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Author Topic: Absolute polarity, How important?  (Read 30669 times)

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Absolute polarity, How important?
« on: November 15, 2004, 01:41:05 PM »

Greetings.

First of all, this is long and I repeat myself because some people simply have a hard time understanding me. Hopefully this time, it is spelled out.

I bring this up not only for my understanding but also others that may be enlightened by responses of those in the field. Without any further ado, lets discuss absolute polarity in the audio chain.

Not polarity per speaker but phase as it travels down the chain in absolute terms of staying coherent to the recording event.

This weekend I have studied absolute phase in the chain. To my surprise, I am consistent in my chain all the way through whereas I wonder who actually pays attention to it. This is basic stuff, granted but to verify my results, I would like a few basic questions answered.


Given the above scenarios, we would assume “compression” to the microphone diaphragm (diaphragm being pushed from initial sound event) should produce a positive wave (looking at single cycles) or rarefraction, with the loudspeakers. (outward cone motion)

JBL woofers (4310/4311/4312) have woofers with inverted phase meaning when a PNP transistor bank is pushing them, the cone is in compression mode (moving backwards). or pulling them (A JBL bright idea??)

1. In terms of absolute phase, what is correct here?

Should a compression event to a microphone cause a positive voltage swing to make a driver move outwards or should the JBL model be normal in this?

Most high quality monitors being used today work with compression events on the negative and rarefraction events on the positive. To clarify..... Microphone compressing means positive and loudspeaker moving forward. The signal on the positive.

2. When viewing the extreme zoom of a track, should the first movement of the wave file be in positive terms or negative terms? Can we hear the difference?  

Some in the field of audio says it does matter and a difference is apparent in sound quality.

How does absolute phase “travel” from microphone, to recorder, to mixer, to 2 track recorder, to mastering, to pressing plant to consumer CD player to speakers and then to the listener. How much of it is screwed up and that by simply changing the polarity at BOTH loudspeakers make that much of a difference?

In terms of absolute phase (input to output of your chain in mastering), here are some links to ponder. I would like some expounding on my questions if you will based on your experience and study of this.

Should we give a damn actually? It took all day to check my chain out down to the other systems as well. Only with the JBL’s did the events change at the loudspeakers. I have one CD player and one CD burner that inverts polarity. I am happy to have found this for sake of not wasting the day.



Here are my findings.

A.   Some equipment inverts phase internally (1 channel) and then re-associates, back at the outputs. From my understanding, this is to put “less strain” on the power supply and or rails
B.   Some equipment inverts phase on both channels.
C.   Some cables come phase inverted.
D.   A mix-down that sounds as though it is “fighting itself” may have one or more channels “out of phase” channels mixed in other channels that are of opposite phase.
E.   Some microphones may have phase inversion.

Here are some web links to ponder.

http://www.positive-feedback.com/Issue1/cjwoodeffect.htm

http://www.siber-sonic.com/broadcast/polarity.html


     http://www.econcrisis.homestead.com/MiscEssaysAbsolutePolari ty.html

     http://www.enjoythemusic.com/magazine/rickerinterview/ricker 9.htm

http://www.gcaudio.com/resources/howtos/absolutephase.html
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Wyn Davis

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Re: Absolute polarity, How important?
« Reply #1 on: November 15, 2004, 02:21:14 PM »

Bill,

I have over the years found that this subject is almost like discussing religion or politics. Some believe, some don't.

Here is my take. The polarity at the output of any device should absolutely match the polarity of the signal being fed to the input. Further, I think that at any point where a signal can be intercepted during a process, it should match the signal fed at the input. I have no opinion about whether it matters if a signal is inverted during some part of a process prior to an output stage. I have never done any listening with that particular in mind. I am sure others around here have.

In the mixing environment I believe there are occasions when a signal inverted against the majority can be useful. In fact, (stepping out on a limb here), I think I recall eavesdropping on a lecture by our host all these many years ago at UCLA where he said he sometimes inverts the polarity of one overhead against the other. Point being, in the mixing environment one does whatever it takes to get the desired result.

In building a large audio system, like a studio, polarity should be positive, absolutely.

Finally, phase is in the time domain, polarity is not. Lets not confuse this issue by mixing those terms.

That is my position, I'm sticking to it.

Digging in ...

Wyn Davis
Total Access Recording
Redondo Beach, Ca


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Re: Absolute polarity, How important?
« Reply #2 on: November 15, 2004, 02:28:11 PM »

So, compression of a microphone diaphram (the inital wavefront hitting it) should produce a positive start and push the loudspeaker cone outward..like a real sound event. Right?

I bet many systems get this wrong..in fact, the JBL's I spoke of certainly must have had a reason for being 180 out.

This is one factor I am trying to understand is "Why" and also, does anyone pay attention to it...in mastering.
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Nika Aldrich

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Re: Absolute polarity, How important?
« Reply #3 on: November 15, 2004, 04:14:01 PM »

You want your recording chain to ideally be set up so that an event that causes air compression on the recording end causes air compression on the playback end.

If a microphone diaphragm moves inwards (away from the source) then the speaker cone should move outwards, simulating a move away from the source.

Issues are caused with instruments wherein the microphone does diaphragm does not move in this fashion - a mic on the underside of a snare, on the beater side of a kickdrum, on the backside of an amplifier, or on the reverse side of any other transducer.  In these situations you would typically flip the phase of the microphone to accommodate the air pressure movements.

As for whether or not absolute phase is audible, it varies with material.  Recent tests that I read about done at the University of Waterloo in Canada, if I recall correctly, showed that the ear is indeed sensitive to absolute phase upon critical testing.  An explanation is given in the relative movement of the basilar membrane.

Nika

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Bob Olhsson

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Re: Absolute polarity, How important?
« Reply #4 on: November 16, 2004, 04:59:45 PM »

For some reason people in the hi-fi world keep making some kind of an issue out of polarity along the lines of exotic speaker wire arguments. It's been very well established for 70 years that polarity has frequently been observed to be audible and hence important to keep an eye on.

JGreenslade

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Re: Absolute polarity, How important?
« Reply #5 on: November 16, 2004, 05:39:04 PM »

On one occasion I was pitching a song to some media mooks (go easy on me); they heard the original arrangement and wanted some changes so I went back, not changing the desk, but wiring up the o/p from the HD recorder feeding the main vocal with a different cable for reasons that escape me that this moment.

When I returned the next day (having been up to 4am arranging) the mooks and label management were up in arms saying that the vocal sounded awful, even though I knew the singer was fine technically. When I returned to the studio I realised the cable carrying her vocal was wired inverting.

I wonder if the difference could've been to electrical consideration though. i.e: The desk + recorder had inverting op-amp i/p/o/p stages, and the one big advantage of transformers is CMR, whereas an op-amp will need careful evaluation to approach the CMR performance even a cheap xformer has as standard? Uneven DC-offset in electrically-coupled circuit perhaps?

I always check absolute phase religiously (a DK is a favoured means), although am not entirely sure why... Have done for years, maybe it was all those hi-fi magazines during childhood.

Cheers,
Justin
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Re: Absolute polarity, How important?
« Reply #6 on: November 16, 2004, 05:44:43 PM »

We still don't have the JBL mystery sorted out yet..afterall, they were the dominant monitors from 1970-1980 and some of the finest productions were done during this time.
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JGreenslade

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Re: Absolute polarity, How important?
« Reply #7 on: November 16, 2004, 05:55:00 PM »

Quote:

A. Some equipment inverts phase internally (1 channel) and then re-associates, back at the outputs. From my understanding, this is to put “less strain” on the power supply and or rails



Love to hear comments from the more academically inclined members as to why it could exert less strain on pwr rails.

The only scenario I could envisage would be if one rail had more current supply than the other, but that would be a weirdo supply right?

We should also reinforce for reader's benefit that polarity and relative phase are different creatures.

You can't hear relative phase, everyone knows that :-)

J
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Re: Absolute polarity, How important?
« Reply #8 on: November 16, 2004, 05:57:14 PM »

While we're at it Bill (or anyone else), have you got any tips for using 4333Bs? (sorry for the thread creep)

Dispose of internal x-overs and go fully active, or just bi-amp and bypass the low inductor?

J
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Re: Absolute polarity, How important?
« Reply #9 on: November 16, 2004, 06:55:38 PM »

I am sorry, I am not familiar with the 4333B's. I would have to have them here and test, to do a deterimination what x-over frequencies, slopes et al would be proper for them. I have never used that model.

Ok, I looked it up.

http://www.jblpro.com/pub/obsolete/4331b_4333b.pdf

Looks simalar to the L-300. I have used L-200's and I actually have a new pair of 077 tweets sitting around which would make an L200 (with proper x over), an L-300, with the sloping front.

Xover is at 800 (12dB/oct) and 8500 (12dB/Oct) from the specs.

If you multiamp them, you would either need a calibrated DB meter or balance the levels by ear.






Quote:

Love to hear comments from the more academically inclined members as to why it could exert less strain on pwr rails.

The only scenario I could envisage would be if one rail had more current supply than the other, but that would be a weirdo supply right?

We should also reinforce for reader's benefit that polarity and relative phase are different creatures.

You can't hear relative phase, everyone knows that Smile




That would be an interesting exchange indeed. I look forward to it myself. AFAIHH, I single supply should not have as much "swing" if two channels, out of phase, draws from it VS in phase. I am going by the observations of others on this..not my own. This was pertaining to Power amplifiers and line amplifiers. I will try to dig up the links. I simply remember some designers hammering this out and measuring the results on the famous "joe list" which most designers pay attention to.
YMMV.
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Giovanni Speranza

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Re: Absolute polarity, How important?
« Reply #10 on: November 17, 2004, 08:56:50 PM »

How  can you check if your audio chain results in an absolute phase? A low freq would show the speaker movement but it should be so low that it would toast it.

bobkatz

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Re: Absolute polarity, How important?
« Reply #11 on: November 17, 2004, 09:05:07 PM »

Joe Speranza wrote on Wed, 17 November 2004 20:56

How  can you check if your audio chain results in an absolute phase? A low freq would show the speaker movement but it should be so low that it would toast it.


You can get a polarity tester. It's actually an excellent tool that will expose a wiring fault anywhere in the system. When working at a new studio I used to go round with a polarity tester in front of each microphone and with an assistant in front of the loudspeaker with the other half of the tester.

I just sold my old polarity tester as the Audio Toolbox already has one built in. Basically, the generator puts out a positive going pulse on pin 2 and the detector should detect a compression from the loudspeaker. Where it gets hairy is whether to detect the woofer, the tweeter or the aggregate.
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David Schober

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Re: Absolute polarity, How important?
« Reply #12 on: November 17, 2004, 11:50:57 PM »

I agree about the polarity tester.   It's a must for every studio and essential when doing a live recording.

For those of you old enough to remember (like me), the old direct-to-disk records that Doug Sax's Sheffield Labs made had an interesting note somewhere in the liner notes.  It read something like, "Audiophiles note: for maximum results, please switch the polarity of your speakers when playing this album."  I remember reading that when I lived back in Texas wondering why they'd say something like that.

Years later when working with Doug, I asked him about it.  He explained to me that the cutting system he had in those days produced a reversed polarity LP.  I don't remember the exact reason, but fixing it would have required another amp in the circuit.  This was something he was unwilling to do as he felt the sonic detriment, if discernible on home systems, was a better compromise than the extra amp.  I don't know why he couldn't just rewire the output stage.  He didn't seem to be putting one over on me, but I was still wet behind the ears back then....
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Re: Absolute polarity, How important?
« Reply #13 on: November 18, 2004, 12:11:28 AM »

David, I remember that too on the Sheffield Lab records. I had the JBL 4311WX and Klipschorns in 1976 when that came about, I had to invert the 4311's anyway, due to the woofer. So this was, invert the Klipschorns, and JBL's were back to zero phase!... and it was madness!

Sheer killer sound those albums are. It gets very little better.

I still have all my Sheffields on vinyl and a safety of Dave Grusin "discovered again" which I am remastering. Fine stuff!


Imagine Klipschorns with custom crossovers triamped and 4311WX hanging above them. I still have the picture somewhere. It was unreal then..still is!
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bblackwood

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Re: Absolute polarity, How important?
« Reply #14 on: November 18, 2004, 07:19:20 AM »

"They made my guitar go straight ahead in a line for miles, and sound like it's coming through a telephone."

- Steve Miller (on the Klipsch speakers)
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ted nightshade

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Re: Absolute polarity, How important?
« Reply #15 on: November 18, 2004, 11:42:04 AM »

Any recommendations or leads on specific models of polarity tester? I got to get with!
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bobkatz

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Re: Absolute polarity, How important?
« Reply #16 on: November 18, 2004, 08:39:24 PM »

ted nightshade wrote on Thu, 18 November 2004 11:42

Any recommendations or leads on specific models of polarity tester? I got to get with!


There's one built into the Audio Tool Box. It's a must-have unit anyway.


See if Neutrik makes one. The one I used to have was made by a French company, I think it was SCV....

BK
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tanov

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Re: Absolute polarity, How important?
« Reply #17 on: November 22, 2004, 12:46:07 PM »

You can use an oscilloscope with 2 inputs.Connect the first
input to the "studio input" and 2nd input to one (L or R)
monitor output.Play a sine wave from a PC.Watch the PC
output and JBL output.Calibrate two waves. Smile
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Geoff Doane

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Re: Absolute polarity, How important?
« Reply #18 on: November 22, 2004, 12:56:59 PM »

bobkatz wrote on Thu, 18 November 2004 21:39

ted nightshade wrote on Thu, 18 November 2004 11:42

Any recommendations or leads on specific models of polarity tester? I got to get with!


See if Neutrik makes one. The one I used to have was made by a French company, I think it was SCV....

BK


Neutrik does make one, the Minirator/Minilyzer (MR1/ML1) combination.  It can do a lot more than just polarity, but the polarity is easy to use.  The ML1 also has a built-in mic for testing speakers.

On JBL polarity:  I was under the impression that JBL was still using the old Western Electric standard, where the black terminal was positive in relation to the red.  This anomaly is well known in the SR world, and I assume their studio speakers follow the same standard.

On the topic of reversing polarity to apply less stress to the power supply rails:  I used this "trick" several years ago for the sub amps of a PA system.  The sub signal was run to the left input of the amp, the amp was switched to bridged mono mode. One speaker ran from the left amp output, and another from the right, with the polarity reversed.  The official reason for this unconventional arrangement was that assymetrical waveforms would stress the pos and neg rails equally.  Unofficially, I saved a patch cord to link the two channels.

Geoff Doane
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Bill Mueller

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Re: Absolute polarity, How important?
« Reply #19 on: November 22, 2004, 09:45:25 PM »

Nika is correct.

I have always been able to tell the difference between polarity in a bass drum. One way is solid and the other is softer. It stands to reason with a quick waveform. I have never been able to tell with a vocal or an instrument that has a softer attack. I usually get my polarity on the snare top mic and then reverse the bottom mic (or not) to deliver best bass. I never trust the cable to be correct on kick and snare.

BTW. JBL used to be notorious for reconing/building speakers out of phase. I once went to a mastering house that had one mid range driver out of phase. I couldn't stand it, so I pulled the speaker and reversed the phase. It was then correct. The engineer told me he had blown that driver and replaced it properly, but it was out of phase with the original.

Best Regards,

Bill
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Re: Absolute polarity, How important?
« Reply #20 on: November 22, 2004, 10:17:17 PM »

Quote:

On the topic of reversing polarity to apply less stress to the power supply rails: I used this "trick" several years ago for the sub amps of a PA system. The sub signal was run to the left input of the amp, the amp was switched to bridged mono mode. One speaker ran from the left amp output, and another from the right, with the polarity reversed. The official reason for this unconventional arrangement was that assymetrical waveforms would stress the pos and neg rails equally. Unofficially, I saved a patch cord to link the two channels.





I am happy to see you experimented along these 'lines' (pun intended)

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bobkatz

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Re: Absolute polarity, How important?
« Reply #21 on: November 23, 2004, 11:00:55 AM »

I produced an absolute polarity test for one of the Chesky test discs. I use the term "absolute" to distinguish from "relative channel". I recorded a solo trumpet in front of a Blumlein pair in a live room. When the polarity is correct, the trumpet seems closer to the listener. Depending on your reproduction system, the difference in apparent distance is as much as 2-3 feet!

Absolute polarity can be terribly important in many cases. We just didn't worry about it much in the analog tape and LP days because we had so little control over it. But in an all-digital storage path there is no excuse to keep absolute polarity in mind. Mastering engineers doing analog processing should check the absolute polarity of their total chains.

How much do I worry about absolute polarity from day to day? I'm probably not doing my job as well as I could...  A mastering engineer ought to switch the polarity of both channels for each song that he/she masters to see which way is most correct. I confess that I don't do it.. I have so much else to do that it's hard to get into the habit, and to be honest, I think the number of times when it makes a real difference are very small and the effect very small. I'm willing to be proved wrong  Smile


BK
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Brent Handy

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Re: Absolute polarity, How important?
« Reply #22 on: December 04, 2004, 05:25:00 PM »

We have been talking about this at www.3daudioinc.com.  I thought it right to mention that when JBL had positive to red wiring drivers, their systems were that way throughout.  Their documentation has always stated that they believed in absolute phase and that the polarity should be reversed on the speaker terminals.

All new systems and drivers are industry standard now.  They do have legacy drivers and systems that are wired the old way.  I was selling JBL back then and the confusion was immense.  Especially with people in the field replacing drivers in older systems with newer VGC drivers, etc.

The problems that people are stating here, like the midrange driver out of phase, is operator/installer error.  It was not that JBL make a mistake and reconed the speaker incorrectly.  If you know their recone process, that is impossible.  What it means is that they had an older driver, and wired it in incorrectly.  Chances are, if they did that, their whole system was out of phase because the systems were not polarity flipped at the terminals.
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Re: Absolute polarity, How important?
« Reply #23 on: December 04, 2004, 05:35:45 PM »

Many years ago some friends of mine decided to make the ultimate woofer for a sound reinforcement system. They started with a Hartley 24". Then they took the assembly apart and installed a valve so they could air-cool the voice coil (this was long before ferrofluid was invented). A little fan motor sits inside there and was powered from power on the multipin that fed the woofer. I think they increased power handling capacity by 3 dB or more.

After taking the woofer apart it lost its magnetism, so they had to send it somewhere to be remagnetized. Lo and behold, the polarity came back inverted from standard... So they just relabelled the terminals on the woofer.

I remember hearing four of these outdoors with large horns attached and hearing fundamental bass at 50 yards.
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Re: Absolute polarity, How important?
« Reply #24 on: December 04, 2004, 05:53:01 PM »

JBL was notorious for turning out random polarity drivers. The first thing you had to do when you bought one of their drivers or speaker systems was to check EVERYTHING. Another company that sold random polarity gear was White.

I can't tell you how many times I got hosed by BOTH company's products until I learned to not trust them to get it right.

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Re: Absolute polarity, How important?
« Reply #25 on: April 21, 2007, 04:27:27 PM »

A Speculation Regarding Perception of Detail

I?ve observed that if an audio system sounds good, no single component of that system can be all that bad nor can the polarity of the recording be played inverted from the live performance.  Reproduced music is in absolute polarity when its pressures and rarefactions match the pressures and rarefactions of the original performance.

I have come to this conclusion because I haven?t been able to compensate for a bad component without causing some egregious sonic and musical tradeoffs.  On the other hand, if a system really sounds awful it may only be a single component or the inverted polarity of the recording that?s causing the problem.  For example, simple as it may seem, a single component could degrade the sound if its power cord is plugged into the wall outlet in less than the best sounding orientation.

A great sounding system is the result of its creator?s choice of components and musical judgment.  The only true basis for their judgment is an understanding of music and a memory of unamplified acoustic instruments and voices in a reasonable acoustic venue and heard from an aesthetically correct distance.

I believe that every choice one makes in the design of an audio system involves tradeoffs, and the only question is which tradeoffs each of us finds acceptable.  Around fifteen years ago, when I first became interested in the audibility and importance of absolute polarity, the speaker system that I?d created some ten years earlier and used for all my serious testing and musical enjoyment had second-order 12 dB Linkwitz-Riley crossovers.  Despite its many advantages it also had one major disadvantage; it wasn?t phase coherent. Without phase coherence it was impossible for me to discern polarity or to hear music purely in or out of absolute polarity because that crossover requires some of its drivers to always play in opposite relative polarities to each other.  As a result that speaker system was inconsistent with the single absolute polarity of live music.  I listened to each separate driver connected first in one polarity and then the other.  It wasn?t all that easy in the beginning to hear the differences, especially with my sealed back electrostatic tweeters.  But since they crossed over at a relatively low 1.6 kHz I eventually decided that they, as well as all the other drivers, sounded better connected in absolute polarity.  And next, with all the drivers playing in absolute polarity, I determined that I greatly preferred hearing music in absolute polarity.  And from that day to this, I only find music played in absolute polarity to be truly emotionally satisfying and believe that the single most important sonic and musical aspect of a properly connected audio system is its ability to reproduce the polarity of live music.

Audio systems must at the very least satisfy the following three requirements to be suitable for rendering polarity judgments.  1. The playback polarity of the source is heard in the same polarity as the original recorded source.  2. The system is phase coherent and preferably minimum phase.  In the analog domain the only classic crossover networks that permit a speaker to preserve the phase-polarity of the input signal are 6 dB first-order Butterworth.  If you?re not sure about your speaker system, you may use single driver headphones.  3. The system?s frequency response deviates no more than  +/- 3 dB from flat between 50 and 8 kHz which is an example of an application of the rule of 400 as defined in the first edition of the Audio Cyclopedia.

The gist of my speculation regarding the perception of detail and polarity is as follows: When one watches film, video or computer monitors the pictures are not seen as a series of separate still images and thank goodness!  It?s because the frames change or refresh fast enough, typically 24, 30 or 60 plus times per second respectively.  The actual flash rate may be up to120 frames per second, depending upon the medium, which causes our eye-brain?s persistence of vision to merge one still frame of a picture into the next.

Similarly, in audio, active noise-canceling headphones illustrate the ear-brain?s persistence of hearing with regard to high frequencies.  The way that active noise-canceling headphones work is by picking up ambient noise with built-in microphones and then generating a signal that?s exactly out of phase to the ambient noise that, at least in principle, should cancel it completely.  The specifications of active noise-canceling headphones indicate that they cancel bass frequencies much more effectively than high frequencies.  And perhaps that?s true to some extent, but much of the reduction in their apparent effectiveness at higher frequencies may be the result of our ear-brain?s persistence of hearing that merges the rapidly alternating relative phase of high frequencies into one sound that has no apparent phase/polarity.  Thus two tweeters playing high frequencies out of relative phase aren?t heard as canceling each other. Perhaps, this phenomena could be considered a corollary of the Fletcher-Munson effect whose curves describe the reduction of our ear?s sensitivity at both frequency extremes.  Well wouldn?t it be great if noise-canceling headphones canceled the high frequencies as well as the bass frequencies?  I?d surely like that and I bet you would too.  So from Shakespeare ? Julius Caesar, Cassius speaking, ?The fault, dear Brutus, is not in our stars [equipment], but in ourselves??  

In my experience it?s exceptionally difficult if not impossible to determine solely by ear the phase of a tweeter?s electrical connection because the phase of the high frequency signal reverses too rapidly for our ear-brain to get a fix on it.  In other words, when the highpass frequency of a tweeter is raised it eventually becomes so high that it exceeds our ear-brain?s ability to distinguish the phase of its electrical connection, and its rapid phase reversals merges both phases into a single sonic impression that?s without a discernable phase.   For example, when two tweeters are playing a 10 kHz signal, if your head is a mere 3/10ths of an inch (a quarter wavelength) closer to one tweeter than the other, the signal from one tweeter arrives at your ears 180 degrees out of phase with the signal from the other tweeter.  Although theoretically they should cancel each other perfectly, I believe most listeners will still hear the 10 kHz signal at full volume.

Before I state the conclusion of my theory you need to know something about the use of test equipment to determine polarity.  The measurements of spectral content, frequency balance, dynamic range, distortion made on components playing music are the same regardless of the polarity of its playback.  Were it otherwise, I wouldn?t have written this think piece about how music played out of absolute polarity affects our perception of detail.  According to ?The Wood Effect? many listeners can detect the polarity of asymmetrical musical signals even though test equipment and computer programs can?t.  Therefore it shouldn?t seem so contrary to common sense, scientific analysis or the least bit mysterious that measurements frequently don?t correlate well with subjective listening tests.  But on the other hand, perhaps some measurements will be more relevant to the way we hear when equipment is played in absolute polarity!

Now it follows, although the cutoff threshold may vary among individual listeners, as the sound?s frequency increases, above some point all listeners will perceive the music?s high frequencies as equally loud regardless of their actual polarity.   But when music is heard out of absolute polarity, the midrange, bass, and even the high frequencies below some frequency, all tend to sound somewhat recessed, rather dry, and bleached out.  Thus psycho-acoustically against a background of a sucked out and a papery dry sounding midrange, and a sucked out dry sounding bass, the high frequencies are heard in bold relief and sound a bit harsh, which also makes the bass and mid-range seem more detailed with faster transients, although they are not.  And that can make the bass sound as if its attacks are quicker because what?s heard as the leading edge of its transients are really the sound of its harmonics which are actually reproduced by the mid-range and tweeter not the woofer.  The result gives the impression of a greatly degraded stereo image that?s rather two-dimensional with a soundstage that?s vaguely focused and somewhat confused.  That also contributes to the false impression that one is hearing more of the performance venue?s space because there seems to be more reverberation when the mid-range is less prominent.  But those effects are really only psychoacoustic artifacts of the music being played out of absolute polarity and not how acoustic instruments and voices sound live!

Here are some other examples of how the psychoacoustics of audio affects our perceptions, which sometimes seems counter intuitive, but nevertheless may resonate with some listeners.  I believe when you add a subwoofer to a system it doesn?t necessarily sound as if you?ve added more bass, but more often than not, it sounds as if the highs have been reduced.  Similarly, add a super tweeter to a system and it may sound as if there?s less bass not more highs.  And if you turn off the bass/mid-bass altogether or reduce your mid-range, the sound seems more detailed when it?s not.

Music played out of phase coherence or out of absolute polarity may cause some listeners to wrongly attribute the low fidelity unpleasant sound to solid state devices or the digital process in general.  This causes some listeners to prefer what they think is the more tuneful, full bodied, and rounded sound that they associate with tube equipment or vinyl records which they believe sounds more like a live performance, when in point of fact, all they really need to hear is music played in absolute polarity.  High-fidelity equipment, tube or solid state, shouldn?t impose a sonic character of its own on the musical signal; its only tasks are to amplify the signal without distortion and control the speakers!  How much tweaking and component swapping in our systems are only musically misinformed attempts to correct for music played out of absolute polarity that in Absolute Reality are bound to fail the test of high-fidelity?  Does this suggest that the conclusions of some prior listening tests should be reevaluated and repeated with music that we know for sure is played in absolute polarity?  I definitely think so, and that should include recordings as well, but each of you may answer that question for yourselves.


The Louis Objective Test of the Audibility of Relative Polarity

Someone, other than the test subject, compiles a 72-minute test CD-R or CD of 72 one-minute music tracks as follows: The first track will be a one-minute excerpt from a CD, record or tape recording of a two microphone stereo recording selected for its musical value but without regard to its actual polarity.  The second track will be the same one-minute excerpt as the first track, but it will be recorded in the same polarity as the first track or in the opposite relative polarity to the first track as determined by the toss of a coin, heads the same and tails in the opposite polarity.  The same procedure is followed for tracks 3 and 4 with different music and repeated again until 36 pairs of identical music tracks have been recorded to the CD for a total of 72-minutes.  The person making the disc memorializes the polarity of each of the even numbered tracks relative to its odd numbered counterpart, and thus he has created a test CD for The Louis Objective Test of the Audibility of Relative Polarity.  The playback system should use single driver headphones or at least a speaker system with consistent polarity, i.e. all drivers move in the same relative phase to each other.  The actual polarity of any track or the playback system doesn?t affect the validity of the test because it?s only a test of the audibility of relative polarity not absolute polarity.  A test of a person?s ability to discern the actual polarity isn?t necessary if they can?t pass the relative polarity test.  If the polarity of the first track of each pair of tracks is randomly selected, then the test CD can also be used as a test of the ability to discern absolute polarity.  Test subjects who discern absolute polarity would by definition have also passed the relative polarity test.

The standard way to scientifically compare component A against component B is by double blind ABX testing.  In order to make ABX testing a bit easier I?ve added non-X that allows the test subject to hear non-X but only knowing that it?s non-X.  When the purpose of the test is to find whether component A or B is preferred, I have a more direct protocol.  Component A and component B are played alternately double blind first one and then the other as many times as needed to state a preference.  Then the sequence is repeated with the order of A and B chosen at random for the next set of alternating comparisons.  The protocol is repeated until the results are statistically significant.  This single test will determine directly both the test subject?s ability to distinguish A from B as well as preference.
Best regards,

George, Perfect Polarity Pundit?  Copyright 2006 All rights reserved by George S. Louis
Digital Systems & Solutions, 1573 Kimberly Woods Drive, El Cajon, CA , Phone: 619-401-9876

The Absolute Reality of Absolute Polarity

Here?s the first part of what I?ve been promising to reveal regarding the Absolute Reality of absolute polarity.  Once you setup your system to play any track on any commercial stamped CD in absolute polarity your system will play all tracks on all commercial stamped CDs, DVDs, DVD audio discs, SACDs, and probably DSDs or any other laser read media in absolute polarity.  I and my music loving audiophile friends have heard that to be the case on thousand of tracks that were mostly CD tracks as well as hundreds of tracks on every other type of disc we tried with the same conclusion.  There a few exceptions such as the Stereophile Test CD STPH-002-2 that has all its tracks after track number 8, a musical polarity test track, in the wrong polarity.  There are some other test discs that may also be recorded incorrectly.  In addition there are some rock music CDs that also have certain polarity anomalies such as the lead vocalist(s) and/or instrumentalist(s) being recorded in a different relative polarity than the rest of the musicians in order that they might stand out against a wall of sound but even those recordings are consistent and we?ve always preferred them played in the same polarity as every other disc.  

I believe that one reason that some music lovers prefer vinyl records to their digital versions is that most of the time when they hear CDs, they?re playing out of absolute polarity.  Here?s a quote from my think piece A Speculation Regarding Perception of Detail, ?How much tweaking and component swapping in our systems are only musically misinformed attempts to correct for music played out of absolute polarity that in Absolute Reality are bound to fail the test of high-fidelity?  Does this suggest that the conclusions of some prior listening tests should be reevaluated and repeated with music that we know for sure is played in absolute polarity?  I definitely think so, and that should include recordings as well, but each of you may answer that question for yourselves.?

So if you use a phase coherent minimum phase speaker system or single driver headphones and non-inverting playback electronics that you should be able to verify those results.  If you believe you?ve found any discs that don?t conform to that standard please let me and the rest of the music loving world know so that we may test them for ourselves.  These conclusion are completely contrary to what you?ve been led to believe by some in the audio industry who claim that absolute polarity is a random or that recorded media has no inherent polarity.  It?s my opinion and that of many of my music loving audiophile friends that once you?ve become accustom to hearing music in absolute polarity it?s addicting and you?ll never want to hear music inverted except when testing for polarity.

The second part of the Absolute Reality of Absolute Polarity is the explanation of why at least 95% and probably closer to 99% of laser read media playback components such as CD players including those in cars invert music.  Many manufacturers have different model CD players with different output polarities which is definitely a mistake and which incidentally isn?t correlated with their prices and with multiple outputs such as fixed, variable, and headphone may also have their outputs in different relative polarities which would also be a mistake.  The reasons for that are more difficult to explain and will follow in due course.  I will be describing the Electronic Industry Association (EIA) microphone standards RS-112-A that were promulgated in October 1979, the CD Red Book, the CBS CD-1 Test CD that?s the digital music industry?s standard since 1980, and the Audio Engineering Society (AES) standard AES26-2001: AES recommended practice for professional audio Conservation of the polarity of audio signals (Revision of AES26-1995), printing date October 11, 2004.  Whether or not a CD player, any laser read media player, components, and speakers are inverting are objective facts that can be scientifically verified that don?t depend upon subjective opinions of a disc?s playback relative polarity to that impressed upon the disc.  

When the lies and various intrigues of the 23 plus years since the inception of CDs are revealed for in all their ugly truths it won?t seem so surprising that the Absolute Reality of laser read media all being made in one polarity to be enjoyed by all those who will listen took that long to be revealed.  There?s been a lot of great music hiding in plain hearing right under our collective ears if only we?d been hearing it in absolute polarity.  Life is short and music is infinite so go listen and enjoy!

George S. Louis
Perfect Polarity Pundit? Chief Polarity Buster of the Polarity Police? who knows he right because his alter ego Father Audio Music Messiah? is on his side who?s brought you the Second Coming of CDs.
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Andy Peters

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Re: Absolute polarity, How important?
« Reply #26 on: April 22, 2007, 04:21:02 AM »

Perfect Polarity Pundit wrote on Sat, 21 April 2007 13:27

 For example, simple as it may seem, a single component could degrade the sound if its power cord is plugged into the wall outlet in less than the best sounding orientation.


So you advocate flipping the mains hot and neutral?  Don't kill yourself.

Quote:

Around fifteen years ago, when I first became interested in the audibility and importance of absolute polarity, the speaker system that I?d created some ten years earlier and used for all my serious testing and musical enjoyment had second-order 12 dB Linkwitz-Riley crossovers.  Despite its many advantages it also had one major disadvantage; it wasn?t phase coherent. Without phase coherence it was impossible for me to discern polarity or to hear music purely in or out of absolute polarity because that crossover requires some of its drivers to always play in opposite relative polarities to each other.


Everyone who's looked at crossovers for more than a minute realizes that two-pole filters (not just Linkwitz-Riley alignments) result in a 180-degree phase shift, which, when the output of the two drivers (in a two-way system) are summed acoustically, result in a suckout at the crossover frequency.   The solution is to simply swap the polarity of one of the drivers.  Then the phase through the crossover region lines up and there's no more cancellation.

Quote:

 As a result that speaker system was inconsistent with the single absolute polarity of live music.  I listened to each separate driver connected first in one polarity and then the other.  It wasn?t all that easy in the beginning to hear the differences, especially with my sealed back electrostatic tweeters.


Really?  The suckout is quite audible.  And it's apparent when you measure the system.  (Oops -- I  used the "m" word.)

Quote:

The specifications of active noise-canceling headphones indicate that they cancel bass frequencies much more effectively than high frequencies.  And perhaps that?s true to some extent, but much of the reduction in their apparent effectiveness at higher frequencies may be the result of our ear-brain?s persistence of hearing that merges the rapidly alternating relative phase of high frequencies into one sound that has no apparent phase/polarity.


Actually, they cancel slowly-varying/steady-state noise a lot more effectively than rapidly-changing noise signals.  A fast impulse, like a gunshot, goes right through the filter, but a noise canceller can train on and cancel a continuous whistle.  However, by limiting the bandwidth of the noise to be cancelled, you can decrease the time required to train the filter.  Read Widrow and Stearns' Adaptive Signal Processing, which is basically the canonical text of the field.

Quote:

In my experience it?s exceptionally difficult if not impossible to determine solely by ear the phase of a tweeter?s electrical connection because the phase of the high frequency signal reverses too rapidly for our ear-brain to get a fix on it.


Which is why you can use a readily available transfer-function measurement tool and remove all doubt!  Don't know the system phase response or polarity?  Measure it.

-a
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Larrchild

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Re: Absolute polarity, How important?
« Reply #27 on: April 22, 2007, 12:54:19 PM »

TDS
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Re: Absolute polarity, How important?
« Reply #28 on: April 26, 2007, 05:14:20 PM »

This is interesting, the thought that one way is right. I've definitely flipped tracks to the wrong polarity on purpose, to get that kind of different sound on the low end, or on a reverb or whatever.
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Sin x/x

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Re: Absolute polarity, How important?
« Reply #29 on: June 07, 2007, 08:22:30 AM »

Andy Peters wrote on Sun, 22 April 2007 03:21



Everyone who's looked at crossovers for more than a minute realizes that two-pole filters (not just Linkwitz-Riley alignments) result in a 180-degree phase shift, which, when the output of the two drivers (in a two-way system) are summed acoustically, result in a suckout at the crossover frequency.   The solution is to simply swap the polarity of one of the drivers.  Then the phase through the crossover region lines up and there's no more cancellation.



This is only true if the acoustic centre of the speakers are in the same place. If they are not (like in real life) then this whole thing does not compute this simple.


My experience with absolute polarity is that when you use speakers with large amounts of distortion (PC speakers)or very high spl's, it's very eazy to hear absolute polarity. But when you use speakers that have very low amounts of distortion (e.g. Quad els)and low levels of spl's, it is very difficult to hear this phenomenon.
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compasspnt

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Re: Absolute polarity, How important?
« Reply #30 on: July 18, 2007, 12:46:17 AM »

Sin x/x wrote on Thu, 07 June 2007 08:22



My experience with absolute polarity is that when you use speakers with large amounts of distortion (PC speakers)or very high spl's, it's very eazy to hear absolute polarity. But when you use speakers that have very low amounts of distortion (e.g. Quad els)and low levels of spl's, it is very difficult to hear this phenomenon.


What would be the reason for this empirically observed phenomenon?
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Tomas Danko

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Re: Absolute polarity, How important?
« Reply #31 on: July 21, 2007, 05:01:23 PM »

compasspnt wrote on Wed, 18 July 2007 05:46

Sin x/x wrote on Thu, 07 June 2007 08:22



My experience with absolute polarity is that when you use speakers with large amounts of distortion (PC speakers)or very high spl's, it's very eazy to hear absolute polarity. But when you use speakers that have very low amounts of distortion (e.g. Quad els)and low levels of spl's, it is very difficult to hear this phenomenon.


What would be the reason for this empirically observed phenomenon?



I always felt that the only reason I could sometimes identify the polarity switch was that, for instance when listening to a soloed vocal track, some plosives would send air AT me whereas the inverted polarity would not.

Hence, some places in the vocals would feel/sound/act in a subtly different way.

Not that I could ever tell which one was better. They both sounded like the recorded vocal take to me.

I don't know where distortion would come to play in this matter, but I'm keen to find out.
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compasspnt

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Re: Absolute polarity, How important?
« Reply #32 on: July 21, 2007, 06:27:54 PM »

This might all be chasing a wild beaten horse with a dead goose, or it might really be something, one of those tiny incremental things that adds up at the end of the day.
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Klaus Heyne

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Re: Absolute polarity, How important?
« Reply #33 on: July 24, 2007, 05:21:06 PM »

Just stumbled upon this fine thread (almost too much to absorb in one sitting.)
bobkatz wrote on Thu, 18 November 2004 17:39

ted nightshade wrote on Thu, 18 November 2004 11:42

Any recommendations or leads on specific models of polarity tester? I got to get with!

...The one I used to have was made by a French company, I think it was SCV.... BK



I have used the SCV polarity tester for over a decade now, and find its sophistication yet simplicity of use still unsurpassed:

LA Audio (an SCV International Group Company),
40 Chigwell Lane, Lughton, Essex, IG10 3NY, UK
Tel:  +44 (0)208 418 0778  Fax:  +44 (0)208 418 0624.
email:  sales@laaudio.co.uk  

I use the SCV not so much for microphone testing (I use my voice, ears, headphones and a polarity reversal switch on my mic pre-amp to tell me what I need to know) but find it most useful for testing the whole recording/playback chain.

I have been in countless studios with severe polarity inconsistencies, all the way up to drivers of main monitors being out of sync with each other and the world at large.

For the last five years I have also used polarity checkers to remove polarity reversals in amplified electric instrument chains (f. ex. bass or guitar and amp): It is astounding how much better I play when the attack of my pick or other string trigger is translated into a wavefront, rather than the loudspeaker being triggered by the first impulse of the note to move backwards/inward, which would suck out the air, rather than pushing it towards my ears.
The SCV works simply and reliably for this purpose.

As there has never been an industry standard for wiring pickup, cable, amp or speaker cabinet polarities, chances are an even 50% that the first trigger of the instrument arrives at my ears polarity reversed.

Even if you don't have a polarity tester, try sometimes wiring up a second speaker cord with its polarity reversed on one end, and switch between that and a polarity-correct cord: One choice will be clearly more focussed and inspiring to play with than the other!

If the reversed cord sounds better (and is later tested as having corrected overall polarity of the chain), simply rewire the speaker's terminal.

Best regards,
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compasspnt

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Re: Absolute polarity, How important?
« Reply #34 on: July 24, 2007, 09:15:14 PM »

Excellent post Klaus!

I am now becoming inspired to check my...everything...
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maarvold

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Re: Absolute polarity, How important?
« Reply #35 on: July 25, 2007, 06:58:11 PM »

Did I hear about this here?

http://www.galaxyaudio.com/CRICKET.html

Around $100--it helped me make a better-sounding record the very first day I used it (I found a couple of phase flops on a rhythm tracking day).  It seems like when you get everything technically sorted out making good recordings just becomes easier.  When a few little things are wrong, I find it disorienting and it's a lot harder to work with the conviction that things will sound good when I'm done.  Sometimes, weeks after the recording date, I'll find that a mono source (like an electric bass recorded direct) was recorded with absolute polarity reversed.  I flip it around, listen, then I think, "Ah, that's better".  On some level I could tell that something was wrong, I just hadn't identified it.  
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Sin x/x

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Re: Absolute polarity, How important?
« Reply #36 on: July 28, 2007, 01:49:03 AM »

compasspnt wrote on Tue, 17 July 2007 23:46

Sin x/x wrote on Thu, 07 June 2007 08:22



My experience with absolute polarity is that when you use speakers with large amounts of distortion (PC speakers)or very high spl's, it's very eazy to hear absolute polarity. But when you use speakers that have very low amounts of distortion (e.g. Quad els)and low levels of spl's, it is very difficult to hear this phenomenon.


What would be the reason for this empirically observed phenomenon?



Your guess is as good as mine.
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Earth Terminal Studios

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Re: Absolute polarity, How important?
« Reply #37 on: September 02, 2007, 11:36:50 PM »

In terms of the reproduction of a whole band the argument that the polarity of the playback system can be correct or incorrect is senseless. I can see that a plosive on a single vocal (for instance) should probably push the reproducing cone toward the listener but with any distance the concept rapidly breaks down.

Really people!

You'd have to have an ear in the same place as all the microphones used to experience the same absolute polarity in reality, as in a band recording!

However, I can see that being confident that a positive voltage swing comming out of ones microphones produces the same all the way father down the line to would be of some comfort.

Presumably upstrokes are negative? Wink

Lewis
Earth Terminal Studios
UK

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Andy Simpson

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Re: Absolute polarity, How important?
« Reply #38 on: September 05, 2007, 06:10:40 AM »

bobkatz wrote on Tue, 23 November 2004 17:00

I produced an absolute polarity test for one of the Chesky test discs. I use the term "absolute" to distinguish from "relative channel". I recorded a solo trumpet in front of a Blumlein pair in a live room. When the polarity is correct, the trumpet seems closer to the listener. Depending on your reproduction system, the difference in apparent distance is as much as 2-3 feet!
........
BK


Whether absolute polarity is important or not, Bob's point about the trumpet is interesting.

When I last looked at the wave-form displays from an orchestral recording of mine, the loud blasts from the brass section (mostly trombone) were extremely asymmetrical (heavily weighted to one side).

Andy
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Rader Ranch

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Re: Absolute polarity, How important?
« Reply #39 on: September 11, 2007, 11:58:04 AM »

Klaus Heyne wrote on Tue, 24 July 2007 17:21


I have used the SCV polarity tester for over a decade now, and find its sophistication yet simplicity of use still unsurpassed:

LA Audio (an SCV International Group Company),
40 Chigwell Lane, Lughton, Essex, IG10 3NY, UK
Tel:  +44 (0)208 418 0778  Fax:  +44 (0)208 418 0624.
email:  sales@laaudio.co.uk  



FWIW it's called the PC90 now, cost $425, and the US distributor is www.cwsalesandmarketing.com
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