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Phase invertion

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  • Phase invertion

    Hi all

    I own a cd player that inverts phase, and though the manufacturer prefers it, owners can revert back to original polarity arrangement by switching connections in the loudspeakers terminals.

    I've been listening on my SHL-5s now for a couple of months on the inverted polarity mode but has just now switched speaker connections to hear the harbets as intended. I need more time to compare, if there is a difference, but I'm curious what Harbeth's view on this. I find it quite unsettling to imagine the radial woofers firing backwards than forwards. Is this understanding correct?

    Any design and sound penalties based on experience in this set-up? Alan will appreciate your thoughts..

    thanks

  • #2
    Re: Phase invertion

    Did you know that all B&K measuring microphones are phase inverting? Furthermore, do sound engineers ask the polarity of or care about the polarity of their microphones? I very much doubt it. In fact, I dare to say I have never met a recording engineer who has even thought about this issue let alone checked any of his mics. It is entirely possible that a sound engineer could work his entire career and have one of more mics in his armoury wired out of phase with the others! In large-scale orchestral music it would probably not be detectable ....

    So - it's just one of those things that you need not give any attention to at all. As for the manufacturer preferring it, yes doubtless they do - it will have saved the cost of some circuitry to reverse the reverse i.e. put the output back in phase again!
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

    Comment


    • #3
      Re: Phase invertion

      Hi Alan,

      Thanks for the reply. I did an extensive listening last nite after I posted my question, going back and forth, switching the polarity in the SHLs, and my conclusion is-- the inverted phase, as recommended by the cd player maker indeed sounds better thru the harbeth.

      THis is not a speaker issue but a design decision by the player manufacturer that my ears validated--- the mids were more transparent and the highs were more delicate, though there was also an obvious loss of bass impact. When i inverted the polarty in the harbeths to correct the phase, bass thru the radial woofer had more slam that i could feel thru the couch frame. Aside from the increased slam though, everything els was less refined, especially because the bass had an overpowering effect on the music that kind of muddied up the mids.

      I agree we shouldn't make a fuss about this, but the difference in the bass perhaps says that the proper phase is how the woofer should push air i.e. forwards out of the box instead of backwards inwards the box...and the inverted phase out of the cd player means that 'm not hearing radial woofers s intended..

      Sound aside, I wonder if the mechanical excursion of the woofer being in reverse, might lead the woofers to deteriorate faster..anyway, I may just be paranoid..

      thanks again alan.

      Comment


      • #4
        Re: Phase invertion

        I'm afraid but I can not agree with your conclusions. Even with test equipment to give a visual display of the signal waveform, it is impossible to decide upon absolute phase by the time the signal reaches your ears.

        1. Listening alone cannot determine absolute phase. In other words, whilst you may or may not prefer (or you think you prefer) what you call the 'in phase' or 'out of phase' setting there is no way of determining the true phase. You could, conceivably, prefer the wrong phase connection - what then? Since one cannot tell by looking at the cone's movement on normal music whether it is 'in phase' or not you have to use technical equipment to determine this - and even then, you are only checking the phase situation of your own home equipment - but that's not the same thing as checking the whole chain back to the microphones.

        2. There are so many phase reversal possibilities right back to the microphones, the mic cables, the mixing desk, the EQ equipment, the CD mastering, your CD player, your amplifier etc. I can say for certain that nobody really knows whether a recording is 'in phase' or not with the original musical instrument. Nor does anyone in the recording chain care.

        So if indeed you do hear a difference then be prepared to go through the same trial and error process for every recording. Or just forget it and accept that this is an unfathomable issue.

        P.S. Assuming that the entire chain, right up to your CD player is definitely 'in phase' with the musicians, don't you think that it's somewhat arrogant for an equipment manufacturer to deliberately invert the phase regardless of justification? Isn't high-fidelity supposed to preserve the original experience as closely as possible? On the same basis should we make speakers that are deliberately out of phase because someone says they prefer the sound that way? Of course not.

        As a manufacturer seeing this from the opposite side I'm much more cynical than you, and I refer to my earlier comment that there could very well be component and PCB-area cost savings behind this 'preference'.
        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • #5
          Re: Phase invertion

          Alan,

          I certainly recognize that the extraneous variables alone in the entire recording chain would make this issue a non-starter and I agree with you that it shouldn't be a cause for bother.

          Regardless of the intention of the cd manufacturer, I just find it fascinating to note that I'm hearing a difference, and try as I might to dismiss it, the difference is substantial enough to affect my listening.

          I don't like analyzing sound in the "audiophile-obsessed way." At the end of the day, the only question is --does the music move you as it is supposed to? (by the same token that I ended my audio journey with the Harbeths)

          But the observations I have gathered so far is a point of curiosity, which I seek no answers to , and I would rather spend my extra time listening to my music than switching speaker terminals (though I must confess a curiosity about how some "high-end" manufacturer having phase inversion as an option in their equipment-- and if there's anything in it) .

          PS. I installed a cd recorder of pro audio aspirations to my set-up, and with the normal polarity, the bass energy I mentioned earlier was there again, energizing my room....

          Anyway, thanks Alan for the clarifications and insights you are so generous sharing..

          Comment


          • #6
            Re: Phase inversion

            (almost) sorry to raise this one again, but having tried a (inverting) Quad 303 with passive preamp and found it rather dull, switching speaker phase results in a less muffled sound (this is with digital-era recordings, I'm pretty sure absolute phase will vary randomly on older recordings).

            So that's the inverse of the observations of polaris... (other than the observerations on bass which I haven't paid much attention to)!

            The effect is noticeable with the HL-P3 (original type) but more marked with the Magneplanar SMGa.

            I'm pretty sure I'm not audiophooling myself but would prefer some hard data - Alan if you had time to do some of your rapid A/B switching with identical amps I'd love to know what is really going on.

            Mark

            P.S. I must admit to having spent several years in the late '80s happily using Quad 33 and 44 preamps with an American "pocket battleship" amp.

            Comment


            • #7
              Re: Phase inversion

              Hi Mark,

              The best way to find out is to get the cheap phase detector and see if your speakers are connected correctly. Some components such as BC-3 preamp invert phase and therefor you have to reverse the connection at the speakers. Unless you are absolutely familiar with a track i doubt anyone would able to tell if the speakers are connected wrongly.

              Rgds
              ST

              Comment


              • #8
                Re: Phase inversion

                Whilst some sort of measuring equipment connected to the input of your amp and using a microphone to measure the output of your speakers may be able to detect the phase coherence (agreement) throughout your own system, this is really only half the story.

                First, if the preamp is phase inverting and the power amp is also phase inverting (like the Quad system mentioned) then an inverted inversion (think two minuses making a positive) will produce an in phase signal again, and that is what the test equipment will show. It won't be able to detect that the correct phase is the result of a double inversion, because to the test equipment, a 'true' phase and a double-negative will look identical.

                Second - What about the recording and signal processing chain? The microphone(s), mixing desk, outboard signal processing even the software could phase invert at any point along the reproduction chain.

                I'd be amazed if phase inversion of the entire system (music + your equipment) was detectable by ear. The ear is known to be extremely insensitive to phase (BBC research).
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • #9
                  Re: Phase invertion

                  Occasionally, I have used equipment offering the facility to alter absolute phase, sometimes by remote from my seat. It's a very frustrating facility because not only do some tracks sound marginally better one way or the other but individual instruments on a track will sound different. You might have the vocals further back and the strings forward or the drums forward and the guitars receding etc etc and it just drives you up the wall. Of course you have no idea what the producer had in mind when making the disc or LP.

                  I've never known anyone with the facility to do other than leave it on 'normal' after the initial fiddle.

                  Comment


                  • #10
                    Re: Phase invertion

                    Thanks Dave, that's useful. As I understand it then, it may be that the choice of phase "rearranges" the perceived deficiencies of the system, which results in listener preferences varying by individual and programme material.

                    I suspect that a lot of "tweaks" work that way...

                    Alan, when you test your designs with inverting power amplifiers, do you ensure that the signal is also inverted elsewhere in the equipment chain?

                    I do appreciate the Harbeth "BS-free" approach to audio & having worked most of my life in the engineering world it bothers me when observable changes do not seem to be connected with any identifiable physical process (and especially when they are not reliably repeatable).

                    Mark

                    Comment


                    • #11
                      Re: Phase invertion

                      Originally posted by hifi_dave View Post
                      I've never known anyone with the facility to do other than leave it on 'normal' after the initial fiddle.
                      Hello Dave,
                      the point is that a recording is always considered phase true becouse the mastering ingeneer intented to sound so in the final mastering, regardles of the phases of microphones, preamplifiers, mixers, etc used during recording proces. Now the problem seems to be Alan, which can't accept that different people can hear something he can't!

                      Comment


                      • #12
                        Re: Phase invertion

                        Originally posted by honmanm View Post
                        ...Alan, when you test your designs with inverting power amplifiers, do you ensure that the signal is also inverted elsewhere in the equipment chain?
                        No I don't. I really don't care whether the amplifiers are phase inverting or not. Logically though, all the reproduction equipment at home (CD, tuner, cartridge, amp, speakers etc.) should be wired such that it is phase coherent simply because that makes engineering sense. But - big but - to be of any real relevance this phase issue must be traced right back through the audio chain, through thousands of transistors and all sorts of software back to the microphones themselves. Since none of us mere consumers can do that, this strikes me as an issue far beyond our control and hence something that could vary from recording to recording. So we might as well settle on one wiring convention at home and be done with this as an issue.

                        Just another thing we should take for granted and not worry about I suggest.
                        Alan A. Shaw
                        Designer, owner
                        Harbeth Audio UK

                        Comment


                        • #13
                          Re: Phase invertion

                          Originally posted by Vlado View Post
                          ...a recording is always considered phase true becouse the mastering ingeneer intented to sound so in the final mastering, regardles of the phases of microphones, preamplifiers, mixers, etc used during recording proces....
                          I can't understand your point. Surely one person - the mastering engineer - cannot be given the responsibility of fiddling around with the recording's phase to suit himself can he? I hope not. It's the job of the recording engineer to capture the sound as he wishes.

                          But I have never met a recording engineer who has ever tested the true phase of his microphones and cables back to his mixing desk, through his desk, through all the EQ hardware racks, through all sorts of software compressors etc. and to the final .WAV output sent to the mastering plant. I'd go so far as to say that I doubt is such a test has ever been made. So if the front end (recording) is uncalibrated with regard to true phase, why should we be wasting energy fretting over the back end of the process at home? Of course we shouldn't.

                          In the real world recording engineers are (poorly) paid contractors who have a job to do as quickly and efficiently as possible. They are rarely if ever audiophiles. It's a job of work to them as dentistry is to a dentist. There really is no time, motivation or interest in checking dozens or hundreds of mics and recording circuits which could take days - and no producer would pay for that. And if you don't check every source then you might as well not check any.
                          Alan A. Shaw
                          Designer, owner
                          Harbeth Audio UK

                          Comment


                          • #14
                            Re: Phase invertion

                            Hi Vlado,
                            I have no experience of recording or broadcast studios so I can only quote what people such as Alan and others who have a great deal of experience in this field say. Apparently, true phase can get inverted in many ways via mics, cables, connectors, patch boards, mixers etc etc. The result is that certain instruments or performers could be recorded out of phase. So on any recording, everything might be out of phase or everything might be in phase or some things in phase and some out of phase. A nightmare.

                            This is why I have said that when you can reverse the absolute phase of a system easily, you often hear certain instruments or vocals better or worse but not all. It appears to be completely random and eventually you get completely confused and simply don't bother to check anymore. It really doesn't matter. IMO

                            Comment


                            • #15
                              Re: Phase invertion

                              Originally posted by A.S. View Post
                              I can't understand your point. Surely one person - the mastering engineer - cannot be given the responsibility of fiddling around with the recording's phase to suit himself can he? I hope not. It's the job of the recording engineer to capture the sound as he wishes..
                              In the sound production indeed nobody is taking care abot the signal phase. The guy or the girl responsable for the final mix ( recording or mastering engineer) is taking the final decision how the recording should SOUND after pressing. When the record is played at home, the whole audio chain should be in phase to preserve the final mix.

                              Originally posted by A.S. View Post
                              In the real world recording engineers are (poorly) paid contractors who have a job to do as quickly and efficiently as possible. They are rarely if ever audiophiles. It's a job of work to them as dentistry is to a dentist.
                              ... Rudy Van Gelder, Bruce Swedien, Carl Palmcrantz, Bernie Grundman, Jan Persson, Kongshaug.... all dentists ???

                              Comment

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