- Written by Ross Jones
- Published on 25 April 2012
Design of the Emotiva X-Ref 12 Subwoofer
The X-Ref 12 is a compact, nearly cube shaped, sealed design subwoofer. It uses a 12" long-throw driver, with a three-inch vented motor structure made from what Emotiva calls a proprietary para-aramid blended fiber cone. The X-Ref 12 is powered by a 600 watt rms (1,000 watt peak) amplifier. Emotiva claims "typical in-room frequency response" of 20-200 Hz, although the frequency response graphs on Emotiva's website show that the sub's frequency response is flat down to about 29 Hz, at which point usable output drops off. This is to be expected with sealed subwoofers, which typically trade off low frequency extension for flatter, more accurate frequency response.
As mentioned above, the X-Ref 12 is DSP-powered; the controls are contained in an ingenious rotary encoder located on the top of the enclosure, lit by a backlit LCD display.
The rotary encoder incorporates many of the functions you'd normally find on analog dials inconveniently located on the back panel of a sub, such as phase control, crossover point and volume. Having precise digital control over these parameters in a readout visible from the top of the subwoofer is a very useful feature.
However, the real guts of the DSP control is in its EQ capabilities. The X-Ref 12 includes two pre-set EQ curves called "Music" and "Movie." The sub includes remote triggers that can automatically activate these modes when the appropriate input is selected from your pre-pro or receiver (assuming your pre-pro has the necessary trigger outputs and set-up). Music mode is flat, with no EQ adjustments. Movie mode incorporates Emotiva's version of a house-curve, which adds about 6 decibels of bass boost at around 45 Hz. House curves are a sensitive subject. Some people object to anything that artificially changes the sound from that originally recorded on the soundtrack. For others, who like a little extra oomph with their movies, the house-curve gives them a fuller, robust bass sound. With the X-Ref 12, you can please both types with a twist of the rotary encoder.
Besides the pre-set modes, the X-Ref 12's DSP processor also includes a two-band variable parametric equalizer. The parametric equalizer allows the user to adjust a particular frequency (between 25-150 Hz) with up to a 6 dB boost or 12 dB cut, as well as set the "Q" or width of the adjustment, from 0.5 to 5.0 in 0.1 steps. A "Q" setting of 1.0 translates into a width of one octave. Used properly, the parametric equalizer can be a great tool for reducing peaks in the subwoofer's frequency response caused by standing waves. Used poorly, to try to overcome a null (or dead spot) in frequency response by cranking up the volume, is at best an exercise in futility and at worst leads to a blown sub (although the Emotiva's DSP is designed to prevent dangerous overloads).
Sub-based parametric EQ occupies a kind of middle ground in dealing with room response. There are dedicated subwoofer EQ/room correction units such as Velodyne's SMS-1/MIC-5, and until recently, SVS's AS-EQ 1 (now discontinued as its functions are essentially identical to those found in products with Audyssey's MultEQ XT32). I suspect that most consumers rely on their receiver or pre-pro's built-in EQ/room adjustment software, such as the various versions of Audyssey found in many models, or proprietary systems such as Pioneer's MCACC, Anthem's ARC, and Emotiva's own EmoQ, even though these systems vary in the way they handle low frequency response. The best ones use a calibrated microphone that can take measurements at multiple locations in the listening room, and create adjustments in both the frequency and time domain that create the best overall sound for the entire room.
A sub-based EQ system, such as that in the X-Ref 12, relies on the user setting the frequency, Q (bandwidth), and cut/boost level. I'm guessing that the typical buyer of an X-Ref 12 uses some form of measurement tool to get a sense of the room response at the main listening position, and then dials in the appropriate EQ adjustment. If the main listening spot has an unusual peak (which is pretty common in many rooms), the Emotiva's EQ can cut the offending frequency and smooth out overall response at that position.
Because most of the parameter adjustments normally found on the back of a sub (volume, phase, crossover) are handled by the Emotiva's rotary encoder, the panel panel is pretty sparse. There is a detachable IEC power connector, which automatically detects either 120 or 230 volts, a main power switch, and two unbalanced RCA inputs. The X-Ref 12 also has a balanced XLR input, and balanced XLR output to daisy-chain more than one sub. Balanced input and output are not features usually found on a sub in this price range. Finally, the back panel has a 12 volt trigger to turn the Movie EQ mode (assuming your pre-pro supports such a feature).