Subwoofers

Velodyne DD-18+ Subwoofer

ARTICLE INDEX

The Design

The first thing one will notice in looking at the DD-18+ is its shape. Instead of the usual square box, the sides are curved. This reduces internal standing waves.

Although you can manage the functions of the subwoofer via the included remote control, there are also some controls at the top of the front, underneath the grille. The photo below shows the controls, and from left to right, they include a mini-USB jack for connecting to your computer to run the EQ software, a microphone jack, the IR port for remote control signals, a volume control and crossover frequency selection control, and an Auto EQ button. The volume control and crossover frequency control are continuous rather than potentiometers, and the values are displayed on the LCD window in the center. If you want to adjust the volume using the control knob instead of the remote control, use your fingers to pull the top of the grille away from the subwoofer so that you can reach in and turn the control. Then push the grille back into place.

velodyne-dd-18-plus-subwoofer-control-panel-front

It's getting so that the connections on the back of subwoofers are almost as complex as the backside of receivers. The DD-18+ (and the other subs in the DD+ series, which include a 10, 12, and 15) has an Ethernet port, S-Video jack (for use instead of a computer), RS-232 input, RS-232 Output, Left and Right XLR line-level inputs, XLR Thru Outputs (for daisy-chaining subwoofers - no high-pass or low-pass has been applied to the signal), and XLR high-pass line-level outputs. On the right side there is a composite video output (again, for use if you don't want to use a computer for bass management), IR input, Trigger jack, Line-Level volume control (RCA inputs only), left and right channel RCA Thru, Line-Level Outputs (high-passed), RCA Line-Level Inputs, High-Pass frequency selector (100 Hz or 80 Hz) and Speaker-Level volume control. At the bottom are the on/off toggle and non-grounded AC receptacle.

velodyne-dd-18-plus-subwoofer-rear-panel

The driver in the + series has a much longer excursion than previous models (Xmax - 1.3" peak-to-peak). It uses a fiberglass-Rochacell laminate cone and has a 40 pound magnet. The cone has a hand-made accelerometer mounted near the voice coil and acts as a servo-feedback mechanism to the input of the amplifier. The difference between what the amplifier is sending to the driver and the actual driver motion is inverted and fed back into the amplifier circuit, which cancels some of the distortion that the driver is producing. However, the real key to low distortion is through careful design of the driver itself, and Velodyne has done this (they have been doing it for decades).

Many subwoofers now have built-in EQ capabilities, either one or two manual dials on the rear panel, push buttons on the remote control that activate preset EQ's for various music and movie situations, or software. The Velodyne DD-18+ comes with a software program that runs on Windows. Initially, make sure the subwoofer is connected to the sub-out on your receiver and is powered on (toggle on rear panel). Install the software on your computer. Then, after removing the sub's grille, you connect the included USB cable from your computer to the mini-USB port on the front of the subwoofer (you will likely need your laptop for this, as the cable is short). Next you connect the included microphone to the Mic input jack on the front panel and place the mic in your listening position with the included small stand.

The last item you need is the included CD which has test tone sweeps in the low frequencies. Place this in your CD player or Blu-ray player and turn on your receiver. Boot the software program, and then start playing the test tone CD. You will hear low frequency sweeps that last about 1 second. The sweeps repeat one after another so you have plenty of time to work with the software to EQ your room. You can also press the Auto EQ button on the front panel of the sub, and the software will go through a series of adjustments to EQ your room as best as it can. My room proved to be very difficult for the Auto EQ, so I performed the task manually (it was a lot more fun EQ'ing it manually, anyway).

The steps I took are shown below (as usual, click on the photo to see a full sized version that is more legible).

Up in the right hand corner, I selected 4-Custom as the preset that I wanted to EQ (rather than change the other presets that already have EQ applied to them). The CD was playing, and I clicked Start in the bottom right. There was an indicator that said the sub was "synced"). The room response, without any EQ applied, appeared in the upper graph.

Then, I began applying EQ by adjusting the level and the Q (width) of the eight EQ bands. You simply use the left mouse key to drag the little quadrangles next to the numbers 1 - 8 upward, downward, or sideways (sideways changes the frequency where you are making the adjustment). The Q is the width of the EQ that you are making at any one frequency. In other words, with a low Q, the width around the 20 Hz marker will be very wide, so it will affect frequencies farther away from 20 Hz as well as 20 Hz itself. You can narrow this effect by increasing the Q in the box down at the bottom of the screen.

The beauty of this software is that, as you adjust the EQ bands, the CD is still playing, and you will see the effects of your latest EQ adjustment in live time. Now, you will find that it is not as simple as just adjusting the level at a frequency where there is a dip or a peak. You may have to move the EQ button to the left or right of the frequency you want to adjust. Using the Q has large effects as well. It will take you some time to get used to what the EQ buttons do when moving them and changing the Q, but in the end, you can have a room response as shown below.

When you have the EQ curve that you want, you can stop playing the CD, and the software will say "Not Synced" at the bottom right corner. I clicked the "Save to DD+" button in the bottom right, and it was done. You can also "Save to File" so that you have a backup of the Custom EQ settings. To open the file, go to File, Open, and click on your saved file (be sure to name it so you won't confuse it with other saved EQ files). I adjusted the crossover in my receiver, which has its own bass management options, to 60 Hz so that it blends with the response I obtained in the EQ software for the Custom preset.

If you have saved it to the DD+, and you change your mind and want to start over with a flat EQ, hit the "Reset" button, and the EQ will go back to being a flat line, shown below. Then Save to DD+. That will put a flat EQ back into the subwoofer and you can start over with a fresh EQ screen.

My suggestion, after initially EQ'ing your subwoofer, is to sit back and enjoy some music and movies because there is more to come.

. . . . OK, so you have listened to music and watched that Britney Spears movie and are ready to go a bit further.

Boot the software, open your saved EQ file, click the "Next" button at the top right. That will take you to this screen:

Here, you can adjust the turn-on Volume, Low-Pass Crossover Frequency, Low-Pass Crossover Slope, Sub-Sonic Frequency (below which the sub will not respond), Sub-Sonic Slope, Phase, Polarity (inverting or non-inverting), Contour Frequency (a frequency where you want a little extra bump, which is useful in some of the presets, such as Rock, where the contour frequency is set at 52 Hz and the level is set at 2), Theater/Music (this is the amount of servo-feedback that is applied, with 1 being the least amount, which allows the most distortion and is preferred by many users when playing games, or perhaps a dynamic action move, and 8, which is the most amount of servo-feedback and results in the least amount of distortion, preferable for music, Auto-On, and Night Mode (compresses the dynamic range so that the sound does not get too loud, waking the neighbors, or too low volume to hear what is being said).

You should try out some of these features on the secondary screen to see what effect they have on your sound system, particularly, the low-pass crossover frequency, low-pass crossover slope, the polarity, and the phase. You can save various combinations as EQ files, loading them when you wish.

The factory default preset when you first turn on the subwoofer is Preset 3 – Jazz. If the preset is changed and the new settings are saved, when it turns on, it will go to the preset that was last saved to memory. If you change to Preset 2 and save it, then turn it off and back on, it will be in Preset 2. If you change the preset and turn it off and on without saving first, it goes to the last saved preset.

When the PC software is first loaded and connected, all of the settings on the main screen correspond to the Setup preset. This is the universal preset and settings that change in Setup, cause changes in all the other presets. If you turn the Volume up by 1 in Setup, all of the other presets' volumes go up by 1. Auto EQ makes changes to the Setup preset.

The differences between the presets are in the Contour Frequency and the level for that frequency, and in the Theater/Music setting (the amount of servo-feedback).

The remote control is smaller than their previous remotes, but is well designed with tactile buttons. You can control all the features of the DD-18+, including setup, EQ optimization, and selecting presets. You can also turn the front panel display on so that it is constantly illuminated. Clicking the Defeat button turns off all the EQ in the preset that you are using. This lets you hear what the differences are with and without EQ applied. Click the Defeat button again to turn the preset EQ back on.