Question for you acoustic engineer types

[Uke]

Ran across an idea for archtop guitars with pickups mounted directly onto the top. The suggestion is to raise the pickup rings up off the top by using small washers under the ring where the screws go through too the top -- the idea being to have less of the ring in contact with the top (sort of a semi-floating pickup). Would this make any perceptible (and positive) difference in the tone of the guitar?

 

[Rocky]

Not an engineer, but It would reduce the contact, but it wouldn't reduce the additional mass of the pickups, which I believe is the primary goal of a floating pickup, with the big holes added to the top being a secondary concern. It might make some difference, but probably not as much as you would hope.

 

[Uke]

Not an engineer, but It would reduce the contact, but it wouldn't reduce the additional mass of the pickups, which I believe is the primary goal of a floating pickup, with the big holes added to the top being a secondary concern. It might make some difference, but probably not as much as you would hope.

Yeah, I would predict my ear wouldn't be able to tell the difference. I have a relatively inexpensive Korean Epi Broadway that I was thinking about experimenting with. Thanks Rocky.

 

[Rocky]

Yeah, I would predict my ear wouldn't be able to tell the difference. I have a relatively inexpensive Korean Epi Broadway that I was thinking about experimenting with. Thanks Rocky.

No problem. I suspect it would make a bigger difference with a solid/carved spruce top than with a more rigid laminate.

 

[Uke]

a bigger difference with a solid/carved spruce top than with a more rigid laminate.

 

[matsickma]

There is a special series of Guild guitars designed and built that way. A famous Jazz player had the pickup floating free of the upper body. Don't recall his name at the moment. I beleive his intent was to isolate tbe pickup from the sound board to reduce feedback. Didn't really accomplish what he hoped for. Feedback is the result of a number of factors and the classic low frequency howl still occurred at high volume.

For someone who wants to retain much of the acoustic tone of the sound board floating the pickup on a carved archtop guitar had merit but that would mostly apply when the guitar is played acoustically. The best approach to get the acoustic tone sound amplified would be a combination of a microphone inside the body and a contact pickup under the bridge saddle. A classic magnet and coil electric guitar pickup has its own unique sound characteristics.

Additionally, the overall tone of a guitar, when played electrically, is a complicated combination of acoustics, body vibrations, electromagnetic affects all combined together. Floating a pickup might actually cause the amplified tone of the guitar to not sound as good because that pickup picks up more than just the strings. It will pickup other vibrations on the body.
So what may assume to make something better may have the opposite effect.

My background is an EE with four graduate courses in acoustics. None of that academic "schooling" was any help in making guitars sound better or improving my playing skills. It only allowed me to look at the complexity of the problem in a different light. However it did provide me the physics to avoid screwing up the performance of a sound system in my younger days!
M

 

[Rocky]

There is a special series of Guild guitars designed and built that way. A famous Jazz player had the pickup floating free of the upper body. Don't recall his name at the moment. I beleive his intent was to isolate tbe pickup from the sound board to reduce feedback. Didn't really accomplish what he hoped for. Feedback is the result of a number of factors and the classic low frequency howl still occurred at high volume.

I think that's the George Barnes Acousto-Lectric [sic] and Guitar in F. Pickups were mounted on a bar that ran from neck to endblock, and protruded through holes in the top.

The Barnes design would likely reduce 'microphonic feedback' of internal vibrating parts inside the pickup, which is annoying and high pitched, but rarely an issue except in high gain circumstances. The major source of feedback of electric instruments is the strings becoming excited by sound waves. Hollow/acoustic instruments are particularly susceptible because they're actually designed to have coupling between the soundboard and strings, and anything you do to reduce that (laminate top, soundposts, trestle bracing, semi-hollowbody construction, sealing of acoustic chamber) reduces it's acoustic properties, but can enhance other properties.

 

[Uke]

Currently Guild offers the A-150 with a floating pickup, but given that it appears to be a laminate top probably indicates it doesn't make much positive difference in tone.

 

[Rocky]

Currently Guild offers the A-150 with a floating pickup, but given that it appears to be a laminate top probably indicates it doesn't make much positive difference in tone.

You might be surprised. It won't sound exactly like a carved top, but it won't have the mass of the pickups inhibiting vibration either. Still quite prone to feedback, though.

 

[Nuuska]

My oh my . . .

If there is a rabbit hole somewhere - this might be it
I have not the slightest mathematical skills to dive deeper in any of my plentifull imaginary variations of the situation.

The guitar w.o. pup vs w pup !
If w pup - where is it located ? - What is the mass of it ? Is it supended or hard mounted ?
As of just washers - methinks instead of metal - rubber washers between top and pup-ring plus on top of pup-ring. A poor-man's floating suspension.

Fast forward from that swamp ( bigger than FL ) - what kind is the pick-up ?
Is the pup shallow enough so no hole routing needed vs a hole in the top ?

And probably much more . . .

 

[bobouz]

Currently Guild offers the A-150 with a floating pickup, but given that it appears to be a laminate top probably indicates it doesn't make much positive difference in tone.

Actually, the NS A-150 Savoy has a pressed solid spruce top, which is X-braced & totally free to operate as an acoustic (with the addition of the floating pickup). Because this combo is similar to a ‘30s Gibson-made Wards guitar I used to own (with a carved solid spruce & X-braced top), I purchased a A-150b early out of the gate, just before Fender sold to Córdoba in 2014. Running D’Addaario PB extra-lights, the acoustic tone is quite reminiscent of that old Wards, which I greatly enjoy. Plugged in, the single-coil D’Armond is clear & clean for fingerpicking. The guitar is truly a two-trick pony, both of which work satisfyingly well with my playing style. Of course ymmv, but it’s a rather unique & fun piece, imho. Here’s a photo - only the TRC has been changed:

 

[Uke]

Bobouz, thanks for the clarification on the top.

 

[Uke]

If there is a rabbit hole somewhere - this might be it

Whatever it takes to keep us LTGers from actually playing the guitar!

 

[matsickma]

I was going to say, but bobouz beat me to it with better words..., the NS A150 is a very lively sounding guitar. I had also assumed it was a laminate top but based on the sound and weight I had assumed it was a very thin laminate. Now I know it is a pressed solid spruce top. Mine is similar to the picture and when purchased it was one of the best values around for such a guitar. Now that I know it has a solid spruce top it is an even better deal!

I still have the stock flatwounds on the guitar but am tempted to add round wound to hear the true tone. However I continue to resist such urges!
M

 

[Guildedagain]

If it hasn't been mentioned yet, the floating pickup was widely attributed to Johnny Smith. The idea is to get the pickup off the top so it's not hindering vibration, completely floating, no contact with the usually carved Spruce top on higher end models. The vintage DeArmonds are going for a fortune now, because they sound good and it still a great way to amplify an archtop.