Definitive Technology Descend DN15 15" Subwoofer Review

[shadyJ]

​

For a long time, monster subwoofers have been the domain of manufacturer direct businesses, since demand for giant subs was relegated to a relatively niche market of home theater enthusiasts. However, the breakout success of some of these home theater businesses has proven to the audio business that the people willing to accommodate a monster subwoofer in their home constitute a larger fraction of the buying market than previously thought. We have recently seen some of the more mainstream loudspeaker manufacturers try their hand in the big sub game, and two that we looked at were the Paradigm Defiance X15 and Klipsch Reference Premiere RP-1600SW. Definitive Technology wasn’t about to let this challenge go unanswered, so they have thrown their hat in the ring with the Descend DN15, the subject of today’s review. The DN15 is basically a 2’ cube that weighs 115 lbs., and it uses a 15” driver powered by a 500-watt RMS amp to move two 15” passive radiators. In other words, it is a bruiser - at least on paper. How does it compare in practice? Can we get deep bass and audiophile sound? Read our full review to find out!

READ: Definitive Technology Descend DN15 Subwoofer Review

 

[XaVierDK]

Very interesting review, and it's interesting to read your note on testing vs the Monolith SW15.

You mention that there are definite differences between the two subs, but in a typical room how much of those differences do you think would be audible, or is it a "different strokes" situation?

Further, I was wondering if you felt the lack of infrasonic extension hurt it in any way? I have been a bit of a die-hard "infrasonics aren't really something we should chase" for a while, and from your review it would seem you didn't miss it much, even though you have often talked up infrasonic performance.

 

[ryanosaur]

Thank you, @shadyJ !

 

[Danzilla31]

View attachment 66533​

For a long time, monster subwoofers have been the domain of manufacturer direct businesses, since demand for giant subs was relegated to a relatively niche market of home theater enthusiasts. However, the breakout success of some of these home theater businesses has proven to the audio business that the people willing to accommodate a monster subwoofer in their home constitute a larger fraction of the buying market than previously thought. We have recently seen some of the more mainstream loudspeaker manufacturers try their hand in the big sub game, and two that we looked at were the Paradigm Defiance X15 and Klipsch Reference Premiere RP-1600SW. Definitive Technology wasn’t about to let this challenge go unanswered, so they have thrown their hat in the ring with the Descend DN15, the subject of today’s review. The DN15 is basically a 2’ cube that weighs 115 lbs., and it uses a 15” driver powered by a 500-watt RMS amp to move two 15” passive radiators. In other words, it is a bruiser - at least on paper. How does it compare in practice? Can we get deep bass and audiophile sound? Read our full review to find out!
READ: Definitive Technology Descend DN15 Subwoofer Review

That was a great review Shady!!!! Nice to see Definitive actually building a sub that can dig to 20hz! They finally made a true subwoofer

Little pricey and I wish they had XLR but otherwise impressive for it's side and the amplifier power they chose to go with

 

[Danzilla31]

Thank you, @shadyJ !

It doesn't have any ports

 

[shadyJ]

Very interesting review, and it's interesting to read your note on testing vs the Monolith SW15.

You mention that there are definite differences between the two subs, but in a typical room how much of those differences do you think would be audible, or is it a "different strokes" situation?

Further, I was wondering if you felt the lack of infrasonic extension hurt it in any way? I have been a bit of a die-hard "infrasonics aren't really something we should chase" for a while, and from your review it would seem you didn't miss it much, even though you have often talked up infrasonic performance.

It would depend on content and usage to tease out the differences between these subs. If you are rocking hard with stuff that emphasizes mid-bass, the SW-15 will hit harder. However, if you are listening to stuff that uses very deep bass, the DN15 will sound more authoritative and cleaner.

Infrasonics do make a difference, but it isn't a huge one, and it depends on how deep we are talking about here and just what is meant by infrasonics. Most people take infrasonics to mean stuff below 20Hz, and that is a reasonable definition, although simplistic given that infrasonic literally means "below audibility."

Personally, I might divide infrasonics into two ranges: from 25Hz to 16Hz, and then lower than 16Hz. 16-25Hz is an audible bandwidth but a somewhat subtle one. Nonetheless, it definitely adds a layer of realism to the sound when the system can reproduce it. It's nice to have but not hugely important, in other words, the lack of it shouldn't do much to inhibit your enjoyment of whatever content you are listening to.

Below 16Hz, I would say that spectral content in that range can be perceived but it is extremely subtle, much more so than 16Hz and above. It's not very important and is only worth chasing for heavy-duty dedicated reference home theaters. The omission of playback in this range wouldn't do anything to inhibit your enjoyment of whatever you are listening to (unless that content made a real point of laying in hard in that band, a la "Bass, I Love You" by Bass Mekanik). Human hearing can hardly even differentiate pitch in this range.

 

[TLS Guy]

View attachment 66533​

For a long time, monster subwoofers have been the domain of manufacturer direct businesses, since demand for giant subs was relegated to a relatively niche market of home theater enthusiasts. However, the breakout success of some of these home theater businesses has proven to the audio business that the people willing to accommodate a monster subwoofer in their home constitute a larger fraction of the buying market than previously thought. We have recently seen some of the more mainstream loudspeaker manufacturers try their hand in the big sub game, and two that we looked at were the Paradigm Defiance X15 and Klipsch Reference Premiere RP-1600SW. Definitive Technology wasn’t about to let this challenge go unanswered, so they have thrown their hat in the ring with the Descend DN15, the subject of today’s review. The DN15 is basically a 2’ cube that weighs 115 lbs., and it uses a 15” driver powered by a 500-watt RMS amp to move two 15” passive radiators. In other words, it is a bruiser - at least on paper. How does it compare in practice? Can we get deep bass and audiophile sound? Read our full review to find out!
READ: Definitive Technology Descend DN15 Subwoofer Review

Shady, just one comment. I'm not sure there is a high pass filter. One of the major differences between a ported design and a passive radiator design, is bass roll off below F3. A ported design will roll off 24 db per octave and a passive radiator design at 36 db per octave. It seems to me that this sub is rolling off at 36 db per octave.
If there is not a HP filter, then may be there should be, which would give the unit more power above F3.

Not sure an H power supply was a good choice. Those switching voltage rails in the power supply have been a bit of a headache in amps employing that topology.
Actually that would pause me wanting to invest in that sub until some long term reliability was known. I think they would have been better off following the class D bandwagon. They make less heat anyway, which I think is a significant issue given the relatively small air space inside the box.

 

[shadyJ]

Shady, just one comment. I'm not sure there is a high pass filter. One of the major differences between a ported design and a passive radiator design, is bass roll off below F3. A ported design will roll off 24 db per octave and a passive radiator design at 36 db per octave. It seems to me that this sub is rolling off at 36 db per octave.
If there is not a HP filter, then may be there should be, which would give the unit more power above F3.

Not sure an H power supply was a good choice. Those switching voltage rails in the power supply have been a bit of a headache in amps employing that topology.
Actually that would pause me wanting to invest in that sub until some long term reliability was known. I think they would have been better off following the class D bandwagon. They make less heat anyway, which I think is a significant issue given the relatively small air space inside the box.

There is almost certainly a high-pass filter. Most every commercial subwoofers will have a high-pass filter, if only to protect the woofer from over-driving. As for class H, time will tell about their long-term reliability. I don't think enclosure space is going to be an issue for this sub. It might be an air-tight enclosure, but it's certainly a larger space than most sealed subs.

 

[oniiz86]

Not sure an H power supply was a good choice. Those switching voltage rails in the power supply have been a bit of a headache in amps employing that topology.
Actually that would pause me wanting to invest in that sub until some long term reliability was known. I think they would have been better off following the class D bandwagon. They make less heat anyway, which I think is a significant issue given the relatively small air space inside the box.

Def Tech's smaller 8" & 10" models the DN8 & DN10 employ Class D & for whatever reason they went for the less efficient Class H for their larger DN12 & DN15 models, the logic for the switch to Class H was mentioned in this overview/review of the Descend subwoofer series here https://hometheaterreview.com/definitive-technology-descend-series/
"Why make the shift from Class D to Class H amplifier with the larger subs?
Class D amplifiers are highly efficient (greater than 90%), allowing for cooler operation, smaller physical size, and lower power draw than Class H amplifiers.

Class H amplifiers are a variation of standard AB amplifiers that use two power rails operating on an overlapping portion of each input cycle to achieve very low distortion. However, they sacrifice efficiency by requiring more power and heat sinks to run cool. They also draw more energy to get to the same level of loudness as a Class D amplifier.

The Class H amplifiers use multiple power rails, which kick in when output-signal peaks would otherwise exceed the maximum voltage available from the Class AB amplifiers voltage rails. The result is even greater linearity (smoother, more natural sound reproduction) with extremely low distortion.

The Class H amplifiers have larger size requirements and draw more power than Class D, which is why they are used for the larger 12-inch (DN12) and 15-inch (DN15) subwoofers in the Descend Series. If your objective is to fill a large room with deep bass for low-frequency effects on movies and tight bottom-end music enjoyment - where size is not a constraint - then the Class H models produce excellent sound quality.

The Class D amps in the smaller subs are just as fast and make a proper LFE impact when watching movies. Your only limit with these is the size of the room you will be pressurizing"

Is the reviewer's claims on what I highlighted above nonsense or is there some merit to it?

Also it is really rather odd that Def Tech's design objectives were fairly low distortion & that's it, they sacrificed deep extension & high SPL to achieve this, seemingly content with their mediocre output numbers because of their choice of woefully under-powered amplification at only 500W RMS, I suppose the budget went to mostly marketing these models rather than a properly engineered unit for the discerning individual as they are mostly sold at box-mover stores like Best Buy.

 

[TLS Guy]

Def Tech's smaller 8" & 10" models the DN8 & DN10 employ Class D & for whatever reason they went for the less efficient Class H for their larger DN12 & DN15 models, the logic for the switch to Class H was mentioned in this overview/review of the Descend subwoofer series here https://hometheaterreview.com/definitive-technology-descend-series/
"Why make the shift from Class D to Class H amplifier with the larger subs?
Class D amplifiers are highly efficient (greater than 90%), allowing for cooler operation, smaller physical size, and lower power draw than Class H amplifiers.

Class H amplifiers are a variation of standard AB amplifiers that use two power rails operating on an overlapping portion of each input cycle to achieve very low distortion. However, they sacrifice efficiency by requiring more power and heat sinks to run cool. They also draw more energy to get to the same level of loudness as a Class D amplifier.

The Class H amplifiers use multiple power rails, which kick in when output-signal peaks would otherwise exceed the maximum voltage available from the Class AB amplifiers voltage rails. The result is even greater linearity (smoother, more natural sound reproduction) with extremely low distortion.

The Class H amplifiers have larger size requirements and draw more power than Class D, which is why they are used for the larger 12-inch (DN12) and 15-inch (DN15) subwoofers in the Descend Series. If your objective is to fill a large room with deep bass for low-frequency effects on movies and tight bottom-end music enjoyment - where size is not a constraint - then the Class H models produce excellent sound quality.

The Class D amps in the smaller subs are just as fast and make a proper LFE impact when watching movies. Your only limit with these is the size of the room you will be pressurizing"

Is the reviewer's claims on what I highlighted above nonsense or is there some merit to it?

Also it is really rather odd that Def Tech's design objectives were fairly low distortion & that's it, they sacrificed deep extension & high SPL to achieve this, seemingly content with their mediocre output numbers because of their choice of woefully under-powered amplification at only 500W RMS, I suppose the budget went to mostly marketing these models rather than a properly engineered unit for the discerning individual as they are mostly sold at box-mover stores like Best Buy.

No idea why they did it. Class H amps have had avery checkered history. Not that class D have been smooth going in years past. However, class D amps seem to be at a point where they are reliable.

 

[oniiz86]

No idea why they did it. Class H amps have had avery checkered history. Not that class D have been smooth going in years past. However, class D amps seem to be at a point where they are reliable.

I believe Rythmik also use Class H amps in some of their models that have 600W RMS but the top end HX series are (Hypex module) based with either 800W/900W RMS but I suppose that isn't a very good comparison as Rythmik utilise their highly regarded direct servo-based amp technology compared to Def Tech's low-cost budget amplification.

 

[shadyJ]

Also it is really rather odd that Def Tech's design objectives were fairly low distortion & that's it, they sacrificed deep extension & high SPL to achieve this, seemingly content with their mediocre output numbers because of their choice of woefully under-powered amplification at only 500W RMS, I suppose the budget went to mostly marketing these models rather than a properly engineered unit for the discerning individual as they are mostly sold at box-mover stores like Best Buy.

The DN15's extension is pretty good. It legitimately digs down to 20Hz. Few big-brand loudspeaker subs dig that deep.

 

[Danzilla31]

The DN15's extension is pretty good. It legitimately digs down to 20Hz. Few big-brand loudspeaker subs dig that deep.

Honestly it's impressive they can dig down to 20 hz on a 500 watt amp. Just shows how much the cabinet and drivers and overall design are just as important for performance as amp power

 

[TLS Guy]

Honestly it's impressive they can dig down to 20 hz on a 500 watt amp. Just shows how much the cabinet and drivers and overall design are just as important for performance as amp power

With a ported or passive radiator design the low frequency limit of the unit has absolutely nothing to do with the power of the driving amp. It is determined solely by the design of drivers and system. That is not true of sealed subs, where amp power and driver excursion have everything to do with LF extension.

 

[kini]

No idea why they did it. Class H amps have had avery checkered history. Not that class D have been smooth going in years past. However, class D amps seem to be at a point where they are reliable.

My SuperCube 8000 has a class HD (not sure what that is exactly but it has an "H" so..) and it's been used nearly every day since I bought it in 2013 and have not had a single issue other than the auto on is not very sensitive.

 

[haboscio]

I am glad this sub was finally reviewed. Own the DN12 for two years now and love it. Really love it. It sounds very clean and goes very low, 18hz before it starts rolling off (measure using REW and UMIK-1).

However, I have never managed to measure upwards of 90hz to 100hz (or 110hz) before it rolls of completely. So I am very surprised the DN15 can go up to 300hz or more.

Always thought my DN12 had a "short response runway" (18-100) because they were mean to be xo at 80hz... That how I convince myself that was the expected .

Now I wonder why I get such limited response on the DN12

PS, I usually use REW to measure from 0-24000hz on all my speakers, not just my Sub.

 

[TLS Guy]

I am glad this sub was finally reviewed. Own the DN12 for two years now and love it. Really love it. It sounds very clean and goes very low, 18hz before it starts rolling off (measure using REW and UMIK-1).

However, I have never managed to measure upwards of 90hz to 100hz (or 110hz) before it rolls of completely. So I am very surprised the DN15 can go up to 300hz or more.

Always thought my DN12 had a "short response runway" (18-100) because they were mean to be xo at 80hz... That how I convince myself that was the expected .

Now I wonder why I get such limited response on the DN12

PS, I usually use REW to measure from 0-24000hz on all my speakers, not just my Sub.

View attachment 66582

How were you driving it? Was there a crossover involved, ot were you running from a full bandwidth output?

 

[oniiz86]

I am glad this sub was finally reviewed. Own the DN12 for two years now and love it. Really love it. It sounds very clean and goes very low, 18hz before it starts rolling off (measure using REW and UMIK-1).

However, I have never managed to measure upwards of 90hz to 100hz (or 110hz) before it rolls of completely. So I am very surprised the DN15 can go up to 300hz or more.

Always thought my DN12 had a "short response runway" (18-100) because they were mean to be xo at 80hz... That how I convince myself that was the expected .

Now I wonder why I get such limited response on the DN12

PS, I usually use REW to measure from 0-24000hz on all my speakers, not just my Sub.

View attachment 66582

It is surprising that @shadyJ managed to reach a broader frequency response to around 300Hz with the DN15 as it is rated from 20Hz-150Hz, the DN12 is rated to 25Hz-150Hz & curiously the smaller DN8 & DN10 frequency response is rated at 35Hz-200Hz & 30Hz-200Hz respectively, is it typical for smaller woofers to have broader frequency responses because it doesn't make sense?

 

[oniiz86]

With a ported or passive radiator design the low frequency limit of the unit has absolutely nothing to do with the power of the driving amp. It is determined solely by the design of drivers and system. That is not true of sealed subs, where amp power and driver excursion have everything to do with LF extension.

Do you think Def Tech's drivers & DSP tuning are responsible for its middling performance numbers? Surely if they added a 1000W amp it would've brought much greater headroom in the mid-bass region like REL's HT/1510 Predator II, there is absolutely no excuse for them to charge $1799 only to include a 500W amp, it's understandable for their smaller DN12 12" variant to have 500W like REL's 1205 MkII or the Monoprice M-12 V2 but the other companies had the smart sense to employ more powerful 1000W amplification for their 15" counterparts, it truly is amazing that the Monoprice SW-15 @$300 with a 600W amp offers greater punch even if it isn't as refined sounding as the DN15.

 

[shadyJ]

It is surprising that @shadyJ managed to reach a broader frequency response to around 300Hz with the DN15 as it is rated from 20Hz-150Hz, the DN12 is rated to 25Hz-150Hz & curiously the smaller DN8 & DN10 frequency response is rated at 35Hz-200Hz & 30Hz-200Hz respectively, is it typical for smaller woofers to have broader frequency responses because it doesn't make sense?

All other things being equal, a larger cone will have more weight and thus less high-frequency sensitivity.