I recently received the Six Rounds Rockabilly Recoil and Double Barrel pickups for upright bass. At a recent gig, I broke an old Underwood when I fell off my bass unexpectedly (long story; maybe another post). I was looking for an inexpensive pickup to replace it and came across those made by Six Rounds.
The Recoil has one wing pickup and one fingerboard pickup (similar to the K&K rockabilly system) while the Double Barrel has two wing pickups (much link an Underwood). The Recoil also has a separate volume control for the fingerboard pickup which, unlike the K&K, is passive and doesn't require a battery. I use a separate preamp and really liked this feature.
I got the pickups before the first in what was a long series of gigs. I was short on time and didn't have the option of experimenting with the pickups. Installing the pickups was easy, although the fingerboard pickup on the Recoil is much larger than that of the K&K. As a result, I had a harder time finding a large enough flat spot under the fingerboard where I could install it. I ended up putting it at the top of the fingerboard.
I started with the rockabilly recoil pickup on a Czech plywood bass, but also had another underwood hooked up to do a comparison. While I had briefly tested everything at home before the show (albeit at low volumes) that night the recoil did nothing but feedback. I ended up having to roll off all the bass in order to get anything usable. (I should mention that throughout these gigs I was using a Fishman Preamp, an Acoustic Image Focus and a Bag End cabinet.)
The next day, I decided to run a few experiments. I tried a lot of different EQ tricks but then used something harder (a saw reed) in place of the cork spacers that came with the Six Round pickups. This solved the feedback issues immediately. Its as if the cork absorbs too much vibration from the bass and weakens the signal received by the piezo. As a result, what should have a sharp attack gets muted and those low frequencies are left to bounce around the room. The reed (or anything harder) solved this problem. After some more experimenting, I found that a reed on the bottom and a cork spacer on the top gave me the best sound for the wing pickup.
That night I tried the same set up and the Recoil gave me a more natural sound, rivaling the Underwood. When I slapped, the Recoil was an improvement over the Underwood.
On Sunday I had a gig at an art gallery and used the Double Barrel with one reed and one cork spacer in each wing. It sounded great.
Over the next gigs I compared the Double Barrel to the David Gage Realist on a plywood bass and a carved instrument. These were mainly jazz, swing, and folk gigs so I didn't do a lot of slapping. Across all of these gigs, I needed to modify my tone to fit the genre. Again, using a reed in the wing as a spacer, the Double Barrel gave the Realist a run for its money. The only cases where the Realist and the Underwood were noticeably better were when I mounted the pickups on a carved bass (the Realist captured more of the tonal color of that bass than did the Six Rounds) and when I was bowing.
So, after giving the Six Rounds pickups a workout over two weeks of gigs, I'm impressed with them. For the price I don't think they can't be beat. They sound great and are easy to control in terms of their ability to give you the tonal color you want. I think for regular gigs, this is a great option, particularly the Recoil as you have the extra control with the fingerboard pickup.