Meyer Sound Self-Powered Studio Monitor HM-1S - Manual (Page 3)

3
Introduction
The Meyer HM-1S Studio Monitor is a compact, full-
range, self-powered reference monitor that employs a
concentric tweeter mounting structure to achieve true
point-source performance. Sophisticated phase-correc-
tion circuitry provides superb imaging without the off-axis
cancellation effects, back-wave interference, and IM dis-
tortion commonly exhibited by dual-concentric speakers.
The HM-1S Studio Monitor is a two-way system comprising a
7-inch graphite cone low-frequency driver, and a concen-
trically-mounted, 1-inch soft-dome high-frequency driver.
A constant-directivity, high-frequency horn affords a sym-
metric 100° beam width. The HM-1S employs optimized
electronics, drivers, and cabinet venting (tuned to 40 Hz)
to achieve low frequency response far exceeding that of
most small speakers. The drivers are magnetically shielded
and the magnets employ field-cancelling techniques
to minimize magnetic leakage, allowing speaker place-
ment within one foot of color video monitors.
The HM-1S can be used with the Meyer HM-1S Studio
Subwoofer, extending the free-field LF (low frequency)
response down to 42 Hz. The passive subwoofer is
powered from the Sub output on the rear panel of the HM-
1S. Although each HM-1S Studio Monitor can power a
subwoofer, ample LF energy may be obtained by driving
one subwoofer from two HM-1S Studio Monitors, result-
ing in a correctly-summed mono signal. Subwoofer usage
depends on the loading conditions, the LF gain desired,
and whether a stereo LF signal is required. Placing the
HM-1S next to a wall or ceiling (half-space loading) also
extends the LF response down to 42 Hz.
The HM-1S Studio Monitor and Subwoofer cabinets are
constructed from medium density fiberboard and fin-
ished with an attractive, durable oak veneer (natural
wood or black). Although external heatsinks on the rear
of the cabinet provide adequate convection cooling, a
variable-speed cooling fan assembly (part# 40.039.016.01,
driven from a rear-panel output and mounted on the rear
of the speaker) is available if the HM-1S will be operated
in hot temperatures or in an unventilated, enclosed area.
The enclosure contains a 400 W stereo amplifier, an active
crossover, frequency and phase alignment circuitry, and
driver protection voltage limiters. Front-panel LEDs indicate
power, signal limit, and thermal overload, and a rear-
panel circuit breaker provides overall DC power protection.
The HM-1S accepts a unipolar 48 VDC power source,
which may be supplied by the Meyer PS-1 AC Adapter.
Using a DC supply enables long power cable runs with
minimal induced noise or hum, which is particularly im-
portant for recording studios and other noise sensitive
environments.
Power Requirements
The HM-1S requires a 48 VDC external power supply,
which provides these benefits:
• Low voltage wiring simplifies installation.
• Utilizes telecom 48 V supply and bus standard.
• Eliminates 50/60 Hz AC noise coupling in wiring.
The power supply input uses a male 2-pin EN3 connector.
The HM-1S can be powered by the Meyer PS-1 AC
adapter or a supply that conforms to the 48 VDC specifi-
cations detailed in this section.
Meyer PS-1 AC Adapter
Using the Meyer PS-1 AC adapter is the simplest way to
power a pair of HM-1Ss, or a single HM-1S with a sub-
woofer. The AC adapter can be purchased through Meyer
Sound and comes with two 10 ft power cables. The AC
adapter has two output connectors that are wired together
inside the supply, allowing either one connector to
drive two speakers at the end of a single cable, or one
connector and cable per speaker.
Do not connect the outputs of multiple PS-1 AC
adapters together!
For installations up to 10 HM-1Ss, using multiple PS-1
AC adapters is often the simplest and most cost-effective
solution. Since the limited output power for each supply
acts as circuit protection for light gauge cables, it is not
necessary to install circuit breaker distribution panels.
Using the PS-1 does, however, limit each 48 V line to two
speakers. The dimensions of the AC adapter are 10” x 5” x 3”.
Contact Meyer Sound for further information on the PS-
1 AC Adapter.
!
Do not use a ground-lifting adapter or cut the AC
cable ground pin.