powered mixer question

[omtayslick]

I have a Yamaha powered mixer. (EMX640) It has twin 200 watt power amps, and a selector for Main/Main, Main/Monitor, and Bridged. I normally run four 8 ohm speakers, 2 for mains, 2 for monitors. However, I would like to be able to use an external amp for monitors, (using 2 of my 8ohm cabinets) and utilize both of the Yamaha internal amps for mains via the Main/Main setting. My question is this: Will I get a full 400 watts from the Yamaha amps for mains, or will this power be reduced by impedance using 2 8ohm speakers for mains? Anyone know how this works on these powered mixers? The Yamaha manual is not clear on this matter.

 

[NRS]

Actually Yamaha rates that mixer at 200watts per channel @4ohms, (not @8ohms), which is how you've been running it already by using two pair of 8ohm speakers @4ohms per pair (Delivering 100 watts per speaker).

Switching to MAIN/MAIN will not change the internal amps power rating, it only changes what mixer section now feeds each amp channel, which will now be LEFT/RIGHT stereo signals from your MAIN section ONLY, freeing up your moniter section to be used with another amp. (It helps to always think of a powered mixers internal power amp as being completely sepeate from its mixer).

What changes your power rating however, will now be the fact that you will be using a single 8ohm speaker per amp channel and since an 8ohm load is usually rated at about 1/3 less than a 4ohm load, you'll now be getting roughly 140 watts per speaker @8ohms each. (Adding another speaker to each side will bring you back to the original 4ohm rating per side).

Bridge mode is the only exception as it is a function of the power amp and will combine the two amp sides into a single mono amp channel that will be about 1/3 more powerful than the sum total of them both, so the combined output in bridged mono will now be capable of a full 400watts @8ohms, but since you'll now once again have a 4ohm load from running a pair of 8ohm cabs off a single source, that will actually translate into roughly 530 watts @4ohms (providing over 250 watts per speaker).

Hope that all made sense

 

[mshilarious]

I have a Yamaha powered mixer. (EMX640) It has twin 200 watt power amps, and a selector for Main/Main, Main/Monitor, and Bridged. I normally run four 8 ohm speakers, 2 for mains, 2 for monitors. However, I would like to be able to use an external amp for monitors, (using 2 of my 8ohm cabinets) and utilize both of the Yamaha internal amps for mains via the Main/Main setting. My question is this: Will I get a full 400 watts from the Yamaha amps for mains, or will this power be reduced by impedance using 2 8ohm speakers for mains? Anyone know how this works on these powered mixers? The Yamaha manual is not clear on this matter.

The manual doesn't state power at 8 ohms in unbridged mode, but usually is it roughly half of 4 ohms. Right now you are running the mains at 4 ohms parallel load, so you have max power of 200W on the mains channel. You could use one cab in bridged mode for max of 400W, but that's only with one speaker, you can't use both because that would drop the impedance too low for bridged mode. If you run one cab in each channel in unbridged mode, you will probably get around 100W per side, same as running two in one channel. As I said, they don't state the spec at 8 ohms per side, so 100W is a guess. It could be 130W or something, but it's such a small difference I don't think you'd notice. On the other hand, it's probably good to distribute the load between the two channels rather than leaving one unused.

If you want a full 400W, you'll have to either get 4 ohm cabinets, 2 more 8 ohm cabinets, or 16 ohm cabinets in parallel in bridged mode. I would probably get 2 more 8 ohm cabinets myself; that way you could pick up some purpose-built wedges or mains, depending on what you already have.

 

[NRS]

You could use one cab in bridged mode for max of 400W, but that's only with one speaker, you can't use both because that would drop the impedance too low for bridged mode.

Actually, isnt the minimum impedance for most power amps while in bridged mode usually 4ohms? (Making running a single pair of 8ohm speakers while in bridged mode still plenty safe?) Although its bridged rating is indeed listed at 8ohms, I dont think that nessisarily indicates its minimum. Correct me if I'm wrong though.

Manufactures really need to stop this confusing ohms rating game and be required to list every product at both its 8ohm and 4ohm rating when applicable (which are your two most common real world configurations). 2ohm ratings of coarse are usually listed for sales hype purposes because they make the power specs seem higher that what most people would probably ever use the amp for.

 

[pandamonk]

I wish they explained all this on the 2 year course i just finished. So with a 1000w(at 4ohm) amplifier, you can run two sides at 500(if 4ohm speakers), but only about 250 each at 8ohm. I knew that. But if you have two 8ohm speakers on each side, it doubles up to 4ohm, and you can get 500w out each side? How would you connect this? Do you need speakers with an option to output, like a sub with passive crossover, or an amp with 4 outs(2 each side). I suspect the former... I don't understand about parallel and bridge mode etc.

Cheers

 

[boingoman]

Actually, isnt the minimum impedance for most power amps while in bridged mode usually 4ohms? (Making running a single pair of 8ohm speakers while in bridged mode still plenty safe?) Although its bridged rating is indeed listed at 8ohms, I dont think that nessisarily indicates its minimum. Correct me if I'm wrong though..

For pro amps it's usually twice the minimum rating for a single channel ie if each channel is rated for 4ohms, 8ohms will probably be the minimum bridged impedance. Don't take chances, follow the ratings, bridging at too low an impedance will cook an amp fast.

 

[pandamonk]

For pro amps it's usually twice the minimum rating for a single channel ie if each channel is rated for 4ohms, 8ohms will probably be the minimum bridged impedance. Don't take chances, follow the ratings, bridging at too low an impedance will cook an amp fast.

I'm not fully sure what the ratings mean to be honest. We'll i know you should get a higher powered amp than what is suggested for the speaker at that ohm(not by too much though). So for a 1200w(600w each) at 4ohm amp, you should get 2 400-500w 4ohm speakers... am i right?

But from what was said earlier in this thread, it seemed as if you could get 2 200-250w 8ohm speakers... What is meant by bridging? Could you explain, or point me somewhere that explains all about speakers and amps? Can you tell that I'm into actives, haha?

Cheers

 

[mshilarious]

But if you have two 8ohm speakers on each side, it doubles up to 4ohm, and you can get 500w out each side?

Yes.

How would you connect this? Do you need speakers with an option to output, like a sub with passive crossover, or an amp with 4 outs(2 each side). I suspect the former... I don't understand about parallel and bridge mode etc.

Either one. It looks like the Yammy has two outs per channel, those will be parallel connections. Cabs with two jacks are almost always parallel as well, unless somebody changed the wiring because they wanted to do series-parallel or something. But stock from the factory, those jacks are parallel. It's usually easiest to daisy-chain the cabs because normally they are spread in a line, or sitting in a stack. Either way, it's a shorter cable run than running a wire for each cab from the board.

 

[omtayslick]

Thanks for the replies. mshilarious' answers come closest to what I suspected to be true, but I thought I'd throw this out to the community to see if anyone could shed some light on this. Sounds like the easisest solution is probably a new powered mixer @ 500 watts per side.