JBL M9500 owner manual Typical System Performance Measurements

The JBL model 475Nd compression driver used in the M9500 has a smooth titanium dome 101 millimeters in diameter that has been lightly coated with Aquaplas™ damping compound. Its aluminum ribbon voice coil operates in a magnetic flux field of 1.65 tesla (16,500 gauss). Mid-band efficiency is 20%, while at the peak value of driver impedance it is in excess of 50%. The driver uses JBL’s Coherent Wave™ phasing plug, which provides equalized path lengths from all sections of the diaphragm to the driver's output. The driver is mounted on the H9500 horn, a design used only in this system that provides smooth loading down to 500 Hz and exhibits consistent horizontal dispersion over its operating range.

There are two JBL model 1400Nd low-frequency transducers in each loudspeaker system. A single 1400Nd is capable of handling instantaneous input signals of 600 watts, corresponding to a midband peak output of 118 dB Lp at a distance of one meter. The transducer’s second and third harmonic distortion have been reduced through the use of JBL’s traditional aluminum shorting ring at the base of the pole piece, as well as through the use of a copper shorting ring on the top plate adjacent to the voice coil. The transducers make use of JBL’s Vented Gap Cooling™ in which forced air, generated by cone motion, removes heat produced by the voice coil. Each driver is mounted in its own ported enclosure, and the two enclosures are “stagger tuned” to provide smoother and more extended low-frequency response.

Cutaway views of the high-frequency and low-frequency transducers are shown in Figures 2 and 3.

Typical System Performance Measurements

The high-frequency response of the M9500 system was care- fully established by making a series of measurements over frontal angles of 60° in both vertical and horizontal planes. This allows for optimal listening over a wide area. The frequency response averaged over the 60° horizontal and vertical angles, measured from 200 Hz to 20 kHz, is shown in Figure 4. Here, the network High Frequency trim is set in its zero position. The slight downward trend was incorporated, based on extensive listening tests to contemporary pop/rock and classical recordings.

	+10
	dB
(dB)	0
level	–10
Relative	–20
	–30
	2	3	4	5	6	7 8 9 10	1.5	2	3	4	5	6	7	8	9 10	1.5	2	3	4	5	6	7	8 9 10	1.5	2
						100									1000								10000

Figure 4. Averaged frontal angle response (60°, horizontal and vertical) of M9500 from 200 Hz to 20 kHz.