Tip #28 (July 2001): An Update:
Hammer Dynamics has recently updated the S-12 loudspeaker kit (see Tip #18) by replacing the old titanium dome tweeter with a new fabric dome (Audax model TM025F15). Since Audax had discontinued the titanium dome, it became necessary to find a suitable replacement. I was asked by Hammer Dynamics to evaluate the new tweeter selection and determine what if any changes might be necessary to the electrical crossover network. This consulting was performed at no cost, in memory of John Wyckoff.
I'm happy to report that the new tweeter integrates seamlessly with the woofer using the current crossover network. See the frequency response of the S-12 (above) with the new tweeter in place. The resultant tonal balance is a bit more vivid and smoother through the upper octaves. However, there is a slight loss of treble resolution. I don't think that the fabric dome is as quick or detailed as the old metal dome, but it's VERY natural sounding. Overall, considering the various tradeoffs involved, I think that the fabric dome tweeter is the better choice. I continue to recommend the S-12 kit as a tremendous sonic bargain. Please contact Hammer Dynamics (firstname.lastname@example.org) for more information.
There have been some questions about the crossover schematic as published in my original article and the one provided as part of the kit manual. The difference has to do with the position of the trap circuit and the resistor value in the network. I recommend that the network be assembled as shown above with a 8.4 ohm resistor value, which by the way, is exactly how John Wyckoff wired my pair of S-12.