ESS

The success of ESS as a hi-fi speaker manufacturer during the 1980’s and 90’s was due to one overwhelming factor - the Heil air-motion transformer (AMT) tweeter that ESS licensed from inventor Oskar Heil. Sadly, the other components that went into ESS systems were not nearly as special as the lovely AMT. The most obvious flaw was their absolutely dreadful crossover networks, which were not only primitive in design, but also built with miserable grade components. Upgrading the crossovers involves more than the typical replacing of capacitors and inductors, because the fundamental design of the networks was rubbish.

One equipped with proper crossovers, the AMT is less stressed, and the woofer sounds appreciably cleaner. Most of the ESS hi-fi enclosures are reasonably well made, and while it is possible to add bracing, the improvement is quite subtle. So, while the original woofers and passive radiators may need new foam edges, the cost is quite reasonable, and the results most satisfying.