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Mixing Bass amp with bass DI.

If you take a DI on your bass track and then proceed to amp that bass track and mix it in with the DI, what if the two tracks are out of phase, but you like the mic positioning on the amped track. I remember hearing about a plugin where you can adjust phase by the degree for a total of 360°, but let's say you don't have this and need an alternate method. What would you do?


boxcar Mon, 05/31/2010 - 07:44
someone correct me if im wrong but a DI line and a mic line can not be out of phase, only two mics could do that.
they would be out of sync because one source got to the app. a little quicker.
what i do with that is just magnify the two tracks in my app. and nudge the late one forward a hair till it lines up.

EDIT: i stand corrected.
i just found this free phase correction plug in and it says a bass DI and a micked bass cab can be out of phase and this plug can apparently correct that.

BobRogers Mon, 05/31/2010 - 10:08
Since the sound has to travel from the speaker to the mic, the miced cabinet will always be slightly delayed relative to the DI. You can figure the amount of the delay by taking the distance from the speaker to the mic and dividing by the speed of sound in appropriate units. But, of course, the easiest way to correct the difference is to blow the tracks up and time shift one or the other to align the peaks and valleys. You don't need a plugin - just nudge one of the tracks.

Guitarfreak Mon, 05/31/2010 - 21:38
Thanks for the wisdom. Before I say anything else, the project I am going to refer to has been deleted and is long gone now, so unfortunately this is from memory. I remember once I took a DI and before I reamped it I used an amp sim on it to see how it would sound. After I reamped, when both simulated and miked guitar tracks were played together there was phasing. I seem to remember there not being a time delay, or that I adjusted for it (can't remember) and that the phasing remained. The reason I ask about the bass scenario is that I actually like mixing the compressed bass DI in with an amped track, the few times that I have done it, I have liked the results.

Boswell Tue, 06/01/2010 - 04:13
There are two issues here - delay and phase. Don't get them confused. A phase-adjustment plug-in will not necessarily deal with the delay and vice versa.

For bass guitar work where fundamental frequencies are low (and hence wavelengths are long) and the harmonic content is much less than that of a lead guitar, you can usually get away with simple corrections, the most obvious of which being a polarity switch. If your amp mic is close to its speaker, compensating for a few inches of acoustic delay hardly seems worth it when the wavelengths are of order 10 feet, but you could follow Bob's advice and nudge the time axis on the DI track back by about 1ms per foot. But first, check that the waveforms on the amp mic and the DI are both going high together. Flip the DI polarity if this is not the case.


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