Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #79861  by hogan
 Wed May 12, 2010 3:00 pm
It should be noted that a single speaker cab can be out of phase w/ other cabs in an array, i.e. other bandmembers rigs. That further demonstrates what Brad is saying. You need more than one speaker to be "out of phase". The good times start when deciding which dude in your band is the culprit.
 #79872  by ugly rumor
 Wed May 12, 2010 6:17 pm
Actually Hogan, it would only be that way if everyone used the same amplifier. Different amps each pushing speakers in phase with the other speakers that amp is also pushing would have no effect on any other amp and whatever it is doing. That's a convoluted way to say that each individual amp is responsible for its own speakers, and doesn't have to be in phase with the speakers from other amps. Each exists in its own universe. That step is for each amp alone, in other words, to paraphrase.

Sarno is dead on.
 #79880  by JonnyBoy
 Wed May 12, 2010 10:48 pm
When I was building my buffer there was a circuit to invert the signal if that was something I wanted done. Then I found it to be in almost all the schematics as an optional circuit, sometimes it was written in as a part of it without option. In terms of pedal building, that seems to be a common thing to happen.

Ugly rumor- I now see if I want to use that speaker I would have to do a parallel series hookup as a three speaker setup. I really don't need 3 speakers EVER with the JBL E 120 style speakers I use. 2 of them are plenty ear buzzing. I wanted to use a 150 watt Peavey Black Widdow JBL styled 4 ohm speaker as a lower volume rig. clipping sounds so nice on a 2x12 pushing some watts. I have yet to see what this speaker will do at lower volumes.

Brad-- Does the Black Widdow break up easily?
 #138220  by Bobbybriand
 Fri Apr 11, 2014 11:08 am
As Brad said the polarity can get changed several times before it hits your cab or combo pair. Atleast you can do especially if your mixing brands in your cab is make sure all the speakers polarity are known. You can do this with the 9volt battery trick. If you hook the + on the battery to the red on a speaker and the - from battery to the black on the speaker . If the speaker moves out the red is pos and black is neg. On JBL's when doing this test on my K's and E's it is opposite. The red to + and the black to neg. move the speaker inward hence Black connector is pos. and red connector is neg.
Wonder if any other speaker companies do this with their red/+ n black/- connectors. Also what is the purpose?
 #138221  by James-T
 Fri Apr 11, 2014 11:58 am
Great post Brad! Or should I say professor Brad. If I have a 15 ohm load on one speaker jack in my Vibrolux and a single JBL E120 on an external cab on the other jack so mow I know now I get about a 4 ohm load. Question for the group. Does it matter on the JBL what is positive or negative or is it not possible for an extension cab to be out of phase with it's mother combo amp?

And BTW I'm digging the E120 with the Vibrolux. I'm pretty sure it's out powering the two Celstrions so my question is perhaps mute but still an interesting one. You'll love the E120 when you get it.


 #138224  by tatittle
 Fri Apr 11, 2014 2:02 pm
Interesting to hear experienced folks say 1 speaker doesn't matter. I swear I heard a difference in my Princeton (single 12" JBL). I use the battery test: hooking up a 9V battery to the speaker terminals (and removing), the positive side of the battery connective to the positive terminal of speaker will flex the speaker out towards the front of cabinet. It will stay flexed until you remove the battery.

I don't doubt that technically it doesn't matter with only 1 speaker, or that there are many more factors which come into play. I also don't doubt that the single speaker seemed to produce less volume wired with + from amp to - on the speaker. Maybe one of my terminals is just dirty or it is in my head. "Feelings" often bear little relationship to objective reality...but I hook up + to +, even if merely to make me feel better. :cry:

If the JBL has been reconed it may no longer be BLACK = positive. I think the newer JBL's have switched to the industry standard RED=positive; not sure if the E120's ever had this switch though.
 #138252  by Bobbybriand
 Sat Apr 12, 2014 5:51 pm
Huh gonna try the battery on my K's. Ive been running Red to COM on E's and Red to Shield from Rocktron on my K's.