Definitive Technology Dymension DM70 Tower & DM20 Center Speakers Review

Our last review encounter with Definitive Technology in the form of the Demand series left a positive impression, but it was a departure from their normal design practices. It almost looked as if Definitive Technology was turning a new leaf in terms of sound character, even though we and many others enjoyed their traditional sound of their bipolar speakers. In the Demand series, Definitive Technology aced the design of a more traditional speaker than their usual bipole loudspeakers. However, if it did signal a new direction for Definitive Technology, they have just launched a speaker series that proclaims they have NOT abandoned their bipole design. The new Dymension speakers, which we previewed back in March, take Definitive Technology’s traditional design and advance it with a host of new features. In today’s review, we take an in-depth look at the Dymension D70 towers and the DM20 center speakers. We will ask the questions of what Definitive Technology has done to move their standard design forward, and how they compete among other speakers in the same product class.

Appearance

At a glance, there has hardly been any aesthetic change at all between the Dymension series and Definitive Technology’s popular BP series. The DM70 are tall, nearly featureless tower speakers comprised of hard angles. The speakers are wrapped in a black fabric, but this is not some kind of grille that can be removed. The fabric shrouds any kind of mechanical elements that would otherwise be visible, so this is not a speaker where the drivers are visible. There are just a few touches that save them from absolute minimalism, such as a slim metallic belt with a buckle that bears the Definitive Technology insignia. The top of the speaker is a metal panel, and on this panel, there is a plate engraved with Definitive Technology badging. The feet are visible, but they are just disc feet mounted on some simple outriggers.

The DM20s is similarly styled; it is a thin, stretched-out oblong that is shrouded in black fabric. The only features it has is a small badge in the lower right corner and some metallic plates that cap the sides (these are actually painted MDF).  The badge is attached by a magnet and so it can be removed or oriented by 90 degrees for those who want to use the DM20s in a vertical, on-wall use. There isn’t much more that can be said to describe these speakers’ appearance. The simplicity of their styling makes them an easy fit in a wide variety of decor. I think they look nice, and they are a good lesson in how to make something look upscale through simple, without spending a lot of money on a real wood veneer with ten layers of lacquer.

Design Analysis

Let’s start our discussion of the Dymension speakers with the DM70 towers since they are much more complex designs. A big selling point of the DM70 speakers is their ‘bipole’ design, which is their ability to radiate sound out of the front and back. Definitive Technology claims that the bipole design creates a ‘spacious, immersive soundstage’ for an ‘incredible depth-of-field and truly enveloping listening experience.’ Is there anything to this beyond marketing hyperbole? Maybe. The DM70s are supposedly able to accomplish this thanks to a rear array of drivers that is identical to the front array and can project the same sound out of the rear of the speaker as the front. What that does is increase the ratio of reflected sound relative to the direct sound for the listener. That should make for a more diffuse sound field which may sound ‘wider’ and more ‘enveloping.’ The research in this area does suggest that a higher ratio of acoustic reflections would make the sound sources seem wider (the technical term is ‘Apparent Source Width,’ or ASW, which is defined as “the audible impression of a spatially extended sound source.”) Research also suggests that increasing reflections also increases ‘Listener Envelopment’ or LEV which is defined as “the listener's sensation of the space being filled with sound images other than the apparent sound source.” Much of the science in this area focused either on concert halls, acoustical properties of the room itself, or multi-channel listening rather than dispersion patterns of stereo speaker pairs. However, Definitive Technology’s marketing claims don’t seem to contradict existing science and may have some merit.

Broadly speaking, the Dymension DM70s are 3-way speakers that use MTM arrays on the front and rear and a powered bass section that uses two passive radiators. But that is an extreme simplification, and there is a lot going on within each component that deserves discussion. Let’s start our discussion of the hardware of these speakers at the top of the frequency band with the tweeters. The tweeters use a 1” anodized aluminum oxide dome set in a shallow waveguide with a phase lens mounted in front of the dome. That isn’t an unusual design, and it has been used successfully before such as in the Demand series that we spent time with. Waveguides and phase lenses can vary greatly in effectiveness, so the devil is in the details in this regard, and we can only see how well-executed they really are in the end result.

There are two 5.25” midranges on each side which use Definitive Technology’s BDSS woofer which stands for ‘Balanced Double Surround System,’ and it gets that name because the cone uses two surrounds: one surround on the outer edge of the cone and one on the inner edge that attaches it to a large phase plug. Definitive Technology claims that this double surround system allows greater linear excursion. The large phase plug is something particular to Definitive Technology loudspeakers, and they call it the ‘Linear Response Waveguide.’  Its job is to block wavefronts from the different areas of the cone from colliding and interfering with each other. It looks to me like it would be effective in that role. 

The Dymension DM70 uses one active 10” subwoofer driver and two 10” passive radiators. The passive radiators are mounted across from each other which is a good idea. Passive radiators can have a lot of moving mass, so having them oppose each other will cancel out the momentum that they impart on the enclosure. They are also coupled together by a foam ring to help mitigate cabinet vibration. The active driver is powered by an onboard 180-watt, Class-D amplifier. The level of the subwoofer section can be adjusted by +12dB to -15dB. DefTech touts a feature of the subwoofer’s volume adjustment system that they call ‘Intelligent Bass Control’ which raises the level of the subwoofer in a nonlinear way so that higher or lower levels will not affect the sound of lower mids (Boston Acoustics implemented a similar feature in their VR960 and VR 970 speakers in 1998). The bandwidth of drivers in loudspeakers is not filtered out over a sharp drop-off but rather a gradual roll-off. If you simply raised the level of a driver within a speaker, the sound that is affected starts getting into other drivers’ bandwidths. So in a normal speaker, if you simply raised the level of the bass driver, its sound would start to be heard in the mids which would degrade the quality. Definitive Technology has solved that problem by changing the shape of the filter at each notch in the subwoofer’s volume knob so that the sound from the subwoofer section does not bleed into the midrange section.

The cabinet seems sturdy enough with most of the bracing in the upper section MTM arrays. The opposite-facing driver arrays should go a long way toward canceling out movement caused by the moving mass of the woofers and voice coils, but cabinet resonances still need to be addressed by damping and mass. The DM70 is held up by a set of outriggers where the user can choose either flat or spike feet. While the fabric sock that covers the enclosure does lend it a unique and handsome appearance, it could be a real problem for cat owners or rambunctious children. The fabric is certainly vulnerable to abuse, and I don’t think that it would be re-upholstered under warranty if a cat decided to use it as a scratching post. One advantage is that the low reflectivity of the fabric will do a lot to make the speakers disappear in low-light conditions.

One disadvantage of the DM70s for home theaters with projection screens is there is a rear blue LED which is somewhat bright, and if these speakers are placed in front of a projection screen, the light from the LED will degrade the screen’s contrast. Users with projection screens could cover the LED with a couple of pieces of electrical tape to block the light from hitting the screen, but a switch to turn off the light would have been welcome here. Alternatively, if appearance of the speaker isn’t a big concern, users could simply rotate the speaker by 180-degrees since the rear array is the same as the front. This speaker would sound the same if it was turned around in place, since the rear-to-front design is symmetrical - so long as the tweeter level switch is set to ‘0dB.’

Connectivity is done through some typical 5-way binding posts. There is no LFE input for the subwoofer section, and that is probably a good idea to avoid confusion. These speakers ought to be set as ‘large’ in AV processors since they should have no problem with lower bass. There are also some binding posts for the optional DM90 ‘height’ speaker for Atmos systems that can be installed on top of the DM70s. Height speakers on top of the main speakers are not normally the best solution for Atmos upfiring height channels, so I would recommend users check to see if ceiling speakers can be used for Atmos height channels before resorting to setting speakers on top of the left/right mains. Definitive Technology also offers the wall-mountable Dymension DM95 speakers as an option against ceiling speakers. Without the Atmos speaker, there is a solid aluminum plate topping off the DM70. 

The DM70 speaker design seems like it could accomplish its goal of issuing more acoustic reflections than a traditional speaker, and outside of that aspect, the build quality and engineering seem sensible as well. For those who might prefer the bipole aspect toned down, there is a switch on the back panel that takes the rear array down by 6dB. This could be especially helpful if the user needs to position the speaker close to the wall.

Moving on to the DM20 center speaker, it is a 2.5-way slim center/on-wall LCR that is designed to fit in tight situations. It is a lot less complex than the DM70 tower speakers and does not have a rear driver array. It uses the same aluminum oxide dome tweeter as the DM70 but not the same midrange woofers. The woofers are four composite polymer 4” cones. While the use of 4” drivers might not sound like it would have serious dynamic range, four of them equals the surface area of an 8” woofer, so the DM20 may be capable of some real punch, at least in midrange frequencies. The -3dB low-end of its spec’d frequency response is 91Hz, so it isn’t designed to play low bass. Users should set this speaker to ‘small’ in their AV processor or receiver, and they might consider a 90Hz crossover frequency. The DM20 is a sealed design that uses a low-volume enclosure, so lower bass would not have been possible, at least without sacrificing a lot of dynamic range. Definitive Technology made the right choice in exchanging low-frequency extension for dynamic range since anyone who has this center will also have a subwoofer.

The DM20 has rear keyhole slots so that it can be mounted against the wall either horizontally or vertically. This enables it to be used as an on-wall speaker as much as a stand-mount center speaker. It is a bit hefty at 22 lbs., so make sure it is mounted onto studs or anchors. One problem is that the keyhole slots are spaced 20” apart, and this is awkward because the slots won’t quite line up with the 16” stud spacing of North American homes or 24” spacing of European homes. For this reason, I recommend that the non-stud mounting screw use an anchor, or both use anchors if the keyhole slots can’t line up with any studs.

The DM20 drivers are arranged with the tweeter sandwiched between two sets of two midrange woofers in an MTM-style design (although technically this implementation is an ‘MMTMM’ but the principle is the same). This will inevitably give rise to interference nulls at off-axis angles that horizontally-aligned MTMs are known for. We have talked about this at length multiple times in articles such as: Vertical Vs. Horizontal Center Speaker Designs, Vertical Vs. Horizontal Center Speaker Designs - An Alternate Perspective, and Center Channel Speaker Design Additional Considerations. To boil down a complex engineering issue, MTM designs can have very good responses at the on-axis angle but can have very poor responses at off-axis angles along the plane of the drivers. For horizontal MTM center channels, that means if you are seated off to the side relative to the center speaker, you can be met with a subpar sound because of a depression in an important frequency band, typically the midrange to upper midrange. All MTMs will have this problem to some extent, but some will have it more severely than others. The DM20 ameliorates this somewhat by going with a 2.5-way design where the outer mids have a much lower low-pass frequency than the inner mids.  

I decided to test for this off-axis interference cancellation by listening for any timbral shift in the off-axis versus on-axis sound in the DM20s by playing a white noise as well as dialogue and music samples. It was quite evident in this speaker. Listening at an off-axis angle causes a significantly audible spectral shift in this speaker as opposed to having it face the listener. There was a definite ‘hollowing out’ of sounds that had midrange energy. I could still understand dialogue at off-axis angles, but the timbre had shifted at those angles, and not for the better. At an on-axis angle, everything sounded full and fairly good. For this reason, I wouldn’t advise the addition of the DM20 to a set of DM70s for the purpose of getting center imaging for far off-axis listeners (>15 deg). To be sure, the DM20 can anchor center channel sound to the right location, but the qualitative hit that it suffers at off-axis angles may negate its advantages. And to reiterate what I said before, any low-profile center speaker would inevitably have the same problem. The DM20s are not at all unique in this regard.

It should be kept in mind that this off-axis interference cancellation only happens when the DM20 is used horizontally, and users who choose to use it as vertically mounted on-wall pairs will not have this problem. However, it does mean that the vertical dispersion will be a bit narrow with vertical mounting, so users should try to mount the DM20s with the tweeters roughly around the ear level of the listening position.

Listening Sessions

In my 24’ by 13’ (approximately) listening room, I set up the speakers with a few feet of stand-off distances between the back wall and sidewall and equal distance between the speakers and the listening position. I angled the speakers to face the listening position. The listening distance from the speakers was about 9 feet. No room correction equalization was used. Processing was done by a Marantz 7705 and the amplification was done by a Monoprice Monolith 5x200 amplifier. No subwoofers were used. All music listening was done with the DM70s alone in two-channel stereo, and I brought in the DM20 for movie watching.

I should say that before I sat down to do some serious listening with this speaker, it took a little while and some extra positional tweaking to get a balanced sound between the left and right DM70 speakers. For most speakers, I can place them in the same spot for an even soundstage between the left and right speakers, but the DM70s did take more work to get a balanced sound. It’s possible that their unusual acoustical properties were reacting to my room differently than traditional speakers, but setting these up was a bit more involved than normal. Also, I found that the soundstage didn’t stabilize until I was at least as far back as my typical 9-foot listening distance. At closer proximities, it was difficult to get a good stereo-center image.

Music Listening

A major new release this year came from Depeche Mode in their 15th studio album, “Memento Mori.” Like so many others, I have been a fan of the band for decades, and this release is particularly poignant because it is the first without founding member Andy Fletcher who passed away in May of 2022 early in the album’s formation. Remaining members David Gahan and Martin Gore, who famously never had an easy relationship, decided to finish the album. Since its release, it has been widely acclaimed by music critics as the best work that Depeche Mode has released in years. I thought it would be a good opportunity to see what the DM70s could do for the harder edge of pop music.

The first track, “The Cosmos is Mine,” opened with a pretty hefty bass line, and the DM70s handled it with subwoofer-like authority. Gahan’s voice was processed to make it sound nearly phantasmagorical, and it hovered over the speakers like an otherworldly spirit. Ambient synth sounds darted left and right, and the speakers could image these sounds outside of the boundaries of the width of their placement. Subsequent tracks, such as the album’s single, “Ghosts Again,” had a drier mix on the vocals, and this gave them a stronger center image. I was afraid that the rear acoustic emanation might blow center imaging out to huge proportions, but this wasn’t the case. While the center image was not pinpoint precise as I have heard with some other speakers, the DM70s could place the singer and instruments where they are supposed to be around the soundstage. The soundstage was generally quite wide and expansive, more so than conventional loudspeakers. On occasion, I did hear an uncanny sense of depth, such as on the track “Soul With Me” where the processing on the singer’s voice combined with the speaker’s unique design pulled the voice back well behind the speaker’s distance from me. By the end of the album, I would say that the DM70s killed it (and I mean that in a good way). This music sounded great on these speakers, and I am sure most Depeche Mode fans would agree. The wide soundstage gave “Memento Mori” a ‘big,’ panoramic sound that particularly suits that album.   

To see how the DM70s sound with orchestral music, I selected an album from Qobuz titled “Destination Rachmaninoff. Departure.” This album contains Rachmaninoff’s Piano Concertos No.2 and 4 as well as Rachmaninoff’s piano arrangement of Bach’s “Partita for Violin Solo No.3.” I decided on this music because it would have a piano at the forefront with orchestral accompaniment, so I could hear what the speakers do to image a single instrument as well as a full orchestra. Piano is played by the virtuoso Daniil Trifonov who is accompanied by the Philadelphia Orchestra, and the performance was recorded at the palatial Verizon Hall in Philadelphia’s Kimmel Center. I streamed this beautifully-produced Deutsche Grammophon release in a 24-bit/96kHz resolution.

While the piano was the lead instrument here, it did not overshadow the orchestra as can sometimes happen. One reason for that, which can be heard through the DM70 speakers, is that the recording engineers did not close-mic the piano like is very often done. This, thankfully, makes the piano a part of the orchestra rather than some giant that sits atop the orchestra. The piano did image between the speakers, but not with laser precision - not that such precision should be expected in a recording done in a symphonic hall. However, the reverb of the performance space wasn’t very extensive, and I don’t know if that is because the Verizon Hall is not as reverberant as other symphonic halls or that was just how the recording engineers set up the microphones. Whatever the reason, this recording style seemed to compliment the DM70s, and the sound they produced from this album sounded natural and lifelike. It sounded like a closer seat to the performers, and that may be partly due to the wide soundstage projected by the DM70s. Tonally, I never noticed anything that sounded off or colored, and the instruments sounded correct. During this album, I tried to hear the difference that the DM70’s rear array attenuation switch made. It reduces output from the rear tweeter by 6dB, but the difference that it made for this music was subtle at best. Regardless, in either mode, the music sounded terrific. It’s possible that the extra reflections from the rear array enhance the concert hall effect which can be especially beneficial to this type of orchestral music, so I do think that classical music lovers with a penchant for full orchestras ought to give the DM70s very close consideration. I can’t imagine anyone complaining about the sound quality of what I heard when listening to this album on these speakers.  

For something simple and traditional that focuses on a few acoustic instruments, I found a recent release titled “Uusi Aika” by the Finnish jazz ensemble Uusi Aika (it must have taken them a while to come up with the album name). I wanted to hear how the DM70s would image a smaller-scale performance with its larger imaging. The album is formed mostly from just saxophone, piano, bass, and percussion with a smattering of a few other instruments here and there. This is lower-tempo jazz for those in the mood for a very relaxed pace. The recording doesn’t have a usual studio sound but instead sounds like a live performance done with a single microphone.

The recording gave this performance an intimate sound as if I were right next to the performers, and the imaging of the DM70s added to that effect. The lead saxophone on the first track imaged big as did the double bass. A similar effect was heard on the shakuhachi on the second track. I think a more traditional speaker might have squeezed the soundstage of this album a bit more as well as tightened up the imaging of the instruments, but I don’t think the DM70s imaged poorly, but rather just not as precisely as more conventionally designed speakers, especially ones with narrow directivity control. As with other acoustic music albums that I listened to, tonality was generally very good. The detail and timbre of the overtones of the double bass were terrific to hear and evidence that the bass section was well-integrated with the MTM arrays. Likewise, the texture of the saxophone was articulate and nicely rendered. The bass was strong without being overbearing, but that is partly a setup matter since the user has control over the subwoofer level on the DM70. For my tastes and in my room, the dial at just a couple of notches under 12 o'clock sounded right. In that setting, nothing sounded off, even by a little bit. I enjoyed “Uusi Aika” by Uusi Aika, and I liked the sound that the DM70s imparted to this music. Some might prefer the smaller soundstage and more focused imaging of traditional speaker designs, but I am sure there are many who would quite enjoy the presentation given by the DM70s.

For something that can push the loudspeaker hard, I threw on Malux’s “Destroy the Machines.” This is a drum’n’bass album that begs to be played at a loud volume. It is chocked full of ferocious breakbeats, scorching lead synths, and hard bass with everything mixed at high levels. It is dance music, but Malux mixes things up enough so that it is not too repetitive to be enjoyed while seated in an Eames Chair and enjoying a glass of 30-year-old Macallan in your finest smoking jacket. On paper, the DM70s should be able to rock hard, but we have to test it to know for sure, so I cranked the volume to see what it could do.

I knew right away that the DM70s had more dynamic range than my ears did, at least for the mids and treble. I backed down on the volume in the interest of preserving my hearing, but there was no doubt that the speakers could rock. While I backed down to a loud but not insane volume for the system as a whole, I still wanted to see what the limits of subwoofer sections would be, so I decided to max out the subwoofer sections, since loud deep bass is a lot easier on the ears than loud treble and mids. Taking the system volume up with the sub volume at max, I could drive the MTM arrays to louder levels than the DM70’s subwoofer could follow, but that was at a very loud level. At very high levels, the bass tonality did change indicating that the subwoofers were running into some distortion, so the limiters aren’t so strict as to only permit clean bass. I wasn’t able to drive the system into bottoming out, but it could be audibly pushed past linear behavior above a certain point. However, normal users are unlikely to drive these speakers that hard. Those who want very loud bass should probably supplement these speakers with subwoofers. Perhaps the Definitive Technology DN15 15" sub with dual passive 15"s would do the trick.

Movie Watching

To see what the DM70s could do for a typical movie experience, I selected the 2013 crime comedy “American Hustle.” This film takes place in New Jersey in the late 70s and concerns a con man who is caught in one of his own schemes and is forced to work with the FBI along with his accomplice/mistress to help an investigation into political corruption. I hadn’t yet seen “American Hustle,” but this big-budget movie with an all-star cast is sure to have a top-notch sound mix and should be a good demonstration of the DM70’s sound with a major Hollywood movie.

“American Hustle” turned out to be a fun caper with talented actors turning in great performances with strong, well-written roles. The dialogue was ripe with 70s New York and New Jersey vernacular and profanity, and it sounded terrific on the DM20 center. Dialogue intelligibility was never a problem even when muttered, whispered, or improvised. The sound mix was rich in music, not just from the period with pieces from Donna Summer, The Bee Gees, and The Wings, but also from prior eras that reflect the film’s characters. Duke Ellington’s “Jeep’s Blues” played a major role, as did Tom Jones’ “Delilah,” and they sounded terrific on the DM70s. The sound mix was also rich in the sounds from the era. The rumble of the V8s from massive old Cadillacs, Buicks, Oldsmobiles, and Lincolns was impeccably rendered, and it is a once-common sound that is seldom heard in real life these days. There weren’t that many more sound elements from a dialogue and music-driven film, but the artistry of this sound mix certainly deserves an audio system worthy of it, and I would say that Definitive Technology’s Dymension series is certainly that.

For a more fantastical sound mix, I watched the 2022 Marvel movie “Dr. Strange in the Multiverse of Madness.” The first Dr. Strange film is one of the few Marvel adventures that I actually enjoyed, so I was looking forward to seeing this sequel, and the DM70s presented a sound system that seemed worthy of the endeavor. With the legendary Sam Raimi in the director’s seat, this outing promised to be a wild experience in both sight and sound, so I turned the levels up and strapped in.

The movie, and thus the sound mix, was indeed a riotous excursion, and the DM70s did a terrific job in executing the sound reproduction. There were many instances of creatively bizarre sound mix choices such as when the doctor and his traveling companion were falling through the many bizarre universe incarnations or when the Scarlet Witch attacked the Sanctum Sanctorum in alternate New York City. Raimi never lets the camera sit still for long, and the whirling, manic perspective was echoed by the sound mix. While this movie was prime material for a surround sound mix, the DM70s could image the restless point-of-view nicely, and I didn’t miss the surrounds at all. The bass was also good, although I do think there was some very deep bass that the subs did miss. They thundered and rumbled my room, but not quite with the same authority that a large, ported 15” sub might have. However, I think most people would be very happy with the bass ability of these speakers and feel no need for an extra subwoofer at all. The dialogue intelligibility of the DM20 was fine. I had anticipated the DM20s being badly outgunned by the DM70s, but that didn’t prove to be the case. Even though it is a much smaller speaker, I never noticed any weakness in the center of the soundstage. Director Raimi’s longtime collaborator Danny Elfman does the music score, and the DM70s really shined with this energetic orchestral music. Indeed, the film as a whole had a quite complex and multi-layered sound mix, with the lively music running alongside a plethora of effects noises as well as dialogue, but it never became a confused or jumbled mess on these speakers. In the end, I quite enjoyed “Dr. Strange in the Multiverse of Madness” with the DM70s and DM20, and if they make a sequel, I hope I will have a sound system as good as these speakers to watch it.  

Definitive Technology Dymension DM70 & DM20 Speaker Measurements & Conclusion

The Definitive Technology Dymension DM70 speakers were measured in free-air at a height of 4 feet at a 2-meter distance from the microphone, with the microphone raised to an 8’ elevation that was level with and aimed at the tweeter center. The measurements were gated at 8 milliseconds. In this time window, some resolution is lost below 400 Hz and accuracy is completely lost below 200 Hz. Measurements have been smoothed at a 1/12 octave resolution.

The above graphs depict the DM70’s direct-axis and horizontal dispersion out to a 90-degree angle in five-degree increments. Information on how to interpret these graphs can be read in this article: Understanding Loudspeaker Review Measurements Part II. There is a lot of good news to be seen here. Firstly, the midranges and treble are very nicely neutral. There are some slight elevations centered around 500Hz and 20kHz, but other than that we have a very flat on-axis curve, very much within the +/-3dB window that Definitive Technology specifies from 30Hz to 23kHz. The off-axis curves are similarly good with excellent correlation out to 30 degrees. Past the 30-degree angle, the off-axis responses do get a little rocky, but they still aren’t bad relative to many other loudspeakers in this class.

The above graph shows individual frequency responses on the horizontal axis from the on-axis response out to 30 degrees. The most neutral responses seem to be between 15 to 20 degrees, but the sound won’t change a lot between any of these angles. I would give these speakers a mild toe-in to be slightly facing the listening position but not facing it directly for the most neutral direct sound. 

The above polar map shows the same information in the preceding graphs but depicts it in a way that can offer new insight regarding these speakers’ behavior. Instead of using individual raised lines to illustrate amplitude, polar maps use color to portray amplitude, and this allows the use of a purely angle/frequency axis perspective. The advantage of these graphs is they can let us see broader trends of the speaker’s dispersion behavior more easily. More information about interpreting this graph can be read in this article: Understanding Loudspeaker Review Measurements Part II.

The DM70 is a fairly wide dispersion speaker with a rather complex dispersion pattern. We see some webbing effects out at far off-axis angles, and I believe this is due to a mild interference pattern created by the rear array interacting with the front array. It does start to seep into a 30-degree listening window at mid-bass frequencies where the far-off axis response has a lot more output below 400Hz with respect to the on-axis response. Since that region is mostly below the transition frequency of most domestic rooms where standing waves will dominate the sound, what is shown in a graph of anechoic measurements will not at all resemble the in-room response. While there is some off-axis energy beyond 30 degrees, the response does get a bit ragged, so these speakers are best listened within a 30-degree angle of the on-axis angle. That will cover any reasonable listening area, so this speaker should sound good from any intended listening location.

It should be noted that this graph also matches a polar map of the rear of the DM70, so if we turned the speaker around by 180 degrees, it would be the same. The rear array is essentially the same as the front. As we mentioned before, this speaker would sound the same if you turned it around in place. 

The above graph is a sampling of some of the vertical angle responses at and around the on-axis angle. Negative degrees indicate angles below the tweeter, positive angles indicate angles above the tweeter, and zero degrees is level with the tweeter. The DM70 would best be experienced with ears level with the tweeter. Not much changes within a +/-5-degree angle of the tweeter, but the woofers of the MTM array do start canceling each other out at a 10-degree angle, particularly at 10 degrees below the tweeter axis. It’s not easy to see the tweeter since there is fabric covering it, but it lays at a height of 38.5” with the speaker’s feet attached. Most listening positions will be within a +/-5 degree angle of the tweeter, since, at 2-meters, a 5-degree downward angle will be at a 31.6” height and at 3 meters it will be 28.2” height. However, those with low-slung seating shouldn’t be positioned close to the speaker.

The above graph shows the DM70’s low-frequency response captured using groundplane measurements (where the speaker and microphone are on the ground at a 2-meter distance in a wide-open area). Here, we look at the speaker when measured with the subwoofer volume knob at maximum, minimum, and the middle position which is 12 0’clock on the volume dial. At 12 o’clock, the speaker has a nicely flat response down to nearly 30Hz before it starts to roll off. Raising or lowering the subwoofer volume knob affects frequencies below 120Hz. Here we can see Definitive Technology’s ‘Intelligent Bass Control’ at work, where the low frequencies can be changed without affecting the mids. This is not difficult to do with a DSP-controlled unit but would be impossible were this speaker fully passive or using simple analog filters. There is a curious dip in the response centered at 55Hz when the volume knob is lowered completely. While this speaker has a very accurate response in low frequencies at 12 o’clock, it doesn’t make a huge difference because room acoustics dominate the sound in this range and will inevitably mangle the low-frequency response below the room’s transition frequency. Nonetheless, it’s nice to see such neutral sound capability coming out of the box.

The above graph shows the electrical behavior of the DM70. There isn’t really anything unusual here except that the impedance curve does not exhibit the usual saddle shape that we always see with ported or passive radiator speakers. The obvious reason is that there is not much for the system to measure in the bass range since the DM70 bass drivers have their own amplifier so the impedance and phase in that region are only seeing the midrange drivers. Switching the rear tweeter’s -6dB attenuator didn’t change much with respect to impedance. Definitive Technology labels this as a 4-ohm speaker, and that is what we see. This is not an egregious electrical load, and any decent amplifier should be able to handle it without issue.

DM20 Center Channel Measurements

The above graphs depict the DM20’s direct-axis and horizontal dispersion out to a 90-degree angle in five-degree increments. Here we see the on-axis response of the DM20 is quite good, but it doesn’t last long as we move out at further angles. The problem is that the interference cancellation between the woofers creates a very significant drop in the sound at off-axis angles. At 10 degrees, the woofers start to battle each other, and we see signs of phase cancellation just under the tweeter’s bandwidth. Moving further out, we end up with a 10dB suck-out that extends up to 2.5kHz. I would advise listeners to not be seated off-axis when listening to this speaker. The irony is that the reason for the center speaker’s existence is to have center imaging for listeners not at a point equally distant between the left and right speakers. In this case, off-axis listeners will get that, but in a badly degraded sound. Horizontal MTM loudspeakers are not great solutions for center channel speakers, and the DM20 is no exception.

The above polar map more lucidly exhibits the problems with this type of design. It can only really sound good at or very near the on-axis angle. Far-field listening will be alleviated the problems endemic to this design to a degree. Outside of the angle close to the direct axis, you will hear lots of treble with depressed midranges. It is possible that this problem won’t be heard to be quite as severe in the room, since the acoustic reflections of the midrange drivers may average out some of this phase conflict. Going back to my discussion of the problems of interference cancellation, here we see a lot of it when the woofers do not have an equal distance from the microphone. As their distance becomes unequal to the measurement mic at off-axis angles, their phase difference becomes greater, and they end up canceling themselves out. As we discussed before, this is not just a harmless measurement artifact, this is an audible attribute of this loudspeaker. The user should have this speaker facing them directly, and off-axis listeners will be met with hollowed-out mids and lower treble, especially if they are seated too close to the speaker.

The above graph shows the DM20 on its vertical axis if the speaker was oriented horizontally like a center speaker. Conversely, this would be the horizontal dispersion if the user is going to mount the DM20 vertically as an on-wall. We get a much wider and more even spread of acoustic energy in this axis. We do see a swelling of dispersion around 4kHz, and this is likely due to the tweeter fully kicking in in this range. Remarkably, the tweeter keeps a fairly broad dispersion all the way past 20kHz, and this is surprising because most dome tweeters tend to narrow their dispersion a great deal by such a high frequency. It’s possible that the phase lens in front of the tweeter is the cause of the wide upper treble dispersion here.

The above graph shows the electrical behavior of the DM20. This is an uneventful graph and shows a well-behaved loudspeaker in the electrical domain. Any competently designed amplifier could handle this electrical load without problem. The most strenuous part is the steep phase angle between 150 to 200Hz, but then it levels out to an easier load.

Conclusion

Before bringing this review to a close, I will briefly go over the strengths and weaknesses of the products under evaluation, and, as usual, we will start with the weaknesses. There likely isn’t any surprise when I say that the weakest part of this speaker set is the sacrifices that the DM20 has to make to achieve a low profile for center channel duties. As mentioned before, most center speakers suffer from the same type of weaknesses, and the center speakers that do not have this problem must be quite a bit taller. Those who are seated off to the side of the center speaker will be listening in a suboptimal sound field, although that problem is mitigated somewhat in far-field listening. Those who want center channel content to have good coverage over a wide listening area should consider just using a phantom center by letting the front left and right speakers take care of the center speaker content or finding a way to vertically orient a DM20 (perhaps behind a AT screen). The DM70 tower speakers can cover a wide angle with a full, balanced sound, but the DM20 center speaker has limitations. All of Definitive Technology’s center speakers for this series will have the same problem, since they all use the same basic design, so this isn’t just limited to the DM20, unfortunately. We are hopeful that Definitive Technology would consider making a larger 3-way model with a W(T/M)W driver topology to better handle wider listening areas.

Another aspect about the DM70 and DM20 speakers that I wouldn’t say is a weakness specifically but rather just a comment about their design and use is that I think there are better choices for dedicated home theater rooms, especially those with projectors. I say this for four reasons. First, I don’t think the DM20 center is on the same level as the DM70 towers for the reason discussed above; it doesn’t have sufficiently wide dispersion for off-axis seating which is what many dedicated theaters have. Second, the more multi-channel that your theater gets, the less acoustically reflective you will want the system to be as a whole, since it becomes the job of the surround speakers to provide sounds of spaciousness and envelopment, and surround speakers are better suited for that than left and right fronts, even ones like the DM70s. That negates the usefulness of the highly reflective bipolar design. Third, any dedicated home theater is going to use separate outboard subwoofers, and that negates the need for towers with a powered bass section. In other words, you would be paying a lot for a feature that you wouldn’t really use. Fourthly, the LED on the rear-mounted amp panel sprays a fair amount of light that would hurt the contrast of any projection screen behind the speaker. Regarding these four points, I should emphasize that they pertain to a dedicated home theater; not a typical family room that isn’t trying to be focused solely on home theater. In fact, I would argue that the DM70s excel at providing a great sound for people without devoting a lot of space to a surround sound system. This is especially true if floor space is limited and additional powered subwoofer cannot be added to the system.

This brings us to their strengths, which are many. First of which is the sound quality when properly set up. The DM70s have a neutral sound both on and off-axis. This took me by surprise since I thought that the unusual acoustic radiation pattern generated by the rear array might lead to some odd voicing, but it does not. Everything sounded tonally balanced, and you could move a considerable distance from the on-axis angle without changing that neutrality. The soundstage had a depth and level of envelopment beyond normal speakers, so I find that they do work as advertised in that regard. They do give up some precision in imaging to accomplish this expansive soundstage, but the imaging wasn’t as imprecise as I was expecting, and I could still get a good sense of center imaging if not as tightly focused as some other loudspeakers. The dynamic range of the DM70 was very good, and it does not take a lot of wattage to drive to loud levels, nor does it take a heavy-duty amp since the electrical load is not onerous. While serious bass heads will want to add outboard subwoofers to augment the low-frequency headroom, most people would be very happy with what the DM70s can do from top to bottom of the frequency range.

In addition to their sound, they look fairly good as well. They aren’t dazzling, but they have an austerity that will enable them to blend in most rooms without being noticed, and that is a quality that a lot of people will appreciate. The build quality seems up to the job, and they are somewhat hefty at 71 lbs. each. I also like the adjustability of the subwoofer level along with the ability to adjust the rear tweeter output. While I didn’t notice a big difference when taking the rear tweeter down by 6dB, I can imagine that it would have more of an effect in a smaller room or placements closer to the back wall. Likewise, the ability to lower the subwoofer volume would be a valuable tool in reducing boominess or overloading in a small room.

I think it would have been interesting if Definitive Technology made the DM70s fully active instead of just active with subwoofers. If they had been given an active crossover, the user could easily adjust the rear array to any level that they wanted instead of just a 6dB attenuation. Furthermore, it could easily have been given a phase knob, so the user could explore the effect of different acoustic radiation patterns on the soundstage (The DM80 has the ability to experiment like this since the rear array has its own inputs). Definitive Technology is already throwing on active electronics onboard, so they might as well take it all the way and get the benefits of active crossover circuits across the entire speaker. 

In my opinion, the DM70s would be a great choice for a two-channel hi-fi system as well as something to enjoy movies in a family room for those who don’t want the complexity of a surround sound system. They do away with the need for a subwoofer, and they don’t have a large footprint. They can project a wide, spacious soundstage so listeners can get an enveloping sound without needing surround speakers as much. They don’t need to be aimed at the listener for a good sound, so they don’t need a particular toe-in. I enjoyed their sound and wish I had them for longer to relisten to some of my favorite old albums. Their $4k MSRP is a lot of money, but I would say that is a very fair price considering everything that they can do. There are a lot of great speakers in that price range, but if I were shopping in that segment, I would be giving them a very close look. I think that the vast majority of buyers of the DM70s will be very happy with their purchase. 

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Imaging
Dynamic Range
Fit and Finish
Performance
Value