Velodyne DD-18 Set-up
The calibrated mic\real-time response plot display is a combination superbly suited to getting the DD-18 properly set up. In addition to the benefits already mentioned, the real-time display can make quick work of locating suitable positions for the sub: simply place the sub at your main listening position, set the DD-18 to generating its test tone sweeps (Sine wave, 15 Hz to 200 Hz, with tracking bandpass filter) and walk around the room with the mic in hand and watch the effect your position has on the response displayed. No more crawling for bass! Eventually a few spots within your listening space suitable for your sub (acoustically speaking) will emerge.
Once these are identified, move the sub to whichever of the spots it is practical to do so and run the EQ process. To make it easy to compare before/after PEQ for each spot I fed the video stream to a PC and put together a collection of screen captures. Snapping pictures with a digital camera and looking over the results afterward would work just as well.
Running the EQ
process is pretty easy to do. In general form, here are the steps:
1. Make certain both sub and AVR are off.
2. Connect the mic to the DD-18 (jacks are provided on both front & back panels).
3. Connect the sub’s EQ Out to an appropriate input on your AVR.
4. Turn on AVR & Sub, turn down gain on each to mute output
5. Set sweeps running and increase gain on AVR to a
comfortable level, then increase subs
gain until the two response plots appear roughly equivalent in terms of
amplitude magnitude. Set crossovers, slopes, phase and polarity,
primarily to get the crossover point with the mains right, then go to PEQ (step 6).Proceeding in this way allows for a minimum of PEQ required to tune the sub.
6. Set Equalization mode to Automatic and let the DD-18 calculate a solution. It’s fascinating to watch the display as the system homes in on a solution.
7. Once the auto process has run to completion, manually tweak the PEQ settings (if so desired) and save. Note: When tweaking system settings (Fig. 11), use the Test key to jump back and forth to the system response screen and see the results of the latest efforts. When all is maximally tweaked, save.
If your processor/receiver is running bass management, defeating the DD 18s internal crossover is a common practice. This can be done when you’re in the System Settings screen by setting the low pass crossover slope & frequency to “OFF”. (See Figure 11).
The manual provided with the DD-18 (available online as well) provides, of course, far more detailed instructions and comes highly recommended. I suggest reading through it a few times before running the process.
The third and final screen in the series presented by the DD-18 is the Presets screen, seen in Figure 11.
Figure 11: DD-18 Presets Screen
The DD-18 comes from the factory with its 6 presets preset. (One of the six functions as an EQ defeat)
On the remote they’re labeled:
5. Custom (yours to tweak as you see fit to do)
6. EQ Defeat (especially useful for before/after comparisons with Preset 5)
Referring to Figure 11, from the top down the function/parameter fields are:
- Lowpass Crossover Frequency: adjust the upper limits of the subs response
in terms of frequency (15 Hz to 199 Hz, increments of 1 Hz)
- Lowpass Crossover Slope: adjust the upper limits of the sub’s response
in terms of slope (6 dB to 48 dB/Octave in 6 dB/Octave increments).
- Subsonic Filter Frequency: Set the sub’s LF limit in terms of frequency (15 Hz – 35Hz, 1 Hz increments)
- Subsonic Filter Slope: Set the sub’s LF limit in terms of filter slope (6 dB – 48 dB/Octave, 6 dB increments)
- Phase: Set sub’s output signal phase (0° to 180°, 15° increments)
- Polarity: Set subs polarity (toggle between “+” and “-“, equivalent to a 180° phase reversal
- Volume: Set individual preset volume (gain) separate from that of system master gain control.
- Contour Frequency: Sets contour boost/cut frequency of Contour EQ
- Contour Level: Amount of boost/cut at contour frequency of Contour EQ
- Theater/Music: Set the amount of distortion-limiting servo gain; 1 (Theater, min. servo gain)
8 (Music, max servo gain, minimum distortion).
- Default Preset: Select the sub’s default preset; the preset the sub automatically runs at startup.
- Auto On/Off Mode: On at signal sense, off 15 minutes after the last detected signal.
(L & R In sum to mono, in effect, increasing sensitivity to the incoming signal by the auto on/off process, making it more effective at detecting low-level signals).
- Night Mode Volume: Preset max. gain level.
- Light: Sets the logo light on or off. Default is on.
So how well did the PEQ work?
Pretty well, actually. Figures 12, 13, and 14 tell the story.
Figure12 is the pre-AutoPEQ picture, Figure 13, post-AutoPEQ and Figure 14, post-AutoPEQ followed
by a modest amount of manual tweaking. Subjectively speaking, the audible difference between the system response as seen in Figure 12 & 14 was truly substantial; best described as the lowest few octaves of the system pulled into focus, delivering an increase in precision and clarity that would have to be heard to be believed. Excellent!
There are a couple things that should be kept mind when viewing the figures. First, the plots generated by the Velodyne display are 1/3rd Octave smoothed. Second, the amplitude response generated is for the main listening position only; move away from that position and the response will change both audibly & measureably.
Figure 12: System response, pre- AutoPEQ, as measured at the main listening position 9’ (2.7m) directly in front of sub.
Figure 13: System response, post- Auto PEQ, as measured at the main listening position 9’ (2.7m) directly in front of sub.
Figure 14: System response, post- Auto PEQ, with additional manual tweaking, as measured at the main listening position 9’ (2.7m) directly in front of sub.