The IAQ-1 System includes an outboard digital signal processor (DSP) for active equalization and crossover functions. In an active system the amplifier follows the crossover, rather than the reverse. Each speaker is tri-amplified, so a stereo pair requires six channels of amplification.
An active crossover is a must for a minimalist open baffle speaker, due to the need for equalization. Digital processing provides boost with a rising slope toward the lower frequencies, to compensate for dipole cancellation.
Beyond the practical benefits of DSP, there are performance advantages. All drivers are wired directly to the amplifier with no passive crossover elements in the signal path. The amplifier and cables have an easy job compared to passive systems. You soon realize that expensive specialty components are not needed for exceptional performance.
Two fabric dome tweeters are installed with one facing front and one back. The rear facing dome is wired in reverse phase, to form a dipole. These tweeters have compact neodymium magnets and slim mounting depth so they can fit compactly, with the motors just touching, back to back.
Dome tweeters are not inherently dipolar because their motor assembly gets in the way of sound generated behind the diaphragm. Using two domes makes the sound at the back quite similar to the front. The 22mm dome size is small enough for wide coverage but plenty robust, including a boost from working in pairs.
An upper baffle just wide enough to fit the midrange is essential to maintain a true dipole directivity pattern. This midrange driver has an advanced low-distortion motor design with a compact neodymium magnet and streamlined basket structure. Sound escapes easily from behind the cone to maintain front / back symmetry.
A 3-way design allows enough woofer size for solid bass, plus a dedicated midrange driver to cover most of the critical vocal region.
Ideally the midrange cone should be less than a wavelength in diameter within its range. In this case the midrange cone corresponds to a 2.2 kHz wavelength, and the mid to tweeter spacing is 2.8 kHz (center to center between the drivers). A 2.1 kHz crossover frequency allows a seamless transition between the drivers, plus a generous listening area. The sound remains natural even when you are standing.
To compensate for bass output that is lost to cancellation, a dipole speaker needs more woofer surface than a box type speaker. Four 8″ (22cm) woofers work together like a single larger cone. This size driver has a slim mounting depth that accommodates a rear grille, and keeps the mass centered over the footprint. Mounting the drivers behind the baffle aligns the acoustic center with the midrange and tweeters above.
These drivers have high efficiency thanks to rigid but lightweight fiberglass cones. Low moving mass reduces vibration, not a trivial matter for a dipole speaker because the cones move further than a conventional boxed speaker.
Having this much woofer cone surface also delivers impressive mid-bass. Drums, bass guitar and upright bass all sound phenomenal on good recordings, with serious headroom that your neighbors will appreciate too.
Historically, dipole speakers have been known for giant baffles, generally in pursuit of bass extension without resorting to active EQ. However, the IAQ was designed for compact size. DSP control was part of the plan from the beginning, for several reasons including active equalization of the bass response.
The size and woofer complement of the IAQ intentionally leaves room for a subwoofer, with the dipole bass array covering 50 Hz to 300 Hz. Including a subwoofer (or two) adds headroom and bass extension, and allows scaling the system for larger rooms and greater output. However, in smaller rooms the IAQ can run full range with plenty of bass for most types of music.
Nine parallel layers of 3/4″ (19mm) plywood are glue-laminated to form the lower cabinet. The material, called Appleply, is an all-hardwood panel made in Oregon, a premium version of Baltic Birch. The upper baffle has two layers of 1/2″ panel, plus a 3rd layer to fit the rear tweeter.
Panel edge grain makes up the majority of the cabinet surface, and transparent finishes reveal the distinctive layering of the material. Hand-rubbed oil-based varnish has a smooth sheen that visitors want to touch.
Magnets secure grilles at both sides of the lower cabinet, for a more subtle appearance.
Custom Speaker Cables
Custom made speaker cables are included, with six conductors rather than the usual two. Speakon terminals on the cabinets allow instant and foolproof connection. At the amplifier end of the cable, the six conductors fan out and have banana plugs for conventional amplifier binding posts. Length and terminal options are available as requested.
A wide stance serves to steady the cabinet against woofer vibration, including a bump from a rambunctious Great Dane. Footers should be adjusted to make contact at all corners.