Hi my name is Ray, a friend of Henning’s, and I want to talk about my latest acquisition, the Velodyne SMS-1 subwoofer optimization system.


Introduction

One of the things that most people don’t realize is that the acoustics of the typical home theater room plays a huge role in the quality of the bass you get. You can spend tens of thousands on your sound system and have a top of the line subwoofer, but due to the way bass travels in your room, you may still end up with very boomy bass. In some parts of a typical room, the bass waves build up and you end up with huge frequency response peaks and dips, which is heard as very overbearing or weak bass depending on where you are sitting. Try a different seating position, and you may suddenly find your bass quality varying again. Usually smaller and medium sized rooms show most unevenness. A great deal of experimentation in placement of your sub can often help minimize the problem so the sound, and/or spending lots of money on expensive acoustical treatments is also going to help. The third way to solve the problem (for your listening location) is by equalizing your system for flat frequency response. A lot of receivers nowadays, like my current Yamaha, come with fully auto equalizer function using a supplied microphone. But these equalizers don’t do much in the bass region where all the problems occur.

Velodyne SMS-1

When Velodyne introduced their absolutely phenomenal Digital Drive line of servo subs, the subs featured one of the best, friendliest, most flexible automatic parametric equalizer systems around. This ensured the sub can be integrated into any room with great results. This didn’t help people who already owned a good sub or like me that can’t afford to drop $4000 US on a Velo DD sub. But then Velodyne answered my prayers, when they offered the equalizer part as a standalone product that can be used with any brand sub. This product is the SMS-1.

The SMS-1 sells for about $599 US street, and it’s a complete system, which comes with everything you need, a calibrated balanced microphone and cables, the equalizer unit which you connect between your sub out from your receiver and the sub. You also need to connect its outputs up to your receiver and a display, to play back the calibration tones and to display the adjustment screens. For me, since my HT projector makes noise, I hooked it up to a second display so the projector fan didn’t affect the results while I was doing the adjustments.

Before this product came out, people who wanted to do room equalization usually bought a product such as the Behringer Bass Feedback Destroyer, a microphone, and some spectrum analysis software such as TrueRTA that ran on a laptop. While this will do the job for cheaper than what an SMS-1 costs, but the SMS-1 is still worth it, as I will explain later.

SMS-1 in My Room

When I first got my HT system going in our viewing room, I realized that the bass was very bad sounding, it just seemed too boomy. I checked the frequency response with frequency sweeps and a Radio Shack sound meter, and the I realized the culprit was a huge 12dB bass peak at 44Hz, and an 8dB dip at 65Hz.

I decided to acquire an SMS-1, and it is marvelous! Once I got the hang of the operation, which is explained pretty well in the manuals, and some online SMS-1 reviews such as the one here, I was able to achieve a truly flat response. The SMS-1 has a self adjust mode which does a passable job but it isn’t overly smart, so adjusting it manually will give you superior results as you can try different combinations of settings that the machine doesn’t try. One thing I noticed is that, on my couch, each seating position yielded vastly different frequency curves, so I tried to find a set of settings that was a good compromise for all three seats. It took me about a half-hour of trying different things before I found an overall setting that seemed to work well. Every time I adjusted one parameter, I placed the microphone across all the seating positions to see how it affected the response. My system isn’t a very expensive system with modest bookshelf speakers and a 12” sub which is only rated down to about 20Hz, but I was amazed at how much better the SMS-1 has made the system sound in my room. The sub’s sound is completely integrated with the main speakers, and is very tight and realistic. The bass never calls attention to itself, and the sound is full bodied. I even like the way it sounds with music for a change.

The SMS-1 is amazingly flexible. It has a comprehensive set of inputs and outputs, even balanced connections, so it will work with any system with subwoofer pre-outs. When using it, it allows you to observe every change and its effects on the sound in real-time, as you change settings with the supplied remote control. The unit repeats a full bass frequency sweep in 1 Hz increments between 15-120Hz, and you observe the effects on the spectral analyzer screen every five seconds. The first thing I did was to choose polarity, and then the phase setting for the sub. You can very quickly toggle to the spectral analyzer screen with a press of the Test button to see the effects. The SMS-1 allows you do control the phase in 15 degree increments. I found that the phase was best at 75 degrees, and with no polarity inversion. This alone made a huge difference, as the big dip I was getting at the crossover frequency was almost completely gone. Then I adjusted the volume for the best blend to my main speakers. After that, I adjusted each of the nine bands of the parametric equalizer by changing the center frequencies, the Q (bandwidth of each slider), and the levels to flatten the frequency response as much as possible. I dialed back the peak at 45Hz and added some boost at 65Hz. One thing to note that if you have a perfect bass null that causes a huge dip, you have to be careful that you don’t overboost the signal, because a true bass null may sometimes not respond well to EQ. Otherwise, you may run out of headroom and overload your sub. If you see a dip that doesn’t get affected by boosting, you may want to try other options like adjusting the polarity, or placement of the sub itself to remove a particular null. One other feature that is great is you can choose to use SMS-1’s low and high pass crossover filters, and you can even adjust the slope of the filters for best match if you use them.

The beauty of the SMS-1 is that it has six presets, and you can program completely separate phase, polarity, crossover, and EQ curves for each preset. Each preset is named Rock/Movie/Jazz etc, and has a preset contour setting to give some emphasis for certain frequencies, but you don’t have to use them that way and can turn off the contour for that preset. So that means you can have several curves for different sources, your mood, or even for seating positions if you choose to do so. This flexibility separates this from other system you can piece together yourself.

Highlights

Some of the highlights of the SMS-1 (over other optimizer systems that you can buy or based on calibration using a laptop)

• Complete system, nothing else to buy.
• All calibrated to work together with an included microphone.
• Presets. Have separate 8 band full parametric EQ settings, volume, phase, polarity, low pass crossover frequency, low crossover slope, high pass filter frequency, contour, all settab;e for each preset.
• Both fully automatic or manual adjustments allowed.
• Remote control lets you observe the effects of the EQ at your listening position, and make adjustments from afar.
• Enough accuracy during calibration to get great results
• Very flexibile set of inputs and outputs. Can be used for a stereo system with preamp out jacks, and can supply signal to three subs. (although one EQ curve for all three).
• Transparent. Does not degrade sound like some other cheaper outboard parametric equalizers.
• Internal firmware is upgradeable down the road if you have a computer with serial RS232 connector. Won’t become obsolete.

Some people have claimed that the SMS-1 does not provide enough resolution on its spectral display to show very narrow frequency bumps. But this is a non issue in my opinion, because any such bump that narrow is going to be different as you move your head forward a few inches, and probably not audible.

Summary

For me, the SMS-1 did wonders for the sound quality. The only thing that I’m missing now is bass below 22Hz. Seeing the frequency curve drop off below 20Hz on the SMS-1 screen makes me wonder if a better sub should be my next upgrade. Maybe I need that Velodyne DD-18 after all! Honey, I’m selling the car!

All in all, I highly recommend this unit. It enables you go get the best bass possible out of your system, whether you have a modest sub or a very high end system. It made more difference to my system than any other single upgrade. For that reason, it was quite a bargain.