JBL Technical Note - Vol.1, No.3 电路原理图.pdf
《JBL Technical Note - Vol.1, No.3 电路原理图.pdf》由会员分享,可在线阅读,更多相关《JBL Technical Note - Vol.1, No.3 电路原理图.pdf(20页珍藏版)》请在收音机爱好者资料库上搜索。
1、Technical Notes Volume 1, Number 3 Choosing JBL Low-Frequency Transducers A. INTRODUCTION When JBL converted its low-frequency transducers from Alnico-V magnets to SFG ferrite structures in 1978, we took the first steps in simplifying and rationalizing the line by reducing the number of models. Ther
2、e had been needless duplication and functional overlap in the line, and this often served more to confuse the user than help him. The present line-up of products includes models of the important performance classes in each size, and it is the intent of this Technical Note to explain to the professio
3、nal user how LF transducers are chosen for specific jobs. We will also explain in detail the elements of construction and design of the products which optimize them for their particular jobs. B. THE BASIC MATRIX The primary JBL transducers are grouped into a three-way matrix, shown as follows: TABLE
4、 I. SENSITIVITY: MEDIUM HIGH MAXIMUM EFFICIENCY: 0.5% - 3% 2% - 6% 4% - 10% LINEARITY: HIGH MEDIUM LIMITED 460 mm (18) 2245H 2240H (E155-8) 380 mm (15) 2235H 2225H,J 2220H,J (E140-8) (E130-8) 300 mm (12) (128H) 2202H (E120-8) Those models enclosed in parentheses are not in the normal 2200-series lin
5、e-up, but they fit structurally into the matrix in the slots indicated. The model 128H is used as the LF driver in the 4411 monitor system. C. SENSITIVITY VS. EFFICIENCY It is important to understand the difference between sensitivity and efficiency, and the various methods of rating sensitivity. Th
6、e reference efficiency is a function of the electro-mechanical parameters of the loudspeaker. It represents the low frequency output within the piston band limit (where sound propagates omnidirectionally), and will usually correlate with the measured output in the 300 Hz to 400 Hz range for 460 mm (
7、18 inch) to 300 mm (12 inch) transducers. Sensitivity relates to the measured output on-axis for a given input, which may or may not relate to the low-frequency efficiency level. JBL Professional Series low frequency loudspeakers are rated with a 1 watt input averaged from 100 Hz to 500 Hz, which co
8、rrelates directly with their efficiency ratings. JBL E Series loudspeakers are rated with the same input but averaged from 500 Hz to 2.5 kHz, since they are primarily designed for full range use. If they were rated as the Professional Series are, for low frequency use, their sensitivities would be l
9、ower. The reference efficiency percentages give the most consistent method of comparison for E series, Professional Series, and competitive loudspeakers in low-frequency applications. These can be compared by taking 10 log of the efficiency ratio. D. DETAILED DESCRIPTION OF THE MATRIX In this sectio
10、n, we will ba describing in some detail the internal parts of a loudspeaker. For those who are not familiar with the construction details of a typical JBL LF transducer, we show in Figure 1 a labeled cutaway drawing of a typical JBL Profesional series transducer. 1. MEDIUM-SENSITIVITY TRANSDUCERS: a
11、. Uses: Primary use is as LF transducers in monitor systems as well as sub-woofer designs for recording studios and motion picture theaters. For these purposes, long travel at low frequencies is essential, as is low distortion. Smooth HF response* is also a requirement for proper transition to mid-
12、and high-frequency transducers in the 400-to-1 kHz range. b. Sensitivity and Power Handling: TABLE IL MODEL RATED SENSITIVITY (1 W, 1m) CONTINUOUS PROGRAM POWER REFERENCE EFFICIENCY 2245H 95 dB 600 WATTS 2.1% 2235H 93 dB 300 WATTS 1.3% 128H 91 dB 200 WATTS 0.86% c. Internal Design and Construction:
13、VOICE COILS: Flat copper wire (See Table VI), extended over-hanging winding for maximum linearity (See Figure 2A). 100 mm (4) voice coil diameter used in larger models; 75 mm (3) voice coil diameter used in 128H. VOICE COIL FORMER: Made of aluminum, Kapton polyimide plastic, or a composite for effec
14、tive heat sinking and mechanical integrity (See Table VII). SPIDER (Inner Suspension): All models use a special design which reduces dynamic offset and instability at high drive levels, resulting in unusually low distortion and a tight transient character. 3 CONE: Straight-sided and ribbed for stabi
15、lity. Fairly large mass for optimum balance of efficiency and bass output, and low distortion. Aquaplas (TM) coating used on 2245 and 128H to optimize stiffness and mass, mass ring on 2235 for desirable efficiency and bass balance. SURROUND (Outer Suspension): Half-roll of polyurethane foam for high
16、 compliance and long travel (See Figure 3A). DUST DOME: Made of similar felted material as cone for smoothest HF response. 2. HIGH-SENSITIVITY TRANSDUCERS: a. Uses: Primary use is in sound and music reinforcement, mounted in horn and direct radiator reflex-type enclosures. For these purposes, LF con
17、e excursion has been limited and sensitivity increased, relative to the transduers of the medium sensitivity class, in order to get greater output in the 50 or 60 Hz range up to 800 Hz. b. Sensitivity and Power Handling: TABLE ill MODEL RATED SENSITIVITY (1 W, 1 m) CONTINUOUS PROGRAM POWER REFERENCE
18、 EFFICIENCY 2240H 98 dB 600 WATTS 5% 2225H.J 97 dB 400 WATTS 3.5% E140-8 100 dB 400 WATTS 4.9% 2202H 99 dB 300 WATTS 6.0% c. Internal Design and Construction: VOICE COILS: Flat copper wire, 100 mm (4) in diameter. Slightly over-hung in the magnetic gap (See Figure 2A) for proper balance of sensitivi
19、ty and linearity. VOICE COIL FORMERS: Made of aluminum, Kapton polyimide plastic, or a combination, for effective heat resistance and sinking, and rigidity. SPIDER (Inner Suspension): All models use a special design which reduces dynamic offset and instability at high drive levels, resulting in unus
20、ually low distortion and a tight transient character. CONE: Straight-sided and ribbed for stability; however, total moving mass is less than in the case of medium efficiency transducers, without the added dampening compounds or mass rings. SURROUND (Outer Suspensioh): Multiple half-roll (See Figure
21、3B) provides controlled travel. Stiffness is optimized by depth of rolls, weave of cloth, and damping treatment. DUST DOME: Made of similar felted material as cone for smoothest HF response. The E140 is similar to the 2225, but with an aluminum dome and less voice coil overhang for slightly more mid
22、range efficiency, peaked high-frequency output, and a punchy sound character. The E145 and 2234 are specialized transducers that combine high efficiency with high linearity. The E145 has a short copper coil moving in a very deep magnetic gap (Figure 2B) for maximum voice-coil control and excursion l
23、inearity. This design also provides maximum low-frequency output from a given enclosure size. The E145 can move as much air as a high efficiency 460 mm (18 inch) transducer. The 2234 is identical to the 2235 with the deletion of the mass ring. This raises the efficiency (mid-band sensitivity) for mu
24、ltiple woofer applications. The 2234 is used in the 4435 studio monitor. 3. MAXIMUM SENSITIVITY TRANSDUCERS: a. Uses: Primarily in music reinforcement for driving LF horn systems. For these applications, the range of linear travel has been restricted in a trade-off for greater sensitivity in the 50
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- JBL Technical Note Vol.1 No.3 电路原理图 Vol No 电路 原理图