With a sub that’s 22.5 inches deep, your placement options may be limited because there are only so many places it can fit. I was able to put the DD-15 Plus into my usual “subwoofer sweet spot,” the place where a single sub sounds best from my listening chair. However, the front of the DD-15 Plus stuck out almost a foot further into the room than a typical sub does. I used it with several different speakers, including home theater systems set up around the Sonus Faber Liuto towers and MartinLogan ElectroMotion ESL electrostatic speakers. In all cases, I chose “small” speakers in my receiver’s bass management menu, so the DD-15 Plus would be handling all the bass.
For inputs, the back panel has stereo balanced XLR and unbalanced RCA jacks and binding posts for speaker-level connection. Stereo XLR and RCA outputs are provided for feeding the amplifier for your main speakers, so you can use the sub’s internal crossover to filter the bass out of the main speakers. More stereo and XLR and RCA outputs allow connecting more DD-15 Plus subs in a slave/master arrangement, so the master sub’s Auto-EQ optimizes the sound with all of the subs active. Video outputs are also provided so you can see the sub’s menus and measurement graph on a TV instead of on the PC.
Despite the availability of so many connections, I needed just one RCA input to connect the DD-15 Plus to my system.
You can choose from three setup procedures: Self-EQ, Auto-EQ and PC.
With Self-EQ and Auto-EQ, you plug the included microphone (which looks identical to the Dayton Audio EMM-6 budget measurement microphone) into the sub’s front panel, place the mic in your listening chair using the included stand, then press the Auto EQ button on the front of the sub. The difference between Self-EQ and Auto-EQ is that the former uses test tones generated by the sub itself, and it adjusts only the sub’s internal EQ. Auto-EQ uses a test tone from an included CD; in addition to performing the EQ function, it also evaluates the bass response of your main speakers and adjusts the DD-15 Plus’s crossover frequency, phase and level to suit.
The PC setup is of course more complicated. You install the app on your PC from the included CD, connect the sub to your PC through the sub’s front USB input, then run the app. You’ll also have to play the test tones from the CD. The screen shot included here shows the basic control interface (as well as the settings I arrived at in my room). The PC screen shows the measured response at the microphone. You then adjust EQ points onscreen until the response is as close to flat as you can get it. The level, frequency and Q (bandwidth) of the EQ points can be separately adjusted.
Although the EQ and tuning capabilities of the DD-15 Plus may seem mindblowing, there’s one major limitation: As supplied, the sub allows you to tune the sound only for one seat. Some other systems, such as Audyssey MultEQ, let you average the result from several microphone positions, so you get a result that’s balanced for multiple seats. However, for an extra $799 Velodyne can provide the Mic-5 Microphone Averaging System, a set of five mics and a junction box that lets the DD-15 Plus’s Auto-EQ function average the results over five seating positions. Seems like a lot to spend for a rig you may only use once, but it’s certainly a far better investment than a lot of the audio tweaks out there.
There’s one feature the DD-15 has that the DD-15 Plus omits: servo control. In essence, this control let you adjust the distortion-limiting functionality in the DD-15’s electronics. I liked it because it functioned as a “tight/loose” control, letting the listener find the right compromise between a tight/precise sound and a loose/fat sound.
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