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L-ACOUSTICS ARCS Manual V2.0

2/13/2003

2. POWERING ARCS

It is important that power amplifiers with sufficient power are used to power ARCS since headroom is

much less likely to damage loudspeaker components than amplifier clipping. Apart from normal

standards regarding construction, protection, cooling and damping factor that are expected of any

professional sound reinforcement amplifier, the ARCS system has been calibrated to be used with

amplifiers with the following specifications:

GAIN STRUCTURE

All amplifiers should have 32 dB gain for all sections (sub, low and high). The limiter thresholds and

output channel gains of OEM digital crossover presets have been adjusted to be used with amplifiers

having 32 dB gain.

LIMITERS

Peak limiters on all amplifier outputs with soft clipping characteristics; attack time less than 3 msec.

COOLING

Temperature speed-controlled fan recommended

POWER OUTPUT

Minimum and maximum power handling ratings for ARCS are as follows:
LF Section: 54 volts long term rms (pink noise with 6 dB crest factor)

375 Watts (rms), 1500 Watts (peak) at 8 ohms

HF Section: 29 volts long term rms (pink noise with 6 dB crest factor)

100 Watts (rms), 400 Watts (peak) at 8 ohms

In practice, L-ACOUSTICS specifies power amplifiers with power output equivalent to twice the RMS

power handling for the low section and equivalent to the peak power handling for the high section.

These requirements typically allow the same amplifier to be used for both LF and HF sections. For the

high section, since the drive level is attenuated relative to the low section by up to 10 dB at the

crossover to compensate for component efficiency differences, we can use the same amplifier since

we will never deliver full continuous power to the high section (i.e., due to the attenuation). The extra

available power translates to headroom for improved high frequency transient response.
Table 1 gives a summary of rms and peak power handling along with recommended amplifier output

power specifications for 1, 2 or 3 ARCS in parallel.

Table 1: Load and Power Ratings for ARCS

ONE ARCS

TWO ARCS

THREE ARCS

FOUR ARCS

SECTION

LOAD

RMS

PEAK REC'D LOAD

RMS

PEAK REC'D LOAD

RMS

PEAK REC'D LOAD

RMS

PEAK REC'D

LOW

375

1500

750

750

3000

1500

2.7

1125

4500

2250

1500

6000

3000

HIGH

100

400

400

200

800

800

2.7

300

1200

1200

400

1600

1600

For amplifying

2 ARCS in parallel

, the recommended amplifier specifications are:

* LOW Amplifier Output Power: 1500 W into 4 ohms

* HIGH Amplifier Output Power: 800 W into 4 ohms

For amplifying

3 ARCS in parallel

, the recommended amplifier specifications are:

* LOW Amplifier Output Power: 2250 W into 2.7 ohms

* HIGH Amplifier Output Power: 1200 W into 2.7 ohms

For amplifying

4 ARCS in parallel

, the recommended amplifier specifications are:

* LOW Amplifier Output Power: 3000 W into 2 ohms

* HIGH Amplifier Output Power: 1600 W into 2 ohms

Содержание ARCS

Страница 1: ...Version 2 February 2003 L ACOUSTICS ARCS OPERATOR MANUAL ...

Страница 2: ... manual will be sufficient for most applications however should you require further assistance your local distributor or L ACOUSTICS are available to provide additional technical support MANUAL ORGANIZATION The Introduction gives a presentation of Wavefront Sculpture Technology and the ARCS system Chapter 1 introduces the elements of the ARCS system Chapter 2 details ARCS power amplification and c...

Страница 3: ...PRESET POLICY 19 3 3 GUIDELINES REGARDING SYSTEM PROTECTION 20 3 4 ARCS PRESET LIBRARIES 21 4 SOUND DESIGN 27 4 1 APPLICATIONS 27 SINGLE ROW ARRAYS 27 DOUBLE ROW ARRAYS 28 4 2 ARRAY AIMING 28 4 3 MONITOR SIDE FILL 30 4 4 COMPLEMENTARY FILL 31 FLOWN STACKED CENTRE FILL 32 STACKED STEREO INFILL 32 OFFSTAGE FILL 32 4 5 DELAY SYSTEMS 33 4 6 USING ARCS WITH SUBWOOFERS 34 A COMBINING ARCS WITH SUBWOOFER...

Страница 4: ...FOH system with delays 33 Figure 20 L ACOUSTICS Subwoofer Continuous Unweighted SPL Comparison 34 Figure 21 Illustration of subwoofer time alignment 36 Figure 22 Rigging procedure for a 4 enclosure ARCS array 39 Figure 23 Rigging procedure for a 3 enclosure ARCS array 40 Figure 24 Rigging procedure for a double row 4 4 enclosure ARCS array 43 Figure 25 ARCBUMP rigging procedure for a 3 enclosure h...

Страница 5: ...ge has long been regarded as the most practical approach for high power sound reinforcement the condition that each array becomes the equivalent of a single sound source has often been comprised or overlooked When arrayed most conventional speakers do not couple acoustically at frequencies having a wavelength smaller than the physical size of the enclosure Typically problems occur at mid and high ...

Страница 6: ...g WST criteria at higher frequencies is a specific waveguide that is used to load a conventional compression driver This DOSC waveguide was invented by Dr Christian Heil and is patented world wide DOSC stands for Diffuseur d Onde Sonore Cylindrique in English this means Cylindrical Sound Wave Generator Essentially the DOSC waveguide permits fulfilment of the 1st and 3rd WST conditions at higher fr...

Страница 7: ...ogy and provides when arrayed in any number the equivalent of single loudspeaker behavior The net result is exceptionally even frequency response over the entire array coverage area a feature which is characteristic of Wavefront Sculpture Technology For optimizing the geometrical coverage of typical audiences the vertical coverage of ARCS is not symmetrical but provides 40 in one direction and 20 ...

Страница 8: ... rigging an ARCS array Weight is 3 8 kg 8 4 lbs One BUMP3 is required to fly 2 or 4 cabinets Two BUMP3 and one LIFTBAR are required to fly 1 3 4 6 or 8 enclosures 5 ARCSTRAP Vertical linking elements for flying double row ARCS configurations ARCSTRAP is provided in pairs for front and rear attachment 6 LIFTBAR Rigging bar for use with 2 x BUMP3 provided with 3 shackles 7 ARCBUMP Rigging accessory ...

Страница 9: ...L ACOUSTICS ARCS Manual V2 0 2 13 2003 8 Figure 3 ARCS System Block Diagram ...

Страница 10: ...L ACOUSTICS ARCS Manual V2 0 2 13 2003 9 ARCS ARCPLA ARCOUPL BUMP3 LIFTBAR ARCSCOV ARCBUMP ARCSTRAP F CABLE DO7 F LINK CABLE DO 7 Figure 4 ARCS System Parts and Accessories ...

Страница 11: ...stance for a long lasting appearance The color is maroon gray and touchup paint is available for maintenance purposes Internal steel bracing guarantees both flying security and long term reliability of the cabinets under the most demanding of touring conditions Coupling rails are bolted to internal bracing and are vertically connected to each other by internal steel bars Two recessed handles are f...

Страница 12: ...feature strategically located flaps and holes for convenient handling and testing purposes Figure 7 ARCSCOV 1 4 ARCS RIGGING COMPONENTS ARCOUPL Aluminum coupling bar designed to mechanically connect adjacent ARCS enclosures when arraying The male connecting bar slides into the two female rails on adjacent ARCS to provide a tight mechanical connection between the enclosures Two ARCOUPL are required...

Страница 13: ... gravity for the array in order to provide the desired overall tilt angle Only one BUMP3 is required for flying an even number of enclosures up to 4 whereas two BUMP3 and one LIFTBAR are required for flying an odd number or for more than 4 enclosures up to 8 For larger configurations where ARCS is flown in the normal vertical orientation there should be no more than 4 ARCS enclosures vertically or...

Страница 14: ...ng up to 3 ARCS enclosures single point hangs can be performed using the rigging points available on the central spreader bar section of ARCBUMP For flying 4 ARCS enclosures horizontally a bridled hang should be performed using the exterior points on the sides of the ARCBUMP frame Safety steels must be employed for all flown horizontal applications The safety steels are attached between all front ...

Страница 15: ...el section is used to physically link ARCOUPL bars front and rear between the top row of ARCS enclosures bottom ARCOUPL bars and bottom row ARCS enclosures top ARCOUPL bars Locking nuts with cotter pin safeties are then used to secure ARCSTRAP Figure 12 ARCSTRAP Figure 13 Example of ARCSTRAP BUMP3 LIFTBAR Requirements for a 2 row x 4 element ARCS Array ...

Страница 16: ...d equivalent to the peak power handling for the high section These requirements typically allow the same amplifier to be used for both LF and HF sections For the high section since the drive level is attenuated relative to the low section by up to 10 dB at the crossover to compensate for component efficiency differences we can use the same amplifier since we will never deliver full continuous powe...

Страница 17: ...RCS HI Section MLS 2 dB LA48a ARCS HI Section MLS 5 dB Table 2a Recommended Power Amplification and MLS switch settings for ARCS low section ARCS LOW SECTION AMPLIFIER OUTPUT POWER REC D POWER MLS SETTING LOAD REC D LA 24a LA 48a ohms POWER 2 3000 1700 2900 do not use 0 dB 2 7 2250 1635 2700 do not use 0 dB 4 1500 1500 1600 0 dB 2 dB 8 750 1100 820 0 dB 2 dB Table 2b Recommended Power Amplificatio...

Страница 18: ...l 160 200 340 520 8 ohms Stereo 2 channel 300 400 700 1100 4 ohms Stereo 2 channel 600 750 1300 1500 2 7 ohms Stereo 2 channel 1000 1180 1465 1635 2 ohms Stereo 2 channel 1200 1400 1550 1700 L ACOUSTICS LA 48a POWER MATRIX MLS SWITCH SETTING LOAD CONFIGURATION 5 dB 4 dB 2 dB 0 dB 16 ohms Stereo 2 channel 220 260 410 650 8 ohms Stereo 2 channel 430 520 820 1300 4 ohms Stereo 2 channel 830 1000 1600...

Страница 19: ...ection 11 gauge The SP25 cable can therefore be used for 25 meter cable runs to power a 4 ohm load 2 ARCS in parallel with a damping factor greater than 20 3 ARCS CONTROL AND PROCESSING A digital processor is specified for use with ARCS in order to provide the following functions crossover filtering component time alignment corrective component equalization system protection and system equalizatio...

Страница 20: ...ver points and crossover filter slopes for example As a result ARCS presets give the user an optimum starting point system tuning should be done using output gain attenuation accurate subwoofer time alignment and system equalization not by altering crossover presets for the following reason Without proper instrumentation and spatial averaging adjustments made at one location e g the mix position a...

Страница 21: ...ow RMS signal content increase standard HF limit threshold by 3 dBu to correspond to the peak power handling for example ARCS HF limit threshold 2 dBu 5 dBu 2 rave techno music high RMS signal content long duration decrease standard HF limit threshold by 3 dBu to correspond to the RMS power handling for example ARCS HF limit threshold 2 dBu 1 dBu NOTE Setting limit thresholds to the amplifier inpu...

Страница 22: ...way presets In addition for these 2 way presets channels 1 and 4 are unlocked and available for programming of passive fill loudspeakers subwoofers or alternatively for monitoring input system equalization when using the SMAART or SPECTRAFOO measurement systems Note for BSS 366 3 x 2 way presets are provided in memory locations 37 46 This channel configuration is recommended for Left Centre Right ...

Страница 23: ...15 3 way stereo 25 SB115 A 112XT LOW A 112XT HI A SB115 B 112XT LOW B 112XT HI B 112XT 3WX SB115 3 way stereo 26 SB115 A 112XT LOW A 112XT HI A SB115 B 112XT LOW B 112XT HI B 112XT 3W SB118 3 way stereo 27 SB118 A 112XT LOW A 112XT HI A SB118 B 112XT LOW B 112XT HI B 112XT 3WX SB118 3 way stereo 28 SB118 A 112XT LOW A 112XT HI A SB118 B 112XT LOW B 112XT HI B 112XT 3W SB218 3 way stereo 29 SB218 A...

Страница 24: ...LO A 112XT HI A 112XT LO B 112XT HI B 112XT 3W SB115 3 way A SUB B 25 SB115 A 112XT LO A 112XT HI A SB115 B 112XT 3WX SB115 3 way A SUB B 26 SB115 A 112XT LO A 112XT HI A SB115 B 112XT 3W SB118 3 way A SUB B 27 SB118 A 112XT LO A 112XT HI A SB118 B 112XT 3WX SB118 3 way A SUB B 28 SB118 A 112XT LO A 112XT HI A SB118 B 112XT 3W SB218 3 way A SUB B 29 SB218 A 112XT LO A 112XT HI A SB218 B 112XT 3WX ...

Страница 25: ...A 112XT HI A dV SUB B 112XT LOW B 112XT HI B 112 X dVS 3 A 3 B 24 dV SUB A 112XT LOW A 112XT HI A dV SUB B 112XT LOW B 112XT HI B 115XT FIL 3 A 3 B 25 FULL A 115XT LOW A 115XT HI A FULL B 115XT LOW B 115XT HI B 115XT FOH 3 A 3 B 26 FULL A 115XT LOW A 115XT HI A FULL B 115XT LOW B 115XT HI B 115XT MON 3 A 3 B 27 FULL A 115XT LOW A 115XT HI A FULL B 115XT LOW B 115XT HI B 115 SB115 3 A 3 B 28 SB115 ...

Страница 26: ...112XT HI A 112XT LO B 112XT HI B 112XT 3W SB115 3 way A SUB B 16 SB115 A 112XT LO A 112XT HI A SB115 B 112XT 3WX SB115 3 way A SUB B 17 SB115 A 112XT LO A 112XT HI A SB115 B 112XT 3W SB118 3 way A SUB B 18 SB118 A 112XT LO A 112XT HI A SB118 B 112XT 3WX SB118 3 way A SUB B 19 SB118 A 112XT LO A 112XT HI A SB118 B 112XT 3W SB218 3 way A SUB B 20 SB218 A 112XT LO A 112XT HI A SB218 B 112XT 3WX SB218...

Страница 27: ... SB115 3 A 3 B 16 SB115 A 112XT LOW A 112XT HI A SB115 B 112XT LOW B 112XT HI B 112 X 115 3 A 3 B 17 SB115 A 112XT LOW A 112XT HI A SB115 B 112XT LOW B 112XT HI B 112 SB118 3 A 3 B 18 SB118 A 112XT LOW A 112XT HI A SB118 B 112XT LOW B 112XT HI B 112 X 118 3 A 3 B 19 SB118 A 112XT LOW A 112XT HI A SB118 B 112XT LOW B 112XT HI B 112 SB218 3 A 3 B 20 SB218 A 112XT LOW A 112XT HI A SB218 B 112XT LOW B...

Страница 28: ...t rows of the audience ARCS is typically arrayed in a number and configuration based on the geometry of the audience to be covered The horizontal coverage of each enclosure is 22 5 and the total horizontal coverage of the array is a multiple of 22 5 For a single row ARCS array the vertical coverage is asymmetrical providing 40 degrees by 20 degrees and cabinets can either be flown in the normal or...

Страница 29: ...o apply a separate time delay to the bottom row of ARCS enclosures so that the bottom row is time aligned with respect to the top row at the FOH mix position or approximately 30 metres from the system as a reference point 4 2 ARRAY AIMING The first task is to map the coverage of an ARCS array in the vertical plane i e section cutview in order to see how it matches the audience area to be covered L...

Страница 30: ...re 15 ARRAY Cutview simulation of an ARCS installation for theatrical sound reinforcement The flown and ground stacked ARCS arrays are both inverted to provide 20 40 degree coverage As an alternative to ARRAY CAD tools for AUTOCAD are available for representing ARCS horizontal and vertical coverage ...

Страница 31: ... Single or two enclosure ARCS arrays are the most common set up for side fill applications and ARCS can be used with or without subwoofers depending on the amount of LF extension expected by the monitor engineer or performing artist When stacked on top of one or two horizontally oriented SB218 subwoofers up to 4 ARCS can be used depending on horizontal coverage requirements In the horizontal orien...

Страница 32: ...n The following recommendations give some commonly used examples In all cases proper time alignment of fill systems with respect to the main L R FOH system is essential for obtaining optimum results Similarly pre delay to time align the overall sound reinforcement system main L R plus fill systems with the energy generated on stage is also an important consideration particularly for the first 10 r...

Страница 33: ...bwoofers plus to reduce proximity effects for the audience located close to the subwoofers For smaller set designs it can also be an option to place stereo front fill ARCS close to the subwoofers employed for onstage side fill monitors As for stacked center fill applications the height of the HF section should be optimized to suit the audience seating area with special attention paid to the first ...

Страница 34: ...l be perceived as an echo behind the main signal Time alignment of delays should be made using a measurement point on the axis of the reference source and the delayed source If the delay time setting is such that the two sound waves arrive at the same time on axis the reference source will be slightly ahead of the delayed source at any other location off axis For some applications speech it is adv...

Страница 35: ...0 134 0 136 0 138 0 140 0 10 100 1000 10000 frequency Hz dB SPL Continuous re one source SB118 SB115 dV SUB SB218 Figure 20 L ACOUSTICS Subwoofer Continuous Unweighted SPL Comparison a Combining ARCS With Subwoofers In this section we present techniques for optimizing the coupling between an ARCS array and subwoofers Two cases can be considered ground stacked systems where ARCS and subwoofers are ...

Страница 36: ...egative for sub drive in 3 way mode Table 11 Subwoofer and Low Section Processing for ARCS 3 Way Presets PRESET TYPE SUBWOOFER DRIVE SUBWOOFER BANDPASS ARCS LOW BANDPASS SUBWOOFER POLARITY 3W 3 way mode 25 80 Hz 80 800 Hz Positive 3W Separate aux drive 25 80 Hz 80 800 Hz Positive 3WX 3 way mode 25 80 Hz 40 800 Hz Negative 3WX Separate aux drive 25 80 Hz 40 800 Hz Positive 3 way mode same signal se...

Страница 37: ... position for time alignment is always a compromise since the geometrical path difference will vary with position STAGE PATH DIFFERENCE MEASUREMENT MICROPHONE FLOOR TIME DELAY SB218 ARCS dsub m dARCS d SUB PATH DIFFERENCE dsub m SB218 PATH DIFFRENCE meters 343 meters second T Figure 21 Illustration of subwoofer time alignment In most cases 3W presets are used for flown ARCS and ground stacked subw...

Страница 38: ... or 8 ARCS enclosures two BUMP3 and one LIFTBAR are required Each BUMP3 is designed to work as an assembly with one ARCOUPL To construct a BUMP3 assembly remove the two end shackles from an ARCOUPL and align the ARCOUPL and BUMP3 so that their end holes are aligned Secure the ARCOUPL rear end only with the locking nut and bolt assembly ensuring that the cotter pin safety is installed Note With ref...

Страница 39: ...ted in position and in the desired orientation refer to rear jack plates when facing downwards 40 20 deg coverage is obtained 4 Front dolleys removed note logos oriented upwards indicate that ARCS are inverted for 40 20 deg coverage 5 Front shackle removed from ARCOUPL 6 ARCOUPL slides in from the rear of the array two required top and bottom 7 Rear ARCOUPL shackle detail 8 Front shackle secures A...

Страница 40: ...COUPL secured using a locking nut and bolt assembly with cotter pin safety 12 BUMP3 assembly slides into position from the rear 13 Front locking nut and bolt assembly installed with saftey pick point selected on BUMP3 14 The final flown assembly refer to the Rigging Reference Chart for hole selection to provide the desired tilt angle for the array Figure 22 Rigging Procedure for a 4 Enclosure ARCS...

Страница 41: ...igging 1 3 or 5 ARCS 2 2 x ARCOUPL installed on the bottom of the array 2 x BUMP3 installed on top 3 The final flown assembly refer to the Rigging Reference Chart for hole selection to provide the desired tilt angle for the array Figure 23 Rigging Procedure for a 3 Enclosure ARCS Array ...

Страница 42: ...tom row using the ARCSTRAP adapter front and rear The two rows are now physically attached to each other and the array can be flown Alternatively the double row of ARCS enclosures can be stacked prior to assembly as shown in the rigging procedure illustrated below Note For a 2 x 2 element ARCS array only one BUMP3 is necessary For a 2 x 3 element ARCS array one LIFTBAR should be used along with tw...

Страница 43: ...13 2003 42 5 Front detail of ARCSTRAP attachment 6 Rear detail of ARCSTRAP attachment 7 BUMP3 slides into position from the rear 9 LIFTBAR attached to 2 x BUMP3 refer to Rigging Reference Chart for hole selection 8 2 x BUMP3 required ...

Страница 44: ...in the offstage direction For rigging up to 3 ARCS enclosures horizontally single point hangs can be performed using the rigging points available on the central spreader bar section of ARCBUMP For flying 4 ARCS enclosures horizontally a bridled hang should be performed using the exterior points on the sides of the ARCBUMP frame Safety steels must be employed for all flown horizontal applications T...

Страница 45: ...5 Safety steel detail front top and bottom 6 ARCBUMP attached to the array using 2 x ARCOUPL top and bottom 7 Safety steels are used to secure ARCBUMP to the array front and rear top and bottom 8 Front view 9 Side view note shackle attached to central spreader bar section for single point hang 10 Rear view ...

Страница 46: ... start to raise the array 12 As the array is raised use the rear handles to rotate the system into the correct orientation 13 The final flown assembly front view 14 The final flown assembly rear view Figure 25 ARCBUMP rigging procedure for a 3 enclosure horizontal ARCS array ...

Страница 47: ...idled hangs are also recommended for 1 3 ARCS arrays in order to compensate for ARCS enclosure center of gravity offset in the horizontal plane 5 4 SAFETY RULES Always consult a certified rigger if you have any questions regarding safe rigging practice L ACOUSTICS recommends the use of safety steels at all times Always install two ARCOUPL coupling bars between adjacent enclosures top and bottom Th...

Страница 48: ...L ACOUSTICS ARCS Manual V2 0 13 02 03 47 Table 13 ARCS Rigging Reference Chart ...

Страница 49: ...2 5 for LOW and SUB channels 7 turn off the pink noise Set all amplifier output levels to 0 dB gain Un mute all crossover output channels and the system is ready for use Remember the old saying amps on last amps off first in order to avoid component damage due to power on off transients 6 1 RECOMMENDED MAINTENANCE PROCEDURES a HF Diaphragm Replacement To access the HF compression driver for servic...

Страница 50: ... enclosures should be checked every month or even more frequently A frequency response check can be performed with a high resolution RTA real time analyzer or preferably using WINMLS SMAART SPECTRAFOO TEF or MLSSA measurement systems Refer to the on axis amplitude frequency response in order to determine if the response of your ARCS enclosure is within specification In addition a response sweep us...

Страница 51: ... 2 enclosures 133 dB continuous unweighted 1 m 2WLO preset 4 enclosures 137 dB continuous unweighted 1 m 2WLO preset Nominal Directivity 22 5 horizontal symmetrical 60 vertical asymmetrical 20 down x 40 up Components LF 1 x 15 weatherproof loudspeaker bass reflex loaded 3 voice coil HF 1 x 1 4 compression driver mounted on DOSC waveguide and lens Material Baltic birch plywood 15 18 and 24 mm Seale...

Страница 52: ...L ACOUSTICS ARCS Manual V2 0 13 02 03 51 Figure 26 ARCS line drawing ...

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