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All systems go !
DRIVE UNITS BY MANUFACTURER:
Morel CAT 378 Tweeter
Categories: 0.75 - 2" (19-50mm) Dome Tweeters Morel Tweeters

The Morel CAT 378 is the modern updated replacement for the legendary MDT-37. This high efficiency horn loaded tweeter features a field replaceable hand coated 28mm Acuflex textile dome, a large ferrofluid cooled Hexatech aluminium voice coil, a vented ferrite magnet system and a tuned / damped rear chamber. This tweeter is ideal for low powered valve amps and has a detailed, unfatiguing sound with a gently downward sloping response - excellent for taming 'live' rooms with hard surfaces. Recommended frequency use: 2000-20,000 Hz. High power rating of 200w nominal, 1000w peak.
A full datasheet can be downloaded from the bottom of this page.
| Resonant frequency (fs) | 700 Hz | Nominal impedance (Zn) | 8 Ω |
| Effective diaphragm diameter | 28mm | DC resistance (Re) | 5.2 Ω |
| Ferrofluid ? Y/N | Yes | RMS power handling | 200W |
| Recommended crossover | 2khz | Faceplate diameter | 94mm |
| Sensitivity (2.83V/1m) | 93 dB | Cutout hole diameter | 72 mm |
CAT378
Not a review of the drive units received as such, because the project is still awaiting other parts from elsewhere, but the tweeters arrived rapidly and in good condition, as usual from Willys.
However, FWIW, based on previous experience with Morel tweeters, and having heard the design I'll be including these in, I would also recommend Morel tweeters. Not necessarily the very highest resolution, but still good clarity, and very easy on the ears. Good power handling too, and easy to replace the diaphrams if the worst happens.
Thanks for the review John !
Will & Caroline
Excellent customer service and good prices.
Thanks for the review Simon !
Will & Caroline
Friendly technical support
40+ years in the trade
UK family run business
Excellent customer service
Quick dispatch
I tried this uprated capacitor through sheer curiosity and am pleasantly surprised with the results. So far, and not too many hours in, it’s giving a slightly smoother edge to the top end and has solved an issue I had regarding some hardness to the sound. I’m impressed enough that I’ll look to replace the mid range caps in the future.
New Foam covers supplies by WHF have completely changed the appearance- they look brand new! Great quality foam, very reasonably priced and quick delivery. Delighted with they now look and sound - will hang on to them forever now.
Excellent upgrade, works perfectly with the speakers it's just soldier and play, they takeaway the over intensity of the original tweeters.
I've had my Mission 734s for about 30 years and for the last five or so the bass units have been falling to pieces. I was about to take the speakers to the tip, but didn't have the heart knowing how capable these used to be. I did a little internet research and these Monacor replacements appeared to do the job. Next day delivery from Willys was impressive, as was the killer sound once the replacements were fitted (which was a simple job). I'd forgotten how these speakers make the windows rattle. Very happy customer!
Excellent service from Willys-Hifi. Caroline was very helpful and patient when answering my queries. Please be aware that some soldering is required when connecting the tweeters. Something I haven't done since I was at school over 40 years ago! They do sound good though, listening to Smoke on the Water as I write , wow 😆
