Heres some info from Drummerwold:

"The Resonator Series was introduced by Premier in 1972 and was originally called the 'Kenny Clare' series.

The Resonator concept was invented by Alan Gilbey, a UK custom drum builder who still makes drums today. He came up with the idea of adding an inner shell to the 50's WFL snare of his friend Kenny Clare, Kenny tried out the snare and eventually an entire kit was fitted with the inner liners.

Unlike many modern drums, nearly all drums 30+ years ago were thin shelled with support rings, the inner shell was cut to size and 'sprung' into place on the support rings creating a cavity between the main shell and the inner shell. Kenny toured with the USA with his Resonator WFL kit and they presented the idea to Premier drums. The Kenny Clare kit appeared in the 1972/3 brochure but by 1975, the kit was renamed 'Resonator' and was the first range of drums from Premier with a 'secondary' brand name.

Visually, the Resonator range looked identical to the regular Premier drums, apart from the 'R' logo that appeared in the bottom right quarter of the bass drum reso head. By 1978, Resonator had it's own wrap configuration which sported a black hoop inlaid into the main wrap of each drum approximately a third from each drum's resonant head. In the late 70's, the range gained a small badge under the main Premier 'P' badge identifying the drums as Resonators, Premier by this time had a number of 'brands' under the main banner; 'Club' (formerly 'Olympic'), Soundwave (followed on from the short lived mid-range 'Super-Olympic'), Elite (brand for the regular Premier range) and Resonator, all had their own badges under the main Premier badge.

In 1983, Premier launched the 'Black Shadow' range which was essentially a Resonator range but with single tension lugs, deep shells and a purple/black lacquer. This range ran alongside the Resonator range for a few years until the 'Black Shadow' was absorbed into the Resonator line and was fitted, by then with hi-tension lugs, as were all the late 80's and early 90's ranges.

Resonator disappeared around 1992 and are now considered quite collectible, especially earlier, 70's examples.

From a premier ad:

"Premier Resonator

Not just a new outfit, but a new kind of outfit

Few drummers in the world do as many gigs as Kenny Clare, and not many of those do as many different kinds of gigs. So when he teamed up with Premier to create this new professional outfit, the result literally had to be able to do it all and do it all better.

The Premier Resonator does it better by doing it differently. Resonator drums have double shells — a conventional outer shell, plus a thin inner shell separated from it by a pocket of air. We call it Resonator because that's exactly what it is — a sound box inside the drum that produces 18% greater volume. We know because we've tested it electronically. You'll know the minute you try this remarkable new set. The Resonator outfit includes all of the most desirable Premier features, and will give you the ultimate in sound, power, and performance."

I have never played a Resonator kit, but am a big Premier fan and I'm sure the concept is sound. It gives me GAS just thinkin' about it!