Watts & Ohms Question!!!

[CliffD]

I've got a question for anyone who knows a lot about amplifiers in relation to speaker cabinets:

I have a Mesa/Boogie Walkabout head that is rated at 165 watts at 8 ohms and 300 watts at 4 ohms. If I run my walkabout through two 4 ohm cabinets drawing 2 ohms will it push more than 300 watts? Is this something I shouldn't do as the owners manual doesn't cover its power at 2 ohms? Thanks!

 

[i_got_a_mohawk]

If the owners manual doesnt say, the head is probably 4 ohm minimum. If that is the case, running at two ohms could fry the amp.

 

[LumpyGravy]

I wouldn't bring the value to 2ohms. 4ohms is a good place to be.
You could smell something burning in your power at 2ohms.

 

[RickenBoogie]

It's not recomended to run at 2 ohms, but alot of users do, with no ill effect. I was afraid, at first, but do it occasionally now. The trick with running a Walkabout at 2 ohms is to not push the master volume past halfway, (12 o clock). The amp won't fry, it has thermal shutdown protection. If it gets too hot, it'll shut itself off. Just don't let it get hot, keep the volume reasonable, and yes, 2 ohms = 500 watts. Great little amp.

 

[rpsands]

Definitely possible you will free your magic smoke at some point doin that

 

[RickenBoogie]

Search the Walkabout mega thread for convincing evidence to the contrary.

 

[CliffD]

Gracias, I appreciate the help.

 

[Fretlessboy]

call Mesa if in doubt

 

[JTE]

Can you? Sure you should be able to. But there are risks. MESA specs it at a 4 ohm load becasue if they state its 2 ohm output, then the UL listing requires that it operate at that load for a certain time without generating enough heat to potentially cause a fire. So they don't. Same reason Fender didn't rate their Bassman 200 combo at 2 ohms even though they had a 4-ohm load in it and an external speaker jack.

What happens when you operate an amp into a lower impedance is that the amp will work to put out more power. But you don't get something for nothing, so the current increases. "Current" is the number of electrons passing a point in a specific time. Thing is that electrons also cause heat when there's a lot of them squeezing down the same wires. While I imagine that MESA has an excellent thermal protection circuit, understand that you are running the risk of thermal shutdown in the middle of a gig. And understand that components fail. Maybe one of the output devices on your amp is more heat sensitive than its specs say it should be. Or maybe the thermal circuit breaker on yours decides today's the day to stop working. It is posible to overheat the amp and cause catastrophic failure.

So, do like Dennis says, and contact MESA Engineering to see what the warranty people say about running the amp at 2 ohms.

jte

 

[CliffD]

Thanks, I called and left a message with Chris in their technical help department, we'll see if they respond...