Double Bass King Moretone Bridge Height Question

[gbaker]

I have acquired a blond '54 King for my next repair project. It will be used for blue grass or such, not bowed.

A major decision is with the neck set. The neck was repaired at least twice and it has been stable for 15+ years according to the two previous owners. It looks like it was first repaired with a wooden dowel through the mid-toe to the block and then again with a screw about in the same place. My metal detector finds metal under a wooden plug. Over stand is about 7/8".

The neck angle is low and as a result the bridge is only 5 3/8". I think it should be 6 to 6 1/4".

My question is will a neck reset to afford a 6" bridge height be worth the effort in terms of acoustical improvement knowing that the repair may have been done with non-hide glue and could be messy? Or does it not matter that much.

BTW, it has rib cracking and ply bubbling and I expect to take the front plate off but I doubt that helps with the neck question.

Pix-

King Moretone pictures by ghbaker - Photobucket


Thanks.

 

[KUNGfuSHERIFF]

My '39 King's bridge is 6 1/4" tall and has 3/4" of overstand. My neck has the same break and three others across the heel held together with a bolt but is behaving so far since i reset it last month. Am I seeing things or is the upper bout on the G side crushed?

 

[gbaker]

My '39 King's bridge is 6 1/4" tall and has 3/4" of overstand. My neck has the same break and three others across the heel held together with a bolt but is behaving so far since i reset it last month. Am I seeing things or is the upper bout on the G side crushed?

Thanks for the info KfS. No big problem with the upper g side but the lower has some strange bubbles in the outer ply.

 

[gbaker]

I will try to answer my own question by building and fitting substitute bridge feet (there are adjusters already) to afford 6.25" bridge and compare the open string response. The A-B test is still subjective without a lab.

 

[juuzek]

I will try to answer my own question by building and fitting substitute bridge feet (there are adjusters already) to afford 6.25" bridge and compare the open string response. The A-B test is still subjective without a lab.

My bridge height was increased to a correct level by gluing blocks to the top of the existing feet [where the adjuster hole is]. This might be a good solution for you, as you wouldn't need to recut/fit the feet to the top. After it was finished, it's lowest adjustment was too high, so my luthier cut down the blocks a bit until it was perfect.

Not the best pic [I was shooting the mic, not the bridge feet] but you can see the lighter wood and the seam of where the new wood is joined to the feet.

 

[gbaker]

I will try to answer my own question by building and fitting substitute bridge feet (there are adjusters already) to afford 6.25" bridge and compare the open string response.

I found an iPhone app that measures sound pressure and has a hold function, which makes it an improvement over my old RS VU meter w/o hold. The iPhone mic reportedly rolls off below 50 hz but will do for a A/B test.

A bridge top (above the adjusters) from the junk box afforded a 6.25" height to compare with the present 5.25" one using the same feet.

I did an A/B test on all open strings at maximum output at 24" distance to the mic. There was measurement overhead available (verified with a closer distance distance not shown below).

I was surprised to only find an improvement with the higher bridge on the G and D.

Since I am not interested in improving output only for the higher strings I decided not to reset the neck.

I tested 3 ply basses just for fun and was surprised how little difference in maximum output there was between them. BTW a 3 dB increase requires twice the acoustic energy.

Data (dB) by string:

- C1 C2 C3 C4 C5
G 86 90 87 87 87
D 87 90 89 87 88
A 86 85 84 88 86
E 85 86 84 86 85

Key to Columns -
C1 - King 5.25"
C2 - King 6.25"
C3 - King 6.25 at 36"
C4 - 1950 Kay
C5 - 1960 German Flat Back
All at 24" plate to mic unless otherwise noted.