how do you fix phase issues?

Posted: Mon Jul 23, 2007 10:56 pm

i was surfing the forum and saw cucco touch on some phase issues with recording drums, I am fairly new to recording(2 years) and havent really learned to much about phase problems when recording drums or anything for that matter. im interested about how to acknowledge phase problems when they are there and how to fix them. i really want to have a great drum sound and i think this could help. thx

Posted: Mon Jul 23, 2007 11:59 pm

it happens when mics get into close parimiter of each other and cause some sonic problems with ur mix. what helps is either spacing the mics out further hitting a phase switch which reverses the phase of the mic. you ca switch on and off the phase switch to see if you hear a difference.

and im sure some other people can elaborate more on this subject and hope they do haha.

Posted: Tue Jul 24, 2007 4:19 am

Oh, I could write a book about this, again. And again. Maybe again, again?

You really don't want to be pushing phase invert buttons willy-nilly. You merely need to simply reposition microphones. Inverting phase is necessary when you use 2 microphones top and bottom on snare drum. The bottom microphones is phase inverted. With a microphone in the bass drum, try inverting phase. It provides a harder sounding tighter thud, in reference to the sound of the rest of the kit. With the bass drum microphone in phase and not inverted, you'll get a fatter, rounder more flabby sounding bass drum. Perfectly lovely if that's what you want.

Very hard to follow the 6 to 1 rule when miking a drum kit to keep phase anomalies to a minimum. Cucco has mentioned a technique that I think some folks also referred to as the " Recorder Man" technique? Of course, when you watch the late-night variety shows, you don't see the drum kits miked quite in that manner. Yet, it still sounds perfectly cool. It's still good engineering technique that makes the difference in the end product and not entirely based on more phase coherent recording techniques. After all, it must look right for television. Things are still getting squished and gated.

Oh sure, I make it sound easy. But I also make it sound good. It is easy once you get the hang of it.

Hang on me
Ms. Remy Ann David

Posted: Tue Jul 24, 2007 7:33 am

You may already understand this, but let me explain what a "phase issue" really is. The basic problem occurs when you record the same sound source with two different mics at different distances from the source. If you were recording a pure sine wave and the two mics were half a wavelength apart one mic would record the wave going up at the same time the other mic recorded it going down. When you played them back together, the two recordings would cancel. (Here is a good site that calculates the wavelengths of audio waves.) Of course, in real life you don't record pure sine waves, but the principle is the same.

Here are a couple of ways to fight this. (1) The "recorderman technique" is simply the idea of placing the two overhead mics equidistant from both the snare and the kick drum. Geometrically, it comes to putting the two mics on the circle created by the intersection of a sphere around the snare and a sphere around the kick. Do a search and you can find tips about practical ways of setting this up. (2) The other (far more common) technique is close micing the drums. This doesn't really avoid phase problems. It just makes the sound of the drum in the close mic so much louder than the sound in the far mic that little cancellation can occur. (This is also the idea behind the 3 to 1 rule.)

Posted: Tue Jul 24, 2007 4:14 pm

Ooops? I guess size does matter? I indicated 6: 1 instead of 3: 1 . Sorry.

Phasing effects are particularly unpleasant when you have 2 news anchors sitting side-by-side. Trying to have both of their microphones open, as they are all laughing and joking before bumping into the commercial, even under 3: 1 causes a horrendous phasing anomaly that produces an abnormally hollow boxy smear of sound. So even with the 3: 1 rule, it's not a panacea of perfection. Microphones that have individual compressors on them which are not electronically "locked" to the other compressors detectors, can exaggerate that phasing effect anomaly. Since the microphones not being spoken into now has the level cranked up on the microphone, by the compressor, that is not being spoken into, which produces the worst sounding phasing anomaly effect. And that's the argument for a bus compressor as opposed to individual channels of it. It ain't pretty sounding and nobody wants to hear things that way. And it really doesn't matter whether you're using dynamic, condenser, ribbon, Omni, Figure of 8 or cardioid microphones. Wireless microphones can produce more bizarre sounding problems since they may appear to be neither in phase or out of phase, in relationship to microphones that might be wired and directly next to them.

Phased out
Ms. Remy Ann David

Posted: Tue Jul 24, 2007 4:44 pm

That's OK Remy. I just figured it was an example of the situation the lady comic described - "The reason we women can't do math is that men keep telling us that this (hold fingers four inches apart) is six inches."

Posted: Tue Jul 24, 2007 6:05 pm

so if im using the recorder man technique and micing all the drums it will remove some phase problems but not all, is that about right? it seems that the phase issue is never fixed just reduced.

p.s. i never tried the phase rev on the kick that sounds interesting, got to try that! thx

Posted: Tue Jul 24, 2007 8:49 pm

Correct.
Never fixed. Only settled for.

I thought for a second there that there was this new 6:1 rule and that somehow I was left outta da loop.

Phase is a very wild beast. Simply put, try to not use 2 mics where 1 will do.
For Novice recordists, 'The Bear's' response is all you need at this point.
Later on, after doing a good deal of experimenting on your own, you can come back and absorb Remy's response.

Posted: Tue Jul 24, 2007 10:16 pm

One of the very reasons that 'specialty mics' have been developed for drum kits...mostly stage use......

While these type of mics can withstand tremendous amounts of dbs in a small pattern area, the sensitivity is a low number while the off-axis rejection is off the chart. In a close mic'd situation it would be hard for the toms to become 'phased' with each other due to the physical characteristics of the mics themselves.

In a very controlled room, such as a well designed tracking area, this phase problem is easily cured with simple movements of the mics. A tilt to the left or right....a reposition out of one mics 'hot spot' that benefits both....These are easily heard in an environment that is under control.

In a different scenario, one that has a minimum of sound control, and where the recordings are mostly live to the recorder, its another thing alltogether. This is where it truly behooves the engineer to really KNOW the equipment. Have a definate idea of the polar patterns and sensitivities of the mics being used....know what 'phasing' sounds like and have some idea as to a solution to its problems. A minimilist approach is a great starting point for anyone attempting a recording. The 'Recorderman' method is a good place to begin.

I take it to a different place when placing mics on a drumset. I listen to the drums acoustically in the room. All over the room. There will ALWAYS be spots that are in focus to each particular kit and THESE are the spots to place your mics. Like Remy was suggesting, its not always the overheads straight down equal distant apart nor is it always going to be two as opposed to one overhead. The diaphram size will matter in some cases but mostly it will make a differnce with unmatched mics in both polar pattern as well as diaphram size.

The best way to avoid phase problems is to record the drums separately from all other instruments to eliminate bleed and use all overheads in an omni pattern. BUT your room will have to sound decent for this to work well. Track together with the bass dircet and the guitar through a pod or something as a guide track. You get the feel of a live recording with everyone catching the drummers groove in real-time and you can always save these direct tracks as filler behind a live performance take later with the real sound dialed up.

Its a good reason to really know the parts of the song!

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