My wonderful Hyperion HPS-938 speakers are almost 12 years old and perhaps would benefit from ferrofluid replacement. It applies to both midrange and the tweeter. Midrange uses ferrofluid for damping and doesn't have spider suspension. It would be easy to remove it from the basket, but tweeter might be a problem. It is inexpensive looking 1" soft dome snapped into short horn. It was likely designed that way to reduce distortions (reduce required power) or to vertically align all speakers.
https://www.canuckaudiomart.com/details/649593097-hyperion-sound-design-hps-938-full-range-speakers-...Membrane edge and wires are under glue and would be hard to remove and re-glue (risk of damage). Xover is potted in the black epoxy, but I can see 2.5 ohm large white square resistor near tweeter wires. That's possibly L-pad attenuator (whole speaker is rated 90dB sensitivity). I've never removed membrane in any speaker, so I can find somebody who does it, or replace whole tweeter. Morel makes short horn CAT 378 that has identical dimensions and great reviews. I can measure voice coil inductance at 1kHz, DC resistance, impedance at 1kHz etc. It is 3-way with 2.2 kHz crossover point - way above CAT 378 resonance (1kHz). I have calibrated microphone to compare output at different frequencies. Morel is 93dB sensitive, but if it is a little bit more I don't mind. The whole point is to make it a little bit more vivid. Speakers were always soft/warm sounding with great integration between tweeter and midrange, but now I would like a little more highs. It might be dry ferrofluid, but it might be my hearing as well. Advantage of CAT 378 is that voice coil is easily removable (3 screws) without even unsoldering and also spare coils are available. Below is picture of Morel tweeter. What do you think?
https://www.morelhifi.com/product/cat-378/(I cannot get any help from Hyperion - they don't exist anymore)
