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Tube amp Z question

Discussion in 'Amps and Cabs [BG]' started by bassmodder, Jan 11, 2009.

  1. Jan 11, 2009 #1
    bassmodder

    bassmodder

    Dec 9, 2006
    Sioux Falls, SD
    I have two 6 ohm hi-fi speakers that I would like to hook to my amp. My amp has 16,8,4 Z outs.

    My question is can I wire my 6 ohm speakers in series for 12 ohms and then connect the + to the 16 ohm tap and the - to the 4 ohm tap?

    My electronics training says yes but I thought I would ask here any way. I do intend to use the amp with my home stereo is why I am asking.

    I have heard the "lower is better" conversations but my amp really does NOT like this kind of mismatch. So much power is lost when I run on the 4 ohm tap with the speakers wired in parallel.. That's why I would like to try a different arrangement.
    Thanks!
     
  2. Jan 11, 2009 #2
    anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    Are you proposing your speakers ground wire connected to the 4 ohm positive or negative here?
     
  3. Jan 12, 2009 #3
    TrooperFarva

    TrooperFarva Guest

    Nov 25, 2004
    New City, NY
    What kind of amp are you using?

    You say that power is lost when you run the speakers in parallel, connected to the 4 Ohm output. How do you know power is lost? What are you comparing against?

    Also, what kind of speakers are you using? 6 Ohm speakers are rare.
     
  4. Jan 12, 2009 #4
    bassmodder

    bassmodder

    Dec 9, 2006
    Sioux Falls, SD
    Yes, I am saying I would leave the "0 ohm tap" with nothing on it. There would be a connection to the 16 ohm tap and the 4 ohm tap. The secondary on the transformer is all one winding with different taps on that winding.

    I have a Don mcgohan m503 PA amp. Had it for a couple of years and put quite some time into it restoring it to perfect operating condition.

    I am saying power is lost because I can hook up a single 8 ohm speaker the the 8 tap and get more volume out than if I use two of these 6 ohm speakers. The 6 ohm ones even have 8" woofers in them. So by non scientific conclusions I say the amp likes a pretty well matched load.

    If I put the right load on the 4 ohm tap- EX my bass guitar cabs (2x) or put two of my 8 ohm stereo speakers in parallel, she gets very loud so I know it is not my amp. I would have also quadrupled my speaker area.
     
  5. Jan 12, 2009 #5
    TrooperFarva

    TrooperFarva Guest

    Nov 25, 2004
    New City, NY
    I think you might be experiencing a speaker efficiency problem. If you wire the 6 ohm speakers in parallel, run them from the 4 ohm tap, and have volume issues, it's likely either a phase issue or an efficiency issue. The amp shouldn't have much of a problem with running a 3 Ohm load from a 4 Ohm tap.

    Have you checked the wiring on the 6 Ohm speakers to see if they're in phase?
     
  6. Jan 12, 2009 #6
    Rick Auricchio

    Rick Auricchio Registered Bass Offender

    Nov 27, 2007
    Cambria, CA (Central Coast)
    First, the hi-fi speakers aren't made to produce bass for an instrument amp. That's probably why they're terribly inefficient. And you'd soon tear them up anyway.

    I would NOT connect between the 16- and 4-ohm taps to get 12 ohms. You're making a naive assumption there based on some arithmetic, and you could damage the amp.
     
  7. Jan 12, 2009 #7
    T-Bird

    T-Bird Guest

    Apr 29, 2007
    Finland (Northern Europe)
    Hi.

    While it's possible that You actually have 6Ohm speakers, it's unlikely. If You measured the resistance and it was 6Ohms, those are most likely 8Ohm cabs.
    OTOH if You have restored the amp already, you probably know the difference between impedance and resistance ;).

    Do not leave the "ground" floating, it'll mess up the feedback loop and possibly makes the amp unstable.

    What I would do is to find some 8 or 16 ohm speakers to connect to Your amp. If the current speakers are the only ones You want to use, vintage horns for example, I'd reverse engineer the OT and find out just how much mismatch the wrong impedance causes.

    Running a tube amp with a load mismatch shouldn't cause too much power loss if not cranked, but the freq response might be a bit strange. Is that what You're describing?
    Even an ultra-linear shouldn't suffer too much.

    What tubes are You running BTW?

    Regards
    Sam
     
  8. Jan 12, 2009 #8
    BassmanPaul

    BassmanPaul Inactive

    Aug 25, 2007
    Scarborough Ontario Canada
    I agree with Sam, leaving the ground connection unloaded could cause you stability problems.

    Paul
     
  9. Jan 12, 2009 #9
    bassmodder

    bassmodder

    Dec 9, 2006
    Sioux Falls, SD
    They are Hi-FI speakers that would be used in a Hi-FI application.

    The speakers are labeled 6 ohms on the backs.

    Judging by the consensus and the amount of work put into the amp I think I will just get a decent set of speakers with a normal people impedance.

    Thanks for the input. Now I can justify the purchase:hyper:
     
  10. Aug 18, 2009 #10
    LarryR

    LarryR

    Feb 2, 2003
    Los Angeles
    bassmodder,
    I'm the new owner of your hand-restored McGohan M503.
    And I'm a happy camper I should say. PM'ing you if you don't mind.