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"The physical design of this speaker is quite impressive"
"...it images off axis like no other speaker I have heard."

Pinnacle Black Diamond Series BDC 1200
Publication: Sensible Sound, September/October 2006
Reviewer: David Rich

Specifications:
1" liquid-cooled silk dome tweeter
(2) 4” glass fibercone midrange with rubber surrounds
(2) 4” glass fibercone woofers with rubber surrounds
4th order vented design with rear-mounted port
Automatic overload protection circuit
10-year transferable warranty on parts
7.13” W x 43.5” H x 12” 0 (with grille)
40 lbs. each

Pinnacle is probably best known for what they call the “Diaduct Bass Accelerator Port Tube,” which is essentially a port angled in a cabinet to gain length. It is patented, and years ago Julian Hirsch wrote a review which clearly demonstrated his admiration that the company’s compact speakers “generate deeper or less distorted bass for a given driver and cabinet size (and price) than would be possible otherwise”. This review, which appeared January 1988, along with several other positive reviews that followed, likely helped launch the fledgling company into recognition as a mainstream loudspeaker manufacturer.

I first heard a Pinnacle product outside the showroom when Peter Aczel tested Pinnacle’s large tower (71 pounds and 45” high) speaker, the Classic Gold Aerogel, I was impressed enough with the speaker to recommend it to the president of the Bethlehem (Pennsylvania) Chamber Music Society. My recommendation was based on her need to have a really good system so that demo CDs of groups we were auditioning (I co-chair the music committee of the group) for our concerts could be reproduced with enough fidelity for her to evaluate the tonality of the players.

These days, big towers may translate into small sales, so Pinnacle challenged itself to obtain the quality of sound of a top of the line tower loudspeaker (minus the bass extension) with something smaller, yet still floorstanding. The Black Diamond Series BDC 1200 is one of a series of new products designed to fulfill this new design paradigm.

The physical design of this speaker is quite impressive. It has a very narrow but relatively deep cabinet. The Pinnacle folks describe it better than I can: “Visual sophistication is attained by the unique integration of cherry grain cabinetry with complementary 6-layer high gloss black lacquer accents.” As a finishing touch, the cabinet’s side walls exhibit a graceful bow, creating a refreshing departure from the “boxy” look. It is the first speaker that I have found that non-audiophiles find visually appealing. (These music lovers normally dismiss any speaker that is not hanging on the wall, or preferably mounted in the wall). My experience revealed that when I had the BDC 1200 located in a small room, visitors actually considered the speaker a decorative element.

The back of the speaker has high-quality joints, providing an absolutely flat back panel. No cheesy plastic termination cup is present. The ultra-high-tech looking sets of speaker terminals are mounted straight into the cabinet, complicating assembly since Pinnacle has no way to separate the crossover from the speaker at the back. Alas, the terminals are not correctly spaced for double banana plugs; this likely is in keeping with electrical safety codes outside the US, thus enabling Pinnacle to realize international sales without complicating assembly and inventory practices.

The narrow front baffle led the design team to set the maximum driver size at 4 inches. The 7-inch width specified by the manufacturer is measured at the cabinet’s widest point, where the sidewalls reach a maximum width. The end caps also increase the speaker’s total width. The width at the front baffle is closer to 5 inches.

Clearly, one 4-inch woofer is not going to do the job. In the BDC 1200, two woofers are used. One might think that if two woofers are good more would be better, but it is not that simple. The effective vertical length of a large array of small woofers can become very large (four 4-inch woofers would have an effective length of 16 inches, ignoring the additional distance required by the driver’s basket) and this can result in suckouts in the speaker’s response below the crossover to the midrange, because the woofers will be significantly below ear height.

Two similar looking 4-inch midranges are placed above the woofers, one above the silk dome tweeter and one below. The crossover point of the woofers to the midrange is specified at 200 Hz. That is not a frequency that is easy to verify using close-miking techniques, since the woofer leaks into the midrange measurement even with the microphone pushed as close as one can without hitting the cone. I could have pulled the drivers out of the box and disconnected the woofers to make the midrange measurements but it was clear that getting the drivers out of the box was not going to be easy. The gaskets behind the woofers in the BDC 1200 are effective in keeping the air in and prying fingers out. Bi-wiring makes the measurement of the midrange and tweeter crossover points a lot easier. The tweeter has a relatively high crossover point of about 4500 Hz. The tweeter crossover appears to be a single-order high pass. The midrange appears to be a second-order low pass.

The cosmetics of the unit dictate the use of a rather thick grille, which does have significant effects (Figure 1). One effect is that the grille attenuates the high treble, helping ensure top end balance—it is clear that the manufacturer wants this speaker to be used with the grille on. Even with the grille on, however, a significant rise in the mid treble is noted at 4,000 Hz, just below the crossover point. Because the tweeter is rolled off a slow rate (6 dB/oct.), it still has significant output at 4,000 Hz to contribute to the total radiated power of the speaker at that frequency.

The lower section of Figure 1 shows an average of the speaker’s vertical dispersion characteristics (-15 to +15 degrees in 7.5 degree intervals). The individual curves are shown in Figure 2. A significant notch develops as the microphone is moved above the tweeter axis at 2 kHz; yet the crossover is more than an octave beyond that. What appears to be happening is that the two midrange drivers are interfering with each other or becoming highly directional (the combined size of the drivers if placed next to each other would be at least 8 inches in the vertical direction). In the average we see the effects of the driver midrange interaction dominate (Figure 1 bottom). We also note the rising top end. Again, these measurements are with the grille in place, resulting in the response ripples seen in the tweeter passband.

Audiophiles often think a midrange/tweeter/midrange (MTM) array has some advantages besides increased power handling of the midrange. The principal misconception is that the configuration allows optimization of axial and power response at the same time. Dr. Lipschitz put that one to rest in a classic paper (“Power Response of Loudspeakers with Noncoincident Drivers-The Influence of Crossover Design”- JAES Volume 34 Number 4 pp. 236-244; April 1986). Still, the variation in frequency response with changes in vertical angle Pinnacle has achieved at the 4.5-kHz crossover point is actually impressive given the low-order crossovers. No crossover interactions are seen down to the 300 Hz limit of these measurements, indicating that the crossover between the woofer and midrange indeed occurs below this frequency.

Horizontal response (Figure 3 top) was measured with the grille off. Horizontal axis measurements with the grille on showed increasing and deleterious effects as the horizontal angle was increased (graph not shown). With the grille off we can see that the small drivers and thin cabinet result in excellent performance with little deviation except near the tweeter crossover. In a speaker with a 6.5-inch midrange, for example, we would expect to see more rolloff off-axis near the crossover to the tweeter as the midrange becomes directional. The rise in the tweeter’s response is again seen, although the effect is suppressed as the angle is increased. Figure 3 bottom is the average of the curves shown in the upper curve (off-axis curves double-counted).

Peter Moore, a loudspeaker designer for Pinnacle since 1993, points out that emphasis in the BDC 1200 design was placed on getting good in-room response. Figure 4 shows the manufacturer’s in-room measurements done from approximately 7-8’ back from the speaker with the microphone directed towards the top driver. The measurement is a 1/3rd-octave RTA response. (Note that I cropped the chart supplied by Pinnacle to make the spacing of the vertical axis divisions more closely match those of my graphs).

While the curve somewhat correlates with Figure 3 bottom, the overall response fits in a tighter window and the high end lift is less apparent. I did not show my own RTA (actually the ETF software in the “Psychoacoustic Mode” or with a long gate time) since in my room the various boundaries appear to dominate the measurements. Others on the reviewing staff at T$S have had better luck using weighted, continuous averaging (Moran, Strauss, et al). ETF has a new product called R + D (Resonance & Distortion) that allows sophisticated averaging. I have not tested it yet.

Moving from measurements to subjective testing, it was clear that the very narrow baffle offers significant acoustic benefits. It was difficult to identify the presence of the speakers themselves in the sound field. Perhaps more significant is how well the sound field remained stable as one moved off the center listening axis. The BDC1200 did not localize, even deeply off-axis, and the image was very stable even when I moved around the room. The image seemed in front of the speaker, floating in air. This ability to create a floating, airy quality is often absent with speakers using tweeters with waveguides. A waveguide does improve the ability to localize images in big boxes, yet the BDC 1200 still managed to retain some of that attribute. Clearly the very thin baffle in conjunction with the tight horizontal dispersion characteristics does make a difference. This suggests that the BDC 1200 is a good choice for a living room with couches placed throughout the room, although one hopes at least one be placed close to optimal. All the speaker seems to ask is that you do not try to hide it by putting a large potted plant in front of it!

I started listening to the speaker in my large (16’ x 24’ with a complex cathedral ceiling), listening space in a location where other towers (recently auditioned) were positioned. Sonically, the speaker was significantly on the bright side of neutral. I could find no speaker placement where I was happy with the tonal balance without dialing back the treble control one or two notches. I could have taken more radical steps, such as trying to attenuate the top end with a passive L-pad, or biamping the speaker. Because L-pads introduce additional resistance in series with the tweeters crossover, though, the crossover characteristics might change. The biamping approach is not a tweak move, because my object is to vary the tweeter level using the amplifier’s level control (the amps I would have used have these controls) without placing any components between the amplifier and tweeter input. Under normal circumstances, I do not recommend biamping.

Given that neither of these approaches is likely to be undertaken by the typical purchaser, I decided not to attempt playing speaker designer after the fact. Instead, I used the tone control on my amplifier. Not all speakers can be brought back to neutral tonality with a tone control, but with the Pinnacle it worked out very well. The high end rise matched the typical treble control roll off.

Even with the tone controls adjusted optimally, the speaker was not as neutral as some of the speakers I have reviewed in past issues. Perhaps the slight lift in the 1 kHz region was responsible for this. The averaged vertical plane measurements (Figure 1 bottom) do not appear to correlate with the sound of the speaker when auditioned at tweeter height. Removing the grille cloth improved the speakers’ tonality in the upper midrange, but the speaker does not look correct this way, and an even heavier hand on the treble control was required.

On the other hand, bass was very smooth, without the heaviness of some of the larger units in my big room. Yes, one could argue some of this was the lower limit of the speaker, but look at Figure 4 from the manufacturer. My own ETF Psychoacoustic measurements roughly match the bass response shown in Figure 4.

When I stood up, the perceived tonality of the speaker changed significantly, although not to the extent that it became unpleasant. The changes were also not as abrupt as in other speakers in my experience. I have found that speakers that have subjectively abrupt changes in tonality can sound strange even on the speaker’s optimal axis (this effect is usually correlated with measurements showing changes in frequency response over a wide area of the midrange spectrum, not just near the tweeter crossover point. I have found 2.5-way speakers with more than two woofers can have this problem if they are not very carefully engineered).

Another positive point for the BDC 1200 is that although the linear vertical listening range is restricted, it is symmetrical about the tweeter (Figure 2). Some speakers with poor vertical response patterns insist that you sit below the tweeter axis. This is based on some strange idea that everybody listens on a soft couch with an average ear height of 39 inches. Measure this yourself sitting in a variety of seats and you will be surprised at the variation in ear height The BDC 1200’s overall radiation patterns allow its successful use for listening to music while seated, yet still being acceptable for use when entertaining standing individuals.

In my large listening room, the speaker ran out of output capability before other, bigger floor standing units with two or three 6.5-inch woofers. It also obviously did not have the bass extension of the larger units. Perhaps a subwoofer or two would have helped the Pinnacle, but I am not a fan of that approach (see issue 106) and I do not think a subwoofer would blend with the BDC 1200 to yield the smooth bass one gets from the speaker alone. It should be noted that Pinnacle makes a number of excellent, compact subwoofers if you wanted to give that approach to bass extension a try.

Looked at another way, the BDC 1200 will outperform most mini-monitors or one of those long, thin on wall or on video device speakers in a similar sized room by providing superior dynamic capabilities. On the other hand, the best mini-monitors exhibit less coloration than the Pinnacle with no equalization applied.

So, let’s move them to the small room (12’ x 16’ x 8’), where many thought they looked so cool. Bass was nicely reinforced with placement about a foot from the rear wall and the off-axis imaging characteristics of the speaker were retained. Mini-monitors with bigger 6.5-inch woofers could not compete with the BDC 1200 with respect to imaging off-axis. Room gain brought the bass up subjectively, so it sounded flat down to 50 Hz (the manufacturer specs the woofer’s -3 dB point at 45 Hz). Dynamics were no problem in the smaller room, again out performing the mini-monitors I had on hand.

Although the freedom from the localization of the cabinet and the transparency of the sound was retained, the tonal balance towards the treble range remained. Violins could take on a harsh tone. Chamber music (woodwinds and stings) lacked warmth. Putting in the tone control had a significantly positive effect. Harshness dissipated significantly and some warmth in the lower midrange reappeared. Fortunately, none of the positive characteristics of the speaker was lost. With the tonality corrected, I could hear that the top end was free of the edgy coloration that can be heard in some tweeters, although typically not in a speaker in this price range. The limited vertical dispersion characteristics could be more bothersome in a smaller room, since one often listens closer to the speaker (simple trigonometry tells you that a change in height of the listener will result in an increase in the off-axis angle when you are closer to the speaker).

In summary, the BDC 1200 gets positive comments about its looks even from those who have absolutely no interest in High Fidelity. The tall, very thin shape provides sonic benefits to those of us who do not care what a speaker looks like. It images off-axis like no other speaker I have heard, and on-axis it provides good placement of images across the soundstage without losing an airy sound, provided you turn the treble control down. The size and shape of BDC 1200 allow you to place it in a smaller room where a full-sized floor stander might look out of place, or have overly enhanced bass when placed close to the back wall. For those not bothered by listening with the tone control engaged, or who have less sensitivity to a rising treble tonality, the Pinnacle is a very good choice for use in small rooms, or in larger rooms where optimal placement of the listening positions is not possible.
-DAR


 

 

 

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