Ohm ratings

[Sirion]

I have four 8 ohm Greenbacks (25 watters) that I play to put in a 4x12. I need it to be able to run in stereo and mono, with a Marshall 9100 power amp (50x50 watt). Of course, I am in the danger zone when it comes to what the speakers can handle, and I am aware of this.

A guitar technician I spoke with said that if I wired each stereo side in series, 16 ohms, I would be a little safer, since the amplifier wouldn't run as hot then. This suits me fine, because the amp can only handle 8 and 16 ohm ratings. So, basically, I need a 16 ohm for stereo and 8 ohm for mono, and each stereo "block" need to be wired in series. Is this possible to do with 8 ohm elements?

 

[Rich_S]

Re: Ohm ratings

Yes. You can wire each pair in series, and it will give you 16 ohms on each side. Then you need to set each side of the power amp to its 16 ohm setting.

The amp will not run any hotter or cooler regardless of whether its at 8 or 16 ohms. The important thing it to have it matched to the load, in your case 16 ohms on each side.

If you want to run this cab in mono, say with a normal 100-watt head, then run two cables from the amp to the L and R inputs on the cab. In this case you'll have your two 16-ohm pairs in parallel, for a total load of 8 ohms, so you set the mono amp for 8 ohms.

And it bears saying once again - you're really pushing your luck running 100 watts of Marshall tube power into four Greenbacks.

 

[Sirion]

Re: Ohm ratings

I know, I know. Unfortunately, I really love the sound of them! I will take my precautions though. I am 100% positive that I will not have to crank it, and I'm going to run an attenuator on each side.

 

[Rich_S]

Re: Ohm ratings

You've overlooked the obvious solution - you simply need a pair of 4x12's. :naughty:

 

[Sirion]

Re: Ohm ratings

I'm getting there, but then I'd need a bigger car to move my rig. It is a long term goal though :cool2: