d&b DSP and amplifier plan

To wrap up this mini-series on the new d&b rig (if you missed any posts, be sure to go back through the past three for more info on what is going on), today’s post will focus on DSP & amplifiers.

On our old KF650 rig, DSP was extremely important.  We used a BSS London BLU-80 to provide an insane amount of processing to the entire rig, essentially trying to polish it to a point of usability.

When we decided on going with d&b, a significant bonus to the system is the awesome amplifiers with built-in DSP for system processing.  While some manufacturers lock down almost all system settings making it too difficult to customize the rig to the room, d&b has done a great job of creating a system with what I believe to be just the right amount of control to tune the room.  Because of this, my goal was to have as little DSP as necessary to make the rig sound good.

Our signal chain now is a left/right feed from the console that hits the first system amplifier, then simply loops through to each of the other amps.  The system is run full range from the console rather than aux fed subs so that the phase and spectral response of the PA as a whole will remain consistent from service to service and engineer to engineer.

Each amplifier channel has a 4 band fully parametric EQ & signal delay.  The coolest part of the DSP, though, is a few other settings available that provide subtle ways to sculpt the rig artistically for different responses depending on what’s desired.

• The CPL (Coupling) circuit compensates for coupling effects between the cabinets. These effects increase as the length of the line array is extended. CPL begins gradually at 1 kHz, with the maximum attenuation below 400 Hz, providing a balanced frequency response when T10 cabinets are used in arrays of four or more.  The function of the CPL circuit in these amplifiers can be set in dB attenuation values between –9 and 0, or a positive CPL value which creates an adjustable low frequency boost around 65 Hz (0 to +5 dB).
• The HFC (High Frequency Compensation) circuit compensates for loss of high frequency energy due to absorption in air when loudspeakers are used to cover far field listening positions. It’s almost like an “air” control that gives a few options for how open the high end responds.

The D6 and D12 amplifiers have three configurations for T10 cabinets, Line, Arc and PS (point source). The Line or Arc configurations are selected when the T10 loudspeaker is used as a line array. The chosen configuration will depend on the curvature of the array. The Line configuration is selected when groups of four or more T10 cabinets are coupled in a straight long throw array section, where the splay angles to adjacent cabinets are 0° to 2°.  The Arc configuration is selected when T10 cabinets are used in curved array sections, where the splay angles to adjacent cabinets are 3° or more. Within a typical array both amplifier configurations are used. The PS configuration is selected when the T10 is used as a single spherical loudspeaker.

Wrapping up this section on DSP and amplifier control, I’m very impressed by the R1 software included with the amplifiers to provide remote control from FOH of the entire rig.  Tuning functions such as EQ, delay, HFC, and CPL are all included, but the coolest function to me is a page we set up that shows the input level into the amps, the output level the amps are actually sending so you can visually see your system headroom, actual ohm loads on the amps, actual RMS output wattage, power supply voltage, gain reduction, and temperature warnings.  The software is completely customizable so you can set up pages to show exactly what you want, how you would best like the information.  Great stuff!

d&b subwoofer placement

Continuing this mini-series on our new PA at Kensington Troy, today we’re going to talk about subwoofers.  This post might be a bit premature since we have not settled on the final quantity and location of the B2 subwoofers that provide the bottom end of the rig.

I must say, these subs have always been some of my favorite.  They are very very tight and punchy, with what feels like headroom for days.  Some subwoofers start to break up when pushed and “feel” like they’re being pushed.  These B2s can run right up to the brink and actually sound better as they’re doing it.  The result is a rig that feels like it has no limits!  Pretty awesome to mix on, I must say!  :)

From the ArrayCalc software, here is the predicted pattern of our initial configuration – 2 subs equally spaced on the stage deck approximately 40 feet apart.

This looks a little nastier on paper then it actually feels in context, but there is definitely some slight banding of the low end in this configuration.  Another option that I think I want to try is 3 subs in a cardiod configuration flown over the center downstage position where our old center cluster used to live.  Here’s its predicted response…

As you can see, there’s a big difference in how these two configurations will perform in the room.  The jury is still out on which direction we will go.  I’m hoping to try this soon with the boxes on the stage deck before we commit to the air and see how it translates compared to the equally spaced approach.

d&b T10/TSub array configuration

Those of you who are system geeks like me will probably dig this post.  I’m going to outline the configuration of our system and how we designed it using the d&b ArrayCalc software available for free download at their website.

As you can see, our main arrays are each comprised of 6 T10 main speakers and 2 TSub subwoofer cabinets.  The T10 is made up of two 6.5″ drivers and a 1.4″ hi-frequency compression driver.  The TSub is a single 15″ high excursion driver.

This first output from ArrayCalc simulates the aiming, coverage, and SPL throughout the main floor of our room.  In the Top View, the white line shows the center throw point of each array.  The dotted yellow line shows the coverage pattern at the top of the array while the orange line shows coverage at the bottom of the array given the rake of the boxes.  Listening to the actual space with the boxes installed, as expected, the only shaded listening positions is the 5 or 7 seats in the extreme front corners of the room and the very last row under a slight balcony overhang.

The next drawing is Main L/R Profile at 10 degree aiming.  This shows how the center point of each box’s coverage and how that will translate to the seating area.

Finally, the Direct sound level vs. distance shows how the rig should respond in the space and what SPL fall off to expect from front to back.  As you can see, this prediction was probably my only slight concern since there’s as much as a 12 dB difference from the front to back of the room.  We expected to need to do some gain shading of the boxes in the array from bottom to top in order to smooth out this difference a bit.  However, in actuality, we found the difference to be far more understated then expected.  As I noted with my general observations in Friday’s post, everyone was blown away by how consistent the spectral balance and perceived SPL remains throughout the entire seating space.  It really does translate smoothly from FOH to both the front and back of the room.

Next time we’ll talk about subwoofer arrangement and performance.