Emotiva X-Ref 12 Subwoofer Measurements and Analysis
The Emotiva X-REF12 subwoofer was measured outdoors sitting on the ground with the microphone placed 2 meters from the front lip of the cabinet. The driver was facing directly at the microphone. The low pass filter was disabled and the subwoofer volume was set to maximum for all testing, except for those tests purposely conducted to examine the effects of the built in functions or different operational modes.
The overall approach to this testing along with the equipment and software used is outlined in the article here: Powered Subwoofer Testing Outline and Procedures Overview
Emotiva X-REF 12: Effect of Low Pass Filter Settings
Above is the effect of the low pass filter on the Emotiva X-Ref 12’s response. It exhibits a textbook 24dB octave roll off and corresponds quite closely to the indicated value specified in the DSP unit.
Emotiva X-REF 12: Effect of Movie EQ Preset
Above is the effect that engaging the movie EQ preset on the X-REF 12 has on the overall response. It provides a roughly 5 to 6dB overall level boost centered at what looks like 45-50Hz.
Emotiva X-REF 12: Parametric EQ Settings Example
Above is a rather large sample of the settings available with the two built in parametric EQ’s provided by the DSP unit. There is a large range of flexibility offered and these should help address problem room acoustics or adjust the sound to a particular listeners taste. I would’ve liked to have seen a little bit sharper notches available though. Still 2 bands of PEQ on a product in this price range are out of the ordinary already. Most subwoofers in this price range will have little to no internal adjustable EQ let alone 2 bands and built in DSP.
Emotiva X-REF 12: Basic Frequency Response as Tested
The basic response of the X-Ref 12 as tested is shown above. This is with the unit set to the Flat EQ preset and with the low pass filter defeated. The unit is sharply filtered below 30Hz and also exhibits a notable upper range roll off as well probably due to inductance in the driver motor system. Emotiva states the typical in room response of the X-Ref 12 as 20-200Hz with no tolerance given. As measured the X-Ref 12 fits within a 6dB total window from 28-109Hz. The -10dB point from the peak at 60Hz occurs at about 200Hz on the top end and right below 26Hz on the low end. The response is down over 20dB by 20Hz. The roll off of the X-Ref 12 appears to be about 30dB an octave acoustically which indicates that there is an 18dB and octave high pass filter used in addition to the natural 12dB an octave roll off of the sealed alignment. The natural roll off likely starts near 45 or 50Hz but boost EQ is used to extend and flatten the response till 30Hz.
Emotiva X-REF 12: Waterfall Decay
Emotiva X-REF 12: Group Delay
The waterfall decay and group delay charts are well behaved overall and indicate only a moderate amount of delayed energy near 30Hz which should correspond to the high pass filter and EQ boosting to extend the X-Ref 12’s response.
Emotiva X-REF 12: Long Term Output Compression
The X-Ref 12 maintains its response shape and accurately tracks the increased volume of the input signal up until the 100dB nominal sweep level. At the 105dB sweep level some compression was in evidence between 25-35Hz where its response is EQ boosted. Increasing the level another 5dB to a nominally 110dB sweep produce barely 1dB of extra output over much of the range indicating that the X-Ref 12’s limiter was interceding heavily at that point. During this the X-Ref 12 maintained its composure very well and barely emitted more than a slight roughening or distortion of the sound near 30Hz.
Emotiva X-REF 12: Output Compression Magnitude
In the measurement above is the same information from the previous output compression measurement but shown in a way that only indicates the amount of compression that is occurring.
Emotiva X-REF 12: Maximum Long Term Output Level
Looking at the maximum long term output achieved by the X-Ref 12 during the output compression testing reveal that it maintains its basic response shape pretty well but the maximum output level reached is modest. This is unsurprising since the X-Ref 12 is such a small unit overall.
Emotiva X-REF 12: Total Harmonic Distortion
Emotiva X-REF 12: 110dB Sweep Distortion by Component
The distortion results for the Emotiva X-Ref 12 are good and follow the usual trends for a sealed alignment. At the maximum output level reached during testing the distortion is below 10% everywhere above about 43Hz and the distortion is dominated by the second harmonic which is good since the second harmonic is generally held as the least audible and inoffensive. Below 40Hz where the excursion increases so does the distortion and it quickly exceeds 30% THD below 30Hz. Again this is not unusual for a small sealed subwoofer alignment.
Emotiva X-REF 12: CEA2010 2 Meter Groundplane RMS Results
Emotiva X-REF 12: CEA2010 2 Meter Groundplane RMS Comparison
Looking at the results for CEA-2010 testing presented above we again see that the X-Ref 12 can produce more than 105dB at the 50hz band and above with a gradual decline below that point. This is typical of sealed subwoofers. At the 31.5Hz band and above the X-Ref 12 is amplifier limited and produces output levels commensurate with its size and price. I could not obtain a passing result below the 20Hz band where a maximum passing output of 81dB was recorded. The very steep roll off of the X-Ref 12 below 30Hz prevents useful output much below 25Hz in any case.
For comparative purposes, I took Gene’s reverse sine-wave rms sweep data from his Ultra 12 review, scaled it to 2 meters and charted it next to my max long term output tests of the X-Ref 12. Although both of our test rigs are different, our testing results are calibrated and consistent so this is a fairly accurate apples to apples comparison.
|Frequency||X-Ref 12||Ultra 12|
|20 Hz||83 dB||84 dB|
|25 Hz||95 dB||92 dB|
|30 Hz||100 dB||96.5 dB|
|40 Hz||103 dB||101 dB|
|50 Hz||105 dB||106 dB|
2 Meter RMS Reverse Sine Sweep Data Comparison
As you can see the X-Ref 12 has a significant output advantage (between 3-4dB) from 25-30Hz but does give up a couple of dB above that due to the X-Ref 12’s less efficient driver.
You want it where your head is at the listening position.
that's what I have been doing,I must have misunderstood your post
With the microphone and subwoofer both on the ground
so you're saying it's better to put the calibration mic on the floor for sub calibration ?.
You want it where your head is at the listening position.
Essentially yes but your listening placement and other boundaries and objects also matter. This is why groundplane measurements are done the way that they are. With the microphone and subwoofer both on the ground in theory you only get one perfect reflection of energy from the ground through the bass range. This is known as half-space and provides basically 6dB of gain over a reflection free anechoic environment. If you were to raise the microphone the subwoofer, or both away from the ground you would start to see some response changes due to the distance from the boundary represented by the ground.
so you're saying it's better to put the calibration mic on the floor for sub calibration ?
I have 2 Emotiva ultra 12 subs,one on the front wall facing into the room,and one on the rear wall facing into the room,each is about 5 feet from a corner,and I have a Auralex gramma under each one,
and I use a Anti-Mode 8033,I have always put the mic on a tripod in the main seating area at ear level.