Velodyne SMS-1 Features and Using the System

Using the System: Breakdown of Features

Though the setup process for using the Velodyne Subwoofer Management System is direct and uncomplicated, there are several options that should be understood so that you get the most out of the system. You can also negatively affect the bass management in your system if you are not careful to set the low pass crossover frequency correctly (or defeat is as we’ll point out).

Inputs and Connections

While the front of the SMS-1 only sports a power button, LCD panel and XLR microphone input, the rear of the unit is loaded for bear. A balanced LFE Input and Output (yes, just one) plus additional Mic Input garner the rear of the unit in addition to an RS-232 Input and Output and IR Input. S-video and composite video connections are provided to get an on-screen display which is necessary for making adjustments on the SMS-1. There are three unbalanced “LFE” outputs (for attaching up to 3 subwoofers in parallel).   An EQ output provides the necessary sweep tone and calibration outputs which get routed to your AV processor/receiver.

Though we would have liked to have seen the ability to independently EQ two subwoofers in the SMS-1, we recognize it would complicate setup for most end users of single subwoofer systems.  In some cases, EQ’ing just one sub in a multi subwoofer system will do the trick nicely.  For instances where additional EQ’ing is needed, the SMS-1 has the ability to be daisy changed to additional units to make it a reality.    A “Thru” connection (stereo) routes pure, un-EQ’d signal out of the SMS-1, allowing for daisy-chaining of multiple units. The unbalanced “Output” RCA connections provide an 80Hz 6dB/octave high pass crossover for use with systems that do not provide adequate bass management. Lastly, as far as unbalanced RCA connections go, there are a pair of LFE inputs, with a mono Right channel input for those in the majority who have mono subwoofer outputs from their receiver or processor. Speaker level inputs (bare wire terminals) and a 12VDC trigger are also provided.

Connections a-plenty reside on the rear of the SMS-1

Understanding the Real-Time Frequency Response Graph

Upon entering the Setup system a low frequency (15Hz – 200Hz) sweep tone will begin. This will allow you to see how the low frequency room response is measured at the microphone position. As best we can tell, in accordance with comparative LMS measurements, this is a 1/3-octave smoothed response giving users a general idea of both the overall bass response of the system along with a look at how well the subwoofer integrates with the main speakers at the crossover point.

The System Settings

The system settings menu is where you should start in order to ensure you are properly configured prior to making manual EQ adjustments. This is the place where you can really tweak the system and fine tune what the SMS system will do for each preset mode.

LOW PASS XOVER FREQ/ LOW PASS XOVER SLOPE
This function sets the frequency above which the SMS-1 will apply the LOW PASS XOVER SLOPE (set as any range from 15Hz – 199Hz in 1Hz steps). The LOW PASS XOVER SLOPE is configurable from 6 – 48dB/octave in 6dB/octave step sizes. We recommend DEFEATING this function by placing the cursor over the LOW PASS XOVER FREQ and hitting the “Reset” button on the remote control. This will cause the XOVER FREQ and SLOPE to register “OFF” as their value across all presets. As the majority of users will have adequate bass management present on their receivers, there is no reason to either double up or defeat the bass management functions of the AV processing device. In fact, it is highly likely that by disabling bass management on the receiver (as recommended by Velodyne’s SMS-1 User Manual) you could cause problems such as missing frequency response from surround and center channels, overdriving surround channels to distortion, and wasting amplifier power by driving full range audio to loudspeakers that do not support it.

SUBSONIC FREQUENCY/SUBSONIC SLOPE
This setting is typically not needed for most systems, but enables the user to cap the lower frequency limit that the SMS-1 will allow. This could, for example, save a delicate (ie. underperforming) subwoofer from getting too much low frequency information that would otherwise distort and possibly damage the driver or amplifier. It can be configured from 15Hz – 35Hz in 1Hz increments. The 15Hz default will be sufficient for most systems attempting to get the lowest possible frequency response. The SUBSONIC SLOPE can also be set to either 6, 12, 18, 24, or 48db/octave.

PHASE
This self explanatory setting allows you to adjust the phase of the SMS-1’s output signal from 0 to 180 degrees in 15 degree increments. Phase can be utilized to effectively “delay” the subwoofer signal and better time align it to the system or create a flatter overall room response.

POLARITY
You can switch the polarity of the subwoofer output to + or – which flips the subwoofer out of phase by 180 degrees.

VOLUME
The Velodyne Subwoofer Management System allows each Preset to have its own volume setting. This is good, for example, in the event that you simply want your subwoofer set higher for action/adventure movies (Preset 1) or Pop/Rock (Preset 3).

CONTOUR FREQUENCY/CONTOUR LEVEL
The point of this setting is to allow a “bump” or “cut” in the frequency response in order to accentuate a small frequency area for particular presets. You could use this to give an extra boost around 60Hz during Action/Adventure movies for example – or to pump up the 40Hz response for your favorite Hip Hop tunes (no, there isn’t a ‘Hip Hop’ preset, but you get the idea).

The final controls on the System Settings screen are 12V TRIGGER MODE and NIGHT MODE VOLUME. The first setting shuts off the SMS-1 until a 12V DC current is fed to the 12V trigger input on the rear of the unit. The latter, is intended to provide a night listening mode which could cap the subwoofer volume so as to keep late night movies from waking the other household members.  We initially thought NIGHT MODE was inoperable since engaging it at even its lowest setting didn’t appear to make an audible difference when listening to music.  It wasn’t until we popped in the DVD Toy Story 2 and listened to the opening scene where Buzz Lightyear was blasting his rockets into space that we heard our subwoofer cap off its output during the loud passages.  Measuring with an RMS meter to confirm we watched the steady state signal of 200mVrms from Buzz’s rockets fizzle out to around 20-40mVrms with NIGHT MODE engaged at 10%.  This feature acts more like a limiter than an active gain control or compressor, which was what we thought its function was supposed to be prior to testing it.

Using the 8-band Parametric EQ

Below the real-time system response graph are 8 sliders which can provide +6 dB gain or -12dB cut. Once you have optimized subwoofer placement and done as much as possible to optimize the physical room and listening position, you can raise and lower the sliders to help smooth out the in-room low frequency response. We recommend mostly cutting frequencies, though if you can achieve a better in-room response by adding a dB or two of gain in some areas (without negatively affecting the secondary listening positions) then feel free to try that as well. Rarely will dramatic EQ boosts improve overall sound as you cannot dramatically increase what is not there to begin with.

The “Test” button on the remote control sends the user back and forth between the System Settings menu and the System Response screens.

When using the EQ you can jump from band to band by arrowing left and right. Pressing the up/down navigation/arrow keys while on an EQ band allows you to raise and lower the gain at that frequency. Clicking the ‘Select’ button will allow you to “move” the frequency and you can select the ‘Set’ keys to raise and lower the Q value.