Phase Switching In Pro Tools?

[akg414]

For those of us who don't have a console that has phase-flipping...

If I were to mike up my drum kit (following some "time-tested" techniques) and track right into Pro Tools, could I simply use the Digidesign "TRIM" plug-ins (AFTER TRACKING) to make all the phase switches?

Basically, do these plug-ins server the same purpose on playback, as they would if applied while placing mics and getting sounds?

[Nick Sevilla]

For those of us who don't have a console that has phase-flipping...

If I were to mike up my drum kit (following some "time-tested" techniques) and track right into Pro Tools, could I simply use the Digidesign "TRIM" plug-ins (AFTER TRACKING) to make all the phase switches?

Basically, do these plug-ins server the same purpose on playback, as they would if applied while placing mics and getting sounds?

Yes.

[akg414]

Really?

So you're saying, that I can arm (say) 10 tracks for drums with TRIM plugin, and as my drummer is playing, I can flip the phase that way, and it would be identical to having a board that has phase-flipping on each channel?

[googacky]

You would only be flipping polarity on playback. If you want to flip polarity and record it that way, you'd have to flip it prior to the signal hitting Pro Tools. Actually, I suppose if you really wanted to, you could have all your inputs assigned to busses with trim plugs on them and the output of those busses assigned to audio tracks. That way you'd actually be recording the change. That makes for some convoluted session setup, however. If I were you, I'd simply use trim plugs to determine correct phasing and then apply all those that need flipping by using the audiosuite invert plugin.

[googacky]

I also should have mentioned that you could make a number of cables that have pins 2 and 3 swapped and use these where polarity needs flipping. Make sure you clearly label those bastards. I'm assuming that you're tracking on a console that doesn't have phase switches and that's why you're asking.

[I'm Painting Again]

yeah you could just make flipped cables..but the whole point is to be able to flip around really fast and get your best sounds fast right off the bat before final mic placement..both the cable thing and the protools plug-in thing seem nightmarish to me..

there is this:

http://www.shure.com/ProAudio/Products/ ... RS_content

but $50 per channel is your cost for that ability..but then it's not right at your level and mic controls which is still a compromise..

[@?,*???&?]

For those of us who don't have a console that has phase-flipping...

If I were to mike up my drum kit (following some "time-tested" techniques) and track right into Pro Tools, could I simply use the Digidesign "TRIM" plug-ins (AFTER TRACKING) to make all the phase switches?

Basically, do these plug-ins server the same purpose on playback, as they would if applied while placing mics and getting sounds?

Yes. In reality, depending on your system (LE versions suffer most), just using the digirack plugin will shift your audio file 2 samples. Technically, all the tracks should have the same plugin on them to keep them aligned as they were recorded. Consider too, instead of using the phase flip on the EQ plugin, why not go with a short delay plugin and nudge in .02ms increments and see if you can get the phase much tighter overall. Remember, nudging a file 1 ms would equate to a 1 foot movement of the mic before it was tracked. Have fun. You can certainly tighten up your already decent sounds!

[thunderboy]

Obligatory "phase and polarity are two different things" post here.

jt

[@?,*???&?]

Obligatory "phase and polarity are two different things" post here.

jt

Yup. And we all use those phase flip switches on consoles for the wrong reason.

[Nick Sevilla]

Really?

So you're saying, that I can arm (say) 10 tracks for drums with TRIM plugin, and as my drummer is playing, I can flip the phase that way, and it would be identical to having a board that has phase-flipping on each channel?

Yes.

[Professor]

Obligatory "phase and polarity are two different things" post here.
jt

Yeah, I suppose that always seems to happen... and the funny thing is that I used to believe it until I really dug into it and found that you know, those brilliant old guys in the 50s & 60s who first put "phase reverse" switches on the consoles actually named them correctly.
And as it happens, the cable that googacky described up there with pins 2 & 3 would indeed be reversing the phases of the microphone output within the cable, not inverting the polarity. The result is the same for most every purpose, but the two phases of different polarity were that way coming out of the microphone.


Anyway, as regards ProTools and the "Trim" plug-in... YES, you can use the trim in mixdown to invert the signal inside the computer.
Better still, if you read up a little on the delay running around the drumset microphones, you can use the "Time Adjustment" plug-in to delay channels as necessary so they really line up.
You see, the phase issues that you have with multiple microphones on a drumset come from the difference between the speed of sound (slow at about 1100 feet/sec) and the speed of light (or as close to it as the speed of electricity gets). The microphone stuck inside your bass drum, for example, is maybe 12-inches away from where the beater hits and the drum sound starts moving through the air. The overhead microphone might be say, 7-feet away from the point of impact on the bass drum, and that's a difference of about 6-feet. With the speed of sound just slightly less than 1ms per foot (about .9ms) , that means the bass drum impact arrives at the overhead about 5.4ms late.
Yeah, it's true that some sounds will be out-of-phase between those two microphones. About 92Hz or so should be out-of-phase, and inverting the recorded track with "Trim" would put that frequency in phase, but it wouldn't address the root problem which is the delay. While 92Hz might well be out of phase for two mics with a 6-foot difference from the source, about 184Hz would be in-phase, 276Hz would be out, 368 would be in again, etc. We call that comb-filtering.
So flipping the signal whether inside ProTools, or on a console channel, might fix up a couple frequencies, but delaying the track would fix all of them.
If instead, you were to delay the bass drum (in this example) by about 5.4ms, that would line up all of the frequencies with the signal picked up at the overheads. You might find that you still need to flip a few channels because the microphones are located on different sides of the drum head, and therefore receive their first wavefront from the signal moving in different directions. But still that's what will cure the problem.

Unfortunately, I didn't say it would be the easiest, just the best.
And as it happens, it reads worse than it really is.
Personally, I time-align every drum track to the overheads, and it takes me only a couple minutes.
I set the ProTools clock to read in samples and I zoom in on a single bass drum impact until I can see very clearly the very start of the waveform. I select the audio from the start of the wave on the BD track to the start of the same wave on the OH track (usually upside-down) and I look at the length of the selection in the green display at the top. That's my delay time in samples - the most accurate measure in PT. I delay the BD track that much using the 'Time Alignment' plug and I invert the OH track using 'Trim'. Then I repeat the measure for a snare drum hit, delay the snare track, and invert it as well to match the OH. Repeat for toms, and whatever else may be individually mic'ed.
And that's it. Like I said, it really can go pretty quick. And if I recorded several songs with the same drum setup, then I can just write down the delays and apply them to the next session in mixdown. Sometimes I even measure things out with a sample recording on a template session before I begin tracking a band, and then I have the delays in place for every new session I open from the template.

In the mean time though, yeah, the Trim plug will do you just fine. But it will only process the recorded audio on the way out, it won't flip the signal on its way in to be recorded. That's what the other guys were trying to say up there.

-Jeremy

[Andy Peters]

Obligatory "phase and polarity are two different things" post here.
jt

Yeah, I suppose that always seems to happen... and the funny thing is that I used to believe it until I really dug into it and found that you know, those brilliant old guys in the 50s & 60s who first put "phase reverse" switches on the consoles actually named them correctly.
And as it happens, the cable that googacky described up there with pins 2 & 3 would indeed be reversing the phases of the microphone output within the cable, not inverting the polarity. The result is the same for most every purpose, but the two phases of different polarity were that way coming out of the microphone.

Ummmmm ....

No.

It is a polarity reversal, as it affects all frequencies equally and there is no time dependence.

-a

[hughmanatee]

I thought it was the Invert plugin to invert polarity, am I wrong? also Sonalksis has a great free plugin that has polarity inversion its called Free G. I had no idea you could filp the polarity with the trim plug

[Nick Sevilla]

Obligatory "phase and polarity are two different things" post here.
jt

Yeah, I suppose that always seems to happen... and the funny thing is that I used to believe it until I really dug into it and found that you know, those brilliant old guys in the 50s & 60s who first put "phase reverse" switches on the consoles actually named them correctly.
And as it happens, the cable that googacky described up there with pins 2 & 3 would indeed be reversing the phases of the microphone output within the cable, not inverting the polarity. The result is the same for most every purpose, but the two phases of different polarity were that way coming out of the microphone.


Anyway, as regards ProTools and the "Trim" plug-in... YES, you can use the trim in mixdown to invert the signal inside the computer.
Better still, if you read up a little on the delay running around the drumset microphones, you can use the "Time Adjustment" plug-in to delay channels as necessary so they really line up.
You see, the phase issues that you have with multiple microphones on a drumset come from the difference between the speed of sound (slow at about 1100 feet/sec) and the speed of light (or as close to it as the speed of electricity gets). The microphone stuck inside your bass drum, for example, is maybe 12-inches away from where the beater hits and the drum sound starts moving through the air. The overhead microphone might be say, 7-feet away from the point of impact on the bass drum, and that's a difference of about 6-feet. With the speed of sound just slightly less than 1ms per foot (about .9ms) , that means the bass drum impact arrives at the overhead about 5.4ms late.
Yeah, it's true that some sounds will be out-of-phase between those two microphones. About 92Hz or so should be out-of-phase, and inverting the recorded track with "Trim" would put that frequency in phase, but it wouldn't address the root problem which is the delay. While 92Hz might well be out of phase for two mics with a 6-foot difference from the source, about 184Hz would be in-phase, 276Hz would be out, 368 would be in again, etc. We call that comb-filtering.
So flipping the signal whether inside ProTools, or on a console channel, might fix up a couple frequencies, but delaying the track would fix all of them.
If instead, you were to delay the bass drum (in this example) by about 5.4ms, that would line up all of the frequencies with the signal picked up at the overheads. You might find that you still need to flip a few channels because the microphones are located on different sides of the drum head, and therefore receive their first wavefront from the signal moving in different directions. But still that's what will cure the problem.

Unfortunately, I didn't say it would be the easiest, just the best.
And as it happens, it reads worse than it really is.
Personally, I time-align every drum track to the overheads, and it takes me only a couple minutes.
I set the ProTools clock to read in samples and I zoom in on a single bass drum impact until I can see very clearly the very start of the waveform. I select the audio from the start of the wave on the BD track to the start of the same wave on the OH track (usually upside-down) and I look at the length of the selection in the green display at the top. That's my delay time in samples - the most accurate measure in PT. I delay the BD track that much using the 'Time Alignment' plug and I invert the OH track using 'Trim'. Then I repeat the measure for a snare drum hit, delay the snare track, and invert it as well to match the OH. Repeat for toms, and whatever else may be individually mic'ed.
And that's it. Like I said, it really can go pretty quick. And if I recorded several songs with the same drum setup, then I can just write down the delays and apply them to the next session in mixdown. Sometimes I even measure things out with a sample recording on a template session before I begin tracking a band, and then I have the delays in place for every new session I open from the template.

In the mean time though, yeah, the Trim plug will do you just fine. But it will only process the recorded audio on the way out, it won't flip the signal on its way in to be recorded. That's what the other guys were trying to say up there.

-Jeremy

I know, I'll get my arse beat by stating an opposing view to yours, but here goes:

Most records I have recorded have not had this done, instead I have set up the drumkit mics by ear, until I get the best sound AS IT OCCURS IN THE ROOM.

This means that you KEEP the time delays between the mics. Why?

Because sound travels through the air.

Because sounds of different frequencies travel differently (ray behavior on high freqs. VS waves for low freqs.)

Because to get the drumkit to sound as if it is in a room, it helps to have these delays on the mics, to create more space.

Sure, the kick might sound "tighter" but what about al the other pieces of the drumkit? Does anyone listen TO THE OTHER MICS when they time delay the kick? I hope so. Even though the kick may not get a lot of the other drums, it still does capture them, and you can get slight comb filtering as well by delaying the kick mic in relation to the other microphones.

I really prefer to treat a drumkit as one instrument, and even if I do use more than 3 - 4 mic on it, the close mic I do use I use only to enhance that particular tom drum or sidestick when it sounds.

I like to take as long as possible placing the mics until they ALL work together to capture the drumkit and the room it is in.

Cheers

[@?,*???&?]

Personally, I time-align every drum track to the overheads, and it takes me only a couple minutes.

Very precise description Jeremy. Are you generally happy with the stereo image that results? Those in-between settings can really open up a soundstage though.