I just completed a homebrew AS-1 seismometer. All of the mechanical bits, including the spring, were purchased from LOWES. The part number of the spring is "C 311." It needed to be cut to length.
I ordered a coil and magnet from Larry. The amplifier is from the following URL http://users.viawest.net/~aloomis/seismom.htm . A power supply for this amplifier can be found at http://users.viawest.net/~aloomis/seisprea.htm .
I must say that the sensitivity appears to be superb as compared to my Lehman (but it's never been quite right after I rebuilt it.)
If you would like more information please contact me at n0ssy at comcast dot net.
The two enclosuers on the base plate are: the large one by the
magnet covers is the amplifier and the small one
is just a box that holds the connectors that go off to the A/D and DC power supply.
I have a vault in the crawl space of my house. It is a 3'x3'x4" concrete pad that is covered with a cardboard box that has 2" styrofoam hot glued to it. When I get the wiring completed I'll let you know how well it works.