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The Alcone line of aluminum-coned woofers and mid/bass drivers and ceramic
composite dome tweeters is produced by RCM Akustik (hereinafter, simply "RCM"), a
German manufacturer. Used in a number of OEM systems, Available data suggests that
the metal cone drivers are better controlled than Seas', yet not quite as well
controlled as Jordan's. Each of the metal cone drivers have one or two strong
resonance points, usually well above the passband. Alcone's data sheets each have
suggested crossover designs to tame these problems. To date, I've received
recommendations for the following drivers:
- The AC1HAT Mk2 is a 1"
shielded dome tweeter featuring a ceramic composite diaphragm. One respondent
described the Mk1 version as, "…very refined - the extension of the best
metal domes with the smoothness of silk…". At that time, the published
FR and waterfall data show some uncontrolled resonance and breakup right at 20
kHz, which the same respondent's measurements did not confirm. Interestingly,
the Mk2 version's curves show better control of the out-of-band resonance.
front view
side view
view
response
waterfall
crossover
- The AC525HE is 5.25" shielded
mid/bass unit featuring a rubber surround, die-cast frame, and central phase
plug. The cone resonance falls around 6 kHz. RCM publishes a recommended notch
filter which should be used with driver. Using the notch filter and a simple
first-order crossover, this drivers exhibits flat response out to 2 kHz, and
can reach as low as 34 Hz in a vented box.
front view
side view
response
waterfall
crossover
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