SA-2
Subwoofer Amplifier
OWNER’S MANUAL
Now Hear This
535 Getty Court
Benicia, CA 94510
800-NHT-9993
IMPORTANT SAFETY INSTRUCTIONS
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION: TO REDUCE RISK OF ELECTRICAL SHOCK, DO NOT REMOVE COVER (OR BACK). NO USER SERVICEABLE PARTS INSIDE. REFER TO QUALIFIED SERVICE PERSONNEL.
The lightning flash with the arrowhead symbol, within an equilateral triangle, is intended to alert the user to the presence of uninsulated “dangerous voltage” within the product’s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons.
The exclamation point within an equilateral triangle is intended to alert the user to the presence of important operating and maintenance
(servicing) instructions in the literature accompanying the appliance.
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE.
1.READ INSTRUCTIONS - All safety and operating instructions should be read before the appliance is operated.
2.RETAIN INSTRUCTIONS - Safety and operating instructions should be retained for future reference.
3.HEED WARNINGS - All warnings on the appliance and in operating instructions should be adhered to.
4.FOLLOW INSTRUCTIONS - All operating and use instructions should be followed.
5.WATER AND MOISTUREThe appliance should not be used near water - near bathtub, washbowl, kitchen sink, laundry tub; in a wet basement near a swimming pool, etc.
6.CARTS AND STANDS - Do not place this product on an unstable cart, stand, tripod, bracket, or table. The appliance should be used only with a cart or stand that is recommended by the manufacturer.
7.VENTILATION - The appliance should be situated so that its location and position do not interfere with proper ventilation. The appliance should not be situated on a bed, sofa, rug, or any surface that may obstruct cabinet openings.
8.HEAT - The appliance should be situated away from heat sources such as radiators, heat registers, stoves, or other devices (including amplifiers) that produce heat.
9.POWER SOURCES - This product should be operated only from the type of power source indicated on the marking label. If you are not sure of the type power supply in your home, consult your product dealer or local power company. For products intended to operate from battery power or other sources, refer to the operating instructions.
10.POWER CORD PROTECTION - Power supply cords should be routed so that they are not likely to be walked upon or pinched by items placed upon or against them, paying attention to cords and plugs, convenience receptacles, and the point where they exit from the appliance.
11.POLARIZED PLUG - This appliance is equipped with a polarized line plug (a plug having one blade wider than the other). This plug will fit into the power outlet only one way. This is a safety feature. If you are unable to insert the plug fully into the outlet, try reversing the plug. If the plug still fails to fit, contact your electrician to replace your obsolete outlet. Do not attempt to defeat this safety feature.
12.LIGHTNING - For added protection for this product during a lightning storm, or when it is left unattended and unused for long periods of time, unplug it from the wall outlet and disconnect the antenna or cable system. This will prevent damage to the product due to lightning and power line surges.
13.OVERLOADING - Do not overload wall outlets, extension cords, or integral convenience receptacles, as this can result in a risk of fire or electricshock.
14.CLEANING - Unplug this product from the wall outlet before cleaning. Do not use liquid cleaners or aerosol cleaners. Use a damp cloth for cleaning.
15.NON-USE PERIODS - This amplifier should be unplugged from the outlet when the appliance is left unused for a long period of time.
16.OBJECT AND LIQUID ENTRY - Never push objects of any kind into this product through openings, as they may touch dangerous voltage points or short-out parts that could result in a fire or electric shock. Never spill liquid of any kind on this product.
17.DAMAGE REQUIRING SERVICE - The appliance should be serviced by qualified personnel when:
a.The power supply cord or plug has been damaged; or
b.Objects have fallen on or liquid has been spilled into the appliance; or
c.The appliance has been exposed to rain; or
d.The appliance does not appear to operate normally or exhibits a marked change in performance; or
e.The appliance has been dropped or the enclosure is damaged.
18.SERVICING - Do not attempt to service this product yourself, as opening or removing covers may expose you to dangerous voltage or other hazards. Refer all servicing to qualified service personnel. For service warranty information call the NHT Hotline number: 1-800-NHT-9993.
19.REPLACEMENT PARTS - When replacement parts are required, be sure the service technician has used replacement parts specified by the manufacturer or that have the same characteristics as the original part. Unauthorized substitution may result in fire, electric shock, or other hazards.
20.SAFETY CHECK - Upon completion of any service or repairs to this product, ask the service technician to perform safety checks to determine that the product is in proper operating condition.
CAUTION
TO PREVENT ELECTRIC SHOCK, DO NOT USE THIS (POLARIZED) PLUG WITH AN EXTENSION CORD, RECEPTACLE OR OTHER OUTLET UNLESS THE BLADES CAN BE FULLY INSERTED TO PREVENT BLADE EXPOSURE.
Table of Contents
I. Specifications |
2 |
Placement |
2 |
Front and Back Panel Diagrams |
3 |
General Connections |
4 |
Low-Pass Filter |
4 |
High-Pass Filter |
4 |
Subwoofer Phase |
4 |
Subwoofer Volume Control |
5 |
II. The SA-2 and SW2Si: The SW2Pi Powered Subwoofer System |
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Connection Methods |
5 |
Fine Tuning the Subwoofer |
10 |
III. Multiple Subwoofer Configurations: Using two SW2Si subwoofers |
11 |
Connection Method |
11 |
IV. The SA-2 and Biamplification |
11 |
Connection Methods |
12 |
Recommended Biamplification Settings |
15 |
Bass Tuning Methods |
15 |
V. Operation |
15 |
Maintenance |
15 |
Changing the Line Voltage Setting |
15 |
Changing the Fuse |
15 |
Troubleshooting |
16 |
Glossary of Terms |
16 |
VI. Warranty Information |
17 |
Thank you for your purchase of the NHT SA-2 monaural subwoofer amplifier. Please take a few moments to read through this Owner’s Manual prior to installing your new amplifier and/or subwoofer system. The information provided can help you to obtain maximum performance from your audio system. For your convenience, a glossary on page 16 explains some technical terms. If you have questions or require assistance at any time during the installation or operation of your new amplifier/powered subwoofer system, please call your local NHT dealer or our Toll-Free Customer
Service Hotline at:
1-800-NHT 9993
Please retain the SA-2 packaging to protect the amplifier in the event that you move or transport it.
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SA-2 Amplifier Specifications
·System Type: Monaural Class G subwoofer amplifier
·Power Output: 120 watts RMS into 8 ohms, 165 watts into 4 ohms
·Frequency Response: 25Hz - 150Hz +/-3dB
·Distortion: Less than 0.03% at full power
·Crossover: Low-pass continuously variable between 35-150Hz, 18dB/octave
Selectable high-pass at 50, 75, and 110Hz, 12dB/octave (line-level)
Fixed high-pass at 100Hz (8 ohms), 6dB/octave (high-level)
· Input Connectors: Gold plated RCA jacks for line level input Gold plated barrier strip for speaker level input
· Output Connectors: Gold plated RCA jacks for line level output Gold plated barrier strip for speaker level output
Gold plated 5-way binding posts for subwoofer output
·Phase Control: 2 position selectable at 0 and 180 degrees
·Standby Mode: (defeatable) Automatically shuts off when no signal is present for 10 minutes
·Weight: 15 lbs.
·Dimensions: 3.75"H x 16"W x 10.75"D
·Finish: Black anodized front panel, black painted chassis
Design
NHT products are designed to deliver refined, musical sound from attractive and affordable packages. Our efforts are guided by the study of human hearing and are optimized for real-world use. Every NHT product undergoes rigorous testing and quality control at the factory to ensure you years of listening pleasure.
The NHT SA-2 Subwoofer Amplifier is a powerful and versatile monaural low frequency amplifier. The SA-2 and SW2Si passive subwoofer together comprise the SW2Pi Powered Subwoofer System. Additionally, the SA-2 is designed to power the subwoofer sections of NHT tower speakers when connected in biamplified configurations.
The SA-2 is optimized for powerful low frequency reproduction, with a host of convenience features and sufficient high output capability to drive up to two subwoofers. Its discrete Class G design enables cooler operating temperatures, employing a massive power transformer and dual-rail power supplies for high output and low distortion. Only high-precision, low-noise componentry is used in the crossover circuits, for seamless blending with any loudspeaker.
Placement
The SA-2 amplifier’s stand-alone design allows it to be placed either with other electronic components in the system or on top of the SW2Si subwoofer enclosure.
Note: To prevent the SA-2 amplifier from overheating, always be sure to provide adequate space for proper ventilation.
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Front and Back Panel Diagram
(A)Power Switch - Turns the unit on and off
(B)Power / Status Light - Tri-color LED: Green (On), Orange (Standby), Red (Protect)
(C)Volume Control - Adjusts the loudness of the subwoofer independently of the main speakers
(D)Subwoofer Output Terminal - 5-way binding posts for connection to the subwoofer
(E)High Level Output Barrier Strips - Speaker level connection to satellite speakers
(F)High Level Input Barrier Strips - Speaker level connection from amplifier or A/V receiver
(G)Line In - Low level RCA input jacks
(H)Low-Pass Filter (Subwoofer Fc) - Continuously variable low-pass crossover control
(I)High-Pass Filter (Satellite Fc) - 3-way selectable high-pass crossover for satellite line out
(J)Line Out - Low level RCA output jacks to receiver / main amplifier
(K)Subwoofer Phase Selector - 2-position selectable phase control
(L)Standby Mode Switch - Selects standby mode on or off. Status LED shows orange in standby mode
(M)Input Voltage Selector - 115VAC or 230VAC line voltage selector switch (note: under a removable cover)
(N)AC Power Connection and Fuse Holder - For universal line input connection
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General Connections
Caution: Prior to connecting the SA-2 to your system, it is important that all AC power connections to associated components (receivers, amplifiers, pre-amplifiers, processors, etc.) are either unplugged or turned off. Do not plug in or connect the SA-2 to AC power until all connections have been made.
The SA-2 subwoofer amplifier is designed for use with passive subwoofers only. As it is not a full-range amplifier, it will not function satisfactorily if used to power full-range loudspeakers. Four different subwoofer connection methods are covered in this manual.
Proper wiring of the subwoofer is essential to good sound. At a minimum, 14 AWG cable is recommended for runs of 15 feet or less between the SA-2 and the subwoofer, with heavier special purpose cable used for longer runs. For specialty cable considerations, consult your local authorized NHT retailer. If you are using a single SA-2 to drive two SW2Si subwoofers in parallel, it is preferable to use similar lengths of speaker cable for connections to each subwoofer.
Prepare your speaker cable by removing 1/4” to 3/8” of insulation from the ends and twisting the exposed wire strands tightly. The fiveway binding posts on the subwoofer and amplifier will accept raw wire, banana plugs or spade plugs. Tighten the binding posts by hand, as pliers can strip or break them.
Be sure to wire the subwoofer “in-phase.” That is, the positive (red) terminal on the amplifier output must be connected to the corresponding positive (red) terminal on the subwoofer. Likewise with the negative (black) terminals. All speaker cables have some sort of marking along one or both conductors to help you make the correct connections.
To minimize noise pickup, segregate cables by function. Do not run low level signal cables parallel to power cables, speaker cables, or digital cables. Also, do not run speaker cables or digital cables parallel to power cords or parallel to each other. If different types of cables are placed near each other at some place in your system, separate them by the maximum practical distance and cross them at right angles where they meet.
Low-Pass Filter (Subwoofer Fc)
The SA-2 features a continuously variable LOW-PASS FILTER which is used to determine the range of frequencies that the subwoofer will reproduce. For example, a low-pass setting of 100Hz means that the subwoofer reproduces only frequencies below 100Hz. The Low-Pass Filter is variable between 35Hz (low bass) to 150Hz (upper bass), to accommodate a variety of speaker configurations.
If you are using Connection Method #1 or #4, your main speakers are reproducing the entire frequency range (including bass) and it is advantageous for the subwoofer to reproduce only those frequencies below the rated response of the main speakers. For example, if your main speakers have a rated low frequency response of 60Hz, begin with the Low-Pass Filter set at 60Hz. See the “Fine Tuning” section for further adjustment guidelines.
If you are using Connection Method #2, your main speakers are reproducing only the frequency range selected by the SA-2’s HighPass Filter (see following section). As a starting point, set the Low-Pass Filter at about the same frequency you have set the High-Pass Filter. For example, if the High-Pass Filter sends only signals above 75Hz to your main speakers, begin with the Low-Pass Filter set at 75Hz. See the “Fine Tuning” section for further adjustment guidelines.
If you are using Connection Method #3, your main speakers are reproducing only frequencies above 100Hz, due to the fixed 100Hz high-pass filter at the speaker-level output barrier strip. As a starting point, set the Low-Pass Filter at 100Hz. See the “Fine Tuning” section for further adjustment guidelines.
High-Pass Filter (Satellite Fc): Connection Method #2 Only
The SA-2 features a 3-position selectable HIGH-PASS FILTER which is used to determine the range of frequencies that the L & R speakers (“satellites”) will reproduce. For example, a high-pass setting of 50Hz means that the L & R speakers receive a signal containing only frequencies above 50Hz. The benefit of high-pass filtering is improved dynamic range and lower distortion in the main speakers, as they are spared the task of low frequency reproduction. There are three available high-pass settings: 50Hz, 75Hz and 110Hz.
The High-Pass Filter should initially be set to a frequency above the rated low frequency limit of the L & R speakers. For example, if your speakers have a rated low frequency response of 40Hz, use the 50Hz high-pass setting. If your speakers have a rated low frequency response of 90Hz, use the 110Hz high-pass setting.
To select the appropriate high-pass setting for your L & R speakers, check the owner’s manual for their rated low frequency response. If you are unable to obtain this information, here are some common high-pass settings:
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Small speaker |
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Large speaker |
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Subwoofer Phase |
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Medium speaker |
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100Hz to 150Hz |
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80Hz to 100Hz |
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65Hz to 80Hz |
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The ability to adjust subwoofer phase is a great advantage for achieving smooth bass response in your system. The propagation of low frequency sound waves from the subwoofer and the speakers combined can sometimes cause peaks and dips in the frequency response at the listening position. In this case, adjusting the subwoofer phase may improve the blending and overall performance of the system.
The SA-2 features a 2-position SUBWOOFER PHASE selector which inverts the phase of the subwoofer between the 0° position (normal phase) and the 180° position (reverse phase). The optimal phase setting will differ according to room conditions and placement, and the main speakers used. Experiment with phase settings by listening to a familiar CD from the listening seat, alternating phase set-
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