Bridge knocked out of whack

**Chris Fitzgerald** · #1 03-12-2011, 07:37 AM

Not sure how it happened, but I noticed it more by the amplified sound than anything. The feet were clearly too far neckward when I checked, so I tapped them back down to be roughly more or less centered on the interior f-hole notches. The amplified honks from the Full Circle improved or went away, but it's still clearly not where it was.

Before, I often kept the FC set with the wire on the corner of the bridge leg, as setting it in the middle of the leg gave too dark/undefined of a sound. Now, setting it on the corner sounds completely weak and thin and setting it in the middle makes it about twice as loud. Looking at the bridge adjusters (threads are down on mine), it looks like the bottom of the adjuster wheels and the top of the foot beneath are not parallel, and I'm assuming that they should be. I'm assuming that if this is true, I need to knock back the bridge top until they look parallel, or at least moreso. Lluthier types - is this a reasonable assessment of how to proceed? I can never tell if a bridge is straight by eyeballing it. I'll have some time to mess with the bass later before the gig, and I hope to make some progress then. Any tips appreciated.

PaulCannon · #2 03-12-2011, 07:49 AM

Quote:

Originally Posted by Chris Fitzgerald

Looking at the bridge adjusters (threads are down on mine), it looks like the bottom of the adjuster wheels and the top of the foot beneath are not parallel, and I'm assuming that they should be. I'm assuming that if this is true, I need to knock back the bridge top until they look parallel, or at least moreso.

I'll let a professional handle your question, but I will point out that one can't assume the adjuster's wheels were ever parallel to the top of the bridge foot unless you observed that immediately after the wheels were installed.

Having installed adjusters in about 40 bridges, I know the point of contact will only be flush and/or parallel if the luthier takes the time to make it so. Depending on their method of installation and attention to detail, it's possible the adjusters were never perfect.

Uncletoad · #3 03-12-2011, 08:05 AM

I'm sure the adjusters were dead on when they were done. That's not a detail our boy misses.

The bridge should have a line of tension straight from the bridge top string break point through the adjuster wheels to the feet. That line should bisect the notches on your bass. Do that and the pickup should sound pretty normal.

If it's off you have to straighten the top up till everything lines up. Whack it, tap it, whatever you have to do to line everything up. They tend to fall away one way or another over time with banging into stuff and humidity changes.

Stuff will never stay put either, it's always in some level of flux through the above changes. Just have to eyeball it from time to time to get things to sound and look right. Sometimes what used to work doesn't anymore. Wood moves and changes, never stays constant. Gotta roll with the changes.

Jake deVilliers · #4 03-12-2011, 09:17 AM

Quote:

Originally Posted by Chris Fitzgerald

Not sure how it happened, but I noticed it more by the amplified sound than anything. The feet were clearly too far neckward when I checked, so I tapped them back down to be roughly more or less centered on the interior f-hole notches. The amplified honks from the Full Circle improved or went away, but it's still clearly not where it was.

Before, I often kept the FC set with the wire on the corner of the bridge leg, as setting it in the middle of the leg gave too dark/undefined of a sound. Now, setting it on the corner sounds completely weak and thin and setting it in the middle makes it about twice as loud. Looking at the bridge adjusters (threads are down on mine), it looks like the bottom of the adjuster wheels and the top of the foot beneath are not parallel, and I'm assuming that they should be. I'm assuming that if this is true, I need to knock back the bridge top until they look parallel, or at least moreso. Lluthier types - is this a reasonable assessment of how to proceed? I can never tell if a bridge is straight by eyeballing it. I'll have some time to mess with the bass later before the gig, and I hope to make some progress then. Any tips appreciated.

Just go ahead and pull the bridge top back until the Llines of the Llegs and Ffeet are paraLlel. I'm sure Nnick did his usual exceLlent work on your bridge.

I always include the exact string length on the invoice of DBs I've worked on so as to be useful in this sort of scenario. I like Upton's idea of a bridge-top to fingerboard gauge stick too.

**Chris Fitzgerald** · #5 03-12-2011, 10:43 AM

Thanks guys. I'm going to tune it down a bit, Llay it on the bed, and try to get the bridge straight. Nnick always suggests using a ruler to check the angle of the top of the bridge to the surface of the top. I know what to do to set the bridge straight, but have Nnever experienced the weird pickup response before or the asymmetrical appearance of the adjuster tilt before. Hopefully everything will work out just fine. I know I'm fussy when my sound/response isn't where it should be!

Don Higdon · #6 03-12-2011, 07:24 PM

The time to do this is immediately after setup:
With soft lead pencil and a straight edge, mark the top to show the positon of all four corners of each bridge foot.
Then, measure the string length and write it down. Then, you'll always be able to restore the bridge to its proper position.

**Chris Fitzgerald** · #7 03-12-2011, 11:18 PM

That's a good idea. The club was kind of noisy tonight (as usual), but with the bridge back in place and the string height moved back up to 6-9mm, it felt/sounded really good. The amplified sound was good, but maybe a little thick for my taste. What with the ambient noise, I didn't really worry about it too much. It seems that the Full Circle now has two basic sounds that are distinct:

- Thick and loud, with a lot of response on the G sting. This is the sound with the wire in the middle of the foot, and it requires some judicious high pass filtering to whittle it down. Once that's dialed in, it's a really strong sound.

- thinner and quieter, but more focused. With the HP filter turned down or off, it's also very usable, and the extra gain can be dialed back in at the pre gain level. I'm not sure which I prefer yet, but I was happy enough with either tonight.

Tomorrow I'll check the acoustic sound more thoroughly and see if today's impressions hold. if so, then maybe I can mark and measure as suggested above.

William Hoffman · #8 03-13-2011, 09:54 AM

Quote:

Originally Posted by Chris Fitzgerald

Not sure how it happened, but I noticed it more by the amplified sound than anything. The feet were clearly too far neckward when I checked, so I tapped them back down to be roughly more or less centered on the interior f-hole notches. The amplified honks from the Full Circle improved or went away, but it's still clearly not where it was.

Before, I often kept the FC set with the wire on the corner of the bridge leg, as setting it in the middle of the leg gave too dark/undefined of a sound. Now, setting it on the corner sounds completely weak and thin and setting it in the middle makes it about twice as loud. Looking at the bridge adjusters (threads are down on mine), it looks like the bottom of the adjuster wheels and the top of the foot beneath are not parallel, and I'm assuming that they should be. I'm assuming that if this is true, I need to knock back the bridge top until they look parallel, or at least moreso. Lluthier types - is this a reasonable assessment of how to proceed? I can never tell if a bridge is straight by eyeballing it. I'll have some time to mess with the bass later before the gig, and I hope to make some progress then. Any tips appreciated.

Chris, I had the same issue with my new La Scala (not due to Arnold's or Wil's set up). After changing strings, the bass when played gave a rattling sound which I finally localized in exactly what you describe: the flat top edge of the adjuster wheel wasn't exactly parallel with the bottom of the bridge leg.

If you place a bright light on the other side of the bass and angle the bass such that you can peek through that crack, you can see which way the bridge needs to be knocked. This seems to be an issue with the FC but there isn't much info on it.

**Chris Fitzgerald** · #9 03-13-2011, 10:57 PM

William - I'm not sure that was the issue with mine. What I was trying to describe was the whole adjuster (screws and all) being at a tilt while going into the lower bridge foot. I tilted it back, and the sound changed drastically. I didn't notice any gap between the pickup and the flat part of the bridge above it, although there may have been one.

Acoustically, the bass sounds powerful and rich now that the bridge is back in place. It's happened before, but i can't help but think that having the bridge moving around gives me a better sense for what moving the sound post does, since when the bridge moves and the post does not the effect of the two relative to each other is similar. When the bridge moved forward, the feet were farther from the post, the string height dropped a bit, and the tension was lower. While it made the bass feel "looser", it also diluted the sound and produced some strange wolf tones, especially on the open G and the first minor 3rd above it; the note was there, but it had a strange hollow sound to it compared to the rest of the bass, as if the center of the tone had been sucked out like marrow from a bone. I've heard this same effect before during post adjustment experiments where the post was moved back away from the bridge foot.

Apparently, I like a very tight sound and a tight/fast feeling of the strings that is produced by the bridge foot and post being close to each other. With the setup like this, at this height and with these strings, the sound is gorgeous, articulate and strong, but the tension takes a toll on the hands. Time will tell about that. For now, the tone is worth it. It's like the physical version of what was going on with the HP filter I described above - the strong, direct sound is a great color to have in the palette, but when it's there the softer more ambient tone has to come from the hands by backing off and using more RH finesse. I like this paradigm, but I'll need to give it a few weeks/months to see whether my hands agree. If they do, I'll be a very happy guy.

William Hoffman · #10 03-14-2011, 02:55 AM

Quote:

Originally Posted by Chris Fitzgerald

...What I was trying to describe was the whole adjuster (screws and all) being at a tilt while going into the lower bridge foot. I tilted it back, and the sound changed drastically...

Acoustically, the bass sounds powerful and rich now that the bridge is back in place.

Chris, sounds complicated, but I guess you fixed whatever it was. Maybe you even improved the sound?

Just a thought, but given that the FC adjuster threads are cut into the bridge wood itself, a tilted adjuster like you describe could damage the threads if left too long and under full tension.