Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Chris Carpenter]

I snagged a pair of used jrx115s super cheap and am starting to play with them. The speaker I am testing now looks to have had a tweeter diaphragm replacement (the horn was mounted upside down). The magnatude graph seems to loose coherence and amplitude around 2k (right where the passive crossover is set). I flipped the polarity on the tweeter and got the second graph, which is much more even. Note that I bypassed all crossovers and EQs to get those graphs. Does this imply the tweeter is out of polarity? The leads are properly connected, could this be an after-market diaphragm that was wound the wrong way? Will reversing the polarity on the tweeters solve my problem, or is there something bigger I should worry about?

[Chris Carpenter]

Heres the phase graph...

[Bennett Prescott]

Looks like a classic polarity inversion to me. Of course, either the tweeter OR the LF could have been reversed...

[Tim McCulloch]

Looks like a classic polarity inversion to me. Of course, either the tweeter OR the LF could have been reversed...

And that absolute driver polarity does not necessarily reflect the phase response at acoustic crossover....

[Chris Carpenter]

Looks like a classic polarity inversion to me. Of course, either the tweeter OR the LF could have been reversed...

Ah, I didnt know this was normal. It's strange, I thought the graph with the components in polarity looked nicer.

[Gordon Brinton]

I snagged a pair of used jrx115s super cheap and am starting to play with them. The speaker I am testing now looks to have had a tweeter diaphragm replacement (the horn was mounted upside down). The magnatude graph seems to loose coherence and amplitude around 2k (right where the passive crossover is set). I flipped the polarity on the tweeter and got the second graph, which is much more even. Note that I bypassed all crossovers and EQs to get those graphs. Does this imply the tweeter is out of polarity? The leads are properly connected, could this be an after-market diaphragm that was wound the wrong way? Will reversing the polarity on the tweeters solve my problem, or is there something bigger I should worry about?

Bennett could be right...it could be an after market LF 15 or even a recone kit. For years, JBL has wound their voicecoils opposite of everyone else in the industry. DC voltage to the red post drives their cones rearward instead of forward. Either the LF or HF driver could be off.

If you use subs, the jrx115s should be in phase with those as well.

As you have already learned, it is simple enough to fix with wiring.

[Chris Carpenter]

Bennett could be right...it could be an after market LF 15 or even a recone kit. For years, JBL has wound their voicecoils opposite of everyone else in the industry. DC voltage to the red post drives their cones rearward instead of forward. Either the LF or HF driver could be off.

If you use subs, the jrx115s should be in phase with those as well.

As you have already learned, it is simple enough to fix with wiring.

Oh, i was under the impression this was normal? So I should flip the polarity on the tweets, right?

[Mac Kerr]

Oh, i was under the impression this was normal? So I should flip the polarity on the tweets, right?

You should make them both be like the one without the big notch at the crossover frequency, and the loss of Smaart coherence. Sometimes it is part of the design for the absolute polarity of the tweeter to be different than the woofer, but that would be to smooth out the response through the crossover, not put a hole there.

The woofer should be in the correct absolute polarity.

Mac

[Gordon Brinton]

Oh, i was under the impression this was normal? So I should flip the polarity on the tweets, right?

It doesn't matter which speaker you flip to make the correction. And it doesn't matter which direction the cones move with positive current. As long as all drivers in the stack begin moving in the same direction, then they will be in phase with one another. This will avoid cancellation at the crossover points.

All speaker stacks in the system need to be in-phase with one another as well.

[Mac Kerr]

It doesn't matter which speaker you flip to make the correction. And it doesn't matter which direction the cones move with positive current. As long as all drivers in the stack begin moving in the same direction, then they will be in phase with one another. This will avoid cancellation at the crossover points.

No. See my earlier post. Sometimes the various drivers in a given speaker will not all be in polarity with each other. Sometimes one of them will be intentionally out of polarity with respect to the others to smooth out the phase and amplitude response through the crossover region. It also does matter which drivers you correct if you ever want to use your speakers together with the same model that is unmodified.

All speaker stacks in the system need to be in-phase with one another as well.

All the speaker systems need to be the same, with all the low frequency drivers in polarity with each other, all the mids, and all the high frequency drivers.

Mac

[ProSoundWeb Community]