Size of Midrange Drivers

Lewinskih01, I have no idea. Hyperion went bankrupt (poor marketing,
poor dealer base) without any parts sale. I'm not sure why they decided
upon such large midrange driver but I suspect they wanted to reduce
membrane excursion making it more linear. 3kHz xover was probably
selected to stay away from the tweeter's resonance that is around 1.5kHz.
If this xover is single pole 6dB per octave then tweeter helps keeping
dispersion around 2.5-3kHz, as Johnyb53 stated. It is possible to
improve linearity at large excursions by using underhung, instead of
common overhang motor. It is rare, likely because of the increased cost
(large magnet). I've seen this only in Acoustic Zen woofers or Morel
Supreme tweeters. In underhung motor coil is very narrow while
magnetic gap is very wide. Coil is all the time inside opposite to
overhang design where coil is long being mostly outside of very narrow
magnetic gap.

Kijanki, yes larger diameter voice coils are definitely desirable from a thermal standpoint, all else being equal. Ferrofluid helps as well, assuming it's a good heat conductor, which it probably is. On the other hand I don't recall seeing any prosound company using ferrofluid, so it may have downsides when subjected to high temperatures over time.

I can't comment on the unorthodox suspension system of the cone drivers in the Hyperion; I don't know enough about suspension systems.

Duke

Kijanki: I just checked out the 6Moons in-depth review (from 10 yrs ago) of the Hyperion hps-938. The midrange unit addresses this dispersion challenge in its design. Notice that the Hyperion midrange has a large, flat dustcap. It's not a typical dustcap, however. Hyperion called this the SVF--Synchro Vibrate Flattop. This dustcap floats independent of the main diaphragm and is connected directly to the voice coil. What this does is provide a midrange-within-a-midrange of smaller diameter to ensure wider dispersion of high frequencies that would beam at 6-1/2" but not at 3" (or whatever diameter this floating dustcap is). That's a pretty ingenious solution to have it both ways--larger diameter for more radiating surface and deeper reach while keeping dispersion consistent as frequencies rise toward that rather high 3K crossover point.

That's what whizzer cones and phase plugs are used for in many fullrange drivers (e.g. Fostex and Audio Nirvana). But Hyperion's flattop dust cap strikes me as a more ingenious and precise way to achieve that.

Johnyb53, unfortunately Hyperion went bankrupt since design is only small part of success. Now, I feel uneasy about spare parts or service.

Hey! Tannoy! You've only been making speakers since 1926 so take some more lessons because somebody on this web-site thinks you and I are "confused".

Stop making your $55,000 Kingdom Royal until you get straightened out and start using 5" midrange drivers!

(dang this is fun!)...