2. speakers
  3. 1266479522

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
glai's avatar
glai
446 posts
 
Along the same lines, I have Verity Sarastros which have first order crossovers, all drivers in same polarity with rear facing woofer. As a result, there is large overlap of the midrange and woofer. My room has some inherent narrow band peaks at 50Hz and 80Hz. When I invert the polarity of the woofer, these peaks completely went away and I was left with a near ideal frequency response with no peaks. Base is cleaner, tighter. The soundstage is deeper but some instruments are more difficult to localize in the soundfield. I am bit surprised because violins does not have much energy below 100Hz.

I understand that there is more to just a flat frequency response. What is the ramification of this?
bryoncunningham OP
890 posts
 
Glai - Interesting. Are you saying that you inverted the polarity of the woofer ONLY, and not the tweeter and midrange?
glai's avatar
glai
446 posts
 
Yes, that is correct.
bryoncunningham OP
890 posts
 
Glai - Your case is different, I believe, from what I posted in the OP. You changed the polarity of ONE driver, while I changed the polarity of BOTH drivers, which is why the perceived improvement in my case was such a mystery.

The improvement in your case, I'm guessing, is the result of a certain amount of cancellation between the midrange and the woofer when they are wired with opposite polarity, which in your room, has the fortunate effect of counteracting your room modes. Is that right?

If so, that's a different phenomenon than the one I experienced.
More to discover