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Can hardware change speaker phasing over time??

After years of great listening, I suddenly noticed I wasn't getting the sharp center image with vocals.  I spent hours moving the speakers and even did Room EQ on my Denon receiver (which normally would tell me if speakers are out of phase). The vocals sounded diffuse.  Finally, I switched the wires on one speaker.  BOOM!  Right back to crystal clear center imaging on vocals, on all of my favorite tracks.  I've checked all the wires.  Everything is hooked up right, though now red is hooked to black on one speaker.

Could something have changed the phasing in the hardware?  There is no other place in the set up the wires could have been reversed.  I have triple-checked that the ++++ cable is connected to the red output on the amp.  

Signal goes from Mac Mini by USB to Bryston DAC, by two single channel cables to Denon receiver, by two single channel cables to Parasound A21 Halo amp, by speaker wires (one wire marked ++++) to B&W CM10s.
stroud27612
imhififan's avatar
imhififan
2,136 posts
 
I wired the speakers back to "in phase" and the world was right again. I have a wandering phase issue, either with one of the speakers or the electronics in the receiver or amp.
I suggest you test your B&W CM10s polarity with a 1.5V battery, + to speaker positive and - to negative terminal and see if the woofers "pop" forward. But this test only determine the woofers polarity, in some cases, tweeter or/and mid-range driver could be wired out of phase to its woofers, due to some capacitors in series you need to check the tweeter and mid-range driver at its quick-connect terminals on the crossover.
erik_squires
15,918 posts
 
Hey, what I think is going on more likely is you are training your own ear-brain mechanism.

It's like learning to read upside down.  For a while, you have to work at it, and then one day, bam, you can read upside down just fine, but you no longer can read normal directions of writing correctly. Same kind of thing has been tested with watching TV.

You are flipping the phase, your ear/brain mechanism is going "oh, look, something new!" and then one day your ear/brain gets used to it and that sensation is gone.
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mwh777
72 posts
 
This may be completely unrelated and I know nothing about electronics but, I was an air conditioning tech for 40+ years. There is a weird thing that can happen on 480 volt ac units, if the capacitor for the outdoor fan motor goes bad, the fan will run backwards. Maybe you have a failed capacitor on the mid-range driver that is responsible for the problem. I have no idea if this is even feasible or not.
stroud27612 OP
39 posts
 
I understand the A/C capacitor issue.  When my capacitor went out, I could hear the unit trying to start, so I put a stick through the grill and gave the fan a push.  Sure enough it started running, though I had pushed it the wrong way!  The air was blowing down over the condenser, which still sorta worked.  Then the A/C guy came out and charged me $230 to replace the $12 capacitor.

As for training my ears, I had a lot of friends, at least one who is an audiophile with 5x more $$$ invested in this hobby than I have, and he heard the exact same thing.  Anyway, everything is back to normal.

Of course, as a hobbyist, I am now thinking of buying a new Lexicon receiver to replace the Denon.  It's just that damned urge to upgrade again.
millercarbon's avatar
millercarbon
12,531 posts
 
Please God no! Not a receiver! Lord have mercy!
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