High Efficiency Speaker Asylum: REVIEW: Supravox 215-2000EXC field-coil driver Speakers by tinos Need speakers that can rock with just one watt? You found da place.

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Model:	215-2000EXC field-coil driver
Category:	Speakers
Suggested Retail Price:	$2480 (pair)
Description:	High efficiency electromagnet full-range driver
Manufacturer URL:	Supravox
Model Picture:	View

Review by tinos ( A ) on March 24, 2004 at 19:43:44 IP Address: 68.162.159.50

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Disclaimer: the product reviwed below is not a complete speaker system but a driver. Systems based on this product is also available from the manufacturer.

I have been a full-range aficionado for more than 20 years. The first set of speakers I owned was Telefunken 6x9’s that came out of my father’s console – I was sixteen. In 20-ltr open-back cabinets, driven by Telefunken 6AR5 single ended tube amplifiers, they were very good indeed. The accidental intoxication of SET / full-range fever at that early age was incurable, spoiling me to the extent that I have not yet experienced similar satisfaction from more ordinary kinds of stereo systems.

Immediately after achieving financial independence, I started my quest for the best full range drivers. The “best,” of course, is to my ears, and those ears are what count in the end. My first love affair was with JBL LE8T’s. Then I moved on to Lowther 6A’s, 7A’s, and original PM6’s of old, in variety of cabinets. Occasionally I tried to divert my taste from Lowthers – Jordan watts, Fostex, Manger, and most recently PHY-HP. They all had their own virtues and did better jobs than Lowther in many ways but none of them could truly satisfy me in the long run. Until recently the most impressive fullrange sound I had heard in my own listening room was from
1) JBL LE8T’s in 3 sq. ft bass reflex cabinets driven by 6B4G single ended amplifiers;
2) Lowther PM7A’s in a modified Acousta back-loaded horn cabinets powered by a pair of Western Electric KS16608-L1 amplifiers;
3) and a pair of Goodmans Axiom 80’s in open-back cabinets paired with Marantz 8B.
LE8T had good tonal balance and nice easy-going character, but with poor sensitivity and lack of refinement. High-frequency extension was also limited. Lowther had very good dynamics, resolution, and high sensitivity, but alas, no real bass in practically feasible cabinets. With certain kind of program materials Lowther’s uneven frequency response was quite noticeable, and sometimes bothersome. Axiom 80’s high and midrange were stunningly beautiful with depth and character, but the bass was a little lean, lacking impact and punch.

My ideal full range driver would have the combined virtues of the above mentioned excellent drivers. It must have reasonably flat response between 50 Hz to 12 KHz in a not-so-humungous enclosure, and a character that combines amicable elegance and dynamism. The sensitivity must be high, around 95 dB per Watt, which is necessary for my 2A3 singles. In short, I have been looking for something very unlikely to be obtained, regardless of price.

After being disappointed by poor high frequency behavior of PHY-HP 8-inchs, my recent interest had been upon field coil drivers. My intimate experience with field coils was limited to Jensen A-12 and an RCA unit (model number uncertain); however, their commonly distinctive quality is vivid in the memory. Their sound was so “easy,” effortless and natural.
I could find two field-coil full range drivers currently in production: Fertin and Supravox, both made in France. Since they both are very expensive drivers I tried quite hard to obtain detailed information before making investment. End-user reviews for both, though not numerous, were very favorable. As it appeared, Fertin was slightly less expensive but did not have a representative in the U. S., while Supravox was readily available from a newly established U. S. distributor, Supravox America. After some lengthy and friendly discussion with Mr. David B. Levinson of Supravox America, I finally decided to try Supravox 215-2000 Excitation drivers. I ordered a pair with a regulated DC power supply made by CIC for excitation. Ordering was hassle free – communication excellent and the delivery fast.

At first I mounted the drivers in my "universal" mass-loaded transmission line, designed using Martin King’s excellent simulation program. I call this cabinet “universal” because it represents an ideal size for my (likely) listening environments, and the alignment broadly fits to typical 8-inch drivers with Qts of 0.4 to 0.5, Vas 60-80Ltr, resonance frequency around 50Hz. The cabinets measure 33.5 inches high, 10.5 inches wide and 15 inches deep. (All dimensions internal) Provisions for mounting various drivers – exchangeable baffle, removable port, and easy access into the cabinet to rearrange the damping material – are also integrated into the design.
Sources were Rega Planet 2000 for CD playback and Kuzma Stabi II / SME 309 / Clearaudio Aurum Beta S setup for vinyl. Amplification was provided by my own design TR preamp and a pair of 60W MOSFET mono amplifiers. These amps are technically up to current hi-fi standard with neutral tone and reliable performance. At least they are as good as decent $3000 commercial units in their objective performance. Nothing fancy or extraordinary but such was the exact reason why I used them. I have another set of amplification, also of my own design, that I use for serious listening (transformer coupled tube preamp and 2A3 single ended) but I do not use them for getting acquainted with new drivers. The tube setup was not intended to be neutral or "able to drive anything" - the transistor system was. Besides, one would not try to break in a new set of drivers with a flea-powered SET amp – it may take forever. Cabling was by Transparent Music Reference series throughout.

The sound of Supravox drivers in the “universal” TL was not satisfying (tuning was obviously way too off), even though I could glimpse what they were possibly capable of. The bass, though weak and uneven due to the mistuning, was forceful and at the same time natural. Midrange was slightly forward as any new drivers but never fatiguing or annoying. High was somewhat ragged and grainy, about which I was assured by Supravox that it would improve over time (it did).
Since Supravox 215-2000 was not happy in a relatively small transmission line, a new design was called for. While trying to design a better enclosure, I mounted the drivers on open baffles, made of 3 ft by 2 ft sheets of 17-ply Baltic birch plywood. They were intended to be only a temporary setup. The Supravox on open baffle was, however, an unexpected revelation. Tonal balance was surprisingly good even though there wasn’t enough bass due to smallish baffle size. Everything except the lowest couple octaves of bass was wonderful. Midrange forwardness was gone, and the bass had the effortless ease, powerful but yet relaxed quality. Male vocal, known for a good test for tonal balance, was reproduced with coherence, elegance and body. If I were only listening small acoustic ensembles, I could live with this humble and simple open baffle for ever.

It was Tchaikovsky symphony no. 6 (RCA living Stereo, Charles Munch conducting Boston Symphony Orchestra, 180g vinyl) that reminded me that I would not be truly satisfied until I get at least down to 50Hz from this capable drivers – which, of course, would not be obtainable from open baffle of such a small size. So I went on to build a new, bigger and sturdier open baffle (see picture). The main baffle, upon which the driver is mounted, is made of the same Baltic birch, 1.5ft by 3.2ft. Wings, made of American pine 1.75ft by 3.2ft each, are attached to both sides of the main baffle. The baffle leans back slightly (about 8 degree) so that the drivers’ axes would point toward the listening position at 10ft distance. The whole assembly is decoupled from the floor by 1”-thick maple base and 0.75”-long steel spikes. (There was a hole above the Supravox driver in provision for mounting a tweeter, but I find the helper tweeter is not needed. It is now blocked as seen in the picture.)
With this baffle, the bass extends to 50Hz flat and begins to roll off from there. There is still audible output at 40Hz. I know – the Qts of the driver at 6.5V excitation is only about 3.6, which would disqualify them for open-baffle configuration. However, as the measurement (done by Clio) indicates, they perform excellently on this baffle. How and why I honestly do not know. All I know is that they work remarkably well. Actually, I had to REDUCE the amount of bass by decupling the baffle from the floor to make the overall balance even.

I have been listening to them for about two month now. These drivers take long time – even by the high efficiency fullrange standard – to break in: they have been getting better and better, and still keep doing so. I am quite certain, though, that I am now familiar enough with them to describe the nature of these fine drivers without being overly biased. Following is a list of their virtues:

1) The tonal balance of Supravox 215-2000EXC is the best so far I have heard from any full range drivers. It is the widest and smoothest, with character, refinement, and elegance. The bass is deep and powerful, notably so for an 8” full range. High-frequency extension is excellent, flat to 10K and down only 4dB at 14 KHz on-axis (my upper hearing limit) without any pronounced peaks; it goes on to 20KHz to hit -10dB line. Timbres are true and free from pronounced coloration. In addition to this lack of "habits," the spectrum of the tonal colors available is rich and wide – their palette has many pigments, so to speak.
2) The drivers are extremely dynamic with "effortless power," which I guess is due to the use of huge electromagnet. (It is difficult to describe this particular quality – one could mentally try to combine the two mutually exclusive qualities: tremendous dynamism and relaxed ease of presentation. A good analogy would be the effortlessness of professional athletes exercising their skills.) They sound BIG, in such a way that well designed horn speakers do, without loosing composure. There are only few fullranges I’d use for listening operas or post-Romantic orchestral pieces, and 215-2000EXC is among the very best in this regard.
3) They are highly sensitive and revealing. Resolution is very good – even during complex, loud passages, there isn’t any noticeable compression or loss of details. Consequently the soundstage is huge and stable, with pinpoint imaging. One of my usual complaints about fullranges is that the soundstage commonly lacks depth and height. With Supravox, it is not only wide but deep and tall. Oftentimes big soundstage, combined with dynamic presentation, comes with "big-mouth-ness." That does not happen with Supravox. The singer’s mouth is just as big as mine, and it remains locked on the stage with convincing height and depth.
4) They are sensitive even with low excitation voltage. (96dB at 6.5V) Even though the published impedance is 4 Ohms, it does not drop much below that. My 2A3 single amps have highsh source impedance (as any traditional single-ended tube amp) but easily drive them to very loud volume level without noticeable degradation. 215-2000EXC would make SET amps happy and sing.

And below is a list of hints and cautions, including few shortcomings I could find:

1)Thanks to the electromagnet design, one may change the character of the drivers quite dramatically. At low voltage (7V and below), they are polite and laid back. 10V would be about maximum I would use, at which voltage the character is very exciting and lively. 6.5 to 8V would probably suite most listeners. Since the Qts varies accordingly, one may also tune the drivers to particular enclosures or room acoustics to a degree.
2)Their very high Qms and ultralight moving mass require enough room behind the cone to breath. Enclosure, be it a bass reflex, horn or transmission line (closed box wouldn’t do except aperiodic configuration), would be fairly large. (For transmission line the cross section needs to be at least 5 to 6 times the cone area, according to simulation) There must not be any thermally resistive material – such as fiberglass batting or wool – immediately behind the drivers, since the electromagnet produces fair amount of heat.
3) They beam. This is not surprising since the design does not incorporate whizzer cone or inductive coupling metal dome. Thusly sweet spot is relatively limited, and the drivers need to point to the listener directly. 215-2000 is a "for your ears only" driver.
4) Due to their very sensitive, revealing nature, one may find them "unforgiving." Changing amps and cables results surprising difference. While excellent source would sound truly remarkable, poor quality recordings could be less enjoyable than with other loudspeakers.
5) There is no need to worry overmuch about excursion limit, which is incredibly generous 8mm peak to peak. As the designer warns, however, it is always advisable not to overpower them on open baffle where there is no loading under the acoustic short-circuit determined by the baffle size. In a horn or transmission line, the safe operation margin is probably bigger than that of your ears or the tolerance margin of your neighbors.
6) The most serious shortcoming of this extraordinary unit is its price, which is on par with the most expensive fullranges on the globe. However, in addition to the supreme build quality and performance, its owner will enjoy one of the best possible customer services. If there is something wrong with the driver or its implementation, it will be taken care of promptly and thoroughly. The performance of the driver and satisfaction of its owner are not merely of financial importance to the company: it is rather a matter of pride, honor, and privilege. I am not exaggerating with PR clichés here – such has exactly been my experience.

It is not wise to claim a driver to be the "best," especially a fullrange, for obvious reasons. However, Supravox 215-2000EXC is, at least so far, the best to my ears. If I were asked to describe the driver in a couple words, I would say that it is both dynamic and elegant. Drivers with pretty tone commonly sound "small," while energetic ones are often flawed with harshness or uneven balance. 215-2000EXC makes no apology to either department. If I were asked again to add one more sentence I then would say that it excels both in musicality and objective performance. There are drivers with excellent measured data: they usually tend, sadly, to sound flat and dull. On the other hand, quite a few vintage drivers and a small number of modern fullranges are praised for their musicality. Their objective performance such as frequency response and power handling, however, is often unsatisfactory, requiring some sort of ideological commitment. Again, 215-2000EXC does not compromise either.

P. S. I have no affiliation or any such relationship with Supravox. I am just a very happy customer. I hope this wonderful product may please many music lovers.

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Product Weakness:	Requires big enclosure and power supply, expensive, limited sweet spot
Product Strengths:	High sensitivity, excellecnt dynamics and resolution, good balance

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Associated Equipment for this Review:
Amplifier:	See review text
Preamplifier (or None if Integrated):	See review text
Sources (CDP/Turntable):	See review text
Speakers:	See review text
Cables/Interconnects:	See review text
Music Used (Genre/Selections):	Mostly classical, including large scale ochestral/choral works
Type of Audition/Review:	Product Owner

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