- Written by Jim Clements
- Published on 05 June 2013
Design of the SVS SB13-Ultra Subwoofer
The SVS SB13-Ultra is a fairly compact, high output sealed box subwoofer. Subwoofers can be designed in any number of ways but the two most common design concepts are either ported (bass reflex) or a sealed box (acoustic suspension). Ported subs tend to have a lower tuning frequency and a faster roll off below the tuning frequency while sealed designs normally have less extension but with a gentler roll off. In the hi fi and home theater belief systems, ported subs are considered higher output and less precise in their reproduction. They are generally viewed as optimal for movie effects while sealed subs, with their "tighter" and more controlled response characteristics are considered the better choice for music systems.
But SVS wondered what it would take to develop a sealed sub that would exploit cutting edge technology to bring you the best of both design concepts? Thus the SVS SB13-Ultra was born.
The SVS SB13-Ultra has been designed from the ground up to be a high quality and high performance compact subwoofer. The engineers at SVS call this a "Fully Optimized Design" which means they considered every aspect of the system - driver, amplifier and cabinet in order to achieve the optimal performance objectives.
The SVS SB13-Ultra is roughly an 18" cube. Don't be fooled by its smallish footprint as this bad boy clocks in at 92 pounds net! This may well be the densest subwoofer I have ever had in my system. I was able to load and unload the box from my car. I also singlehandedly unboxed the subwoofer and wrangled it into position in my listening room. That will be that last time I do that. A quality hand truck is now at the very top of my shopping list!
SVS told me that there are two major keys to making a great sealed box subwoofer – lots of clean power and lots of cone excursion. Let's start with a breakdown on the driver. It starts with a 13.5" Rohacell-backed pulp and fiberglass layered cone. The motor sports a 43 pound magnet structure. The 3" diameter voice coil is bifilar wound to reduce impedance. This voice coil sports dual 9" spiders that are spaced ¾" apart. This prevents rubbing or twisting of the voice coil. The driver features a gap extension plate to balance the force/displacement curve in the forward stroke direction. Additionally, the voice coil assembly is designed so it can't "bottom out". The stitched surround has a parabolic cross section. The whole assembly is supported by a die-cast aluminum basket.
So what does all this jargon mean to you, the consumer? It means that this sub's driver has a very light and stiff cone. The motor can handle gobs of power in a controlled fashion with a peak excursion of 50mm! In the end, you can rest assured that you are getting substantial, linear output capabilities and very low distortion.
The conservatively rated Class D plate amp produces 1,000 watts RMS with a peak rating of 3,600 watts. It has a built-in control circuitry that is tailored to the system's response. In this regard, SVS fully exploits one of the primary advantages of a powered speaker design – the ability to closely match the amplifier to the system. Furthermore, a high pass filter is not required for protection due to the sealed box design.
SVS has designed a unique limiter circuit for their subwoofers. Most limiter circuits chop off the first dynamic peak but let the tail end of a given passage come through at full power. SVS's limiter circuit is is different. It is designed to equally attenuate each section of a passage, thereby retaining the dynamic shadings of the music.
The amp has a (manual) dual band parametric equalizer, room gain compensation control with adjustable frequency and slope along with adjustable digital delay on the main speaker line-level outputs to time-align the speakers and subs. All this is controlled by a single rotary knob and rear-panel LCD display.
The grille is a heavy duty perforated steel cage that is a perfect aesthetic fit with the subwoofer's extreme image. The sub is available in either black ash or gloss black. My review unit was gloss black. The quality of the finish was exemplary.