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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
jea48
4,453 posts
 
Kirkus,

That is the way I read the OP at first as well. But through later responses from Bryoncunningham I believe he just reversed the speaker cable leads at each of the box speaker terminals.


Anyway, a 180d change can produce a relative suckout in the lower-mid area, whereby the perceived result is more clarity ion the upper register (=better imaging) and a more pronounced upper bass region.
02-24-10: Gregm

Gregm,

What if instead of reversing the polarity at the box speaker terminals Bryoncunningham pulled the midrange/hi-frequency driver and reversed the polarity there? Then reconnect the speaker cables from the amp to the speakers + to +, - to -.
kirkus
502 posts
 
Changing the relative phase between the woofer and tweeter will of course alter the summed power response, as well as the vertical dispersion charasteristics, of the complete speaker.

But I think it's clear that the relative phase between the two drivers has been preserved the whole time . . . what's still unclear to me is whether the relative phase between the drivers and the passive crossover has been changed, or simply the relative phase between the loudspeaker and amplifier. And I'm also not sure under which conditions absolute phase has been preserved or altered . . . so it's difficult to make further speculation.
rleff
1,065 posts
 
You can simulate this situation using a simulation program although you would need to know the layout of the crossover with component values and connections;LT Spice a free simulation program could do this if you wanted to take the time to download it and then input the needed data(crossover circuit and drivers) then run the simulation and look at the outputs of voltage vs current using the tools in the simulation program.You would see phase relationships as they occur at runtine at any node(test point) in the crossover to the driver(s).
bryoncunningham OP
890 posts
 
my assumption was that you removed the woofers and tweeters from your loudspeaker cabinets, reversed the wiring on each of the drivers, and put the speakers back together. Is this correct?

No. I'm sorry that wasn't clear from the OP. I have done nothing to the speakers internally. I have simply swapped the speaker cables connections from the amp. In the OP, I said "speaker wire leads," which I now see is ambiguous. I should have said, "speaker CABLE leads." Sorry for the misunderstanding, everyone.

When I said that I "inverted the polarity of the drivers," I was referring to the fact that the woofer is wired positive and the tweeter is wired negative, and that, by reversing the speaker cable connections, I changed the woofer to negative and the tweeter to positive.

Kirkus - In light of this information, does your initial crossover/driver/cabinet theory still apply?
kirkus
502 posts
 
Kirkus - In light of this information, does your initial crossover/driver/cabinet theory still apply?
No, sorry, it doesn't. There are only three things that I can think of can explain what you're experiencing:

- Psychological or experimental change, like improving the speaker connections in the process.

- In your room, with your system, and with your program material, reversal of absolute phase make enough of a difference enough of the time, in the right way, to be perceived as an improvement

- The amplifier somehow performs slightly differently when its connection to the speaker is reversed. Speculation about this in further detail would require some pretty obscure types of data to be measured pertaining to the loudspeaker, the amplifier, and the speaker cable . . .
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