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 #91907  by lunasparks
 Sun Jan 09, 2011 11:46 am
I've searched the web but gotten massively conflicting answers to this question:

In my 2x12 cab I previously ran a couple of 16 ohm K120s wired parallel. One of the K120s died and I threw an 8 ohm E120 in its place, still wired parallel. I'm not running it with a tube power amp but with a Rocktron Velocity 300 (which I believe handles 4 ohm and higher loads).

My question is whether I SHOULDN'T be running the cab like this with mismatched ohm speakers? God forbid I blow up the speakers or the amp...what say ye?
 #91910  by JonnyBoy
 Sun Jan 09, 2011 2:20 pm
I have heard For the electrical system to work efficiently, the impedance should be as per manufacturing specs. What that means in my mind, if it says no less than 4 ohms, then 4 ohms should be the target. Although, 8 ohms won't hurt it if it need be, especially if you have plenty of headroom, since volume loss is the main by product. It will not hurt you amp to run your speakers that way, but two speakers with different ohm ratings, one will sound louder than the other. You can run them separately on the stereo lines to help compensate for volume that way. It should not hurt your amp to go higher with the ohms, but it will not be as loud and clear at lower volume settings. I think what most people like to do is keep their amp in that ohm zone where it gets the best performance, tone and volume, but it won't fry it unless you are running it hard under 2 ohms for a while. :smile:
 #91925  by strumminsix
 Mon Jan 10, 2011 8:07 am
Your poweramp should be fine. I think you'll be at a 5 ohm load at the poweramp.

Now where this will get weird is your volume. The 8 ohm speaker will be louder than the 16.
 #91934  by lunasparks
 Mon Jan 10, 2011 9:53 am
Thanks, guys. I feel more comfortable now. I do detect the volume difference. The E120 is a louder speaker anyway, so I wasn't sure if that was it -- looks like both factors at play making the E louder, I guess.

Here's one for you: I run the cab on the floor with slight tilt up. Any suggestion which speaker should be the one on the bottom? I read somewhere that because of "ground coupling" issues that the lower ohm/louder speaker (the E in my case) should be on top, with lower power on the floor. Tech-babble or do you think there's something to this?
 #91940  by lunasparks
 Mon Jan 10, 2011 10:28 am
strumminsix wrote:Louder speaker up for sure. Nuttin' too technical but no reason for the louder speaker to blast your knees vs up towards your ears.

Good enough for me. 8) Thanks!
 #94933  by zoooombiex
 Mon Mar 07, 2011 1:26 pm
this was sort of hinted at, but when you have an 8 ohm speaker and a 16 ohm speaker in parallel, the 8 ohm speaker will be handling double the load as the 16 ohm (rather than the speaker splitting it equally). just make sure the 8 ohm speaker can handle that wattage.
 #94937  by Pete B.
 Mon Mar 07, 2011 1:58 pm
You might consider running the speakers individually, from separate sides of your power amp, then match the volume by ear.
You may need a Y cord to split your signal to either side of the amp.