Karaoke Forums

I've been in business for several years now and still haven't figured out how many
speakers you can hook up to an amp?  I use a yahama 8-88 (400X400 watts @ 8 Ohms) powered mixer with four Pr-15s and still seem to have a lot of head room.  I would like to have a couple of floor units for the singer. If two 8 ohm speakers give you 4 ohms per side, what do get with three 8 ohm speakers? and what do the watts do?

Don't think you wrote down the correct model number on the Yamaha mixer/amp.
Most amps can run comfortably at 4 ohms.  You already have 2 8 ohm speakers that drop the load to 4 ohms.  Now not being able to find any info on that number you listed 8-88, there is no way to tell if it can handle a 2 ohm load (the next rating).  If you add 3 8 ohm speakers you drop your load to approx 2 which unless the amp can run "stable" at 2 ohms, you will fry the amp.  
As far as watts, it will raise the power rating when you drop the load.  If your amp is rated 400 watts into 8 ohms, most likely at 4 ohms it can push anywhere up to 6-800 watts (again don't know for sure without specs).  At 2 ohms, the wattage will go even higher.
Now there are ways to hook up multiple speakers to 1 amp & stay within the proper load, but it does take much rewiring of speaker cables & hooking up in parallel AND series but this is generally very complicated for even some experienced sound engineers i've worked with.
Also, 2 8 ohm speakers handling 400 watts program power connected together will now be 4 ohms being able to handle 800 watts program power.

Here is a good website describing several speaker connections & options.

http://colomar.com/Shavano/spkr_wiring.html

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Here's the formula

Total resistance =               1
                         -------------------------
                          (1/R1 + 1/R2 + 1/Rn)


or RT = 1 / ((1 / R1) + (1 / R2) + (1 / Rn)).

Here's some additional information regarding wattage:How do I calculate Amplifier Output?

The calculation for figuring out how much is fairly straightforward, and pretty much what I would expect it to be. Since ohms measure resistance, the more ohms, the less output from the amplifier. Conversely, the less ohms, the more output from the amplifier.

Since the amp is rated at a specific amount of ohms (i.e 100 watts @ 4 ohms), a different amount of ohms will produce a different output. Two 8 ohms amps wire in series would cause the amp to produce 25 watts to each speaker.

Amplifier Output = Amplifier Watts x (Amplifier Rated at Ohms / Speaker Chain Ohms)
Amplifier Output = 100 watts x (4 ohms / 16 ohms)
25 watts = 100 watts x 1/4

Two 8 ohms speakers wired in parallel would cause the amplifer to produce 200 watts.

200 watts = 100 watts x (4 ohms / 2 ohms)

The amp produces 100 watts at 4 ohms. When the resistances is increased to 16 ohms, four times what it was rated, the amplifier produces one fourth as many watts.

You must be careful when wiring mutliple speakers together in a series or parallel chain because the amplifier may have trouble dealing with certain Ohms chain ratings, especially below 4 and above 16, and you must be sure that your speakers are capable of handling the wattage that they're receiving. Be sure to check the manaul for all of your equipment before doing any of this.

copied from http://www.marktaw.com/music/OhmsAmpsandSpeakers.html

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Thanks All! Great help.

Loneman, My amp is a EMX-88s, dug out the Owner's manual today and read it! as they say if all fails read the instructions. Looks like the way to go is a small powered speaker of some kind for the singer. I try to set up with one speaker facing back at the stage. But the one venue I have is a long nearow bar with low ceilings,tuff to get the sound where I want it. I belive the sound for karaoke should be just a good as any DJ has out there.

Yeah that's a little better.  Your mixer/amp only pushes 270 watts into 8 ohms (you had stated 400 watts into 8 ohms) & 400 watts into 4 ohms.  It's not 2 ohms 'stable' meaning you don't want to do it (ie 3 8 ohm speakers per side as opposed to your current 2 per side).  A small powered speaker would be better anyway, that way you can control the volume of it independantly from the main speakers.  It would connect in via the monitor out jack on the front panel.  To get the signal to the monitor, you'll turn up the monitor dial on each channel that you want in the monitor.  I believe that model also has a switch for mains & monitor as well.  
As far as sound goes, I agree however I prefer it to sound like a live show myself but that's my opinion.

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