semi-hollow unplugged resonance/plugged feedback?

[HacksawLuthier]

Hi everyone,  new here, so maybe somebody already addressed this...

For my next project, I'm going to build a semi-hollow thinline-ish something like a B&G Little Sister, and I have a question about amplified feedback vs. acoustic (unplugged) resonance.

I was wondering if I ended the internal block just in front of the bridge, and braced the rear part of the top like an acoustic guitar, could I get a more acoustic sound out of the guitar without getting into straight hollowbody feedback problems when plugged in and (lightly) overdriven?

Most semi-hollows look like they mount the bridge into the back end of the center block (some images) and the pickups onto- or into- the block like a solid-body. Is most of the feedback smothering accomplished by the block damping the pickups, or does bolting the bridge to the block really do a big part of it?

... and if anybody has tried it, how much more hollowbody/acoustic sounding could it be if the bridge was just attached to a pretty resonant top (like spruce) but the top was still glued to the center block just a little ways forward. I assume the center block would still cut the resonance of the top pretty significantly, but would it just cancel it so bad it's not worth the trade-off?

Thanks for any advice you have!

~James

 

[Bizman62]

If you're going the trapeze way you'll have to somehow spread the spring pressure on the bridge to the body. The Little Sister does it by sort of having a solid body within the hollow one i.e. a center block. That allows for sturdy mounting of the bridge studs. Actually any type of bridge can be used with that construction - Tune-o-matic, wraparound, hardtail as well as all kind of tremolos. Depending on the bridge you can change the shape of the center block even down to a couple of posts sticking from the bottom.

If you want to lay the bridge over an acoustic top, a mandolin type wooden bridge is widely used on archtop hollow bodies. The top by itself is way too thin for drilled studs with just a mm wide collar. The wooden bridge can then have adjustable poles for a tune-o-matic bridge with a trapeze instead of a stoptail.

 

[Crusader]

I think the more accoustic a guitar is, the more feed-back prone it will be. With the question about the internal block personally I would stick to the norm to avoid any unforeseen problems

By the way do those Little Sisters have a flat top or a carved top?

 

[HacksawLuthier]

Thanks, you guys. Very good points. I looked at a mandolin bridge, and it looks like I would want to build an arch into the top to resist the inward pressure from the strings, or at least have some serious bracing inside, or both. I have to admit I just want the trapeze for style purposes.

I think the B and G's are flat top. Looks like it in the videos at the bottom of the page, and the pic of the routing of the back. They are mounting the bridge onto the rear-most part of the center block.

I just read somewhere that a whole bunch of rockers and blues players stuff their semi-hollows with foam to stop feedback, so maybe I'll just make sure the f-holes are big enough for future foam mods.