Immedia RPM2 turntable Page 2

In fact, the two parts of the bearing proper, as well as the spindle and the platter, must all be machined at the same time. Most bearings are simple devices, consisting of a spindle and a cup—or some variation on that theme. The RPM's bearing has two cups, one of which is attached to the platter and fits down over the bearing well, rotating around it. This outer cup contains a downthrust spindle that fits into the bearing well inside the inner cup. The bearing well has a wedge-shaped bottom, into which is fitted a steel ball. A sapphire disc sits atop the ball, acting as the bearing. The downthrust spindle rests upon the sapphire disc, thus supporting the platter. The point where spindle and disc meet is also the rotational point at which the belt drives the platter. Bronze sleeves separate the inner and outer portions of the bearing above and below the point of rotation.

Perkins likens the effect to that of multiple pulleys or multiple motors, and claims that this creates a low-noise bearing with steady rotation.

What drives it?
The last—or perhaps, from Perkins' view, the first—unique component of the RPM2 is his approach to the controller and motor, which he views as a single unit. The motor is a 12V DC motor with a lot of torque. "A lot of turntable designers go for a less torquey motor and then run the platter with dental floss—that's a very lossy system (footnote 2). I don't want the drag of the stylus in the groove to have any effect on rotational speed. If it were quiet enough, quite honestly, I'd prefer chain drive! I don't care how much mass you have in a passive system, there will still be deceleration, so I believe in using a motor that can constantly accelerate against the drag."

The heart of the drive system is an analog sinewave generator. "It doesn't have a digital or a crystal chip in it. It allows me to adjust amplitude, frequency, and phase. Most manufacturers like AC motors because you can lock them into a sinewave. I wouldn't have any problem locking into the 60Hz component of 110, except that power companies average that 60Hz wave over the period of a month! That's not very accurate—at least not accurate enough to ensure 33 1/3rpm repeatedly. But more than that, I don't think that wall current is all that clean, so I'd rather be isolated from it.

"We create our own sinewave, which is incredibly clean compared to what we'd get from the wall. We set our frequency and amplitude for maximum torque at 33 1/3, which means it's slightly lower at 45, but the platter makes up for the difference.

"The other thing about the chip we use is that it allows us to adjust phase. There is a point when a motor is rotating where it goes between the magnetic fields of the coil and the magnet. The coil's polarity flips and it jerks the magnet through to the next spot. We changed the phase angle enough to smooth the transition. We reduced the noise from the motor by a considerable margin."

A synthesis of experience
I'm sure glad there are people out there who are content to design turntables. When I sat down with my drink and considered the whole question of turntableness, I didn't get much further than "It should have a platter that turns around." To design a high-end turntable from scratch requires a mindset that can see the big picture and obsess about screw-thread sizes.

But give me a turntable and I certainly know what to do with it. You play records. A lot of them. So I did.

An Immedia turntable is essentially a bespoke item. Since it doesn't have a removable armboard, you must order it drilled for a specific tonearm. My review sample came drilled for two different arms: Immedia's own RPM-2 arm and my long-term reference, the Naim ARO. Setup with either arm was a snap—no springs to balance, remember?

From the instant I set the 'table up with the ARO, I suspected that Allen Perkins must be a drummer (I later found out that he is)—this 'table has a way with rhythm and pace that is impossible not to notice. Choose any track that relies on subtle timing to work and clamp it onto the RPM2. Whoowee, it'll sound so fine.

One reason I've stood by my Linn all these years is that it gets pacing and timing so right. I've heard other turntables that may have greater bass extension, or that extract more holographic soundstaging from the grooves, but at day's end they just don't boogie. The RPM does, however.

When I listen to CDs for a long period, I tend to forget the special way that good turntables have of portraying rhythm as a living thing that surges and pulses and breathes. Good timekeeping is not merely steadiness, but a means of marking time and possessing it. The best CD players can extract some degree of this quality, but to really know it, you still need to listen to a good turntable. I haven't heard anything that gets it righter than the RPM2.

There a moment in "All I Need is the Girl," on Francis A. & Edward K. (Reprise 1024), where Frank Sinatra comes in after the break, driving the vocal line across the riffing of Duke Ellington's band. On some 'tables, his voice is obscured by the band. On very good 'tables it is a thing apart, easily distinguished in the mix. On the best 'tables, not only is his voice quite separate from the instruments, but his rhythmic line is revealed to be in spectacular counterpoint to the one pursued by the orchestra. On the RPM2, all of that was manifest to the point where I decided that anyone with that deep a comprehension of time deserves enshrinement at Greenwich.

But the RPM2 has much more going for it than great timing. Images are incredibly stable, which does indeed mean that the soundstage is huge—not to mention filled with detail. Classic's new reissue of Hi-Fi a la Espanola (Mercury Living Presence/Classic SR90144) really kicked some audio butt. Bass was deep and the dynamics were spectacular, but as I listened I kept muttering, "It's so big, it's sooo biiig." And it was.

"But," I hear some audiophiles objecting, "what about the lack of a suspension?" Well, first, the RPM doesn't lack a suspension—it uses mass and compliant material to replace a conventional sprung suspension. The presence of springs does not guarantee isolation from external vibration. When I lived in a prewar Brooklyn apartment, the suspended wooden floors interacted very unfavorably with my LP12. Footfalls would set the springs in motion, and once the subassembly started moving, it seemed as if the springs actually amplified vibrations at certain frequencies. I solved that problem by buying a wall-mounted stand which, when attached to a load-bearing wall, never moved at all—and allowed the Linn's suspension to do its job.

These days I live in a house floored with a poured cement slab. My Linn is happy on a floorstand, and so was the RPM2. Mounted on a classic Sound Organisation stand, it never skipped, fed back, or acted as a microphone. I had no problem with the suspension at all.

However, some users may find that they do. I might've in my old place. Perkins points out that there are many after-market supports, such as the Bright Star stands or Simms air-tables, that should solve any problems that come up.

How does the Immedia stack up against the competition? Pretty darn well, thank you very much. Comparing my LP12/Armageddon to the RPM2 using the ARO arm and van den Hul Grasshopper, I felt they were fairly well matched in terms of pace, but that the Scots 'table did not reach quite so low in the deep bass. (I'd come to a similar conclusion when comparing my Linn to John Atkinson's, which sports a Lingo power supply, so don't take this as definitive.)

I also had a VPI TNT III, fitted with Immedia's laminated armboard cut for the RPM arm; I compared the two using that arm and a Lyra Clavis D cartridge. The VPI is a low-end champ, but I felt the two 'tables were fairly well matched in bass extension. The Immedia seemed to swing with greater ease, however. On the other hand, the TNT had an engaging presentation that made the RPM2 sound a tad more aggressive. Call it a draw.

I also put the Well Tempered Reference Turntable into the system, but direct comparison there was impossible, since the WTRT can use only its own arm. Even so, it was a close race. Again, I was astounded by the Immedia's lively rhythmic presentation, which I find hard to resist. Like the VPI, the Well Tempered sounded tonally mellow compared to the RPM2. I don't mean to imply that the RPM has an edge—to my ear, it doesn't. It's possible, I suppose, that the acrylic platters on the other two 'tables have consistent sounds of their own.

Disappointed that each of these 'tables has its own strengths? You shouldn't be—nor should you be surprised. They all inhabit Class A in Stereophile's "Recommended Components," and each represents an enormous amount of thought and hard work. But the Immedia RPM2 has proven—to me, at any rate—that it belongs there too.

So what does a high-end turntable look like? Well, I never came up with a definitive answer to that one. But it must certainly be imbued with that quality of turntableness. It must spin the record steadily, shield it from the noise inherent in the environment, and work reliably. Now that I've had the Immedia RPM2 in my system, it's begun to personify those qualities for me. These days, a turntable looks mighty like Immedia's little jewel. If you're looking for a world-class turntable, you need to add it to your list of contenders. It's a good 'un.

Footnote 2: Again a filter action is required to reduce the amount of motor noise that gets through to the stylus/groove interface. With belt-drive designs, this is provided by the belt compliance working in conjunction with the rotating mass—the platter's moment of inertia. By adding resistive damping as in the RPM2, this low-pass filtering action can be fine-tuned.—John Atkinson
1101 Eighth Street, Suite 210
Berkeley, CA 94710
(510) 559-2050
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