09-25-2001, 12:36 PM
Polk Audio RT25i loudspeaker
By Robert J. Reina, September 2001
Polk Audio is the Rodney Dangerfield of high-end audio. Why does this conscientious, innovative, and well-organized company garner no respect from hard-to-please audiophiles? Well, for years we've all seen the multipage glossy color ads featuring designer Matthew Polk in his pristine lab coat. The audiophile cynic responds: How can these speakers be any good? But Matthew Polk shouldn't be criticized for sponsoring an aggressive marketing and distribution campaign? It certainly seems to have worked; the name recognition of his company among the general public seems to be a great deal higher than that of many companies listed in Stereophile's "Recommended Components." As it had been nearly two decades since I'd critically listened to a Polk design, I jumped at the chance to audition their entry in the Bob Reina Search for Speaker Nirvana at Cheapskate Prices: the $320/pair RT25i. Description The RT25i, one model up from the least expensive Polk speaker, is a two-way bookshelf satellite sporting a 1" trilaminate polymer-dome tweeter and a 5½" mineral-loaded polymer/composite-cone woofer, both drivers shielded for home-theater applications. The woofer was designed using Polk's Dynamic Balance technology, which employs heterodyning laser-interferometer analysis to minimize resonances. The rear-ported enclosure uses Polk's unique Power Port technology, which consists of a cone at the mouth of the port and space between the rear of the cabinet and the port cone to maximize efficiency while minimizing port noise, or "chuffing." The cabinet also uses two small ports on the front of the speaker, these tuned to resonate at the same frequency as the cabinet's internal depth resonance. This is intended to minimize coloration resulting from the cabinet's air-space resonance. The RT25i has two interesting features not usually found in a speaker at this price. First, the cabinets are finished in real wood, unlike the vinyl finishes found on most budget speakers. My review pair's maple finish was astonishingly beautiful for the price; I wouldn't be ashamed to have wood that nice on any of the necks in my guitar collection. Second, the aforementioned Power Port doubles as a handy wall-mounting device. I mounted the RT25i's on Celestion Si speaker stands, spiked and filled with sand and lead shot. Although I tried the speakers with their grilles off, I heard the most natural tonal balance when I left the grilles on, despite a slight loss of transparency. Polk's detailed and well-written owner's manual recommends leaving the grilles in place. Listening: The Downside Before I begin to gush about this little speaker, I'll point out the RT25i's two serious shortcomings, both of which are consistent with the design limitations inherent in bookshelf speakers with very small cabinets. The Polk's first serious problem was a lack of dynamic bloom in the bass frequencies during densely modulated passages. When the program material was fairly active and complex, the RT25i's bass performance, although tight, fast, and low in coloration, did not achieve a sense of dynamic bloom—a marked departure from the speaker's lively and wide dynamic capabilities further up the frequency spectrum. The result was that mid- and upper bass sounded confined, compressed, and disconnected dynamically from the rest of the spectrum. This was very noticeable in the normally driving bass guitar in Mighty Sam McClain's "Too Proud" (from Give It Up for Love, AudioQuest XRCD 0012-2), and in the forward, rapid, and deep bass synth lines throughout Sade's Love Deluxe (Epic EK 53178). The latter sounded more akin to some of the mechanical-sounding bass lines on the more antiseptic Kraftwerk albums. This problem was much less severe when the bass instrument stood alone in less complex material, such as the timpani in Kohjiba's Transmigration of the Soul (Festival, Stereophile STPH007-2), and the string bass in George Crumb's Quest (Bridge 9069), both of which sounded natural, tuneful, and dynamic. Like the Alón Petite and the Mission 731i, both of which also have very small cabinets, the Polk's in-room bass extension was impressive—down to the lower 50Hz region—in the two smaller listening rooms I used, but sounded a bit bass-shy in my large primary listening room: realistic down to the upper 50Hz region, audible but unconvincing below that. However, the harmonic accuracy of what bass was produced was sufficiently convincing that the organ pedals in John Rutter's Requiem (Reference Recordings RR57-CD) seemed natural, even though the lowest notes were missing in action. The RT25i's second serious shortcoming was severe dynamic compression during densely modulated passages. Orchestrally dense works such as Messiaen's Turangalîla Symphony (André Previn, EMI SLS 5117) seemed flat and lacked vibrancy in the more demanding and cacophonous passages. Similarly, the title track from Hole's rock blockbuster, Celebrity Skin (Geffen DGC-25164), sounded as compressed as an FM broadcast of this familiar tune. However, on "Use Once and Destroy" from the same album, the shifting textures of closely miked vocals, acoustic guitars, timpani, and synthesizers kicked ass as the quieter passages gave the Polk a chance to breathe. Equally convincing were highly varied chamber works (the aforementioned Kohjiba track) and orchestral works such as Penderecki's Symphony (EMI EMD 5507), a blockbuster whose dramatic use of space, dynamics, decay, and the subtle as well as cacophonous use of strings as percussion, shone on the Polks.
I am spending only so much ink on these two shortcomings because the RT25i's combination of strengths exceeded by a wide margin the performance of any speaker I've heard under $1000/pair, and are more likely to be found on speakers costing much more than that.
Listening: The Upside
Here, in a nutshell, is what the Polk RT25i did well: linear and organic low-level dynamic resolution, as in live music; superlative resolution of inner detail; on good recordings, a highly accurate depiction of room ambience; extremely flat but natural reproduction of transient articulation; and extraordinarily uncolored tonal balance from the midbass to infinity and beyond.
The RT25i's reproduction of vocals was to die for, due to the speaker's superlative timbral and dynamic performance and its resolution of detail in the all-critical midrange. I'd never heard Janis Ian (Breaking Silence, Analogue Productions CAPP 027) or Mighty Sam McClain sound more natural, and the angelic integration of Crosby, Stills & Nash's voices on "Guinnevere" (Crosby, Stills & Nash, Atlantic/Classic SD 8229) floated in three-dimensional space, each vocal line easy to follow individually. The dynamic and delicate articulation of well-recorded percussion instruments, from mallets to snares on both classical and jazz recordings (Miles Davis, Kind of Blue, Columbia/Classic CS 8163, 45rpm, and the Kohjiba and Crumb recordings), made the Polks seem to disappear entirely. Kind of Blue and Ian's "Some People's Lives" showcased the warm, rich, articulate reproduction of piano timbres as convincingly as I've heard from any speaker under $2000.
Soundstaging reproduction was beyond reproach, with the three-dimensional image of each instrument in Stravinsky's The Firebird (Mercury Living Presence/Classic SR 90226) reproduced on a wide, deep, ambient stage. In fact, the Polks' imaging specificity was so precise that, even with the speakers spread fairly far apart in my home theater, the central dialogue image was tightly focused on the screen. It made me wonder if, when these speakers are properly positioned, a center-channel speaker is even necessary.
Despite my Hole comments above, most rock'n'roll recordings boogied tunefully and dynamically through the Polks. The hard-driving "Rock and Roll," from Led Zeppelin's fourth album (Atlantic/Classic SD 7208), dug up my toe-tapping memories of the first time I saw this band perform the tune in concert, back in the Mesozoic era.
For me, the acid test of a speaker's realism is to play a minimally orchestrated piece of music, listen from the next room, and see if I can fool myself into thinking that there are actual musicians performing live in the first room. While working on my computer in the den, two rooms away from the listening room, I spun Joni Mitchell's "Urge for Going" (Hits, Reprise 46326-2). The Polk passed the test with flying colors; I found the realism of Joni's voice and guitar accompaniment so distracting that it was difficult to concentrate at the computer keyboard.
Wipe that spittle off that lab coat and talk about the competition
I skipped the budget speakers and first compared the Polk RT25i to my $1000/pair reference, the Alón Petite. The Alón's high-frequency reproduction was more refined, detailed, and articulate than the Polk's, but the Polk's midrange reproduction, in terms of timbral accuracy and detail resolution, was damn close. The mid- and upper bass also bloomed more naturally in the Alón, and the more expensive speaker was superior in its subtle reproduction of low-level dynamic gradations.
The direct price comparison, the now-discontinued $300/pair Mission 731i—my entry-level reference—was darker and more opaque than the Polk, its bass reproduction a little warmer and looser but with more natural dynamic bloom. Although the Mission was balanced tonally, it shared the Polk's high-level dynamic constrictions and large-room/lower-bass definition limitations.
The Paradigm Reference/20 ($600/pair) was the only speaker in the group able to re-create realistic high-level dynamics and bass extension below 50Hz in my large room. Its high frequencies were a bit less natural than the Polk's and its midrange a little more laid-back. The Polk, however, seemed superior in the resolution of inner detail in the midrange. Finally, the Reference/20's lower-midrange/upper-bass region was the warmest of the group, and was most noticeable on piano recordings.
And my new entry-level reference speaker is...
The Polk RT25i has set a new benchmark for what an entry-level speaker can accomplish in many areas. Given its price and diminutive size, its few weaknesses are forgivable. It is far superior to any speaker I've heard for less than $500/pair, and has become my favorite speaker for under $1000/pair. I plan to purchase this pair for use as monitors in my home computer recording studio.
I recommend the Polk RT25i to anyone considering buying a speaker of moderate price and size. I recommend it even to audiophiles used to more expensive wares, just so they can see how much speaker 320 of today's bucks can buy. I've never been more impressed by an inexpensive loudspeaker.
Sidebar 1: Specifications
Description: Two-way, reflex-loaded bookshelf loudspeaker. Drive-units: 1" trilaminate polymer-dome tweeter, 5½" mineral-loaded polymer/composite-cone woofer. Crossover frequency and slope: 3kHz, second-order with Mylar HF bypass cap. Frequency range: 50-26Hz. Frequency response: 60Hz-25kHz, -3dB. Sensitivity: 89dB/W/m. Recommended Amplifier Power: 20-100Wpc.
Dimensions: 11 1/8" H by 6 5/8" W by 10 3/8" D. Shipping weight: 28 lbs (pair).
Finishes: Maple, natural cherry, black oak (real wood veneer).
Serial numbers of units reviewed: 00727 & 8.
Price: $319.90/pair. Approximate number of dealers: 200.
Manufacturer: Polk Audio, 5601 Metro Drive, Baltimore, MD 21215. Tel: (800) 377-7655. Fax: (410) 358-2870. Web: www.polkaudio.com.
Sidebar 2: Associated Equipment
Analog source: VPI TNT IV turntable, Immedia tonearm, Koetsu Urushi cartridge; Rega Planar 3 turntable, Syrinx PU-3 tonearm, Clearaudio Aurum Beta cartridge.
Digital source: California Audio Labs Icon Mk.II Power Boss and Creek CD53 Mk.II CD players
.Preamplification: Vendetta Research SCP-2D phono stage, Audible Illusions Modulus L1 line stage.
Power amplifier: Audio Research VT100 Mk.II.
Integrated amplifiers: Creek 5350SE, JoLida JD-101A.
Cables: Interconnect: MIT MI-350 CVTwin Terminator, MI-330SG, Terminator 2. Speaker: Acarian Systems Black Orpheus.
Accessories: Various by VPI, Simply Physics, Bright Star, ASC, Sound Anchor.—Robert J. Reina
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