NHT M-20 Speaker User Manual
Contents
1. Pro Audio M 20 Powered Monitor Owner s Manual M 20 Control Amplifier Serial Number M 20 Monitor Serial Number Rev 6 06 Safety Instructions Please Read First CAUTION To reduce the risk of electric shock do not CAUTION remove the cover or back No user serviceable parts are T RISK OF ELECTRIC SHOCK inside refer servicing to qualified personnel DO NOT OPEN E l WARNING SHOCK HAZARD DO NOT OPEN WARNING To reduce the risk of fire or electric shock do AVIS RISQUE DU CHOC ELECTRONIQUE not expose this appliance to rain or moisture NE PAS OUVRIR This symbol wherever it appears alerts you to This symbol wherever it appears alerts you to the presence of uninsulated dangerous voltage important operating and maintenance inside the enclosure that may be sufficient to instructions in the accompanying literature constitute a risk of electric shock 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 water e g near a bathtub washbowl kitchen sink laundry t2. NHT 6400 Goodyear Rd Benicia CA94510 Or visit our web site at www nhtpro com SYSTEM SPECIFICATIONS SYSTEM MONITOR 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 ferro fluid cooled and damped Magnetic Shielding Full Loudspeaker Dimensions Wst 14 h x 8 w x 9 375 d 19 lbs Shipping weight 22lbs 10 kg Loudspeaker Materials 0 75 MDF CONTROL AMPLIFIER Amplifier Power 250W continuous rms 400W 100ms peak Peak Acoustic Output 111 dB SPL 100ms pink noise 1M Residual hum noise lt 10 dB SPL 1M System THD 90 dB SPL lt 0 4 100Hz 10kHz 1M Response 2 dB 1 3 oct swept noise 48Hz 20kHz 1M 45Hz 20kKHz 2M 6dB LF cutoff 40Hz in room response Control Amplifier Dimensions Wst 1 75 h x 19 w x 13 375 d 19 lbs Shipping weight 25 7lbs 11 7 kg 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 Switchable SPL Output 68dB 120dB Line Voltage 90 135V Heat Sink Temp 20 99 C LED s Power Overload NHT 6400 Goodyear Rd
3. WITH THE AC POWER TURNED OFF POWER CONNECTIONS FUSE The power cord receptacle contains a spare fuse located within the power connector To get at the fuse remove the power cord and use a small flat head screwdriver to access the fuse compartment When replacing the fuse with a spare use only a fuse of the same current rating Located next to the power cord receptacle is a voltage selector preset at the factory for the destination country the power cord supplied is appropriate for that voltage Confirm the voltage selector setting before powering up the system CONTROL AMPLIFIER INPUT SECTION The M 20 Control Amplifier accepts both balanced and unbalanced inputs on either XLR or 1 4 TRS connectors These connectors are connected in parallel within the M 20 to allow for convenient equipment chaining but only one input 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 Keep in mind that the M 20 can accept awiderangeof signals and has an input sensitivity control on the front panel 2 PIN SIGNAL SOURCE A 20 INPUT 1 1 GND P l l SIGNAL S GND 6 3 3 Shield J TRS XLR Fig 3a Balanced Wiring Diagram Fig 3b Unbalanced Wiring Diagram SPEAKER CONNECTIONS The M 20 includes a 20 special purpose cab
4. and provide flat response at various listening distances Setting the control in the FF far field position gives the maximum high frequency output Each step counter clockwise moving toward the near field position attenuates the 20 kHz by an additional 75 dB with the effect rolling off at3 kHz See Fig 7 for appropriate POSITION controlsettings for various listening distances Listener Distance lt 4 gt 0 1m 1 5m 2m 2 5m 3m M 20 X Far Field Monitor Mid field Near field Fig 7 Position Control Settings Diagram SPEAKER PLACEMENT The M 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 the M 20 Monitors should be set up the same distance from the listening position see fig 8 below This is important in order to insure equal arrival time of all channels to the listening position Ideally the tweeter height on the M 20 monitor as with all channels should be on axis with your ears or slightly above Also remember that nearby reflective surfaces including video monitors can alter impulse response blur imaging and change tonality giving the M 20 as much room as possib
5. hour session to sessionandroom to room Levels under 68dB 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 SPLhelps to assure consistent results VAC This is a reading of the AC power line voltage being supplied to the M 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 Centigrade Typically you should expect thisto run between 40 C and 60 C depending on listening and ambient conditions If you findthat your Control Amplifier unit tends to run hotter than 60 C it is recommended that you improve the ventilation around it The M 20 Control Amplifier contains a protection circuit that automatically shuts the amplifier down if the heat sink temperature reaches 100 C SENSITIVITY This function controls input sensitivity with settings at 10dB 3dB 4dB 11dB and M ute to provide 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
6. without source clipping Professional devices typically specify full output at 4dB most consumer audio products reach full output at 3dB most computer sound cards at 10dB Consult the owner s manual of the source device driving to the M 20 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 greatest 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 inFig 6for information on setting the control appropriately TO P Quarter Space Quarter Half Space Half Space Half Whole Space Whole Space 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 monitoring conversely reveal aspects of room ambience and are more representative of end use With increased listening distance a speaker s upper frequency power response attenuates due to room influences and air absorption The M 20 may be adjusted to compensate for this change
7. Benicia CA 94510 ph 707 747 0122 fx 707 747 1252 www nhtpro com
8. btle impact on the basic character and accuracy of the speaker We encourage you to experiment with fine tuning the system to your particular requirements KT M 20 RS SENSITIVITY BOUNDARY POSITION Fig 5 M 20 Control Amplifier Front Panel POWER INDICATORS Two LED S are located tothe immediate left of the power switch on the M 20ControlAmplifier The top green LED lights up indicating there is AC power to the amplifier and the POWER SWITCH is turned Qn 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 and the input signalorsystem gain should be reduced to avoid the risk of possible system damage SYSTEM STATUS DISPLAY Located in the center of the front panel a unique system status display informs you of the operating state of your system Three small LED s green for average SPL yellow for AC line voltage and blue for heat sink temperature respond to your setting the square MODE switch to the right of the System Status Display to the desired mode SPL This is a reading of the long term average sound pressure level calibrated at 2 meters from the M 20 monitor and derived from the amplifier output voltage Peak sound levels are ignored The readout is designed to report overall listening levels and to help realize consistent monitoring from hour to
9. eaker cabinet using controlled impedance cables that actually form part of the crossover network By designing the system as an integral package of control amp cables and monitor many of the advantages of self powered speakers can be realized without the possible attendant performance compromises of fully integrated designs A WARNING The M 20 monitor speaker must only be used with the M 20 Control Am cables and vice versa The following are included in the Control Amplifier carton 1 Control Amplifier 1 20 Monitor Output Cable 1 6 IEC Power Cord 4 10 32 Rack Mounting Screws 1 Warranty Registration Card 8 Plastic Insulating Washers Screws Insulating NS 4 Washers ren fe fld M 20 meen AA S rac ron E p fi Fig 1 Rack Mounting Detail INITIAL INSTALLATION The M 20 Control Amplifier may be used on a shelf or mounted in a standard 19 equipment rack using the screws and washers supplied One vertical rack space is required but we recommend you leave at least one additional open space above and below the M 20 Control Amplifier 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 position all M 20 monitors equidistant from the listening position For more detailed speaker placement information see page 7 SYSTEM CONNECTIONS A CAUTION MAKE ALL CONNECTIONS
10. le assures the highest quality reproduction M 20 A 9 4 x K B A C The Distance of A B C D E E AX Cy E Fig 8 Ideal 5 1 Surround Monitor Placement SYSTEM OPERATION The M 20 is capable of very high output levels especially when listening in the near field 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 that 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 Protect your ears and use common sense M 20 MONITOR SYSTEM CARE Except for the occasional flattering comment your M 20 System needs no regular maintenance Never attempt to clean the M 20 Monitor driver units except for very light feather dusting The M 20 Monitor cabinets and the M 20 Control Amplifier front panel can be cleaned using a damp soft cotton cloth first sprayed with a mild non abrasive glass cleaner and with the unit unplugged and AC power off Never spray the speaker or amplifier directly Avoid silicone and oil based cleaners or treatments NEED SOME 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
11. le to connect the Control Amplifier to the Monitor While this cable looks similar to a standard microphone cable it is constructed with lower and more consistent conductor impedance Portions of the M 20 s crossover circuitry are located in both the amplifier and speaker enclosures and the cable supplied is an important part of this electrical network This allows the speaker cable to function as a neutral and transparent component inthe system Replacing or extending the supplied cable with any other type will have a varying and unpredictable impact on the sound If your installation requires the use of alternative cables you may consult the Cable Measurement Data Chart on our website Besure they are wired as shown in Fig 3a Using the included cable to connect the M 20 Monitor to the Control Amplifier is quite simple and straightforward fit the XLR connectors into the corresponding connectors on the Control Amplifier and Monitor until the connector locks WARNING IF USING CABLES OTHER THAN THOSE SUPPLIED WITH THIS SYSTEM BE SURE THAT NO CONDUCTOR IS WIRED TO THE XLR CASING FAILURE TO DO SO A MAY CONSTITUTE A RISK OF ELECTRIC SHOCK Fig 4 Typical installation M 20 MONITOR ING OUTPUT NTHE r GE S To AC outlet Source To monitor via supplied red cable USING THE M 20 CONTROL FUNCTIONS The M 20 controls are designed for utility and repeatability under varying conditions and make only su
12. 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 plus has been damaged or Objects have fallen 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 selecting and purchasing the M 20 Your studio monitors are a critical element in the countless decisions made during recording mixing and mastering and must deliver a transparent neutral sound so you have the information you need to choose and place microphones set eq s balance mixes ie to deliver exceptional product Multiple M 20 s deliver state of the art multi channel monitoring capability If you require assistance at any time during or after the setup process call our Customer Service Hot Line at 1 800 NHT 9993 648 9993 You can also visit our web site at www nhtpro com for more in depth technical information GETTING STARTED The M 20 is unique in that it combines a dedicated control amplifier with a separate loudsp
13. ub in a wet basement or near a swimming pool etc 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 Salat 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 Liquid Entry Care should be taken so that objects do
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