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Secrets Product Review

Velodyne SMS-1 Digital Drive Subwoofer Management System

Part I

December, 2005

Roger Welch

Introduction

When Velodyne launched the Digital Drive

series of subwoofers, they created a near

perfect bass solution in a box. The combination

of a high-powered, low distortion subwoofer,

coupled with sophisticated digital servo-control

and parametric EQ allowed the sub to be

seamlessly integrated with virtually any system

and in any listening room.

While there was great convenience in having all

this functionality in the one box, Velodyne

recognized that many of the unique design

features of the Digital Drive system (excluding

the digital servo), could be extracted and

released as a standalone product, enabling

owners of a wide range of other subwoofer

makes and models to benefit from DSP (Digital

Signal Processing) technology without having to

invest in a whole new subwoofer.

Most subwoofers suffer from problems caused

by the room into which their subwoofer is

installed. The laws of physics dictate that the

room will tend to emphasize some frequencies

compared to others due to a combination of the

effects of boundary gain, room gain, and room

modes. Everyone’s room is different, and it is a

sad fact of life that the bigger and better the

subwoofer you use, the worse the problems can

seem.

Historically, you could fix some of the issues by

Specifications:

•

Operating Frequency Range: 15 Hz - 200

•

THD: < 1%

•

Digital Phase: 0° to 180° (variable in 15°

increments)

•

High-Pass Crossover: 80 Hz (6 dB/octave

slope)

•

Low Pass Crossover: 15 Hz - 199 Hz

(adjustable) 6 dB/octave initial, to 48

dB/octave ultimate

•

Subsonic Filter: 15 Hz - 35 Hz (adjustable)

12 dB/octave initial, to 48 dB/octave

ultimate

•

Polarity: Adjustable (+/-)

•

Auto On/Off: Yes

•

Inputs: Balanced (XLR), Line-level (RCA),

Speaker-level

•

EQ Outputs: Line-level (RCA), Balanced

(XLR)

•

Other Outputs: Thru-put (RCA), High-Pass

(RCA) (fixed at 80 Hz)

•

Crossover Bypass: Yes

•

Dimensions: 2.0" H x 16.5" W x 6.5" D

•

Weight: 17 Pounds

•

MSRP: $749 USA

Velodyne Acoustics

www.velodyne.com

Summary of content (17 pages)

PAGE 1
Secrets Product Review Velodyne SMS-1 Digital Drive Subwoofer Management System Part I December, 2005 Roger Welch Introduction When Velodyne launched the Digital Drive series of subwoofers, they created a near perfect bass solution in a box. The combination of a high-powered, low distortion subwoofer, coupled with sophisticated digital servo-control and parametric EQ allowed the sub to be seamlessly integrated with virtually any system and in any listening room.
PAGE 2
engaging the services of a professional audio calibrator using expensive instrumentation to optimize the placement of the subwoofer(s) and/or employ some serious room treatments. Unfortunately, these seldom proved totally acceptable or effective, due to aesthetic or practical constraints, meaning that sub-optimal performance was all too often the norm. DIY attempts without proper instrumentation were always liable to be even more hit-ormiss.
PAGE 3
Next come three LFE Output RCA sockets that can be used to connect up to three subwoofers. Each produces an identical signal. Composite and S-Video TV outputs are provided, one of which should be connected to a TV or other display device for visualizing the EQ curves and accessing the menu structure. There is a 9-pin RS232 input socket to allow serial control by Crestron/AMX-type universal remote controls as well as the ability to upload software upgrades using a PC.
PAGE 4
Secrets Product Review Velodyne SMS-1 Digital Drive Subwoofer Management System Part II December, 2005 Roger Welch Set-up The SMS-1 can be connected to an existing system in several different ways. I chose to evaluate it for this review in the configuration that I believe will be most commonly used. That is to control a single subwoofer in an A/V system, driven at line-level from the suboutput jack of the SSP/receiver which performs all the bass management.
PAGE 5
I configured for stereo use with bass management. I kept the 63 Hz, 24 dB/octave crossover and slope settings that I normally use in the SSP with my floor-standing main speakers. The initial screen of the OSD is shown below. It tells you the current subwoofer volume setting (00-99) and which preset (there are six to choose from) is currently selected. Pressing Menu and/or 1-2-3-4-5 on the remote control (shown below) brings up the sweep test screen OSD.
PAGE 6
Secrets Product Review Velodyne SMS-1 Digital Drive Subwoofer Management System Part III December, 2005 Roger Welch I had previously determined what I felt was the best position for the subwoofer using a good deal of trial and error, just listening by ear. This turned out to be between my front left speaker and the center channel. I had also calibrated the relative subwoofer level using Video Essentials and a Radioshack SPL meter. Until the arrival of the SMS-1, this was the best that I could achieve.
PAGE 7
Since several of the peaks and dips in this response are significantly above the crossover frequency (63 Hz), the SMS-1 will be powerless to do anything about them because it can only influence what the subwoofer produces. The first stage in improving the sub’s performance was to get it positioned in the optimum location.
PAGE 8
reversed. I next turned the main speakers back on and proceeded to smooth the response around the crossover frequency using the polarity, phase and low-pass crossover controls on the SMS-1. These can be found on the second OSD screen page which is entered by selecting NEXT. This screen initially looks quite complicated, but if you restrict yourself to making changes in the Setup column only to start with, these get copied automatically across all the presets.
PAGE 9
Secrets Product Review Velodyne SMS-1 Digital Drive Subwoofer Management System Part IV December, 2005 Roger Welch Equalization There are a number of different approaches to digital room correction in use these days. Some of the more sophisticated techniques used in modern receivers and SSPs attempt to reduce the extended decay times at the room’s modal frequencies by subtly modifying the original signal (modal equalization).
PAGE 10
Realizing that there are some customers who will not want to get into the intricacies of the manual EQ set-up straight away, Velodyne equipped the SMS-1 with a couple of automated EQ set-up modes to minimize the effort required. In order to use the simplest of these, the Self-EQ mode, you strictly only need to hook up the microphone to the SMS-1 and the LFE output to the subwoofer. However, I would always recommend connecting the video output to your TV as well.
PAGE 11
That represents a further incremental improvement, and if I didn’t want to venture any further into the set-up process, I could just decide to leave it at that. Click Here to Go to Part V.
PAGE 12
Secrets Product Review Velodyne SMS-1 Digital Drive Subwoofer Management System Part V December, 2005 Roger Welch The next level of automation is called Auto-EQ. This is engaged from the sweep screen by placing the cursor on the Manual field and pressing Select on the remote. Again, the sliders get reset to default 1/3 octave frequencies and the SMS-1 starts to move them up or down over 25 sweeps, trying to flatten the response to within ± 3 dB limits.
PAGE 13
processes. The SMS-1 had chosen to apply a +6 dB boost at 20 Hz to try and raise the response where the sub is naturally starting to roll off. Applying such a powerful boost at a low frequency like this would be very likely to exceed the sub's capabilities, for very little actual improvement in bass extension. After using either of the automated EQ set-up processes, it is a good idea to apply a sense check to the settings and manually correct anything obviously unwise such as this.
PAGE 14
From experience, I know that the 85 Hz dip in my room cannot be corrected by applying an EQ boost even if I were to set my crossover higher and use the SMS-1 to attempt it. So I just choose to live with that until I can employ some other room treatments to correct the problem. Other than that, I am very happy with the smoothness of the response that I have achieved, despite the fact I have had to use a couple of fairly strong boosts in the 50 Hz – 60 Hz range.
PAGE 15
Secrets Product Review Velodyne SMS-1 Digital Drive Subwoofer Management System Part VI December, 2005 Roger Welch There are just a few more features worthy of mention on the third OSD page, as shown below. Having configured the Setup column of global parameters, you can Lock them so you won't accidentally change them. As well as all the settings mentioned so far, each preset can have its own default Volume and Contour settings.
PAGE 16
can be used to boost (or cut) a single band around a specific frequency. For example, with the factory default settings, Preset 1 (Action/Adventure) has its default volume raised to make the sub slightly "hot". The boost of +5 dB applied around 35 Hz gives an additional kick to certain special effects. The precise values used in each of the presets are entirely up to you, and any of them can be changed to suit your own tastes. Preset 6 is treated differently, because all the equalization is disabled.
PAGE 17
This is by no means the fault of the SMS-1. Even without it, I could have produced a similar effect by running the sub too hot. Nor is it a criticism of the sub, since every sub has a finite limit beyond which it is not sensible to push it. It is simply the case that the combination of the EQ boosts correcting dips in the response, taken together with Preset 1 which runs the with a +5 dB contour boost at 35 Hz, proved too much. The manual contains several warnings to this effect.