JBL D140F Question

You brother's guess was a good one. If the speaker is going in the opposite direction, it's 180 degrees out of phase. Or to put it simply, you've attached the positive to the negative and vice versa.

Then when you changed the wiring on the input jack, you probably got interupted by a phone call and accidentaly put it back the same way you found it. It's been done before - am I blushing

 

I'm not a JBL expert, but I know that some JBL speakers were (are) phased opposite to the norm (majority). I once had a 1510 cab that I loaded with an EV 10 and a JBL E140, and the two speakers were out of phase using the red dots as indicating positive. I thought that EV had screwed up so I followed the JBL and reversed the EV. Then using a phase tester I found that my rig was out of phase with the mains (the mains made my stage rig "disappear") so I had to reverse both speakers in the 1510 cab. Someone who knows more about this will undoubtedly weigh in.

 

A number of JBL drivers use Black forward, compared to the more conventional Red forward. JBL publishes a list of which drivers do this, and is somewhere on my site in the JBL section.

The easiest thing to do is wire your cabs by swapping the cables at the speaker. Test with a battery and a speaker cable. Battery negative goes to the sleeve and positive goes to the Tip. When the Tip is made, the drivers move forward (away from the magnet).

If you make sure all your cabinets are Red Forward, you will be in phase with a new cabinet added later.

 

Thanks Bruce,
Hope you're doing well.
Gantt

 

Yep, and Chelsea is still pounding away on that D410XLT.

 

Here is the Link

You can reverse the wiring anywhere you want... speakers or the jack itself. What you want to wind up with is cab the goes Red Forward using standard speaker cables. Never use trick speaker cables, because if you trash one and have to buy a fast replacement, it won't be trick.

 

If it's any help to you at this point, my original Fender-labelled D140Fs are both "black forward" as bgavin stated.

 

OK back to basics.

Pulg the speaker cable in again. DO the battery test. Now do the battery test again but flip the battery the other way.

The speaker should go IN with the battery one way and OUT with the battery flipped. The only other possible outcome it NO movement at all.......

 

I've never done a battery test with an amp connected.......

OK forget the battery.

Set up your rig and plug in your bass. Connect one cab. Hit a low note on your bass. Turn the amp up intil you can see ths speaker moving. Which way is it going?

Now do the same with the other speaker. Which way is that one moving?

Now plug em both in. Which way are they moving now?

 

If you mean that you turned your amp on, and with no sound coming out of the speaker it simply moved in, then your amp is putting out DC, which is bad. If that's the case, then have the amp checked out.

If you mean that when you hit a note on your bass, it looked like the speaker moved in, then your eyes may be deceiving you, because it's going to move in and out pretty much the same amount, just like your bass string moves back and forth pretty much the same amount when it is vibrating from being plucked.

If the speaker just briefly moved in or out when you turned on the amp, that could just be due to a turn on transient thump - probably no big deal.

You're not really going to be able to tell the phasing of the speaker by playing through your amp, unless you do what was said above where you plug in a second speaker and see if the bass increases or decreases. Increased bass = in phase, decreased bass = out of phase.

And just because it's late, I'll go ahead and say that if you're having this much trouble figuring this out, you may need to take it to a tech. If you know you can figure it out, do some research on it and by-cracky figure it out.

Chris