TriAxis in stereo - disappointed/confused

[Jackie]

I decided to play mad scientist again and run my TriAxis into one half of the 2:90 and my Marshall JVM's "Poweramp In" simultaneously (and I was able to A/B the poweramps too).

So I set my 1960A cab to stereo and plugged everything in. I put the 2:90 in the left side of the cab, and Marshall into the right. Then I A/B'd both the poweramps and I liked both tones, they both had something different but none was better than the other.

The Mesa was Deeper, more low mids, cleaner sounding, looser lows (more resonant). Phonetically it would be a GROOOOOOHL sound.
The Marshall had a tighter low end, that midrange snarl that I like so much, it was a fair bit "filthier". Phonetically it would be a more "WRAAAAAAAANGH" sound.

I was all "holy **** this is awesome". Then I matched the volumes and I set both the TriAxis outputs to 6... and the sound was great and all, really full in the mids (the Marshalls mids and Mesa's low mids mixed perfectly like a puzzle), but my bottom end disappeared!!

Any clue as to what I did wrong???

 

[Screamindv]

Sounds like a phase cancellation. Take one end of your speaker wire and reverse the wiring on one end and listen. Here is a test you can do using a battery. To make sure all your speakers are in phase, unhook the speaker you want to test at the amp (both wires preferably). Using a 1.5 volt battery (any size), touch the positive terminal of the battery to the positive wire going to the speaker, then do the same for the negative wire. Have a friend look at the speaker. If the speaker pops out, the polarity is correct. If the speaker pops in, the speaker is hooked up backwards (out of phase). To fix this, simply reverse the wires when hooking the speaker back to the amplifier. A word of caution here: DO NOT hold the battery power to the speaker for more than 1 second, all you want to do is to see if it pops in or out. You will damage the speaker if you hold constant power to it. Do not use a higher voltage. Also, do not try this test on tweeters, you could fry the voice coils. If there are crossovers with capacitors along the line, this test will not work (capacitors block DC voltage). Bypass the caps momentarily.
Hope this helps

 

[allphourus]

I Agree that it seems evident that it's phase cancellation but it doesn't have to be speaker phase though that's the place to start. If checking Speaker phase does not reveal the problem, The phase could be being reversed in the amp, an extra pre-amplification stage in either amp could cause the same thing to happen .

 

[crane]

Mesa's poweramps like 20/20, 50/50 and 2:90 use an additional triod in input before the PI.
If the JVM poweramp input goes directly to the PI : you have your phase cancellation.

Edit : seems to be the case : http://jimcornelius.files.wordpress.com/2010/05/jvm210h_schematic.jpg

 

[Jackie]

Screamindv, I put the speakers the cab in myself and I'm 100% sure that they're wired correctly. Plus it doesn't cancel out when I put both channels of my 2:90 into one cab.

The phase could be being reversed in the amp, an extra pre-amplification stage in either amp could cause the same thing to happen

Mesa's poweramps like 20/20, 50/50 and 2:90 use an additional triod in input before the PI.
If the JVM poweramp input goes directly to the PI : you have your phase cancellation.

That's probably the case. Yes, the JVM's poweramp in goes in after everything into the PI.

Any way to fix this?

Stupid idea: would plugging it in the other loop's Return jack (the other loop can also be used as a poweramp in) help in any way?

Thanks for the replies guys!

 

[Screamindv]

Try reverse wiring one side of the cable going from one power amp to the speakers. Or reverse wire one side of the wire that goes from the triaxis to the marshall.

 

[ando]

Any way to fix this?

Dude, did you actually read the explanation from Screamindv? He's given you the solution! Saying your cab works fine with your 2:90 in stereo is irrelevant because we are talking about what happens when you use two different amps - with one being out of phase with the other due to its internal circuitry. Nobody is suggesting your cab is wired incorrectly or that you should rewire it. It's as easy as rewiring (reversing) one end of one of your speaker cables.

 

[Jackie]

I read it. He said "speaker wires" which to me means the cables connecting the speakers themselves, not the speaker cable. I also read the second one telling me to reverse the wires of my speaker cable.

I think that's a great idea and I'll get around to doing it. Problem is that speaker cable is scarce where I'm from and I'd have to make a new cable because I only have 2 and I need 'em both to use with my Mesa only.

 

[ando]

I read it. He said "speaker wires" which to me means the cables connecting the speakers themselves, not the speaker cable. I also read the second one telling me to reverse the wires of my speaker cable.

I think that's a great idea and I'll get around to doing it. Problem is that speaker cable is scarce where I'm from and I'd have to make a new cable because I only have 2 and I need 'em both to use with my Mesa only.

Do you have a soldering iron? If you do, it's very easy to try and then reverse again. If you don't want to mess with your good cables, I guess you'll have to order a speaker cable and get it sent to you. I always have a bunch of cables for experimenting. I never throw things away - just throw them in a box for old stuff. Nice to know it's all there. In your situation, I would make a temporary speaker cable using mains power cable and old mono guitar sockets. Mains wire is usually fine for a test cable and will tell you what you want to know. You could go to a HiFi store and buy a length of cable. I'm sure you'll find a way. Good luck.

 

[RJ2213]

hell if you really need the cable and have some old connectors or semi-faulty cables you can solder together a cable. hell at times i even used lamp cord, or cut a power cable of a piece of dead electronics and solder that for a speaker cable. just make sure the wire is decently thick and solder it onto the right connectors as needed. hell, i've been unemployed for a year, and still find cheap ways to improve my PA system and practice space. look around, see what raw materials you have, channel your inner MacGyver.