Crest Audio LH3 LOUDSPEAKER User manual

Full Range
Other LH series loudspeakers
SERIES
Features Description
• Smooth frequency response characteristics
• 500 Watt continuous rated woofer
• 140 Watt continuous rated mid-range compression driver
• 90 degree x 40 degree constant directivity horn with 2" throat
• High power crossover components
• Neutrik Speakon®input connectors, with automatic biamp switching
• 15 degree trapezoidal cabinet design
• Recessed steel handles with comfortable round handgrip
• Heavy gauge metal grill with black, powder-coat finish
• High-impact resistant polypropylene cabinet corners
• Rugged stand adapter
• Exterior grade 3/4", 7-ply all poplar APA-1 plywood
• Scuff and weather resistant, black Hammer-Head™ finish
The Crest Audio LHTM3 is a newly designed, three-way speaker system com-
prised of one 15" high-power woofer, one 8" heavy-duty mid-range, and a 2"
exit compression driver coupled to a 90° x 40° constant directivity horn.
As with all LHTM full-range speakers, this unit can be driven in full-range or
biamp mode simply by plugging into the desired jack on the input plate. The
LHTM3 has a trapezoidal shaped cabinet, rather than the more traditional rec-
tangular shape.This allows cabinet arrays to be constructed more easily. This
shape also greatly reduces the build-up of internal standing waves. Standing
waves are internal amplitude peaks that occur due to reflections within the
cabinet at frequencies related to the internal square dimensions of the cabi-
net. The trapezoidal shape resists the formation of standing waves by caus-
ing the internal reflections to cancel rather than reinforce each other. This
ensures a minimum of mid-bass and mid-range coloration of the reproduced
sound due to standing waves within the cabinet.
The LHTM3 is constructed of very high quality 3/4", 7-ply all-poplar plywood,
which is void-free, medium density and warp-resistant.The LHTM3 cabinet is fin-
ished with Crest Audio’s durable black Hammer-Head™ poly-coating. Polymer
corners are also added to provide further protection to the cabinet. A black, pow-
der-coated heavy-gauge metal grill covers the lower section of the front of the
cabinet to protect the low and mid frequency drivers from unforeseen impacts.
Crest Audio’s protection circuit for mid and high frequency driver protection is
included as a standard feature. The input signal is routed through the protec-
tion circuit in both full-range and bi-amp modes of operation. When the mid
and/or high frequency drive level to the LH3 exceeds predetermined thresh-
olds, the protection circuit is temporarily engaged. This subtly decreases the
signal level applied to the mid and/or high frequency drivers so that they will
not be damaged due to long term overpowering. Short duration transients will
not be attenuated by the protection circuit and thus have the potential to dam-
age the drivers.The protection circuit is realized through the use of a dynam-
ically resistive component in conjunction with a switched padding circuit.
An additional feature in the crossover circuitry is a mid-range contour switch.
This switch allows a choice between flat (HIGH position) and mildly attenuat-
ed (NORMAL position) mid-range frequencies. The position of this switch is
purely dependent on venue and personal sonic taste. As a suggestion, the
NORMAL position is more suitable for live (highly reflective, long reverb time)
venues. Whereas, the HIGH position is more suitable in venues where the
reverb time is relatively short.This switch is located on the rear panel input plate
and is actuated with a suitable tool such as a flat screwdriver tip, or door key.
LHTM3
Loudspeaker
LHTM3
LHTM1
LHTM2
LHTM4
LHTM5M
LHTM6M
LHTM7M
500W
600W
1,000W
1,200W
400W
500W
1,000W
1,000W
1,200W
2,000W
2,400W
800W
1,000W
2,000W
2,000W
2,400W
4,000W
4,800W
1,600W
2,000W
4,000W
Power Handling Continuous Program Peak

Specifications LHTM3 Loudspeaker
Power Handling
There are many different approaches to
power handling ratings. Crest Audio rates
this unit’s system power handling using a
modified form of the AES Standard 2-
1984. Utilizing audio band limited (20 Hz
- 20 kHz) pink noise with peaks over four
times the RMS level, this strenuous test
signal assures the user that every portion
of this system can withstand high inpact
music. The test signal contains large
amounts of low frequency energy, effec-
tively simulating the frequency content of
live music situations. High frequency test
signals expose the speaker system to
synthesized tones that may extend
beyond audibility. This rating is contingent
on having a minimum of 3 dB of amplifier
headroom available so as to ensure that
clipping does not occur.
Frequency Response
This measurement is useful in determin-
ing how accurately a given unit repro-
duces an input signal. The frequency
response of the LH3 (Figure 1) is meas-
ured at a distance of 1 meter using a 1
Watt (into the nominal impedance) swept-
sine input signal.
Directivity
Beamwidth is derived from the -6 dB
points from the polar plots which are
measured in a whole space anechoic
environment. Q and Directivity Index
(Figures 3 & 4) are plotted for the on-axis
measurement position. These are specifi-
cations that provide a reference to the
coverage characteristics of the unit. These
parameters provide insight for proper
placement and installation in the chosen
environment.
20 50 100 200 500 1k 2k 5k 10k 20k
Frequency (Hz)
1
10
100
Q & Directivity Index
Q
Figure 4
20
10
Di
0
20 50 100 200 500 1k 2k 5k 10k 20k
Frequency (Hz)
30
40
60
80
100
140
180
300
360
Beamwidth (Degrees)
Beamwidth
Vertical
Horizontal
Figure 3
20 50 100 200 500 1k 2k 5k 10k 20k
Frequency (Hz)
1
2
3
5
10
20
30
50
100
Impedance
Z
()
Figure 2 Lower Curve: Midrange Contour = High, Upper Curve: Midrange Contour = Norm
20 50 100 200 500 1k 2k 5k 10k 20k
Frequency (Hz)
70
80
90
100
110
dB SPL (re 20 Pa)
Amplitude Response (1W 1m On-Axis)
Figure 1 Lower Curve: Midrange Contour = Norm, Upper Curve: Midrange Contour = High

Specifications LHTM3 Loudspeaker
Horizontal Polars
Vertical Polars
-90o
-60o
-30o
0o
30o
60o
90o
125 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
250 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
500 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
1000 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
2000 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
4000 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
8000 Hertz
-90o
-60o
-30o
0o
30o
60o
90o
16000 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
125 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
250 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
500 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
1000 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
2000 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
4000 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
8000 Hertz
0o
30o
60o
90o
-30o
-60o
-90o
16000 Hertz

Specifications LHTM3 Loudspeaker
Frequency Response, 1 meter on-axis,
swept-sine in anechoic environment:
Usable Low Frequency Limit (-10 dB point):
Power Handling:
Passive High Frequency Section:
Sound Pressure Level, 1 Watt, 1 meter in
anechoic environment:
Mid / High Frequency Section:
Maximum Sound Pressure Level (1 meter):
Mid / High Frequency Section:
Radiation Angle measured at -6 dB point
of polar response:
Transducer Complement
Low Frequency Section:
Mid Frequency Section:
High Frequency Section:
Box Tuning Frequency:
Crossover Frequency (internal passive):
Recommended Active Crossover
Frequency Region and Slope
Mid Frequency - High Frequency:
Time Offset:
Impedance (Z):
Passive MF/HF:
High Frequency:
Input Connections:
Enclosure Materials & Finish:
Dimensions (H x W x D):
Net Weight:
LHTM3 Loudspeaker
53 Hz to 20 kHz (±3 dB)
40 Hz
Full Range:
500 W continuous (63.2 V RMS)
1,000 W program
2,000 W peak
150 W continuous (34.6 V RMS)
300 W program
600 W peak
Full Range:
97.0 dB SPL, (2.83 V input)
104 dB SPL, (2.83 V input)
Full Range:
126.8 dB SPL continuous
132.8 dB SPL peak
134.5 dB SPL continuous
140.5 dB SPL peak
90 degrees horizontal x 40 degrees vertical.
1x 15 in. woofer, vented basket
1x 8 in. mid-range
2.0 in. exit / 75 mm voice coil compression driver on a CD horn
Fbox: 36 Hz
Low Frequency - Mid Frequency: 500 Hz
Mid Frequency - High Frequency: 3,700 Hz
500 Hz at 18 dB/octave
Low Frequency: 0.00 ms
Mid Frequency: -0.30 ms
High Frequency: 0.60 ms
Full Range:
Nominal: 8.0 Ω
Minimum: 6.4 Ω
Nominal: 8.0 Ω
Minimum: 8.9 Ω
Nominal: 8.0 Ω
Minimum: 6.9 Ω
2x Neutrik Speakon®4 conductor input jacks, 1x Neutrik Speakon®4 conductor
biamp switching input jack
3/4" 7-ply premium, exterior grade, all-poplar, void-free plywood. Material conforms
to APA-1 specification. Finished in black Hammer-Head poly-coating.
Front: 33.5 in. x 22.38 in. x 19.75 in. 851 mm x 568 mm x 502 mm
Rear: 33.5 in. x 12.75 in. x 19.75 in. 851 mm x 324 mm x 502 mm
120 Lbs. (54.4 kg)
Crest Audio Inc.
16-00 Pollitt Dr. Fair Lawn, NJ 07410
TEL: [phone] FAX: [phone]
www.crestaudio.com
*80304808*
Crest Audio reserves the right to make improvements in manufacturing or design which may affect specifications.
8/22/01
v.1.5
Architects’ & Engineers’ Specifications:
The loudspeaker system shall have an operat-
ing bandwidth of 53 Hz to 20 kHz. The nominal
output level shall be 97 dB when measured at
a distance of one meter with an input of one
Watt. The nominal impedance shall be 8.0
Ohms. The maximum continuous power han-
dling shall be 500 Watts, maximum program
power of 1,000 Watts and a peak power input
of at least 2,000 Watts, with a minimum ampli-
fier headroom of 3 dB. The nominal radiation
geometry shall be 90 degrees in the horizontal
plane and 40 degrees in the vertical plane. The
outside dimensions shall be 33.5 inches high
by 22.38 inches wide by 19.75 inches deep. The
weight shall be 120 pounds. The loud-speaker
system shall be a Crest Audio model LHTM3.