NHT A-20 User's Manual
Contents
1. 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 SAFETY INSTRUCTIONS PLEASE READ FIRST CAUTION To reduce the risk of electric shock do not remove CAUTION the cover or back No user serviceable parts are inside refer A RISK OF ELECTRIC SHOCK A servicing to qualified personnel DION 0 Me 1 WARNING SHOCK HAZARD DO NOT OPEN WARNING To reduce the risk of fire or electric shock do AVIS RISQUE DU CHOC ELECTRONIQUE NE PAS OUVRIR not expose this appliance torain or moisture This symbol wherever it appears alerts you to the presence This symbol wherever it appears alerts you to of uninsulated dangerous voltage inside the enclosure that important operating and maintenance instructions in the may be sufficient to constitute a risk of electric shock accompanying literature Read the manual DETAILED SAFETY INSTRUCTIONS All the safety and operation instructions should be read before the appliance is operated Retain Instructions The safety and operating instructions should be retained for future reference Heed Warnings All warnings on the appliance and in the operating instructions should be adhered to Follow Instructions All operation and user instructions should be followed Water and Moisture The appliance should not be used near water2. near mid 1 5M mid 2M mid far 2 5M far 3M Power On off Display Mode Display Switchable SPL Output 68dB 120dB Line Voltage 90 I35VAC Heat Sink Temp 20 99 Co LED s Power Overload Other Headphone Output insertion interrupts main output NHTPRO 6400 Goodyear Rd Benicia CA 94510 ph 707 748 5940 fx 707 747 1252 www nhtpro com
3. Hot Line at 800 NHT 9993 648 9993 You can also visit our web site at www nhtpro com for more in depth technical information Thanks 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 I ea Control Amplifier 2 ea 20 Monitor Output Cables I ea 6 IEC Power Cord 4 ea 10 32 Rack Mounting Screws I ea Warranty Registration Card 3 ea Plastic Insulating Washers Screws Insulating The A 20 Control Amplifier may be used on a shelf or mounted in a standard 19 equipment J Washer rack using the screws and washers supplied For rack mounting remove and retain the four pss fa a feet from the bottom of the amp chassis using a 2 Philips screwdriver Two vertical rack cr spaces are required but we recommend you leave at least one additional open space role dk Roi above and below the A 20 for improved cooling as
4. 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 efforttocombat longterm ear fatigue can help youavoid 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 IIO V may limit your maximum output levels and could indicate thatthe AC circuitis overloaded Continuous readings above 125 V indicatean 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 willautomatically 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 1 IdB 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 d
5. 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 beon axis with your ears or slightly above Also remember that nearby reflective surfaces can alter impulse response blur imaging and change tonality Dix 5 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 MONITORSYSTEM 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 spraythe speaker or amplifier directly Avoid silicone and oil based cleaners o
6. 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 Coe 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 alotiation Ree page 7 Fig I Rack Mounting Detail Monitor Qutput Cables ae i utpu To AC Line Bees alls Fig 2 Typical System Configuration SYSTEM CONNECTIONS 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 A CAUTION MAKE ALL CONNECTIONS WITH THE AC POWER OFF CONTROL AMPLIFIER INPUT SECTION The A 20 Control Amplifier accepts both balanced and unbalanced inputs on either XLR or 1 4 TRSconnectors 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 ee TRAN Lee SOURCE A 20 I
7. NPUT j 1 GND 7 SIGNAL gt GND 3 3 Su Shield XLR TRS Fig 3a Balanced Wiring Diagram Fig 3b Unbalanced Wiring Diagram SPEAKERCABLE 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 measurement data on a variety of cable types at www vergenceaudio com under the support section Be sure they are wired as 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 onthe control amplifier and monitors untilthe connector locks IHAT NO CONDUCTION IS WIRED TO THE XLR CASING FAILU
8. RE TO WARNING IF USING CABLES OTHER THAN THOSE SUPPLIED WITH THIS SYSTEM BE SURE A MA Y CONSITITT UTE RISK OF ELECIRIO SHOCK A 20 Monitor CAUTION A 20 Monitor Right Ace A RIGHT LEFT NHTPro Left DO NOT OPEN AZ AZ MODEL A 20 CONTROL AMPLIFIER Ege h WARNING SHOCK HAZARD DO NOT OPEN O O SERIAL NO A20 A 10001 h Ce AVIS RISQUE DU CHOC ELECTRONIQUE Jj y 7 ae NE PAS OUVRIR l CAUTION NHTPro FOR CONTINUED PROTECTION AGAINST INPUT BENICIA CALIFORNIA U S A RISK OF FIRE REPLACE ONLY WITH SAME MADE IN TAIWAN G1 TYPE 250V FUSE C C 2 PIN SIONAL INPUT VOLTAGE FUSE TYPE z eA 5 n CAUTION T9A 250V FOR 110 120V 2 CONNECTING OUTPUTS TO ANY T5A 250V FOR 220 240V UL LISTED 3 a PRODUCT OTHER THAN A 20 XLR TRS 20 or AUDIO EQUIP C 20 MONITORS MAY RESULT IN A 50 60 Hz 950W SEVERE EQUIPMENT DAMAGE Fig 4 A 20 Control Amplifier Rear Panel USING THEA 20 CONTROLFUNCTIONS 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 to fine tune the system to the requirements of your particular installation
9. SENSITIVITY BOUNDARY POSITION SPL VAC TMP BHT Control A 20 Amplifier 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 theright of the System Status Display selects the desired mode SPL Thisisthelongterm 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
10. e g near a bathtub washbowl kitchen sink laundry tub in a wet basement or near a swimming pool EtG Ventilation The appliance should be situated so that its location or position does not interfere with its proper ventilation For example the appliance should not be situated on a bed sofa rug or similar surface that may block the ventilation openings or placed in a built in installation such as a bookcase or cabinet that may impede the flow of air through the ventilation openings Heat The appliance should be situated away from heat sources such as radiators heat registers stoves or other appliances including other amplifiers that produce heat Power Source The appliance should only be connected to a power supply of the type described in the operating instructions or as marked on the appliance Grounding and Polarization Precautions should be taken so that the grounding or the polarization means of the appliance is not defeated Power Cord Protection Power supply cords should be routed so that they are not likely to be walked on or pinched by items placed upon or against them paying particular attention to cords and plugs convenience receptacles and the point where they exit from the appliance Cleaning The appliance should only be cleaned as recommended by the manufacturer Non use Periods The power cord of the appliance should be unplugged from the outlet when left unused for a long period of time Object and Li
11. esired 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 Space Quarter Half Space Half Space Half Whole Space Whole Space gt i i i i D dl es r gt 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 frequenc
12. quid Entry Care should be taken so that objects do not fall and liquids are not spilled into the enclosure through openings Damage Requiring Service The appliance should be serviced by qualified service personnel when The power supply cord or the plug has been damaged or Objects have AIEN or liquid has been spilled into the appliance or The appliance has been exposed to rain or The appliance does not appear to operate normally or exhibits a marked change in performance or The appliance has been dropped or the enclosure damaged Servicing The user should not attempt to service the appliance beyond what is described in the Operating Instructions All other servicing should be referred to qualified service personnel 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
13. r treatments pray P P y NEED HELP Technical Support can be reached several ways Telephone us 800 NHT 9993 648 9993 E mail us at tech nhtpro com Fax us at 707 747 1252 or write us at NHTPro 6400 Goodyear Rd Benicia CA 94510 Or visit our worldwide web site at www nhtpro com 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 I metal dome textile surround ferrofluid cooled and damped Magnetic Shielding Partial 12 18 working distance from PC monitor recommended PERFORMANCE SPECIFICATION Amplifier Power 250W continuous RMS ch 400W 100ms peak Peak Acoustic Output 117 dB SPL 100ms pink noise IM Residual hum noise lt 10 dB SPL IM System THD 90 dB SPL lt 0 4 100Hz I0kHz IM Response 2 dB 1 3 oct swept noise 48Hz 20kHz IM 45Hz 20kHz 2M 6dB LF cutoff 40Hz in room response Loudspeaker Dimensions Wet I4 hx 7 5 wx 11 9 d 19 lbs Loudspeaker Materials 0 75 MDF w high pressure laminate internal external Control Amplifier Dimensions Wet 3 5 hx 19 wx 13 375 d 37 lbs FEATURES CONTROLS Connectors Input XLR TRS Output to monitor XLR Controls Sensitivity 5 position 10dB 3dB 4dB IIdB Mute Boundary 5 position 0 0 0 5 1 0 1 5 2 0 representing walls Position 5 position near IM
14. y 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 lt gt Do IM 1 5M 2M 2 5M 3M A 20 N Far Field Monitor Mid field Near field MF 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
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