I have a Taylor Big Baby - I installed a K&K Pure Mini (sounds awesome) - I bought a D'Addario Soundhole Plug - It works....sometimes. I play in a band situation and I cant afford a preamp system to go through right now plus I only play acoustic for 4 or 5 songs so it isn't really worth it to me. So I play with my amp rig right behind me and if I move away from the amp the feedback stops, is this what I am going to have to do or is there some other solution for me. I suppose I could go play on the other side of the room for those songs.
As long as the solution of moving allows you to still hear what you're doing, and be heard in the mix, it's certainly cheap, dirty, and effective.

Any other fix would be tons of money. For example, a parametric equalizer will remove a very narrow spectrum of the low frequency which is causing the feedback.

Many AE guitars designed for stage use have pickup phase reverse, along with low frequency cutoff filters, with variable roll off points, a bit akin to parametric EQ.

Ibanez goes this route with their "AEG" bodies. I have some good news, and some bad news. They sound great plugged in, not so good otherwise.

Extreme fix, stuff the body full of fiberglass insulation, (least recommended, to not recommended at all). Especially if you play the guitar at home or any place other than on stage.

Depending on the relative position of the PA speakers, (if a PA is in play,of course), you could send more guitar to the board, and set the amp just loud enough to hear what you're doing.
Last edited by Captaincranky at Feb 13, 2015,
If you're in a band you have a PA for vocals right? Plug the acoustic straight into the PA instead of a guitar amp, run it back through the monitors enough you can hear it. I've done it that way dozens of times with a sound hole baffle, almost never have trouble. I can run it through my Super Reverb without problems too, including with loud bands, but prefer to run through the PA.
Hmmm...I wonder what this button does...