NHT Evolution Loudspeaker System

      NHT might be a loudspeaker company, but their design vision encompasses far more than just the loudspeaker. NHT utilizes a systems design approach, taking into account far more than just the loudspeaker itself. Specifically, NHT also includes in its systems design those portions of the playback system that are both before and also after the loudspeaker, and which influence the loudspeaker's performance as you hear it. Those additional elements are of course the electronics that precede the loudspeaker, and your listening room which follows the loudspeaker, since it is your room that literally plays to you the acoustic output of the loudspeaker, transforming the sound from the acoustic signal put out by the loudspeaker itself into the acoustic signal that you hear. By taking into account both the electronics and your room, NHT is able to deliver to you a systems design approach that transcends what ordinary loudspeaker designs, engineered simply as loudspeaker products, can deliver.
      So the NHT Evolution is much more than a loudspeaker. It is a systems design approach, designed to work with special electronics and with your listening room, to deliver distinctive features and advantages, as a key part of your total playback system (which of course includes your room). For example, the NHT electronics, designed as a functional part of the complete Evolution loudspeaker system, provide for sonically superior integration of satellite loudspeakers with subwoofers - a feature that is sonically important, and that you won't find in most other loudspeakers, even very expensive high end ones. And, as a further example, the NHT electronics also provide superior features for tailoring the loudspeaker sound very flexibly to work best in your particular listening room and room acoustics. For that matter, even the design of the satellite monitor loudspeaker itself provides for surprising flexibility in tailoring the sound to suit your room and your personal listening preferences.
      Such complex flexibility of control features in this NHT system has a potential down side, in that it could be a complex, difficult, time consuming process for you to optimize its sound. But we have spent literally hours and hours researching and experimenting with these complex control features, and we have arrived at specific setup recommendations that will allow you to quickly optimize this system's sound and hear it at its best. Indeed, in our research we found that we constructively disagree with some of the manufacturer's own recommendations on system setup, and we believe that the system setup we arrived at provides much better sonics. So if you follow our simple recommendations you will hear sound from this system that is (at least in our judgment) superior even to what the manufacturer has heard himself from his own system design.
      The NHT Evolution is also a highly modular loudspeaker system, which gives you the freedom to choose among many combinations of modules in putting together a total loudspeaker system package that will suit your room, your listening needs, and your budget. It's nice to have so many choices among modules, but such an assortment of modules to select from, your choice can be dauntingly complex. However, we have sorted through the key choices among many possible combinations, and we have arrived at simple recommendations of the best sounding modular combinations for you.
      The unique, sonically important systems design features that you get from NHT would be the envy of the most expensive high end loudspeakers. And the NHT Evolution also includes many detail touches you'd expect in high end loudspeakers, such as floor spikes, and secure clamps for mounting a satellite monitor atop a subwoofer. Yet the NHT Evolution modules sell for amazing bargain prices, putting this sophisticated product within easy reach of most budgets. For example, the Evolution satellite monitor is a full 3 way system (not just a 2 way, like many competing products), and boasts two woofers (not just one, like many competing products). The larger M6 monitor weighs in at a hefty 36 pounds, far more than most other home theater satellites, which testifies to the seriousness of this product. Yet this M6 monitor sells for just $600 each, and the M5, a junior version of the same monitor design, sells for just $450 each. We've seen loudspeakers selling for five times this price that do not offer you any more in the way of overall performance, and which can't match the sophistication and sonic flexibility of the Evolution's unique systems engineering design.
      To complement the M6 or M5 satellite monitors, NHT offers a choice of four passive subwoofer models, all using the acoustic suspension principle in a sealed enclosure (no port or vent). There are two models in tower format (which are also intended as supporting stands for the M5 or M6 monitor), and two in floor cube box format. The B6 tower model features two 12 inch woofers, and sells for just $825 each (sold only in symmetrical left/right pairs), while the junior B5 tower model employs just one 12 inch woofer and sells for $425 each (again, sold only in pairs). The W1 box cube model employs the two 12 inch woofers again, and it sells for just $550 each (purchasable singly), while the junior W2 box cube model employs just one 12 inch woofer and sells for $325 each.
      The woofer driver is the same in all these subwoofer systems, and the cabinet volume per driver is the same, so their bass reach is essentially the same (naturally, the subwoofer models with two drivers per box will play low bass twice as powerfully, and/or with roughly half the distortion, as the subwoofer models with just one driver per box). Also, since the woofer driver is the same in every subwoofer model, and since it is utilized as an open front direct radiator, the upper frequency reach of all the subwoofer models is the same (and is commendably flexible, as we'll discuss below). Thus, any of the subwoofers can be utilized with either of the satellite monitors.
      Already you can get a feeling for all the choices you have in combining these Evolution modules. You have a free and flexible choice of subwoofer model, to mate with your choice of satellite monitor. You could even mix satellite monitors in a surround system (say two M6s for the two main front channels, and M5s for the center and all surround positions), and you could also mix subwoofers. For a bargain budget system, you could choose the least expensive modules, say a $450 M5 monitor for each channel, and one or two $325 W2 subwoofers. At the other extreme, you could go for a dream setup with full (and awesome) low bass surround sound, by pairing an M6 monitor with one of the dual driver subwoofers at each position of your surround system (for most other competing loudspeaker systems, this option is too expensive to contemplate, but with the NHT bargain prices you could actually afford this dream setup). Or you could put together an NHT Evolution system with any combination in between these two extremes.
      The Evolution loudspeaker also provides electronic modules, to work with the loudspeaker modules. The X1 at just $350 is a two channel (stereo) electronic crossover, which is essential for sending the correctly equalized signal to any of the Evolution subwoofer modules, and which is also sonically important for sonically integrating the subwoofer with the satellite monitor loudspeakers handling the rest of the spectrum. Thus, you'll want to purchase one X1 for each pair of Evolution subwoofers you buy (and we always recommend that you buy at least two subwoofers, in order to experience the true spatial portrayal of large acoustic spaces at low frequencies).
      The Evolution A1 at $400 is a 200 watt (into 8 ohms) monaural power amplifier, in a convenient pancake (slimline) chassis. It is specifically recommended by NHT for driving the Evolution subwoofer modules, but it is designed as a full range general purpose power amplifier. So you could buy as many A1s as you have loudspeaker modules (one A1 to drive each subwoofer module, and another A1 to drive each satellite monitor module). At the other extreme, you could use your own choice of power amplifier to drive the satellite monitors, and even the subwoofers if you wish, thus not buying any A1s at all.
      As noted, the B6 and B5 tower subwoofers are intended to act as stands for the satellite monitors, for those positions where you choose to locate both a satellite and a subwoofer. Then, for those positions where you choose to locate only a satellite, NHT also sells the P6 and P5 dummy pedestals, which match the B6 and B5 in height and appearance. These dummy pedestal modules enable you to conveniently put all your satellites at the same height, with an aesthetically pleasing visual consistency at all loudspeaker locations. These pedestals also provide a small sonic benefit, increasing (and making consistent at all loudspeaker positions) the output of the satellite monitor in the warmth region, by providing some (and the same consistent) front panel radiation loading for the woofers in the satellites mounted atop these pedestals.
      The tower subwoofers (B6 and B5) and the pedestals (P6 and P5) also include complete mounting hardware, which securely clamp the satellite monitor to the base, to form a tower system with good rigidity and mechanical integrity.
      That completes the roster of modules constituting the Evolution system. It might seem complicated at first glance, but the flexibility and interchangeability of the various modules means that you can easily choose the system that best meets your requirements and your budget. As you'll see, we'll also have some specific recommendations as to which modules perform the best, and which work the best together, so that should make your choices easier.
      This review will be extensive and complex, because the Evolution system includes so many types of modules, and also because the Evolution includes so many flexible options and controls, all of which should be evaluated and explained in a review that hopes to be responsibly thorough. We'll tackle one topic at a time, and in the end you'll have a complete understanding of this product, so you'll know how it sounds, and why it sounds that way, and how to get the best sound from it.
      What about the Evolution's sonic performance? Before we discuss the modules individually, we should give you a brief overview as a reference point. The NHT Evolution system is capable of providing sonic performance equivalent to other loudspeaker systems selling for many times its price. It covers essentially the full frequency spectrum very well, from 27 Hz to 20 kHz. It can play with impressive loudness, even at low bass frequencies (this naturally being a function of how many subwoofer drivers you employ). And, if you set up the system following our (admittedly unorthodox) recommendations, it can deliver very smooth sound throughout the spectrum, and can achieve excellent spatial imaging.
      All loudspeakers have an overall sonic personality, but the Evolution has several. Thanks to the flexibility of its systems design and control features, you can choose from a variety of sonic personalities, to suit your room and listening taste. We'll be recommending one particular sonic personality, which provides smooth, relaxing sound, but we'll also describe your other choices as we go along, so you can make an intelligent choice for yourself.

M6 Satellite Monitor

Rich Warmth

      Many satellite loudspeakers are not tonally rich enough in the warmth region, so they sound small (and lean and thin). When you combine these other satellites with a subwoofer, your natural tendency is to crank up the subwoofer volume, in order to try to give music and sounds decent weight and body. But this doesn't really work, because subwoofers cover only the bass (below 100 Hz), not the warmth region (100-300 Hz). Also, if you try to run most other subwoofers above 100 Hz, they start sounding artificially colored, because they usually have a nasty ringing peak (from the vent or from the front loading slot) around 300 Hz, which you don't want to trigger by feeding in any signal energy at all in this 300 Hz area, so you have to keep the low pass crossover frequency for the subwoofer set below 100 Hz (since a crossover set at 100 Hz still feeds out some energy at 300 Hz). Furthermore, when you crank up the subwoofer volume too much, in order to try to put in some of the warmth missing from the satellite, you wind up with bass that is too heavy (and typically boomy). This produces a total system sound which has too much bass, and then transitions to a satellite that sounds too lean and hence too bright, without enough natural warmth to bridge the spectral gap and give music a natural sounding weight and body. The end result is the artificially unnatural (and fatiguing) boom and sizzle sound that is the bane of most satellite plus subwoofer systems.
       The NHT M6 solves this problem. It has abundantly rich warmth, and so it sounds much bigger than its small bookshelf size. Rich warmth is sonically crucial to achieving natural sound for many musical instruments, voices, and various other sounds. Rich warmth is what makes a grand piano sound grand, instead of like a tiny upright; it's what gives a human voice the palpable presence and body of a chest cavity, instead of comprising just thin throat noises; it's what allows a classical guitar with a large cavity and sounding board to sound like a master's instrument instead of a tiny toy ukulele; it's what gives an alto sax its woofy fullness, a trombone its dark growl; and of course it's what makes a cello and bass sound realistically large. If you ever doubt the musical importance of the warmth region, just remember that middle C (256 Hz) is still within the warmth region, and that the whole bottom half of the musical scale resides within the warmth region or below in frequency. The M6's rich warmth provides all the natural body and weight you could want for realistic reproduction of these sounds.
      And the M6 provides this rich warmth even without needing to rely on any subwoofer. So, with the M6, you don't need to artificially extend the subwoofer's range or artificially boost the subwoofer's volume in order to achieve natural sounding overall system warmth, as you do with many other satellites. Thus, the subwoofer can act in its intended role as provider of just the bass foundation, and it does not have to be cranked up too loud in order to compensate for missing warmth from the satellite. The M6 also provides a natural, realistic sounding spectral bridge to a subwoofer, through the warmth region, which aids seamless sonic integration with any subwoofer.

Strong Upper Bass

      The NHT M6 boasts another sonically important feature at its lower spectral end, a feature that is even rarer among satellite loudspeakers. The M6 can actually put out full spectral response in the upper bass, from about 50 Hz upward. And, because it has two 6.5 inch woofers instead of the usual single woofer you find in satellites, it can put out full energy and play loudly in this octave of upper bass. Thus, you can rely on the M6 to supply the octave of upper bass from 50 Hz to 100 Hz.
      It turns out that this feature is very important for achieving true surround spatial imaging. Our research experiments, described in previous reviews, proved that you need to hear this octave of upper bass in true surround sound, from all the loudspeaker positions around you, in order to experience that crucial, magical sense of being aurally transported to, and totally immersed in, the alternative venue of a good recording (music or film soundtrack). If the loudspeakers all around you are restricted to reproducing the spectrum from only 80 Hz upward, as is almost universally the case for satellites (per the THX spec, and also per the cutoff frequency of the signal from most processors when the loudspeaker positions are set to Small), then the large space all around you abruptly collapses, since your ear/brain needs to hear that octave of upper bass coming at you from all surround directions, in true multichannel sound, in order to be aurally persuaded that a large acoustic space is truly all around you.
      This means that, with most other satellite loudspeakers, you need to also employ a subwoofer at each and every surround loudspeaker position, in order to reproduce that important octave of upper bass. But, thanks to the NHT M6's ability to reproduce this important upper bass octave in full, you can get great surround sound with the M6, and experience the magic of being aurally transported to large spaces, without having to invest in subwoofers all around you at every loudspeaker position. Obviously, this is yet another way in which the NHT Evolution can save you a lot of money, while still giving you the true magic of surround sound. With the M6, you can set the high pass crossover frequency to around 50 Hz, instead of the usual 80 Hz, to feed to all the surrounding satellites, and you'll still hear the magic, even without a subwoofer at each position.

Sealed Enclosure

      Most other satellites employ only one woofer driver, and also employ a vented (ported) bass enclosure, to extend the response and boost the output of that single small woofer. But the M6 takes a different approach, employing two woofers to achieve greater output capability at its lower frequencies, and eschewing the use of a vent to boost or extend low frequency output. The M6 design approach, using a ventless, sealed enclosure, provides several sonic benefits.
      First, the quality of the M6's lower frequency reproduction is very good. Basically, this is because a sealed enclosure affords better transient response for lower frequencies than a vented enclosure does. A vented enclosure has worse overshoot, overhang, and ringing in its transient response, and this sonically produces an inferior quality bass, which typically sounds too heavy and lingering, with poor definition, and a one-note boom. That one-note boom obscures the true pitch variations of musical notes in the bass and warmth regions (i.e. for the whole lower half of the scale), and the temporal lingering of this overhanging boom also acts to obscure all musical information that follows immediately in the shadow of each and every musical note in the bass and warmth regions.
      The one-note boom of a typical vented enclosure has a pitch approximately corresponding to the corner frequency of the vented system's low frequency response, but that boom

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