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Clifton Hanger
07-15-2008, 03:00 PM
newbie poster here, who just picked up my first pair of E120's. I am replacing a set of Tone Tubbies in a 2x12 guitar cab.

I hate even asking this question, (because I am sure it is covered somewhere but I just got more confused on searching!:banghead:)

In wiring up these E120's I am am going to wire the 2 of them (they are 8 Ohm speakers)in parallel for an 4 ohm cab. I have heard that JBL's may have "reverse polarity" and that I should treat the red as negative and the black as positive, unlike any other speaker I have ever wired. Is this true?

I am using a 1/4 inch neutrik locking jack. What should I wire to the tip(Hot)? And what to the sleeve (ground)? Are these speakers really "backwards" for lack of a better term.

I guess really all I am asking is Which is positive and which is negative on these things!! :blink:

Sorry for the newbie question....Thanks!

Fred Sanford
07-15-2008, 05:54 PM
http://www.audioheritage.org/vbulletin/showthread.php?t=14501

Positive voltage to black = forward motion of the cone. Really only an issue if you combine the E120s with another brand/type of speakers at the same time on the same amp. Otherwise, just stay consistent with the two E120s.

I've got two E120s just waiting for a cabinet to call home...

je

Maron Horonzakz
07-16-2008, 07:18 AM
Why doesnt JBL mark the connecters with a + - and stop this crazy confusion...It couldnt cost them much to once in awhile think out of the box. and stop this nonsense.;)

boputnam
07-16-2008, 09:46 AM
Positive voltage to black = forward motion of the cone...... on vintage JBL drivers.

Clifton (and Maron, too) - you can always check your woofs with a simple test: Use short wires to connect a AA battery to the transducer terminals. (Current ;) ) convention is (+) voltage drives the cone out. Connect however is required to get that movement.

Fred Sanford
07-16-2008, 11:30 AM
... on vintage JBL drivers.

Clifton (and Maron, too) - you can always check your woofs with a simple test: Use short wires to connect a AA battery to the transducer terminals. (Current ;) ) convention is (+) voltage drives the cone out. Connect however is required to get that movement.

Bo, do you mean that there are some E120s in a 'vintage' arrangement, and some not? I was quoting specifically from the linked E120 spec sheet, do you know if they changed through the run of that model #?

I'd also advise that you only touch the battery terminals quickly, I've seen some people leave them connected longer than is needed to see the cone motion. In fact, I've watched them do that with a 9V battery instead of the 1.5V AA that Bo mentioned. :(

je

boputnam
07-16-2008, 12:28 PM
Bo, do you mean that there are some E120s in a 'vintage' arrangement, and some not? I was quoting specifically from the linked E120 spec sheet, do you know if they changed through the run of that model #?No, your remark was fine - I just wanted to make it more "specific" to all (er, most... :p ) vintage JBL.


I'd also advise that you only touch the battery terminals quickly, I've seen some people leave them connected longer than is needed to see the cone motion. In fact, I've watched them do that with a 9V battery instead of the 1.5V AA that Bo mentioned. :(
Yes, stranger things have been done. The 1.5v drive is plenty.

Clifton Hanger
07-16-2008, 01:22 PM
http://www.audioheritage.org/vbulletin/showthread.php?t=14501

Positive voltage to black = forward motion of the cone. Really only an issue if you combine the E120s with another brand/type of speakers at the same time on the same amp. Otherwise, just stay consistent with the two E120s.

I've got two E120s just waiting for a cabinet to call home...

je

Thanks so much for the clear concise answer!

Maron Horonzakz
07-16-2008, 01:38 PM
Bo,,, You miss my point,,, Its too late for the speakers out there now,,,So battery testing is nessary,,, But Damn cant JBL mark + - on future production speakers. ???? :biting:

boputnam
07-16-2008, 02:01 PM
...cant JBL mark + - on future production speakers. ???? :biting:Yes, JBL do mark their new issue transducers. Quite plainly. This, to avert legacy confusion... :)

Fred Sanford
07-16-2008, 02:52 PM
Thanks so much for the clear concise answer!

No problem. Stick around for the show 'n' tell after you've done the swap- we want pics, mp3s, and a full write-up...:applaud:

Something with P90s, maybe.

je

jcrobso
01-16-2009, 10:46 AM
Bo, do you mean that there are some E120s in a 'vintage' arrangement, and some not? I was quoting specifically from the linked E120 spec sheet, do you know if they changed through the run of that model #?

I'd also advise that you only touch the battery terminals quickly, I've seen some people leave them connected longer than is needed to see the cone motion. In fact, I've watched them do that with a 9V battery instead of the 1.5V AA that Bo mentioned. :(

je
When I got my first JBL D140F positive voltage on the red terminal moved the cone forward, but times have changed.
In general it is not a good idea to run DC voltage through a speaker VC, they are designed for AC. But a quick check is OK. The DC resistance of and 8 Ohm speaker is 3~6 Ohms. If you use a 9 v battery the current draw will be about 2 amps. I don't feel that this will do damage to a JBL woofer but it will drain the battery in a very short time, 9 volt batteries are not designed to put of 2 amps of current. Still I would not leave the battery connected for more that a second or two.
If one of the output transistors in am amp would short out it would dump the power supply voltage (40~80 volts depending on the amp power) this WILL fry ANY voice coil. Fortunately today's amps have protection circuity to prevent this from happening. John

edgewound
01-16-2009, 02:45 PM
When I got my first JBL D140F positive voltage on the red terminal moved the cone forward, but times have changed.

Yes...times have changed. Current production JBL transducers have followed the industry standard positive=red for a few years now.

If your D140F was original factory bone-stock when you got it, it should've been positive= black. Always has been, should always be restored that way too...in the interest of Heritage purity.:)



In general it is not a good idea to run DC voltage through a speaker VC, they are designed for AC. But a quick check is OK.

That's a great point, since DC has no frequency...ok....maybe 1/2 cycle.



The DC resistance of and 8 Ohm speaker is 3~6 Ohms.

Not always...sometimes it's between 6-8 ohms. 3-4 ohms would be closer to a 6 ohm nominal driver...and it would most likely be frequency dependent.

jnewmark
02-24-2010, 11:39 AM
Does this also apply to the K140 ? ( positive = Black )