Phasing??

S

Shreadzilla

New member
Situation:
While experimenting with recording multiple amp setups, I came upon a nice combination that is damn near perfect save for one problem.
The setup is fairly simple: guitar into A/B splitter, one signal to a POD, the other to a 100 watt half stack.
The pod is going direct to the comp via a mackie 1402 mixer-inputs 5 & 6 [aprox 2- ft. from the comp], the amp [which is aprox 12-15 ft. away in a sealed spare bedroom] is being miked by a sm57, input 1.
Either signal by its self is most superb, HOWEVER, combining the two results in what I can only describe as the classic symptoms of phasing, a kind of hollow notched sound, kinda like one of those old flangers that had the manual sweep knob that you could set where you want & get that sewer pipe sound, etc.

Is the problem the result of the different lengths that the signal must travel?
Anything else I might be overlooking?
Any Ideas
Help me for the love of god
 
Combining direct and mic'ed siganls often results in phasing, because of the distance the sound has to travel through the air before it is picked up by the mic. This will make the recorded mic signal delayed in time compared to the DI. The farther your mic is from the amp, the more noticeable the effect will be.

You can try various solutions:

•Get your mic closer to the speaker cone.
•If you have a DAW, slide the mic track back until the waveforms of that track and the DI "match".
•If you don't have a DAW, you can try patching a delay into the DI signal path, and play with the delay settings until the phasey sound disappears. Or you can insert a delay onto the already recorded DI track for the same results.
 
One tip-

If you are going to split the signal you might as well record the dry guitar instead of the Pod. You can always run it through the Pod during mixdown and have more options on tweaking your final guitar tone. You could even run it through the amp again if you wanted.

Good advice from littledog. You will probably have to delay the track a few ms. I believe the formula is 10ms for every foot the mic is away from the sound source. Somebody please correct me if I'm wrong. It's late and I'm a little fuzzy.
 
Good ideas people, thanks
I think the unequal distance is the culprit, & it's further compounded by the miked signal haveing to travel the 15 ft. TO the amp, then, 15 ft.BACK through the mike cable,etc.
The mic is about 2" away from the cone, so I think my only other options would be to try & minimize the signal path, & maybe play around with adding a delay to the direct signal.
Maybe I could just slap 30" of cable between the pod & the mixer LOL.:D
Thanks
 
The length of the cable runs shouldn't enter into it, since the signal travels darn near the speed of light. It's the distance the sound travels in air that's the problem (about 1130 ft./sec.).

Scott
 
O.K............ now I'm very confused:confused: :confused:
Taking the above suggestions into consideration, I decided to record the two sources [pod/amp] simultaeneously into my daw, each to its own track.. so that I could get a handle visually on the actual latency/delay,etc.
Now to be honest,the cabinet that is being miced has a steel grate for a cover, so the sm57 is about 3-4 inches from the cone, & at the closest edge maybe about 2 inches.

The POD track is consistantly about 275 samples BEHIND the MICED AMP
:confused: :confused:
wtf?
Its the opposite of what has been theorized above,
does the POD have some kind of inherent latency?
And yes I'm sure that I have the tracks right, I did it twice:confused:
Anyone?
 
TexRoadkill said:
One tip-

If you are going to split the signal you might as well record the dry guitar instead of the Pod. You can always run it through the Pod during mixdown and have more options on tweaking your final guitar tone. You could even run it through the amp again if you wanted.
Click to expand...

I know people do this a fair amount..and was the rage with the amp farm plugin...but I have always felt you really needed to hear the final results (or as close as you can get...excess delays and reverbs possibly excluded) to know 'how' you're going to play. A sound TO ME really affects on how I pick, strum, and just generally how I play. I record effects on the track all the time, just for this reason. If I had too much of an effect, ...hey studio time is free...I just re-do it (I never get those magic takes much anywazzz:( ). Just my take on this procedure.

Shread...no specific answers...but at least it sounds like you figured out the time relationship between your tracks...so nudging them back in time to each other, hopefully has cured your problem. Maybe the POD does have a small amount of latency. ..maybe the (not so obvious..but unitentionally overlooked) idea of an out of phase channel, cable, etc could be the problem...but that would be toooo simple of a solution. Sounds like you need motorized mic stands to be able to remote control their placement while monitering!!:p
 
It doesn't really surprise me that the Pod is delayed. Think about it - it's a digital device, and you're going in and out analog, so that's 2 conversions (with their inherant delays) and in between there's processing going on (which may involve "look ahead" function or caching). I know from using the d8b that every digital process involves a small amount of delay or offset - EQ, compression, chorus(flange, etc. -obviously), conversion, you name it. The trick is to know how much is introduced at each stage and how to compensate - it seems like you've got a handle on that.

Scott
 
mixmkr, No shit dude motorized/remote controlled mike stands!!
You know me well:D
I know I can always move the tracks around later, but it bugs me to hear it that way whilst monitoring/tracking, although it does replicate that George Lynch DOKKEN kinda sound lol [also reminds me of a Randy Rhoads kinda sound, GO FIGURE]
I could move the sm57 back to compensate [ I can see the effect of moving the mic around in terms of the visually represented delay]
BUT I hate seemingly inexplicable shit.
One thng you mentioned set off an alarm:
The possiblity of an out of phase cable/channel,Hhmmm...
In setting this whole thing up, one thing I encountered was a very nasty groundloop problem that I dealt with by lifting the ground on the amp, ths removed MOST of the hum, but not all, now I wonder if this is somehow creating the phase ??
I dunno, this seems like it should be so simple, but this one little thing is pissin me
peace,
Shred
 
DigitMus, thanks man, I was thinking along the same lines, does the pod really do a ad/da conversion, keep in mind that I have the 'lil desktop bean model & not the pro, if ths is the reality then I can just delay the miced amp,
I'm gonna get ahold of an official pod rep & see what they have to say about latency,etc. its no big deal, but it certainly threw a wrench into my frame of mind.
good lookin out man,
peace,
Shred
 
The pod could add around 1 - 10ms of processing time.

Mixmkr- I only recomended recording the dry signal in addition to the amp signal since he was splitting it already. It would be pretty tough to play to a dry guitar tone when you intend for it be distorted ;)
 
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