hello - wiring polarity question for old JBL bits

[Harkness]

hi all.. "first" post here.

actually, i did briefly participate some years ago, but have no idea what name i used then in order to re-register with the same name.

my question is regarding the phase correct wiring between an N400 crossover, a 150-4C and a 375 fitted with a 2397 horn (if that makes any difference). i am unsure of the relationship between the terminal connections on the N400 and the red and black terminals of the drivers.

can someone detail the way these 3 components should be wired to ensure absolute phase correctness?

thanks so much!

ps. if anyone is interested, my 150-4C's are loaded in piano black C40 Harkness boxes. i took the 375's out of the C40's, removed the 90 degree horns that were originally installed and now have them on top with the much better sounding 2397 horns. it's my understanding that finding a pair of C40's with 150-4C's and 375's is pretty unusual. a few years ago forumite Oldmics helped me obtain a correct replacement 2440 diaphragm for one of my 375's which came to me in blown condition. i suppose i should replace the other diaphragm in the other driver too, but i can't bring myself to break the wax seals!

[John]

Yes I have heard of this condition before??? The wax seal phobia:p

[Zilch]

Do you have an RTA?

Whichever connection produces the deepest notch in area of the crossover frequency is the wrong one, and it's specific to your particular driver setup....

[Harkness]

no RTA, sorry.

i have relied on my ears to wire them, but i would sure like to know the correct connection protocol.

[4313B]

1 and 4 should go to red on the drivers but you've changed the horns so you will need to determine correct phase at your normal listening position.

[Zilch]

Section 3-9 here: http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-5235%20manual.pdf

[toddalin]

no RTA, sorry.

i have relied on my ears to wire them, but i would sure like to know the correct connection protocol.

I went though this just yesterday when putting in 2235's. You don't need an RTA if you have a sound level meter and an function generator, oscillator, music keyboard, or even computer sound card.

What you want to do is play a simple tone (sine wave or flute) near the crossover frequency and measure the sound level. Switch the wires and try it again. The louder volume is the correct wiring. When I did this, wired correctly gives the loudest volume, followed by no horn at all, followed by an incorrectly wired horn giving the lowest volume. I did the same for the horn to the tweeter crossover with the same results. However, you can't do this by ear because the incorrectly phased horn is audible and the ear will trick you into thinking it's louder than with no horn at all!

[Harkness]

appreciate all the responses, thanks so much everyone. :applaud:

[smartpolo]

1 and 4 should go to red on the drivers but you've changed the horns so you will need to determine correct phase at your normal listening position.

I want to know where I can find this reading. Thanks!

[jim3860]

hi all.. "first" post here.

actually, i did briefly participate some years ago, but have no idea what name i used then in order to re-register with the same name.

my question is regarding the phase correct wiring between an N400 crossover, a 150-4C and a 375 fitted with a 2397 horn (if that makes any difference). i am unsure of the relationship between the terminal connections on the N400 and the red and black terminals of the drivers.

can someone detail the way these 3 components should be wired to ensure absolute phase correctness?

thanks so much!

ps. if anyone is interested, my 150-4C's are loaded in piano black C40 Harkness boxes. i took the 375's out of the C40's, removed the 90 degree horns that were originally installed and now have them on top with the much better sounding 2397 horns. it's my understanding that finding a pair of C40's with 150-4C's and 375's is pretty unusual. a few years ago forumite Oldmics helped me obtain a correct replacement 2440 diaphragm for one of my 375's which came to me in blown condition. i suppose i should replace the other diaphragm in the other driver too, but i can't bring myself to break the wax seals! Buy a red candle:p use as much as you want to refill.:rotfl: