SVS SB12-Plus Measurements and Analysis

System amplitude response, measured nearfield, scaled to 1m,

All User-accesible, Onboard processors disengaged or otherwise set inactive.

In the SB12-Plus amplitude response curve we see the typically well controlled, balanced plot we've seen in other SVSound subs. The LF rolloff, typically nearer 12 dB Oct in a sealed (acoustic suspension) system, sits at just over 24 dB oct. Processor controlled, the BASH amp never pushes the driver beyond its electrical or mechanical limits, all the while ensuring the superbly flat response as seen above.

The one "Con" item mentioned at the top of the article (Driver Mildly Noisy At Max Levels) Was, in practice, a very minor issue. (The fact that I am picking at such an insignificant nit speaks loudly for the overall quality of the product in terms of both design & construction). The noise referred to was faintly audible but only when the sub was driven hard - out to its limits - with pure sine wave test tones. Realistically, who spends their recreational listening time listening to sine waves? When reproducing music, any noise was rendered inaudible.

Electronic lowpass filter; fc = 120 (green), 80 (gold), and 40 Hz(dark red), Off (dark blue) measured nearfield, scaled to 1m.

All User-accesible, Onboard processors disengaged or otherwise set inactive.

Whether the SB12-Plus is used as part of a 2, 5 or 7 channel system an electronic lowpass filter is essential for proper integration. The constant-variable lowpass filter supplied with the sub was quiet, accurate and functioned exactly as it was designed to. Above are the response plots resulting from the filter set at 120, 80 & 40 Hz.

Along with the LP filter, the SB12-Plus sports a single-band parametric equalizer (PEQ). Designed to notch out peaks in the measured amplitude response, above we see the PEQ dialed in at 2 different frequencies. Continuously variable, it too was quiet, accurate and functioned flawlessly at notching out response peaks (depending on how set) to the tune of ~ 10 dB or so.

PEQ, variable Q function, f ~ 45 Hz, Low (blue), Mid (purple), High (red) scaled to 1m.

The adjustable Q function of the SB12-Plus's PEQ allows for the effective control of the width of the PEQ's notch, allowing the end user to custom-fit the notch with greater accuracy.

The Room Gain Control (RGC) as implemented in the SB12-Plus functions essentially as a variable slope, highpass filter. It can be set to either Small, Medium, Large or Bypass (Off). "Small, Medium, Large" refer to the size of the room, of course. The website suggests 1400ft^3 as being "Small", up to 2400ft^3 as "Medium" and anything over 2400ft^3 as being "Large". Its a nice feature and some endusers will no doubt find it useful in tweaking the sub's performance in their listening space.

The LMS graph shows the effect in dBr of the 3 settings. Measurements were done and the resulting "Small, Medium, Large" amplitude response plots were then normalized to the curve taken with the RGC bypassed. Here's the graph key:

1. Dark Blue: Reference Plot

2. Purple: Large

3. Green: Medium

4. Mustard: Small

Room Gain Control. Reference response curve, RGC Bypassed (Blue), Large (Purple), Medium (Green) & Small (Mustard)

By normalizing the response plots its easy to see exactly how and where each setting rolls off the lowest portion of the sub's acoustical output.

System Max Output (Blue curve), measured anechoically @ 2m, no scaling or smoothing.

LP filter engaged and set @ ~ 120 Hz.

Come time for assessing the SB12-Plus's max output capabilities the sub was taken to a nearby anechoic chamber to which I have access (schedule permitting). Measurements were done at 2m, on axis with the LP filter engaged and set to ~ 120 Hz. All other user-accesible, onboard processors were disengaged or otherwise set inactive.

First run was done at a respectable mid band level of just over 94 dB spl. Max db spl sat just above 106 db spl, midband and as before, the measurement distance was 2m. It's evident that as the unit is driven harder the LF knee of the system's response is pushed progressively higher. (Compare these plots to the first plot done at the top of the series) Thus the unit ensures the driver survives to rock another day.