REW Frequency Response Measurements
Using my Dayton EMM-6 microphone (calibrated to 5Hz by Cross Spectrum Labs), my M-Audio MobilePre USB sound card and laptop, I went about measuring the SB13-Ultra using Room EQ Wizard (REW) which is a great free software tool. I had already performed many of these tests for a previous review of the PB13 which uses the same amp so some of the wording I took from that review.
Frequency Response
For frequency response, I measured the sub close-mic’d by placing the subwoofer into the middle of my room and the mic on a tripod at a 90 degree angle with the tip of the mic ~0.5” from the center of the driver. Below is the frequency response graph I measured using this technique.
The response implies a +/- 3 dB measurement of approximately 21-300 Hz according to my close-mic graph. Clearly this sub can be crossed way up high if/when needed, for example, for smaller satellite and/or bookshelf speakers. Below is SVS's 2M GP measurement which shows a response of 20-460 Hz +/- 3 dB.
I asked Ed to comment on the close-mic vs 2M GP measurement and the differences, and he simply indicated that
”close-mic sealed is a good approximation of GP, but not identical.” Looking at the two graphs, they are almost identical from 10Hz through to about 125Hz (with mine not quite as flat in the 30-100Hz range but within 1-2 dB), and start to diverge much more above 150Hz with the 2M GP graph remaining flat well beyond 300Hz. Ed also sent over his own close-mic measurement graph of the SB13, and I overlaid it above my own and they were pretty much identical from 10Hz through to around 300Hz, +/- 1dB.
I also ran a few sweeps to give people an idea of what kind of room gain profile my room provides, keeping the drive level on the subwoofer amplifier the same and the trim and volume levels in the AVR the same for these sweeps, then overlaid the graphs and matched them from the crossover down. I smoothed these graphs to 1/3 Octave to line them up easier.
As you can see, my room has pretty good gain below 25Hz or so (ignore the large modal peak from around 29Hz to 50Hz and peaking at 38Hz), allowing a sealed sub like the SB13-Ultra with its shallow roll-off to extend quite low and be quite flat in my room. Another reason I love sealed subs for my application. Unfortunately as you can also see, and previously mentioned, pre-EQ my room is a mess!
Room Compensation Controls
One issue people can run into with subs in general (more so for ported subs that are tuned quite low) is that in rooms where you have substantial room gain below 30Hz or so (such as mine), you can actually end up with a rising in-room response down low (i.e., the FR rises substantially and creates a hump down low), making certain scenes or music seem boomy or muddy. The Ultra Sledge STA-1000D has a handy little “Room Compensation” adjustment whereby you can select what appears to be a high pass filter that can be set at 25Hz for “large rooms”, 31Hz for “medium sized rooms” and 41Hz for small rooms, and then you can also select whether you want the sub to roll off at 6 dB per octave or 12 dB for a more aggressive slope. Here are a few of the different modes and their effect on the FR:
Low Pass Controls
Though most will use the low pass functionality inherent in their processor or AVR and leave this function off, you can also low pass the sub itself at 31, 40, 50, 63, 80, 100, and 125Hz with either a 12 dB or 24 dB per octave selectable slope. Below you can see a few of these options and the impact on the Frequency Response:
PEQ Controls
The last adjustment I measured was the PEQ controls. The Ultra Sledge STA-1000D amp came with 2 PEQ adjustments, with available center frequencies of 31, 35, 40, 46, 50, 56, 63, 70, 80, 90, 100, 112, or 125Hz with +3 dB to -12 dB trim level, and Q range from 2 to 14.4.
Below are a few examples of what can be done with the PEQs (there are tons, but I only graphed a couple).
Combining all of the various possible tweaks above allows for an incredible amount of shaping of the final frequency response to assist getting as flat a response as possible, or a house curve if desired, etc.
Waterfall and Group Delay
Although best measured outdoors, below are the Waterfall and Group Delay charts that I measured with the sub in the middle of the room.
The waterfall remains clean throughout the sweep and group delay seems to show that the SB13-Ultra remains composed with little delay throughout the range, remaining below 1 cycle for the entire sweep. There seemed to be some anomalies with GD spiking at 13Hz and dipping at 15Hz. Again, not sure how accurate these graphs are using close-mic measurements so will be interesting to see how the compare to Josh's tests.
CEA-2010 Estimation
While I had no ability to measure CEA-2010 results as I don't have the necessary equipment/software, nor the ability to take the subwoofer outdoors and do a proper test, Ed Mullen did say that the SB13-Ultra would have approximately 6dB of additional headroom on top of the SB12-NSD at all test frequencies. So taking Josh Ricci's CEA-2010 results for the SB12NSD, here is what you should get for the SB13-Ultra.
I would have expected the PB13-Ultra to have had slightly higher deep bass measurements (below 25Hz) than the SB13-Ultra given the same amplification, similar drivers, but much, much larger box. Again, we'll see how close these are once Josh puts the SB13-Ultra through his battery of tests.
