How to resolve absolute polarity

There's no small amount of controversy surrounding this issue. That's partly because some listeners aren't particularly sensitive to the effect of inverted signal polarity, while for others, it's very irritating. Since a number of manufacturers include a polarity reversal switch on their components, they obviously think that it's worth addressing.

First, I should admit that I am in the latter camp. It always bothered me...

It was 1982. I was trying to set up a pair of Magneplanar T-1D loudspeakers. I had actually written the set-up instructions on these in 1976, back in my ARC/Magnepan days. So I was reasonably knowledgeable about how they should sound.

The LP I was listening to had a famous male performer (singer, writer, guitar player) on it. In fact, I happened to know at the time that this performer owned the very same model of speakers!

It was only his voice and his guitar on the recording. But I just couldn't get the sound right. I could either put him in the room while he played a slightly muffled guitar, or, by swapping the 'positive' speaker connectors for the 'negative' on both speaker leads, I could make his guitar clear, but then it sounded as if he was singing with rocks in his mouth!

By this time, I had been wrestling with the occasional effects of inverted polarity for several years. I had become aware of it through my work doing freelance recordings for the local NPR affiliate and others.

But this LP recording was especially maddening. Apparently, the microphone

for the performer's voice was wired with one polarity convention, but the pickup for the acoustic guitar was wired in reverse.

Or perhaps the microphones used different pin-outs for hot and return signal. Since some mics used pin 1 ground, pin 2 hot, pin 3 negative, and some mics swapped pins 2 and 3, it could have been "correct wires to incorrect mics."

Before I say anything more about that situation, I should probably touch briefly on absolute polarity.

Since some advocates of the audibility of the concept can't even agree on how best to describe it, I'll go for my own simplistic description.

First, you should know that there are two places where the original event's acoustic polarity could be inverted:

(1) Somewhere in the recording chain (microphones, cables, mixer boards, microphone preamps, etc).

(2) Somewhere in the playback system (a component may invert signal polarity, or it could be an incorrect speaker cable hook-up).

Playback of proper acoustic polarity in a recording results in a recorded compression waveform when reproduced in a playback (home) system that maintains that acoustic polarity.

Imagine saying 'punch' and projecting the word forcefully from your mouth. Exhaling. That's compression, similar in a way to positive 'absolute' polarity.

Now, imagine saying the same word by pulling in the air as you say it. Inhaling. That's rarefaction, similar in a way to inverted absolute polarity.

Unfortunately, systems that use loudspeakers that aren't particularly phase/time coherent may not show much of a difference. And more often than not, this is the source for comments such as "I may hear a difference, but it's no big deal" or even "I can't hear any difference. It's just an illusion."

Not only is the effect of inverted absolute polarity audible, I actually ran a test in 1984 to verify that I could measure it on a home audio system I had installed. It was easily and repeatedly measurable at the listening seat.

In general, a system that is non-polarity inverting (a positive waveform on the recording produces a positive waveform into the room) will sound clearer with recordings that have positive absolute polarity. Bass will have more attack on the leading edge. It'll be more defined. Vocals will be more 'present' on the soundstage. And treble will sound more 'correct,' not splashy and ill-defined.

And then, sometime after my "good singer, bad guitar" incident, there was great news. Someone finally wrote a book about absolute polarity!

In 1988, Modern Audio Association in Boston, Massachusetts, published Clark Johnsen's book, The Wood Effect, about the effects of absolute polarity. There is still a limited quantity of the second printing available. You can get his book by e-mailing Clark at clarkjohnsen@gmail.com .

OK, why did I spend so much time on a phenomenon that many audiophiles and some reviewers ignore, as if it didn't exist?

You need to know about the phenomenon in the event that you should inadvertently select two components to compare that happen to have opposite

absolute polarities.

Because the unfortunate result could be that you would make a mistake when evaluating a component, purely because it inverted absolute polarity when compared to another that did not.

Additionally, more than a few power amplifiers and preamplifiers have an odd number of gain stages, which will result in inverted polarity (in both channels of course).

I'm always amused when I read a review (especially if it's a rave review) about a product that I KNOW inverts absolute polarity. Did it mean that the product is even better than the reviewer thought, or did it mean the reviewer is slightly incompetent? Or did he catch it, but not write about it?

Honestly speaking, this is an instance when purchasing an acoustic polarity indicator might be worth the expense even for a consumer who is considering an upgrade.

Jim Smith

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