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boogie troubles

Discussion in 'Recording' started by willjrockstar, Nov 25, 2006.

  1. i have a tri-axis and a mesa 2-90 and two stero recto cabs. whenever i run the a (or b) channel only its sounds perfect.thats one 8 ohm output into one 8 ohm cab.when i try to run the unit in stero,using one cab or two, the low end drops out drastically and the tone suffers. i havent tried switching all of my cables out yet but im willing to bet thats not it any way.
     
  2. RemyRAD

    RemyRAD Well-Known Member

    What you describe sounds like one speaker is reversed phase from the other speaker? But your description is not exactly clear? When you try to do stereo guitar, your guitar is feeding 2 amplifier heads?? You're using a passive "Y" split cord to do that? Or are you taking the output from one amplifier and feeding into the input of the other amplifier? That's not exactly stereo guitar unless you're doing something to create a stereo sound field? If you're simply feeding 2 cabinets which are only 2 speakers from a single amplifier, that's not stereo either. Your description is somewhat of a non sequitur.

    Can you get the phone? I'm a non sequitury and I don't do coffee.
    Ms. Remy Ann David
     
  3. what the hell is wrong with you. i said i was using a simul class 2-90.sorry when i run the A side and the b side of my amp at the same time.thats the stereo simuclass 2-90 bud.does that clarify?
     
  4. RemyRAD

    RemyRAD Well-Known Member

    Yes bud, that clarifies everything.
     
  5. Scoobie

    Scoobie Active Member

    To me it sounds like you do not have the output of the amp right. I'm sure that amp has 4 or 8 ohm outputs. When running two cab's have you used the 4 ohm output.

    Peace...............Scoobie
     
  6. yeah bro thanks for the get back.. that amp has two 8 ohm outs and four 4ohm outs. should that matter anyhow?i should be able to plug those things in any ol place back there without noticeable signal loss.this sounds major"ish". anyway to answer your question im running two 8ohm outs into two 8 ophm cabs,or two 4ohm outs into one stereo cab, or two seperate cabs.all the same ,plugging in any two cabnet combinations degrades the signal.using one sounds fine.
     
  7. moonbaby

    moonbaby Mmmmmm Well-Known Member

    FWI, Remy was right about this being a phase issue. I have seen this problem with Mesa, Marshall, and THD stereo power amps and cabs.
    Something is wired bass-ackwards. Don't be a dummy and think that the factory can't screw up (especially Mesa)-they can and do. You need to pull the grilles off of the fronts of the cabs so that you can watch the individual cone movements. Now hit a low "E" string (that's the real thick one you use to play Pipeline on). Watch the in/out movements of ALL of the speaker cones. Do some move in while the others move out? I'll bet they do. Make notes as to which ones do this and whether the cab is in mono or stereo. Start with them in mono. Let us know. I personally feel that you have a speaker cable (or jack on the cab)that is wired wrong, but...
     
  8. mesa troubles

    moon baby thanks for the reply, i can fully pick up what your layin down,but first off aren't those grill covers impossible to take off? yes i agree with both that something is out of phase.and its been in the shop more than once.i called mesa boogie,and they were real nice so im going to just send it back too them and let them deal with it. its under warranty ,so i may as well just let the "pros" go over the whole thing. besides im thinking there might be more wrong.anyhow i very much appreciate the input. i have a couple of days to mess with it so,if i figure out how to conduct the phase testing i will let you know how it ends. anymore suggestions?
     
  9. Scoobie

    Scoobie Active Member

    Do the test that moonbaby has told you to do on the speaker cab, I'm curious. I bought a Marshall cab along time ago and didn't like the tone it had, so I ended up taking it back.

    Moonbaby are you talking about them not wireing the speakers or jacks correctly, postive & negative.

    I have a amp that I run one or two cabs with and if I don't plug the speakers into the right ohm's ouput for the cab's. It's not near as loud.


    Peace...........Scoobie
     
  10. Tommy P.

    Tommy P. Well-Known Member

    Like Remy said, phase issue.
    Get a volt meter and test continuity of the speaker cables, and your line connection cables between pre and power amp before you ship out your gear and waste a whole lotta time and expense. Just test tip to tip, and sleeve to sleeve. If that checks out, then it would ...

    gotta be an input or output jack internally miss-wired in either the stereo pre or power amp, or an improperly wired A/B A+B selector in the pre. If you don't specify "out of phase sounding outputs" the techs probably won't catch it, especially in a busy shop, where these guys are expected to crank out X number of repairs per hour. They usually test one side at a time, and if it scopes ok, it goes back in the box to you.

    The odds are against the problem being the speaker cabs, because there's two of them that can each run in stereo....and all the config possibilities have been tried with the same outcome, right?. But as Moonbaby says, you should test them.

    Do the 9 volt battery test(get an old cable, cut off one end and intermittently touch it to the battery with the other side plugged into the cab) and observe the speaker cone movement. You can shine a small led flashlight thru the grill to see better.
     
  11. thanks guys im on it
     
  12. RemyRAD

    RemyRAD Well-Known Member

    The best way to conduct a speaker polarity/phase check, is to take both speaker cabinets. Position them within 1 foot of each other, face to face, grill to grill. If the sound all but disappears, they are out of phase to each other. Of course you must be playing something but you can play anything in the sound will cancel itself out.

    Conversely, if the energy of the sound gets larger, the speakers are in phase and you will definitely noticed plenty of bass sound. Out of phase... No bass. Zilch. Zip Time to reverse speaker connections.

    Unfortunately, the right way, is whatever way the manufacturer thinks is right. Which may not be right, but they think it is. Remember that little sticker you've seen in the past on some pieces of equipment? "Manufacturer reserves the right to make changes without notice". Man, have I run into that in the manufacturing end when I worked for Scully. Don't let me get started.

    I worked for Scully but I never saw Fox??
    Ms. Remy Ann David
     
  13. dear pannel,after sitting down to trouble shoot this amp problem you have all helped with, it didnt take long to find out what it was.a speaker cord that must have been wired incorrectly. i never suspected it coz when i used it by itself it worked.so after unpluggin everything and chekin it all out,thats what it was.the funny thing is that i stole that cord off a guy to replace one that he stole from me. i try not to buy any junk ,and i was lightly pissed when he took my top notch speaker cable ,so i took the nicest one he had in his bag.guess i see now why he took mine in the first place.bad move on my part.i think thats karma right?anyhow thanks for all your help,and sorry if i wasted your time.i know i learned a few things.my regards to all,,,JRock.
     
  14. RemyRAD

    RemyRAD Well-Known Member

    And so with a jury of your peers, we have all unanimously diagnosed, troubleshooted and repaired your guitar speaker dilemma!

    It's Miller Time!

    You're buying!
    Ms. Remy Ann David (ladies first)
     
  15. karbomusic

    karbomusic Active Member

    Looks like I'm real late on this one..

    Phase reversals are interesting to me so I'll chime in...

    First off I would offer the advice that any guitarist with a speaker cab test their setup. I've just seen too many mixups in cabs, wiring, cables you name it. Once you know its a phase issue here are some ways to diagnose what went wrong and where:

    There are two primary ways of testing that are pretty much definitive and accurate which is the 9volt battery mentioned earlier and also generating very low square or sine waves and sending them through the cab.

    9 Volt method:

    Test the inputs to the cab itself using a 1/4 speaker plug with no wire. Touch the + side of the battery the + post of the plug and - to - etc. If all four speaker move outward at once then the cabinet is wired properly. If any move backwards then their leads need reversing. Work your way back towards the amp. Do this for each cab. If they check out properly, separately and together with and without the cable(s) and things still seem out of phase then the amp is the culprit. (Assuming its mono going in)

    Sine Wave/ Square wave method:

    This method IHMO is the most definitive and can be used throughout the signal path for just about anything. You need to be able to generate a wave of appx 1 or 2 HZ. Yes, 1 or 2 and send down a signal path. In this case your amp then to the speakers. Take care setting gain and levels as accidentally sending a 2 hz square wave at full pop aint' gonna be good for the speakers. REALLY. You only want to send just enough signal to move the speakers enough to view their direction of travel. On second thought, stick with the sine wave, its not as extreme as the square one.

    You must be able to know when the wave is on the positive side. For example you generate the signal in Wavelab and observe the wave and watch the speakers to make sure their forward excursion happens when the positive side of the sine/square wave plays. This allows one to send this signal down very complicated signal paths in a studio and be able to confirm without a doubt that the signal is in phase at the end. Not just in phase but also that Positive = forward excursion. Depending on what items are in the path you can verify at each junction point. Very low levels must be used however as this would be quite damaging to speakers if not paid close attention to...

    Which reminds me of this old debate... If a studio was wired out of phase top to bottom so that it is in phase with itself. (everything reversed) Would it sound the same while within the confines of the studio??


    Karbo
     
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