ATC ELECTRONICS MANUAL COVERS
Contents
1. BEFORE USE 2 3 G o rae put impedance 6 o 2V 8 2dBu s Acoustic Transducer Co is a trading name and SLS is O the registered Trade Mark of Loudspeaker Technology Ltd J Fig 8 SCM20ASL Pro Rear Panel Figure 8 illustrates the connection and control panels for the SCM20ASL Pro amplifier Each feature is described below 6 2 Mains Inlet The supplied mains power lead appropriate to the local territory should be connected here Ensure that the mains voltage specified on the panel corresponds with the local supply voltage SCM20ASL 20PSL Pro 6 3 Power Switch Switches on the monitor When powered up the front panel power limit LED will illuminate green 6 4 Fuseholder Should a monitor fail to switch on when the power switch is operated the fuse should be inspected Lift out the fuseholder cover using a small flat blade screwdriver remove the fuse and inspect for damage If required a replacement fuse should be fitted Ratings are printed on the amp rear panel It should be stressed however that fuses most often fail only because of a serious electrical fault If this is the case then simply replacing the fuse will only result in another fuse failure The monitor should be returned to ATC or an authorised service technician if a second fuse fails 6 5 Input Socket The audio signal cable should be connected here Balanced or unbalanced cables may be used see Section 3 6 6 Bass Shelf This adjustment2. designed from the outset to offer the best of both Its an easy concept to describe but surprisingly difficult to engineer The difficulty inherent in designing such loudspeakers is one of scale Hi fi levels of accuracy and detail call for lightweight moving parts and delicate engineering Professional monitor levels of performance however demand far more robust components engineered to survive the rigours of high level use for extended periods The only way to combine the two is through precision engineering of a class and scale more often associated with aerospace or motorsport But the results are worth the effort and the cost ATC loudspeakers with their unique in house designed drivers combine the best of hi fi and professional to devastating effect ATC has become synonymous with active systems Choosing to offer active loudspeakers where the passive crossover network is replaced by active filters and Safety Warnings multiple power amplifiers is simply a result of the uncompromising attitude to i loudspeaker design While passive systems still have their place and ATC engineering Ion skills can still bring remarkable results from them active is a fundamentally better Section 1 Description solution to the problems posed by accurate high level music reproduction The ATC Section 2 Unpacking and Handling Section 3 Monitor Placement Section 4 Listening instinct is always for the better solution Not cheaper not quicker but bett
3. reduced by making ONE of the following modifications to the signal cable e Ifthe driving pre amp or desk is double insulated ie has no mains earth disconnect the signal cable screen at the RCA phono plug end or e Disconnect the signal cable screen at the XLR end This option will make the source the reference signal earth Fig 4 Input connection pins Pin 2 Signal hot Pin 1 Screen Pin 3 Signal return Fig 5 Balanced cable Fig 6 Unbalanced cable 3 Pin Male XLR 3 Pin Female XLR 3 Pin Male XLR Phono RCA Connector Two Core Screened Cable Connector Connector Two Core Screened Cable Connector G A Hot G _ Return o qa J AL seen o To Monitor Input To Source Output To Monitor Input To Source Output SCM20ASL SCM20PSL Pro 6 Operation SCM20ASLPro power limit Fig 7 SCM20ASL Pro Front Baffle 6 1 Power On Limit LED Situated on the lower front baffle of the SCM20ASL Pro is the Power On Limit indicator LED When the monitor is powered On the LED will illuminate green This feature is shown in Fig 7 above When the monitor is driven hard and the amplifier FET limiter begins to act the LED will turn red The brighter and longer the duration the LED red flash the more severe the limit event The FET limiter is designed to stop the amplifier hard clipping It is not a fail safe way to protect the loudspeaker drive
4. resonance free If the loudspeakers have to be positioned so the acoustic axis is above ear level they can be tilted downwards For loudspeaker positioning for 5 1 or 7 1 surround please see Fig 3 on the next page All rooms vary and it is a good idea to experiment with both listening and speaker position until a good compromise is reached For professional installations the reguirements are often very specific Please consult an experienced professional acoustician if necessary If the monitors are to be placed in any kind of cabinet or enclosure adeguate clearance around the amplifier and a means of cool air entering and hot air exiting the cabinet must be provided Alternatively the amplifiers should be removed and installed remotely Fig 2 Acoustic Axis I acoustic axis 310mm 4 Listening The ear and brain tend to interpret distorted sound as loudness and thus underestimate the actual level of undistorted sound The SCM20SL Pro both active and passive like all ATC monitors demonstrate very much lower levels of distortion than conventional systems of a similar size It is therefore advisable to begin listening at an artificially low level and carefully increase the volume It is also possible for the SCM20SL Pro to produce sufficient sound pressure levels for your ears themselves to become a source of distortion and make the sound appear harsh Any audible d
5. AT C SCM20ASL Pro SC M20PSL User Operating Manual P r o Safety Warnings 10 dat 12 13 14 15 Read instructions all the safety and operating instructions should be read before the appliance is operated Retain these 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 operating and other instructions should be followed Water and moisture the appliance should not be exposed to dripping or splashing and no objects such as vases should be placed on the appliance Ventilation a minimum Of 80mm is required at the rear of the appliance to ensure sufficient ventilation The ventilation should not be impeded by covering the appliance with items such as table cloths curtains etc Further the appliance should not be built into an installation such as a bookcase or cabinet that may impede the flow or air around the appliance Heat the appliance should be situated away from heat sources such as radiators stoves or other appliances that produce heat Power sources The appliance is of Class1 construction and shall be connected to a MAINS socket outlet with a protective earthing connection Power cord protection power supply cords should be routed so that they are not likely to be walked on or pinched by i
6. The upper horizontal pair of terminals are connected to the tweeter The lower horizontal pair are connected to the bass driver Terminals can accommodate either stripped bare cable ends 4mm banana plugs or spade terminals Do not use crimps on the bare wire ends as the difficulty in compressing them can cause poor link bar connection Always use a good quality speaker cable with 2 5mm minimum cross sectional area per conductor 79 strand For cable runs longer than 5m use a significantly heavier gauge cable Consult your dealer or consultant for specific cable recommendations Ensure that the positive and negative terminals on each connection panel are connected to the corresponding positive and negative terminals on the amplifier A lack of bass output and very wide unstable stereo imagine is most likely caused by the left and right loudspeakers being connected out of phase If the system displays these characteristics please check the polarity of the wiring Fig 8 SCM20PSL Pro Passive Input Panel S Serial No 140001 K 1Psodsp 40 vaanzoejnuews 03 umay acoustic Designed amp manufactured by Acoustic Transducer Company Gypsy Lane Aston Down Stroud Gloucestershire GL6 SHR England e 2 Acoustic Transducer Cois a trading name and jd is the registered trademark of Loudspeaker Tecnology Ltd 8 Amplification The choice of partner
7. ed Active units feature a built in two way amplifier with frequency gain and phase correction which has been individually optimised at the ATC manufacturing facility Adjustment of input sensitivity and bass boost is available to the user via controls on the amp rear panel 2 Unpacking and Handling Both the SCM20PSL Pro and SCM20ASL Pro are large heavy items and should be handled with care Always employ a second person to assist in moving them Unpacking is best carried out on the floor or a large low table with adeguate open space around the carton preferably close to their final position e Open the carton and remove all loose items leaving the packing foam in place e Up endthe carton so the open end is facing down e _Liftthe carton off the contents speaker amp foam end caps e _Liftthe upper foam end cap off e Flip the speaker over so it is resting on its base and lift the remaining foam end cap off e Remove the tape sealing the plastic bag open the bag and remove the baffle protector e Remove the speaker from the bag and position in the listening control room Fig 1 Stereo Loudspeaker Positioning A beenen distancez 47 distance x distance y distance z SCM20ASL SCM20PSL Pro 3 Monitor Placement The subjective performance of any monitor loudspeaker will be influenced by the acoustic character of the room in which it is used and its position within the room Most often monitors are insta
8. er It was the development of active loudspeakers that first brought ATC into SCM20ASL Pro Active Monitors electronics design and engineering Active speakers demand multiple power Section 5 Signal Cable Options amplifiers so ATC from the mid 1980s became not just a loudspeaker manufacturing Section 6 Operation company but an electronics manufacturer too The further step from electronics for active speakers to a range of stand alone amplifier products was natural and now Section 6 Operation means that ATC engineering is available from the recording desk or CD player SCM20PSL Pro Passive Monitors output to the ears Section 7 Connection Section 8 Amplification From modest beginnings ATC has grown to become one of the very few Section 9 Specifications manufacturers successful across both domestic and professional audio By selecting ATC you join a group of music lovers professional audio engineers studios and Section 10 Care amp Maintenance Section 11 Warranty amp Contact musicians across the world that understand and value the engineering that goes into an ATC product and the sound that comes out 1 Description The SCM20 Pro series consits of two models of loudspeaker one passive one active Passive units are denoted by a PSL suffix and active units by an ASL suffix Passive monitors are equipped with a bi wire connection panel to enable separate amplification of mid bass and high frequency drivers if requir
9. h technology material finishes are used in this product The surfaces are durable and with a little care can be kept as good as new even under conditions of heavy use Normally a dry duster will be all that is required to keep the finishes clean Heavy soiling can be cleaned using a cloth slightly moistened with a non abrasive household cleaner There are no components within the speaker that can be considered expendable or that would benefit from regular maintenance There is no requirement for any kind of routine service work and there is no schedule for preventative maintenance There are no user replaceable parts within the speaker and in the unfortunate event of any malfunction repair should be referred to either the supplying dealer or consultant the relevant importer or ATC ATC has every confidence in the quality of each product that it manufactures 11 Warranty and Contact All ATC products are guaranteed against any defect in materials or workmanship for a period of two years from the date of purchase Within this period we will supply replacement parts free of charge provided that the failure was not caused by misuse accident or negligence Purchasers who complete and return the Warranty Card will have their warranty period extended up to a period of six years from the date of purchase This guarantee does not limit statutory rights ATC can be contacted at Loudspeaker Technology Ltd Gypsy Lane Aston Down Stroud Glo
10. ing amplifier to power the SCM20PSL Pro monitors will have significant influence on the performance of the system Consider the following when selecting an amplifier With any passive loudspeaker there is a trade off between low frequency extension and sensitivity These monitor s extended low frequency response means the sensitivity is relatively low It is therefore advisable to select a power amplifier of relatively high power output capabilities Typically best performance comes with use of amplifiers capable of gt 150W continuous into 8 ohms Use ofan underpowered amplifier will result in the premature distortion of the system and increased risk of damage due to voice coil overheating e Valve or solid state amplifiers with high output impedances should be auditioned carefully to establish that their characteristic reduced damping factor at low frequencies is acceptable e Thanks in part to Super Linear technology and the underhung voice coil construction these monitors not only demonstrate extremely low distortion at all levels but also a greatly enhanced effective dynamic range This exceptional distortion performance combined with a very wide dispersion will ruthlessly reveal deficiencies in ancillary equipment Itis advisable therefore to audition the monitors with your proposed amplifier and ancillary system SCM20ASL 20PSL Pro 9 Specifications SCM20ASL Pro 1 o 0000 0D Acoustic Drive unit Low Freguency LF Drive
11. istortion indicates that either the system or your ears are being overloaded and that volumes should be reduced The user should also bear in mind that the monitoring level in a professional environment can change the way certain sounds are perceived and that for consistent high quality results consistent and moderate monitoring levels should be used Look after your ears You only get the one pair SCM20ASL 20PSL Pro Fig 3 5 1 and 7 1 Surround Loudspeaker Positioning centre All loudspeakers should be equidistant from the listening position distance L C R LS LR RR RS For 5 1 systems position the surround speakers between 110 and 150 degrees ITU spec is 110 If ideal positioning isn t possible position loudspeakers as close as possible to ideal Try to avoid placing subwoofers in corners very close to walls and on the midpoint between two parallel walls distance Q et TA S side hi i 5 side SCM20ASL Pro rear rear 5 Signal Cable Options Balanced cable configuration is the preferred option however unbalanced connection is possible Figures 5 amp 6 illustrate the signal cable connections required for each option Balanced XLR XLR connection offers lower noise and better immunity to hum pick up Unbalanced XLR RCA Phono or two pole jack connection carries risk of hum caused by multiple signal earths Hum problems resulting from unbalanced connection may be
12. lled in rooms which are comfortable to sit and talk in A mixture of carpets curtains and soft furnishings will help ensure that the middle and high freguencies are reasonable well controlled There may however be low freguency problems either too much or too little bass To minimise low freguency problems e Try to position speakers away from walls e Try to position speakers away from corners Try not to position speakers exactly 1 4 1 3 1 2 2 3 3 4 between parallel walls In professional installations try to avoid placing the loudspeakers on the console desk meter bridge Typically this compromises the freguency balance of the loudspeaker especially in the lower mid range Mounting the speakers on stands behind the console desk usually gives better results If the balance is bass light the monitors can be moved towards the back walls If the balance is bass heavy try moving the monitors away from walls corners The SCM20ASL Pro features a bass boost cut control This should be used for fine tuning rather than to compensate for poor positioning For stereo listening the loudspeakers should be positioned so they form an equilateral triangle with the listening position see Fig 1 Loudspeaker stand height should be chosen so the acoustic axis is at ear level see Fig 2 For most seating positions in professional scenarios a suitable stand would be 900 1000mm or 35 5 39 4 tall Suitable stands should be heavy rigid and
13. o result in excessive amp heating and repeated thermal trips Condition 1 is likely to cause premature drive unit failure and accelerated amplifier component ageing Conditions 2 amp 3 are likely to cause accelerated amplifier component ageing If the amplifier will not re start after a cooling period it is highly likely there is a fault leading to a DC voltage in excess of 4 0V on the amplifier outputs This will require repair by ATC or a approved service engineer Please contact your local ATC dealer or ATC direct if this is the case Note Due to the nature of the electronics in ATC active loudspeakers it is quite normal for a sound to be heard from the speaker when the power is applied or disconnected The noise heard and the movement observed in the bass drive unit will not damage the speaker and is quite normal Although ATC uses the highest grade components a different noise may be heard from each speaker due to slight tolerance variations in the amplifier components SCM20ASL SCM20PSL Pro SCM20PSL Pro 7 Connection The SCM20PSL Pro monitors are equipped with a bi wire connection panel to enable separate amplification of the bass mid driver and tweeter The connection panel is shown in Fig 8 below If not bi wiring connect your speaker cable to either the upper or lower horizontal pair of terminals Remove the linking bars between vertical pairs of terminals should you wish to take advantage of the bi wire facility
14. om around the unit to ensure the switch is readily operable when the unit is in use SCM20ASL SCM20PSL Pro SCM20ASL 20PSL Pro Introduction Welcome In selecting ATC you have chosen an example of the finest audio engineering available ATC was founded on a principle of engineering excellence and that principle still defines our products today Given the right opportunities ATC products will deliver exceptional audio performance but the opportunities will only arise from careful and thoughtful installation and use Please read the following manual fully It will help you understand the product and to realise its full potential We are happy to answer questions and offer advice on any issues that arise through installation or use of ATC products Contact details can be found at the back of this manual ATC was founded in London in 1974 by Australian emigre Bill Woodman who still heads the company today An enthusiastic pianist and engineer he was naturally drawn to loudspeaker design and after a period working at Goodmans where many of the names that went on to found British loudspeaker companies began their careers he struck out on his own The premise on which ATC began is a simple one and one that in many respects is still true today hi fi loudspeakers tend to be detailed and accurate but of limited dynamic range while professional monitor speakers tend to express the opposite character ATC products were
15. order 12dB oct critically damped with phase compensation 250kHz 112dBA Max gain ref 40V out IEC A 109dBA Max gain ref 20V out IEC A 80Hz 2dB to 3dB in 1dB steps via rear panel rotary switch Active FET momentary gain reduction inc front panel mounted limit LED Amplifier thermal trip circuit 115 230V 50 60Hz internally selectable by technician 100V 50 60Hz factory set 381Watts 483VA K amp M 24120 Wall Mount cabinet requires modification to accept top hat mount 28kg 61 6lbs per cabinet 6 5 150mm Super Linear with 75mm 3 voice coil SB75 150SL 8 Ohm 1 25mm dual suspension Soft Dome SH25 76S 6 Ohm 80Hz 20kHz 2dB 55Hz 25kHz 6dB freestanding 80 coherent 10 coherent 108dB per pair 1m 2 1kHz 75 to 300 Watts 8 Ohm 2 x Pairs Binding Posts 4mm Plugs Bi Wireable K amp M 24120 Wall Mount cabinet requires modification to accept top hat mount 450x250x294mm 18kg 39 7lbs per cabinet Specifications comply with the following standards Australian Standard Specification No 1127 Sound System Loudspeakers Part 5 IEFE Specification Standard No 219 1975 E amp O E The policy of ATC is that of continuous design and development ATC reserves the right to alter products and specifications without prior notice Acoustic Transducer Co is a trading name and ATC is the registered trade mark of Loudspeaker Technology Ltd 10 Care and Maintenance Hig
16. provides 2dB to 3dB of cut and boost in 1dB steps in the form of a shelving filter This subtracts adds more warmth and energy in the low frequency region When used to boost it is at the expense of e Accurate transient reproduction e Reduced Headroom e Increased distortion Note This adjustment should be used for fine tuning Please try to achieve the best possible in room bass response by first adjusting loudspeaker and listening position and room acoustic treatment if possible 6 7 Input Sensitivity This user adjustment is made up of two controls a Selector Switch This switch toggles between 1V 2 2dBu and 2V 8 2dBu input sensitivity for full amp output Choose the setting that best suits the source pre amp mixer or monitor controller Input sensitivity can be further fine tuned using the Input Sensitivity Trim Note For source driving equipment with potentiometer based analogue level control choose an input sensitivity that results in the desired average sound pressure level with the source level control at approximately 50 For source driving equipment with a digital level control choose an input sensitivity that results in the desired average sound pressure level with the level control at approximately 80 b Trim Pot This control provides fine adjustment of input sensitivity Fully clockwise is the factory reference position of OdB In this position the trim has no affect on the input sensitivity which is con
17. tems placed upon or against them paying particular attention to cords at plugs convenience receptacles and the point where they exit the appliance Cleaning the appliance should be cleaned only as recommended by the manufacturer Unattended periods the power cord of the appliance should be unplugged from the outlet when left unused for a long period of time Object entry care should be taken so that objects do not fall into the appliance Damage requiring service the appliance should be serviced by qualified service personnel when i the power supply cord or the plug has been damaged ii objects have fallen or liquid has been spilled into the appliance iii the appliance has been exposed to rain or other serious liquid exposure iv the appliance does not appear to operate normally or exhibits a marked change in performance v the appliance has been dropped or the cabinet damaged Servicing the user should not attempt to service the appliance beyond those measures described in the operating instructions All other servicing should be referred to qualified service personnel Grounding or polarisation precautions should be taken so that grounding or polarisation means for the appliance are not defeated The Mains disconnection switch is located on the rear panel Pressing the switch downwards will turn the unit on The unit can be turned off by upward pressure on the switch Please allow enough ro
18. trolled by the switch described above Turning the control anti clockwise will result in up to 6dB of adjustment The combination of the two controls gives a total input sensitivity range of 1V 2 2dBu to 4V 14 2dBu for full amplifier output of 200W 6 8 Fault LED This LED will illuminate if one of two fault conditions occurs within the amplifier 1 Thermal Overload amplifier plate temperature gt 60 C 2 Output DC offset amplifier output DC offset gt 100mV If thermal overload is suspected an amp plate of 60 C is uncomfortable to touch turn off the amp and leave it to cool for 15 minutes If the amplifier re starts without the fault LED the temperature will have fallen and the fault cleared However thermal overload is not typical The heat sinking on the amplifier has been specified to control the amp temperature under normal working conditions If the amplifier plate has reached 60 C then it is very likely one of the following conditions applies 1 The monitor is being driven continuously at very high SPL or with signals that are continuous in nature ie sine waves REDUCE THE SOUND PRESSURE LEVEL 2 The heat sink and amp plate are covered or partially covered blocking or reducing the cooling airflow DO NOT RESTRICT COOLING 3 Ambient temperature in the control listening room or in the area in close proximity to the monitor is in excess of 33 C REDUCE AMBIENT TEMPERATURE Failure to correct any of the above is likely t
19. ucestershire GL6 8HR Telephone 01285 760561 Fax 01285 760683 Email info atc gb net Website www atcloudspeakers gb net SCM20ASL SCM20PSL Pro Loudspeaker Technology Ltd Gypsy Lane Aston Down Stroud Gloucestershire GL6 8HR United Kingdom Telephone 01285 760561 Fax 01285 760683 Email info atc gb net Web www atcloudspeakers co uk
20. unit High Freguency HF Amplitude linearity Cut off freguencies Horizontal dispersion Vertical dispersion Maximum continuous SPL Crossover freguency Electronic Audio input Input sensitivity Input sensitivity trim Total input sensitivity range Input impedance LF amp max output power HF amp max output power THD LF amp THD HF amp Crossover filters HF upper 3dB point S N N ratio LF S N N ratio HF Low freguency shelf cut boost Overload protection Mains power reguirements Max power consumption Accessories Weight SCM20PSL Pro Drive unit Low Freguency LF Drive unit High Freguency HF Amplitude linearity Cut off freguencies Horizontal dispersion Vertical dispersion Maximum continuous SPL Crossover freguency Recommended Power Amplifier Nominal Impedance Connectors Accessories Cabinet Dimensions HxWxD Weight 6 5 150mm Super Linear with 75mm 3 voice coil SB75 150SL 8 Ohm 1 25mm dual suspension Soft Dome SH25 76S 6 Ohm 80Hz 20kHz 2dB 55Hz 25kHz 6dB freestanding 80 coherent 10 coherent 108dB per pair 1m 2 1kHz Rear panel mounted female XLR pin 2 ve 1V 2V RMS or 2 2 8 2dBu via switch ref bass full output OdB to 6dB via rear panel pot 1V 2 2dBu to 4V 14 2dBu 10kQ per leg 200W continuous 1 THD 50W continuous 1 THD 0 0006 104 4dB 100Hz 1dB below rated power 0 0022 93 2dB 10kHz 1dB below rated power 2nd
21. units When not active the FET limiter is not in circuit ie it is a parallel part of the circuitry and it will not reduce sound quality When the limiter is active it reduces gain with a soft clipping characteristic Nonetheless when the limiter is active it does have an affect on the sound quality and the amplifier distortion will increase At these levels the loudspeaker drive units will also display much greater non linearities and the sound pressure level should be reduced if critical judgements made on the monitors are to be trusted It should also be noted that the sound pressure levels produced when the amplifier is at full output and the limiter is active are capable of causing hearing damage especially if the listener is exposed to these levels for sustained periods of time Critical judgements made on the monitors at full output are also likely to be inaccurate With ANY studio monitoring system use consistent and moderate listening levels if consistent and accurate judgements are reguired ee To FAULT amplifier overtemp DC offset TT 11 N fuse 230V 2 5A on CL 15V 5A A P EO RUSE serial number 00001 5 M O 7 O voltage 230V 0 balanced input MAINS INPUT 50 60Hz XV S input sensitivity bass shelf for 200W out POWER CONSUMPTION cut boost dB trim dB 335VA MAX 0 3 IV l it CHECK VOLTAGE ll Ut A i 2 2dBu o o zy
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