Next, the ESS AMT-1 diaphragm in a DIY motor:
First, a bit about the motor. I built this (full-dipole) prototype motor to evaluate the ESS as well as AC diaphragms (diaphragm dimensions and materials are somewhat different). The proto motor has only half the neobdymium of the AC motor so sensitivity is about 6db lower…but 92db is still quite useful. With less neo, cost is lower than the AC. Like the AC driver, LF output should increase with a back-cup and horn.
Despite reading past references to poor quality, the ESS diaphragms I tested were very nicely assembled. I had high hopes for the ESS because it is nearly as large as the AC, pleat spacing is nearly perfect, and it costs less. However, as seen in the FR plot, the ESS suffers from resonances at 7k and 11.5k.
Spectral decay is "okay"…except for those pesky resonances.
Non-linear distortion is simply too high. Even more troublesome, is sub-harmonic
output at several frequencies, including clusters of frequencies generated from 1-2k when driven from 2-4k. While visible on the sweep screen, sub-harmonics are not plotted as typical 2nd-5th, but they are clearly audible
when running the HD sweep…they sound far worse than typical HD. Two samples of this diaphragm were tested with substantially similar results.