Has spring reverb sprung back into favor?
Achieving natural-sounding artificial reverberation has always been difficult. In fact, even with the latest digital technology it is, and never will be, possible to emulate a real acoustic environment 100% accurately. (I guess you want to know why, but that will have to wait until another opportunity).
The earliest method of generating reverb artificially was to use a 'natural echo chamber', which is basically a real room with speaker and microphones. Unless your natural echo chamber has extraordinarily good acoustics, this doesn't produce anything like a natural reverb sound, although it can be very useful even today.
Next up in the timeline of reverb technology is the spring reverb. When these were first current, no-one really liked them. They had a harsh, metallic sound, and you really could hear the 'twang'.
Spring reverb units did advance and later models were quite good for some sound sources. The 'Great British Spring', although constructed from a real drainpipe, was excellent for strings with a very complex wash of reflections.
However, when digital reverb units first started to emerge, it was plain that the days of the spring were numbered. But human nature being what it is, now that we can have really good digital reverb whenever we want it, somehow we yearn for the quirky sounds of the past.
And there is no better example than the Vermona Retroverb, newly re-reincarnated as the ReTubeVerb, which combines a spring reverb with tube amplification and control stages. Both use the classic Accutronics spring system and add EQ and even an envelope generator.
One trick popular in the 60s and 70s with guitarists with reverb-equipped amplifiers was to kick the amp! This caused the springs to crash together making a sound not unlike thunder.
With a Vermona spring reverb, you don't have to kick it, just press the 'crash' button!