High Definition
Audio Monitor
HD-1
OperatingInstructions
The HD-1 High Definition
Audio Monitor* is a self-contained,
precision loudspeaker for near-
field sound reproduction.
Aligned to closely approximate
a true point source radiator, the
HD-1 features exceptionally broad
directivity characteristics. Its time
delay response is tightly controlled,
with minimal deviation from linear
phase across the full frequency
range of its operation. Each unit is
individually factory-calibrated to
ensure unprecedented consistency
of performance. The HD-1 is
within 2 feet of sensitive color
video monitors. For applications
requiring closer proximity to
monitors, an optional steel-
shielded model is available.
against damage from excessive
amplifier power and ensure
graceful overload characteristics.
suitable for critical applications
ranging from professional record-
ing to psychoacoustical research.
Independent power biamplifiers
maximize system headroom,
The HD-1 is a two-way system
comprising an 8-inch cone low-
frequency driver and dome tweeter
housed in a vented cabinet. The
low-frequency driver features an
exceptionally large magnet struc-
ture and a 2-inch voice coil for
greatest efficiency and heat dissipa-
tion. The tweeter employs a
The HD-1 incorporates line-level efficiency and damping while
control electronics mounted within minimizing distortion. The low
a rear-panel chassis, including:
frequency amplifier delivers 150
watts output power, while the high
frequency amplifier provides 75
watts. Both employ complementary
power MOSFET output stages
operating class A at low-to-moder-
ate listening levels (<90 dB SPL),
and class AB at high levels.
• an active balanced input circuit
with switchable sensitivity
(+4 dBu or -10 dBV);
• an active crossover utilizing
optimized pole-zero filter
combinations to achieve acousti-
cal transparency and linear
phase;
• independent protection circuits
for each loudspeaker driver;
• dual power amplifiers for
biamplification.
specially-developed impregnated
silk dome to minimize breakup and
colorization.
The HD-1’s free-field frequency
response is flat within 1 dB from
40 Hz to 20 kHz (-3 dB at 32 Hz
and 22 kHz). It delivers high peak
SPL with >100 dB dynamic range
and extremely low distortion.
Covers are included for use during
transport.
Both drivers are of a proprietary
design, and are individually
selected for maximum linearity.
Their magnet structures employ
sophisticated field-cancelling
design techniques to minimize
magnetic field leakage, and the
cabinets may safely be placed
The driver protection circuits
employ thermo-predictive limiters
and soft peak clamps to guard
* patents pending
Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, California 94702
Sensitivity Switch
Input Connection
Operation
• For professional balanced
equipment, use the +4 dBu
setting.
• For semiprofessional and
consumer unbalanced equip-
ment, use the -10 dBV setting.
The HD-1 presents a 10 kohm
input impedance at a three-pin
XLR-type receptacle wired as
follows:
In normal operation, the front-
panel LED will glow green.
At high listening levels, the LED
may flash red on program peaks.
This indicates the onset of over-
load, where the loudspeaker
Pin 1 Audio common
Pin 2 Signal low (-)
Pin 3 Signal high (+)
Case Earth (AC) ground
Note that the -10 dBV setting is
more sensitive (designed for lower
signal levels) than the +4 dBu
setting:
protection limiters are activated.
If the LED is continuously red
for an extended period (8 hrs.),
thermal damage may result.
Shorting any input connector pin
to the case may form a ground
loop and cause hum.
• +4 dBu position:
1.23 VRMS = 114 dB SPL RMS
• -10 dBV position:
Calibration Port
0.316 VRMS = 114 dB SPL RMS
Standard audio cables with
XLR-type connectors may be used
for balanced signal sources. Unbal-
anced sources will require an in-
line adapter.
The calibration port is for factory
use only. Do not apply external
voltages to any of the connector
pins.
Driving the HD-1 from a +4 dBu
source with the switch set to -10
dBV will result in increased noise.
Troubleshooting
Problem
Symptom
Power switch on but switch
Possible Cause
Action
No sound
Bad AC connection
Blown fuse
Check AC outlet and power
cord.
not lit
Power switch on and lit, LED
out
Replace fuse. Check voltage
selector and AC line.
Signal source disconnected
Power switch on and lit, LED
lit
Check input cables, connec-
tots and signal source.
AC voltage selector incor-
rectly set
Turn off HD-1. Check AC
outlet voltage and selector
switch setting.
Distorted sound with hum
Turn off HD-1. Check AC
outlet voltage; if low, contact
power company.
Selector switch setting correct
Power brownout
Low sound levels
Insufficient drive from signal
source
Increase source equipment
output level.
Input sensitivity incorrectly set
Set input sensitivity switch to
-10 dBV
Hiss
Input sensitivity incorrectly set
Program material
Check sensitivity switch and
source equipment output.
Sensitivity setting correct
Program material OK
Stop playback. If hiss
disappears, check program.
Source equipment malfunc-
tion
Unplug input connector. If
hiss disappears, check
source equipment.
Distorted or intermittent
sound
Bad input connection
Check input cables
Input cables OK
Defect in signal source
equipment
Substitute known good signal
source. If problem stops,
replace signal source
equipment.
3
Obtaining Service
To obtain service:
4) You will be given an RA (Return
Authorization) number for job
tracking. Refer to this number
on shipping materials and in all
correspondence concerning the
repair. Shipping charges are the
responsibility of the purchaser.
The HD-1 Monitor is protected
by Meyer Sound’s Limited One-
Year Warranty. For complete
information regarding terms and
conditions, refer to the printed
warranty statement that is packed
with the system.
1) Contact your dealer or call
Meyer Sound.
2) If you are calling Meyer Sound,
have the serial number(s) of the
unit(s) at hand for reference. Ask
for Customer Service, and be
prepared to describe the prob-
lem clearly and completely.
3) If the problem cannot be re-
solved over the phone, you must
return the unit for service.
To extend coverage to two full
years, and assure notification of
product improvements or literature
updates, complete and mail the
enclosed Warranty Registration
Card.
Any attempt to modify or replace
components of the HD-1 will
invalidate your warranty. Service
must be performed by a Meyer
Sound service center.
Specifications
Acoustical - HD-1 System
Notes:
Frequency Response1
32 Hz to 22 kHz
1. Subject to room loading. Specified for
8 feet actual distance between HD-1
cabinet and a single boundary
surface.
Free Field
-3 dB at 32 Hz and 22 kHz
1 dB from 40 Hz to 20 kHz2
Maximum SPL
125 dB SPL peak capability (120 dB @ 1 meter)
> 100 dB (noise floor 20 dBA @ 1 meter)
60 degrees horizontal and vertical
Signal-to-Noise Ratio
Coverage Angle (-6 dB)
2. One-third octave resolution.
Unless otherwise specified, all acoustic
and magnetic measurements are
performed at one-half meter from front
baffle on tweeter axis.
Audio Input
Type
Electronically balanced, 10k ohms impedance
XLR (A-3) female
Connector
Nominal Input Level
Accepts either +4 dBu or -10 dBV, switchable
Physical Dimensions
Amplifiers
Type
Complementary power MOSFET output stages
Power Output
Low Frequency
High Frequency
THD, IM, TIM
150 watts burst capability
75 watts burst capability
< .02 %
12.00"
9.20"
1.40"
Crossover
Optimized pole-zero filter combinations to
complement transducer response and to achieve
acoustical transparency and flat phase
16.53"
15.65"
Transducers
Low Frequency
High Frequency
8" diameter cone (2" voice coil)
1" dome tweeter (1" voice coil)
5.00"
3.85"
13.20"
1.40"
16.00"
AC Power
3-pin IEC male receptacle. Voltage selector switch
for 100/120/220/240 VAC, 50 or 60 Hz (accepts
voltages from 90 to 260 VAC)
14.00"
Physical
Dimensions
16" H x 12" W x 14" D (+ 2" additional depth for
amplifier chassis and HF dome clearance)
51 lbs. (23 kg.)
Weight
05.550.026.01 A2
Copyright © 1994, Meyer Sound Labora-
tories, Inc. All rights reserved.
Stray magnetic field
<1 Gauss in all directions from cabinet
4
|