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Dead String on Fishman Setup?
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Author:  Bruce Dickey [ Fri Oct 12, 2007 7:34 am ]
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Okay, I have an unresolved issue here on this five string acoustic Bass. Of course you never know how it sounded before but made the assumption that all five strings were equally tempered in the pickup?

Well, four strings have strong sound, but when you get to the tiniest string, the G, it's only half as loud.

The customer wanted the action on this fretless bass lowered, which we did, .020 at the saddle, .040 at the 12th fret. Everything was fine until he got home, the G was half as loud as the others.

So, I get to thinking that it needs the break angle adjusted to increase pressure on the pickup which looks like braided wire. I knew these existed, but this is a first for me. I'm used to seeing ribbon transducers in say a Fishman Natural 1.

It was a bit frayed on the end. I also thought it may have slipped out of the slot slightly, and made extra effort to push the pickup tight into the bridge slot at the G which is on the outside lower edge of the slot.

Well, break angle and pushing the pickup to the very end, made no difference. It may have helped in the very slightest of way, but not much. The G can be heard, but it's half the volume of the rest.

We are wondering if these things go bad. The bass is less than a year old. Thanks for any advise you may offer, Bruce
Author:  David Collins [ Fri Oct 12, 2007 8:08 am ]
Post subject: 
There are of course a number of things that could be going on, but here's
one point to consider. On Coaxial transducers I always drill in to the
treble end of the bottom of the slot at a very shallow angle for about
1/4", to tuck the end of the pickup in to. Baggs recommends this for their
coaxials, and I believe they have some diagrams if you download the
Element or IBeam manuals at their web site. The end of a Coax pickup can
often be mute.

Of course there's how true the bottom of the saddle and the slot are,
tightness, both in width and length, etc. I don't know how long your
saddle is, but it could also be worth making sure the active area of the
pickup element is long enough to cover the span.

Then of course, a big difference in breakover angle can have a big effect,
just as you assumed above, but it sounds like you tried ramping the
string slot behind the saddle a bit more and it didn't help?

I would drill in to the treble of the slot to slide the pickup end in to. And
of course check and recheck the bottom of your saddle. Of course, if this
is a Michael Kelly, there's no guarantee that the bottom of the slot is
level.
Author:  Bruce Dickey [ Fri Oct 12, 2007 8:28 am ]
Post subject: 
Thanks Dave, sounds like something to give a go.

Fishman was responsive to the owner today, stating that is sounded like a mechanical problem.   

That Paints the problem with a big brush.

I'm headed down to try your suggestion. Coaxial, I've heard of them but this is the first one I've seen. I'll report back in a bit.
Author:  Bruce Dickey [ Fri Oct 12, 2007 9:12 am ]
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The bottom of the slot looks fine. I took off 1/8th inch of the shrink wrap and pushed it up more. That gave a bit of length to push into the hole drilled out of the slot horizontally on the treble side.

While there, I ramped the slot a bit more. The coax went into the hole at the treble end just fine. Tuned it up and plugged it in. No better, still dead on the G string of this five string. Punt.

The slot bottom looked flat. Stumped again. I considered drilling a new hole on the treble end vertically and reversing the pickup..... but haven't.
Author:  David Collins [ Fri Oct 12, 2007 11:47 am ]
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Well, the usual check list I go through is such.

Bottom of slot, difficult to check but with a few small straight edges you
can guess pretty well. Sounds like that's been done.

Bottom of saddle, I always always pencil the bottom of any saddle and do
a final check/truing on a surface plate or glass plane that I have
sandpaper mounted to. No saddle bottom is ever really true off a belt
sander.

Then I typically miter or round off the edges of the bottom for most
transducers. A quick file across the bottom corners, taking off .005" or so
on each side can help.

That said, none of these sound too likely in your case because the coaxial
transducers are usually the most forgiving out of all the UST styles of
small inconsistencies in the surfaces.

So there's the fit. If it's tight enough that it has to be pressed in to the
slot with any pressure, that can cause problems. This goes both to saddle
width and length. Again not too likely if you just lowered and existing
saddle. You can even rub some wax on the saddle sides and ends if you
want to rule it out entirely.

I'm not sure how far you ramped the slot where the G leaves the pin hole,
but increasing the break over angle even further by ramping it in a bit
further may help.

Then there's the 1 in 100 I come across that still will not cooperate by any
normal means. Grrrrr. For those you can try the old slotted saddle trick.
Drilling small holes through the saddle, between the strings and right
below the surface of the bridge, then slotting from the bottom to the
hole. This allows the saddle to actually flex a bit between each string and
conform to inconsistent surfaces.

Or just scraping away freehand from the higher response areas on the
bottom of the saddle. Or placing a soft ultra thin shim or two (like card
stock) underneath the transducer toward the very end.

I really hate doing any of those last methods, because I think of them as
a shoddy quick fix to a symptom, without every really diagnosing or
addressing the problem. I will typically reroute the saddle slot before
resorting to those methods. Sometimes however it seems they can't be
avoided, usually on cheap guitars with cheap pickups. Go Figure.

By the way, I don't think Fishman sells any coaxial pickups as a standard
product, but you do find them in cheap guitars as a cheap factory pickup.
I've never liked them, and it wouldn't surprise me if the pickup just has
some dead spots. You could even try rotating the pickup to a different
side up to see if it helps.

Good luck, and I'm glad it's in your shop instead of mine.    
Author:  Brad Way [ Fri Oct 12, 2007 11:58 am ]
Post subject: 
Bruce...I once had a very similar problem on a 6 string, one of the strings was very dead sounding. I recut the slot in the bridge and flattened the bottom of the saddle. It worked great when complete.
Author:  MikeP [ Sat Oct 13, 2007 4:49 am ]
Post subject: 
from my experiences with this type of problem I have to agree with the concept that there is a problem with either the saddle or the slot...I've got a 21 year old Taylor K20-ce that upon its last of 9 trips for warranty work the bridge was replaced (finally) and moved back so that it would play in tune (the neck has been removed repeatedly to compensate for the top bellying up)...I guess the top moves quite a bit when tensioned by the strings, the end result being that the slot gets bent out of shape when the strings are on...I got this baby back the night before a gig and spent about 3 hours carefully reshaping my fossilized bone saddle so that the string response was correct....also with under the saddle pickups there is the issue of how you tighten up the strings and in what order...I've found the best method is to put all strings on at very low tension then start bringing them to pitch working from the outside in..i.e. tighten up the outer strings equally and work your way in to the center slowly until concert pitch is achieved....

of course it is possible the ribbon is wacked, that does happen...but my bet is that the 'solution' is to carefully sand a curve into the bottom of the saddle and carefully bring the strings to pitch using the above method..
Author:  Bruce Dickey [ Wed Oct 17, 2007 2:49 pm ]
Post subject: 
[QUOTE=David Collins] Bottom of saddle, I always always pencil the bottom of any saddle and do
a final check/truing on a surface plate or glass plane that I have sandpaper mounted to. No saddle bottom is ever really true off a belt sander. [/QUOTE]

David, today I had a minute to recheck that bass and you were right. The saddle against a straightedge showed each end with a slight upward curve. I took it and a piece of sandpaper to a window pane, and just a few strokes took care of it. Plugged into the amp and bam, full volume on the itty bitty string of the five string acoustic bass.

But now I notice that the biggest string has a loss of volume, that may just be the fact it's lower and harder to hear? I don't know, but now it's the noticably quiet string. Ahhhhhhhhh!      Owner is coming by tomorrow to try it. Thanks for all the suggestions folks.
Author:  Bruce Dickey [ Thu Oct 18, 2007 1:39 pm ]
Post subject: 
We are trashing the coaxial pickup and going with a K and K. Deiter sez it should work fine with that preamp.

Maybe tomorrow? When that low string traded places with the itty bitty string, that broke the camel's back. Time for a change. Dave, I wish this was in your shop.
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