Burmester Audiosystems B99 loudspeaker
Larry Greenhill, June, 2002
Sometimes it all comes down to the shape of the side panels. I was smitten by the gentle curves of the Burmester B99 loudspeaker's aluminum side grilles, which have uncommon grace. A love affair with an enclosure? Well, yes. After all, beauty is an intensely personal matter. In the words of Burmester's motto: "Art for the ear."
The B99's shape is slightly reminiscent of an airfoil and with an aluminum veneer modeled on the riveted wings of turboprop aircraft. It is a three-way, full-range, floorstanding loudspeaker whose midrange and high-frequency drivers are installed in a D'Appolito configuration; the two woofers are mounted on the side.
The B99's ribbon tweeter consists of heat-treated Kapton foil. Its motor consists of aluminum conductors laminated on the diaphragm foil, and uses neodymium magnets with an energy density 20 times higher than similar ferrite magnets. Silver conductor wires are soldered directly to the diaphragm foil. The ribbon's 28cm2 area (4.34 sq.in.) is protected by a plastic ridge that also serves to broaden the dispersion angle of the tweeter over its working frequency range. The ribbon covers an area about 10 times the size of conventional dome tweeters, allowing for a low crossover frequency of 1.8kHz.
The two 5.6" midrange drivers use magnesium cones that are said to be free from resonant modes to above 3kHzan octave above the crossover point. Each driver has a large gold-colored, bullet-shaped phase plug of copper to prevent compression effects in the center of the driver, and is supported by a rigid, diecast, magnetically nonconductive support.
The bass frequencies are managed by two 10" woofers with air-dried, resonance-damped paper cones. The woofer has a large vent hole in the pole core behind the dustcap to reduce compression effects, and the 1" coil is said to have a long linear throw. The two woofers are mounted either side of the ports and vent through 40 lateral openings, each 10" by 0.5", in the curved aluminum panels on one of the loudspeaker's sides.
Burmester makes the B99 in matched pairs. The process begins with setting tight tolerances for the OEM drive-unit suppliers. The drivers received from the supplier are then burned in for two weeks, using a 10Hz continuous sinewave for midrange units (at 110W) and woofers (at 250W), and a 7W continuous pink-noise signal for the ribbon tweeters. The drivers are then measured and computer-sorted; the 10 units that go into a given pair of B99s are trimmed within ±5dB for their respective frequency responses. All technical specifications for each driver are filed, so that a loudspeaker in the field can receive a new driver identical to the one being replaced.
The B99's enclosure is double-walled. The inner chamber is made of 1"-thick, ultrastiff MDF strengthened with a complex internal bracing system. The midrange driver and tweeter are mounted in their own internal cabinets and the outer housing and inner chamber are insulated from each other by a layer of damping material. Like all Burmester speakers, the B99 is not damped by wool stuffing, because "the woofer has to pull the air through the wool." Rather, the B99 contains mats of a felt-like material in various thicknesses. The thickness of these mats has been calculated precisely in relation to their placement in the enclosure.
The B99's crossoverwhich weighs more than 11 lbssits in its own completely sealed enclosure at the bottom of the speaker cabinet, protected from the "sonic storms" that rage inside the main enclosure. Second-order crossover slopes are used, and impedance correction is used so the theoretically correct filter behavior is not affected by changes in the driver's impedances. Heavy-gauge copper plating is used for the crossover's printed-circuit board. The woofer connections are made with high-purity 10mm2 copper wire, and the midrange drivers and tweeters are wired with pure silver.
The four speaker binding poststwo for the woofer section, two for the midrange-tweeterare located on the underside of the enclosure just below the crossover. Two people are required to change the speaker cables: one to tilt and hold the front end of the 220-lb speaker, the other to crawl underneath and screw down the four large plastic wing nuts.
The B99 comes in three standard finishes: elsberry/aluminum laminate, maple/aluminum, and silver/aluminum. The veneer panels can be changed, thus making it possible to alter the enclosure's color. The fit'n'finish of the cabinetry, hardware, and drivers is superbas you should expect of a speaker costing $47,000/pair.
The pair of Burmester B99s, enclosed in their 6'-high cardboard and foam shipping cartons, arrived at my house by rental van. Udo Besser, then Burmester's marketing manager, was there to help me unload, move, and set them up for the review. He immediately discovered minor shipping damage to one speaker's wooden front panels, but as the damage was insubstantial, the moving operation continued. Each 220-lb speaker was carried into my front door, up a short flight of stairs, and into the listening room.
I positioned the B99s 42" from the back wall, 83" apart (measured from the tweeter centers), and 120" from my chair, with the side-mounted woofers facing each other. Toed-in slightly, the speakers focused on the nearfield listening position while facing down the full length of my narrow listening room. (The room is 26' long, 13' wide, and 12' high, with a semi-cathedral ceiling. The room's other end opens into a 25' by 15' kitchen through an 8' by 4' opening.)
Over the following weekend, I drove the B99s to listen for loose parts, unwanted resonances, or any other sign of shipping damage. I blasted pipe organ music, soprano arias, and rock, relying on my Krell FPB 600C power amplifier to reveal any weaknesses. None were evident. The only rattles I heard were from objects in the room that were set in motion by the music.
Rated at 90dB/2.83V/m, the Burmester B99 proved capable of 110dB sound-pressure levels (SPLs). Driven by 250Wpc Mark Levinson No.334 and 1200Wpc Krell FPB 600C stereo amplifiers, or by a Bryston 14B-ST 800W dual-mono ampall rated for the B99's 4 ohm loadthe Burmesters easily revealed the sonic signature of each amplifier. The Bryston had a smooth delivery with solid, well-defined bass response; the Krell generated the widest soundstage, along with an extended, transparent top end; and the Levinson produced a narrower sonic image, but with bass slam.
I drove the B99 with low-frequency warble tones from Test CD 2 (Stereophile STPH004-2) and measured SPLs at each frequency with a RadioShack sound-level meter resting on the arm of my listening chair. The B99's deep-bass output remained within ±2dB limits from 100Hz to 31.5Hz. Below that, it shelved down by -10dB at 25Hz. I was unable to detect any port chuffing during the warble tests.
Changing over to broadband pink noise, I found the tonality the same whether I sat back or leaned forward. This wasn't surprisingthe height of the B99's ribbon tweeter, 36-41" above the floor, included my seated ear height of 37.5". However, the pink noise dulled as soon as I stood up, or when I moved around the room during the "sit down, stand up, walk around" test.
I was just finishing my May review of Snell's XA Tower Reference loudspeaker when the B99s arrived. Taller and slightly heavier, the XA Tower had a more neutral sonic presentation that made it difficult for me to describe its character. On the other hand, I immediately appreciated the B99's transparency and wide, deep soundstage. And the B99 remained fast, clean, undistorted, and uncompressed at SPLs approaching 106dB. So far, so good.
Despite its measured rolloff below 31Hz, the B99's bass was fast, taut, and powerfuluntil I damped my wall cabinets, its woofers set them buzzing. I both heard and sensed the deep synthesizer notes that punctuate "No Sign of Ghosts," from the Casper soundtrack (MCA MCAD-11240), and the ponderous thuds and ominous rumblings presaging the asteroid impact in "The End of Our Island," from the Dinosaur soundtrack (Walt Disney 50086 06727).
The B99 played with perfect pitch the 32Hz double-bass note that opens Strauss's Also sprach Zarathustra (Time Warp, Telarc CD-80106), conveyed the power and weight of the final organ chords of Elgar's The Dream of Gerontius, Part 1 (Test CD 2), the soft but dense bass-drum beat on "Cosmos Old Friend" from the Sneakers soundtrack (Columbia CK 53146), and the subterranean synthesizer chords from "Assault on Ryan's House," from the Patriot Games soundtrack (RCA 66051-2). It also evoked Tony Soprano's desperation and anxiety with oppressive bass pulsations in "Woke Up This Morning," Chosen One Mix's main theme from the TV series The Sopranos (RCA 7464-2).
The B99 really rocked on pipe organ recordings. Pedal notes were delivered with dense pressure and room lock, as heard on the Allegro of Widor's Symphony 6, from the CD reissue of Marcel Dupré's Recital (Mercury Living Presence 434 311-2). "Gnomus," from Jean Guillou's organ transcription of Mussorgsky's Pictures at an Exhibition (Dorian DOR-90117), was reproduced with a mix of the large organ's shuddering bass notes and delicacy from its pipes and trumpets. Reed's La Fiesta Mexicana, from Fiesta (Reference Recordings RR-38CD), opens with a mix of explosive bass-drum beats and shimmering, reverberating chimes, both superbly conveyed without compression by the B99s.
The Burmester's treble and upper midrange were thrilling, both in their seductive clarity and their ability to reproduce a recording's ambience. The seductiveness reminded me of Quad 57 electrostatic panels driven by Mark Levinson ML-2 monoblocks. Ever since I convinced a local audio store to loan them to me for a weekend, the Quad/ML 2 system has been my standard for midrange lucidity and transparency. The German ribbons were just as good, rendering the top register with plenty of air and a total absence of grain. Billy Drummond's Zildjian ride cymbal, which opens Duke Ellington's "The Mooche," from Rendezvous: Jerome Harris Quintet Plays Jazz (CD, Stereophile STPH013-2), sounded more like the real thing than I've heard before.
Bells, chimes, and triangles shimmered with cascades of clearly defined harmonics. Don Dorsey's "Ascent," from Telarc's Time Warp, played with a mixture of dense bass pulses and chimes that were sweet, translucent, and clean. The leading edges of transients were razor-sharp without being irritating. Dorsey's synthesizer exploded out of black silence with a stream of pulses, beeps, bell-like sounds, and high-pitched squeaks that moved back and forth across the soundstage. The piece's endan explosive shot followed immediately by sullen, massive rumblingwas full of angst and foreboding.
The Burmester B99's retrieval of ambience was outrageously good. "The Mooche" had ambience in spadesthe B99s re-created a dark, somber, distant, sonic landscape. The kick drum took on an oppressive, solid heft, the trumpet and trombone solos blossomed into a stunning, lucid sound full of the biting "brassy blattiness" so admired by Stereophile reviewers.
Another ensemble, this one from Senegal, was vividly reproduced when I played Orchestre Baobab's Pirates Choice (World Circuit/Nonesuch 79643-2). I was transported by the B99s to a steamy Dakar nightclub where time stood still. Released on cassette in 1982, this studio recording has achieved legendary status among those who treasure West African music. Creating a fusion of Cuban rhythms and African folk melodies, Baobab's eight musicians "take the listener to another time, back to a magical studio session," where one floats on "soothing, spellbinding, relaxed rhythmic grooves," according to the liner notes. The B99s' imaging on "Werente Serigne" placed the percussion on the left, a droning blend of singers on the right, with the main singer and a syncopated tenor sax in the center. "Soldadi," a song from the Cassanance region of Senegal, was sensuous and hypnotic, alternating a vocalist with a woeful tenor sax in the center of the stage.
The B99s created a vivid sense of the recording venue. This was evident listening to the L.A. Four's Going Home (Ai Music 3 2JD 10043). The instruments were spread before me in a large arc: Laurindo Almeida's guitar to the left, Ray Brown's standup bass at center, Bud Shank's alto sax and flute to the right, and Shelly Manne's drum kit at center rear. The B99s totally "disappeared," leaving the sonic holograms of four musicians on a virtual soundstage.
Vocal solos blossomed with ambience, imaging, and the rich timbres of the human voice. Listening to "Brother, Can You Spare a Dime?" from Strike a Deep Chord: Blues Guitars for the Homeless (Justice JR003-01), I could easily discern the virtual images of the two singersDr. John and Odettasinging alternate choruses. On "Lord, Make me an Instrument of Thy Peace," from Requiem (Reference RR-57CD), the layered-in-space voices of the Turtle Creek Men's Chorus and the pipe-organ accompaniment gave me the sense of a huge performance hall. José Carreras' clear tenor voice had a liquidity and immediacy that were uncanny as he sang the "Kyria" from Ariel Ramirez's Misa Criolla (Philips 420 955-2). When I heard Harry Connick, Jr.'s performance of "Don't Get Around Much Anymore," from the When Harry Met Sally... soundtrack (Columbia CK 45319), I was struck by the natural vocal timbre with no sign of honk. The B99s also rendered the most natural, spacious acoustic of Robert Silverman playing Beethoven's "Moonlight" sonata (Orpheum Masters KSP830) that I have ever heard.
The B99s maintained their liquid midrange and extended highs up to moderate volume levels. Yet I had to be careful to keep the Bryston 14B-ST's clipping indicators from flashing. When they did, the soundstage flattened and narrowed, as heard during the explosive opening timbales solo on "Tito," from Arturo Sandoval's Hothouse (N2K 10023). In this respect, the Burmesters lacked the Revel Salons' resistance to high-level compression. I also detected loss of three-dimensionality and microdynamics at top volumes during the drum solo that ends "Like LT," from Patricia Barber's Companion (Premonition/Blue Note 5 22963 2), and the over-the-top percussion solo at the end of "The Maker," from Emmylou Harris' Spyboy (Eminence EM 25001-2). But this is a silly criticismthe B99s never distorted, a major feat when my SPL meter was registering peaks of 105dB at my listening chair. The B99 was designed to be a home loudspeaker, not a disco monitor.
The Burmester Audiosystems B99 blew my socks off. My listening notes read like an audiophile's anthem: lucidity, transparency, ambience retrieval, jewel-like build quality, the capacity to "disappear," superb imaging, great timbral detailing. These babies were more transparent than any speaker in recent memory. Their soundstage, three-dimensionality, and big sweet spot increased my pleasure and prolonged the review. I was sad to see them start on their long journey back to Berlin.
Yet there were a few things I didn't love. Talk about sticker shock! $47,000/pair exceeds the MSRP of a new Porsche Boxster. I'm sure Burmester sells every B99 it builds, but spending this much for a speaker that won't be as tall as many of its owners won't wash in most households. For this price, I'd want more tautness in the bottom octave, as I've heard from the Snell XA Tower References, and a bit more resistance to high-level compression when I really want to get down.
And no matter how I tried, I couldn't learn to love the location of the speaker posts. I didn't want to wait for help in changing speaker cables during my auditioning, but reason always intervenedas much as I loved the B99's transparency, I didn't want to be flattened under it.
Still, that seductive transparency brought back memories I hadn't experienced for a long time. I never knew it was possible to capture the lucidity and transparency of a Quad 57 in a pair of dynamic speakers that could handle the full output of a Bryston 14B-ST and still image like bandits. My hat's off to you, Dieter Burmesteryou've created an object of sheer beauty, both to listen to and to gaze at.
Sidebar 1: Specifications
Description: Three-way, floorstanding, reflex-loaded loudspeaker with double-walled enclosure, milled and enameled aluminum front panel. Drive-units: 5" by 1" ribbon tweeter, two 5.5" (140mm) magnesium-cone midrange units, two 9.5" (245mm) paper-cone woofers. Crossover frequencies: 180Hz, 1.8kHz. Crossover filters: second-order Linkwitz-Riley. Frequency response: 32Hz-28kHz, ±3dB. Power rating: 400W. Impedance: 4 ohms nominal, 3 ohms minimum. Sensitivity: 90dB/W(2.83V)/m.
Dimensions: 58.3" (1495mm) H by 12.1" (310mm) W by 24.2" (620mm) D. Weight: 220 lbs (100kg) each.
Finishes: Silver-metallic enamel laminate front and side panels; enclosure comes in rowan berry, high-gloss black, or maple trim.
Serial numbers of units reviewed: 12385, 12386.
Price: $47,000/pair. Approximate number of dealers: 9.
Manufacturer: Burmester Audiosystems GmbH, Kolonnenstrasse 30g, D-10829 Berlin, Germany. Tel: (49) 30/78 79 680. Fax: (49) 30/78 79 68 68. US: Burmester USA, 229 Arbor Road, Franklin Lakes, NJ 07417. Tel./fax: (201) 848-7700. Web: www.burmester.de.
Sidebar 2: Dieter Burmester chats with Larry Greenhill
Larry Greenhill: When did you start building audio products?
Dieter Burmester: I have been an audiophile and musician since age 14. I played guitar in clubs every weekend and later studied electronics at the university. After my education, I went into business making electronic sensors for medical diagnostic systems that ran automated blood tests. I owned Quad electrostatics driven by a Quad 22 amplifier. The amplifiers broke often because the tubes didn't last.
I decided to build my own amplifier in 1977, using the precision components and circuit parameters used in my medical sensor electronics. These circuits used extremely low currents and voltage. A magazine in Germany heard about the amplifier, scheduled it for review, and praised its sonics. Soon there were customers and dealers. I persuaded two friends to join me, and we began to manufacture audio electronics 25 years ago.
Greenhill: Does the ribbon tweeter account for the B99's high level of transparency?
Burmester: It's not just the ribbon tweeter, but the entire loudspeaker works together as a system. I believe the enclosure construction, which uses a double wall separated with an inner lining, helps greatly. The sonic resonances can't come through the enclosure walls, so the housing is entirely quiet. Many other high-end systems have clean, precise, transparent low frequencies, but they don't transmit the real power of the instruments. The goal of my speakers is to convey the real substance of the music. That's why I believe that you can hear the difference of our loudspeakers even in the next room.
Greenhill: Any new directions for the company or new products under development?
Burmester: Burmester is now working on a home-theater system and a DVD player. This system will be a rack system that will be beautiful and be accepted by the wives. It will include a center-channel speaker, subwoofers, and the B99s. In addition, we are designing the audio system for the $1 million Bugatti sedan. Besides our audio gear, the car has an 1100hp engine and goes over 400kph!
Sidebar 3: Associated Equipment
Analog source: Linn Sondek LP12 turntable with Lingo power supply and Ittok tonearm, Spectral moving-coil cartridge.
Digital sources: Krell KRC-28 CD transport, Sony SCD-C555ES multichannel SACD player.
FM tuners: Day-Sequerra FM Reference Classic, Rotel RH-10, Magnum Dynalab MD-102 with 205 Sleuth RF amplifier, Fanfare FT-1A.
Preamplifiers: Krell KCT, Sony TA-P9000ES, Mark Levinson ML 7A with L-2 phono section, Conrad-Johnson Premier 18LS, Margulis and Duntech MX 10 MC phono preamplifiers.
Power amplifiers: Mark Levinson No.334, Krell FPB 600C, Bryston 14B-ST and 9B-THX (5 channels).
Loudspeakers: Dynaudio Contour 3.0, Revel Ultima Salon, B&W 805 Nautilus (rear surrounds), Mirage HDT-FCH-1 (center), Velodyne HGS 18 subwoofer.
Cables: Digital coax (75 ohm): Silver Starlight, Ultralink. Interconnect, balanced: Krell CAST, Bryston, Krell Cogelco Yellow, PSC Pristine R-30 silver alloy. Single-ended: Randall Research, Mark Levinson HFC (with Camac connectors), Totem Acoustic Sinew, Coincident CST Interface, Ultralink Performance Audio. Speaker: Burmester LN (low and mid-hi range), Levinson HFC 10, PSC Pristine R50 biwired double ribbons, Ultralink Excelsior 6N OFHC, Coincident Speaker Technology CST 1.Larry Greenhill
Sidebar 4: Measurements
Stereophile's reviewers seem to be currently enamored of large, heavy loudspeakers. As with the 270-lb B&W Signature 800 that Kalman Rubinson reviews elsewhere in this issue, it was not possible for me to lift the 220-lb Burmester B99 off the ground for the acoustic measurements. As a result, there was an unavoidable "floor bounce" of the speaker's output that contributed some visible roughness to some of the frequency-response graphs.
I must also comment on the "thinking out of the box" that led Burmester to place the terminals in a recess on the speaker's base. Try as I might, I just couldn't hold the speaker with one hand while I inserted the wires with the other. Of course, at this price level the dealer should do all the work during the speaker's installation, and it could also be fairly pointed out that reviewers are not typical in the amount of plugging and unplugging they do. Nevertheless, I could be heard to let loose with the occasional uncharacteristic cuss word during the measuring session.
Once the cables were hooked up, I estimated the B99's voltage sensitivity as 89.5dB(B)/2.83V/m, which is within experimental error of the specified 90dB. This is a useful 3dB above average. The plot of the speaker's impedance magnitude and phase against frequency (fig.1) reveals the B99 to be moderately difficult for an amplifier to drive, due to a drop to 3.33 ohms in the midrange. However, the electrical phase angle is generally low, meaning that a good amplifier rated at 4 ohms will have no difficulty coping with the speaker.
Fig.1 Burmester B99, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)
In the region covered by the ribbon tweeter, the speaker resembles a 7 ohm resistor. Other than a very slight kink at 190Hz, there are no glitches in the impedance traces that would reveal the presence of mechanical resonances. In fact, the B99's enclosure was as dead as the proverbial door nail.
The minimum at 32Hz in the magnitude trace indicates the tuning of the reflex ports, which in turn implies good bass extension. This is confirmed by the plot of the speaker's low-frequency nearfield responses (fig.2). The blue trace is the complex sum of the outputs of the midrange units, woofers, and ports, and can be seen to smoothly roll off with a somewhat overdamped character, reaching a -6dB point at 35Hz. Note that the usual notch in the woofer response at the reflex tuning point is almost absent. As a result, the overall high-pass rolloff is closer to 12dB/octave than the typical reflex system's 24dB/octave. As I explain in the "Measurements" Sidebar that accompanies the B&W 800 review, this type of woofer alignment tends to give, in all but very large rooms, the optimal balance between low-frequency extension and clarity.
Fig.2 Burmester B99, nearfield responses of midrange unit (magenta), woofers (green), port (red), and their complex sum (blue), plotted below 800Hz, 1kHz, 400Hz, and 800Hz, respectively.
The ports' output (red trace) covers the passband between 25Hz and 60Hz, but an otherwise smooth low-pass rolloff is spoiled by the presence of a sharp peak at the same 190Hz seen in the impedance traces. Fortunately, the woofers' response (green) has a suckout at exactly the same frequency, which is why the summed (blue) response is smooth. The crossover between the midrange units and woofers appears to be set slightly lower in frequency than the specified 180Hz, and features symmetrical 12dB/octave slopes.
The same summed nearfield low-frequency curve is shown to the left of fig.3, spliced to the B99's farfield response averaged across a 30 degrees horizontal window on the tweeter axis. It is astonishingly flat, overall! The lack of the usual 3dB "nearfield boost" in the mid- to upper bass, however, suggests that the woofer alignment is perhaps a too overdamped. I note that LG found the speaker's bass to roll off below 25Hz, even with the usual low-frequency "room gain."
Fig.3 Burmester B99, anechoic response on tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with the complex sum of the nearfield responses plotted below 400Hz.
The ribbon tweeter's output appears to roll off sharply above 11kHz or so, which, all things being equal, might be expected to make the speaker's sound lack upper-octave "air." Yet as LG commented on the plentiful air to the B99's balance, perhaps all things are not equal. The missing factor is the speaker's dispersion. Fig.4 shows the B99's lateral radiation pattern (plotted out only to ±15 degrees because I could not maneuver the speaker onto my computer-controlled turntable). The audioband balance doesn't change at all within this window, and the top octave starts to roll off only at the most extreme angle. However, as the output is well-suppressed at the 15 degrees off-axis angles, I suspect that these responses contribute significantly to the rolloff above 11kHz seen in fig.3.
Fig.4 Burmester B99, lateral response family at 50", from back to front: differences in response 15 degrees-5 degrees off-axis, reference response on tweeter axis, differences in response 5 degrees-15 degrees off-axis.
The B99's dispersion in the vertical plane (fig.5) features a sharp notch at the upper crossover frequency for standing listeners, but the response doesn't change significantly as long as the speaker is auditioned on an axis between the centers of the two midrange units. (Ignore the smooth rise above 15kHz in the second trace from the bottom, which I believe is due to an averaging error when I took the measurement: I measure outdoors, and minuscule differences in path length due to slight breezes can lead to such errors.) At extreme off-axis vertical angles, the ribbon's output is well-suppressed in the top two octaves, due to its radiating dimension in this plane being very much greater than the wavelengths of the sound in this frequency region.
Fig.5 Burmester B99, vertical response family at 50", from back to front: differences in response 20 degrees-5 degrees above tweeter axis, reference response, differences in response 5 degrees-10 degrees below tweeter axis.
In the time domain, the B99's impulse response (fig.6) is conventional and clearly shows the unavoidable floor reflection 3ms after the initial pulse. This reflection can also be seen in the step response (fig.7), but more important, this graph reveals that both tweeter and midrange units are connected in inverted acoustic polarity. The woofers, however, whose contribution can barely be made out at the far right of the graph, are connected in positive acoustic polarity.
Fig.6 Burmester B99, impulse response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.7 Burmester B99, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Finally, the B99's cumulative spectral-decay plot (fig.8) is superbly clean. Note that the presence of the floor reflection meant that I had to aggressively window the impulse response to produce this graph. The area where this windowing results in invalid data is shown dotted; fortunately, the B99's treble output has already dropped below the graph's floor long before this point.
Fig.8 Burmester B99, cumulative spectral-decay plot at 50" (0.15ms risetime).
Overall, this is superb measured performance for which no excuses need be made.John Atkinson