JBL Technical Note - Vol.1, No.1A 电路原理图.pdf
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1、Performance Parameters of JBL Low-Frequency Systems Introduction This technical note will enable sound contractors and consultants to specify JBL LF enclo sures, transducers and packaged systems to fit particular requirements. While most of the listed parameters are straightforward, some of them des
2、erve special comment. Parameter 4 states the primary use of the system. Those indicated for reinforcement are to be used primarily for fixed-installation speech reinforcement applications. Those indicated for monitor LF or cinema VLF are to be used for high-level LF performance in recording studio c
3、ontrol rooms or motion picture theaters, for response down to 25 Hz. The general term Ml means that the system is intended for electronic musical instrument or amplified instrument use. Those systems indicated for high-level music reinforcement are intended for upper-bass or lower mid-range in those
4、 applications where HF horn components must be crossed over in the 120040-1500 Hz range. Parameter 7 is the JBL traditionally conservative sine wave power rating. Program ratings are easily 3 dB greater, and transient program peaks up to 10 dB above the steady-state rating can be tolerated, provided
5、 that displacement limits are not exceeded. Parameter 8, the half-space reference efficiency of the system, assumes that the system will be placed next to a single reflecting surface. In Parameter 10, free-field ratings averaged over the system bandwidths are given. The bandwidth of a system extends
6、 from its 3 dB down point up to its recommended crossover frequency. An additional rating gives the maximum output to be expected in a reference rever berant environment with a room constant (R) of 18.6 m 2 or 200 ft2. These ratings may easily be manipulated to give the reverberant SPL in rooms with
7、 other values of R using the following equation: New SPL = Reference SPL-10 log (R/18.6), where R is the new room constant in m 2. The beamwidth data of Parameter 13 gives the 6-dB down included angle in both horizontal and vertical planes at the usual crossover frequencies of 500, 800 and 1200 Hz.
8、Both direc tivity index (Dl) in dB and directivity factor (Q) are given at those frequencies. The Systems In addition to standard JBL systems, we present a number which are based on enclosures that JBL does not build, but for which JBL supplies construction plans. These are the special horn systems
9、(*), which make use of either 300 mm (12) or 380 mm (15) drivers, depending on the application. The W horn is intended for music reinforcement applications, and the 340 L Sub-woofer is intended for theater use. Note for this system that there are two values of lower frequency limits. Those values gi
10、ven in parentheses require a different enclosure tuning and an appropriate electrical boost in the LF cut-off region, which can be provided by the JBL Model 5235 Electronic Dividing Network. Details of this are included in the plans. Finally, we present data on the models 4520 and 4530 rear-loading
11、horns no longer made b y JBL. Technical Notes Vol. 1, No. 1A Parameters Direct Radiator 1. Model 4646 4647 4648 4648-8 2. Enclosure 4512 4507 4508 4508 4518 3. Transducer Model 2204H 2225H 2225H 2225J 2240H Diameter 300mm (12) 380mm (15) 380mm (15) 380mm (15) 460mm (18) Quantity 1 1 2 2 1 4. System
12、Application Reinforcement Reinforcement Reinforcement Reinforcement Reinforcement 5. System Impedance (ohmsj Nominal CO 8 4 CO 8 Minimum 7 7.3 3.7 7.0 7.3 6. Sensitivity (1W 1m) 96 dB 97 dB 100 dB 100 dB 98 dB 7. Continuous Power Rating, watts 150 W 200 W 400 W 400 W 300 W 8. Half-space Efficiency 1
13、.7% 3.5% 7% 7% 5% 9. Maximum Continuous Acoustical Power 2.6 W 7 W 28 W 28 W 15 W 10. Maximum Continuous SPL Free Field 3 m (10) 108 dB 110dB 116dB 116dB 113dB Free Field 30 m (100) 88 dB 90 dB 96 dB 96 dB 93 dB Reverberant Field, R - 18.6 m 2 (200 ft2) 117dB 122 dB 128 dB 128 dB 125 dB 11. Lower Fr
14、equency Limits - 3 d B 70 Hz 45 Hz 45 Hz 45 Hz 50 Hz - 1 0 d B 50 Hz 35 Hz 35 Hz 35 Hz 30 Hz 12. Recommended Upper Crossover Frequency 1200 Hz 1200 Hz 800 Hz 800 Hz 800 Hz 13. Beamwidth ( - 6 d B ) 500 Hz (Hor.) 180 140 140 140 125 500 Hz (Vert.) 180 140 100 100 125 DI (Q) 500 Hz 4 dB (2.5) 6 dB (4)
15、 8 dB (6) 8 dB (6) 7 dB (5) 800 Hz (Hor.) 140 90 90 90 75 800 Hz (Vert.) 140 90 50 50 75 DI (Q) 800 Hz 6 dB (4) 9 dB (8) 10 dB (10) 10dB(10) 13 dB (20) 1200 Hz (Hor.) 90 70 - 1200 Hz (Vert.) 90 70 _ DI (Q) 1200 Hz 10 dB (10) 10 dB (10) 14. Enclosure Data Volume, L (ft 3) 34(1.2) 145 (5) 225 (8) 225
16、(8) 225 (8) HxWxD, mm (in) 406 X 470 x 273 775 x 546 x 448 1010 x667x438 1010 x667x438 1010 x667x438 (16x18 1/2Xl03/ 4) (30 1/ 2 x 21 1/ 2 x 17%) (39 3/4261/417 4) (39 3/ 4x26 1/4X 171/ 4) (39 3/ 4 x 26 1/ 4 x 17V4) Weight, kg (lb) 18(40) 36 (80) 69 (152) 69(152) 63(138) 4645 4645x2 4645x4 4625B 469
17、5B 4518 4518x2 4518x4 Sub-woofer 340 L (12 ft 3) 2245H 2245H 2245H E140-8 E155-8 2245H 460 mm (18) 460 mm (18) 460 mm (18) 380 mm (15) 460 mm (18) 460 mm (18) 1 2 4 1 1 1 Monitor LF; Monitor LF; Monitor LF; Ml Mi Cinema VLF; Cinema VLF Cinema VLF Cinema VLF Monitor LF CO 4 8 8 CO CO 7.1 3.6 7.1 6.5
18、7.3 7.1 95 dB 98 dB 101 dB 100 dB 100 dB 95 dB 300 W 600 W 1200W 200 W 300 W 300 W 2.1% 4.2% 8.4% 4.9% 4.9% 2.1% 6.3 W 25.2 W 100.8 W 9.8 W 14.7 W 6.3 W 110dB 116 dB 122 dB 113dB 115dB 110dB 90 dB 96 dB 102 dB 93 dB 95 dB 90 dB 121 dB 127 dB 133 dB 123 dB 125 dB 121 dB 35 Hz 35 Hz 30 Hz 25 (20) Hz 2
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