Fourier 6 loudspeaker

The Fourier 6 has the special ability to generate large coherent sonic fields, from a box small enough to slip into an ordinary shopping bag. At $499/pair, the 6 competes directly with another remarkable-imaging, compact American speaker, the Spica TC-50 ($420/pair).

The success of both the Spica and Fourier does not arise from new discoveries, old alchemy, or any other audio magic, but instead from the application of computer-aided design (CAD) and good engineering. The 6 is the least expensive model in Fourier's current lineup, and to my ears the most coherent. Computer systems analyst/mathematician Bruce Zayde teamed up with Peter Aczel, formerly publisher and editor of The Audio Critic, to apply proven mathematical concepts and CAD to the design of drivers, crossover network, and enclosure. The resulting model 6 produces a smoothly coherent, large sound field typically found only in much larger systems.

Similarly, John Bau created the Spica TC-50 with his Hewlett-Packard 9845, a dual-module software package developed by Deane Jensen of Jensen Transformers, and Richard Heyser's time-delay spectroscopy (TDS) instrument, the Tecron System 10. The result of this CAD work, the prism-shaped TC-50, employs a 1" tweeter and 6.5" acoustic-suspension woofer, with a unique crossover and enclosure.

Although the Fourier 6 also uses a 6.5" woofer, its cone is of a proprietary polypropylene composition (the Spica's cone is doped paper), and is housed in a 0.65 cubic foot vented fourth-order enclosure. Crossover slopes of 24dB/octave are used to divide the audio spectrum at 3kHz, passing the high frequencies to a 1" soft-dome tweeter. Tweeter, woofer, and port run from top to bottom of the front baffle in vertical alignment, their close proximity supposedly helping the sonic coherence. Cabinet edges around the front baffle are beveled to reduce diffraction effects. Speaker cables are connected by means of banana-post terminals, which I have found the minimum for making good electrical contact.

The accompanying literature recommends raising the Fourier 6 off the floor; the stands sold by Fourier get them up 10". So mounted, the speakers angle up towards the listener, generating a sonic image with lowered apparent height. With eyes closed the music seems displaced downwards, somewhat like sitting in the balcony above the orchestra. Raising the speakers on 25"-high stands stimulated some annoying room interactions, so the Fouriers were auditioned on their own stands.

Sound Quality
Sonically, the Fourier 6s were well-balanced but a bit warm and rich-sounding. Their perspective on the music is close, bringing vocalists and solo instruments right up to the listener. Stereo imaging was strikingly good, with more than adequate depth. Dispersion was excellent with no evidence of a sweet spot. Centerfill was particularly good, lending a three-dimensional, palpable quality to vocalists.

Instrumental timbres were reproduced well, particularly violin and cello. String tone was bright but not hard, resonant and sharp without being metallic. Piano music had richness, due in part to the Fourier's slight emphasis in the warmth region, yet male vocalists did not sound tubby—just clean and realistic. This upper-bass accentuation did not get worse with increased volume level. The Fouriers maintained the same sonic fingerprint even when driven to 98dB levels by a Mark Levinson ML-9 capable of 240Wpc! The bass drum whacks on the Telarc CD of the Cleveland Winds did not bottom out the Fouriers' woofers. What about the Spicas? They were cooler, somewhat bass-shy (footnote 1), slightly more dynamic-sounding, and displayed more horizontal directionality than the Fouriers. In my listening room, swept frequency response measured at the woofer showed the 150;3dB point to be 68Hz for the Spicas and 58Hz (with the microphone at the reflex port) for the Fouriers—a significant difference. The Fouriers played louder than did the Spicas for the same input level—ie, they're about 3dB more sensitive—and definitely had more bass.

The lack of lower bass in the Spica, and the tightly controlled mid and upper bass, permits a good subwoofer (like the Entec, Janis, or RH Labs) to blend easily with TC-50 and does wonders for its mid- and lower-bass response. I find the Spicas most listenable and enjoyable when biamped and used with a subwoofer; for this comparison, however, they were run full-range.

After hearing of several acquaintances who fried their Spica woofers, I was hesitant to push this unfused speaker to its limits. Even so, the Spicas proved to be faster, punchier, and were better-sounding than the Fouriers on percussion and vocals. Instrumental timbres were reproduced as well as on the Fouriers, and in some cases better. The Fouriers, however, excelled in their rendition of string resonance, in solid bass response—no subwoofer needed here (footnote 2)—lack of directionality, and superb central imaging.

The Spicas did best at producing an imaging envelope all around the speakers, with both depth and space. They generated a seamless, deep, three-dimensional, wall-to-wall sonic image in contrast to the image heard mostly at stage center with the Fouriers.

I found high-powered amplifiers like the ML-9 or the VSP Labs 150 worked best with the Fouriers. The Spectral DMC-1O preamp plus Levinson ML-9 amplifier system worked synergistically with the TC-50s, yielding unusually precise and coherent imaging, and freeing the instruments or vocalists from any apparent connection with the speakers. Realism and transient speed equaled that of any system I've heard. Although neither speaker deliv ered the transparency of the Quad ESL-63 electrostatic, both generated imaging with front-to-back depth presentation and accuracy of instrumental location not possible with my physically larger Snell Type A.

Both these small speakers have top, though not identical, imaging abilities. When deciding between them, most people will weigh the wider soundstage and greater coherency of the Spica against the better bass and more resonant sound of the Fouriers.

Summing Up
To some extent the choice will depend on the future of your system: if you anticipate purchase of (or already own) a subwoofer, the Spica is a clear choice; as a turn-key system I prefer the Fouriers, by a narrow margin. Both systems are serious candidates for any audio hobbyist tired of the expense, repair bills, and shipping costs that come with ownership of huge, monolithic boxes or finicky electrostatic screens.

I welcome the day (right now!) that a pair of audiophile-quality loudspeakers can be lifted by one man and do not have to be shipped in refrigerator-sized cartons.—Larry Greenhill

Footnote 1: Some listeners to the Spicas find them downright bass-shy, but this depends on room placement, height from the floor, and associated electronics.—Larry Archibald

Footnote 2: In fact, a glance at the frequency response curve indicates that it would be difficult to mate a subwoofer to the Fouriers.—Larry Greenhill