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In Reply to: RE: drivers out of phase? posted by Duke on December 08, 2009 at 19:31:30
Duke
This reverse polarity in one speaker by design.
Do they pack these two speakers in one box? Is it possible to do that accurately with so many speakers packed by unsuspecting packing boys?
This phase and polarity stuff is so confusing.I have read so many posts on this and am still wondering about it all.There was even an inmate who wrote a best selling book on it who was unfortunately banned from here.
I connect the red to positive and happily listen Who knows perhaps I have never heard what my speaker is capable of.
Follow Ups:
srdavis2K is correct.
Let me try to explain in a bit more detail what I'm talking about by using an example. Suppose we have a two-way system with a second order acoustic slope crossover; in other words, the inherent driver rolloff + electrical filtering = 12 dB per octave rolloff for both the woofer and the tweeter. To simplify, we'll ignore the effects of driver offset for now. At the crossover frequency, the woofer will be lagging the tweeter by 180 degrees, so with both drivers connected with the same polarity we'll get a deepn cancellation null at the crossover frequency. (In fact, this is one way that the designer often checks to see if his crossover is optimal; if there is no deep null with the drivers connected in normal polarity [for this type crossover] then he still has some work left to do.) Anyway the proper way to connect the drivers in this case is with the tweeter's polarity reversed, so that it's in-phase with the woofer in the crossover region.
Now suppose that the crossover frequency is 3.4 kHz and the tweeter's acoustic center is physically 2 inches in front of the woofer's acoustic center (voice coil location is an approximation of a driver's acoustic center). This 2" distance corresponds to 1/2 wavelength at 3.4 kHz, so in this case driver offset adds another 180 degress of phase lag to the woofer and puts the tweeter and woofer back in-phase in the crossover region... almost. Actually, the woofer will be one cycle behind the tweeter at the crossover frequency. If imaging is a very high priority, the designer might want to position the tweeter's acoustic center 2" behind the woofer's, which usually calls for some expensive cabinet construction.
Hope that threw more light than mud on the topic.
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Thanks Duke.
I must someday watch the designers at work.That would be enlightening.The hand on handling of all those complexities in creating an art form within the laws of Physics.
Best Regards
Bill
i meant to say 'driver miswired'. like the drivers in 2 speakers are not wired the same.
Okay, thanks for clarifying, and sorry for the misunderstanding.
Here's what I'd suggest: Play some sort of test tone that's centered in the crossover region. One-third octave pink noise would probably be idea. Listen (or measure) to see which speaker is the loudest in the crossover region, and that's probably the one that's wired correctly.
If you don't have access to a test signal, play music in mono through the speakers and switch back and forth between them. If you don't have a mono switch and a balance control, then use a Y-adaptor from Radio Shack so that both channels get the same signal, and run one into left channel of the CD input and the other into the right channel of the AUX input. By changing inputs you can change back and forth between the two speakers. Whichever one sounds best, that's probably the one that's wired correctly.
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Duke isn't saying that the two speakers are out of phase, but that one of the drivers (the same one) might be designed to be out of phase on each speaker. In other words, the tweeters and midrange drivers might be in phase and the woofers out of phase (by design) with the midrange and tweeter on the same speaker. You still hook up the + and - wires on your speakers the same. It should be transparent to the end user.
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