Stand Loudspeaker Reviews

Manufacturer's Comment

Editor: There are comments in this review, both positive and negative, that are right on target. We have only a couple of major bones to pick with Tom Norton's subjective review, but we have many comments about John Atkinson's test methodology and interpretation of the measurements.

Tom Norton's taste in previous loudspeaker reviews has seemed to gravitate heavily toward systems that can deliver extended and generous bass, such as the B&W 801s he refers to at the beginning of the review. When compared to such systems, the Panoramas will admittedly be shy in the bass range.

When I found out Tom would be reviewing the Panoramas alone without their companion Bass Extension Modules (BEMs), I requested that SOTA either withdraw the product from this review or wait until we could get the BEMs into the picture.

Unfortunately, this did not happen, and now we must deal with the review at hand. Hopefully we will get another shot, this time with the BEMs.

OK, now to the meat of the response.

We feel the initial comparison to the WATT is most appropriate, as we set out to build a speaker along the same principles; ie, a minimonitor which covers the 70Hz–15kHz range with utmost transparency which can then be coupled with a good subwoofer to complement its relatively shallow bottom end. We have always had the intention of mating the Panoramas with a suitable subwoofer, and for the most part listen to them paired up with the SOTA BEMs.

We feel we have surpassed the WATT in terms of imaging and transparency: nearly everyone we have talked to who has compared the two has expressed a preference for the Panoramas, including people who already own WATTs. It is therefore very puzzling to us that Tom didn't like them enough to recommend them a bit more enthusiastically.

The only explanation we can find is that, in all probability, Tom has only heard the WATTs with subwoofers, under which conditions they are truly excellent speakers, as are the Panoramas. Without subwoofers, the WATTs also tend to sound rather thin, although they retain excellent transparency. It is our guess that Tom may end up liking the Panoramas just as well or more if he can audition them with the BEMs or other suitable subwoofers.

In the meantime, we would like to address several items we feel are noteworthy:

1) The use of the Focal tweeter. There seems to be a good bit of Focal tweeter–bashing going on at Stereophile, bashing which is not merited. Yes, it has a rising response and a peak at 16kHz, when measured on-axis, and yes, it can sound a bit tizzy at the extreme upper octave. But there is a reason for people like Wilson and us to use this type tweeter even though it costs more than twice as much as other "comparable" units, and that is that it reproduces the range between 2kHz and 14kHz with more transparency, clarity, and impact than any other unit we have evaluated. It does have a 16kHz peak on-axis, mostly due to the rise in response due to directivity of the driver (and a small resonance), but it's fairly flat off-axis up to about 18kHz. It's a small price to pay, especially if you want that transparency in the midband. We stand by our choice until something better comes along.

2) The measurements shown were taken on the axis directly in front of the system. They closely correlate with our measurements at the same points, but paint a very incomplete picture.

This is a major issue because the Panoramas are designed to produce the flattest response in the area between 15° and 45° off the horizontal axis. It is in this region that they measure best and sound best. These speakers are meant to reproduce a fairly uniform power input into the room, and will tend to sound and measure overbright if they are toed in toward the listener. This is how they were evaluated, as described by Tom in the initial part of the review, and we feel his comments reflect incorrect positioning of the speakers.

We also feel you should have consulted us as to the best orientation of the speakers before you started the review, and certainly before you undertook the measurements. We use test equipment which is comparable to the MLSSA, and would have gladly assisted you with information to extract the best from these speakers. We are frustrated that you chose not to return Allen Perkins's phone calls to try and help with this very important factor before publishing comments and measurements that reflect non-optimal performance. Why didn't you communicate with us? Is there some editorial rule that prohibits contact or discussion before a review is completed?

In fact, most of the measurements you sent us were taken near the very worst measuring positions, and, if published, are likely to leave the layman with a very negative and incorrect impression of the system's true nature. This is unfair to us and your readers. If you are going to publish technical data, please make sure you have a good understanding of where and what to measure; otherwise, you run the risk of making harmful mistakes.

3) Reasons for the imaging being as good as it is: We are pleased that Tom picked up on the superior imaging of the Panoramas. We are not pleased that John Atkinson chose to attribute the imaging of this system to a resonance and then drew an irrelevant analogy to a black-and-white static development process used in photography. No, John, that ain't the reason. Please note that Tom said "sculpted in space," not "etched." One implies a body, the other a delineation.

There are many reasons our speakers image so well. Among them:

a) Most systems have only one point (usually on the front axis) where the response is optimal. We strive for a time-coherent output at 15° to 45° on either side of the frontal axis so that we can get two symmetrical areas which are time-corrected. This allows coherence between the direct field and the reflected field, which contributes mightily to the holographic image.

b) Time correction provides minimum phase response through the 70Hz–6kHz range, and it shows up on your MLSSA plots. We worked our butts off to make this region as good as possible, and frankly feel a bit nonplussed that an engineer of your caliber would completely overlook this factor and ascribe the imaging to a resonance!

c) Suppression of resonances: Resonances destroy imaging by drawing attention to the physical space where they are occurring. Your comments concerning the bass-mid driver resonance at 3700Hz are valid only for the on-axis location. The driver smooths out remarkably between the 15° and 60° off-axis area, rolling off with a nicely controlled characteristic above 2.5kHz. It's a bit peaky on-axis, but its overall smoothness and transparency more than make up for this flaw. By the way, Thiel uses a 5" driver, not a 7" as we are. This is more than a "slight difference."

4) Your comments concerning the choice of a first order in the filter networks are off-target (or should we say off-axis?). We are not using a traditional first-order network, but instead are using the differing directivity and phase response of the drivers to correct for the box lift due to the size and shape of the enclosure. In effect, this network compensates for the box lift by creating a mild "suckout" in one region and an additive response in another. By properly tailoring these characteristics to those of the box, we end up with good performance on-axis and superior performance off-axis.

As we noted earlier, the intent with this design is to provide passable on-axis performance and excellent 15–60° off-axis performance. It is this controlled directivity that helps give the Panorama the boxless quality and superior imaging Tom alluded to in his part of the review.

In sum, while Tom picked up on the imaging and transparency virtues of this system, we believe he auditioned them in a non-optimal situation and got less than optimal results. We hope we can get Stereophile to look at the Panoramas again, this time with subwoofers, and feel confident that the response will be much more favorable when the bottom end is there.

Under correct circumstances, we feel there is nothing out there that can match the Panoramas for sheer lifelike transparency, imaging, and overall sense of being there.

We urge you to judge for yourself. Thank you.—Jack Caldwell, SOTA

More Measurements
As I have said in previous issues of the magazine, I do not like responding to letters from manufacturers in this section of the magazine. My writers and I have had our say in the reviews; this is the place where manufacturers and designers can say whatever they like in rebuttal or support of those reviews.

When it comes to misstated or misinterpreted matters of fact, however, I feel I must put the record straight: when Mr. Caldwell states that "The measurements shown [in the review] were taken on the axis directly in front of the system...[and] are likely to leave the layman with a very negative and incorrect impression of the system's true nature," he is not completely correct. My fig.2 in the review showed the different responses that could be obtained from the Panorama on three different vertical listening axes: on an axis directly in front of the drive-units and midway between them; 15° above the tweeter axis (ie, representing the sound that would be perceived by a listener standing in front of the speaker); and on an axis level with the cabinet base, this representing the axis that I understood to be intended by Mr. Caldwell and, as mentioned in the review, for which the speaker has to be tilted back considerably.

With the exception of fig.5, which showed the non–time-coherent step response on the direct axis, and fig.10, which showed that there was no difference in this response due to the speaker being measured at Santa Fe's altitude rather than at sea level, all the other curves were taken on this optimum frontal axis. My value judgments in the text refer to the speaker when measured on this axis.

Mr. Caldwell, however, does state that the speaker's peaky on-axis treble, due both to the woofer resonance and to the tweeter's rising on-axis response, will smoothen as the listener moves to its side, meaning that the Panorama should sound more neutral when not toed-in to the listening position. I accept that my measurements offered in support of TJN's review did not explore this aspect of the speaker's behavior, so upon receiving Mr. Caldwell's letter I carried out a set of FFT-derived, quasi-anechoic response measurements in order to examine the Panorama's lateral off-axis behavior.

The results are shown in fig.1: the rearmost plot shows the response 48" away on the speaker's optimum axis directly in front, which is the first-arrival sound perceived with the speakers correctly tilted back on their stands and toed-in to the listening position. The next four plots are, in order, the responses 48" away on axes 15°, 22.5°, 30°, and 45° away from the first. In effect, these show how the treble/midrange balance of the Panorama will change as the speaker is rotated away from the listening position, the final, frontmost plot at 45° actually representing a slight amount of toe-away from the listening position with a typical included angle between the speakers of 60°–75°.

It can be seen from this figure that the Panorama's midrange and high treble do indeed become more flat as the listener gets more off-axis—TJN noted the speaker's "open, relatively uncolored" sound, and that the woofer resonances (the twin peaks around 4kHz) also get somewhat lower in level. In addition, cumulative spectral-decay analysis of the 30° off-axis impulse response shows that while the woofer resonance hasn't totally disappeared, it now doesn't develop until some 15dB below the reference level. Though a significant and presumably audible lack of energy in the crossover region remains, the direct sound of the speaker will become more neutral as the speakers are listened to significantly off-axis. I agree, therefore, that toeing-in the Panoramas to the listening seat is, indeed, suboptimal, and my contribution to the review was at fault in not emphasizing this fact. My apologies to SOTA and to Mr. Caldwell for this omission.

I must point out, however, that the fact that one axis can be found where the speaker sounds relatively neutral does not in itself mean that the measured excesses of energy in the mid- and high-treble regions on other axes will not make their subjective presence felt. The ear integrates the direct sound from a pair of loudspeakers with the reverberant soundfield in the room, and the exact degree to which either contributes to the perceived tonal balance is dependent both on how far away the listener sits from the loudspeakers and on such matters as how absorptive are the walls, floor, and ceiling. Even with the speakers positioned optimally, TJN still felt the Panoramas to have a somewhat peaky treble. This was revealed in my fig.4 in the review, which represents the overall 1/3-octave response in-room at the listening position, spatially averaged to remove the effect of low-frequency standing waves. (I have found that this measurement nicely reflects the degree to which the ear integrates direct and reverberant soundfields in rooms where the listener sits so as to get a roughly 50:50 mix of both.)

Regarding the loudspeaker's near–minimum-phase character below 7kHz, I did mention this in my contribution to TJN's review, along with the superb soundstaging (which I certainly didn't mean to ascribe totally to the presence of the strong woofer resonant mode just above crossover). I note that, as suggested by Mr. Caldwell, this minimum-phase condition also applies to the off-axis responses I refer to above. Fig.2 shows that measured on the optimum vertical axis but 30° to the speaker's side; the departure stays within +0, –55° between 300Hz and 10kHz (the cursor position shows a departure of –54.5° at 5240Hz), which is excellent. However, while I have also found a degree of correspondence between this characteristic and accurate portrayal of the soundstage, I feel personally that for a speaker to be minimum-phase but unflat in amplitude response, as the Panorama clearly is, only gets halfway to the desired goal.

I note with interest that in his recent review of the Panorama in Sounds Like..., reviewer Art Dudley pretty much agreed with Tom Norton regarding the speaker's tonal signature when listened to on its optimum axis, a tonal signature that I felt my measurements in the review to a large extent explained. I do accept, however, that the addition of a subwoofer changes everything—what may be unacceptably peaky highs with a minimonitor could metamorphose into a subjectively acceptable degree of HF "air" and "detail" when balanced by an extended and powerful bass—and both Tom Norton and I look forward to hearing a pair of Panoramas used with their matching Bass Extension Modules (footnote 1).—John Atkinson

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Footnote 1: SOTA never did submit the BEMs for a follow-up review with the Panorama. However, when I remeasured both samples of the Panorama that TJN had auditioned following the publication of this "Manufacturer's Comment," I found that the two speakers measured differently. The responses of the two samples are shown in fig.3 above,with the original sample I had measured shown in red, the other speaker of the pair shown in blue.—John Atkinson