Scientific Fidelity Tesla loudspeaker

Foreword by Sam Tellig: I wanted to like the Sci Fi Teslas. I originally heard these speakers at Dave Wolf's store in New Canaan, Connecticut—no longer in business, alas.

To say that the Teslas imaged like gangbusters would be an understatement. These speakers disappeared—particularly when used with a great tube amplifier, like the VAC PA90. With the VAC amps, the music just hung there, suspended in space. So what if the upper midrange was a little scratchy? So what if dynamics were somewhat limited and the bass was—well, not all there? These speakers were doing some amazing things.

They continued to do amazing things when I got my first pair. I had the pair of VAC PA90 amps on loan at the time, outfitted with Golden Dragon EL34 output tubes. True, I couldn't coax deep bass out of these speakers—but I'd had trouble with other speakers, too. Yes, the upper bass boomed a little—but perhaps I could live with that. More troubling, there was something metallic about the tweeter. But the soundstaging was spectacular. And the imaging, too—the placement of instrumentalists within that stage. What a sense of air...or space.

I heard that the speakers would undergo some changes.

"Good," I thought. "Maybe they'll tighten up the bass and smooth out the stop end."

Too bad a later pair didn't live up to my expectations. Work had been done on the speakers, all right. But I thought that the sound was worse, not better. It seemed as if the top end had been lopped off, while the upper midrange still had a touch of metallic stridency. (Most of my listening this time was with the Krell KSA-150—not so lush as a tube amp, but not an amp that anyone would ever accuse of being strident. The sound should have been swell with the Krell. It wasn't.)

And the bass? I still didn't hear any deep bass—but that could have been because my room doesn't allow it. The upper bass was still boomy, and I could not cure this by shoving different foam and sponge materials up the—ah, up the ports of the speakers, as instructed by Dave Wolf. Shoving anything up the ports made the speakers sound constipated.

I was disappointed—and so, too, was my friend, Ritch, who bought a pair and who more or less agreed with my assessment. For me, even the soundstaging and imaging weren't so great on the later pair of speakers—and I did briefly try a tube amp: the Music Reference RM-9.

Obviously, I can't recommend these speakers...yet. On the other hand, I can't dismiss them either. My first listening experiences with two early pairs of these speakers (at Dave Wolf's store and then in my own listening room, heard on VAC tube amps) were great listening experiences. Many times, the sound just hung there suspended in space, as my jaw dropped.

At $1990/pair, I could live with some sonic limitations in order to get that palpable soundstaging and imaging. I could live with a lack of low bass. But I can't live with a boomy upper bass, and I don't want to hear a scratchy midrange—I'm too used to speakers such as the Spendor S100, the Celestion SL700, and the Thiel CS2.2.—Sam Tellig

"Cuz Oi Di'I' Moiiiiiii Whyyyyyyyyyy!—Corey Greenberg"
Sid Vicious should have been a speaker designer. Not because he was a bass player, like Spica's John Bau and Epos's Robin Marshall. And not because he couldn't play the bass, like Quad's Peter Walker (footnote 1) and KEF's Raymond Cooke. Not even because he wore chains around his neck and carved his name onto his chest with razor blades, like...well...maybe the boys at GinS are into that stuff. No, Sid should've been a speaker designer for one reason: he did it HIS whyyy.

This idea pounded itself home after I took part in judging A&S Speakers' third annual "Sound-Off" amateur speaker contest this past October (footnote 2). Confronted with 16 home-brew speakers of wildly varying character, it became obvious that all men's ears are not created equal; some like it hot, and some like their metal-dome tweeters redlining across the Desert Flats like benny-dancing Road Runners. I went into the contest expecting to hear, more or less, slight variations on the same basically neutral theme; how hard could it be to design a decent-sounding speaker these days, what with all the super-drivers and CALSOD-XOPT-SPO-DEE-O whiz-bang design software available to the modern designer?

And the answer IS...very!

For starters, you need a reference, and I don't mean live, unamplified classical music, gramps. 'Cause I don't mean a sonic reference, I mean a reference system with which you evaluate/design/tweak your speaker into shape. And even better, several reference systems, to uncover potential matching problems/synergy with certain types of gear. The Infinity IRSes are a good example of this: designed with ARC tube amps, it's generally accepted that they absolutely positively MUST be used with tubes on the top. Solid-state amps, even the liquid and the lush, are unusable with the big IRS's tweeter panels. The opposite is true of many of the Apogees; to get the best overall sound out of the Stages, for instance, solid-state's the way to go, Classé DR-8s in particular.

So when a salesman tells you that a certain speaker "likes tubes," he's not talking about Mr. Speaker hanging around the Gold Dragon bus station in a dirty raincoat; it's a fact that a speaker's impedance curve reacts with an amplifier's output impedance, resulting in audible peaks and dips in the system's frequency response. So a speaker designed for the most accurate response with a tube amp may well sound lifeless and hard with solid-state, while a speaker optimized for solid-state might become too soft and mushy-assed with tubes. The point is, speaker designers need to audition their prototypes on as many different systems as they can, to make sure they're not building a speaker that will only sound its best with one particular combination; ie, theirs.

Ask me no questions, I'll Tesla no lies
The Scientific Fidelity Teslas are beautiful, distinctive-looking speakers that would look at home in the most outré art galleries; the vaguely phallic profile, with its rounded ends and protruding "hooded" fascia, is in stark contrast with the sharp lines and rectangular cabinetry of most speakers. The cabinet's rounded tush sits firmly in a pair of wooden support-bases, which accept leveling spikes to mass-couple the Teslas to the floor.

The Tesla's drivers, two 6.5" bass-midranges and a 1" Vifa aluminum-dome tweeter, are vertically positioned on the upper half of the cabinet in that hotter-than-hot, knocking 'em dead on every runway from Paris to Milan "D'Appolito" woofer-tweeter-woofer configuration. Sci-Fi calls this "SWFT," for Single Wave-Front Technology, explaining that when two bass-midrange drivers are used in this sandwich-type design, they act as a single acoustic point source as long as the wavelength is larger than the distance between the two drivers, which it is. Designer Michael Maloney—who, incidentally, has been professionally involved with loudspeakers for almost a decade—claims that using very sharp crossover slopes forces the acoustic "size" of this point source to shrink to the size of the centrally mounted tweeter above the 1kHz crossover point, resulting in a "quasi–single-point source." The Tesla crossover features a 12dB/octave low-pass slope for the bass-midranges and a 24dB/octave high-pass slope for the tweeter, with RelCap polypropylene caps used throughout. The two bass-midrange drivers are wired with 14ga stranded copper wire, while the Vifa tweeter is connected with AudioQuest F-14 speaker cable.

The Tesla's bass-midrange drivers are an in-house design, with cones made of woven carbon fiber soaked in a high-strength resin and pressed into shape. What looks like a pointed metal dustcap is actually the extended aluminum pole-piece: fixed to the magnet assembly, this nosecone stays in place while the driver moves back and forth around it. The driver's surround is made of Norsorex, a high-loss material claimed to be effective at damping the cone's high-frequency breakup modes. The Tesla features a bass-reflex alignment, with a rear-firing port filled with a removable resistive plug of multi-cell foam. I found that in my room, removing the plugs was like deflating a monster truck tire; as the Teslas need every bit of control in the bass they can get, I left the plugs in.



Footnote 1: PJ does play the flute, though.—John Atkinson

Footnote 2: See Vol.15 No.3, March 1992, pp.146–158.—Corey Greenberg

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