When I use my Harte 3500 outside With 2 generic 8ohm 15s, it breaks up with the master on 2. I assumed it was the speakers. I've tried different volumes on the bass and amp and the 2 preamps and it doesn't help. I'm thinking of trying to wire the speakers in series for 16 ohms which should drop the amperage and volume. I need to do more research to make sure I don't blow it up.
I'm not sure that I'm following exactly.
When you say that you've tried "different volumes on the bass and amp and the two preamps," do you mean that you kept the overall volume out of the cabs about the same but changed the gain-staging (more master volume with less preamp volume, or vice-versa) or that, even at low playing volumes, you're getting that distortion (which you figure is from the cabs)?
Can you try the cabs with a different amp -- or the amp with different cabs? Do you get the same distortion when you try the amp with each cab individually?
Are you able to check the signal from the DI (pre- and post-EQ) to see if you're getting distortion there? You could record it or route it to another amp, powered speaker, mixer, monitor, headphones...
Particularly if you have an active bass, is it possible that you're getting some distortion from there? I once spent time with a cab builder, chasing down what I thought was a woofer farting-out when I hit a hard low "E" -- sounded like it, but turned out to be a waning 9-volt letting down my active EMGs (put in a new battery and, like magic, the speaker wasn't "farting out" anymore -- the clue was that the "farting" happened at the same level of attack when the amp was turned down as when it was turned up).
I'm not that familiar with Hartke amps -- and I don't know the power-handling or condition of your cabs -- but the HA 3500 is rated for 350 W @ 4 Ohms and 250 W @ 8 Ohms. Into 16 Ohms, you might only get 125, 150 watts -- I'd doubt much more than that.
If there's a problem with your amp, running into 16 Ohms is unlikely to fix it and, if you're simply overpowering your cabs, couldn't you just turn the volume down? (Again, I'm not entirely clear as to whether you're only getting distortion when you push the cabs to a certain level or at low volumes, too.)
If the speakers in your cabs are damaged -- or if the cabs are simply insufficient to handle your volume wants -- that'd be worth finding out. Depending on the cabs and drivers (and your EQ and the voicing of your amp), 350 watts into two 15s could be no big deal or more than they can comfortably handle. Either way, I don't know that series wiring would offer you a meaningful advantage over simply turning your amp down (and maybe reducing bass EQ or contour).
If you do look into series wiring (which wouldn't be my first resort), I gather from various reading on here that you only want to do it with identical drivers and cabs, as doing so with different cabs can introduce electrical weirdness that you don't encounter with parallel wiring.
Don't know if that helps -- I hope it does! Good luck!
