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Polarity mystery: Can you help me solve it?

THE BACKGROUND: My speakers are Focal 1007be. They have a Linkwitz-Riley crossover with a 36 dB per octave slope. Because of that, the two drivers are wired with opposite polarity: the woofers are positive, the tweeters are negative.

WHAT I DID: At the advice of a friend with the same speakers, I inverted the polarity of the drivers, by simply reversing the red and black speaker wire leads to the terminals of both speakers, so that the speakers are still in phase with each other, but now the woofers are negative polarity and the tweeters are positive polarity.

WHAT HAPPENED: To my surprise, the sound improved! Specifically, image focus improved. The improvement can't be attributed to the preservation of the absolute phase of the recording, since the improvement was the same for many different recordings (some of which, presumably, preserve absolute phase, while others do not). And the improvement can't be attributed to the speakers being wired incorrectly at the factory, since the friend who suggested that I try this experiment owns the same speakers and experienced the exact same result. So I don't know what to attribute the improvement to.

Can anyone help with this mystery?
bryoncunningham
bob_bundus
1,834 posts
 
phase inversion is a strange phenomenon.
My preamp has an invert function which I some times experiment with if the music sounds lame. Sometimes a substantial improvement, sometimes barely any difference, sometimes a degradation occurs. Sometimes even different cuts on the same record / CD prefer different phase.

Sorry Byron I can't explain this although I can certainly validate your findings. Trouble with hardwired phase inversion is it's not adaptable. I guess go with whatever sounds best the majority of the time. Interesting post --- thanks.
mofimadness's avatar
mofimadness
4,992 posts
 
There was a very interesting article published years ago about absolute/relative phase. "The Wood Effect" by Clark Johnson.
dopogue
1,773 posts
 
I believe that all you did was change the sound for those disks recorded in one polarity (e.g., inverted, non-inverted). So while those disks may sound better, the ones recorded in the opposite polarity should sound worse. However, since the speaker drivers are apparently not polarity-coherent to begin with, I'm surprised you could hear any difference.
jea48
4,453 posts
 
One sure way to check the drivers, crossover, and internal wiring of the speaker is to place a
1 - 1/2 volt D cell battery across the external speaker box terminals. Disconnect the speaker cables from the speaker box terminals. Connect two test lead wires to the speaker box terminals long enough so you can view the drivers from the front. Tag the test lead that is connected to the positive speaker terminal. Use your fingers to hold the neg test wire on the neg post of the battery. Momentary touch the positive test wire to the positive post of the battery. The woofer cone should push forward, not suck back.
Not sure if you will see any movement in the other speaker driver.
onhwy61's avatar
onhwy61
5,229 posts
 
The fact that you think it sounds better doesn't mean it is performing better. It could be a problem with how the speaker mates with your room. Here are the Stereophile measurements.
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