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In Reply to: You'd better do a polarity check! posted by Michael Bishop on March 21, 2007 at 12:03:54:
I have a polarity switch on my new Marantz SACD player but I'm not generally hearing much difference so far, at least not a huge difference and only occasionally. With some discs I hear no difference at all. Shouldn't there always be a difference heard when changing polarity?
2/ Without intending any offence - are you an "audiophile" or a music lover who attends a lot of live acoustic music - or even better - plays acoustic music?
I have found most "audiophiles" are listening for technical changes - not musical/emotional/realism/acoustic space changes, and hence miss the effect of optimised polarity/absolute phase.
And of course, if the speakers are not phase coherent - no one can get it!
Well, Allen, if I had (until recently) a 777 with your level 5 mods, would that make me an audiophile or a music lover? Just kidding!! Mainly I listen for acoustic space changes and I've read from others that the changes that switching polarity brings can be dramatic. I haven't heard a dramatic improvement as yet but maybe, as you suggest, I really am listening techinically rather than emotionally. My speakers are jmLab Cobalt 820's. If you wouldn't mind, could you please tell me more about what is meant by phase coherent and what I really should be listening for when I change polarity?
One way could/should/would simply, which way does it "sound more realistic"?
Like - if you shut your eyes are you more "at the concert" or "less at the concert"?
And don't expect it to be a quick learning thing - it took me ages to be able to confidently choose - and if you find you are thinking too much, just ask a woman - mine has it 100% in seconds, everytime!
Phase coherent means the leading edge of a pulse/transient waveform has the same direction pressure from the speaker system at all frequencies.
Many multicone speakers have their midrange wired out of phase with the bass and tweeter - so a single unidirectional pulse does not come out as a pulse at all - but a mixture of positive and negative pressures.
Single cone speakers (Lowther etc), full range electrostats (ML CLS etc), most panels (Apogee & Magnaplaner etc) and some carefully designed multiway cone speakers (Theil etc) are phase coherent, most others are not - especially if the designer's main focus was achieving extreme flatness of frequency response.
I recently traded in my Apogee mini-grands for a pair of ML Summits. Do you know whether the Summits, which have a crossover frequency of about 250Hz to the cone woofers, are phase coherent by your definition? Thanks.
Unfortunately, because I changed all the electronics and speaker cables in my system at the same time I purchased the Summits, it is impossible to do a direct comparison with the mini-grands. One issue on which I am certain there is subtanstial improvement with the MLs is bass clarity and depth. Both the Apogees and the MLs are very fast and transparent, two qualities of great importance to me in a speaker. I believe that the MLs have an improved midrange--there is a certain realism and purity of tone in the ML midrange that is truly outstanding.
First, after hearing from others I thought the changes would be dramatic, so I'm glad this is not a quick learning thing. I do hear subtle changes and yes, my wife is better at it than me. With some CDs we hear no difference. Why is that?
Now, if I'm hearing changes does this mean that my speakers ARE phase coherent? I just need to understand better why some speaker designers choose not to make speakers phase coherent and why phase coherent speakers are better, if that's what you're saying?
...so I'm glad this is not a quick learning thing <
Totally depends on the person. Once sold a basic system to a client who played woodwinds in the Sydney Symphony - he could get it perfectly on 2 seconds of music - his "audiophile" friend couldn't get it at all - ever.
> I do hear subtle changes and yes, my wife is better at it than me. With some CDs we hear no difference. Why is that? <
Are they live recordings of acoustic music? If so, they have a chance of being phase coherent recordings - but multitracked studio recordings can have mixed phases - the LA recorded band out of phase with the NYC recorded vocalist etc.
> Now, if I'm hearing changes does this mean that my speakers ARE phase coherent? <
Maybe, but there are gradient s to phase linerity in spekaers.
> I just need to understand better why some speaker designers choose not to make speakers phase coherent <
becuase often they can get a far better frequency response flatness if they hook drivers up out of phase, or if they use crossover designs that are optimised for flatness and no phase response. Because frequency response is the spec that people know to ask about.
> and why phase coherent speakers are better, if that's what you're saying? <
I'm not saying they are "better" - just that for me they are better!
if you want a really simple test - go down to RadioShack and pick up a pair of 4 to 6" single cone full range speakers (drivers - not in an enclosure) for no more than (say) $15 each and mount them slightly off center in some largish sheets of plywood (say 3' x 3') - the larger the better. Hook them to you amp and use them to listen for phase changes - because as long as they are single cone (no crossovers or seperate tweeter involved) they will be as phase coherent as a speaker will get!.
Allen, thanks for the feedback.
I checked with my speaker dealer and my jmLabs are phase coherent, but not time coherent because the drivers are on different planes. Something to look for next time, I suppose. How critical is this?
...the ear is sensitive in this area, and most speakers have the woofer or woofer-midrange driver handling this area...you should hear something. A speaker that is totally phase-coherent will have the entire wavefront, regardless of frequency change, so it is easier to hear (perhaps because it is most "natural sounding").
But on most speakers you should hear something if you listen carefully in that frequency range.
Thanks Harry. Will do as you suggest. Have to also listen to my new Marantz burning in, especially in the lower midrange. Sounds a little nasty right now.
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