A very well built 5.25" aluminum cone mid bass from Germany with heavy cast frame, aluminum phase plug, and shielded motor.
RCM Akustik AC 5.25 HE-S
A very well built 5.25" aluminum cone mid bass from Germany with heavy cast
frame, aluminum phase plug, and shielded motor.
Gold plated terminals and thick front flange.
An ingenious and effective box system.
I received two drivers for testing. Both were broken in at high excursion
at 20Hz for 72 hours. Oddly enough this did little to lower the Fs from
when I first pulled them out of the box. It's possible that these units
had already been broken in. With a DCR of 7 Ohms and an
free-air minima of 7.3 Ohms I would conservatively classify this a 9 Ohm
driver. Looks like an ideal candidate for an MTM.
Ignore dB scale. Sensitivity is about 87 dB. My SPL plots perfectly
matched those published by RCM.
Also, the pair I received had identical SPL plots. I should think that one would want to cross this driver a little above 2k.
RCM has published a suggested filter but I have not tried it.
RCM has not published the gap height or Xmax for the 525 HE-S. I assumed
that the HE stood for High Excursion and guessed at 4.5mm. Don't know for sure. My numbers came out somewhat
different than those published by RCM. I got a VAS of 12.7 liters to RCM's
17 liters. I got a Qts of .55 to RCM's .48. Even though this
may seem like a fairly high Q, in my opinion these numbers might work well for a
5.25" mid/bass. These numbers aren't that far off from those of the
Scan Speak 15S-8530K-01 as measured by North
Creek Music. It also looks like this driver might be an good candidate for the North Creek's MAPD
driver loading.
A 35 liter vented box tuned to 40 Hz will
have an F3 of about 35 Hz. (slight ripple at 100 Hz).
RCM suggests a vented box of 22 liters tuned to 38 Hz with a 60mm by 196mm vent.
A 20 liter sealed box with a Q of .707 will have an F3 of 70 Hz; F6 of 53 Hz;
and F10 of 40 Hz.
The RCM Akustik AC 5.25 HE-S can be
purchased in the US from Paul Pickard.
$40 each plus shipping. Supplies are limited.
Send e-mails directly to Paul Pickard: pkpickard@lycos.com