Mixers with phase reversal?

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nuemes

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Having phase reversal is important when using multiple mics - so why is it that so many mixers do not have this ability? Am I just missing the mixers that do offer it - and if so, are there any 16 channel mixers that offer phase reversal on multiple channels?
 
nuemes said:
Having phase reversal is important when using multiple mics - so why is it that so many mixers do not have this ability? Am I just missing the mixers that do offer it - and if so, are there any 16 channel mixers that offer phase reversal on multiple channels?
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To save costs.

It's easy to remedy though, just create a cable that switches the wires and use that where needed.
 
I just dont understand why phase reversal is needed. I can understand if when using two mics to capture a source and they are out of phase with each other. But why not just nudge one track to line up in phase with the other? (usually move the mic track that is furthest away from the source). I mean if you reverse the phase does it actually mean that the two tracks will be in perfect phase most of the time? i couldnt see how this logic would work.
 
First of all, the phase reverse function in a mixer is designed so that people that are not sitting in front of a DAW have the option. Secondly, sliding a track is not the most efficeient way to get things "in phase" Many people don't realize that phase is infinite. You can be -1937 degrees out of phase, or you could be 2 degrees out of phase. Also, it's important to be able to hear mics in ohase with each other BEFORE you lay the tracks down. If you just start moving the tracks during mixdown there is a possibility that they will not sound the same. That could be good and could be bad. By having a phase reverse switch you can put one mic out of phase with the other and move it around until the biggest nastiest null point. Then you just put it back in phase and you will have a fairly tight phase relationship between the mics.
 
if 2 things are in phase and you reverse the phase of one of them, what does that do? nothing at all?
 
Trey - It puts them out of phase. Simple polarity reversal.

Eck - Say you're hitting a snare - The top head is moving downward (away from the mic) while the bottom head is also moving downward (toward) the mic. The polarity of the bottom mic will need to be reversed to keep it in time. If you shift the track, there's going to be a delay that will mess up the sound of the hit.
 
You are talking about a mic at the top and bottom yeah? There cant possibly be a delay if you nudge the bottom mic track to match up with the top mic track. By zooming right in on the tracks (one step before you see it as digital squares) they can be matched up so they are in almost exact time with each other. There is no phase cancelation atall as they are identical in time and also definetely no delay.

By reversing the phase of the bottom mic how can you ensure that the two mics will not have a delay between them? I mean think about different snares with different distances between the top and bottom skins. THe larger this distance the bigger the delay as the sound is originally coming from the stick on the top skin and travelling down through the whole drum to the bottom skin.

I understand what you are saying about using phase reversal for tracking of say a guitar amp. Could be a good method for gettting the mics to sound good together.
 
there's going to be phasing issues whether you move the track in a DAW or use the polarity button on a mixer. that's just the nature of how sound works. the trick is to minimize it so you don't hear it. mic the top and bottom of a snare and you're going to get two different sounds with two completely different wave forms. nudging the wave form of one track so one cycle of each wave form is lined up, isn't going to do much for the rest of track.

and even if it was going to work...try nudging a track a few samples using an analog console or something that's not a DAW.
 
To deal with the top/bottom issue of micing a snare you can try inverting the wav file of the bottom mic in a DAW to provide the correct polarity.

There's always going to be some amount of delay between 2 or more mics unless you are positioning the capsules next to each other. Moving them in a DAW (or ADAT) can correct these phase inconsistencies.

One has to make the distinction between polarity and phase. Polarity can be 180 degrees out, but the signal could be occuring at the same point in time. For example if a mic cable was wired incorrectly and you have 2 coincident pairs of mics. Phase can be 180 degrees out when the distance matches 1/2 the wavelength.
 
The problem with doing it on a wav file is that you may have already layed a track in which you may never really get the right sound. By checking it at the tracking stage you can ensure right away that you have what you want and what you need. Digital tools are certainly cool, but if you have to rely on them then there is a bigger problem. Also keep in mind that the wave form for a top snare mic and a bottom snare mic are not identical. Nudging the tracks should really be a last resort type of action. When you nudge a track, how do you know that you have only shifted the phase by 180 degrees? If you shift it by 1220, then you have actually created a delay. Secondly, it may not be that useful to have tracks absolutely perfectly in ohase. Certain phasing can be very helpful with tones, depth, width, and all the imaging. The phase button on a console is your friend. Learn how to use it to your advantage, and mixing will be much smoother.
 
Yeah, the phase difference between a top and bottom mic isn't because it arrives there at different times - it's because it's moving the other way when it arrives at the bottom mic. It's the "exact" (of course there's differences otherwise there'd be no point, but it's largely similar in many aspects) same thing in terms of time, but one goes up when the other one goes down.

Shifting things in time will only correct a completely out of phase thing if it's a perfectly cyclical waveform, and it doesn't matter if you have them off by half a cycle at the beginning and end
 
This is getting confusing. Im sure yous are right, but i cant seem to get my head around it. I can kinda understand what yous mean.
 
mattamatta said:
Shifting things in time will only correct a completely out of phase thing if it's a perfectly cyclical waveform, and it doesn't matter if you have them off by half a cycle at the beginning and end
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What do you mean by this?

You can make corrections for out of phase complex waves by making adjustments in a DAW. That's what latency compensation is for.
 
In a casual recording engineering class I took years ago, we miked a snare top and bottom. The bottom gets the snap of the snare, the top gets the slap of the stick, yadda yadda.

The instructor had the students monitor the two mics while reversing the phase of the bottom mic. The difference was distinct. Much fuller sound with the reversal.

This was before the dawn of digital audio so I don't know if the same effect can be accomplished in software. It wouldn't surprise me if it can be done with a simple "flip" of the sampled audio.
 
Scotty said:
In a casual recording engineering class I took years ago, we miked a snare top and bottom. The bottom gets the snap of the snare, the top gets the slap of the stick, yadda yadda.

The instructor had the students monitor the two mics while reversing the phase of the bottom mic. The difference was distinct. Much fuller sound with the reversal.

This was before the dawn of digital audio so I don't know if the same effect can be accomplished in software. It wouldn't surprise me if it can be done with a simple "flip" of the sampled audio.
Click to expand...

It can by inverting the track as mentioned above.
 
Tom, what do you mean by latency compensation and how does it affect phase issues between mics?
 
xstatic said:
Tom, what do you mean by latency compensation and how does it affect phase issues between mics?
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Doesn't really have to do with multiple mics but digital processing. Every plugin or digital processor adds a certain amount of time delay to the signal in order to perform it's processing (latency). Since this can vary with each plugin by different amounts, if the same signal if present in more than one track with different plugins they be delayed by differing amount and cause phase issues. Latency compensation automatically makes up the difference and helps to ensure the tracks are re-aligned so they are back in phase.
 
OK. Thats how I always referred to latency compensation as well. However, most good apps now automatically take care of latency compensation. Personally, I don't consider latency between tracks due to plugins etc... to be phasing. At least not in the same sense as a top and bottom snare mic, or 2 simultaneous vocal mics. I understand that technically you can fix two out of phase tracks digitally by sliding the waveform, but I just think it should be the last resort. With a wav form it is to easy to move a track the wrong direction, or too far, or too little. However, the wav forms will still look extremely similar. By taking care of phase issues at the tracking phase, this problem is solved. The phase button on a ixer doesn't change the pahse by 6000 degrees, it is always by 180 degrees. Also, if your mics are out of phase during tracking, you can't be certain that you are using the right mic, placement, preamp, EQ etc....
 
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