===========
Rated Frequency Response: 60 Hz to 20 kHz, ±2 dB; +0,-6 dB at 35 Hz.
Recommended Amplifier Power: 25 to 150 watts.
Dimensions: 41 3/4 in. H x 8 in. W x 13 in. D (105.9 cm x 20.3 cm x 33 cm).
Weight: 35 lbs. (15.9 kg) each.
Finish: Satin black ash.
Price: $1,099 per pair.
Company Address: 400 Matheson Blvd. East, Unit 31, Mississauga, Ont., Canada L4Z 1N8; 905/507-0777.
===========
Quick: Which speaker company is Number One in sales in the United Kingdom? KEF? B&W? No, it's actually Mission, according to GFK, a leading statistics-gathering firm in the U.K. Mission was founded in 1977 and is now part of the Verity Group, which includes two other well-known U.K. speaker companies, Wharfedale and Quad.
Last summer I visited the plant where Mission manufactures its high-end loud speakers and electronics. I was extremely impressed with the production and ware house facilities, which operate with a level of automation, efficiency, and cleanliness that I have not seen in any other speaker plant. Farad Azima, Mission's founder, had the plant designed to be environmentally friendly, using natural resources sparingly and minimizing pollution.
Currently, Mission exports two lines of speaker systems to the United States, the recently introduced 73 series ($249 to $1,099 per pair) and the upscale 75 series ($800 to about $2,000 per pair), which has been on the market since early 1994. The company will soon add a completely revised and up dated Cyrus electronics line to its U.S. offerings, including amplifiers, preamps, CD players, and home theater components.
The Mission 735, at the top of the 73 series, is a tall, slender tower that contains four drivers: two 7-inch woofers, one 7 inch woofer/midrange, and a 1-inch tweeter. Although Mission describes the 735 as a three-way system, it is actually a modified two-way design with three identical woofers. The bottom two operate in a vented box, the top one in a smaller sealed chamber. All three work at low frequencies, while at higher frequencies the bottom two woofers are rolled off and the top woofer operates as a midrange driver up to the crossover frequency (specified as 3.2 kHz), where the tweeter takes over.
The 735's cabinet is made from medium density fiberboard; the front panel is 3/4 inch thick, and the rest is of 3/8-inch material. In addition to a shelf that divides the cabinet into two chambers, there's a single internal brace that connects the side panels in the larger bottom chamber, to minimize side panel vibration. Spikes are provided and can be screwed into the bottom panel of the cabinet.
-----Tweeter is partially decoupled from other drivers by the molded panel
design.
A custom-designed, injection-molded front baffle, made from a mica-loaded polypropylene, covers the front of the cabinet and, according to Mission, provides optimum acoustic loading for the drivers. The molded front baffle is also said to partially decouple the tweeter from the woofers, to reduce intermodulation distortion. The port, 2 3/4 inches in diameter and 5 inches long, is molded into the bottom of the panel. The port is flared at its exit to reduce turbulence, and it contains an internal strengthening vane that gives it a distinctive look. The grille frame, made of injection-molded plastic, attaches to the front panel with a combination of pegs and press-fit couplings.
The molded front panel looks like a single structure with separate mounting bezels for each driver. In fact, however, it is four interlocking subpanels with the bezels molded in. To gain access to the bottom woofer requires removing each of the three higher interlocking subpanels, which are fastened by a total of 16 screws. The port is on the bottom of the fourth subpanel. It took me several minutes and a lot of head-scratching to figure all this out! The three long-excursion, 7-inch woofers have see-through polypropylene diaphragms with rubber surrounds, mounted in stamped-frame baskets. A large ferrite magnet generates high magnetic flux for the 1 1/4-inch-diameter voice coil. The closed-back, Ferrofluid-cooled tweeter is a ring-radiator design with a 1-inch metal/polypropylene dome. The dome it self is covered by a protective metal screen.
The 735 employs what Mission describes as a "straight-path crossover network [that] minimizes component-induced distortion, which would otherwise color complex, dynamical pas sages." The crossover is wired point-to-point and mounted on the back of the input connection cup, at the bottom of the rear pan el. It contains just four components: one resistor, two ferrite-core inductors, and one capacitor, all of high quality. Connections between the crossover, drivers, and input panel are made with 18-gauge stranded wire. The wire is soldered to the crossover and connected to the drivers with clips.
The bottom two woofers, which are connected in series, are fed through a large inductor that forms a first-order low-pass filter at about 260 Hz (the-3 dB point, as determined by electrical measurement). The top woofer is fed by a much smaller inductor that forms another first-order low-pass filter, at a higher frequency. The tweeter is driven from a series resistor-capacitor network forming a first-order high-pass filter. No driver-impedance compensation net works are used. At low frequencies, all three woofers operate together, with the top woofer in parallel with the series combination of the bottom two.
Input connections are via a pair of five-way binding posts on the bottom rear of the cabinet. The terminals are spaced 1/4 inch apart, so standard double-banana plugs will work. The two sets of terminals normally are linked by straps that can be removed for bi-wiring or biamplification. Wire up to 1/8 inch in diameter (10-gauge) can be accommodated by the terminals.
Measurements
The Mission 735's on-axis anechoic frequency response is shown in Fig. 1. Measurements were taken 2 meters from the front of the cabinet, on an axis between the woofer/midrange and the tweeter, 4 inches down from the top of the cabinet. A signal of 5.66 volts rms was applied (equivalent to 4 watts into the rated 8-ohm nominal impedance) and then referred back to I meter with a 2.83-volt rms input (equivalent to 1 watt into the rated 8 ohms). I used a combi nation of ground-plane and elevated free-field measurements to derive the curve shown, which was averaged with a tenth-octave filter.
Fig. 1-One-meter, on-axis frequency response.
Fig. 2-0n-axis phase response, group delay, and waveform phase.
Fig. 3-Energy/time response.
Fig. 4-Horizontal off-axis frequency responses.
Fig. 5-Vertical off-axis frequency responses.
Fig. 6-Impedance.
Fig. 7-Complex impedance.
The curve in Fig. 1 is fairly smooth, with minimal roughness. It fits a fairly tight, 7-dB, window (+3,-4 dB referenced to 1 kHz) between 55 Hz and 20 kHz. The over all curve's level drops somewhat above 2 kHz, with two moderate dips at 2.2 and 8 kHz and a peak at 12 kHz. Below 2 kHz, the curve is flatter, with a slight rise between 80 and 500 Hz and a hump between 1 and 2 kHz. Below 50 Hz, the response rolls off at about 12 dB/octave. With 90 dB as a reference, the response is 3 dB down at 55 Hz and 6 dB down at 45 Hz. Below 8 kHz and above 10 kHz, as you can see in Fig. 1, the grille causes only minor response variations. Between about 8 and 10 kHz, however, the grille reduces the response some 3 to 4 dB.
The Mission 735's sensitivity, from 250 Hz to 4 kHz, averaged out at 90.5 dB, just slightly above the manufacturer's 90-dB rating.
The right and left speakers matched fairly closely, ±0.75 dB from 100 Hz to 20 kHz.
Figure 2 shows the phase and group-delay responses of the 735, referenced to the tweeter's arrival time. The phase curve is quite smooth and well behaved. Averaged between 500 Hz and 3 kHz, the group delay indicates that the woofer/midrange output is delayed behind the tweeter's by about only 0.25 millisecond. The delay is due to a combination of electrical delay through the crossover and physical misalignment of the drivers' acoustic centers.
The waveform phase curve in Fig. 2 primarily indicates that waveforms will not be preserved over any significant bandwidth.
(This is typical of all but the handful of speakers specifically de signed to maintain near-constant waveform phase.) Only between about 400 Hz and 1.2 kHz does the waveform phase stay near zero, which means that waveshapes may be preserved somewhat, in positive polarity, for signals band-limited to this range. The jumps in wave form phase at 90 Hz and 5.1 kHz result from the way the curve is plotted, not from any discontinuity in the speaker's response.
Figure 3 shows the 735's energy/time response. The test parameters accentuate the speaker's response from 1 to 10 kHz, which includes the upper crossover region. Although the main arrival, at 3 milliseconds, is quite sharp and narrow, it is followed by lower-level arrivals, 21 to 22 dB down and delayed about 0.2 to 1.2 milliseconds.
Fig. 8-Three-meter room response.
Fig. 9-Harmonic distortion for E1 (41.2 Hz), with woofer/midrange connected (A) and disconnected (B).
Fig. 10-Harmonic distortion for A2 (110 Hz).
The 735's horizontal off-axis responses are shown in Fig. 4. (The bold curve at the rear of the graph is on-axis response.) These curves are quite well behaved and exhibit no high-frequency rolloff above 10 kHz in the main listening window, within ±15° of the forward axis. The good curve to-curve uniformity indicates broad and even horizontal distribution.
Figure 5 shows the vertical off-axis responses. (The bold curve in the center of the graph is on-axis response.) In the main listening window, ±15° from the forward axis, the response is quite uniform on and above the axis. Below the axis, however, there is a hole in the vicinity of the crossover frequency, between 3 and 7 kHz (not clearly seen in the graph). This indicates that the woofer/midrange and tweeter are partially out of phase through this range. Fortunately, the directional lobe at crossover points up rather than down. My comparison of on-axis responses, with nor mal and reversed tweeter polarity, revealed that the crossover frequency was closer to 5 kHz than the specified 3.2 kHz.
Figure 6 shows the 735's impedance magnitude. The impedance characteristic of a vented box shows up in the bass range, with peaks at 22.5 and 70 Hz flanking a dip at 34 Hz, the approximate box tuning. Uncharacteristically, however, the lower-frequency impedance peak is far lower in amplitude than the upper peak. This is because the bottom two vented-box woofers operate in parallel with the top woofer, which is in a closed box. The dissimilar impedance characteristics of the two different loading methods causes the widely different peak amplitudes. The 735's overall impedance variation between 20 Hz and 20 kHz is a moderately high 5 to 1 (21.3 divided by 4.2). Cable series resistance should be limited to a maximum of about 0.06 ohm to keep cable-drop effects from causing response peaks and dips greater than 0.1 dB. For a typical run of about 10 feet, that would mean using 14-gauge (or thicker), low-inductance cable.
The complex impedance is plot ted in Fig. 7 over the range from 5 Hz to 30 kHz. Two large loops, corresponding to the impedance peaks at 70 Hz and 2.5 kHz in Fig. 6, dominate. The lower-frequency impedance peak at 22.5 Hz shows up as a small loop in the center left of Fig. 7. The minor impedance irregularities seen in Fig. 6 show up in Fig. 7 as very small loops at 208 Hz and 1.02 kHz. These very small loops are often due to internal acoustical or panel resonances of the speaker's enclosure.
A high-level sine-wave sweep revealed a fairly rigid cabinet. There was only one noticeable wall resonance (at 280 Hz), which involved the sides and top of the sealed chamber at the top of the cabinet.
The 7-inch woofers had a fairly generous excursion capability of about 0.4 inch, peak to peak, and they overloaded quite gracefully. I detected no dynamic offset at any frequency or drive level.
The high-level bass sweeps made it immediately apparent that the sealed-box woofer/midrange was not high-pass filtered and hence operated all the way down into the bass range. This was evident be cause this driver's excursion was significantly greater than that of the bottom two woofers all through the bass range. This made the woofer/midrange much more susceptible to overload, which generates distortion, and it would always reach its excursion limits before the bottom two woofers.
The unequal excursions are due to the series connection of the bottom two woofers, which cuts their individual voltage drives (and hence their excursion) by half, and to their vented-box loading. At high levels at the 34-Hz tuning frequency of the vented box (where the box loading minimizes cone excursion), the bottom woofers' excursion was hardly noticeable while the woofer/midrange cone moved considerably.
Fig. 11-IM distortion for A4 (440 Hz) and E1 (41.2 Hz).
Fig. 12-Maximum peak input power and sound output.
Figure 8 shows the 3-meter room response, with both raw and sixth-octave-smoothed data. The 735 was in the right hand stereo position and aimed laterally at the test microphone, which I placed at ear height (36 inches) at the listener's position on the sofa. The system was driven with a swept sine-wave signal of 2.83 volts rms (corresponding to 1 watt into the rated 8 ohm impedance). The direct sound and 13 milliseconds of the room's reverberation are included. Overall, the averaged curve is well behaved and balanced and does not exhibit any extreme peaks or dips. The averaged curve fits a fairly tight, 10-dB, window.
Prominent characteristics include a peak at 285 Hz followed by a dip at 340 Hz, both in the upper-bass (or lower-mid) floor bounce region. There's a slightly broader peak between 700 and 900 Hz.
Figure 9A shows the 735's E1 (41.2-Hz) harmonic distortion. Immediately evident are the high levels of distortion all the way to the fifth harmonic. Particularly high are the third harmonic, nearly 38%, and the fourth, almost 16%. When I was conducting this test, it was obvious that the woofer/midrange was causing most of the distortion because of its great excursion. At maximum power at E1 (20 volts rms, or 50 watts into the rated 8-ohm impedance), the woofer/midrange's excursion was past its limit, at about 0.45 inch (peak to peak), while the excursion of the bottom woofers was less than one-third as great.
The unequal distribution of power to the woofer/midrange and the bottom woofers prompted me to redo this test, this time with the woofer/midrange disconnected. I raised the input power by 3 dB, to 100 watts (28.3 volts rms), to compensate for the drop in acoustic output caused by the absence of the woofer/midrange's acoustic output. The results are shown in Fig. 9B.
Even at twice the power, the distortion is now considerably lower. The maximum distortion is only 11.1% at the third harmonic, and the fifth harmonic, at 1.4%, is very low. (The sixth harmonic was below the measuring floor of my analyzer.) With the Mission 735 connected normally and driven by a high-level sine wave at or above 15 volts rms (28 watts) in the bass range, the speaker sounded distorted and stressed.
However, with its woofer/midrange disconnected, it sounded quite clean and effort less, even at levels of 28.3 volts rms (100 watts) and higher.
As seen in Fig. 10, the A1 (110-Hz) harmonic distortion rises only to 4.4% second harmonic, 1.6% third, and 0.9% fourth. (Higher harmonics were below the floor of my test gear.) At this frequency, most of the distortion was again generated by the woofer/midrange. The A4 (440-Hz) harmonic distortion (not shown) was very low. It reached only 1.1% at the second harmonic and 0.7% at the third. (Maximum power was 50 watts for this test.)
Figure 11 shows intermodulation distortion versus power, a test using tones of 440 Hz (A4) and 41.2 Hz (E1) of equal power. The IM rises smoothly and reaches a moderate 14% at full power.
The 735's short-term peak-power input and output capabilities are shown in Fig. 12. (The input level was raised until the speaker sounded subjectively bad or the output waveform was quite distorted. I then calculated the peak input power by assuming that the measured peak voltage was applied across the rated 8-ohm impedance.) The peak input power starts somewhat low (20 watts), stays fairly low until 80 Hz (where it rises to 80 watts), and then rises rapidly to a plateau of about 900 watts between 200 and 800 Hz. At higher frequencies, the maximum peak input power rises rapidly, to about 3.5 kW, and then levels off.
Because the 735's ability to handle power was relatively modest below 100 Hz, I again disconnected the woofer/midrange and reran this test. That energized only the vented-box portion of the speaker, which contains the bottom two series-connected woofers. As can be seen in Fig. 12, the input power handling greatly increases between 20 and 125 Hz. At 40 Hz, it is 600 watts, almost 17 times higher than the 35 watts it had been previously, or 12.3 dB! The peak acoustic output will not increase this much, because the efficiency is lower at 40 Hz, by about 3 dB, when the woofer/midrange is disconnected.
However, the effective increase in output will still be about 9 dB, or eight times more power, a very significant amount! Above 125 Hz, the maximum output of the bottom woofers drops below that of the three woofers combined, because of inductor-core saturation.
The peak acoustic output is also shown in Fig. 12, with the speaker connected normally. With room gain, the maximum peak sound-pressure level starts at a usable 94 dB at 20 Hz and then rises rapidly to cross 100 dB at 30 Hz, 110 dB at 62 Hz, and 120 dB at 130 Hz. The output then falls just a little, to 119 dB at 630 Hz, before rising into the very loud range of 122 to 126 dB above 1 kHz.
If you judge the Mission 735's bass out put by the frequency at which the maxi mum output crosses the 110-dB SPL point (the lower the better), then this speaker is about two-thirds down the list of all systems I have tested. Yet even though it is fairly far down on the list, it is still ahead of such well-known speakers as the Thiel CS5 and Meridian D600. Operating the 735 with only the vented section working would lower the 110-dB point from 62 Hz down to about 37 Hz. The 735 would then be only one-third down from the top of my list.
Modifying the crossover to add a high pass filter to the woofer/midrange would make the 735 a true three-way system. The vented-box section would then operate unrestricted and not be throttled back by the woofer/midrange. This would also significantly lower the Mission's bass distortion and increase its maximum low-frequency output.
Use and Listening Tests
When the Mission 735s were delivered to my lab, I was pleasantly surprised by the lightness of the cartons, compared to some heavyweights I have reviewed lately. Mission provided handholds on the sides of the cartons (a nice touch), so it was very easy for me to carry them alone. These speakers were also very easy to unpack. Once unpacked, the speakers were again easy to move around, as they weigh only about 35 pounds apiece. It was also easy to hook them up, because their rear terminals are quite accessible.
My review samples were quite good looking. The cabinet's molded front panel was a definite plus, giving the speaker a fresh, up to-date look. Fit and workmanship were on a par with the best I've seen. The grille fit well and was easy to remove and replace, but the plastic frame appeared to be fragile and not very rigid; it may not withstand rough handling.
The spikes were easy to attach to and re move from the bottom of the cabinet. By virtue of the speaker's light weight, I could easily lift it off the floor, with the spikes attached, and reposition it. On my thick carpeting, the 735 was somewhat tippy, side to side, when the spikes weren't attached; applying a lateral force of only about 2 1/2 pounds on the top was enough to push the speaker over.
The 14-page instruction booklet is well written and very informative and covers the entire Mission loudspeaker line. The manual stresses that the speakers be subjected to a "running-in" period of 10 hours before you use them. I fulfilled this requirement by driving the 735s with a 10-volt rms, 20-Hz sine wave for 8 hours. The manual begins with a long list of "DO NOT"s, including an exhortation against the use of filters, tone controls, or equalizers. Other sections cover hookup, positioning, grilles, spikes, cables, bi-wiring, biamping, and ancillary equipment. A very useful technical section ex plains such terms as coloration, transient response, dispersion, and sensitivity.
The manual strongly recommends that all Mission speakers be placed 8 inches away from the wall behind them and that they should not be toed in or angled toward the listener. The distance from the side wall should be a minimum of 1 1/2 feet. I positioned the Mission 735s both where I usually place speakers, 8 feet apart and far from the rear and side walls, and also much closer to the wall behind them. I experimented with both straight-ahead and angled-in orientations, listening 10 feet away from the speakers. When the 735s were close to the front wall, the bass took on a woolly and somewhat loose character, so I did most of my subsequent listening with them farther out in the room.
Octave-to-octave spectral balance on pink noise was quite acceptable, but the 735s did exhibit some tonality. When they were canted in, I heard some midrange tonal changes when I stood up. These variations were reduced when the systems were aimed straight ahead, as recommended.
When I was sitting down, the sound was essentially the same with either aiming. On music, the sound was less direct and more reverberant when the speakers were aimed straight ahead. I preferred them canted in and did most of my listening that way.
------ Input terminals can be unstrapped for bi-wiring or biamplification.
Listening gear included Onkyo and Rotel CD players, Krell's KRC preamp and KSA250 power amp, Straight Wire cabling, and B & W's 801 Matrix Series 3s as comparison speakers. The 735s required 3 to 4 dB of attenuation to match the lower sensitivity of the 801s.
The first CD I listened to was one that I brought back from my trip to the U.K., a sampler of choral works sung by the King's College Choir of Cambridge, The Sound of King's (EMI Classics CDZ 7 628 2). With this choral material, the sound was full bodied and well balanced; overall, the 735s sounded quite similar to the B & W 801s.
The Missions were slightly less smooth in upper mids and highs as compared to the B & Ws, although not obviously so. Vocal sibilants were emphasized somewhat. On wide-range, complex orchestral music containing significant bass, the 735s made a very good account of themselves. They could be played loudly and cleanly when the material demanded it. However, on music containing high levels of low bass but without much else going on-such as the strong bass drum whacks on track I of Winds of War and Peace (Wilson Audio WCD 8823)--these speakers produced generous levels of bass, but with a character that was clearly distorted. Don't expect gut busting deep bass from the 735s. Yes, they can do justice to loud rock music, such as from Queen, AC/DC, and ZZ Top (I'm showing my rock 'n' roll age here). Although the 735s' bass was not as kicky as that of the 801s, I nevertheless found it quite satisfying.
On third-octave band-limited pink noise, the 735s did not generate any usable fundamental output in the 20- and 25-Hz bands; all I heard was distortion. They did come on fairly strong at 32 Hz, generating usable fundamental output but still with significant distortion. Close listening revealed that most of the distortion was coming from the woofer/midrange, as one would expect from the measurements. The story was much the same in the 40-, 50-, 63-, and 80-Hz bands.
The 735s did a worthy job on male speaking voice, with a character and balance quite similar to that of the 801s. Female vocals were also reproduced well. There was a bit of forwardness and sibilant emphasis, but the sound was very clean and had no harshness. Stereo imaging and soundstage re-creation were excellent. I heard just a slight forward movement of solo instruments. Stereo focus and stability of a mono center image were particularly good. Treble reproduction was crisp and clear, with good extension and no wiriness on orchestral strings.
The 735s' dynamic ability and quick transient response were readily apparent on Dean Peer's solo bass guitar on a super demo CD, U-cross (Fahrenheit FR 9403). These speakers' high sensitivity paid off well here.
In summation, the 735s performed admirably in most of my bench and listening tests. Only in bass capability did they pre sent a dichotomous picture. On one hand, the Missions did quite well with the majority of bass-heavy selections, particularly those coupled with wideband spectral con tent. On the other hand, they fared poorly with material having high-level content restricted entirely to very low frequencies. In other respects-dynamics, spectral balance, stereo imaging, transient response, dispersion, coloration, and naturalness--the 735s did a very credible job and should be seriously evaluated, particularly considering their reasonable price.
(Audio magazine, Jan. 1996)
Also see:
Monitor Audio Studio 10 Speaker (Equip. Profile, Jul. 1991)
NHT Model II Speaker (Jul. 1990)
Mission 776 Preamp (Jun. 1982)
= = = =