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JBLPRO
03-03-2016, 09:08 PM
Hello All,

Its been about 8 months since I completed my JBL 4355 clones. They are 99% perfect! The veneer trimming was a real challenge! I decided to build a CC version of the crossover as per Giskard and Timbers design. All the driver polarities are wired per JBl spec. Today I performed a polarity check on the entire system using the BSS AR-130 phase checker set. Very nice and very accurate piece of equipment. I used the sender signal via input of my preamp. Here are the results: 2235's -(negative) 2202's -(negative) 2441's -(negative) 2405 +(positive) I am not sure what the final polarity should be of all the drivers? All the SAME polarity or some 180 out of phase? I'm pretty sure at 10,000 hz( 2441-2405 x-over point) I will not be hearing this phase reversal but just wanted to know how they were originally setup and designed. BTW this speakers do sound very dynamic and have a beautiful soundstage!

NOTE: the 2405's are the Alnico versions. I am almost certain they have the original JBL diaphragms in them.
Thanks,

Mike Kehr

JBLPRO
03-04-2016, 11:42 AM
I just wanted to update my post from yesterday. It may have been a bit unclear. ALL drivers are moving forward with + voltage to the RED + terminal on the cabinet EXCEPT for the 2405. When the test was performed yesterday there was a phase reversal on the XLR-RCA adapter I used to connect to the BSS AR-130 sender to the preamp input. Pin 2 and 3 swapped resulting in a inward excursion of the drivers. So should all the drivers be of the same phase or some 180 out of phase. I have read that the 4350 had the 2440 wired out of phase to compensate for the position of the set back compression driver. Helping with time alignment per say...

Thanks,

Mike

JeffW
03-04-2016, 02:46 PM
Polarity issues on the 4 way monitors has driven a few folks mad. It might be easier to do a frequency response measurement and look for unusual peaks or valleys near the crossover points.

speakerdave
03-04-2016, 04:21 PM
http://www.audioheritage.org/vbulletin/showthread.php?774-4355-3155-clones

You may already be aware of this archived thread. I think that if you read it you will find the answer to your question and understand it as well.

I do have a question, though. What crossover are you using for the woofer/midbass handoff?

JBLPRO
03-04-2016, 05:13 PM
I am using a JBL/Urei 5235 for the active network. The unit has been modified with gold RCA's muse caps and updated opamps.