ESS advertised its speakers as having "sound as clear as light". Even today they are still considered excellent speakers with a wonderful sound. These speakers feature a 12" woofer and 12" passive radiator for the low end, and a Heil Air-motion Transformer for the mid and high end. (That's the weird thing at the top.) I'm using original Monster Cable speaker wire, which probably needs to be replaced due to oxidation.
These speakers retailed for about $1000 a pair in 1979 when I purchased them. Today, the latest version (AMT 1E Series 5 Classic) goes for $4450/pair. ESS Laboratories has relocated to Los Angeles and has a new website where you can order AMT drivers, but not full loudspeakers. You can read listener reviews at AudioReview.com, or check out an international dealer at Audio International. The last dealer has the newest version of this speaker, the amt-1e.