The system, consisting of seven main pieces, is comprised of the following:

• Two Main Towers w/ external bi-wired passive crossover
• Two Passive Subwoofer Towers
• One Variable Low Pass Filter (Electronic)
• Two IP-1 Crossover Isolation Platforms

GRAND REFERENCE IV.1 MAIN TOWER

The Main Tower employs a total of 19 of the highest quality transducers per channel. The Main Towers are built in mirror-imaged arrays for accurate imaging. Bass and mid-bass frequencies from 40 Hz to 400 Hz are reproduced by four advanced 8 inch cast frame woofers per channel. Two woofers are mounted vertically at the top and two are mounted vertically at the bottom of the Main Tower. The four 8 inch woofers employ cast, surface treated magnesium cones with natural rubber surrounds and solid copper-machined phase plugs. Perfect piston response is maintained to a high 5 kHz, far beyond their 400 Hz operating ranges, for excellent impact and low coloration. The woofers are mounted in individual sealed chambers. Cabinet walls are bonded with proprietary damping layers for inaudible coloration. The four woofers operate with staggered bass resonant frequencies to increase the speed-bandwidth product.

The all-important mid range system consists of six 110mm tri-laminate cast frame transducers, per tower, operating on an open baffle over the range of 400 Hz to 3500 Hz and driven by premium Alnico magnet systems. The six mid range transducers are deployed in a short vertical line array, between the woofers and adjacent to the tweeters. The open baffle Alnico mid- range drivers provide excellent low-level resolution and dynamics, while eliminating cabinet mid range coloration. Harmonic structure is especially accurate, while the special transient response of this driver (as has been commented on before) allows clear separation of the attack, sustain and decay elements of musical sounds- for a more life-like reproduction.

The high frequency transducer system consists of nine 4-inch ribbon tweeters per tower, operating in a short vertical line array. These transducers are true ribbons wherein the conductor and the diaphragm are one and the same. The moving mass is only .0061 gram for near instant acceleration. Extreme high-level transient attacks are taken in stride without harshness, allowing for instance, live levels of cymbals and other harmonically rich musical sounds to be reproduced. Driven by heavy neodymium magnet systems, these transducers are equally comfortable reproducing nuance as well as extreme peak levels. Nine small ribbons are utilized in lieu of one large ribbon in order to take advantage of the superior control of the smaller diaphragm, for greater accuracy.

GRAND REFERENCE IV.1 SUBWOOFER TOWER

Click here to see photos of the Grand Reference in customers' homes.

The Grand Reference IV.1 Subwoofer Towers are designed to complement the response of the main towers from 16 Hz to 40 Hz. The Main Towers operate full range to their acoustic rolloff while the Variable Low Pass Filter rolls off the response of the Subwoofer Tower at 40 Hz. A separate, high current, stable amplifier is required to drive these towers. Each Subwoofer Tower consists of four high-output 12-inch transducers operating in a vertical array. Each transducer is isolated in a separate vented chamber to eliminate inter-driver interference. A 3-inch diameter exponential flared port is provided for each 12-inch transducer. The port is flared both on the inside of the enclosure as well as the outside, for minimum low frequency distortion. Special low distortion voice coils driven by massive double-stacked 7 LB magnets for each driver, provide greater than 1¼ inch peak to peak linear excursions. Output at 20 Hz with both towers driven is greater than 120 dB.

VARIABLE LOW PASS FILTER

Based on a design pioneered by Carl Marchisotto when at Dahlquist in 1976, this remains the preferred way to integrate a subwoofer system with a high-quality, wide-band main transducer. The LP1 provides continuously variable cut-off frequencies from 37 Hz and up. Stereo bass is provided. Fine touch-up qualization is provided to trim the extreme low frequency response on each channel to match different rooms.