Chapter 1: Introduction 3
About the Speakers
The Digidesign RM1 and RM2 are both two-way
(bi-amped) active reference monitors with inno-
vations in amplifier and crossover design and
include PMC’s ATL™ (Advanced Transmission
Line) technology.
ATL Technology by PMC
PMC has taken loudspeaker design to the high-
est level with the use of ATL (Advanced Trans-
mission Line). These designs utilize sophisti-
cated cabinets, proprietary drive units and
special absorption materials.
How ATL Works
The main driver is placed at one end of a long
tunnel (the transmission line), which is com-
prised of a series of internal baffles within the
cabinet. The transmission line is lined with
acoustic material that is designed to absorb the
upper bass range that radiates from the rear of
the main driver.
The lowest frequencies emerge from the large
vent at the end of the tunnel, in phase with the
main driver, extending its LF output. The pres-
sure created within the line controls the main
driver over a wide frequency range, dramatically
reducing unnecessary excursions and the result-
ing distortion.
The mid range in turn appears cleaner and
clearer as it is not masked by harmonic distor-
tion residing in the very low frequencies. This
technology produces a higher SPL and lower
bass extension than a ported or sealed cabinet of
a similar size using identical drivers.
Drivers
The RM1 features a 5 and 1/2-inch LF driver,
while the RM2 provides a 6.7-inch LF driver.
These LF drive units are optimized for an ATL
design.
Both the RM1 and RM2 monitors use an identi-
cal 1-inch, soft dome, ferro-fluid cooled HF
driver.
Amplifier
In the RM series both HF and LF drive units are
independently driven by separate low-distor-
tion, analog-controlled “Class D” power ampli-
fiers. This type of amplifier combines the effi-
ciency and size advantages of a digital amplifier
with the precision, control and sound quality of
linear amplification.
DSP and Crossover
Within the RM series, the crossover function is
handled by a digital 48-bit fixed-point proces-
sor. The powerful DSP processing engine han-
dles the audio signal in the digital domain for
precise control and integration of the drive
units along with the EQ parameters, Bass Port
emulation and Left/Right channel selection.
Clock
The analog input ADC (Analog-to-Digital Con-
verter) is sampled at 96 kHz, 24 bits and is
locked with a discrete low-noise clock oscillator.
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