PMC IB2i Loudspeakers
- Created on Wednesday, 01 May 2013 00:00
- Written by Aron Garrecht
In June 2012, SoundStage! Network publisher Doug Schneider reviewed the PMC twenty.24, the flagship of the British company’s twenty line. Not long after completing his review, Doug told me how impressed he was with the twenty.24, noting that it displayed a remarkable midrange purity, and impressive bass extension for such a modestly sized floorstander. He then asked if I’d be interested in reviewing the IB2i, the smallest three-way studio monitor in PMC’s flagship “i” series. I responded immediately: “Absolutely!”
There were several reasons for my enthusiasm. First, I’d never reviewed so large a stand-mounted speaker, let alone one that’s a transmission-line design and costs $21,999 USD per pair. Second, if the IB2i proved even half as impressive as Doug found the twenty.24, I was in for an ear-opening experience. I was put in contact with David Callam, national product manager for PMC’s Canadian distributor, Precor. Callam proved invaluable throughout the review period, patiently answering my myriad questions and providing an abundance of information. But informative as he was, I was still unprepared for the surprises the IB2i had in store for me.
Behind the veneer
The first surprise was a pleasant one, and happened as soon as I opened the double-boxed packaging of my amber-stained Cherry review samples -- I was greeted with wafts of freshly finished wood. This put a grin on my face; being somewhat of a junior-level woodworker, I’ve always loved that smell. More than that, it implied that I was in the presence of a high-quality product.
The IB2i is available in four finishes: Oak, Walnut, Black Ash, and Cherry. Each speaker weighs just over 90 pounds and measures 29.1"H x 13.0"W x 18.3"D -- a pair of them takes up some real estate. It seemed odd to me that a speaker of this mass and these dimensions would not automatically be shipped with dedicated stands, so I called Callam to see if they’d gone missing in shipping. He told me that PMC offers a choice of 14”- or 33”-high aluminum stands that, they claim, are sonically tuned for the IB2i and respectively cost $2449 and $2699/pair. This turned out to be my only real gripe about the IB2i -- a speaker of this weight and size can’t just sit, unsecured, on a standard speaker stand with any degree of confidence or safety. The bottom panel includes no provisions for feet, so placing an IB2i on anything other than its dedicated stands risks damage to the finish of both the speaker and the surface it’s placed on. Furthermore, because the IB2i’s drivers have such large magnets, by far the bulk of the speaker’s weight is concentrated in the first 5” of its depth. This makes it very front-heavy, and difficult to place on anything other than the recommended stand. Luckily, I was able to build, in my wood shop, a pair of stands based on the 14”-high design, but most buyers won’t have this option.
The stands built, my frustration alleviated, and the IB2i’s properly positioned in my room, I let them burn in for a few weeks before doing any serious listening. During that time I learned about the extensive technology hidden inside these modest-looking speakers, and began to understand that PMC designs its speakers to be far more than the sums of their parts. To get a full understanding of how the IB2i works, I began by studying the cabinet design, which is based on what PMC calls Advanced Transmission Line (ATL) technology. A variation on the well-established transmission-line technology, ATL uses sophisticated cabinet construction and patented materials optimized to absorb specific frequencies emanating from the back of each drive unit.
It’s no easy task to design a speaker that simultaneously utilizes cabinet construction, absorption materials, and driver characteristics to a point where one specifically relies on another to optimally reproduce music. The process begins with software modeling, developed in-house through years of designing ATL speakers, that helps calculate the transition line’s length, shape, and number of turns, as well as the properties and placement of the damping materials (an ATL speaker may have materials of up to four different damping densities and profiles). Once these properties have been determined, PMC uses hard grafting to create different prototype cabinets with movable baffles and foam formulas of slightly different properties. After an optimal balance of these properties has been attained, measurements are performed, followed by lengthy listening sessions to fine-tune the end result.
The cabinets are assembled by hand in the UK using CNC-cut panels of Medite HDF. All finishing is also done by hand, and PMC finishes the inside and outside of each cabinet. I asked Callam why this is done. “PMC calls it balancing. If you prepare both sides of the cabinet, it remains stable over time without any degradation of the cabinet. Another way to look at it would be, if you lick a stamp, it curls when moisture is applied. The same can happen over time when you apply veneer to HDF/wood.”
Callam said something else of interest. After the transmission line has been built and the damping installed, very little air space is left inside most PMC speakers. In the case of the IB2i, 75% of its transmission-line volume is filled with foam materials designed to absorb all the upper frequencies that radiate from the back of the single bass driver. With such a high backpressure, PMC had to design a driver strong and rigid enough to “drive” the air behind it through the line. They developed a 10”-diameter, flat-piston driver made from two discs of thin carbon fiber sandwiching a layer of honeycombed Nomex. Behind this sandwich is a 3” voice-coil with a huge, vented magnet assembly. To move enough air, however, this driver must have an unusually long excursion. This prompted PMC to design an all-new, oversize roll surround that can be found on the IB2i’s 10” piston as well as on the 12” and 15” drivers of its larger brethren.
The result of this design is that frequencies as low as 25Hz remain in phase while emerging from the large vent at the end of the IB2i’s 8’-long transmission line, which essentially acts as a second driver. Because the air pressure loading the main driver is maintained, additional control of the driver is also provided over a wider frequency range, which in turn significantly reduces distortion. Additionally, the lack of distortion afforded by this level of control ensures that upper-bass and midrange detail are not masked by harmonic distortion in the very low frequencies.
The IB2i’s midrange driver, responsible for reproducing frequencies between 380Hz and 3.8kHz, is also used in PMC’s MB2, MB2XBDi, and BB5 models. It’s made entirely by hand by PMC, who claim that it has the lowest distortion and the highest efficiency of any 3” midrange dome made anywhere in the world. Its 3” (75mm) coil is hand wound, then cured in an oven for 45 minutes at 240°. The dome itself is of pure linen, doped with a liquid said to remain highly flexible throughout its lifespan. PMC claims that it takes their average worker six months to learn how to properly apply the dope. This is because the precise distribution, speed of application, and thickness of dope on the surface of the dome all greatly affect the sound; the dope is applied with a very fine brush as the dome rotates on a turntable with a precision bearing to ensure even distribution. The dome, coils, and suspension are then glued together, followed by the incredibly heavy magnet, pole piece, surround, and cast-aluminum flange assembly. Completely assembled, the driver weighs an impressive 22 pounds. Its performance is enhanced by many things; two of particular note are a pure copper cap that PMC fits to the pole piece, which helps focus magnetic flux back into the gap, thereby increasing the efficiency. Another is an absorbent material that fills the volume of the dome and helps damp internal resonances. The driver is then magnetized using a huge coil and oversized reservoir capacitors, followed by testing and measurements.
Directly above the midrange dome is a driver that PMC is especially proud of: their PMC/SEAS 1” (27mm) soft-dome tweeter. Like the midrange, the tweeter is shared throughout the entire IB, MB, and BB models. Constructed using a consistent pre-coated material, Sonolex, that is very resistant to variations in humidity and temperature, the tweeter is cooled with ferrofluid. PMC states that tweeters coated after they are formed have slight variations in the thickness of the coating, which inevitably results in variations in their frequency response, and that their pre-coating method maintains consistency over multiple batches of drivers.
To ensure that all of their drivers respond as accurately and as smoothly as possible, PMC uses sophisticated, low-distortion crossovers with steep rolloffs. The idea is that if a driver operates only within the bandwidth within which its operation is linear -- i.e., the region in which it responds without distortion -- its performance and power handling can be optimized and therefore its sound quality improved. To achieve this, PMC employs 24dB/octave Linkwitz-Riley crossover networks built on circuit boards of military-grade fiberglass. These boards are baked with extra-thick traces of pure copper aligned for optimal signal paths and current capabilities. Each network board comprises 31 components, selected and measured by hand. Altogether, the IB2i has a frequency response of 25Hz-25kHz, a sensitivity of 89dB/W/m, a nominal impedance of 4 ohms, and can handle amplification from 180W all the way up to 900W.
The IB2i’s three pairs of terminals accept both spade and banana connectors and are configurable for triwiring or triamping. A jumper bar is provided should you want to run a single lead, as I did for this review. The fabric grille could use some improvement; it provides minimal protection for the drivers, and connects via flimsy plastic plugs uncharacteristic of a speaker in this price category. I left them off for the duration of this review.
As of December 2012, PMC offers Special Editions (SE) of three of their models, including the IB2i. At time of writing, the price had not yet been set for the IB2 SE, but was expected to be “around” $28,500/pair. The Special Editions offer new internal bracing, a computer-modeled dispersion surround for the midrange dome that’s machined from a solid billet of aluminum, and all-new, British-made binding posts with jumper bars on an updated terminal panel. Additionally, all SE drive units have a new, soft-feel Nextel coating, and the Special Editions include custom-designed, specially tuned stands, knurled spikes (both of the latter are included with SE models), and are available in two more finishes: Rose Macassar and Rich Macassar.
The IB2i is so darn big that I wondered if it would sound more like a full-range floorstander than a minimonitor. I got the answer in the first few minutes of my first listening session: every bit as full-range as a comparably sized floorstander. The kicker -- and this was where some of the brilliance of Peter Thomas, PMC’s chief designer, became apparent -- was that they imaged like narrow-baffled bookshelf speakers. Listening to the first few minutes of the remastering of Pink Floyd’s “Wish You Were Here,” from their Discovery Collection (CD, EMI 028945 2), I heard the most tangible, well-textured, articulate acoustic guitar I have ever heard in my room. Image focus, string detail, and soundstage placement were jaw-droppingly good, and the realism afforded by all of these characteristics coming together was something I hadn’t heard before from any speaker.
After listening to “Wish You Were Here” I don’t know how many times, I moved on to “Tin Pan Alley,” from Stevie Ray Vaughan’s The Essential Collection (CD, Epic/Legacy TV2K 86423). I rarely come across speakers that can handle up to 900W of power, and wanted to hear if the IB2i could convert this electrical energy into sonic energy relative to their sensitivity, or if they’d be harder to drive because of how difficult it is to move the air inside the ATL, and how massive the midrange driver’s magnet is. Listening to “Tin Pan Alley” told me that PMC’s claim of a sensitivity of 89dB may be a bit optimistic. My reference B&W 802 Diamonds are specced at 90dB; to get the same sound levels from the IB2i’s in my room, I had to raise the volume on my Classé CP-800 preamp six full steps. That addressed, Vaughan’s electric guitar and voice sounded clean, neutral, highly dynamic, and very “in the room.” I could easily hear pick slides as the IB2i’s struck a fine balance between illustrating detail and maintaining liquidity. Tommy Shannon’s bass sounded rich, forceful, and seductively deep, which explained the speaker’s size. The IB2i is so big because its ATL needs to have enough volume to provide controlled, natural-sounding bass down to 25Hz. It’s one thing to read this spec; it was something else to actually experience it from a speaker smaller and with fewer drivers than the B&W 802 Diamond.
Track after track, the IB2i’s continued to impress me with their holistic imaging, midrange purity, and uncanny bass reproduction. Even more impressive, they did this regardless of volume level -- PMC’s ATL seemed to be equally effective at delivering the appropriate amount of bass at volume levels high or low. But if there’s one place where neutrality, tonality, and driver integration most need to come together, it’s in the reproduction of the sound of the acoustic piano. I cued up “Melodia Africana,” from pianist Ludovico Einaudi’s I Giorni (CD, BMG 97462 2). Notes floated in the air effortlessly, with excellent tonal purity and fluidity, yet despite their delicacy, also had weight and bite when they needed to. Listening to this and several other tracks of this album, I came to appreciate how well PMC’s steeply sloped crossover network works -- there was absolutely no showcasing of drivers going on. The tweeter had ample resolution to reproduce foot taps, there was wonderful immediacy in midrange notes, and the bass piston made the lower octaves always present without ever drawing attention to themselves. It was also obvious that designer Thomas spent a lot of time and money perfecting the IB2i’s midrange -- it was the best I’ve ever heard.
A word commonly used in audio reviews to describe a product’s sound is musical, a term that can mean different things to different people, depending on the listener’s sonic and musical preferences. For me, musical means realistic, and in that regard I find the IB2i to be tremendously musical speakers. In virtually every test I put them through, the IB2i’s were sonically superior to my reference B&W 802 Diamonds ($15,000/pair). Listening to Pink Floyd’s “Wish You Were Here,” I found the B&Ws quite good, showcasing levels of detail and focus similar to the PMCs’, but they were no match for the PMCs in terms of midrange neutrality, textural accuracy, and tonal purity. The results were similar with Vaughan’s “Tin Pan Alley”: while the IB2i’s demanded more power to produce the same volume level as the 802 Diamonds, the B&Ws couldn’t touch the PMCs in bass definition, extension, or volume. As well, when listening to Lara Ruggles’s “Snowflake,” from Sony’s AR1 SACD sampler, I noted that, while on a par with the B&Ws dynamically, the PMCs excelled at making Ruggles’s voice come alive in front of me, allowing me to picture her at the piano, the double bass solidly illustrated to the right, and the 3D-like presence of the drums and cymbals far back on center stage. Soundstage parameters were clearly outlined. The B&Ws give a great impression of what’s happening onstage; the PMC IB2i’s brought what’s happening onstage to life.
Any reference speaker I might consider buying in this price range must meet three criteria. First, it needs to sound as good as, if not better than, the competition. Second, it needs to offer decent value considering its performance. Third, they need to look good.
After living with PMC’s IB2i speakers for a few months, I found myself reconsidering this approach -- I began to realize that my criteria are not equally weighted. For example, I find the B&W 802 Diamonds more pleasing to look at than the PMCs, but that’s a matter of taste, not a deal breaker. I struggle a bit to see precisely what my $21,999 might be buying in the PMCs when I consider the exotic materials and elaborate construction of the B&Ws -- but the IB2i comes with an astounding 20-year warranty, which says much about their build quality.
What the IB2i made clear is that, as always, sound is paramount, and when it came to sound, PMC’s IB2i is a beguilingly good-sounding speaker that I found difficult to stop listening to. Night after night, the pair of them had me leaving my B&Ws in the spare room while I sat listening with a grin on my face. The integration of the drivers’ outputs was so good that they reminded me of the point-source coaxial drivers used in such speaker’s as KEF’s Blade. The quality of bass on tap from PMC’s ATL technology and robust carbon-fiber piston driver working as one is also equal to or better than that of most floorstanding bass-reflex designs I’ve heard in this price range. But the real jewel of the IB2i is its exquisite dome midrange driver -- it provided the most neutral, natural, lifelike midrange I’ve heard in a speaker south of $40,000. If you’re in the market for a reference speaker, minimonitor or floorstanding, I urge you to listen to PMC’s IB2i -- it might be the last speaker you ever buy. Highly recommended.
. . . Aron Garrecht
- Speakers -- B&W 802 Diamond, B&W HTM2D center, B&W CWM 7.4 surrounds (4)
- Subwoofers -- JL Audio Fathom f112 (2)
- Amplifiers -- Classé CA-M600 (2), Classé CA-M300, Halcro MC50
- Preamplifiers -- Marantz AV8801, Classé CP-800
- Sources -- Ayre Acoustics C5xeMP CD player, Oppo BDP-103 universal Blu-ray player
- Cables -- Kimber Kable Select KS-6063 speaker cables and Select 1126 interconnects, Cardas Clear Blue Beyond power cables
- Power conditioner -- Torus Power AVR2 20A
PMC IB2i Loudspeakers
Price: $21,999 USD per pair.
Warranty: 20 years parts and labor.
43-45 Crawley Green Road
Luton LU2 0AA, England
Phone: +44 (0)870-4441044
Fax: +44 (0)870-4441045
The Sound Organisation
159 Leslie Street
Dallas, TX 75207
Phone: (972) 234-0182
Fax: (972) 234-0249
107 Connie Crescent
Concord, Ontario L4K 1L3
Phone: (905) 660-6234
Fax: (905) 660-6145