Phase Shift Through Analog Gear (less than 180)...

[ultra-alex]

This is why I will eq or compress as little as possible when recording. Mixing is a whole other story though. ;D

To quote the late, great, Tom Dowd "If you grab an eq while we are recording, your fired!!! If you don't like the sound move the mic around until you find a sound you like. If that doesn't happen the use a different microphone."

The your fired part was the exact quote the rest was recalled to the best of my memory but the idea is there in full

I don't subscribe to this purist attitude; very often the sound I want to hear is not achievable by just moving or swapping mics.
Does anybody care about the phase shifts introduced by using a cardioid mic in close micing, or by an omni placed near a reflecting surface?
It seems phase is a dirty word; it shouldn't be. Phase is just the other side of frequency response, a very natural thing.

good point.

 

[skipwave]

The potential for creating deliberate phase shift interaction is one of the main things that piqued my interest about the Tilt EQ.

http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=equal_prj.htm

 

[SmitH]

A few caps & xfmrs , doesn't take much
to create a Phase shift
I'd be curious how many " degrees " of shift
there has to be before you start to hear it
[ guess that also depends on the level ]

The answer is not an easy one, because phase shift is not audible on its own, it's audible when two signals have different phase. It depends on the relative levels and the way these signals are mixed. 

I've got a question about phase shift, so I thought I'd post it here.
I'm a drummer, and when I record with one of my bands, I'll bring the console into the live room beside the kit so I can fiddle with it while playing.
What I've noticed is when the kick mic is soled (all other mics off) I hit the Polarity switch and the kick will either sound massive, or it will dissappear.
I'm using 'Extreme Isolation' headphones, but you can still hear the natural kick sound coming through, so is the kick sound coming from the mic cancelling out the natural kick sound coming from the room when the Polarity switch is in?
The same thing happens with the Toms. It changes depending on where the drums are setup in the room.
Would this be similar to how a standing wave works?

 

[abbey road d enfer]

I've got a question about phase shift, so I thought I'd post it here.
I'm a drummer, and when I record with one of my bands, I'll bring the console into the live room beside the kit so I can fiddle with it while playing.
What I've noticed is when the kick mic is soled (all other mics off) I hit the Polarity switch and the kick will either sound massive, or it will dissappear.
I'm using 'Extreme Isolation' headphones, but you can still hear the natural kick sound coming through, so is the kick sound coming from the mic cancelling out the natural kick sound coming from the room when the Polarity switch is in?

That's exactly what happens. Sound reaches the ear via multiple paths, which creates cancellations.
For this reason, assessing the quality of a vocal mic by singing and listening through headphones is a mistake.

The same thing happens with the Toms. It changes depending on where the drums are setup in the room.

The sound picked up by the mic is the sum of direct and several reflected sounds; depending on the position of the drums, the phase relationship with the electric signal will change.

Would this be similar to how a standing wave works?

No; standing waves are just a particular case of reflected sound, where the length of the path is equal to a integer number of wavelengths, yielding a buildup up of sound pressure.

 

[Stagefright13]

Well I personally don't use any equalizers while recording. I move the mics A lot. But mainly the sound is actually at the source. Remember the mic pics up the sound from where it is located. And a good mic will give a decent sample of that. Listening to a drum set in a room and it all sounds good is much different than listening to the mic positions. Example: guitar amp sounds great, then you put a 57 next to the grill. Your ears were 20 feet away and it sounded great. Mic is 2 inches away. Get it?

Multiple mics on a kit cause all kinds of phase issues. Cause of the differences of the close mics verses the overheads obviously. And will NOT be 180 out. The most powerful sounds in a kit are the kick and snare. You can use a piece of string to measure and move the overheads so they align with the kick and snare distance wise. This will get you in the ballpark. And if using a DAW you can slide the overhead track to align the waveforms with the close mics. But like anything else that may not sound better. So you bump the tracks 'till it sounds good.

Or when we all used tape... Just record it that way with the mics at proper sounding posistions.

Oh and I personally compress EVERYTHING on the way in somewhat. No sense taking a converter trip to outboard when I can do it direct for the sound I want straight up. Just know what ya need ahead of time. If you always mix within a certain range of compression then no reason not to lock it in from the get go. But don't do that if you are not sure. If I don't have enough come mix time I add a plugin for a bit more.

And above all the kit sound is the major priority. Trash in trash out as they say. Most of the sound is what the actual drum sounds like. A fantastic player with an awesome drum sound will be cake to record. Probably sound good even with a cassette deck!

John

 

[Silvas]

Well I personally don't use any equalizers while recording. I move the mics A lot.

Ditto. But i look at the waveforms a lot while moving my mics, i mean, i usually use the kick as my room mics center (i tend to use at least 2 room pairs) , and the snare as my overheads center, then i record some hits, look at the phase and timing on my pairs, then adjust, repeat, adjust again...voila. Works for me. But i have quite nice rooms to record on !

Regarding the kick and its phase differences between mics, i found myself manually aligning the transient of both mics (usually whatever dynamic i like that day inside and a FET47 outside) and sometimes i like to align the room mics too, to the kick, if i want to get a very big and roomy kick sound. 

I almost never do EQ when recording. Works great every time.

 

[drpat]

I don't usually EQ while I print either. It's too difficult for my small brain to predict how it will sound in the context of a mix, and I usually end up having to re-eq at mix time. I will however take the time to phase align mics. Usually, I'll pick a reference mic and flip the polarity switch, then move (and flip the polarity switch if necessary) all of the other mics while combined with the reference (one at a time) till it sounds as horrible as it can (usually only needs an inch here or there), then flip the polarity switch back to normal on the reference mic when it's time to roll tape. This usually get's me to a good starting point.

Not sure if this applies, but got me remembering a funny test that I once performed... I was reading a thread on another forum about the latency difference between host based DAWs and Pro Tools HD, and somebody brought up the point of latency through cable and analogue outboard gear, and how bad it could be. Just for ***** and giggles, I decided to do some testing on the subject.

DAW setup - Pro Tools HD, 44.1k/24bit, 96i/o

Analogue Chain - 48 channels of analogue outboard gear going through approximately 4,300 feet of cable. All EQs flat and dynamics inactive but not bypassed.

My converters add 63 samples of latency (round trip), and the analogue chain was 75 samples total, including the converters. So, the conclusion is...

48 channels of analogue outboard gear through approximately 4,300 feet of cable adds about 12 samples of latency. Fairly useless information, but fun to know! I'm still trying to figure out how to convert that into "miles per second", but I'm horrible at math.

 

[SSLtech]

Well, cable length does induce delay when it gets REALLY long. But 4300 feet is getting on towards 1 mile, and you can probably go in the order of a hundred thousand miles in a second though cable, I'd have thought... (which is VERY approximately 60%  the speed of light in a vacuum)

So one mile of cable should be about a hundredth of a millisecond of PURE delay (phase shift notwithstanding). The numbers are rounded up and down a little, but I wanted to get an idea of scale in terms of sample numbers, rather than any decimal point accuracy...

Anyhoo, at 48kHz, 48 thousand samples per second, that's forty-eight samples per millisecond... or about a half-sample of delay from one mile of cable.

About one sample at 96kHz S/R.

About two samples at 192kHz S/R.

So the rest of the 'latency' is elsewhere. Mind you, the amount of 'stuff' boggles the mind, and this thread has already strayed from the initial question by introducing DELAY.

Polarity and phase are complicated enough, but delay just compounds the difficulty. You do have to make an effort keep all three clear in their differences, otherwise things quickly get confusing.

Keith

 

[Ian MacGregor]

UPDATE:

I spent a bunch of time today working out my drum sound demons and came up with a couple observations.

- Most of my issues could (should) be resolved with tweaking mic placement. Without getting crazy with shifting tracks around, there will always be delay when a source hits mics in two different places. The key is that the individual sounds hitting those two mics are the "right" sounds relative to each other. For example, I found that an outside kick mic with a certain range of sub in it wouldn't really work with the inside kick mic I had. By shifting the outside mic around a bit I was able to find an outside kick sound that complemented the inside. For me, this seems like beginner stuff, I just really had the time and need to dig into it recently.

- The IBP is pretty cool and can solve some issues but it does color the sound running through it in a way that drove me to find a way to take it out. Sometimes I could see it being a worthy compromise.

- This is a separate issue from the parallel compression phasey-ness that I've noticed. I'm pretty sure it is a high pass roll-off induced issue as some have discussed.

This has been a really cool discussion.. thanks all around.