Phase cancellation question

[jacove]

Hi,

I'm pretty new at combining bass DI signal with a miced signal. I have heard that a way to cancel phase issues, well if you don't have the Little labs tool, is to plug in the bass, turn up and listen to the hum...When moving the mic the hum should dissapear at a certain point...my question shouldn't the phase switch on the mixer be "in" when following this procedure?...and then when flipping the switch back the signals should be in phase, or is this wrong? I have just been told the opposite, and it does not make sense to me, so I just want to get it straight...

[Ari-M.]

Originally Posted by jacove

Hi,

I'm pretty new at combining bass DI signal with a miced signal. I have heard that a way to cancel phase issues, well if you don't have the Little labs tool, is to plug in the bass, turn up and listen to the hum...When moving the mic the hum should dissapear at a certain point...my question shouldn't the phase switch on the mixer be "in" when following this procedure?...and then when flipping the switch back the signals should be in phase, or is this wrong? I have just been told the opposite, and it does not make sense to me, so I just want to get it straight...

try nudging the di track forward and back against the cabbie track....do this a few samples at a time...that is if it's already recorded....if not then this is what you want to do....setup the mics where you think they should be (thats up to you).....then go back to your preamps and flip the polarity switch.....which ever setting is the loudest is usually "in phase"...I am really over simplifying this...but start there...I don't think the method of looking for the hum to go away is a good investment of time....I do understand where you are coming from tho....

[Janesaid2me]

I usually dont worry about this ahead of time....i place my mic where i want it....usually about 1-2 feet off the bass cabinet....then once everything is recorded....i bump the DI track forward a hair so that it falls in phase with the mic track and problem is solved.

[jacove]

Thanks guys, so I shouldn't worry about the small phase issues you think, but more listen for which on/off position sounds the best....But just to get the "hum" method straight, ;-)...shouldn't it be with the phase switch pushed "in" that you normally would look for a position where the hum sort of dissapears, and then flip the switch back?

I understand the idea of moving the track forward, I just wanted a method I could use in different settings where I don't have computers with me etc...

[jeremy.c.]

Originally Posted by jacove

Thanks guys, so I shouldn't worry about the small phase issues you think, but more listen for which on/off position sounds the best....But just to get the "hum" method straight, ;-)...shouldn't it be with the phase switch pushed "in" that you normally would look for a position where the hum sort of dissapears, and then flip the switch back?

I understand the idea of moving the track forward, I just wanted a method I could use in different settings where I don't have computers with me etc...

I agree, I flip the polarity on one preamp, set up the mic to where I can clearly hear it is out of phase and thin sounding, then flip the polarity back and it fills out. viola!
For some reason I have an easier time telling when it is out of phase than when it is in phase. Seems more trustworthy to me.

[china jam]

You place mics according to how they sound out of phase?? How does this make any sense? Maybe I misunderstood.

Originally Posted by olivia_nb

I agree, I flip the polarity on one preamp, set up the mic to where I can clearly hear it is out of phase and thin sounding, then flip the polarity back and it fills out. viola!
For some reason I have an easier time telling when it is out of phase than when it is in phase. Seems more trustworthy to me.

[cbc459]

The best way to check for phase offset is the good old fashioned way, with your eyeballs. Zoom in as close as you can, and see if the wave's cycles start at the same time (Whether they both go up and down at the same time or not). If when the cab's waveform goes up, the DI's wave moves goes down, they're out of phase.

[duckoff]

The best way to check for phase offset is the good old fashioned way, with your eyeballs

He he - old fashioned ...... i thought the old fashioned way was using your ears !

[Jaques Beraques]

Originally Posted by duckoff

He he - old fashioned ...... i thought the old fashioned way was using your ears !

No thats New-Skool

[travisbrown]

Uh, what if he's not working on a DAW?

I'm all for positioning the mic properly in the first place.

[travisbrown]

Originally Posted by china jam

You place mics according to how they sound out of phase?? How does this make any sense? Maybe I misunderstood.

Nah, it makes lots of sense.

If you find the spot where you are completely out of phase when you have the polarity reversed, that means you will be completely in phase with the polarity unreversed.

It's just easier to confirm nulling.

[TornadoTed]

I agree, I often find it's easier to find the spot with the mic where the sound is weakest rather than strongest.

[psycho_monkey]

Originally Posted by TornadoTed

I agree, I often find it's easier to find the spot with the mic where the sound is weakest rather than strongest.

for those sounding confused, we should clarify here that first you flip the polarity, then listen to the sound or for some, pink noise coming out of the amp, and position the mic where the most cancellation occurs. THEN flipping the polarity back means your signals are now summing together - and hence in phase (ideally).

FWIW nudging tracks back and forth is only of limited use - you can really only time-align for one particular frequency (this has been gone over several times on here). It might help, but it's much better to get things sounding good in the first place.

[china jam]

Silly. How can you get the amp tone your after if your positioning the mic to just be in phase with the DI?

What if you want it to sound more on or off axis, or you'd like a roomier sound.

I'd personally just go for the best amp sound I could get and forget the DI if you're going to sacrifice proper placement of the cab mic.

[jeremy.c.]

Originally Posted by china jam

Silly. How can you get the amp tone your after if your positioning the mic to just be in phase with the DI?

I would assume in most cases the movement of the mic a few centimeters to phase align your tracks wouldn't disrupt your tone, unless your tone is in fact sort of out of phase sounding, then it's easy, go for it! There is no rule that your tone has to be in phase, it may be part of the sound (but don't use laziness as your "sound")

Originally Posted by china jam

What if you want it to sound more on or off axis, or you'd like a roomier sound.

If you want it more off axis, then turn it off axis, or rommier, move it back into the room which generally gives you fewer phase issues anyway. there isn't one spot in front of an amp where your signals will be in phase.

Originally Posted by china jam

I'd personally just go for the best amp sound I could get and forget the DI if you're going to sacrifice proper placement of the cab mic.

I don't understand your point here as I don't think its what the OP is after, its possible to get both with a small amount of effort.

[jacove]

Thanks guys, I was just looking for a practical and easy way to do deal with both DI and miced signal in terms phase...Just to have a practical "backup" method, that you can use in all kinds of situations...I agree that there might better ways to deal with it with modern technology, but nice to have all options...

[Sigma]

Originally Posted by duckoff

He he - old fashioned ...... i thought the old fashioned way was using your ears !

ya beat me to it