Peavey XR800F 8 channel - I can't get but very little sound to my big speakers. Help

Certainly you could.

Is your graphic eq assigned to main and is kit set correctly?

When you unload one amplifier you stand the chance of killing the amp's output transistor. If you must use only one speaker, you have to bridge the amps.

Look for a 'monitor' switch, change it's position.

Bad output transistors or bad Soldier joint in output section

Yes, you can put two 8 ohm speakers daisy chain per side MAX. The Speakon should have ONLY two wires on the +1 and -1 terminals unless you are using bridged mode which is NOT applicable in your configuration of speakers. Also be careful is you use any 1/4 inch speaker plugs in the sytem as the SLEEVE, not the TIP of channel A is the "hot" lead... get this to ground someplace and goodbye amp.

Several things to do: Plugging into the tape type inputs... say the 7/8 channel.

The little button below the set you plug into needs to be pushed to the down position. This selects the "B" set which are the RCA jacks.

Below the set you are plugged into. Turn up the top knob "Gain" until the "clip" LED just isn't quite flashing.

At the bottom of that same column Turn up the "level" as needed for the mix.

Then of course, advance the Master level as needed.

There are SEVERAL things to set. First is setting the EFX mix for those channels you want the effects to be active. Next, select the effect you want AND the TIME for the effect and FINALLY the amount of the effect output to go to the MAIN and MONITOR outputs. Also the effect disable button below the effects needs to be in the correct state. ALL of these have to be set for using the effects on the mics.

Sorry, but this unit does NOT support "bridged" mode. You will have to drive seperate speakers from the two seperate outputs. You would NOT get any more power if you could do bridged mode than you could with 4 ohm speakers on each of the two output channels.

You will need at least a 24 channel mixer to give you spare channels. You also need an active crossover and a snake. The advice you need is too much to include here so I am including some links:http://mixonline.com/live/FixIts/, http://en.wikipedia.org/wiki/Live_sound_mixing, http://mixinglivesound.com/blog/tag/outdoor-concerts/,http://mixinglivesound.com/blog/, and http://www.scribd.com/doc/11435651/Beginners-Guide-to-Mixing-Sound. You may need more monitors than you are planning on and you might consider in ear monitoring.