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Author Topic: Polarity switch on preamps- use or not  (Read 724 times)

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Offline MBHOTAPER

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Polarity switch on preamps- use or not
« on: March 25, 2016, 04:42:21 PM »
I saw an internet comment that said using the polarity/180 degree switch is useful to tighten up a muddy Bass? I never heard that before wondering if anyone else has used the polarity switch on and found that to be true?
Also does anyone here run their preamp with the polarity/180 degree switch on? If so please explain why and what benefits you get - thanks
« Last Edit: March 25, 2016, 04:57:10 PM by MBHOTAPER »

Offline capnhook

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Re: Polarity switch on preamps- use or not
« Reply #1 on: March 25, 2016, 05:09:45 PM »
Try it for yourself on a matrix, and you will hear what happens.


Using Audacity, load in source 1, and 2 copies of source2.  You can do this with two mics sources, or SBD and mics sources --- whatever you have.

Align the start point of source1, with source2's.

INVERT one of the copies of source2.  Leave the other one alone.

Listen to the difference between the source1+source2 mix, and the source1 + source2INVERTED mix.  There will be a clear difference to hear.  A lot of people don't like that sound, and use EQ to tame the bass,  instead.


One of my stereo mics I use a lot is inverted.....when I put it together with the SBD, and monitor a live performance in closed headphones, I don't get overpowered from the bass in the phones plus the bass going all around me at that moment.

A disadvantage to wiring the stereo mic out of phase is that even though I might get another device to delay the SBD, the live matrix would lack sufficient bass, and have a "Tinnnny" sound to it.  That is what you should hear when you do the test matrix.


I set up all of my Audacity projects this way now, to be certain all sources are in phase.  You can try to read the waveforms and see if they are in phase, but your ears will be the proof.
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Offline MBHOTAPER

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Re: Polarity switch on preamps- use or not
« Reply #2 on: March 25, 2016, 05:24:26 PM »
Try it for yourself on a matrix, and you will hear what happens.


Using Audacity, load in source 1, and 2 copies of source2.  You can do this with two mics sources, or SBD and mics sources --- whatever you have.

Align the start point of source1, with source2's.

INVERT one of the copies of source2.  Leave the other one alone.

Listen to the difference between the source1+source2 mix, and the source1 + source2INVERTED mix.  There will be a clear difference to hear.  A lot of people don't like that sound, and use EQ to tame the bass,  instead.


One of my stereo mics I use a lot is inverted.....when I put it together with the SBD, and monitor a live performance in closed headphones, I don't get overpowered from the bass in the phones plus the bass going all around me at that moment.

A disadvantage to wiring the stereo mic out of phase is that even though I might get another device to delay the SBD, the live matrix would lack sufficient bass, and have a "Tinnnny" sound to it.  That is what you should hear when you do the test matrix.


I set up all of my Audacity projects this way now, to be certain all sources are in phase.  You can try to read the waveforms and see if they are in phase, but your ears will be the proof.
so you find the only benefits of using the polarity switch is for a matrix then? Just trying to clarify.

Offline capnhook

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Re: Polarity switch on preamps- use or not
« Reply #3 on: March 25, 2016, 05:30:26 PM »
Yeah....on a single source I don't hear any difference.
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Offline MBHOTAPER

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Re: Polarity switch on preamps- use or not
« Reply #4 on: March 25, 2016, 05:44:01 PM »
Yeah....on a single source I don't hear any difference.
The online information is rather confusing just wanted to ask tapers in the field that may have better insight. From what I can make out you're correct it's only good for single source mic having both (2 mics/stero) on essentially cancels out each other - I guess that means it still sounds the same as if both were off? Thanks shedding light on a confusing subject
« Last Edit: March 25, 2016, 05:47:11 PM by MBHOTAPER »

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Re: Polarity switch on preamps- use or not
« Reply #5 on: March 26, 2016, 11:25:59 PM »
The comment was probably in reference to a speaker monitoring themselves on headphones.  That will yield a very large difference because your ear hears both the headphone signal and the voice via bone conduction, so when polarity of the headphone is reversed there will be cancellation.

When listening to playback of your own voice, that difference disappears.  So it is noticeable when two sources are comparable, and generally not noticeable when only a single source is involved.

Offline DSatz

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Re: Polarity switch on preamps- use or not
« Reply #6 on: March 27, 2016, 09:12:43 AM »
On most stereo microphone preamps a polarity switch, if it exists at all, affects only one channel. Each channel may have such a switch, or (often with portable equipment) only one channel has one. If there's only one switch and it affects only one channel, then it's there so that you can compensate for a miswired cable, or for mikes that are placed far enough apart to produce phase conflicts when their signals are heard together.

Not very many portable, low-cost preamps have polarity switches for both channels because, rightly or wrongly, "absolute polarity" isn't widely considered to be an issue. If you invert the polarity of both channels of a stereo recording, the very great majority of listeners (I'm talking ~90% or more) will notice no difference. Human hearing is just not very sensitive to this issue most of the time. Among those who do report hearing a difference, it seems to be mostly in the sound of a kick drum (or a bass drum in an orchestral recording). Some of these people can pass controlled, blind A/B tests quite handily, so this is definitely a real thing; it just doesn't affect most listeners and most program material. (This is apart from the possibility of a defective or overdriven woofer in one or both of your loudspeakers, which could make a rather different sound depending on the polarity of a strong signal.)

If it tells you anything, the very highly regarded (appropriately IMO) Grace Lunatec V3 preamp had inverse polarity for years, and no one noticed it until this fact was discovered by testing for it specifically--whereupon the manufacturer adjusted the circuit, and made a retrofit mod available on request. I'll bet most V3 owners didn't bother, though. And a fair amount of regular (as well as high end) hi-fi equipment has always been polarity-inverting, without the oh-so-sensitive "golden ears" in the audiophile press ever making any fuss about it.

If you're mixing signals from different sources (what people here call "matrixing") (incorrectly in my opinion), the same acoustical events reach your recorder channels with differing amounts of delay in the different sources, reinforcing some frequencies and weakening others due to the resulting phase differences. Whenever there are multiple pickups of the same acoustical event from different miking distances, this happens (e.g. it already affects the soundboard mix even before the addition of the signals from your microphones). So you may find that one setting of the switches sounds better to you than the other--but if so, it's not predictable which setting would sound better to you.

Plus you might well make a different choice if you had the luxury of monitoring over a good pair of loudspeakers as opposed to headphones. Mixing signal sources live in this way, when you can't possibly have a good monitoring setup, is always a huge gamble, and I am frankly surprised that anyone would do it. Recording the soundboard signals on a separate channel or pair of channels is a whole other matter--you can pick and choose afterward, and decide whether some form of mixture improves the recording or not, and make adjustments at your leisure. In that situation, the polarity of the signals from the soundboard is definitely one variable that you'd want to play with.

--best regards
music > microphones > a recorder of some sort

 

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