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[Langston Holland]

This is going to be another one of those "this is the best sub I've ever heard" reviews from a guy that is a dealer for these things. Nevertheless, I've had and heard quite a few "high end" home theater subs in the past, such as a $2k Velodyne 18" servo controlled sealed box that I fried when the demon possessed girl in Finding Nemo tapped on the aquarium.

The fact of the matter is the DTS20 is the finest sounding sub I've ever heard and felt in my life. I bought the powered model to keep things cleaner with my powered Dynaudio BM6A monitors in a 5.1 arrangement. The sub sounds like the source you hear with high quality IEM's - with the addition of shaking the house. It goes louder than is rational in a decent sized living room and is amazing with music as well as movies. It seems to sound best without "hay stack" tuning, just keep it at the same level as the lows and cross it over fairly low - 50Hz worked well in my case. It's a horn sub, thus an acoustic inverter, thus you'll probably find the need to reverse the polarity on it electrically.

Measurement Setup: (the size of this thing could threaten your marriage, but it's worth it)



Electrical output of the processed amp into an 8 ohm resistor: (with and without the low pass filter engaged)



Acoustic output with and without the low pass filter: (Danley's claim of 17Hz is accurate)



Alignment with tops: (easy to do with well designed loudspeakers)



Now some really interesting stuff... Turns out Tom has his hands in more than just loudspeakers and amps, but has spent a fair amount of time at Home Depot in the plumbing dept as well! More on that later, for now here is the internal amp installed and removed. My guess on the 4mH inductor is that it's purpose is not the function of a first order low pass filter since the amp has more than enough processing horsepower built into it already. My bet is that Tom modified the electrical Q of the driver in some way to better meet the acoustic target he had in mind.



12" Driver:



Another Look: (with clues that make one think of Helmholtz)



Interior from the Amp Side:



My modest abode: (you guessed it, the round silver thing is an acoustic absorboflector)

[Mike Pyle]

I can tell you that delivering one of those up two flights of stairs with a refrigerator dolly is quite a feat to accomplish.

[Ivan Beaver]

You are right on the PVC pipes.  They are there to tune out some distortion artifacts.  Think acoustic eq if you will-after the distortion is created-not the same as electrical eq that would pull down freq before they are "sounded".

The choke is a little "impedance trick" that Tom plays with some models of subs.  You actually get more gain/level (over the upper part of the freq range) with the choke in series than without it.

He also plays the same sort of "games" in most of the full range passive loudspeakers.  Think chokes in series with the HF and caps in parallel with the HF.  Completely backwards of what you would normally think-but it works-IF done correctly.  Done wrong-and you really mess it up.

[George Friedman-Jimenez]

Wow, that is quite a combination. I would have guessed that a 7 foot tall, 220 pound sub might be a bit massive to match with 5 Dynaudio BM6As. Threaten your marriage? I'd be more worried about your back!

My real question is about the sound. My 2 BM6s are excellent for home recording studio nearfield monitoring at 85 dBA at a listening position 6 ft from the monitors at the apex of an equilateral triangle. I am comfortable with them up to 90 dBA, maybe 95 for musical peaks. Although the specs say -3 dB at 43 Hz (40 for the BM6A), I have not found that to be the case. Mine don't sound like the white line in your last plot, down about 3 dB from the eyeballed mean at 50 Hz. Is the bump from about 55 Hz to about 70 Hz in that plot due to room modes? I have mine crossed over at 90 Hz because it sounds better, although at these moderate SPLs they could be crossed over lower, maybe down to 70 Hz or so in my studio. Those monitors are not built for high SPL or low bass. For 5 of them in a HT setting, you might be listening at 6-8 dB louder than that. My question is, how does it sound with the 50 Hz crossover and huge sub? Do you have a hole from 50 up to 70 or 80 Hz?

[Langston Holland]

George wrote on Fri, 03 April 2009:

Wow, that is quite a combination. I would have guessed that a 7 foot tall, 220 pound sub might be a bit massive to match with 5 Dynaudio BM6As.

The sub definitely outruns the BM6A's, but the 5 little Dynaudio speakers go more than loud enough for anything within reason in my living room. Sound quality is stunning.

And:

My real question is about the sound. My 2 BM6s are excellent for home recording studio nearfield monitoring at 85 dBA at a listening position 6 ft from the monitors at the apex of an equilateral triangle. I am comfortable with them up to 90 dBA, maybe 95 for musical peaks. Although the specs say -3 dB at 43 Hz (40 for the BM6A), I have not found that to be the case. Mine don't sound like the white line in your last plot, down about 3 dB from the eyeballed mean at 50 Hz. Is the bump from about 55 Hz to about 70 Hz in that plot due to room modes? I have mine crossed over at 90 Hz because it sounds better, although at these moderate SPLs they could be crossed over lower, maybe down to 70 Hz or so in my studio. Those monitors are not built for high SPL or low bass. For 5 of them in a HT setting, you might be listening at 6-8 dB louder than that. My question is, how does it sound with the 50 Hz crossover and huge sub? Do you have a hole from 50 up to 70 or 80 Hz?

Small room acoustics are nasty. You can see the effect of modes in the measurement and if you move the mic a few inches, it'll change. Measured on the ground plane outside, those Dynaudio speakers are ruler flat. It's amazing how well our psychoacoustic mechanisms adjust for this kind of thing and the net result is highly workable. The BM6A's were quite satisfying in the bass region prior to the addition of a sub - I guess 5 of 'em plus LF room gain did the trick. My problem initially with the DTS20 was reducing its output enough to keep music playback natural. Movies with bass effects seem to hype the LFE output enough that a haystack setup is completely unnecessary. I doubt I'm using even half the DTS20's maximum output capability even on the loudest movie effects...