There is a web site with the whole set of ESS Heil speakers from this company at http://www.eliteavdist.com and a review at http://www.positive-feedback.com/Issue20/ess450.htm. According to the review they are very nice but quite expensive.

I have had a pair of AMT-1Bs for a long, long time. I bought new 12" woofers (polypropylene like the newer 1D model, which I think sound better than the original ones) and passive radiators directly from the original ESS in Sacramento within the last few years. MeanGene, do you know anything about the relationship between the original ESS and this company? The original ESS in Sacramento was still selling AMT-1D's and AMT-Monitors as well as replacement parts by direct mail order for pretty reasonable prices, at least up until a year or two ago. They were even selling off some inventory of the large Heil tweeters quite recently on ebay.