JBL E-120

JBL E-120

Postby sants » Mon May 10, 2010 7:34 pm

Looking at grabbing an e120 this weekend. I have seen disputed information on the topic of jbl polarity. Is the black positive and red negative on these? I am planning on throwing it into a Matchless Chieftain and don't want to mess it up
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Re: JBL E-120

Postby mijknahs » Mon May 10, 2010 7:49 pm

I believe the red is negative on a JBL but it actually won't hurt either way. I've run JBL E-120s the "wrong way" for years before I knew any different. Sounds pretty much the same too.

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Re: JBL E-120

Postby SarnoMusicSolutions » Mon May 10, 2010 7:59 pm

This is ONLY an issue of relative polarity. If the JBL is in the same cab/setup as another brand of speaker, then you'd naturally reverse one of them. We're dealing with audio, which is AC. That means that the speaker simply goes both directions. You can't harm anything by having one reversed. The only problem is that if you have two speakers that are of opposite polarity, then they'll be moving in opposite directions, and this does a lot of bass cancellation as well as weird phase cancellation. So don't be afraid to get it wrong. Also, if it's a one-speaker amp or cab, then it simply doesn't matter which way the speaker wires are connected to the terminals on the speaker.


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Re: JBL E-120

Postby playingdead » Mon May 10, 2010 8:20 pm

Is that really true, Brad? If the woofer is pulling in when it should be pulling out, wouldn't that affect the sound?

Mine were (both) wired backwards initially, and it sounded better to me when I switched, but it could have been my imagination.
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Re: JBL E-120

Postby ugly rumor » Mon May 10, 2010 8:24 pm

Brad's right.
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Re: JBL E-120

Postby playingdead » Mon May 10, 2010 8:32 pm

So, the speaker is out of absolute phase, but not necessarily audibly different.

Some interesting reading is out there about this subject; some say they can hear the difference, other's say they can't. Even some audiophile recordings recommend that you reverse the phase on your stereo speakers for better results.
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Re: JBL E-120

Postby Imagined Days » Tue May 11, 2010 5:02 am

black will be + and red -
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Re: JBL E-120

Postby NeebruM » Tue May 11, 2010 7:06 am

Just so you know, when the polarity of a speaker is unknown, momentarily connect a 1.5 to 6 volt battery to the terminals. When the cone moves away from the magnet, it means the + terminal of the battery is connected to the + terminal of the speaker.

And yes, out of phase speakers sound worse to me anyway...
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Re: JBL E-120

Postby strumminsix » Tue May 11, 2010 7:14 am

Most say they don't hear a difference as long as they are in phase but I certainly thought my amp sounded better once I correct the + to + and - to -.
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Re: JBL E-120

Postby JonnyBoy » Tue May 11, 2010 7:42 am

am I understanding this right, two speakers in parallel you go from positive post of one to neg of the other and the same for the other terminal? I have mine hooked neg to neg pos to pos then to the 1/4 plug.
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Re: JBL E-120

Postby ugly rumor » Tue May 11, 2010 5:10 pm

JonnyBoy wrote:am I understanding this right, two speakers in parallel you go from positive post of one to neg of the other and the same for the other terminal? I have mine hooked neg to neg pos to pos then to the 1/4 plug.



Parallel = + to + , - to - = ok, ohms = one half of impedance of single speaker
Series = + to _ to + to - = ok, ohms = twice impedance of single speaker

out of phase = + to - to - to + = bad, don't do this!

you are running parallel...A+ is your grade! your impedance is speaker "A" ohms divided by two (assuming both speakers are matched...have the same impedance, which is how it should be).

Speaker "A" = 16 ohms, speaker "B" = 16 ohms, you have 8 ohms of impedance in parallel
" " =4ohms, " " = 4 ohms, " " " " " " " series
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Re: JBL E-120

Postby JonnyBoy » Wed May 12, 2010 9:19 am

ugly rumor wrote:
JonnyBoy wrote:am I understanding this right, two speakers in parallel you go from positive post of one to neg of the other and the same for the other terminal? I have mine hooked neg to neg pos to pos then to the 1/4 plug.



Parallel = + to + , - to - = ok, ohms = one half of impedance of single speaker
Series = + to _ to + to - = ok, ohms = twice impedance of single speaker

out of phase = + to - to - to + = bad, don't do this!

you are running parallel...A+ is your grade! your impedance is speaker "A" ohms divided by two (assuming both speakers are matched...have the same impedance, which is how it should be).

Speaker "A" = 16 ohms, speaker "B" = 16 ohms, you have 8 ohms of impedance in parallel
" " =4ohms, " " = 4 ohms, " " " " " " " series





I use a 4 ohm 2x12 cab loaded with 2 8 ohm speakers in parallel, and I just bought a 4 ohm Black Peavey to make a 1x12 small bar cab. my amp has two outputs (not specified as stereo) for speakers, if hook up both 4 ohm cabs in separate "speaker out" ports does my amp see 2 ohms total or 4 ohms separately? Is there an external device that can change speaker resistance to bring it around 4 ohms? I will most commonly use it one cab at a time, but if I get a wild hair to get a stereo thing going will I most likely be frying my amp at 2 ohms? it is recommended 4 ohms or higher...
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Re: JBL E-120

Postby ugly rumor » Wed May 12, 2010 1:55 pm

The two "outs" on your amp are parallel outs. If you run both cabinets, your amp will see 2 ohms. If your amp is rated at a 4ohm load, do not put a 2 ohm load on it. You can run a dummy load, but there is no advantage and several disadvantages. First, ohms is more than just resistance, but impedance and inductance figure into the equation also. I would have to know more to tell you more about your specific situation. Tube amp or solid state, or hybrid? What are you trying to do?
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Re: JBL E-120

Postby SarnoMusicSolutions » Wed May 12, 2010 2:35 pm

The thing about audio waves, AC, and speaker movement is that the speaker moves equally out as it does in, and comes to rest in the middle. Polarity (absolute phase as some call it) reverses all over the place in a guitar rig. Simply switching from the normal channel on a Twin to the reverb channel will invert the polarity. Some effects pedals will invert the polarity. Switching pickups on many guitars will also invert the polarity. There are so many places that polarity gets reversed that its just a non issue. The only case I've ever run into where polarity matters is with Steve Kimock. He has a polarity flip switch installed on his Two Rock amp. He finds that under certain conditions he can feel the polarity from the amp as it hits him and hits the guitar. And since it varies from guitar to guitar, there's no one way to set it. Even the distance from the amp will change the effect of polarity. With a single JBL speaker, setting it one way is only one of many places that an audio signal can and will invert. By wiring black to positive does NOT mean that the speaker is gonna move "outward" when you play guitar. That's not how AC and audio work. The speaker is moving in AND out equally, and a picked guitar string is not a simple in or out kind of thing. It's a very complex waveform and transient. If you watch your speaker when you thump your strings, you'll see it go both ways, and good luck detecting which way it goes first. It's so fast and complex that you'll find it's not that simple, nor does it really matter. And just because you can flip the speaker polarity with the speaker connections, you still don't address the many other places that your signal polarity reverses. It could be just one of 5 or more places that your signal inverts. Then you switch from the neck to middle pickup, and you've likely flipped it again. Then you kick on your MXR distortion pedal and you've done it again.

Speaker polarity really matters when in relation to another speaker in the same system. That's an issue of relative polarity, and it does indeed matter. You don't want one speaker going one way while the other one is going the opposite direction. You want them moving in tandem.

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Re: JBL E-120

Postby SarnoMusicSolutions » Wed May 12, 2010 2:52 pm

NeebruM wrote:
And yes, out of phase speakers sound worse to me anyway...



The term "out of phase speakers" only applies to the relation between one speaker and another. You can't have a single speaker "out of phase" because it's has no defined phase relationship with another. The concept of phase is entirely relative. That's why it's defined in degrees... degrees out of phase from something else. So I totally agree, two speakers out of phase with each other sound awful and is instantly noticeable as wrong. But one speaker by itself with the wire terminals reversed (black to red, red to black) is NOT necessarily "out of phase".

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