Feature Article

A Tale of Two Subwoofers: How I Achieved Bass Nirvana with the Velodyne SMS-1 Digital Drive Subwoofer Management System and MIC-5 Multiple Microphone System

Part II

October, 2006

John E. Johnson, Jr.


The Results

What  . . . a . . . difference!

All of the deep, intense bass that I had loved from before I installed the room treatments was back.

The room and corner loading, along with reverberation that were in the room before, were actually distortion, but I had liked the effect.

Now, I had the pleasure returned to me, but it was accurate. Not loading. Not reverberation.

In fact, this turned out to be the most significant change to my subwoofer setup that I have made in years. It is really hard to put into words how much improvement this represented.

The MIC-5

At CES 2006, Velodyne showed a new product they call the MIC-5, or Bass Management Hub, priced at $799.

It consists of five microphones, with XLR balanced output, five microphone stands, cables, and a junction box that supplies the 48 volts that the microphones require.

You connect from one to all five microphones to the junction box, connect the output of the box to the SMS-1 or other EQ system, which can include such systems that are built into receivers and processors, and acquire the EQ data.

The idea is that instead of getting the EQ for just one listening position, you get it for an average over several listening positions.

Shown below is the setup that I used, with two microphones, one for each listening chair. The blue arrows point out the two microphones, the yellow arrow points out the junction box, and the black arrow indicates the SMS-1 in the front left subwoofer position that the junction box output was connected to.

Here is a close-up photo of the junction box. A 9 volt battery powers the box. You plug in the microphones that you will be using, press the power button, and use the Mic Select button to select how many microphones will be used. The blue LEDs indicate that the two microphones are powered and ready to go.

I think the MIC-5 will be a dynamite component in the custom installer's arsenal of tools. If the customer has one listening position, one microphone is used, if two, then two, if five, then all five.

For my setup, I finally settled on just one microphone, because I am the only listener 99% of the time. However, the SMS-1 has memory settings for several different EQs (you will need the TV connection so you can see the menu screen to do this, by going into Setup). When you are the only one in the room, sitting in your main chair, one EQ memory setting. If you are sitting in a different spot, a second EQ memory setting. When there are others, with you in the chair and them on the couch, a third EQ memory setting. The MIC-5 lets you deal with the third setting by using several microphones to set the optimal EQ for people simultaneously in the room, in different places.

Be Realistic

Now don't go and try to EQ a large home theater room at 100 dB SPL down to 20 Hz with an 8" subwoofer. The SMS-1 is a fine product, but it can't work miracles by defying laws of physics. If you want high SPL all the way down to the limits of audibility (defined as 20 Hz for humans), use a big subwoofer, i.e., 15" or 18", such as I have done here. With smaller subs, you will only be able to EQ down to 30 Hz or so, depending on the quality of the subwoofer and the power of its amplifier.

One Last Thing

In the original SMS-1 review, the amount of THD+N was not measured. In keeping with our procedures of doing bench tests, I wanted to add the distortion measurements for the SMS-1.

First, the sound card loop through (output connected to input), using a 40 Hz sine wave (shown below). THD+N is less than 0.002%.

With the SMS-1 in the signal path, THD+N increases to a little more than 0.05%, which is acceptable.

Perhaps most consumers who purchase the SMS-1 may want to go ahead with connecting a TV and fine tune the EQ. But, the point of this article is that you can get a significantly improved bass by just activating the Self EQ. It really does perform nicely.


My little experiment was a great success. The use of the two SMS-1 outboard EQ units made so much difference in my bass listening pleasure, I will never be without this capability again.

The Self EQ worked very well, without having to connect a TV and manually adjust any parametric EQ bands.

Whether you get the SMS-1, or a Velodyne DD series subwoofer which has the SMS-1 circuitry built-in, or one of the other outboard subwoofer EQ systems out there, you will undoubtedly never want to be without it again either.


- John E. Johnson, Jr. -

Copyright 2006 Secrets of Home Theater & High Fidelity

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