Another ohm queston.

Discussion in 'Amps and Cabs [BG]' started by GreyBeard, Dec 16, 2002.

  1. I have a SWR Triad 4 ohm and a Hartke 115XL 8ohm I'm thinking of using together. My Eden VT-300A amp only has a setting for 4-8 ohms. If I run them in parallel that would be 2.66 ohms and if I run them in series that would be 12 ohms. Which combination and setting would work the best, or is this just a bad idea???
  2. ESP-LTD


    Sep 9, 2001
    Running them in parallel would be a BAD idea since your amp isn't built for it; it might self-destruct.

    Running in series the problem you face is that you have no control over the balance; the 4 ohm cab with take more power than the 8 does. Also, you amp will be pushing a 12 ohm load, and will have reduced power output. Solid state power sections have no problems with pushing a higher impedance load although tube amps may.

    I bet it sounds better just pushing the 4 ohm box.

  3. Well, the amp doesn't have a 2.67 Ohm tap so you would be mismatching the impedence a bit. If you use the 4 Ohm tap the mismatch isn't much. It's accepted that impedence mismatches of a factor of about 2 (double or half) aren't much of a problem. Running it this way shouldn't cause any trouble. Actually, with tube amps you're better off using lower impedences than higher ones when mismatching. Tube amps deal with shorts better than opens. You just won't get full power out of the amp. The 4 Ohm box will draw more current and therefore receive more power than the 8 ohm one. This may or may not work for you.

    Caveat: While this shouldn't cause any problems, there is an outside chance that it might.
  4. I'm gonna play it safe and replace the 15 in the cab with a Kappa 15 (4 ohm) and then run the 2 cabs in series making 8 ohms. It's just not worth risking damage to the amp. I'm sure that the Eminence won't sound the same as the Hartke driver, but, it should serve my purposes.
  5. geshel


    Oct 2, 2001
    It won't damage your amp at all to run it at 2.67 ohms - it's a tube amp. ESP-LTD was assuming it was solid-state.

    So now, the choice is: run in parallel, and have the Triad get twice the power the Hartke gets? or, put a new speaker in the Hartke, which may or may not sound good.
  6. ESP-LTD


    Sep 9, 2001
    Exactly! I haven't used tubes since my Ampeg Flip-Top. A pal plays with tubes exclusively and has measured the output stages to vary pretty widely in impedance, regardless of what the labels say.
  7. After reading several posts and doing some research I've found out that it is OK to mismatch on the lower side ( amp at 4 and speakers at 2.66 ) but not a good idea to mis-match with the speakers at 12 and the amp at 8. The way the Triad is wired is you have an 8 ohm 15, an 8 ohm 10 in parallel with a cap rolling off at 100 and the foster horn. Adding another 8 ohm 15 would lower the impedance to 2.66 and would probably match the volume of the triad 15 but not the entire cab. If not, I'll replace the 15 and wire it in series.:D
  8. Which is exactly what I said! :D;)
  9. You are the man Mark.....:)