Hi,

I wanted to share with you one of my latest drum projects.

I believe it to be model (130), an early 70s “Krupa Sound King” COB with the “Zoomatic” strainer.

My intention with this project was to improve the clarity of the sound (eliminate overtones and unwanted resonance) by isolating some of the metal parts from one another, by using non-metal spacers and gaskets, making no permanent modifications to the parts.

In addition to correctly dating this drum, I seek your comments about these changes.

Details.

It bears a 5-digit serial#33?57, a scratch makes the third digit unreadable; badge is firm and grommet intact. There is moderate surface pitting, but no flaking.

Unlike the later 80s drums, the tone-control and badge are on the other side of the strainer, away from the player. I believe that the badge and tone-control swapped places in the mid to late 70s.

The snare-bed on this drum is wider and a bit deeper than the later drums, nearly as wide as the distance between the lugs adjacent to the strainer and butt assemblies. I have another COB whose snare bed appears to be only wide enough for a 16-strand wire set, with very little to spare.

In an attempt to eliminate unwanted vibrations and overtones, the following improvements have been made:

1) All lugs have been isolated from the shell using gaskets

2) Strainer and butt assemblies have been isolated from the shell using gaskets cut from clear vinyl

3) Cup washers holding the lugs have rubber inserts

4) The Zoomatic strainer assembly also has additional plastic/rubber gaskets or washers to abate rattling

Additional “upgrades” to this drum include

1) brass shell stiffeners at the strainer and butt ends,

2) upgraded/later tone control and

3) removal of several dents.

Snare Wires.

After installing a set of PSZ-1420s on the other COB drum, and assessing the snare lay on the head, I opted to remove the metal strip at the butt-end, and drill two holes, mounting this side with snare cords.

The strainer-end received the mylar strip treatment.

Getting the snare wires to lay flat under tension, and clear the resonant head when off-tensioned was the problem. Since the butt-side roller is higher than the wire opening (below when looking at it upside-down), the wires had a tendency of rolling up on the end-plates pulling the wires away from the head, I think. The smaller foot-print and more flexible nature of the snare cords, allowed them to take advantage of the snare-beds and lay flatter.

Another option would have been to use a nylon roller on the butt-side, bringing the snare wires more in line with the surface of the head. The original metal strip, or a mylar strip (with appropriate slot cut), would probably been an option at this point.

Sound.

The Evans Genera Drys with minimal tone control, medium tension gave a fat “dry” sound – little to no overtones. Strainer-off gave a clean, crisp sound.

I will revert to a more stock (1-ply) head soon and do another sound test.

Thank you all for viewing and your comments.