Is it possible to run Two cabs with different Ohms ratings from the same amp?

[turn_up_the_tele]

Hey guys. I have a question that I am hoping someone might be able to answer. I want to be able to run two cabs from one head. However one cab is 16 ohms and the other is 8 ohms. The head I have is switchable between 8 and 16 ohms, but i want to know if it possible to run both. I am hoping there is some sorta of pedal that would let me do this, because I want to be able to switch between the cabs during songs and such.... any replies would be greatly appericiated...

thanks
mathew

[Dacious]

There is no 'pedal' you could buy which would do this - because it would also have to switch the amp's impedance between 1 cab and the other. Also, any mechanical switch which could take the voltage/current of say a 50watt amp while it's playing would need to be pretty beefy and make-before-break so your amphead is not left instantaneously without any load.

Running two cabs of different loads is going to provide uneven results, because the higher-impedance cabinet will not receive the same 'power' output as the lower impedance unit.

If your amp puts out 50 watts on the 8 ohm setting, into the 8 ohm cabinet, it will put out probably 30-35 watts into the 16 ohm cab on the 8 ohm setting. Some amps like Fenders will do this all day long. Some other amps it is not at all recommended as they run much closer to the wind with regards to their power sections.

Why do you want to switch between cabinets? Switching between channels, or even between amps - sure. But cabs?

[6942]

Dacious is dead on here.
Loading an amp can be real dicey.
Play on the safe side, and stay close to the manufactorers specs.
Frying an amp is an expensive lesson.
Steve

[Volvoguy]

I'd check out Radial engineerings offerings.
Cab-bone could work for ya

http://www.tonebone.com/tb-cabbone.htm

[turn_up_the_tele]

hey guys , thanks for the great info.... that cabbone might do the trick....

Dacious, its not so much that i want to be able to switch between the cabs, I am more interested in running both the cabs at the same time..

thanks

[Dacious]

The answer is still not recommended. Electricity is like water - it takes the path of least resistance. So if you have two loads in parallel and one is half the resistance of the other, it will get some proportion of between 50 and 100% of the output transformer's secondary (speaker lead) output - probably closer to 80 or 90%. So one speaker box will still take most of the power - the other one will probably be barely noticable.

The other issue is that output load of parallel speakers is (Ztot) = Z1 x Z2/Z1 + Z2 where Ztot is total impedance, Z1 is one speaker box and Z2 is the other.

or 5.333 = 8 x 16 /8+16

Unfortunately, you don't have a 5.3333 ohm impedance setting. If you had a 4 ohm setting you could use that, likely safely. But the 16 ohm cab won't see much business.

You could wire the cabinets, a juntion box or the head so you run them in series on the head's 16 ohm setting - then they will each get similar power, but the total impedance running series is

Ztot=Z1+Z2

or

24=8+16.

Again, your head does not have this setting and it will alter freq. response and total power to some degree to run on 16 ohms with a 24 ohm load.

[tiktok]

Mesa had a thing called the amp switcher which would let you switch between multiple heads into the same cab and vice versa (I believe), but as I recall they were on the pricey end (around four or five hundred dollars), sort of heavy and a rackmount device to boot. And Radial has the Cabbone:

http://www.tonebone.com/tb-cabbone.htm

I could see cabinet switching being useful, but my experience in using mixed cabinets at the same time was that if one was much more efficient, it totally dominated the sound, and there was no "blend" option to vary how much you heard of each cabinet. If you were mic'ing them in the studio, it's not a problem because you can assign each cabinet its own channel and vary the blend during mixing, but for live use it was more problematic.