Scientific Fidelity Tesla loudspeaker Manufacturer's Comment
"Any magazine which publishes reviews has a primary responsibility to the truth."—John Atkinson, "As We See It," Stereophile, Vol.14 No.12
Borrowing a few lines from Stereophile seems to be the best way to make a point. All we at Scientific Fidelity want is the same thing from this review: the truth.
"Cuz Oi Di'I' Moiiiiiii Whyyyyyyyyyy!"—Corey Greenberg, Stereophile, this issue
Now, I must admit I have never heard Sid Vicious do "My Way," and I'm not sure I want to. My personal tastes lean more toward the Sinatra version, for whom the song was written. But this does show just where Corey is coming from. So, from now on I will call this "The Sinatra Factor." Yes, I did it my way, I am very proud of doing it my way, and I will always do it my way (not "Moiii Whyyyy"). No designer worth anything does it any way but his own.
Anyone can be caught "with egg all over your face, a dunce cap on your head, your Sansabelts down around your ankles, and a roomful of people laughing like hyenas at your wretched plight."—Corey Greenberg, Stereophile, this issue
I made a blind assumption about the caliber of Corey's system given the nature of his work at Stereophile. Well, it's my own damn fault! When I heard Corey's system I should have run screaming into the night. I have never heard the Spica Angeluses (a very fine speaker) sound so lifeless. And in his room, on his system, my speakers sounded terrible. Of the more than 100 rooms in which I have set up the speakers, I have run into four that were problem rooms. Corey's was one of them. The problem seems to occur when two dimensions of the room closely duplicate multiples of the woofer height from the floor. This also happens to be about the same dimension as the internal cabinet height. Under these conditions the room will ring at 75Hz for some time after the speaker stops making sound. The Tesla was designed with the port open. The port plugs were designed to add control in problem rooms. This should be evident from Sam's comments. The disagreement between Corey and Sam Tellig on the port plugs supports this.
As far as single wave-front technology goes, it has a far more solid basis than Corey implies. Our claim is that when two or more identical drivers are used to reproduce only wavelengths longer than their respective distance, they are acoustically coupled and act as a single piston reproducing a single wave-front. This is why well-designed line arrays work without comb filtering. Now, if you cross over the woofers before they get into the shorter wavelengths (where they de-couple, causing interference patterns and the resulting response lobes) to a tweeter located in the center, you can duplicate many of the properties of a point source.
Why? It's not because the acoustic size of the point source is forced to shrink due to crossover slopes. (A point is a coordinate and has no size.) It is because the piston which is driving the air shrinks as frequency rises. (As it does in most speakers.) This is the reason crossovers and drivers of different size and frequency range are made. The difference in our speaker is that it maintains a single coherent wave-front from the bottom to the top of the spectrum. And John Atkinson's off-axis measurements help confirm this. You don't see any above- or below-axis dropouts. The only anomalies you see are bumps and dips due to surface diffractions 1.5 octaves past the crossover point.
"Thoroughness and objectivity are the highest ideals to which a reviewer can aspire. Thoroughness and objectivity—a manufacturer deserves no less from a reviewer."—Robert Harley, "As We See It," Stereophile, Vol.14 No.9
If Corey didn't like the image the way I set up the speakers, he should have moved them. Also, I called Corey and told him we had discovered a rare problem with the tweeters. I alerted him to watch for these symptoms: an oily film on the domes and/or a hardness or bright glaring sound, especially if it seems to come more from one side than the other. Obviously, from his pink-noise test, he chose to ignore this. He also ignored my request that, due to the bass overhang, he try them in other rooms.
"Anything that can go wrong will, especially during a review."—Murphy's Law
When Corey's speakers were returned to me, I noticed both tweeters were covered with so much ferrofluid they were collecting lint. What happens when ferrofluid eats away at the glue holding the tweeter dome and voice-coil former together? The dome eventually breaks loose from the voice-coil former. We found out later the damage is caused only when the speakers are air-freighted. The expansion of air (trapped between the pole piece and magnet) forces ferrofluid out onto the dome.
I decided to keep the worst speaker (Serial No.377) intact and have it tested by an unbiased, independent laboratory as soon as possible. I replaced the dome in No.378 with a new one so they would have a reference. The lab submitted a report supported by graphs which clearly show that, although frequency response is slightly altered, distortion has increased tremendously from 1kHz up (the frequency range covered by the tweeter). On speaker No.378 (the speaker with the undamaged tweeter), distortion is 40dB down, less than 1%. But on speaker No.377 (the speaker with the damaged tweeter), distortion is only 20dB down. [See figs.1 and 2, which show the levels of second and third harmonic distortion for No.377, and figs.3 and 4 the same for No.378.]
Fig.1 Scientific Fidelity Tesla, #377, defective tweeter: 2nd-harmonic distortion (below), anechoic response (above), plotted from 70Hz to 20kHz (12dB/vertical div.).
Fig.2 Scientific Fidelity Tesla, #377, defective tweeter: 3rd-harmonic distortion (below), anechoic response (above), plotted from 70Hz to 20kHz (12dB/vertical div.).
Fig.3 Scientific Fidelity Tesla, #378, okay tweeter: 2nd-harmonic distortion (below), anechoic response (above), plotted from 70Hz to 20kHz (12dB/vertical div.).
Fig.4 Scientific Fidelity Tesla, #378, okay tweeter: 3rd-harmonic distortion (below), anechoic response (above), plotted from 70Hz to 20kHz (12dB/vertical div.).
It is very surprising that Corey perceived this as brightness only and didn't know something was very wrong. However, now that I have heard Nos.337 [sic] and 338 [sic] for myself, I concur with Corey's assessment of a damaged product.
Normally we do not air-freight speakers. But, for reviewers, along with an indefinite loan program, we had a policy of shipping by next-day air and now this policy is coming back to haunt us. The fact that all speakers sent to Stereophile for review were shipped by air (with the exception of the pair I delivered to Santa Fe that were never even opened) means that they are all suspect; the reviewers have helped to confirm this. Corey says they are "4th-of-July-sparklers bright," Sam Tellig says they sounded "as if the top end had been lopped off," while Jack English is somewhere in the middle. I know what we are seeing here are varying degrees of tweeter damage.
"Any magazine which publishes reviews has a primary responsibility, not to its advertisers, but to its readers."—John Atkinson, "As We See It," Stereophile, Vol.14 No.12
The evidence shows it is not just possible, but probable that this review is inaccurate and not representative of our product, and that it does Stereophile readers a great disservice.
This problem is not part of my design—it is one of air-freight damage and it occurs after the speaker has left the factory. We have now determined the cause and are correcting it. At its peak, only 5% of our production was affected.
"By telling the truth, you inevitably benefit the reader."—Larry Archibald, "As We See It," Stereophile, Vol.14 No.12
I can only hope the readers will keep open minds and read the forthcoming reviews in other magazines, then go to their nearest Scientific Fidelity dealers and form their own opinions.—Mike Maloney, Scientific Fidelity
Although I do not like to respond to "Manufacturers' Comments" letters, feeling that this is the manufacturers' and distributors' part of Stereophile, where they can say what they want, no matter how intemperate, I must put the record straight on two matters. Contrary to what Mr. Maloney states in his response, he did not warn CG about either the putative tweeter problem or its effect on the sound. In fact, the first any of us at Stereophile heard about this supposed problem was when I visited Scientific Fidelity at the 1992 Las Vegas CES in January, some five weeks after CG had finished his auditioning of the second, less bright pair, and sent the speakers to Santa Fe for me to measure. (This was also nearly a week after Scientific Fidelity had been sent the preprint of the reviews so that they could prepare a "Manufacturer's Comment.")
Mr. Maloney told me at the WCES that the Teslas were being affected by a problem with the tweeters that apparently occurred when they were air-freighted from Vifa in Denmark. He promised a letter from Vifa confirming this, a letter which I never received.
Now, it appears, the problem is due to air-freighting of the complete loudspeaker system, and no more than 5% of Tesla production was affected.
Second, regarding the speaker's boomy bass: Though Mr. Maloney had already visited CG at that time, he didn't mention the purported room problem but told me that the original Teslas' boominess was due to out-of-spec woofers. He requested that he be allowed to send CG a third pair of Teslas for review. Now, he says, the boominess was due to CG's room all along.
We can only report on what we hear. I must caution readers who are interested in buying the Tesla for what it does do well—soundstaging, for example—to carefully audition the speakers with their own ancillaries and music at high levels. Then, as Mr. Maloney says, they should make their own decisions.—John Atkinson