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Author Topic: Unique pickup options for 12 fret Larrivees?  (Read 972 times)
sgarnett
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« on: January 29, 2007, 02:59:14 PM »

The Larrivee 12-fret models have a fairly long bridge plate compared to the 14-fret models (and probably even a Martin 12-fret) due to the shifted bridge. The X brace still crosses right behind the soundhole, and the bridge plate still connects two legs of the X. Ergo, the bridge plate has to be longer. I've confirmed this on the Parlor, 00, and OM(forum) bodies, and from the photos I think it applies to the 000-50/60 and SD-50/60 as well.

That means there's a lot more room for attaching pickups. Of course, covering the plate entirely with pickups would add a lot of mass and kill the sound, but there's still a lot of opportunity for alternate placement. For example, there's probably plenty of room for the full size Pure Western on even the Parlor (if the plate is wide enough to clear the string balls). The K&K Macaferri setup might be an interesting choice, or the K&K classic setup might be interesting (perhaps with three heads installed like the PW-mini and the fourth at one end or the other of the plate. Heck, use a stereo plug and combine the Macaferri and PW-mini setups, or just wire them all in parallel.

I suspect that trying to combine an IBeam with the KK sensors in parallel would be a problem due to impedance mismatch, but an IBeam combined with a Macaferri on a stereo plug might be interesting.

Why mess with success? Well, partly because it's there. I did a lot of experimenting with homebrew contact transducers in the past, and moving them around can have surprising (and good) results. Also, "temporary" mounting combined with a few extra heads might yield a little feedbeack resistance (playing with other amplified instruments) and mechanical filtering of the swoosh and fret noise while still providing a strong signal with low(er) output impedance for driving through a long cable. I have several UST pickups, both passive and with internal preamps, but don't really care for them.

Has anyone tried anything along these lines? Does anyone know what the K&K heads weigh (mini or standard)? I know the IBeam is around 8~9 grams.
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sgarnett
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« Reply #1 on: January 29, 2007, 03:29:20 PM »

BTW, as far as I can tell, there are two differences between the Jazz/Archtop setups:

- The Archtop setup has longer cables, which shouldn't be necessary on a 12-fretter except for possibly the SD body.

- The Archtop setup comes with a stereo endpin jack, while the other passive setups don't seem to (not specified). Jacks can be changed ....

The IBeam Active includes a second, passive channel (presumably using a stereo jack), so adding a passive Macaferri setup to it would be easy. However, I've become a fan of keeping the internal wiring passive if possible.

It should be easy enough to model the weight distribution of various schemes with small weights on the top to check for any affect on the acoustic tone.
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sgarnett
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« Reply #2 on: January 30, 2007, 02:35:44 AM »

After some more time trying to interpret reality through a tiny mirror light, I'm not sure the K&K PW mini would fit on the forum guitar. It looks like most of the plate is actually on the opposite side of the pins from the saddle, so that it meets the big lateral brace (the one that is diagonal to the grain on Martins and perpendicular on Larrivees). The K&K jazz setups (a sensor at each end of the bridge plate) might be the only option (other than a UST).

I know several people have installed minis on the Parlor and 00, though even that looks much tighter than the bridgeplate on my 14-fret OM.

OTOH, there's plenty of room for even the large sensors (the "Big Twin Internal") at the ends of the plate on all three sizes.
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maxferry
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« Reply #3 on: February 08, 2007, 04:41:25 AM »

After having installed the K&K PWM in my L03, I can advise that the weight of the tranducers is negligible; I doubt if they even weigh as much as the wire they're attached to.

I think you might have hit on something with the K&K Classic; 12 fret guitars I've played always seemed to me to skew in the direction of a steel string classical type deal, both in tone and playing. I might be inclined to utilize that similarity, come up with a little different take on the steel-string paradigm. It sure would be fun to experiment...maybe 2 transducers under the bridge, one on the neck heel block, another right on the soundboard...or?   
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sgarnett
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« Reply #4 on: February 08, 2007, 01:33:11 PM »

The design of the classical pickup is driven by the unique restrictions imposed by classical fan bracing. There's a brace crossing the bridge plate between the 3rd and 4th strings, so placing a center pickup between those strings (as in the steel string setup) is impossible. Instead, one pickup is placed on each side of the brace, and the outer pair is still placed between 1&2 and 5&6 like the steel setup. Necessity can be the mother of invention, though, and the classical design will provide a lower output impedance. There's no mechanical reason why the classical arrangement wouldn't fit a steel bridge.

Four pickups does allow more options for placement. The trick is going to be avoiding phase cancellation (or choosing the best frequencies to cancel). I suspect that's the reason for placing all three or four directly under the saddle, or at each end of the bridge for the Macaferri: they are unlikely to be consistently out of phase. Some degree of random phase and attack difference does seem to be a good thing, though, given the rich sound that often results from blended, multi-pickup setups (even on a conventional electric).

The neck block is an interesting idea. With my homebrew pickups, I even found fairly good results on the peghead, but it wasn't a practical location for a cable.

The tricky part about experimenting is that temporary installation changes the results. Clearly, I need to buy more guitars so each experiment can be glued in properly 
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sgarnett
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« Reply #5 on: February 08, 2007, 01:39:57 PM »

By the way, "back in the day" I made my contact picups from Radio Shack piezo buzzers. They were available in a variety of sizes with different sensitivy, impedance, and frequency response characteristics. Some even had a small section isolated for a third wire to provide feedback (either positive feedback to simplify a fixed-frequency oscillator circuit, or negative feedback to smooth out the frequency response). The hardest part was getting the glued plastic case open without damaging the piezo element. The buzzers were a sandwich consisting of a thin brass diaphragm acting as the grond, the ceramic piezo layer, and a sputtered or vapor-deposited silver electrode. They could be carefully trimmed to other shapes using a dremel cutoff wheel. As crude as it may have been (and probably heavier than modern options), the results could be surprisingly good.
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sgarnett
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« Reply #6 on: February 16, 2007, 12:26:10 PM »

Here's a very cool picture of the OM-03PA bracing taken by (I assume) Little Brother. It's on his old site, but I haven't found it on his new site. Hopefully the link won't die in the near future. From my dental mirror inspections, I think the Forum guitar bracing is just like this, and the 00 and Parlor are similiar but scaled down a little of course.

Note that the saddle seems to be right over the front edge of the bridge plate. There is another brace parallel to the bridge plate but closer to the soundhole, roughly where the pins would be with a 14 fret model. I thought the bridge plate was butted against the long lateral brace at the bottom, but the picture shows a gap there. I confirmed that the gap does indeed exist on my forum guitar.

http://littlebrother.nlpd.com/Ebay/pete/Larrivee-om03pa-bracing.jpg
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