I got a used pair of JBL eon 15Ps for real cheap...since there is no 1/4" plug in on the speakers, to connect them to my mixer im running a 1/4" instrument cable into a female 1/4" to male XLR adapter into the speaker. This has been working but I'm finding here and there I need to run over and secure the connection because it starts falling out after a while.

Can I use a 1/4" to male XLR cable so I don't need to worry about the adapter to the speaker? I don't want to lose any sound quality though...what cable should I use?

Yes, you can use any connector without fear of loosing sound quality. The only time sound quality is sacrificed is when lighter cables are used. Always use the heaviest, and if possible, sheilded speaker cables available.

Good Luck,

Gary

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Travlin' Easy

The JBL EON15P are bi-amped/powered speakers, so no need for 'heavy' cables. Any good quality line/microphone cable will work fine.
The inputs on EONs are 'balanced' types, so try to connect them to balanced outputs. (3 wire : hot-cold-shield)

Most of the time jack-connectors cause signaldropouts because the contacts (tip-ring-shield) get dirty. Keep them as clean as possible with e.g. pure alcohol.

On my mixer the only outputs are 2 1/4" so I guess im forced to use this type of cable.
So this would be considered a good quality?
http://www.musiciansfriend.com/product/Horizon-HiZ-14-MaleXLR-Male-Cable?sku=336122

Or should I just stick with the adaptors? Im afraid of them loosening on stage...

This type is OK and MUCH better than adapters!
What is your mixer brand/type?
If it has non-balanced outputs you need a 'mono'jack. If balanced the stereo jack is a better choice.

The mixer is a Yamaha MG10/2 - http://www.musiciansfriend.com/product/Yamaha-MG102-Stereo-Mixer?sku=630048

It says 2 TRS sends. Does this mean it has balanced or unbalanced outputs?

Yep.. I checked the specs at Yamaha-site and they say the outputs are balanced.