum cancellation. As you decrease the volume of one of them, the amount of cancellation goes down. With the lecture tapes I have worked with, it's often possible to get enough cancellation by varying the track's relative volumes to make the recordings much more intelligible without killing the content. I would imagine it's much trickier when working with music tracks.

 

[KamikazeKyle]

I used a similar trick while cleaning up a piece of audio.

 

[BRIEFCASEMANX]

Once I took 5 duplicate tracks of kick drum, 2 panned L and 2 panned R and one mono, and I 180 degree phase reversed the opposing tracks, and used variable phase shifter to shift the mono track +90 degrees. I EQ'ed the L tracks so that the highs were filtered out at about 5khz. I did the same with one of the R tracks but also filtered out the lows at about 150hz. Then I experimented with adding chorus to the mono track and turned the volume of the 4 tracks that were panned hard down about 6db. Added some other time based effects (flanger and phaser) to one of the hard panned pairs. I then automated each kick transient -3db on the mono track for maximum effect. I did the same thing with double tracked guitars in the mix but without the flanger and phaser, and with no automation. Each Guitar was recorded with 2 mics on the cab, a mic about 3ft back and a mic about 15ft back, so there was actually 8 tracks of guitar total, but it would work the same if there was only 4, or possible 5 like the kick. The filtering took out all unnecessary noise, and the room mics on the drum kit provided all the necessary ambience I needed when turned up loud and compressed. It turned out to be one of the best mixes I've done, but took about 20hrs!! to figure out this phase trick. Excellent!

 

[jmorris]

I record a lot of live gigs. If the drummer or soundguy isnt the type that understands that there are certian things that I need, I wont do the gig.Not worth the hassel. I have run into a number of sound guys that dont know their ass from their elbow about simple things like how to mic a kit. My last live gig was 2 1/2 hours away. I emailed the sound engineer 3 times to be sure what his setup was, his mic list for that night. When I got there, all he had for mics were beta sm57, and a kick drum mic. Oh, and a sm58 for drum overhead. He " did not like any condensors for outdoor gigs" and had the toms mic'd off about 8 inches" to get some air". Yeah, thats about all he got. So, for me everyone has to reasonable. If I need the drummer to adjust his kit a bit, I ask him to do so.It will only benifit them as a hole in the end.

 

[boingoman]

I record a lot of live gigs. If the drummer or soundguy isnt the type that understands that there are certian things that I need, I wont do the gig.Not worth the hassel. I have run into a number of sound guys that dont know their ass from their elbow about simple things like how to mic a kit. My last live gig was 2 1/2 hours away. I emailed the sound engineer 3 times to be sure what his setup was, his mic list for that night. When I got there, all he had for mics were beta sm57, and a kick drum mic. Oh, and a sm58 for drum overhead. He " did not like any condensors for outdoor gigs" and had the toms mic'd off about 8 inches" to get some air". Yeah, thats about all he got. So, for me everyone has to reasonable. If I need the drummer to adjust his kit a bit, I ask him to do so.It will only benifit them as a hole in the end.

Huh, not sure how that relates to the original topic, but I try to turn those kinds of situations into extra money, myself.

 

[Reggie]

Once I took 5 duplicate tracks of kick drum, 2 panned L and 2 panned R and one mono, and I 180 degree phase reversed the opposing tracks, and used variable phase shifter to shift the mono track +90 degrees. I EQ'ed the L tracks so that the highs were filtered out at about 5khz. I did the same with one of the R tracks but also filtered out the lows at about 150hz. Then I experimented with adding chorus to the mono track and turned the volume of the 4 tracks that were panned hard down about 6db. Added some other time based effects (flanger and phaser) to one of the hard panned pairs. Then I added the same effects to one of the tracks on the other side, only with the flanger/phaser running in the opposite phase cycle at 50% intensity. I then automated each kick transient -3db on the mono track for maximum effect. I also automated the phase of all tracks to match the phase of the mono tracks on just the transients, making concession for any phase shifts caused by the time-based effects. I did the same thing with double tracked guitars in the mix but without the flanger and phaser, and with no automation. Each Guitar was recorded with 2 mics on the cab, a mic about 3ft back and a mic about 15ft back, so there was actually 8 tracks of guitar total, but it would work the same if there was only 4, or possible 5 like the kick. The filtering took out all unnecessary noise, and the room mics on the drum kit provided all the necessary ambience I needed when turned up loud and compressed. It turned out to be one of the best mixes I've done, but took about 20hrs!! to figure out this phase trick. Excellent!

Maybe I'm not smart (or maybe you are joking?), but I don't follow this at all. Maybe you are overthinking? You shouldn't have to do all that craziness to your kick track. I can't imagine it sounding normal or even good really.

 

[SouthSIDE Glen]

I record a lot of live gigs. If the drummer or soundguy isnt the type that understands that there are certian things that I need, I wont do the gig.Not worth the hassel. I have run into a number of sound guys that dont know their ass from their elbow about simple things like how to mic a kit. My last live gig was 2 1/2 hours away. I emailed the sound engineer 3 times to be sure what his setup was, his mic list for that night. When I got there, all he had for mics were beta sm57, and a kick drum mic. Oh, and a sm58 for drum overhead. He " did not like any condensors for outdoor gigs" and had the toms mic'd off about 8 inches" to get some air". Yeah, thats about all he got. So, for me everyone has to reasonable. If I need the drummer to adjust his kit a bit, I ask him to do so.It will only benifit them as a hole in the end.

Maybe things are done differently in upstate New York than they are around here, but I have a question or two.

The main one is, what the hell are you depending on the FOH guy for your miking for? Except for splitting off of the vocal mikes and (if available) kick mic, I try to avoid any FOH mics altogether. His needs as FOH and my needs as a recorder are two entirely different things.

Also, how large of a room is this? If you're talking ampitheater or other bar, that's one thing. But on a standard club circuit stage, there's no reason whatsoever for the FOH to even mic the drums at all - except for the kick sometimes. I have yet to work with a club circuit band that has needed snare, tom or even OH mics for the live sound. To record these guys I gotta do my own miking anyway.

And BTW, for live recording, a stereo X/Y or ORTF rig in front of the kit and facing back and away from the rest of the sound sources, accompanied by a kick mic, and the drums are done and sound great.

G.

 

[jmorris]

Glen, here's the deal. First I agree that micing in a club other than vocals,keys is fruitless.Non the less bands do it and insist on it in most cases. The last gig I mentioned was a large outdoor gig. After emails and a review of his mic list ( sm57's on gtr,sm58 vocals,sm81's for and condenser appication ie. overheads,hi hat and I believe a beat52 for kick) I said that would be fine. Not optimun, but then again Im not bringing my U87's to a live gig where my fee is $599.00. My option at that point is to get into an argument with the guy,this a guy the band has hired, about how to mic and what application of mic's. For me,not smart. I explained the situation and my concerns to the band. They said do the best I can. I was not into driving back home 2 1/2 hours with nothing. My experience with sound guys is most have not a clue about recording. IMO most cant even get a decent FOH sound. But, most people hear with their eyes and if the guy has an imnpressive rig with big cabnits and a board with lots of cool looking faders,people just seem to think he know what there talking about. In this case,everthing was mic'd. It was a party band with horns.A very large outdoor event,maybe 5000 people. I have a 150' splitter snake,he gets half, and I gets half. Totally clean signal.There is no reason at all to bring a totally seperate set of mic's to get the job done as I know you'll agree.

 

[jmorris]

Huh, not sure how that relates to the original topic, but I try to turn those kinds of situations into extra money, myself.

My point was ( at least I think it's related to this thread) if the situation isnt right, correct it rather than fix it in the mix laster. Like the snare micing issue I think Rawdepth mentioned. I know, easier said than done..believe me

 

[SouthSIDE Glen]

Glen, here's the deal. First I agree that micing in a club other than vocals,keys is fruitless.Non the less bands do it and insist on it in most cases. The last gig I mentioned was a large outdoor gig.

OK, an outdoor gig is another story altogether; there you gotta mc just about everything, I agree...for both FOH and recording. There I go assuming...in this case assuming it was a smaller indoor gig. My mistake.

As far as bands insisting on miking the drums for FOH even on club gigs, though, I gottta say that I have never once come across that issue. Kick drum is an exception; though I have worked with a few bands that didn't even mic the kick and they sounded just fine and knew it. I guess I've just been lucky not to deal with that level of nincompoopness .

My experience with sound guys is most have not a clue about recording. IMO most cant even get a decent FOH sound.

You won't get any arguement from me on that one. My theory is that anyone with good enough ears and talent to be a decent FOH guy on the small circuits isn't going to waste his time mixing a bunch of wankers for a bunch of drunks at one o-clock in the morning. I'll do it once or twice a month, but I do it attached to specific bands with good musicians and good music and a good bunch of regulars in the audience, not as a house guy for every Tom, Dick and Geddy tribute band to wank their way onto a stage.

It was a party band with horns.A very large outdoor event,maybe 5000 people. I have a 150' splitter snake,he gets half, and I gets half. Totally clean signal.There is no reason at all to bring a totally seperate set of mic's to get the job done as I know you'll agree.

Agreed; you got that one covered. Agian, sorry for making the wrong assumptions as to venue type. Sounds like a fun mix job, though; I love working with horns.

G.

 

[jmorris]

Hey, not a problem Glen. You always have great advise. I figured you may not( or more likely I did not explain myself clearly) understand what I was up against. It really sucks in this situation when your trying to do a real good job for people and you run up against buttheads. Like some sound guys. You know what I mean? I agree with not needing to mic most stuff in clubs except maybe kick and of course vocals but I'll tell, for me, it seems like most bands have to have it freakin blasting to the point I leave with a big headache! I dont understand it....well, maybe Im just getting old.

 

[BRIEFCASEMANX]

Maybe I'm not smart (or maybe you are joking?), but I don't follow this at all. Maybe you are overthinking? You shouldn't have to do all that craziness to your kick track. I can't imagine it sounding normal or even good really.

hey, if I have to work 20hrs or even 100hrs to figure out a trick for a single track in a single song, then that's what I'll do. Try out my trick, it sounds awesome.

 

[TragikRemix]

sounds like a good idea!

what about a gate though? if you set the threshold high enough, you can ditch the hats, but i guess you would lose some snare too and have to cut and paste it in..

 

[TragikRemix]

this is a silly question but what the heck does FOH stand for.

im kinda figuring its something along the lines of 'live sound' but i cant place the letters.

 

[KamikazeKyle]

FOH stands for Front of House, its in reference to live sound yes. It depicts the job of the engineer. Its in relation to the engineer mixing for the audience while the Moniter engineer mixes for the band.

 

[RawDepth]

FOH = Front of House

It is slang for the house mixer or the mixer (and effects gear) that the audience hears. Also we sometimes make reference to the FOH rack or the FOH position. As opposed to the stage monitor mixer and position, (usually back stage,) or the recording mixer, (usually in a truck out back in the alley.)

RawDepth

EDIT: Gee, we posted almost the same reply only four seconds apart. Hmm, small world.

 

[TragikRemix]

gotcha

i usually just say 'sound man' or 'sound guy' and 'house PA'.

or 'onsite rec'ing' (pronounced wrecking)

thanks guys

 

[Reggie]

hey, if I have to work 20hrs or even 100hrs to figure out a trick for a single track in a single song, then that's what I'll do. Try out my trick, it sounds awesome.

Ok I read through it all again, and I still don't get it. Why would I want a flanger or "other time based effects" on my kick track? Whatever works for you I guess, but I'm gonna stick to good ole EQ and gating.

Once I took 5 duplicate tracks of kick drum, 2 panned L and 2 panned R and one mono, and I 180 degree phase reversed the opposing tracks, and used variable phase shifter to shift the mono track +90 degrees. I EQ'ed the L tracks so that the highs were filtered out at about 5khz. I did the same with one of the R tracks but also filtered out the lows at about 150hz. Then I experimented with adding chorus to the mono track and turned the volume of the 4 tracks that were panned hard down about 6db. Added some other time based effects (flanger and phaser) to one of the hard panned pairs. Then I added the same effects to one of the tracks on the other side, only with the flanger/phaser running in the opposite phase cycle at 50% intensity. I then automated each kick transient -3db on the mono track for maximum effect. I also automated the phase of all tracks to match the phase of the mono tracks on just the transients, making concession for any phase shifts caused by the time-based effects. I did the same thing with double tracked guitars in the mix but without the flanger and phaser, and with no automation. Each Guitar was recorded with 2 mics on the cab, a mic about 3ft back and a mic about 15ft back, so there was actually 8 tracks of guitar total, but it would work the same if there was only 4, or possible 5 like the kick. The filtering took out all unnecessary noise, and the room mics on the drum kit provided all the necessary ambience I needed when turned up loud and compressed. It turned out to be one of the best mixes I've done, but took about 20hrs!! to figure out this phase trick. Excellent!