Speaker stuff

[lrmars]

I have a 2x15 cabinet with JBL D130F speakers in it, wired in paralle for a 4 ohm load. I have another 2x12 cabinet with Eminence Legends in it wired also in parallel for a 4 ohm load.
I have read that the JBL's are wired so that the red terminal is negative and the black is positive.

When I hook both cabs up to a DUAL Showman head unit (4 ohm output tranny) I hear less bass than with just the JBL cabinet. Is it because the JBL's are out of phase with the Eminence speakers or because the amp is seeing 2 ohms???
I don't really understand what difference the color of the speaker terminals on the JBL's makes...lets say for discussion I merely paint the red terminal black and the black terminal red...I don't think electrons know what color they are going to...do they?

Thanks,
LRMars

[Bob-I]

Take a 9V battery, speaker wire plugged into the cab, and touch the + to the tip, - to the ring of the jack. The speakers should go thump and you'll see them move. They should go forward. If they go backwards, reverse the wires on the speakers.

JBL for some reason go the opposite way of most speakers so they have to be wired backwards. I never trust the color of the terminals.

[selloutrr]

If u have concerns as to phase of a driver touch a 9volt battery to the terminals the positive of the speaker to the postive terminal of the battery when the speaker pushes out it is in phase. The issue you describe with running both cabs could be strain on the OT or probably phase related if the phase for both cabs is the same then it's the OT.

[JD0x0]

from what ive heard the speakers dont care which wire go where as long as both of the speakers are wired the same way so they dont cancel eachother out. for example. Flip the wires on both the speakers in one cab. doesnt matter which, alone it will sound the same. But when you use both cabs (in theory) your phase problem should be fixed

[greiswig]

from what ive heard the speakers dont care which wire go where as long as both of the speakers are wired the same way so they dont cancel eachother out. ....

Speakers out of phase with each other will sound really crappy. But, FWIW, I put in a phase switch on an amp because I had heard that HAD might have reversed the phase on his cabinets and wanted to be able to do the same so I could get that "gen-yoo-wine" tone. I can hear a difference..and I prefer normal phase operation. It also changes how the guitar feeds back. Can't explain why they would be different technically, though.

[JD0x0]

from what ive heard the speakers dont care which wire go where as long as both of the speakers are wired the same way so they dont cancel eachother out. ....

Speakers out of phase with each other will sound really crappy. But, FWIW, I put in a phase switch on an amp because I had heard that HAD might have reversed the phase on his cabinets and wanted to be able to do the same so I could get that "gen-yoo-wine" tone. I can hear a difference..and I prefer normal phase operation. It also changes how the guitar feeds back. Can't explain why they would be different technically, though.

How would you explain the difference in feedback? i feel like my amp doesnt break into feedback as easily with a different cab and maybe it's attributed to the phase.

[solderstain]

You guys are missing the fact that the OP stated he uses BOTH cabs at the same time. In that case, phase ABSOLUTELY counts. Most of you guys are responding as though the conversation is only about one cab. It's not.

I've also heard (and verified) that (some) JBL speakers are wired the opposite of most other speakers. I found that out the hard way several years ago when my band replaced the drivers in our PA mid bins with JBLs and were vastly dissapointed with the results, until I checked with JBL and reversed the wiring so they were in phase with the hi and bass cabs (we ran tri-amped at the time).

Now, are ALL JBLs backwards? I can't vouch for that. But my GUESS would be that the answer is YES for stuff targeted at large SPL applications (and guitar amps certainly fit). The way it was told to me, the reason they do it is to protect the speaker from a very long cone excursion if it gets hit with an unexpected signal spike. They're wired to draw the voice IN (where travel is limited) on a spike instead of pushing the voice coil OUT.

So if I were the OP, and still wanted to use both cabs at the same time, first, I'd go straight to the source: check with JBL and find out if the speaker model I have is 'reverse-polarity'. If it is, then I'd simply swap the leads on the input jack of the cab with the JBLs. That would be the simplest way to put that cab in phase with the other.

[Structo]

In regards to speaker phasing, what if your amps speakers are opposite in phase of your bandmates speakers.

Would that have any bearing on how two guitars and amps would sound while playing at the same time?

Say if you both hit and open E chord, are the sound waves going cancel and sound bad?

I think it was Scott L. has discussed this before and said he can hear it if an amp it out of phase in regards to the way most are wired.

[selloutrr]

Structo. Two opposite phase amps same configuration and model same guitars and tuning equal distance apart in relation to the listener yes they would cancel but in reality no two are the same the amps prob aren't aren't equal distance so it would at most add phasing issues such as loss of select frequencies or the addition of combining frequencies. If is sounds thin flip the phase it doesn't matter if they both push or pull just so they all go the same way the speaker does not care

[solderstain]

Structo. Two opposite phase amps same configuration and model same guitars and tuning equal distance apart in relation to the listener yes they would cancel but in reality no two are the same the amps prob aren't aren't equal distance so it would at most add phasing issues such as loss of select frequencies or the addition of combining frequencies. If is sounds thin flip the phase it doesn't matter if they both push or pull just so they all go the same way the speaker does not care

Exactly. And since the other amps of the other band members are not reproducing YOUR signal, THAT phase conversation is completely irrelevant. The other peoples' amps will NEVER be in phase with yours - none of the amps are reproducing the same signal, never mind the different physical relationship from the listener. The only multi-speaker setup that is a concern for live setups like that are the PA columns, if you're using multiple cabs like my old band used to.

[greiswig]

Structo. Two opposite phase amps same configuration and model same guitars and tuning equal distance apart in relation to the listener yes they would cancel but in reality no two are the same the amps prob aren't aren't equal distance so it would at most add phasing issues such as loss of select frequencies or the addition of combining frequencies. If is sounds thin flip the phase it doesn't matter if they both push or pull just so they all go the same way the speaker does not care

Sorry, but I think I have to disagree: if you were feeding the exact same signal to both amps at the same time, yes, two out of phase amps might suffer phase cancellations. But unless you and the other guitar player are REALLY tight:roll: ...

The string vibration determines the initial phase anyway, so guitar players are almost always out of phase with one another to some extent. Try telling your background vocalist sometime that they're singing out of phase with you, and to get it right, and watch their expression. It doesn't matter because guitars are not putting out identical signals in the first place. Constructive and destructive phasing is part of what we hear as musical.

Interesting to hear about JBL using that out of phase thing as a way of preventing overexcursion.

[Bob-I]

Now, are ALL JBLs backwards? I can't vouch for that. But my GUESS would be that the answer is YES for stuff targeted at large SPL applications (and guitar amps certainly fit).

In my experience, every JBL I used in a guitar amp or PA was reverse wired. I personally don't think it has the effect described though. The issue I felt I had with JBLs in the 60's and 70's was non-linear excursion, not over-excursion. You can tell the difference examining the damaged voice coil. Over excursion is typically damaged at the edge, where non-linear excursion is damaged on the sides of the coil.

I felt that JBLs could handle almost anything you could give it, CLEAN. Add distortion, especally a nasty Big Muff style distortion, and they're give up in a few hours playing, even at power well under the rating.

I blew up JBLs so often that I kept the stock Fender speakers in the trunk so I could switch them between sets. After 4-5 recones, I switched to EVM and never again had a blown speaker.

[Bob-I]

Also, phase relationship is something that can be debated all day, and never come to s consensis.

IMHO the phase relationship between 2 guitars is not a factor. It would only take one guy to play an upstroke when the other guy plays a downstroke to cause the issue.

The single best way to test for phase relationship is to listen. I use the battery trick, which I wouldn't do on a cab with tweeters because they can't handle the DC. Once all speakers are front firing, I listen. Move around the room, side to side, front to back and listen for frequencies to drop out or come back on. It' really best to either play program music or have someone else play.

I've found that on multiple cab setups, moving a cab less than an inch, forward or backward, can create a phase related issue. This is especally noted on PA cabs.

I remember building a fairly large PA for the band in around 77. The soundman/engineer insisted that the speaker spiders line up, not the cones. The sub 15's he used were slighter deeper than the vocal range 15's but since we wanted one cabinet, we build a second baffle, out of 1/2" ply to move the vocal range 15's back and line up the spiders.

He demonstrated the effect by removing the baffle in one cab, and leaving it in the other. The one without the baffle had a noticable drop out in the low mids where the other one was even from top to bottom. He showed it to me on a spectrum analyzer but you could hear it easily.

He also demonstrated that this could not be fixed with EQ. He adjusted the EQ to compensate and the problem actually got worse, as if we were reading the analyzer wrong.

Bottom line, test with the 9V method on cone speakers only, not tweeters, then listen, especally with multiple cabs of different types (slant/straight).

JMO

[Structo]

Good stuff guys!

Yes I kind of figured my example wouldn't cause much trouble, I just wanted to hear why.

Phasing issues can get really complex in given situations.
Move one speaker back 6 inches, angle that speaker 20 degrees more to the right, etc.

I notice say on a home theater setup especially with the sub woofer that placement is the name of the game and depending on placement you can definitely hear the phasing.
That's why most quality subwoofers have a phase switch on back.
One way is going to sound louder with the other speakers but sometimes that is not the best tone, flip it the other way and it will sound tighter and less boomy.

I think mainly that phasing issues arise when the time constants are not right and you get standing waves and other anomalies.
Speaker placement and location being the most important.

I believe it was Scott that said he could hear when his amp and speaker were not in phase. I believe he said that when the speaker is not in phase with the amp that is sounds a certain way that he does not like.
His username speaks volumes, Dogears can hear it.

[Tonegeek]

Here some more on the subject of phase and its role in getting a guitar to "sing" and generate feedback. I am a believer now.

https://tubeamparchive.com/viewtopic.ph ... 37e35c586c