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Hi, joel. Welcome to the Rumble Club.

You're in the right place to talk about Rumbles.
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We-e-ell, there's a whole lot more to electrical "efficiency" than just speaker cab impedance.
In general, the lower the total impedance load, the more power is "drawn" from an amp,
up to a point of diminishing returns. But, too many cabs makes too low an impedance and can burn up the amp! So, most amps are designed for safe operation in a fairly narrow range of impedance load, usually just 8 to 4 ohms. But, the Rumble 800 can also operate safely at 2 ohms, but
at no greater power rating than at 4 ohms. So, the big jump in power output is from 400W at 8 ohms to 800W at 4 ohms. There's no significant power jump from 4 ohms to 2 ohms, still "just" 800W. But there
can be a significant jump in sound pressure level, which
feels louder, by adding more speakers, and thus reducing impedance. Clear as mud?

It gets worse ...
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We-e-ell, with two 8 ohm cabs you can get
up to 400W
per cab! 'Cause two 8 ohm cabs gives a total impedance of 4 ohms. (The basic conundrum!

) And the Rumble 800 can then output
up to 800W, which is split into 400W per cab. But, just to keep it confusing, four 8 ohm cabs gives a total impedance of 2 ohms, but the Rumble 800 still outputs "just" 800W, which is then split into just 200W per cab. Yeah, not at all intuitive! Physics! Go phygure!
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No need to feel stupid, and please don't be offended. I think music and electrical science are as opposite as any other two right-brain/left-brain subjects that exist!
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Don't feel like the Lone Ranger, there, kimo sabe. You and probably 90% of all musicians, if they're honest. That's why we need to help each other in forums and "clubs" like this. Those of us more experienced try to help those with less experience. Then, when you're the more experienced, you help others. You said you've never used an impedance switch before. Someday you can help someone else in that same situation.
joel, show us a photo of your Rumble 800 and you'll get an official Rumble Club membership number and enjoy all the perqs and privileges thereof!
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