Mixing ohms

Wayne8 · #1 10-24-2010, 08:11 PM

I've got an old Peavey cab with an 4 ohm BW 15 and a Peavey 410TX that's 8 ohms. I love both cabs. I just picked up a Peavey Mark IV series 400BH. It says it puts out 210 watts at 4 ohms and 300 watts at 2 ohms. Now, if running two 8 ohm cabs would be a 4 ohm load, two 4 ohm cabs would be a 2 ohm load, would an 8 ohm cab and a 4 ohm cab together be a 3 ohm load? And is it okay to do that?

will33 · #2 10-24-2010, 08:12 PM

Quote:

Originally Posted by Wayne8

, would an 8 ohm cab and a 4 ohm cab together be a 3 ohm load?

2.67 and yes it's ok to do with a 2ohm stable head. The 8ohm cab will get roughly 1/3 of the available power and the 4ohm cab will get roughly 2/3.

Wayne8 · #3 10-24-2010, 08:39 PM

Great. Thanks! One more question. I will experiment and see how each cab sounds alone with this head and also together but I was wondering, if it puts out 210 watts into 8 ohms and 300 watts into 2 ohms, how much do you reckon it puts out into 4 ohms (the BW cab) and then how much would it put out into both cabs together (2.67 ohms). Roughly.

will33 · #4 10-24-2010, 08:43 PM

Somewhere between 210 and 300.

Really, that's getting to splitting hairs. You really have to double power or halve it to get a real noticable difference up or down. You'll make that rig louder by adding speakers to it.

Your 8ohm 15 by itself will be the quietest. The 4ohm 410 should be noticably louder but because it has more speakers in it, not because it's getting a few extra watts. Both together will be obviously the loudest but again because there are more cones moving more air. The 90 watt or less difference isn't going to matter much.

Selta · #5 10-24-2010, 08:48 PM

4x10 + 1x15 isn't the best mix of cabs, just so you know. Do a search here and you can find out why it can be less than ideal...

will33 · #6 10-24-2010, 08:51 PM

Sorry, I got your cabs backwards, 4ohm 15 and 8ohm 410. Your 15 will get about 2/3 the power with one speaker to absorb it all. The 8ohm 410 will get about 1/3 the power divided between 4 speakers.....The single 15 would be the weak link with a bigger amp but you're probably fine with that amp.

If you just want to guess at some wattage numbers for the hell of it call it 150 @ 8ohms, 210 @4ohms and 280 @ 2.67 although it really doesn't matter.

Wayne8 · #7 10-24-2010, 09:18 PM

Thanks!

Bassman1953 · #8 10-25-2010, 02:01 AM

And then of course you have to account the efficiency of each cabinet. That is how much sound pressure they can deliver per given Watt.