Phase cancellation when running multiple cabs.

[diocide]

Hey, whenever I seem to run two of my cabs together (usually my Laney 4-12 and my Mesa 4-12) I notice a significant drop on bass response. With only one can hooked up, the bass sound is pretty huge, which the Laney AOR series are known for. As soon as I connect the other one, it seems like the bass response is literally but in half, out of both cabs.

Is it possible that this is due to some phase cancellation between the cabs? I can't really think of any other explanation, and after talking to my tech, this was the conclusion he came to. He explained that reversing the +\- leads on one of my cabs would be the way to test this theory.

Any of you guys ever experienced this? Just to be clear, both cabs have the same speakers within them (Fanes and Vin30's) and are definitely wired properly, and both sound great on their own or when used independently.

 

[Revson]

It'll never hurt to test, but it would be faster to reverse the leads on one end of your speaker cable.

 

[glpg80]

Phase cancellation is possible.

Take the back covers off of the cabinets so that you can see the cones clearly. Grab a 9V battery. keeping the polarity of the battery the same for each test, pulse the battery + and - to the cabinet input and simultaneously look at which way the speakers are moving - either inward or outward. Do not hold the 9V battery to the cable - pulse it. Make sure they are all moving in the same direction. Do this test with the other cabinet and make sure all of them are also moving in the same direction with each other as well as the other cabinet. This would mean that they are in phase with one another and with each cabinet.

 

[steve_k]

Is it possible that this is due to some phase cancellation between the cabs? I can't really think of any other explanation, and after talking to my tech, this was the conclusion he came to. He explained that reversing the +\- leads on one of my cabs would be the way to test this theory.

Your tech is correct. Do as he advises and see if it sounds different. Much easier to reverse the polarity on the cable than removing the backs.

 

[lettmusic]

Is it possible that this is due to some phase cancellation between the cabs? I can't really think of any other explanation, and after talking to my tech, this was the conclusion he came to. He explained that reversing the +\- leads on one of my cabs would be the way to test this theory.

Your tech is correct. Do as he advises and see if it sounds different. Much easier to reverse the polarity on the cable than removing the backs.

Great topic. i'm experiencing the same issue. How do you reverse the polarity on the cable? (forgive my ignorance)

 

[diocide]

Switching the phase of a cable is a get idea! Thanks for the suggestions guys.

Lettmusic; just unsolder one end of a speaker cable and swap the wires from ring to tip, and tip to ring. Pretty easy.

 

[Anonymous]

do the battery test first.

plug your speaker cable into your cab. leave the bare end. take a 9 volt battery. touch the tip to the + and the sleeve to the - on the battery. watch your speakers as you do this. if they all move out or move in, then they're all together wired in phase. but, each cab may be out of phase with the other. i'd check both cabs.
i like my speakers to move out, but, as long as they're all moving in the same direction, i'm pretty sure it dont matter.

if half your cab pushes out, and half pushes in, you need to get them all to match (either out or in), and, as i said, if you're running both cabs, they should match either moving out or in with a signal going through them.
it can be a pain if the wires are soldered to the lugs on the speakers and switches, but obviously, something that needs fixed.

 

[lettmusic]

Switching the phase of a cable is a get idea! Thanks for the suggestions guys.

Lettmusic; just unsolder one end of a speaker cable and swap the wires from ring to tip, and tip to ring. Pretty easy.

great, thanks a lot for the tip.

 

[freeballinusa]

I think switch a cable first easier to hear then see.....

 

[Anonymous]

I think switch a cable first easier to hear then see.....

the battery test to test your speakers is the best, quickes, easiest way to do it.

takes literally under a minute, and, you'll see your speakers moving, trust me.

if you didn't read my whole first post though, cause it wasn't under 140 characters or whatever other reasons, then you wouldn't see this.

to each his own though! good luck in your searches!

 

[Milerky2]

I found that phase can do strange things on a single cab too!

Story: Fellow Rig-Talker Drucifer plays at church with our band and has a Marshall Cab loaded in an X pattern with Warehouse and Celestion speakers. I like to get the different characters of both speakers in my mix, so I use a Sennheiser MD421 on one speaker, and an MJE K47 on the other... I found that while the cabinet was in phase, I had to flip one of the microphones OUT of Phase because the bass response just disappeared!

I tested the mics and cables and they were in phase, but found that in the use case I had, there was around 6ms of delay across the 2 mics, and that required me to change the phase of the mics. Weird.

So I concur, check the phase of the cabs, and keep proximity in mind when micing... your engineer will love you!

 

[Anonymous]

would that have maybe been due to frequency response rating on the speakers?

 

[Milerky2]

Maybe, but more likely attributed to the different mics on the same cab.