I have a Crown Power Base 1 AMP, with a buzz. It

If the mixer is still running and making the buzzing noise one of the electrical contactors is making the noise and should be replaced.
If the mixer is not running and just making a buzzing noise it can be because off single phasing, check the incoming supply to the mixer and make shore you get the right voltage to the motor (test on motor connection terminals)if the voltage to the motor is right the motor might be faulty

1 make sure its hocked up properly .2 see i if the protection comes on.. with out the speaker wires hocked up if it does the u have a bad amp.3 if the amp protection light is off with out the speaker being hocked up and after hocking up the speaker it comes on the u have bad wiring to your speaker or a bad speaker

If a cobra 29 as indicated here what are you using for power for it? If a base radio as indicated it also has a 12 volt connection--if no problem via the 12 volt connection the fault is in the built in power supply the radio has.

All "Base" radios have 12 volt connection and their own internal power supply to operate off wall voltage.

Could be a problem with the start windings.or start switch.maybe a capacitor .on the older models the start switch sticks just needs freed up and contacts on start switch cleaned.

The power amp is the final stage - the last output from the mixer goes to the power amps.
Its a routing problem - some mixers only allow certain routing and this could be affecting your FX routes.
All the FX - internal or outboard come before power.
Check the manual Check the aux send and returns Check if you need need stereo plugs for the send and return of FX.
Get back if still stuck.

just use the main left and right outputs of the behringer to run xlr (3 prong balanced) to 1/4 inch (looks like a big headphone plug) cables into the inputs of the crown amp. the mixer has the xlr outputs and the amp has 1/4 inch inputrs, sop the cables will have to reflect that on both ends. run the outputs of the amp (rca outputs, i believe, you may have to get a rca plug to 1/4 inch jack adapter, and then use a 1/4 inch speaker cable) to the inputs of the speakers, again, the amp has rca outputs and the speakers will likely have 1/4 inputs, so you will have to address that wil an adapter. have each speaker in its own channel.

Buzz is caused by a bad ground or interference in your shielding check out your cabling or plugs that is where the problem lies.

did you have "buzzing" Before these phones? Anything electrical fan etc on the same circut breaker of your house?. Or buzzing start recently with these already running. It sounds like your describing "electrical noise" and not really a issue with the phoned them selves. Try relocating the base if you have another open wall jack and on another circut. If you notice it goes away check whats all on that circut (wall outlet) that you unplugged the base from. depending on the noise or lack of at the new location it would probly be something running on there. ..
Hope this gives ya a solid start on a fix :)

There was never anything mentioned about the 18 yamaha sub in the hook up process

Send main 1 out to your Crown. Jump Mon send to PWR am insert.