"Stirring the stew" is what I've heard it called when a company introduces a new version of a product every three or four years. When a new product is launched, sales generally rise rapidly to a maximum and then slowly decline. If the stew is stirred every few years, plotting the product's sales volume against time results in a sawtooth wave, without sales ever dropping close to zero.

Richard Vandersteen doesn't appear to believe in stews or stirring. Vandersteen loudspeakers stay on the market for a long time, with infrequent updates. Consider the Vandersteen Quatro loudspeaker. The original version was reviewed for Stereophile by Michael Fremer in July 2006 and cost $6995/pair, with the necessary line-level high-pass filters priced at $595/pair for unbalanced operation and $795/pair for balanced. As retailers felt the plain-Jane sock that covered the loudspeaker might be an impediment to sales, Richard introduced not a new version of the Quatro with a wooden veneer finish but a different loudspeaker, the Quatro Wood, which cost $10,700/pair without the filters and which the late Wes Phillips reviewed in December 2007.

Twelve years later, there is a new version of the Quatro Wood, the Quatro Wood CT, which costs $15,499/pair in standard finish. Balanced line-level filters now cost $1295/ pair but are not necessary if the Quatro Wood CT is used with one of Vandersteen's high-pass monoblock amplifiers, the hybrid M7-HPA ($59,999/pair), which I reviewed in May 2016, or the new solid-state M5-HPA ($15,800/pair), which I am reviewing here with the Quatro Wood CT.

The Quatro Wood CT

The Wood CT looks identical to its predecessor: a slim, truncated pyramid with all surfaces finished in wood veneer. The front baffle features a vertical array of three drive-units beneath a substantial cloth-covered grille that provides the appropriate acoustic environment. Richard Vandersteen strongly believes that a loudspeaker should faithfully preserve the waveform produced by the power amplifier, including "all of the delicate time-domain relationships that comprise the recorded musical performance." The Quatro therefore uses first-order crossover filters and a sloped-back front baffle to bring the three drive-unit outputs into time alignment on the listening axis.

Two 8" subwoofer drivers, powered by a 250W amplifier, fire through a cloth-covered slot at the base of each sidewall and the back. The speaker's rear has a large black metal panel with the amplifier's heatsink fins at its base, above which are 11 trim controls for the subwoofer's 11-band equalizer, rotary Low Frequency Level and Contour controls, and four screw terminalsone pair for the tweeter and midrange passive drivers, the other for the woofer and the input to the subwoofer amplifier.

The differences between the CT and the earlier version are all inside the box. The baskets of the subwoofers are now die-cast aluminum rather than stamped steel. The front-firing 6.5" woofer is loaded with a different internal chamber, the driver's alignment optimized for free-space placement. (The earlier loudspeaker's woofer alignment was optimized for placement close to the wall behind it, which could result in a lean-sounding lower midrange with the speaker farther out in the room.) The 4.5" midrange driver still has the minimal-profile basket that Richard Vandersteen pioneered but now has a woven carbon-fiber cone rather than the original's polypropylene cone. Instead of the earlier Quatro Wood tweeter's alloy dome, the Wood CT's tweeter uses the carbon-fiber dome from Vandersteen's Model 5A Carbon.

The high-pass amplifier

As with other Vandersteen speakers that have active subwoofers, the amplifier used to drive the Quatro Wood CT needs to have its output rolled off with a first-order slope and a 3dB frequency of 100Hz. The subwoofer amplifier then applies a compensatory low-frequency boost. Designed by Richard Vandersteen and Dean Klinefelter and featuring a minimal signal path, the M5-HPA amplifier is a scaled-down, solid-state cousin of the earlier amp, offering a maximum power of 300W into 4 ohms compared with the M7-HPA's 600W. Unlike the M7-HPA, the M5 has variable high-pass settings, with a rotary switch with 3dB frequency settings of 20, 40, 80, 100, or 200Hz mounted on the main circuit board behind the balanced XLR input jack. (As I found out, the amplifier needs to be turned off before each change in the high-pass frequency.) The review samples were set to 100Hz for my auditioning.

The M5-HPA sits on four spring feet; those at the front are less compliant than those at the rear as the hefty power transformer is bolted to the amplifier's front panel. There is a Cardas double binding post on its rear panel, beneath the XLR jack, and power is supplied via a 20A IEC receptacle. The amplifier is turned on with a heavy-duty switch on the rear, following which a front-panel LED glows green to indicate the M5-HPA is in standby mode. Pressing the button next to the LED turns it blue and brings the amplifier out of standby.

Setup

Richard Vandersteen and Vandersteen Audio's Brad O'Toole visited to set up the Quatro Wood CTs in my listening room. With the speakers in what they felt were the optimal positions, Richard then placed a sound-pressurelevel meter at the height of my head in my listening chair, and Brad used a tape measure to ensure that the speakers were the same distance from the SPL meter. Using the "Vandertones," which can be downloaded from Vandersteen's website11 narrowband warble tones, one set each for the left and right channels, with center frequencies ranging from 20 to 120Hz, corresponding to the Wood CT's 11 equalizer frequenciesVandersteen adjusted the setting of each equalizer band until it gave an SPL meter reading that matched his target response. After adjusting the EQ, he tuned in the subwoofers' level and contour controls. These were respectively set to "0" and "5" for each speaker.