Infinity Composition Prelude P-FR loudspeaker
What a bizarre marriage it was, then, to pair the new Infinity Composition Prelude P-FR loudspeakers with the Cary Audio Design CAD-300SEI 11W single-ended triode amplifier (reviewed elsewhere in this issue). This combination didn't happen by accident; as you'll see, these apparently disparate products are a match made in heaven.
I discovered the Infinity Preludes while surveying Home Theater loudspeaker systems for the upcoming second issue of the Stereophile Guide to Home Theater. In addition to evaluating the loudspeaker systems under review with video soundtracks, I assessed their musical qualitiesor lack thereof. The Preludes were such a musical standout that I rescued them from the Home Theater room (where they had been powered by mass-market receivers and fed with a laserdisc source) and gave them a new lease on life in the larger music room, with reference-quality source and amplification components. The Preludes' extraordinary musical performance and unique design compelled me to tell you about how they performed in an audiophile-quality two-channel playback system.
Moreover, the Preludes, with their astounding 96dB sensitivity (2.83V/1m) and integral powered woofer, seemed an ideal load for a single-ended amplifier such as the Cary CAD-300SEI integrated amplifier. At $3395, the CAD-300SEI is also a good price match for the $3000/pair Composition Prelude P-FR.
So that's the story of how my listening room ended up home to the two most disparate products imaginable.
Description The Infinity Prelude represents a bold new approach to loudspeaker design. Created by Laurie Fincham (formerly of KEF) and his protégé Andrew Jones (also once with KEF), the Prelude is the culmination of an 18-monthlong, ground-up development effort. Every driver and component in the Prelude was designed from scratch specifically for this product, with some design aspects pushing the envelope of what is possible in loudspeaker technology.
The Prelude was designed to combine simplicity of use, elegance, and good video soundtrack reproduction in a Home Theater loudspeaker system. Infinity has more than met those goals (see my review in the Stereophile Guide to Home Theater); but, perhaps more importantly, they created a loudspeaker that provided audiophile-quality musical performance at an affordable price.
The entire Composition Home Theater package consists of left and right loudspeakers with integral powered woofers (the Prelude Full Range, or P-FR), a center-channel speaker (the Prelude Center Channel, or P-CC, footnote 1), and a pair of surrounds (the Prelude Quadrapole Surrounds, or P-QPS). These components are available separately or as a $4448 package. I'll just consider the $3000/pair P-FR left and right loudspeakers in this review.
The P-FR looks unusual, to say the least. The narrow but deep lower enclosure holds a side-loaded 12" woofer. A tall column containing the midrange and treble drivers rises from the woofer enclosure, making the column look a little like a stovepipe. A grille wraps partially around the column, covering the drivers without adding a diffraction-producing obstruction. With a width of only 7.5" at its widest point, the Prelude presents a low profile in the listening room. Nonetheless, the Prelude's sleek, rounded contours and charcoal-gray color make a bold aesthetic statement. It's difficult to overstate the Prelude's elegant and beautiful visual design"wow" is often the response of visitors upon seeing it.
The enclosure is supported by feet that protrude from the woofer-cabinet edges. You can thread four smooth, flat glides into the feet to make the Prelude moveable, or insert spikes (supplied) for more permanent installations. Switches on the enclosure's bottom rear panel adjust bass level in three increments, change the grounding scheme, and set the Prelude into automatic shutoff mode when no input signal is detected within 10 minutes.
A built-in amplifier drives the system's 12" woofer; you simply connect a pair of loudspeaker cables to the single pair of five-way binding posts. Because of this design, whatever amplifier is driving the Prelude needs power only the midrange and tweeter column. The amplifier is thus relieved of the burden of driving a large amount of current through the woofer's voice-coil. This is one reason why the Prelude is such an appealing load for low-powered tubed amplifiers.
High sensitivity The main reason I acquired an 11Wpc single-ended tubed amplifier to drive the Prelude was, however, the speaker's extraordinarily high sensitivity. With its 96dB rating, the Prelude will play as loudly with the 11W Cary 300SEI as an 87dB-sensitive loudspeaker will play with 88W.
This high sensitivity was achieved with several techniques. First, by using so many drivers (eight per enclosure), the overall radiating area was increased. Moreover, the four-way design allows each driver to be operated over a narrow passband, one where the driver is most sensitive. Second, the drivers represent a groundbreaking, one-year research effort into making a more efficient motor structure. According to Laurie Fincham, only about 25% of a conventional driver's magnetic energy gets into the voice-coil gap. The motor structure developed for the Prelude focuses the magnetic field so that 75% of the magnetic flux gets into the gap. When the voice-coil sits in a stronger magnetic field, it takes less current flow through the voice-coil to pull the voice-coil back and forth, and with it, the cone. Consequently, more of the amplifier power goes to producing sound, and less power is wasted heating the voice-coil.
Surprisingly, the Prelude's single-dome tweeter can keep up with six highly sensitive midrange drivers and a powered woofer. In fact, the tweeter is actually more sensitive than are the other drivers; it's padded down to match the other drivers' output levels. The tweeter uses a shielded Neodymium Iron Boron magnet structure, and is horn-loaded by an "elliptical waveguide" molded into the front baffle. The waveguide increases the tweeter's sensitivity, allows a lower crossover point, and controls the dispersion.
Inside the Prelude Each midrange column contains seven drivers in a line array: four 5.25" lower-midrange units, two 4" upper-midrange drivers, and one 1" soft-dome tweeter in the middle of the column. The Prelude is thus a four-way loudspeaker (including the single 12" woofer). The lower-midrange units use stiffened paper cones (plastic was too heavy to achieve the sensitivity goal), and the upper-midrange diaphragms are made from polypropylene. Crossover frequencies are 110Hz, 350Hz, and 3kHz, with varying slopes. The 20-liter column is high-passfiltered at 110Hz with a fourth-order slope, and the woofer is high-passfiltered at 15Hz with a first-order slope. Two small ports at each end of the column provide reflex-loading of the midrange drivers.
Although the column contains seven drivers, it's barely wider than the 5.25" lower-midrange units. This narrow profile confers the advantages of low diffraction, wide dispersion, and excellent imaging; it's no coincidence that minimonitors and other narrow-baffle designs disappear more easily into the soundstage than do large boxes.
The column is made from 3/16" extruded aluminum with a steel baffle. The unusual rounded back discourages the formation of standing waves and makes the enclosure less resonant. A charcoal-gray paint finishes the column.
An 18-liter sealed woofer enclosure houses the Prelude's side-firing 12" drive-unit. The woofer features a massive, 70-oz magnet in a diecast frame that uses the same focused field structure as that used in the midrange drivers and tweeter. The cone material is Infinity's IMG (Injection Molded Graphite), a blend of damped polypropylene and graphite fibers. IMG, used in Infinity's IRS Beta and Epsilon woofers, reportedly provides high rigidity, low mass, and high output without distortion.
Loading a 12" woofer in such a small enclosure puts the resonant frequency very highin this case, 85Hz. To extend the bass response, the woofer's integral power amplifier is equalized to provide flat response (the system is down 2dB at 35Hz, $*6dB at 25Hz). The woofer amplifier power isn't specified, but the Preludes each draw a maximum of 300W from the AC outlet [meaning the woofer amplifier probably produces around 100WEd.].
The Prelude is a bold effort that rethinks some of the accepted wisdom of loudspeaker design and aesthetics. This was clearly a pioneering design effort that attempted to break free from the traditional loudspeaker paradigms. Moreover, the execution was first-ratethe build quality and finish detail are superb.
Listening In the following description of the Prelude's sound, you won't find any qualifications such as "The Preludes were superb for a Home Theater loudspeaker." Once the Preludes were moved to my music room, I judged them by the highest audiophile standards.
First, the Prelude had an exceptionally smooth, uncolored sound. Its lack of bass bloat and refinedeven politetreble produced a sophisticated, understated sound. This wasn't a loudspeaker that called attention to itself; instead, the Prelude got out of the music's way and reproduced the signal with very little editorial interjection. The Prelude made the music rather than the loudspeakers the center of attention.
The Prelude's treble was clean and detailed, yet not aggressive or etched. It struck a perfect balance between treble resolution and smoothness. The result was an ability to hear lots of fine musical detail without listening fatigue or feeling that my ears wanted to close. The treble refinement and lack of etch seemed to invite me into the music rather than keep me at arm's length. In addition to being well-balanced with the rest of the spectrum, the Prelude's treble lacked grain or metallic brittleness. Cymbals had just the right degree of sheen and air, and weren't overlaid with the "spray can" white-noiselike sound produced by some tweeters. Similarly, vocal sibilance was less spitty and intrusive than I've heard from many loudspeakers. In this regard, the Prelude's treble balance and cleanliness approached the performance of ribbon drivers.
Some listeners may, however, find the Prelude's treble too polite, particularly when driving them with smooth-sounding tubed amplifiers. Fortunately, you can simply toe-in the Prelude slightly for a brighter presentation and increased sense of immediacy. I did all my auditioning either with no toe-in (with the ARC VT150s) or just a little toe-in (with the Cary CAD-300SEI), which ameliorated the Cary amplifier's lack of top-octave air. That's another reason why the Prelude is ideal for single-ended tubed amplifiers: you can dial-in nearly any treble balance you want to compensate for tubed amplifiers' sometimes rolled-off trebles.
This smooth and refined treble was matched to a remarkably uncolored midband. Vocals had an open and unfettered quality that made them seem to exist completely outside the loudspeakers. There was no trace of nasality, congestion, honk, or a hooty quality. In addition to the lack of midband coloration, the Prelude had a wonderful transparency that allowed me to hear deep into the soundstage. The speaker was highly resolving of midrange detail, easily revealing the differences between digital interconnects, for example.
Although the Prelude was highly resolving of the signal fed it, they were never etched, analytical, or "ruthlessly revealing." Instead, the detail was presented in a natural, gentle way that produced a tremendous sense of musical ease and refinement.
When auditioning the Prelude as a Home Theater loudspeaker, I was struck by how smooth the bass sounded. Most Home Theater loudspeakers have a sluggish boom in the lower bass and a lack of articulation in the midbass. Not the Prelude: it had an extraordinarily well-defined and detailed bass, with no hint of boom or bloat.
Acoustic bass was particularly well-served by the Prelude; I could hear detail and nuance often smeared by lesser loudspeakers. Consequently, I found myself greatly enjoying virtuoso bass performancessuch as Eddie Gomez's playing on Chick Corea's Friends (Polydor 849 071-2), or his work on Steps Ahead's eponymous debut record (Elektra Musician 60168-2). The Prelude's superb pitch definition and bass articulation were significant factors in my enjoyment of music through it.
Moreover, the bass was seamlessly integrated with the lower midrange. Descending or ascending piano lines that crossed the transition showed no discontinuity or change in character.
The bass was also deep and extended but didn't stretch into the lowermost octaves with the authority I'm used to from the mighty Genesis II.5s. The organ-pedal tones on Timothy Seelig's and the Turtle Creek Chorale and Women's Chorus of Dallas's performance of Rutter's Requiem (Reference RR-57CD) were audible, but the lowermost tones (16Hz) were rolled-off. Nonetheless, the bass extension was deeper than you get from most $3000/pair loudspeakers.
Although the bass was highly articulate, it was on the lean side. Rather than sounding weighty, full, and authoritative, the bass was tight, polite, and refined. I much prefer bass quality to bass quantity, but I would have liked a little more visceral impact and weight from the Prelude. Note, however, that I had the Prelude in a 21' by 18' room, well away from the rear and side walls (and with the woofer-level switch in the "high" position). When placed closer to room boundaries (as I used them in the Home Theater room), the Prelude had greater authority and bass power. Nonetheless, you wouldn't think the Prelude's bass was produced by a big woofer in a reflex enclosure with an underdamped alignment.
The Prelude had a tremendously "quick" bass, with no overhang or smearing. Kickdrum had a "sudden" quality that made it jump out from the presentation and stop as quickly as it started. This quality, coupled with the articulate midbass, combined for a tight, quick, and punchy bottom end.
The rest of the spectrum had similarly impressive dynamics. The snare drum on Michael Ruff's Speaking in Melodies (Sheffield CD-35), for example, had a huge sense of snap and impactparticularly with the ARC VT150s driving the Prelude. The overall dynamic contrast was exceptionally wide: the Prelude could play loudly without congestion and resolve fine detail during quiet passages. Moreover, transients were reproduced with razor-sharp leading edges, with no smearing or dulling of transient detail. Microdynamics were also impressive: listen to drummer Steve Gadd's gentle rim work at the beginning of the aforementioned Friends record, or Ralph Humphry's brushes on Mike Garson's The Oxnard Sessions, Volume Two (Reference RR-53CD).
The icing on the cake was the Prelude's spectacular soundstaging. These loudspeakers threw a precisely defined space before me, with a spatial coherence that was among the best I've heard from any loudspeaker. I could hear precisely where each instrument or voice was in the soundstage, and images were highly focused, tight, and compact, making the presentation sound like a collection of individual instruments in three-dimensional space. There was also a remarkable stability and tangibility to the images, further heightening the impression of instruments before me. Moreover, the Prelude completely disappeared into the soundstage, giving no clue that the sound was being reproduced by two spaced sources. Soundstage depth was also impressive, with both a sense of distance and gradations of layering. The Genesis II.5s had, however, a larger overall soundstage size (width and depth) and presented more bloom and envelopment in the acoustic surrounding the instruments. The Preludes tended to sound smaller and more intimate, with less air at the soundstage edges.
As a result of these specific sonic attributes, I greatly enjoyed music through the Preludesparticularly with the Cary 300SEI. Even with my standards set by the $37,000 combination of the Genesis II.5s and Audio Research electronics, the $6395 Prelude/Cary pair was intensely involving musically.
Although some of the credit goes to the Cary single-ended amplifier, the Preludes were able to communicate the quality of the recordings and source componentsand, consequently, communicate the music. In addition, I heard many of the qualities described when auditioning the Prelude with mass-market audio/video receivers for the Stereophile Guide to Home Theater. Although the A/V receivers didn't provide the treble purity and soundstaging I experienced with the tubed electronics, I still heard the Prelude's uncolored tonal balance, excellent bass articulation, and wide dynamics.
With the Cary CAD-300SEI, the Prelude produced completely satisfying playback levels. It's amazing what 11W will do with a 96dBsensitive loudspeaker (and a powered woofer). This combination was absolutely magical, bringing the purity of single-ended triode amplification to an uncolored, audiophile-quality loudspeaker and providing bass performance that wasn't dependent on the tubed amplifier. The Preludes are the load for low-powered tubed amplifiers.
My only reservation is that you may not be able to audition the Preludes under ideal conditionsthey're sold primarily by mass-market stores rather than by specialty-audio retailers. Although they sounded good in the Home Theater system, they didn't really sing until they were optimally set up in the larger music room and driven by topnotch source and amplification components. Once the word gets out about how the Preludes sound with single-ended tubed amplifiers, I suspect more high-end dealers will carry the Preludes. Then you can audition them in their full glory.
Conclusion The Infinity Composition Prelude P-FR loudspeaker is a stunning musical, technical, and aesthetic achievement. Even without its high sensitivity, the Prelude's smooth and uncolored tonal balance, wide dynamic contrast, articulate bass, and wonderful soundstaging would make it a standout. But with its ability to be driven to satisfying levels using an 11W single-ended triode amplifier, the Prelude becomes the loudspeaker for such amplifiers. Indeed, the $6395 Cary CAD-300SEI/Prelude combination was one of the most musical-sounding systems I've heardregardless of price.
It is difficult to criticize the Prelude at its bargain price of $3000/pair. I've heard high-end loudspeakers costing more than twice the Prelude's price that didn't provide anywhere near this level of musical performance. None$*theless, I found the bass balance a little on the lean side in my large rooma little more weight and authority would have been welcome. In addition, the polite treble contributed to less sense of air, which made the soundstage less expansive than that heard from many loudspeakers.
My descriptions of specific aspects of the Prelude's performance throughout this review don't tell the whole story. What I want to leave you with is how greatly I enjoyed music through the Prelude, particularly with the Cary 300SEI. I experienced many transcendental musical moments with this moderately priced combination.
The Infinity Prelude is worthy of my highest recommendation. In fact, I gave them the ultimate vote of confidence: I bought the review samples.Robert Harley
Footnote 1: The P-CC basically consists of the center, sealed-box section of the P-FR turned on its side. As might be expected, other than lacking the low-frequency extension of the P-FR's active woofer and having dispersion patterns rotated through 90°, we found its performance to be identical.John Atkinson