Karl Suager
|
LCR-55
Satellite Speaker, Suggested Retail Price: $225
each V-75 Mark II Powered Subwoofer,
Suggested Retail Price: $625
each |
| Miller & Kreisel Sound Corporation, 10391 Jefferson Blvd.Culver City, California 90232; Phone (310) 204 2854; FAX: (310) 202 8782 Product Info via FAX-back: (800) 414 7744; E-Mail [email protected]; Web www.mksound.com |
While wandering about one of the main floors at last winter’s CES, I fell into the M&K room and saw speakers that I didn’t recognize perched on the wall. They weren’t weird enough to start up a conversation, but I took some notes, got some lit, and intended to follow up on it later. Well, now is finally later, and I wish I’d done it earlier. M&K also sent an accompanying subwoofer to complete the system, the V-75mkII.
On arrival, car keys flashing to rend tape from cardboard, I finally got a close and complete look at the LCR-55. Pulling a single satellite out of the box I thought to myself, "Now this is nice." It doesn’t reek of exotic materials. The small, black, vinyl-laminated box wears beveled front edges and standard 5 way binding posts. Although the cabinet lets out a well-damped thuddish click when knocked by the knuckle, solid enough to cause a good head injury with a little velocity, the grille caught my attention the most. It’s simple - a bent sheet of perforated metal, bordered by strips of rubber above and below, which grips the inside of the cabinet lips to elicit an intentional elegance, resembling the stator of an electrostatic panel. The spiffy grille does provide some very functional services for those who share their abode with other life forms.
For instance, I live with a cat, a dog, and a child in addition to my beloved. The cat has learned via squirt bottle and Scotch Tape to keep her claws on the room treatment panels (better than my speakers!), and the dog chews on books when not tormenting the cat. The child, however, not only chews on any interconnects I leave around, but has expanded her abilities to pushing buttons and/or anything that resembles one. Though I’m proud that she could use the remote control before she figured out how to walk, tweeters and woofers don’t usually like this kind of attention and, to be honest, it just bugs me. But with the avant-garde protector, prod as she might, ain’t no way she’s touching the drivers on the LCR-55s. What’s more, with cabinets pre-drilled for omni-mount brackets, one could mount the speakers to the wall so that the benefits of the grille could be limited to those of cosmetics.
The V-75 mkII subwoofer is not so staunchly equipped with armor and body. Although similar in cabinet styling, its grille is of the material variety. Fortunately, as with my own M&K S-85 satellites which have cloth grilles, my daughter contented herself with merely picking at the M&K logo, and subsequently putting it in her mouth and, after I removed it from that orifice, crying. The V-75 mkII isn’t as inert in construction either. But with subwoofers, so long as the frequency of cabinet resonance is safely above the operating range of the system, any flexing induced by the pressure of the driver will only contribute a small loss in output instead of coloring the sound. Since M&K intended this as an entry level system, I can’t really gripe about it.
This brings up an interesting point about enclosure damping that I’d like to get out of the way. Most enclosures have resonances, by virtue of dimensions and material, somewhere in the lower mid-range. Enclosure resonance may make bass lines unclear and vocals muddy. Several approaches can alleviate this problem. One way is to damp the heck out of it, trying to absorb energy before the surface of the enclosure radiates it into the outside air. Another method is to make the cabinet stiff with bracing (also inadvertently adding damping) and hope that it reduces resonance by minimizing flexure of the cabinet walls. If done intelligently, bracing can spread out resonances to make them less noticeable, but it also raises their respective frequencies of excitation, possibly making them more audible. There’s another technique which works remarkably well when combined with these two.
Cabinets will not resonate until they’re provided with a force at one of their resonant frequencies (they’ve got multiple ones) and only then generate harmonic coloration. So, if you keep a driver from operating at those frequencies via a crossover network, it limits coloration. Also, because the SPL radiated into the air is a direct result of surface area, smaller cabinets with the same amount of vibration will emit less coloration.
Therefore, a designer may use not only a combination of damping and bracing, but also make separate enclosures for drivers that require a lot of volume (woofers) and limit the output of those drivers to frequencies that will not excite their own enclosure resonances. Then, they may house the drivers that will inevitably excite resonances (mid-bass drivers) in smaller, well-damped enclosures. I’ve seen a few very clever variations of this in full-range speakers, but nothing epitomizes the technique like the subwoofer/satellite concept.
Satellite/subwoofer systems do make a lot of sheer performance sense also, especially in a home theater application. Since a subwoofer is pretty much the most direct and cost-effective method of getting deep bass, it’s almost mandatory. And, if you’ve already got a subwoofer to reproduce bass, you may allocate resources destined for the other speakers without having to compromise accuracy for extension. Sure, it’d be nice to have truly full-range speakers all the way around, but when you get into the logistics of room décor, it’s just not practical. And, with room acoustics, subwoofer/satellite systems have an advantage in that placement of the satellites for the best imaging does not conflict with the placement of the subwoofer for optimal bass response, making the setup far easier. In exchange for effort and money spent, a separate dedicated subwoofer can give you more value in terms of dynamic output, low frequency extension, and flat room response.
That isn’t to say that relatively full-range speakers, with their own bass extension, don’t provide a slight advantage when paired with a subwoofer, or a pair of subs. With an active crossover, you have the option to tailor their response to best match both the room and the subwoofer. In a no holds barred arrangement, I prefer to get the main speakers to go down to as low as their dynamic capabilities and room acoustics will allow, usually between 35 and 50 Hz, and hand off to a pair of stereo subs from there. Even though bass below 80-100 Hz is pretty much omni-directional, that doesn’t mean that there aren’t subtle spatial cues to be rendered. Monaural bass can work pretty well, but it loses a degree of spaciousness and hence, realism. On the other hand, not that many recordings actually have stereo bass in the nether regions.
Also, a good loudspeaker with a 10" or 12" woofer capable of output to 30 Hz will take a nice yawning stroll at 80 Hz. So, even if you’re not using the full extension of a full-range speaker, there is an advantage just to have it there. But, does it give you the best performance for money spent? Not at $450 a pair it doesn’t, as it inevitably requires a bigger and more solid cabinet (larger surface area) bigger (and usually more) drivers, and tends to compromise the upper range to satisfy the lower. That’s the case with all speakers, but it’s a matter of degree. A $4,000 pair of full-range speakers doesn’t need to sacrifice much in the midrange or treble to get decent bass. I can’t think of a way that a $450 pair of speakers can get halfway decent bass in the first place, let alone good midrange/treble performance on top of it. Even at the $4,000 level, though, I don’t know of any speakers which will outperform a reasonably solid $1,500 subwoofer in output and extension capabilities.
Design Notes & Observations
The V-75 mkII subwoofer isn’t particularly innovative, but rather a simply manufactured, well-thought out design. M&K created a decent driver to put in a moderately sized enclosure with enough amplifier power to make full use of the excursion capabilities of that driver. Then, they provided a crossover which uses an adjustable 18 dB/octave filter giving a sharp enough slope to keep interaction with the satellites minimal while maintaining a realistic possibility of a good flat summation of the two responses (satellite and subwoofer). In addition to the adjustable filter, they added another 18 dB/octave filter at 125 Hz to further limit higher frequency content which might tip off the subwoofer’s location. Throw in a little EQ and a limiter to pull more extension out of the driver, yet protect the driver from eating up excursion too quickly, and voila! A high performance subwoofer at a modest cost.
Somebody’s probably thinking, "Hey, it’s only 75 watts!" If you’ve already read my recent article about bass reflex, you’re familiar with features of sealed vs. ported enclosures. Although it’s easier and more cost-effective to build sealed systems within close tolerances and they have useable output below cutoff, there’s also a hard limit on output dictated by surface area and excursion of the driver. Even with 1,000 watts, it won’t do you much good if the driver is bottoming out. What most people don’t realize is that even large drivers, because of their displacement limitations, can only handle a handful of watts at very low frequencies (servo-controlled designs differ slightly in power requirements). So, even though it’d be nice to have more power, and large power supplies generally do contribute to better bass, 75 watts may be entirely adequate for the purpose of filling a medium-sized room with a satisfying rumble, especially when the design is optimized and carefully thought out in every way. Such is the case with the V-75 mkII.
The LCR-55 satellites are pretty conventional too. They use shielded drivers with well-damped diaphragms (soft-dome tweeters, polypropylene mid-bass drivers with butyl surrounds) designed for low harmonic and IM distortion. The crossover utilizes air-core inductors which have a very beneficial characteristic in that they don’t saturate like iron-core inductors can. Air-core inductors must use more wire, and suffer a little loss of efficiency because of this, but that can be easily compensated with a few extra watts. The crossover alignment appears to be a third order (18 dB/octave) variety. Guessing it’s a Butterworth alignment where the output of both drivers is down 3dB at crossover, and phase shifted 270 degrees so that they sum flat instead of providing a 3 dB boost due to constructive interference, it seems like a good call. While giving a steep slope to ease demands on the drivers, it also makes possible both a flat power response and a flat on-axis response so that they can be accurate not only straight ahead, but also in terms of total energy put into the room.
I took an impedance measurement of the LCR-55. All M&K satellites are rated at a nominal 4 Ohms, but the LCR actually comes closer to 6 on average. I don’t blame them for calling it 4 Ohms though. The impedance peaks at the 85 Hz woofer resonance of 17 Ohms, but drops as low as 3.75 between 200 Hz -300 Hz where a lot of energy from dynamic peaks will likely hit, and then gradually rises to 6 Ohms at 1 kHz and above. This indicates that although the dip in the mid-bass assures that the load is no cakewalk, neither is it a nightmare. In fact, at modest output levels, it should work fine with some of the better mass market receivers. But, I also measured a sensitivity of 85 dB/2.83volts (1watt@8Ohms), which shows a relatively low voltage sensitivity. Combined with the somewhat difficult impedance, these little power hogs will benefit substantially from a dedicated power amplifier. Most real loudspeakers do.
Listening
But the proof is in the pudding, isn’t it? Too make it short, once I invested the time to set it up properly, the LCR-55/V-75 mkII system had a lot to offer. Coming off a nasty head cold, I gave myself a shot of "Contact". Nothing like a good jolt of 5.1 and Jodie Foster to clear out the sinus passages. The crash boom bang effects with Dolby Digital were fun, showing off the clean dynamic capabilities of these little buggers. But, I appreciated the agility with human voice most. Even though I could turn it up, it wasn't required in order to catch the dialogue. While some speakers intended for surround use often have a zingy "in your face" character to quickly impress, and many others intended primarily for music have a homogenizing smoothing effect to guarantee "musicality," and recess parts of the musical spectrum in order to unilaterally simulate a sense of depth, the LCR-55s did neither. Straightforward, sometimes bluntly so, what they give is pretty much what they get, without a lot of commentary.
Somewhat ironically, under certain circumstances, the LCR-55/V-75II system resembled my Infinity Ren 90s, which are based on planar ribbon mid-range and treble drivers. Aside from a small difference in clarity and depth, they sounded remarkably alike - clean, open, focused, and uncharismatically neutral. At first it seems strange, as they’re based on very different styles of drivers, until you take into account the details. Uh oh, here comes another tangent. If you’d like to skip this part, I’ll understand. Just scroll down to where it says end of tangent.
Ribbons and electrostatic panels are often regarded for their perceived speed, sometimes "explained" by the almost negligible, and easy to accelerate moving mass. They may be thought to have superior transient response to conventional drivers, therefore difficult to blend with their cone counterparts when making either a hybrid design, or matching to a subwoofer. This isn’t the case.
A lighter object will accelerate faster, given the same force. But, if it is moving faster, and at same frequency, it only results in higher output. For instance, a 12" cone woofer playing 100 dB at 200 Hz is going faster than a panel playing 90 dB at 200 Hz. Actually, a woofer would have less surface area than an electrostatic panel or large ribbon, which means that it would require more excursion at the same output levels, which would then mean that the cone woofer is really faster in absolute terms than the panel.
Many have noticed, though, that panel speakers can be difficult to match to cone woofers, and quote differences in speed as the culprit. There are reasons why a cone woofer can be difficult to match to a panel, but they have more to do with dispersion characteristics of the drivers than their speed.
And what is speed anyway? There is a legitimate concern with the behavior of drivers at resonance when it comes to speed, but it's really an issue of phase response at a narrow frequency band. However, that characteristic (especially in sealed enclosures) is no different than an analog crossover network. As far as speed is concerned, you can have two other applications where speed can accurately be applied. One is how fast the membrane can start and stop. That's simply the ability to change direction quickly, which is a matter of high frequency bandwidth. There is a joke among DIY bass enthusiasts that a tweeter is a fast woofer. The second is the actual speed of the driver membrane moving back and forth, which is independent of frequency, but the integral of acceleration, which itself is a function of the mass and the force, and proportional to output. Both of these are irrelevant to the discussion of blending cone and panel drivers.
Ribbons and panels are significantly lighter than cones, but the efficiency of the motor structure in turning current into driving force is lousy. That’s why they tend to be less efficient than cone drivers (which use the iron in the basket to concentrate the flux in the gap, and have much higher inductance to generate EMF) despite the small membrane mass and sometimes large radiating area.
I too used to buy into the idea that that ribbons and electrostatics were inherently superior to conventional drivers because of their low mass. After all, they usually sounded more spacious and open. However, after listening to a lot of stuff, and learning a bit about how they work, it became apparent that the differences in sound are not necessarily attributed to driver technology.
I suspect that the real advantages of ribbon and electrostatic devices are in their simplicity. There's less to screw up. They still have to worry about damping standing waves on the membrane, like cone drivers, since they do flex, perhaps even more. But, the motor structure is so simple (a couple of metal grilles or sandwiched magnets) that one doesn’t have to worry at all about gauss density effects of the ferrous flux former or voice coil turn distribution. And, the relatively resistive impedance that makes ribbon drivers so lousy at generating magnetic force, makes crossover design and implementation much simpler. So, it seems to turn out practical advantages in obtaining good results if the designer is aware of what he’s doing in the first place.
As for the perceived sonic differences, there are plausible explanations beside speed. For one thing, panel drivers usually don't have much of a cabinet, if anything. This eliminates standing waves in the box, and box resonances themselves. Big advantage, but not inherent to the driver, and the cabinets can be damped and designed to minimize this coloration. The other thing is that planar drivers mounted without an enclosure usually have dipolar radiation, which makes the reflections of the room enhance the sense of ambiance, openness, depth, physical presence, and believe it or not, even the perception of detail. Again, not inherent to the drivers themselves, but a feature of dispersion patterns.
When it comes to the difficulty in blending ribbons or panels to woofers, these dispersion patterns can become problematic. Hybrid electrostatic panel/woofer combinations are inherently difficult in design, and at the mercy of the room, because the surface area and subsequently the dispersion of the transducers are so different at all but the lowest crossover frequencies. When drivers beam, the output falls off more slowly as the distance increases than drivers with wider dispersion, as that wide dispersion spreads out the sound pressure level over a greater area as a function of distance, and so decreases faster farther away. This causes frequency response anomalies that can make drivers with almost identical output at 1 meter very different at the listening position. At very low frequencies, it's easier to get a good match since both are pretty much a point source. However, most dipolar planar drivers don’t work very well at very low frequencies because 1) they have very limited excursion, and 2) their dipolar radiation pattern causes an extra 6 dB roll-off at a frequency whose wavelength is 4 times the width of the baffle, requiring even MORE displacement.
In executing a hybrid design with dipolar ribbons and/or electrostatic panels, dipolar woofers are ideal, except that it requires a helluva lot of them to get any real output (like in JEJ’s Carver Platinums) since much of the bass tends to cancel itself out. On a more practical level, bipolar woofers could blend relatively nicely with the appropriate crossover that would induce an equal phase shift between the output of the drivers both front and back, and sum flat both ways on axis. A good example of such an implementation is Carver's AL III which does essentially the same thing by firing a single woofer downward. It not only facilitates room loading, but since the crossover frequency of 150 Hz isn’t otherwise omni-directional, it imposes an omni-directional dispersion pattern by squeezing the output off the floor. Although I think that the output quality at the higher range of the woofer may suffer a wee bit from this arrangement, that’s an intelligent, practical way to blend a conventionally loaded woofer with a dipolar ribbon.
All of this applies to the surprising similarity in sound between a speaker based on conventional dynamic drivers (M&K) and another utilizing planar ribbons (Infinity.) If you take into account the dispersion patterns, it makes a lot of sense. They're both speakers that are relatively flat on-axis and have point-source type, uni-directional, minimal lobing radiation patterns. This also probably explains why the ribbon midrange on the Infinitys blends with the cone mid-bass, not because of speed, but because of similar dispersion patterns at the crossover frequency.
END OF Tangent.
Getting back to the stars of this review. The LCR-55/V-75mkII system is pretty good all around. It can open a relatively spacious soundstage in either stereo or 5.1 while maintaining a good degree of precision, reveal a lot of detail without slamming it at you, and with a good match in an amplifier and source components/listening material, isn't excruciating to listen to. The Denon AVR-3200 worked very well with this system when using the internal digital crossover and digital inputs. The internal low/cut filter, which creates an active bi-amp system, cleared up the mid-range a little, but the difference wasn't huge. Using the analog inputs of the AVR-3200 instead of the digital inputs, with the addition of extra D/A and A/D conversion, the performance of the setup didn’t do much for me. It lost the openness and transparency that the 55s are capable of, making the speakers sound grainy and congested, though still not harsh. But, using the digital inputs, the combination was, in fact, quite impressive, something I’d very seriously recommend for the enthusiast on a moderate budget. To put it more directly, this is one of the few receiver/speaker system combinations designed for 5.1 under $3,000 that I’d want for myself.
Tied to the recently reviewed Audiolab 8000-LX driven by a vintage JVC XLZ 1050 CD player (pretty good actually, though it lacks the precision and silent background of the Myryad player auditioned awhile back) in stereo, my girlfriend actually offered a positive comment. She doesn’t usually bother with my audio interests aside from watching a movie or listening to the occasional Tori Amos/Smashmouth/No Doubt/Pachelbel CD. After returning from a trip at the local supermarket, she commented, "Now this is nice." Aside from the bothersome Déjà vu, that’s quite a compliment. To date, after HiFi’97 and last winter’s CES, the only things that really impressed her were the Cello 2-channel system, and the Martin Logan Statement/Krell reference system, both way out of my price range. She then immediately realized the implication, that I had overspent when purchasing my own equipment, and reassured me with, "but I still like yours better." I like mine better too, but they also cost three times as much and definitely don’t take kindly to mass market receivers, let alone many outboard power amps. Considering that their little brothers, the Renaissance 80s, once put a genuine workhorse, the Hafler 9500, into shutdown from thermal overload, the LCR-55s workable impedance should be considered somewhat an asset in itself.
But the LCR-55s don’t translate well with any old amplifier, let alone some halfway decent ones. I tried the LCR-55s with a Yamaha RX-V992, and while it still extracted the same level of detail, exuded a slightly raspy character, overly sharp with sibilants and generally fatiguing. The RX-V992 is a good piece with many speakers of the eight Ohm variety, so I concluded that the Yamaha just doesn't feel peachy with loads that dip below 4 Ohms, even when set for 4 Ohm speakers.
Another thing to remember, since the LCR-55s really are designed to work best as satellites, they pretty much require a subwoofer. You can use them as mini-monitors if you like, but it’s the bass that adds the finishing touches to realism, and they don’t have much lower-end crunch by themselves. Because of this dependence, the perceived quality can be greatly influenced by not only the associated equipment and the quality of the subwoofer, but also the output level and crossover setting. As a result, the lower midrange could come off as either warm and chesty, or anemic and thin, depending on how the V-75mkII belted out the lower octaves. It takes some experimentation, a lot actually, so keep in mind if you take on an audition that you’re in for some exercise.
As for the V-75mkII, it’s not up to competing with the bad boys in the $1,500 range and above, including some of the bigger push-pull offerings from M&K, as well as designs from other manufacturers. But what do you want for $625? Quality? Well, the V-75mkII has that. It keeps a good handle on control, doesn’t get in the way, and will likely extend the useable response of all but the deepest full-range speakers while offering the flexibility of a dedicated bass system. Its strengths are considerable and it doesn’t have any blatant flaws. I personally like my bass a little more damped, but that’s not always appropriate for home theater which usually asks for more heft, and the V-75mkII does have heft without booming. It far exceeds the performance of your typical entry-level sub which usually sounds like a basket full of mud. It’ll slap thunder, no doubt. It just can’t stop your heart like the giants can.
Combined as a system, this group not only performs near the higher-end of the value spectrum, but I think sits at the top with a select few. It’s not just good for the money, it’s good period. You can pay twice as much and get substantially worse (this is audio, you know.) If it were me, I might invest a little extra to get into one of their push-pull brutes that can really quake. Otherwise we might, after purchasing a system like this, forget about upgrading and get on with enjoying ourselves. This is one very cool little package.
Karl Suager
Associated Components used for the review:
Infinity Renaissance 90 Loudspeakers
Aragon 8008BB power amplifier
Passive controller w/50 k Nobel Pot
Denon AVR-3200 receiver
Yamaha RX-V992 receiver
DH Labs Silver Sonic interconnects & speaker cable
Monster Cable S-14 speaker cable (14 awg flexible zipcord)
Bybee/Curl prototype power purifiers and power cords
API Power Pack V AC line conditioner
JVC XL-Z1050 CD player
© Copyright 1998 Secrets of Home Theater & High Fidelity
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