2447 H/J Specification Document - JBL Professional

1 2447H/JCompression DriverProfessional SeriesKey Features:100 mm (4 in) pure titaniumdiaphragm with radial-rib topology38 mm (1 ) throat exit diameter100 mm (4 in) edgewoundaluminum voice coil150 watts continuous program at1 kHz and higherCoherent Wave phasing plugdesign for increased high frequencyoutput100 watts continuous programabove 500 HzThe Model 2447H/J is a 38 mm(1 ) exit diameter addition toJBL s family of Professional qualitycompression drivers. The 38 mm exitallows the Coherent Wave phasingplug to directly couple with OptimizedAperture Bi-Radial horns to pro-vide lower distortion and bettercoverage control to 20 kHz than pre-vious designs. In addition to improvingperformance the 38 mm design alsoreduces size and Coherent Wave phasing plugstructure has four equal length pas-sages to provide in-phase summationof diaphragm output at the 38 mmexit.

2 This optimized configurationproduces coherent acoustical powerup to much higher frequencies thanmore conventional diaphragm design includes JBL sexclusive three-dimensional diamondpattern surround tuned to reducefatigue inducing stresses in the mem-brane and support structure. Thisprovides predictable normal reso-nance modes, and radial reinforcingribs increase diaphragm stiffness. Thisdiaphragm design combined with theCoherent Wave phasing plugincreases the 2447 s output in the 5kHz to 20 kHz Specifications:Throat Diameter:38 mm (1 in)Nominal Impedance:2447H 8 ohms2447J 16 ohmsMinimum Impednace:6 ohms (H), 12 ohms (J) @ 5 kHzDC ohms (H), (J) 10% @ 25 CPower Rating :100 W continuous program above 500 Hz150 W continuous program above 1 kHzSensitivity:112 dB SPL, 1 W @ 1 m, JBL 2352 horn 114 dB SPL, 1 W @ 1 m, JBL 2353 horn 115 dB SPL, 1 W @ 1 m, JBL 2354 horn 118 dB SPL, 1 mW on plane wave tube Nominal Efficiency:30% (500 Hz to kHz)Frequency Range:500 Hz to 20 kHzRecommended Crossover:500 Hz or higher, 12 dB/octave minimunRecommended Amplifier Power4.

3 200 W into 8 mm ( in) pure titaniumVoice Coil Diameter:100 mm (4 in)Voice Coil Material:Edgewound aluminum ribbonFlux T (18,500 gauss)B1 (H) T m18 (J) T mPolarity:Positive voltage to black terminal produces diaphragmmotion toward phasing plugDimensions:235 mm (9 in) diameter100 mm (4 in) depthMounting:Four -20 studs, 90 apart on 114 mm(4 in) diameterNet kg ( lb) Continuous program power is defined as 3 dB greater than continous pink noise and is a conservative expression of thetransducer's ability to handle normal speech and music program material. Continous pink noise power ratings are testedwith a pink noise input having a 6 dB crest factor, with a high pass filter set to the specified lower frequency, for twohours duration.

4 Sensitivity measured on-axis in the far field with V rms at 8 ohms or V rms at 16 ohms and referred to a 1 meterdistance calculated by inverse square law. Listed sound pressure level (SPL re 20 Pa ) represents an average from1 kHz to 4 kHz. As specified by recognized standards organizations, JBL plane wave tube measurements represent the SPL referred to a25 mm diameter terminated tube, using a 1 mW input signal ( V rms into 16 ohms; V rms into 8 ohms) sweptfrom 500 Hz to kHz. The sensitivity with a 1 W input would be 30 dB power amplifier rating is a guide for amplifier selection considering normal program material and linevoltage available to amplifiers, although lower power amplifiers may be continually engages related to product improvement.

5 New materials, production methods, and designrefinements are introduced into existing products without as a routine expression of that philosophy. For thisreason, any currents JBL product may differ in some respect from its published description, but will always equal orexceed the original design Specification unless otherwise stated. U. S. Patent # patents Compression DriverHigh temperature voice coil former materials and adhe-sives enable the 2447H/J to handle high power levels overextended periods of time. The voice coils themselves areidentical to previous JBL models, so that impedance andnetwork matching will be the same. After manufacture, thefrequency response of each transducer is tested for confor-mity to JBL s rigid performance model 2447H/J is ruggedly constructed to withstandthe rigors of both fixed installations and touring applica-tions.

6 All tolerances are held to the same high levels tradi-tionally associated with JBL designs. The JBL manufacturingprocess permits the use of rim centered diaphragms forinstant interchangeability and ease of field Specifications:The compression driver shall consist of a ferrite magnetic structurewith all magnetic assembly parts machined from cast or extrudedbillet stock. The phasing plug shall be assembled of concentric hornsto minimize phase cancellations. The diaphragm shall be .05 mm(.002 in) pure titanium pneumatically drawn to shape and embossedwith radial reinforcing ribs to increase stiffness. High frequencyresponse shall be controlled through the use of a three dimensionalsuspension structure. The voice coil shall be edgewound aluminumribbon of not less than 100 mm (4 in) diameter, operating in amagnetic field of not less than T (18,500 gauss).

7 Performance specifications of a typical production unit shall be asfollows: Measured sensitivity with a 1 mW input on a 25 mm (1 in)terminated tube, averaged from 500 Hz to 5 kHz, shall be at least 118dB SPL. Measured sensitivity with a 1 W input at 1 m distance on-axisfrom the mouth of a horn with a Q of averaged in the 2 kHz octaveband shall be at least 111 dB SPL. As an indication of electromechanicalconversion efficiency, the B1 factor shall be at least 18 Tesla response, measured on a terminated tube, shall be flatwithin 1 dB from 500 Hz to kHz, with 6 dB/octave roll-offabove that point. Nominal impedance shall be 8 [16] ohms and powercapacity shall be at least 100 watts normal speech or music compression driver shall be the JBL Model 2447H[J].

8 Otherdrivers will be considered for equivalency provided that submitteddata from a recognized independent test laboratory verify that theabove performance specifications are on JBL 2352 Bi-Radial HornFrequency reponse of the 2447H coupled to a JBL 2352 Bi-Radial Horn, measured on-axis at a distance of 1 meter with a 1 watt( V RMS) input in a reflection free environment, with impedancevs. frequency on Plane-Wave Terminated TubeFrequency response and impedance modulus of model 2447H coupledto a 38 mm (1 in) diameter terminated plane wave tube. This is thepower response of the transducer, and is the frequency response thatwill be obtained on a true full range constant directivity horn design,such as JBL s 2350 series of Bi-Radial Professional8500 Balboa Boulevard, Box 2200 Northridge, California 91329 Harman International Company10/94 10MP1162