Originally Posted by Stereodude
Probably Kyle Richardson @ Acoustic Visions. He and his company vanished years ago, around the time Adire folded I think. I never saw any real discussion of the actual performance of the Tumult drivers, but I wasn't watching the various forums that closely over the years with regard to the Tumult. I do remember a few reviews of subs built around the Tumult not delivering the SPL the models predicted. The one Illka measured
had a pretty serious inductance hump, but not as low as mine. It was just over 40Hz, mine is at 30Hz.
I built what should have been a monster with the Tumult shortly after the pre-orders shipped. 220L box with 4 Adire PR-15s at their limit of ~1500g. I used it for a while but wasn't impressed with the performance but didn't really have any comparison point of reference for monster subs at the time. It sat in storage for about 7 years and I got my hands back on it last Friday and discovered my memory of it being underwhelming was very much correct. I started a thread about it
focusing on how to measure it's response without dragging it out into a field and measuring it ground plane. At this point I guess it's mostly academic since there's nothing I can do about it other than consider it a $384.84 lesson in why you don't pre-order audio related things.
The one Ilkka measured was in a 100L box, yours was in free air.
Inductance, inschmuctance. The Tumult was the best sub driver of its day, hands down, and the MKII was flat to >300 Hz, for the inductance-phobes. With 30+ mm of one-way throw it got the job done as well as or better than any of the 100+ drivers I've used.
It rolled off around -8dB from 50-100 Hz, according to Ilkka's and my own measurements. With an 80 Hz 4th order LPF (the standard HT X-over), this was easily managed to a flat response through the crossover. You just have to know what you're doing.
Naked, smoothed and non-smoothed:
One of 12 curves, with proper signal shaping:
4 of them in 2 dual-opposed enclosures with proper signal shaping, signal chain roll off and required power plant yielded 22 liters of displacement, reference level playback, flat to 3 Hz in-room with no compression, inaudibly low THD (<5%) with any disc in existence for $3,000.
You still can't beat that today unless you get in line to wait for the current 18s and 21s and up the box size, finish costs and price of admission.
I personally wish the Tumult MKII was still available. There's nothing available today that bests it... period.