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Author Topic: Tweeter polarity  (Read 17315 times)

Gordon Brinton

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Re: speaker system polarity
« Reply #10 on: April 04, 2011, 09:10:26 pm »

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

According to the jrx115 spec sheet, the tip (1+) pin goes to the + terminal on both HF and LF components. However, we don't know if the components are factory. The only way to go now is to get the crossover point between horn and LF (15) to be coherent. (as he has already done.) Then check the phase between 15 and subs.

What other choice does he have since the boxes have been hacked?
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Chris Carpenter

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Re: speaker system polarity
« Reply #11 on: April 04, 2011, 09:13:06 pm »

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 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

All of the leads are connected correctly in the cabinets, both woofers in the 115s push out when positive voltage is applied to the positive side of the speaker. Now knowing jbl winds their voice coil opposite of the norm, looking at the difference in charts, and that the tweeter diaphragm has been replaced, can I conclude that I should flip the polarity of the tweet?
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Mac Kerr

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speaker system polarity
« Reply #12 on: April 04, 2011, 09:23:40 pm »

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

According to the jrx115 spec sheet, the tip (1+) pin goes to the + terminal on both HF and LF components. However, we don't know if the components are factory. The only way to go now is to get the crossover point between horn and LF (15) to be coherent. (as he has already done.) Then check the phase between 15 and subs.

What other choice does he have since the boxes have been hacked?

Maybe if you read the quote of you that I was referring to, you would know that I was not talking about the OP's speakers, but about your incorrect statement. Not every response in a thread on an Internet forum is going to be about the original post.

Mac
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Gordon Brinton

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Re: speaker system polarity
« Reply #13 on: April 04, 2011, 10:06:45 pm »

@Mac - I was just speaking in general about how to achieve component phase. I don't dispute that some boxes may differ. Sorry for the misunderstanding.

@Chris - Do you know that the 15's are original JBL drivers? If so, then they (the 15's) are probably correct as is. However, if the horn diaphragm has been replaced with a generic brand, that happens to be wound opposite of the original, then reversing it may be necessary. I can't tell you that. I don't know.

The reason I brought up the polarity of the 15's was due to the possibility of those being generic replacements as well.

Many JBL drivers, but not all, move rearward when positive DC current is applied to the positive pole. Perhaps an owner of original jrx115's can tell us which way the cone moves.

Hope this helps.
« Last Edit: April 04, 2011, 10:18:52 pm by Gordon A. Brinton »
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Chris Carpenter

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Re: speaker system polarity
« Reply #14 on: April 04, 2011, 10:24:18 pm »

I checked the crossover, it definitely flips the polarity of the tweeter.
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Bob Leonard

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Re: Tweeter polarity
« Reply #15 on: April 06, 2011, 08:29:37 am »

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.

Incorrect. Starting in the '50s JBL had standardized on a polarity convention specific to their drivers. As time went on and "MI - musical instrument" drivers became a large part of their inventory JBL began to fall in line with the rest of the industry and newer speakers were wired to the spec we accept as standard today. That is, positive voltage = voice coil moves out.
 
Because it was not possible to change entire lines or products already in production simply to meet the "MI standard" JBL began a gradual phase in of their products. They did not change existing products. Regardless of that fact mutli driver boxes, those with crossovers, should be considered "in phase", and they will be until re-wired or the crossover modified. That also includes bi-amped products where the internal wiring has taken this into account. The only time phase is an issue will be when a raw driver is used by another manufacture or home brew specialist, and then, maybe. "Fixing the wiring" is only an option if the wiring is incorrect to begin with, and I suggest some education on a subject prior to making blanket and misleading statements covering entire product lines.
 
It is best to check polarity in those cases, or any case where you may feel there is a polarity problem. You can do this by referencing JBLs white paper on the subject, the final word on JBL polarity. See below;
 
http://www.jblpro.com/catalog/support/getfile.aspx?docid=241&doctype=3
 
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Chris Davis

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Re: speaker system polarity
« Reply #16 on: April 06, 2011, 04:54:50 pm »

I checked the crossover, it definitely flips the polarity of the tweeter.
Not all that uncommon.  I have seen and measured this on various other boxes in the past.  In fact, when paired up with Bob's response I think you have a good reason to verify all your drivers are correct.
In addition, as a sanity check, I would also compare the crossovers from all suspect boxes with a "known good" crossover to see if the polarities are correct. 
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Bob Leonard

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Re: speaker system polarity
« Reply #17 on: April 06, 2011, 07:20:27 pm »

I checked the crossover, it definitely flips the polarity of the tweeter.
Not all that uncommon.  I have seen and measured this on various other boxes in the past.  In fact, when paired up with Bob's response I think you have a good reason to verify all your drivers are correct.
In addition, as a sanity check, I would also compare the crossovers from all suspect boxes with a "known good" crossover to see if the polarities are correct.

So all you need now is the schematic below and a volt meter. Let us know how you make out.
http://www.jblproservice.com/pdf/JRX%20Series/JRX115.pdf
 
 
 
 
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Gordon Brinton

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Re: Tweeter polarity
« Reply #18 on: April 06, 2011, 07:45:07 pm »

Incorrect. Starting in the '50s JBL had standardized on a polarity convention specific to their drivers. As time went on and "MI - musical instrument" drivers became a large part of their inventory JBL began to fall in line with the rest of the industry and newer speakers were wired to the spec we accept as standard today. That is, positive voltage = voice coil moves out.
 
Because it was not possible to change entire lines or products already in production simply to meet the "MI standard" JBL began a gradual phase in of their products. They did not change existing products. Regardless of that fact mutli driver boxes, those with crossovers, should be considered "in phase", and they will be until re-wired or the crossover modified. That also includes bi-amped products where the internal wiring has taken this into account. The only time phase is an issue will be when a raw driver is used by another manufacture or home brew specialist, and then, maybe. "Fixing the wiring" is only an option if the wiring is incorrect to begin with, and I suggest some education on a subject prior to making blanket and misleading statements covering entire product lines.
 
It is best to check polarity in those cases, or any case where you may feel there is a polarity problem. You can do this by referencing JBLs white paper on the subject, the final word on JBL polarity. See below;
 
http://www.jblpro.com/catalog/support/getfile.aspx?docid=241&doctype=3

Wow! I must say, I stand corrected. In fact, I've learned something new today. Thanks, Bob.

All of my hands-on experience with JBL cone drivers was with 2202, 2220, 2226, 2240, and 2241. They are all negative transducers, so naturally I thought all JBL systems were negative up until their most recent product lines. I never owned any of their MI speaker cabs, so I guess I couldn't see out past the rut I was in. The MPro boxes I now use for monitors are not mine, they are my bosses. They have never been opened or modified, so I never had a reason to check their polarity.

I will definitely bookmark that white paper. It may come in real handy some day. And I will watch what I say about JBL polarity from now on. Thanks again.
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Bob Leonard

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Re: Tweeter polarity
« Reply #19 on: April 06, 2011, 08:00:25 pm »

Wow! I must say, I stand corrected. In fact, I've learned something new today. Thanks, Bob.

All of my hands-on experience with JBL cone drivers was with 2202, 2220, 2226, 2240, and 2241. They are all negative transducers, so naturally I thought all JBL systems were negative up until their most recent product lines. I never owned any of their MI speaker cabs, so I guess I couldn't see out past the rut I was in. The MPro boxes I now use for monitors are not mine, they are my bosses. They have never been opened or modified, so I never had a reason to check their polarity.

I will definitely bookmark that white paper. It may come in real handy some day. And I will watch what I say about JBL polarity from now on. Thanks again.

Also note that the list will specify a model as well as individual drivers. In that case regardless of how the components are wired internally the cabinet is wired as listed. The OP's cabinets are an example of this.
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ProSoundWeb Community

Re: Tweeter polarity
« Reply #19 on: April 06, 2011, 08:00:25 pm »


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