SDA 1.2TL Tweeters out of phase?

puunda · January 2006

I've been looking at the XO for the 1.2TL which posted earlier in the SDA, Monitor, RTA Schematics Archive thread. It looks to me like the 4 tweeters are connected out of phase. I know a lot of companies hook the mid range out of phase, but have never heard the tweeter being out of phase with the woofer before. I'm sure there's good reasoning. I just can't figure out why. Can anyone tell me why they've done it this way?

Thanks

dudeinaroom · January 2006

The Only thing I see out of phase is the demensional array. And yes some will wire tweeter, mid, or woofer out of phase from other driver. The only time I know it to be a real advantage is if your x-over has an 18bd/octave slope The signal through the hi pass section of the x-over gets pushed 90 degres ahead, while the low pass section lags 90 , so wiring them out of pahse puts them back in phase

puunda · January 2006

All 4 tweeters have the + connected directly to the - or Black input terminal of the HF input. Yet the 4 Stereo Array woofers have the - connected directly to the - or Black input terminal of the LF input. Does that not mean they're out of phase?

RuSsMaN · January 2006

nevermind, carry on.

dudeinaroom · January 2006

if you look at it again you will notice that all four tweets conect to groung as does that black terminal http://www.polkaudio.com/forums/attachment.php?attachmentid=13670

dudeinaroom · January 2006

ah i c on the other digram they are all hooked to the neg sorry, wrong diagram

heiney9 · January 2006

The tweeters are hooked in what is refered to as a "cascaded taper array" The output of the 4 tweets acts as a single point source by graduating the output of each tweeter (which all cover the same frequency).

The best thing to do, if you are knowledgeable, is to study the correct schematic to confirm they are hooked up as intended. Don't just assume they are incorrect and start messing with them. Chances are if they are the original tweets they are hooked-up correctly as there is no reason for a previous owner to mess with them. I doubt they came from the factory incorrectly hooked up. It never hurts to verify; if you have the correct info. But the likelyhood of them being incorrect is pretty slim.

Carry on

H9

puunda · January 2006

heiney9 wrote:

The best thing to do, if you are knowledgeable, is to study the correct schematic to confirm they are hooked up as intended. Don't just assume they are incorrect and start messing with them. Chances are if they are the original tweets they are hooked-up correctly as there is no reason for a previous owner to mess with them. I doubt they came from the factory incorrectly hooked up. It never hurts to verify; if you have the correct info. But the likelyhood of them being incorrect is pretty slim.
H9

I'm not saying the tweeters are hooked up wrong. I'm saying the diagram, it looks like the tweeters are connected out of phase to the woofers. Obviously they've desinged it this way, and no doubt they're connected that way. I just don't know why though.

jcaut · January 2006

I didn't look at the schematic, but if they're wired electrically out of phase, that's not at all unusual. It just has to do with the crossover topology and the position of the drivers relative to one another. I guess the reason, though it's oversimplifying a bit, is that the crossover components "shift" the phase so that sometimes the drivers need to be connected with reverse polarity in order to acheive the proper response.

That progressive tweeter array seems like it would be very complex, with respect to phase. But Polk knows what they're doing.

Jason

SDA 1.2TL Tweeters out of phase?

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