Not all systems are as revealing, but in any good system correct phasing is huge. I remember 30 years ago when I mis-wired a mid driver and heard the improvement first hand from reversing it's polarity. Years later I found out why!
Unfortunately crossovers shift phase and there is nothing we can do about it. A first order network shifts phase the least, but they don't always work well, especially with JBLs.
My first "known" polarity "issue" occured when I was building a custom LE14H/LE5-9/044 system. Once completed I A/B'd it with a pair of L96's and a pair of L112's. My "creation" sounded weird, bizarre, even frightening! A call to Northridge resulted in the "fessing up" concerning the incorrectly stamped + on the 044 frame
I changed the leads to the 044 and all was good.
In the Loudspeaker Components Series Instruction Manual from the late 70's JBL actually detailed the wiring of a phase reversal switch for use when wiring systems to facilitate A/B comparison of phase response.
My "first" was pairing some strongly recommended 4313B's with other cabinets - the result was awful. I almost turned the 4313B's away.
Instead I got the network schematic and after a few hours of dissection and testing, I grokked what was going on. Some quick Polarity Triage remedied the acoustic malady (for this install).
Now I know that "Negative is Good".
bo
"Indeed, not!!"
Geeeh! Now I'm really confused. I started out by wondering if the 2405 J is negative. It's not on JBL Pro's negative list, but so are the 2405H, and some of You clames it's the same speaker?! And what about when I use it with a 18 dB network, how do I connect it correctly? hmmm...
I'm also confused about the phase of the mid's in my L150's Should they be connected in, or out of phase?
Any help appreciated!
Hi Jakob,
The LE5 in the L150/L150A is wired out of phase with the rest of the system. The female terminal on the LE5 is RED.
As for connecting the 2405 correctly, according to JBL, phase doesn't count for much up in the range the 2405 operates but you can always use their fancy little phase reversal toggle switch to A/B and get it right.
Hey, Jakob...
I read on one other of the JBL .pdf's that the "H" designation signified 8-ohm, the "J" 16-ohm. I have seen that borne out on the few tranducers I have of like number and have H and J of them, but don't personally know the 2405.
You can see on that JBL Tech. Bull 12B partial listing of transducers that most H, and J of the same model are the same polarity. So, if it is only the question of impedence, my guess is the 2405"J" is negative, like the "H".
I've been warned about doing the 9-volt "click" test to compression drivers - it may overdrive it. Maybe someone (Giskard...?) knows if this warning need be heeded, or not.
"Negative is Good"
bo
"Indeed, not!!"
Well I was going to "recommend getting a dedicated 12 volt dry cell battery to test your polarity. It has to be a dry cell, they dump the necessary current required to clean out all the electrons that routinely hide out in voice coils." but then I realized someone might actually take me seriously...
9V is a bit much for smaller coils. It's "fun" and "ok" for abusing the 3 and 4 inch coiled LF transducers. 1.5V to 3V should be more than enough, and don't use dry cells at all.
I've always used a weak 1.5V battery and it never fails to move the coil.
As far as cleaning out those pesky stuck electrons, DC only works to a point. I find it is better to use a good clean 60Hz signal directly out of the wall.
At the risk of beating this in to the ground, I would like a confirmation on this polarity question.
My take on the JBL schematics is that the red input terminals send the + voltage to the crossovers, showing the signal the caps/inductors before it sees the drivers. This "crossover first/driver second" seems to be the recommended "direction" for proper results. So, to bring my JBL speakers (vintage) in to modern polarity convention, (+ voltage to red input terminal on the input board or crossover moves speaker forward), I would only have to switch the wires at each driver. Correct?
Thanks,
Tom
Correcto-al-mundo! Loosly translated that means correct all over the world...
ONLY at the drivers. And, by doing EACH transducer opposite of it's factory wiring, you'll be honoring the phasing between the transducers as intended by JBL engineers.
Think of the route of an active crossover - signal leaves preamp/EQ and courses through the active crossover then to the transducers. You could wire the transducers any way you want, but the networks need "see" the signal before the transducers.
But - again, unless you're pairing those gorgeous 4343's with a positive cabinet, it won't matter one Hz. But you will be in-phase with hearing aids! Ha!
Last edited by boputnam; 06-23-2003 at 07:34 PM.
bo
"Indeed, not!!"
from one of our International Correpsondents...
bo
"Indeed, not!!"
After reading this, I changed the leads on the (3) 2105s I have in the 3 L212s I built a 1 1/2 years ago so the mid range would be out of phase with the 112a and the 066. But when I checked the original pair of L212s that have the LE5-9s(that have male/female connects) the yellow/black leads, (-) according to the schematic, were connected to the male terminal. So If red is the same as female, then black is the same as male. So, the LE5-9s were wired in phase with the LF and HF, just the opposite of the above statement. So what gives?Originally posted by Giskard
Positive voltage to the red/female post on the LE10, LE5, and 066 causes the cone/dome to move in. No networks, just raw transducers. These are all what you call "negative" polarity transducers.
That is what I came up with when I checked a spare 066, and 2105
In the L166 and L212 the LF is wired "in phase" so the cone would move in. The LE5 is wired "out of phase" so the cone will move out. The 066 is wired "in phase" so the dome will move in. 6 dB/octave filters are used throughout.
Ahhhh....
JBl would not make it so obvious as that!And, I need to approach this non-sexist... :o , using only Red and Black.
We need to decipher the impacts of the network schematic. Funny things go on between the cabinet connection posts and the transducer binding posts...
The one Giskard knows this network better than I - and perhaps better that it's design team!I'll have a look at it tomorrow, but (at great personal risk!!!
) the HF is connected opposite polarity the rest of the "team". According to my read of this schematic (posted by Giskard) the MF is phased with the UHF. It's the HF that's on it's own...
Last edited by boputnam; 01-25-2004 at 09:34 PM.
bo
"Indeed, not!!"
Ok, let me think about this again.
RED input terminal to RED wire to #1
RED #1 to #3 to WHITE wire to RED post on 112 driver. Cone would move in.
RED #1 to #6 to YELLOW/BLACK wire with FEMALE end to BLACK/MALE tab connector on LE5 driver. Cone would move out.
RED #1 to ORANGE wire to RED post on 066. Dome would move in.
Nice to have you backOriginally posted by boputnam
Ahhhh....
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