Speaker Impedance help.

[scatterlight]

I bought a bass amp that is rated for 4 Ohms. Its a dual channel (Tube/Mosfet) amp.

 

Specs of the amp here; http://www.mesaboogie.com/manuals/Basis%20M-2000.pdf

 

My question is can I run 2 cabs rated for 4Ohms each? I have a very rudimentary knowledge about all this but I know that if I run 2x 8Ohms the amp will read this as a 4Ohm load. But I was wondering, since the amp is two separate channels, whether this rule applies? Or does the two channels involve just the pre-amp section and the power section must be counted as one?

 

If the latter is the case, and I cannot run two 4Ohm cabs,I was wondering how much do you think it will cost to get the speakers converted to 8Ohms? The reason I am adamant is that I have been offered 2 pristine ACME low Bs for half the price of a new one. I love those cabs and don't want to pass this chance up.

 

Finally, it is also written on the back panel that the minimum load is 2Ohms, which kind os lets me off the hook, but I was wondering if it was ok to run it at this (2Ohms) impedance on the long run?

I would appreciate any direction on this.

 

Thanks in advance,

 

Roshan.

[Rezrover]

Two channels, still one power amp. 4?'s the lowest you should go if you want your amp to last you.

[guitargod0dmw]

 

Or does the two channels involve just the pre-amp section and the power section must be counted as one? If the latter is the case, and I cannot run two 4Ohm cabs,I was wondering how much do you think it will cost to get the speakers converted to 8Ohms? The reason I am adamant is that I have been offered 2 pristine ACME low Bs for half the price of a new one. I love those cabs and don't want to pass this chance up.

 

 

That is correct. 2 channel, 1 amp.

 

You would need new speakers to change the impedance of the cabs, which would more than likely negate any cost savings you'd be getting on a good deal. It's not worth it.

 

 

 

Finally, it is also written on the back panel that the minimum load is 2Ohms, which kind os lets me off the hook, but I was wondering if it was ok to run it at this (2Ohms) impedance on the long run? I would appreciate any direction on this.

 

 

The manual states a 4 ohm minimum load is recommended. It's interesting that it says that on the back. I don't believe mine did.

 

Some Mesa amps can tolerate a 2 ohm load even though they say 4 ohm (Walkabout for example) but I have no idea if the M2K is one of them. I wouldn't chance it anyways, it would be all on you if something went wrong.

[isaac42]

I think it's pretty strange that the back panel says 2 ohms minimum, but they state repeatedly, even in bold lettering, that 4 ohms is recommended. Given that, I think I'd stick to 4 ohms, though if I happened to have some odd speakers around, such as the Sunn cabinets with 3 or 6 drivers in them that were rated at 6 ohms, I'd probably be okay with running two of those together for a 3 ohm load.

[Radar-Love]

 

 

Assuming you have a pair of Acme Low-B4 speaker cabinets, you might be able to rewire them internally from 4 ohms to 16 ohms.

 

Call / e-mail Acme to see if this is possible.

 

 

http://www.acmebass.com/indexA.html

 

[scatterlight]

First off, thank you all for the help.

 

The issue around the 'stated' impedance on the manual seems to be the confusion. In fact, if you were to enlarge the graphic of the back panel on the manual (Online, link provided) it says " Suggested load 4 Ohms, 600 watts RMS, minimum load 2 Ohms).

 

I am waiting for a Mesa tech to call me back. I hope this happens soon. I will keep you all posted on what they say.

 

Thanks again one and all.

[Rezrover]

Looks like they rate their amps like PA power amps, at a 2? load just to generate numbers. Most manufactures advise against running your amp(s) like that cause you're not gonna do it to limp through the last hour of a gig, you're gonna do it for the whole gig and that's like running your car engine at redline constantly which means it's eventually gonna fail.

 

See how 2?'s isn't even mentioned here? It's also a great way for them so sell more amps, if you blow them up.

 

 

[scatterlight]

"See how 2?'s isn't even mentioned here? It's also a great way for them so sell more amps, if you blow them up. "

 

I think you nailed it on the head Rezrover. The Mesa tech called back to say that its an "error" in the manual and that I should not use 2 x 4Ohm speakers. A bloody comfort getting this from the horse's mouth!!!! What if I blew the amp?

 

One last question. Will it affect the amp if I just run the one 4Ohm speaker, on the long run (If so, how best should I dial the back panel settings??). It says I will get 300w on one channel at 4Ohm. This is more than enough for me for the time being. But, I am a little concerned about doing this indefinitely.

 

Thanks again.

[Rezrover]

 

"See how 2?'s isn't even mentioned here? It's also a great way for them so sell more amps, if you blow them up. " I think you nailed it on the head Rezrover. The Mesa tech called back to say that its an "error" in the manual and that I should not use 2 x 4Ohm speakers. A bloody comfort getting this from the horse's mouth!!!! What if I blew the amp? One last question. Will it affect the amp if I just run the one 4Ohm speaker, on the long run (If so, how best should I dial the back panel settings??). It says I will get 300w on one channel at 4Ohm. This is more than enough for me for the time being. But, I am a little concerned about doing this indefinitely. Thanks again.

 

 

If I'm thinking what you're thinking, not using both output jacks isn't gonna hurt anything, the output jacks are more than likely wired in parallel and there is more than one because most speaker cabs don't have a parallel out wired in them. However you get a 4? load really doesn't matter.

[RSBro]

The M2K isn't 2-ohm stable. Others are, as have been mentioned, like the Carbine M6/M9, Walkabout, Titan V12, Big Block 750, later models of the M-Pulse 600. You weren't in serious danger of hurting the amp if you were to try it. You'd need to get it up to volume and sustain that before it just threw the thermal protection and shut off.

 

You will get 600W @ 4 ohms from that amp. The "channels" are referring to the preamps, not independent power amps. It's not like a PA-style power amp that runs independently on either side. I love and play Mesa but yeah their manuals are a lil out there at times... They've gotten better about it though since the M2K was released.

 

That's a great and very versatile amp. Did you get the footswitch with it?

[isaac42]

 

"See how 2?'s isn't even mentioned here? It's also a great way for them so sell more amps, if you blow them up. " I think you nailed it on the head Rezrover. The Mesa tech called back to say that its an "error" in the manual and that I should not use 2 x 4Ohm speakers. A bloody comfort getting this from the horse's mouth!!!! What if I blew the amp? One last question. Will it affect the amp if I just run the one 4Ohm speaker, on the long run (If so, how best should I dial the back panel settings??). It says I will get 300w on one channel at 4Ohm. This is more than enough for me for the time being. But, I am a little concerned about doing this indefinitely. Thanks again.

 

 

You're misreading things. The amp will deliver over 600 watts into a 4 ohm load, and should do so happily, indefinitely. There is only one power amp, so there is only one channel, as far as the power amp is concerned. As RSBro stated, the "channels" refers to the preamp, not the power amp.