NHT Studio Monitor A 20 User Manual

A-20  
Owners Manual  
A-20 Left Monitor Serial Number:  
A-20 Right Monitor Serial Number:  
A-20 Control Amplifier Serial Number:  
Copyright 2001 NHTPro, a Recoton Corporation Brand  
INTRODUCTION:  
Thank you for your selection of the A-20. Your studio monitors are a critical element in the countless decisions made  
during recording, mixing, mastering and other key aspects of audio production. They must deliver a transparent, neutral  
and revealing assessment of sound, so that you have the information you need to choose and place microphones, set  
Eq’s, balance mixes... In other words, deliver exceptional product. The A-20 is capable of state of the art sonic  
resolution and flexibility. Investing time to learn about the A-20’s features and operation will reward you with the  
best possible performance.  
If you require assistance at any time during or after the setup process, call our Customer Service Hot Line at (800)-NHT-  
again for your confidence in our products!  
GETTING STARTED:  
The A-20 is unique in that it combines a dedicated control amplifier with loudspeaker monitor cabinets, using controlled  
impedance cables that actually form part of the crossover network. By designing the system as an integral package in  
this manner, many of the advantages of self-powered speakers can be realized without attendant performance compromises.  
However, it must be recognized that the control amp, cables and monitors are an inseparable package.  
The A-20 must only be used with the A-20 Control Amp, cables, and vice versa.  
The following are included in the Control Amplifier carton:  
1 ea. - Control Amplifier  
1 ea. - 6' IEC Power Cord  
1 ea. - Warranty Registration Card  
2 ea. - 20' Monitor Output Cables  
4 ea. - 10-32 Rack Mounting Screws  
8 ea. - Plastic Insulating Washers  
Screws  
Insulating  
Washers  
The A-20 Control Amplifier may be used on a shelf, or mounted in a standard 19” equipment  
rack using the screws and washers supplied. For rack mounting, remove and retain the four  
feet from the bottom of the amp chassis using a #2 Philips screwdriver. Two vertical rack  
spaces are required, but we recommend you leave at least one additional open space  
above and below the A-20 for improved cooling, as you would with any high power amplifier.  
For table or shelf use, the four feet must remain attached to allow for air circulation. As a  
starting point for speaker placement, align the back of the enclosures parallel to the rear wall,  
with the angled fronts facing in towards you. For more detailed speaker placement  
information see page 7.  
A-20  
Amplifier  
Front Panel  
Rack Rail  
Fig. 1: Rack Mounting Detail  
Monitor Output Cables  
Signal flow  
Signal flow  
1
+4  
MF  
+11  
-3  
POWER  
2
0
FF  
NF  
M
-10  
100  
MODE  
PHONES  
SENSITIVITY  
BOUNDARY  
POSITION  
SPL  
TMP  
VAC  
Control  
Amplifier  
A-20  
To AC Line  
Signal flow  
Corel  
Jpg  
.
Fig. 2 Typical System Configuration  
SYSTEM CONNECTIONS:  
CAUTION: MAKE ALL CONNECTIONS WITH THE AC POWER OFF!  
CAUTION: CONNECTING THE OUTPUT OF THE A-20 CONTROL AMPLIFIER TO ANY  
EQUIPMENT OTHER THAN THE A-20 OR C-20 MONITOR MAY CAUSE  
EQUIPMENT DAMAGE.  
CONTROL AMPLIFIER INPUT SECTION:  
The A-20 Control Amplifier accepts both balanced and unbalanced inputs on either XLR or 1/4” TRS connectors. These  
connectors are hardwired in parallel within the A-20 to allow for convenient equipment chaining, but only one signal source  
should be physically connected to the unit at any time. Figure 3a shows the proper wiring schematic for each type of  
connector. Since there are so many different connector types and signal levels employed by source equipment, some  
experimentation may be necessary, keeping in mind that the A-20 can accept a wide range of signals and has an  
input sensitivity control on the front panel.  
2
PIN SIGNAL  
A-20 INPUT  
SOURCE  
3
1
1
2
3
GND  
+ (SIGNAL)  
- (GND)  
2
1
2
3
1
+
_
3
Shield  
XLR  
TRS  
Fig. 3b Unbalanced Wiring Diagram  
Fig. 3a Balanced Wiring Diagram  
SPEAKER CABLE CONNECTIONS:  
The A-20 includes two 20’ special purpose cables to connect the Control amplifier to the Monitors. While these cables look  
similar to standard microphone cables, they are constructed with lower and more consistent conductor impedance. Portions  
of the A-20’s crossover circuitry are located in both the amplifier and speaker enclosures, and the cables supplied are an  
important part of this electrical network. This allows the speaker cables to function as a neutral and transparent component  
in the system. Replacing or extending the supplied cables with any other type will have a varying, and only partly predictable  
impact on the sound of the A-20. If your installation requires the use of alternative cables, you may consult the table listing our  
shown in Fig. 3a. These considerations aside, using the Vergence cables to connect the control amplifier is quite simple and  
straight forward. Both the amplifier and the monitors are marked with the appropriate “left” and “right” channels. Fit the  
XLR connectors into the corresponding connectors on the control amplifier and monitors until the connector locks.  
WARNING: IF USING CABLES OTHER THAN THOSE SUPPLIED WITH THIS SYSTEM, BE SURE  
THAT NO CONDUCTIOR IS WIRED TO THE XLR CASING. FAILURE TO  
DO SO  
MAY CONSTIT UTE A RISK OF ELECTRIC SHOCK.  
A-20 Monnitor  
Left  
A-20 Monitor  
Right  
CAUTION  
RIGHT  
LEFT  
NHTPro  
MODEL A-20 CONTROL AMPLIFIER.  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
WARNING: SHOCK HAZARD-DO NOT OPEN.  
AVIS: RISQUE DU CHOC ELECTRONIQUE-  
NE PAS OUVRIR.  
SERIAL NO: A20-A-10001  
NHTPro  
BENICIA, CALIFORNIA, U.S.A.  
CAUTION:  
INPUT  
FOR CONTINUED PROTECTION AGAINST  
RISK OF FIRE REPLACE ONLY WITH SAME  
TYPE 250V FUSE.  
MADE IN TAIWAN G1  
2
3
1
PIN SIGNAL  
1
2
3
GND  
CAUTION:  
INPUT VOLTAGE  
FUSE TYPE:  
T9A 250V FOR 110/120V.  
T5A 250V FOR 220/240V.  
2
1
+
_
CONNECTING OUTPUTS TO ANY  
PRODUCT OTHER THAN A-20 or  
C-20 MONITORS MAY RESULT IN  
SEVERE EQUIPMENT DAMAGE.  
LISTED  
AUDIO EQUIP  
3
U
L
XLR  
TRS  
50/60 Hz - 950W  
Fig. 4 A-20 Control Amplifier Rear Panel  
USING THE A-20 CONTROL FUNCTIONS:  
The A-20 controls are designed for utility and repeatability under varying conditions. You should find the effects of the  
controls sonically subtle, with little impact on the basic character and accuracy of the speaker. We encourage experimentation  
tofinetunethesystemtotherequirementsofyourparticularinstallation.  
1
MF  
+4  
+11  
-3  
POWER  
2
0
NF  
FF  
M
-10  
100  
MODE  
PHONES  
SPL  
VAC  
TMP  
SENSITIVITY  
BOUNDARY  
POSITION  
Control  
Amplifier  
A-20  
Fig. 5 A-20 Control Amplifier Front Panel  
POWER INDICATORS:  
Just to the left of the power switch on the A-20 Control Amplifier are two status LED's. The upper (green) LED  
lights up indicating there is AC power to the amplifier and the POWER SWITCH is in the “on”position. The lower (red)  
LED indicates a clipping or overload condition. Occasional flashing of this indicator is a gentle warning you are reaching the  
system’s limits. If the red LED glows continually, severe clipping is occurring. The input signal or system gain should be  
reduced to avoid the risk of possible system damage.  
SYSTEM STATUS DISPLAY:  
A unique feature of the A-20 Control Amplifier is the System Status Display located in the center of the front panel.  
Small LED’s indicate which mode is being displayed; green for average SPL, yellow for AC line voltage, and blue for heat  
sink temperature. The square “Mode” switch to the right of the System Status Display selects the desired mode.  
SPL: This is the long term average sound pressure level calibrated at 2 meters from a stereo pair, and derived from  
the amplifier output voltage. Peak sound levels are ignored. The readout is designed to inform the user of overall listening  
levels, and to help realize consistent monitoring conditions from hour to hour, session to session and room to  
room. Levels under 68 dB are shown as “00”; levels over 120 dB are shown as “HI”. Since monitoring level has a  
profound influence on the perception of sonics, periodically checking your listening levels helps to assure consistent  
results. Making an effort to combat long term ear fatigue can help you avoid the heartbreak of harsh morning after  
realities.  
VAC: This is a readout of the AC power line voltage being supplied to the A-20. It is useful for assuring that power  
conditions are correct and sufficient for all the equipment on the circuit. Sustained readings below 110 V may limit  
your maximum output levels, and could indicate that the AC circuit is overloaded. Continuous readings above 125 V  
indicate an AC circuit problem, which could lead to amplifier failure.  
TMP: This is a reading of the output heat sink temperature in degrees Centigrade. Typically, you should expect this  
to run between 50°C and 80°C, depending on listening and ambient conditions. If you find that your Control  
Amplifier unit tends to run hotter than 80°C, it is recommended that you improve the ventilation around it. Note that  
the A-20 Control Amplifier will automatically shut down if the heat sink temperature reaches 100°C.  
SENSITIVITY:  
This control is used to change the input sensitivity with settings at; -10dB, -3dB, +4dB, +11dB and (M)ute providing  
noise free, consistent gain matching with a wide variety of equipment. The proper setting is the lowest sensitivity possible  
(highest dB number) which allows the speaker to reach the maximum desired output without source clipping. Professional  
devices typically spec full output at +4dB, most consumer audio products reach full output at -3dB, and most computer  
sound cards have a full scale output of -10dB. Consult the owner’s manual for the device connected to the Control  
Amplifier for its output level specifications and set the SENSITIVITY control accordingly.  
BOUNDARY CONTROL:  
Reflective boundaries, such as floors, walls, even table tops, reinforce a speaker’s low frequency output. Conversely,  
placing speakers out into a room decreases bass response. The highest low frequency output is with the BOUNDARY  
control in the “0” position, which assumes no significant boundary reinforcement is present. Each control step  
attenuates low frequencies by 1.5 dB (at 50 Hz), with rapidly decreasing effect above 300 Hz. Refer to the diagram  
in Fig. 6 for information on setting the control appropriately.  
Quarter/Half Space  
Quarter Space  
Whole Space  
Half Space  
Half/Whole Space  
1
1
1
1
1
2
0
2
0
2
0
2
0
2
0
BOUNDARY  
BOUNDARY  
BOUNDARY  
BOUNDARY  
BOUNDARY  
Fig. 6. Boundary Control Settings Diagram  
POSITION CONTROL:  
Near-field monitoring reduces the effect of room acoustics on the signal, and provides greater sonic detail. Mid- and  
far-field listening reveals aspects of recorded ambience and is more representative of end use. However, a speaker’s  
upper frequency power response changes with distance, due to room influences and air absorption. The A-20 may be  
adjusted for flat response at various listening distances. The maximum high frequency output is obtained with the  
control in the “FF” (far-field) position. Each control step attenuates 20 kHz by an additional .75 dB (towards  
the near-field position) with no effect on frequencies below 3 kHz. See Fig. 7 for appropriate POSITION control  
settings based on listening distances.  
Listener Distance  
0’  
2.5M  
Far-Field  
3M  
1.5M  
2M  
1 M  
A-20  
Monitor  
Mid-field  
Near-field  
MF  
MF  
MF  
MF  
MF  
NF  
FF  
NF  
FF  
NF  
FF  
NF  
FF  
NF  
FF  
POSITION  
POSITION  
POSITION  
POSITION  
POSITION  
Fig. 7. Position Control Settings Diagram  
SPEAKER PLACEMENT:  
The A-20 Monitor System is intended to provide consistent performance over a wide range of placement situations.  
This is accomplished through the use of electrical controls, wide dispersion drivers, advanced enclosure design and  
carefully chosen crossover characteristics. Nevertheless, it is always worth investing time and effort experimenting  
with optimum loudspeaker placement. In all cases, A-20 Monitors should be set up symmetrically equidistant from  
the listening position; the left speaker and right speaker should be at the same relative positions with respect to the  
primary listening area. This is important in order the hear a proper stereo sound stage. The speaker baffles angle in  
towards the listening position with the loudspeaker backs parallel to one another. A good starting point can be  
found in Figure 8 below. Ideally, the tweeter height should be on axis with your ears, or slightly above. Also,  
remember that nearby reflective surfaces can alter impulse response, blur imaging and change tonality.  
D
Listening Position  
Fig. 8 Ideal Monitor Placement  
SYSTEM OPERATION:  
The A-20 is capable of very high output levels, especially when listening in the near-field. Protect your ears and use common  
sense. Still, every speaker system has its limits. Harsh breakup at extremely high volume, or heat emanating from the drivers is  
an indication that the system has exceeded its output limits and you should lower the playback level. Watch for excessive  
lighting of the front panel overload indicator on the Control Amplifier. Speaker damage most often occurs from sustained  
high volume levels, not from transient sounds or brief musical peaks.  
A-20 MONITOR SYSTEM CARE:  
Except for the occasional flattering comment, your A-20 System needs no regular maintenance. Never attempt to clean the A-  
20 monitor driver units except for very light feather dusting. The A-20 monitor cabinets and the A-20 Control  
Amplifier front panel can be cleaned using a damp, soft cotton cloth first sprayed with a mild, non-abrasive glass  
cleaner. Never spray the speaker or amplifier directly! Avoid silicone and oil based cleaners or treatments.  
NEED HELP?  
Technical Support can be reached several ways: Telephone us (800)-NHT-9993 (648-9993), E-mail us at:  
[email protected], Fax us at: (707) 747-1252 or write us at: NHTPro, 6400 Goodyear Rd., Benicia, CA 94510. Or visit  
SYSTEM SPECIFICATIONS:  
Type: Modular, two- piece powered near/mid/far field monitor.  
Configuration: 2-way acoustic suspension.  
Woofer: 6.5" curvilinear treated paper. Butyl surround.  
Tweeter: 1" metal dome, textile surround, ferrofluid cooled and damped.  
Magnetic Shielding: Partial, 12-18” working distance from PC monitor recommended.  
PERFORMANCE SPECIFICATIONS:  
Amplifier Power: 250W (continuous RMS/ch), 400W (100ms peak).  
Peak Acoustic Output: 117 dB SPL (100ms pink noise @ 1M).  
Residual hum/noise: <10 dB SPL @ 1M.  
System THD @ 90 dB SPL: <0.4% (100Hz ~ 10kHz @ 1M).  
Response: +/- 2 dB (1/3 oct. swept noise): 48Hz ~ 20kHz@ 1M, 45Hz ~ 20kHz @ 2M.  
-6dB LF cutoff: 40Hz (in-room response).  
Loudspeaker Dimensions/Wgt.: 14" h x 7.5" w x 11.9" d, 19 lbs.  
Loudspeaker Materials: 0.75" MDF w/high pressure laminate (internal + external).  
Control Amplifier Dimensions/Wgt.: 3.5" h x 19" w x 13.375" d/37 lbs.  
FEATURES/CONTROLS:  
Connectors: Input: XLR, TRS.  
Output to monitor: XLR.  
Controls:  
Sensitivity: 5 position (-10dB,- 3dB, +4dB, +11dB, Mute).  
Boundary: 5 position (0.0, 0.5, 1.0, 1.5, 2.0 representing walls).  
Position : 5 position, near(1M), near-mid(1.5M), mid(2M), mid-far(2.5M), far (3M~).  
Power: On, off.  
Display Mode  
Display:  
C).  
Switchable: SPL Output (68dB ~ 120dB), Line Voltage(90 ~ 135VAC), Heat Sink Temp.(20 - 99o  
LED’s:  
Other:  
Power, Overload.  
Headphone Output (insertion interrupts main output).  
NHTPro  
6400 Goodyear Rd.  
Benicia, CA 94510  
ph: (707)748-5940  
fx: (707)747-1252  

JVC AV 29MT16 User Manual
KitchenAid KECC508RPW04 User Manual
MASS Engineered Design C3H 15 User Manual
Miele CS 1122 User Manual
Motorola L304 User Manual
Panasonic CT 24SX11 User Manual
Panasonic DMR E60 User Manual
Philips 14PT1324 User Manual
Philips 21PT5402 User Manual
Philips DVD Recorder DVDR3545V User Manual