Meyer Sound HM-1S User Manual
Operating Instructions
HM-1S
Self-Powered
Studio Monitor
Patents Pending
Copyright © 1998
Meyer Sound Laboratories, Inc.
All rights reserved
Part # 05.059.004.01 Rev A2
Contents
Introduction .......................................................... 3
Power Requirements ............................................ 3
Power Cable Requirements.................................. 5
Audio Input ........................................................... 5
The HM-1S Subwoofer ......................................... 5
Symbols Used
These symbols indicate important safety or operating features in this booklet and on the chassis.
!
Dangerous voltages:
risk of electric shock
Pour indiquer les risques
résultant de tensions
dangereuses
Zu die gefahren von
gefährliche spanning zeigen
Para indicar azares
provengo de peligroso
voltajes
Important operating
instructions
Pour indequer important
instructions
Zu wichtige betriebsanweisung und unter-
haltsanweisung zeigen
Para indicar importante funcionar
y mantenimiento instrucciones Armadura o chassis Tierra proteccionista
Cooling and Fan Installation ................................ 16
Protection and Limiting ....................................... 16
Safety Summary ................................................. 17
Rear Panel Connectors ....................................... 18
Dimensions ......................................................... 18
Frame or chassis
Masse, châssis
Rahmen oder chassis
Protective earth ground
Terre de protection
Die schutzerde
Declaration of Conformity
According to ISO/IEC Guide and EN 45014
Name: Meyer Sound Laboratories
Address: 2832 San Pablo Avenue
Berkeley, California 94702-2204, USA
conforms to the following Product Specifications:
Safety: EN 60065: 1994
EMC: EN 55022: 1987 - Class A
IEC 801-2: 1984 - 8 kV
IEC 801-3: 1984 - 3 V/m
IEC 801-4: 1984 - 0.5 kV Signal Lines,
1.0 kV Power Lines
The product herewith complies with the requirements of t he
Low Voltage Directive 73/23/EEC and the EMC Directive 89/336/EEC.
Office of Quality Manager
Berkeley, California USA
April 1, 1997
declares that the product:The Manufacturer:
Product Name: HM-1S
Product Options: All
Environmental Specifications for Meyer
Sound Electronics Products
Operating temperature: 0° C to +45° C
Nonoperating temp: < 40° C or > +75° C
Humidity: to 95% at 35°C
Operating altitude: to 4600 m (15,000 ft)
Nonoperating altitude: to 6300 m (25,000 ft)
Shock: 30 g 11 msec half-sine
on each of 6 sides
Vibration: 10 55 Hz (0.010 m
peak-to-peak excursion)
2
Introduction
Power Requirements
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-correction circuitry provides superb imaging without the off-axis
cancellation effects, back-wave interference, and IM distortion 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 concentrically-mounted, 1-inch soft-dome high-frequency driver.
A constant-directivity, high-frequency horn affords a symmetric 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 placement 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 HM1S. 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, resulting 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 finished 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 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 specifications 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 subwoofer. 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 PS1 AC Adapter.
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 rearpanel 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 important for recording studios and other noise sensitive
environments.
!
Do not use a ground-lifting adapter or cut the AC
cable ground pin.
3
Power Supplies for Larger Systems
If an installation includes more than 10 speakers, or
requires several speakers to operate from a single 48 V
line, a single, high-output power supply should be
considered. The following sections provide current and
voltage specifications for the HM-1Ss power requirements.
Current Ratings
The wide dynamic range of audio signals normally causes
a high peak-to-RMS ratio in an amplifiers DC supply
currents. The HM-1S has internal storage circuits to
minimize the peak-to-average ratio, which
reduces the peak power rating required by the
supply;
allows efficient use of switched-mode power sup-
plies which have similar peak and continuous ratings.
The following table lists the current and power draw for a
single HM-1S at light, moderate, and maximum operating
levels.
An HM-1S with subwoofer draws 0.4 ADC, 20 W in a
quiescent state.
Voltage Ratings
The voltage operating range for the HM-1S is 48 VDC
nominal, 52 VDC absolute maximum, and 35 VDC
minimum without shutoff.
Each HM-1S draws 0.4 ADC, 20 W in a quiescent state.
The RMS current is measured over a 500 ms integration
time. The peak current is measured over a 10 ms integration
time.
Each HM-1S can drive a slaved Meyer subwoofer from a
connection on the amplifier panel. Adding the subwoofer
increases the amplifiers output current, which increases
the power supply current. The current and power ratings
for an HM-1S and a subwoofer are listed in the following
table at light, moderate, and maximum operating levels.
Allowing operation down to 35 VDC provides two benefits. First, a moderate voltage drop (up to 8 V) for long
DC power cables has a minimal impact on audio performance, enabling the use of light-gauge cables for most
installations.
Second, since some switched-mode power supplies
slowly foldback the voltage if they experience current-
limit, power supplies with lower power (current) ratings
can be used efficiently. Since supplies with lower power
ratings typically experience current-limit when the HM1S is at continuous limiting, some voltage drop and loss
of headroom is acceptable provided the voltage does
not drop below 35 VDC. At 35 V, the maximum current
draw is 25% lower than the values stated in the preceding
tables.
NOTE: If the HM-1S will not be driven at continuous limiting,
a power supply that satisfies the moderate specifications
for voltage and current can be used safely without risk of
sonic degradation or interruption.
It is important to understand how the selected power
supply responds to current-limit, particularly for switchedmode supplies. Some supplies trip off and must be reset
manually, while others remain off for a period of time and
reset automatically. In both cases, the HM-1S suffers
4
audio interruption. In the third, and preferable case,
supplies that feature voltage foldback allow brief periods
of current-limit without audio interruption; for this reason,
we recommend using such supplies.
The HM-1S does not require tight voltage regulation and
operates down to 35 V although peak SPL values are
reduced. This operating voltage flexibility allows for wiring loss and voltage foldback without interruption or
degradation of the audio signal.
A single HM-1S attached to a 100 ft 18 AWG cable (1.27
Ω total) produces a 6.4 VDC loss at the speaker (41.6 V)
during maximum audio bursts (5 A, 0.5 s). This results in
a small loss in peak SPL.
Audio Input
Many high power industrial supplies (15 kWatt) are
available for 19 EIA racks that are suitable for large
installations with equipment rooms. Distribution panels
with branch circuits can be used economically with up to
8 HM-1Ss on a branch. Contact Meyer Sound for information on tested and approved supplies.
Power Cable Requirements
Each HM-1S draws a maximum of 3 Arms and 5 Apk
from a 48 V power supply at peak SPL. The cabling
between the 48 V supply and the speaker adds resistance to the circuit and produces a voltage drop at the
speaker. Decreasing the voltage at the speaker compromises the peak SPL so cable resistance should be
minimized.
For best sonic performance, avoid voltage drops greater
than 8 V at the speaker. Voltage drops greater than 15
V may cause the speaker to mute or distort. The maximum round-trip resistance for a cable attached to a
single HM-1S should be no higher than 1.6 Ω, which
keeps the voltage drop below 8 V during the maximum
current draw of 5 Apk.
The following table helps select cable gauges for various
cable lengths.
The HM-1S has an input impedance of 10 kΩ and receives
its audio input signal at a female XLR connector. Pins 2
and 3 carry the input as a differential signal; pin 1 and the
case are connected to the chassis. The power and audio
cables can be jacketed in the same sheath without inducing noise to the input signal.
For best EMI immunity, it is desirable to use a twisted pair
shielded cable with the twisted pair connected to pins 2
and 3, and the shield to pin 1. However, an unshielded
twisted pair cable can be used effectively, even if it is
jacketed with the power cable.
The input is RF and ESD protected, capacitive coupled,
±50 V common mode to ground, +4 dBu nominal, +21 dBu
max. Clipping occurs at the input at 12 Vpk. The Common
Mode Rejection Ratio (CMRR) is greater than 80 dB.
The HM-1S Subwoofer
The low frequency response of an HM-1S can be extended
down to 42 Hz if used with the HM-1S Subwoofer or placed
next to a wall or ceiling (half-space loading). Each HM-1S
can power a subwoofer from the male 3-pin EN3 Sub
output connector on the rear panel. However, depending on
the loading conditions, ample low frequency energy may
be obtained by driving a single subwoofer from two HM1Ss, resulting in a correctly-summed mono signal. Cables
for connecting one HM-1S to a subwoofer and two HM-1s
to a single subwoofer are shipped with each HM-1S
Subwoofer.
The addition of one subwoofer increases the maximum
SPL of a single HM-1S by 4 dB (without sub: 116 dB SPL;
with sub: 120 dB SPL). The HM-1S Subwoofer has the
following specifications:
Transducer 10 low frequency cone driver
Enclosure/Finish Medium Density Fiberboard (MDF) /
Oak Veneer (natural or black)
Weight 33 lb (11.0 kg)
Dimensions Height: 17.5; Width: 12.3; Depth: 9.3
5
HM-1S Speaker Cable
The following drawings and procedures are provided as
an aid in the event that the speaker cable used to connect
the HM-1S to the HM-1S Subwoofer needs to be repaired
or extended. In cases where the original speaker cable
has been modified, be sure to complete the Subwoofer
Performance Verification section on page 10 of this
manual. Misalignment of the polarity between the HM-1S
and the HM-1S Subwoofer will result in a serious degradation of performance.
(Single HM-1S to HM-1S) Stereo Subwoofer Cable
M.S.P.N. 28.062.007.01
(2 HM-1S to 1 HM-1S) Mono Subwoofer Cable
Connections:
Gray wire to pin 1,
pin 2 no connection,
pin 3 no connection.
-
Connections:
pin 1 no connection,
pin 2 no connection.
White wire to pin 3.
+
M.S.P.N. 28.062.009.01
GRAY
Connections:
Gray wire to pin 1,
pin 2 no connection,
White wire to pin 3.
WHITE
6
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