MartinLogan Prodigy loudspeaker Page 2

The bass module is a sealed dual-woofer design. The forward-facing 10" ScanSpeak aluminum-cone woofer carries the bass audio signal. An independently enclosed, 10" ScanSpeak fiber-cone cone faces to the rear and is driven by a circuit that processes level, phase, and frequency range to create a partial cancellation of the front woofer's output in the lower frequencies (footnote 2). This ForceForward technology specifically reduces the common 50Hz null and 100Hz peak found in many rooms. For those requiring more forward bass, the Prodigy has a rear-panel switch for increasing the below-50Hz response by 3dB.

The wing nuts on the Prodigy's speaker binding posts can be easily tightened without pliers or a wrench. Four binding posts are supplied on each speaker, allowing for biwiring. The excellent owner's manual gives instructions for horizontal passive biamplification (use a tube amplifier for the electrostatic panels, solid-state for the bass modules) and vertical passive amplification (two identical stereo amplifiers, one dedicated to each speaker). Spiked feet—called Energy Transfer Coupler (ETC) Spikes—are supplied with jam nuts to allow for easy leveling.

I placed the Prodigys where the Revel Ultima Salon loudspeakers had sounded best: 63" from the rear wall and 36" from the side walls, sitting out in the room on a circular area rug. The speakers faced the long axis of my narrow listening room, which is 26' long, 13' wide, and 12' high, with a semi-cathedral ceiling. One long wall is covered with bookshelves, the other has a bay window. At the opposite end, the room opens into a 25' by 15' kitchen through an 8' by 4' doorway.

An electrostatic speaker needs to be plugged into an electrical outlet. When playing, the speaker displays a blue light—in the shape of the MartinLogan logo—through its electrostatic screen. Unlike the blue arcing in my old Quads, this light can be switched on and off from a pushbutton in the bass module.

Because the Prodigy's rated voltage sensitivity of 91dB/2.83V/m lies well above the average range of B-weighted speaker sensitivities reported in Stereophile, I found that I needed to set my Krell KBL preamplifier's volume control significantly lower than usual.

I first drove the Prodigys with the high-powered Bryston 7B-ST monoblocks—tested at 954W into 4 ohms—because of the 7Bs' power reserves and easily visible front-panel clipping indicators. Configured in serial bridged mode, the Brystons' bass response was very tight, deep, and fast, their soundstage huge—the bass lines on "Unfinished Sympathy," from Massive Attack's Blue Lines (Circa WBRX2), were solid and full. However, I found the soundstage depth shallow and the transients harsh. I switched the 7B-ST into their parallel bridge mode—tested at 595W into 2 ohms—which enables the amplifier to drive low-impedance loads. Although the bass became less prominent, the soundstage assumed a more natural depth and width and the edginess disappeared. Even so, I preferred the less powerful Mark Levinson No.334 to the Bryston for its sweeter, more transparent sound.

Final adjustments included comparative nearfield (8') and farfield (16') listening, low-frequency signal-generator sweeps, phase checks, pink noise, and fine-tuning of listening position for optimal soundstaging and imaging. The Prodigy's deep-bass output fell off smoothly between 41Hz and 35Hz in my listening room, with no doubling. Playing Stereophile's Test CD 3 for channel checks and phasing, I carefully positioned my chair in the Prodigys' nearfield until I could hear the in-phase pink-noise signal as a centrally focused sonic image. Soundstaging was optimized when speakers and chair described a 7' equilateral triangle (measured from the panels' approximate centers).

The Prodigy's electrostatic panel extends from 31.5" to 60" above the floor. This covers an area below my ear height (38") when I'm seated in my listening chair and extends above my ear height when I'm standing. This explained why the speaker's tonal balance didn't change when I stood while playing pink noise.

I broke the Prodigys in by playing music from an FM tuner for 12 hours, followed by 12 hours of the "Special Burn-In Noise" from Stereophile's Test CD 3.

I first put on some warmup music—David Hudson's Didgeridoo Spirit (Indigenous Australia IA2003 D), Fleetwood Mac's The Dance (Reprise 46702-2), and David Bowie singing "Putting Out Fire," from the Cat People soundtrack (MCA MCAD-1498). The Prodigys' transparency and deep, wide soundstage quickly involved me in the music. But at first, the bass response seemed understated, shy, and reticent.

After a month of listening, things had changed: The louder I played the Prodigy, the better it sounded. [Stereophile webmaster Jon Iverson also reports that the Prodigy requires a significant amount of break-in.—Ed.] Its bass blossomed when driven hard. At a level where my usually unflappable Mark Levinson No.334 began to show signs of compression, the Prodigys opened up. The bass became forceful and taut, and the instruments separated and became more distinct.

Footnote 2: In his August 2000 review of the MartinLogan Prodigy in Hi-Fi News & Record Review, Martin Colloms pointed out, "If [the two woofers] were both equal and always out of phase you would get dipole upper bass while the low bass would cancel out." MartinLogan gives an example of what happens at 50Hz: "The acoustic difference between the drivers is about 2.3'. At 50Hz, the phase shift caused by the traveling wave is about 37 degrees. When added to the 127 degrees phase shift of the passive crossover, the front waves meet with a relative phase shift of 127 degrees - 37 degrees, which equals 90 degrees. The back waves meet with a relative phase shift of 127 degrees + 37 degrees, which equals 164 degrees. The front waves meeting add at 90 degrees, causing an addition resulting in an amplitude gain of 3dB. The back waves meeting at 164 degrees causes a subtraction, leading to an amplitude reduction of 11dB. The total difference between the two waves is then 3dB + 11dB = 14dB."
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