Building a guitar around a pickup

Subject: Building a guitar around a pickup
From: Will Fly
Date: 04 Jul 13 - 05:12 PM

I bought a De Armond pickup in the late 1960s - you can see the sort of thing I mean here - and had it for years on my old Epiphone Texan. When I started using full electric guitars, I took the De Armond off the Texan and stashed it away in a drawer - where I came across it a few months ago.

Now, this was a great pickup - and you can see from prices on eBay that even old ones hold their value. So I decided that I would use it again - but this time would have a guitar built around it - just for fun. My spec for my luthier buddy, Ian Chisholm, looks something like this:

- mid-jumbo body shape with rounded single cutaway but half the depth of a normal acoustic
- round soundhole with the De Armond fitted permanently across it - jack socket in underside of lower bout
- mahogany neck and ebony fretboard with side and face markers at 3, 5, 7, 9, 12, 15 and 17 (Ian's fretboards are normally blank
- body wood to be chosen for visual over acoustic qualities (maple and spruce to be precise)
- Lowden-style rosewood bridge with no bridge pegs - strings run directly through from behind
- clear pickguard
- hardwood edge to the soundhole (normal on Ian's guitars)
- stainless steel Schaller or Grover tuners fitted to "snake" headstock

The guitar will not be acoustic but will have the lightness of an acoustic with slightly more than the body depth of an electric. It will double for playing in both the ceilidh band and my jazz duo.

I wanted something very different from my usual guitars - and Ian likes a challenge in making something out of the ordinary - so we'll see how it turns out. Can't wait to plug in and turn up...

Subject: RE: Building a guitar around a pickup
From: Stanron
Date: 05 Jul 13 - 07:59 AM

This sounds really nice. Ask him if he has heard of or used Lyptus wood. It is a fast growing wood grown as a crop and is described as looking like mahogany.

Subject: RE: Building a guitar around a pickup
From: Will Fly
Date: 05 Jul 13 - 08:13 AM

Lyptus - never heard of that one - I'll mention it to Ian and see if he's heard of it.

Subject: RE: Building a guitar around a pickup
From: Uncle Phil
Date: 05 Jul 13 - 03:34 PM

As it's not intended to be played as an acoustic guitar, have you considered sealing up the sound hole behind the pickup, making it an airtight box, to cut down on the chance of feedback?
- Phil

Subject: RE: Building a guitar around a pickup
From: JohnInKansas
Date: 05 Jul 13 - 04:05 PM

If you wanted to experiment a little, cutting the depth of the body in half will reduce the internal air volume to 1/2 that of a normal acoustic guitar. Starting with a soundhole with half the free area of a normal acoustic guitar with the same body outline should bring you close to the "air resonance" frequency response for a full depth one. The body outline will likely make the "plate frequencies" of top and bottom similar to a conventional one. The reduction in air volume will likely reduce acoustic volume/amplitude a little, but a smaller sound hole might give a more usual "sound" and the pickup can take care of the difference in energy output.

Since the pickup mounts in the soundhole (?) it will block part of the opening and you'd have to calculate [hole area - pickup area] and possibly use an oval hole to get the appropriate Helmholtz frequency with sufficient hole width for mounting the pickup.

If you don't like what you get, you can always trim off a little wood to make the hole bigger, but taking off some wood to make the hole smaller doesn't work too well. IFF you decide to experiment, of course you'd want to do any trimming/tuning before you add the purfling etc.

Some builders get obsessive about matching "air resonance" with "plate frequencies" for the body parts, and others say it doesn't really matter all that much for a guitar, so deciding what - and how much - to play with the design usually depends mostly on the spirits and gremlins afflicting the builder. Of course the buyer should get to express an opinion too - sometimes, but arguing with a guy who does good work isn't something to be strongly encouraged.

John

Subject: RE: Building a guitar around a pickup
From: Will Fly
Date: 06 Jul 13 - 04:27 AM

Thanks guys for some fascinating and interesting comments.

As for sealing the soundhole, well, the DeArmond has quite a depth to it - don't forget that, as well as the thickness of the pickup itself, the volume control is a largish wheel. The top of the wheel projects slightly through a slit in the side of the pickup but, like an iceberg, 9/10s or whatever of the wheel lies below - which will have an effect on the available depth. As I recall, Gibson did a "Chet Atkins" electric classical model which had a sealed soundhole - sounded great, but I never cared for the look of it. I'm reasonably careful about where I place myself in relation to amps - playing both electric and electro-acoustic instruments - and I rarely get feedback these days.

The size of the DeArmond will also influence the width of the soundhole, as I removed the springs which held it temporarily in place, and drilled two small holes in each end so it could be bolted into the guitar face. This is how it will be fixed on to the new guitar. I'm treating this primarily as an electric instrument - the DeArmond is a conventional electric pickup with a large and powerful magnet inside it - and it'll be interesting to see what acoustic resonances are created when the guitar is built...

Subject: RE: Building a guitar around a pickup
From: Mooh
Date: 06 Jul 13 - 08:14 AM

I've considered similar things in the past and never acted on them, other than to play a Godin Acousticaster and a variety of my acoustics with a variety of pickups. I would consider a top without a sound hole, and move the hole to the upper side facing you. It reduces feedback, makes the top stiffer with more surface to resonate, but maintains some acoustic quality to the tone, and you can still play it unplugged quietly. You may have to rewire the pickup to accommodate this, or fashion some sort of drop in design.

My good friend and former student Josh House (www.houseguitars.com) built a narrow body acoustic recently as a live performance guitar for a customer, not around the pickup but around other considerations, and it turned out magnificent. I had the opportunity to play it before it was delivered, and it had way more tone than I anticipated.

It's a great idea Will. I hope it works out for you.

Peace, Mooh.

Subject: RE: Building a guitar around a pickup
From: Uncle Phil
Date: 07 Jul 13 - 11:23 AM

I looked at the pictures of the pickup again. I see what you mean about the size of the volume control wheel. Let us know how your guitar turns out. It's an interesting project.
- Phil