JBL Technical Note - Vol.1, No.12C 电路原理图.pdf

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1、Introduction: When Jim Lansing founded JBL in 1946, he brought with him a number of traditions devel- oped during his previous years at Lansing Manufacturing Company and at Altec-Lansing Corporation. One of these dealt with polarity conventions different from those eventually adopted by the burgeoni

2、ng loudspeaker manu- facturing community. The majority of JBL trans- ducers at that time exhibited inward motion of the cone when a positive-going signal was applied to the red input terminal, and this con- vention was, in many cases, carried over into loudspeaker systems as well. As we can best det

3、ermine, the original polarity decision had been made by Lansing on an arbitrary basis. As industry standardization began during the 1950s, JBL took note of the fact that the com- pany already had a large base of users in the field and that the productive “lifetime” of JBLs transducers was indeed a l

4、ong one. Any sub- stantial change in product operating standards for existing models would have caused chaos in the field. The situation began to change when JBL first introduced systems intended primarily for musical instrument (MI) applications. Since these systems traditionally used 1/4 phone plu

5、gs for signal input, there was no easy way for the user to invert the input signal polarity. However, there was a need for JBLs MI prod- ucts to be consistent with the rest of the indus- Technical Notes Volume 1, Number 12C Polarity Conventions of JBL Professional Transducers and Systems try, since

6、there has always been considerable mix- ing and matching of systems from different manu- facturers in the field. As time has gone on, there have been many pres- sures, both internal and external, for JBL to convert to the “positive-to-red” standard. Such a prospect has never been taken lightly, simp

7、ly because no company has more transducers in active use in the professional field than JBL. Beginning in the early 1990s, JBL began an orderly transition to the positive-to-red standard in accor- dance with practices recommended by the AES, EIA, IEC, and other standards organizations. This process

8、has been underway since that time, with changes being applied to new transducer models and loudspeaker systems. The firm decision was made that no “legacy” transducers in existence at that time would be changed during their remaining catalog lifetime. In most cases, JBL loudspeaker systems, even if

9、they make use of negative polarity transducers, have been internally wired so that they “behave” as positive systems. That is, a positive sig- nal at the red or positive terminal of the system will cause the low frequency cone to move outward. For the transition to be orderly, it is essential that a

10、ll users of JBL Professional products have access to a complete listing of polarity conventions of current and past products, and that all new and updated specification sheets carry a clear indication of polari- ty. In addition, all new cone transducers, which will be of positive polarity, will carr

11、y a small sticker placed next to the terminals indicating the new convention. Bi- and triamplified systems are very common- place today, and these have all been config- ured at the input connector to produce a posi- tive low frequency output signal when a posi- tive-going signal is presented at pin

12、2 of the XLR input or tip of a tip-ring-sleeve input con- nector. The assumption is made that all con- nections in the system have been locked in place internally by JBL and that all pertinent field assembly documents have been carefully followed. A further assumption is that systems using quarter-i

13、nch or Speakon connectors have been wired according to industry polarity standards. This new version of Technical Notes Volume 1 Number 12 spells out the polarity conventions of all current products, along with those of ear- lier products and product groups that have been discontinued but which may

14、still be used in the field and that are supported by repair activities and spare parts. This new publication is current as of the second quarter of 2005. Terminology: Positive systems: A system or transducer is said to be positive if a positive-going voltage applied to its red (or non-black) input t

15、erminal causes a positive pressure at the acoustical output of the device. For cone transducers, the cone will move outward and can be easily seen. For compression drivers, a positive- going pressure can be measured at the drivers exit. Many systems and transducers do not have color-coded input term

16、inals, and in these cases one terminal is usually labeled with a + sign. Consistent with the positive standard, a posi- tive-going signal at the positive terminal will result in outward motion of the cone. Negative systems: A system or transducer is said to be negative if a positive-going voltage ap

17、plied to its red (non-black) terminal causes a negative pressure at the output of the device. Polarity of JBL Professional systems and transducers: The following is a comprehensive listing of for- mer and current JBL Professional systems and transducers by product category. Within each category mode

18、ls are indicated as positive or negative. The obsolete models included here are those that are still supported by company repair service and spare parts. Musical instrument transducers: The following models are negative: E110-8E120-8, 16 E130-8E140-8 E155-4, 8 The following models are positive: M121

19、-8 M151-8 Control Monitors: all models are positive: Control 1Control 1 Plus Control MicroControl 1AW/70 Control SB Micro Control 5 Control 10L, R Control SB-1 Control SB-5 Control 12SR Control Contractor Series Studio Monitors: All 4300-Series models (except models 4311 and 4312L, R) are negative T

20、he following models are negative: 44064408L, R 4410L, R4412L, R 4425L, R4430L, R 4435L, R The following models are positive: 42064208 43114312L, R 4408A-L, R4410A-L, R 4412A-L, R6208 DMS-1LSR4300-Series LSR-SeriesLSR6300-Series Compression Drivers: the following models are negative: 2402H2404H 2405H

21、2426H, J 2427H, J2446H, J 2447H, J2450H, J 2451H, J Cone Transducers: the following models are negative: LE8T-H2105H 2118H, J2123H, J 2202H2206H 2220H, J2226H, J 2235H2240G, H 2241G, H2245H The following models are positive: 2012H2020H 2242H Coaxial transducers: the following models are positive: 21

22、42H2152H 2155H Cinema systems: 3000-Series systems; the following models are positive: 3622N3677 36783632 3632T3678-LF 3639 4000-Series systems; the following models are positive: 46224622N 46324632T 4000-Series systems; the following models are negative: 4670D4675C 4675C-4LF4765C-8LF 5000-Series sy

23、stems; the following models are negative 56715672 5672Bi5674 Cinema subwoofers; the following models are negative: 46424645 Cinema subwoofers; the following models are positive: 36354641 4642A4642A-GS 4645B4645C Cinema surround systems: the following models are negative: 83308333 8340 Cinema surroun

24、d systems: the following models are positive: 33108325 8330A*8340A* (*Note change from previous model numbers) Enclosed utility systems: The following models are positive: SLT-14612OK 8216A8216AT The following models are negative: 4660A4671OK 4652 Application Engineered Series (Prefixes AM, AC, AL,

25、ASB, SH): all models are positive Architectural Series (Prefix AS): all models are positive Array Series (Models 4890A, 4892, 4893, 4894): all models are positive Cabaret Series (Models 4602, 4612, 4622, 4623, 4625, 4627, 4680, 4690, 4695): all models are positive Concert Series (Models 4825, 4828,

26、4842, 4845, 4847, 4850, 4851, 4852, 4853, 4860, 4861, 4862, 4863, 3866, 4870, 4871, 4872, 4873): all models are positive Control contractor Series: all models are positive EON Systems (Prefix EON): all models are positive HLA Series (Prefix HLA): all models are positive JRX Series (Prefix JRX): all

27、models are positive MPro Series (Prefix MP): all models are positive Marquis Series (Prefix MS): all models are positive MR Series (Prefix MR): all models are positive Precision Directivity Series (Prefix PD): all models are positive Soundfactor Series (Prefix SF): all models are positive Sound Powe

28、r Series (Prefix SP): all models are positive SR Series (Prefix SR): all models are positive SR Series X (Prefix SR): all models are positive SR Series II (Prefix SR): all models are positive SRX Series (Prefix SRX): all models are positive TR Series (Prefix TR): all models are positive Venue Series

29、 (Prefix VS): all models are positive Vertec Series (Prefix VT): all models are posi- tive VRX Series (Prefix VRX): all models are positive General Note on Applications: JBL Professional has always recommended that absolute polarity standards be maintained throughout an audio system, from microphone

30、 input to loudspeaker output. Since most micro- phone and electronics manufacturers adhere to the “pin-2 hot” convention, this ensures that a positive-going signal at the input of a micro- phone will produce a positive-going signal at the non-ground output of a power amplifier at the end of the chai

31、n. If JBL negative conven- tion loudspeaker systems or transducers are used, the required polarity inversion should be made at the system or transducer input termi- nals themselves.Note carefully: making the polarity inversion anywhere else in the audio chain is an invitation to confusion. A Harman International Company JBL Professional 8500 Balboa Boulevard Northridge, California 91329 U.S.A. TN VOL 1 NO 12C CRP 06/05 Copyright 2004 JBL Professional