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.
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
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