There are many DSP products on the market today that promise to make the installed sound designer, the installer, and end user’s life easier. You know the drill: more tricks in the box for less. But you also know that most of the time, you will surely get a steep learning curve and unknown configuration caveats just waiting for that obscure application to say “gotcha.” In this review, we’ll look at the latest series of DSPs from Lectrosonics — the DM Series Digital Audio Processors. The series offers five configurations: the DM1624, the DM812, the DM84, the DMTH4 Telephone Hybrid and the unit under scrutiny in this review, the DM1612.
Suggested applications for this device are sound reinforcement and conferencing systems for boardrooms, courtrooms, worship centers, distance learning systems, and so on — basically, any environment that could benefit from an automixer with the additional features of a DSP.
16 x 12 matrix mixing; automixing; delay; low, high, band-pass filters; USB port; LecNet2 software; AMX and Crestron-compatible
Using a cluster of four SHARC DSP chips and 24-bit A/D converters, the DM1612 architecture consists of 16 mic/line inputs and 12 outputs with a DSP-based crosspoint matrix that allows every input to be routed to any or all outputs. After the A/D conversion of each input, the signal passes through multiple EQs, an automatic digital feedback eliminator, a compressor, and a digital delay. In the matrix core, gain is adjustable from –69 dB to +20 dB in 1 dB steps at each crosspoint. Each of the 12 outputs provides a digital delay, multiple EQs, and a compressor/limiter. The DM Series of products can be linked together using conventional Ethernet cables in a master/slave system configuration.
Housed in a 2RU rack space unit, this unit has a very clean, uncluttered face with a just a few controls. The main interface is the four-line, backlit display flanked by a push for menu select/turn to select knob; two micro switches: one used for turning back in the menu and the other to assist in locking the front panel; and six menu item select buttons to the bottom of the display. There is also a USB interface port and the power switch. The flat black face with white lettering will look nice in most racks.
The back panel of the unit is very neatly laid out as well. Starting to the left is the power cord receptacle, a 1/8-inch RS232 serial port jack, a USB port, programmable I/O ports, Ethernet expansion ports, and the line out and mic/line inputs, which are landed on Phoenix connectors. The unit is compatible with Crestron and AMX control systems, has digital I/O ports to connect to other LecNet2 devices, and comes very neatly packed complete with all connectors, cables, cords, software and manuals.
The input chain is pretty straightforward and contains the basic building blocks one needs to process a signal from mic input to output. Each input channel provides four individual processing stages of gain, delay, filtering and compression. Input gain adjustment is available in a 0 dB – 50 dB range with adjustment in 10 dB steps and a fine adjustment in 1 dB steps. Next, a digital delay of up to 1 second can be applied in .5 ms increments. Following the delay stage is a complement of six different filter sets: low-pass, high-pass, band-pass, parametric, low shelving and high shelving. Additionally, you can select a filter slope with 6 dB or 12 dB per octave Butterworth or Bessel parameters. There are six automatic digital feedback eliminator filters and then a compression stage with adjustment parameters including threshold, attack, release, ratio and makeup gain. The limiter parameters include threshold, attack and release.
In the “Automixer Cell,” level control for the automixing algorithm, mixing mode and crosspoint gain is applied to data gathered from other channels and devices. The cell receives data from the master unit in a multiple unit configuration and from the slave units farther down the chain. The automixer does not use a noise gate but rather a “Proportional Gain Algorithm” for a theoretically smoother response.
I decided to see how the unit sets up from the front panel before loading the software. In turning on the unit, the display greets you with the unit’s model number and software version. There is no scrounging around and looking for that piece of important info. Turning and pressing the selection knob gets you into the next layer of submenus while the small select buttons at the bottom of the screen allows you to select the parameter of choice. Coming to the main menu, your selections are Setup, Presets, Sysinfo (system information), Lockset, Cmdview, Serial port and Exit. From the Setup menu, you can select inputs, matrix outputs and general.
Drilling down into the Input menu, here is where you choose attributes like phantom power, phase inversion, mute, gain, rear panel gain and input channel. It’s probably getting picky, but I thought it would make better sense to have the first parameter be the channel selection, as it is it defaults to phantom power, but the first thing I found myself doing is selecting the channel first. The Matrix menu sets up the crosspoint settings like in and out points, mute, gain and mix mode. Next, the Output menu allows you to select the parameters like mute, source, rear panel gain and output channel.
It is important to point out that none of the DSP functions can be accessed or controlled from the front panel. All DSP control functions are accessed via the LecNet2 application. To do this, first you have to make a connection to the unit via USB or serial port. I chose to go the USB route and, the using the cable supplied with the unit, I made the connection to the front panel, then installed the LecNet2 software and USB drivers onto my laptop. This whole operation took only minutes and was clearly outlined in the accompanying manual. Once the software was loaded, I had to look for it because the installation process did not give me a choice to put a shortcut on the desktop. After locating the “LecNet2” folder, I noticed that control panels for all of the DM series of processors were loaded, and I simply selected the control panel for the DM1612.
When I fired up the application, it loaded up into the “off line” mode. Here, you can see all of the screens and parameters, but no changes will be made to the unit until you “connect” to the unit. Connecting to the unit is done through the “connect” pull down menu, and, once this is done, you are talking to the box with all changes made in real time. I would have liked to see some type of physical confirmation that I am connected to the box — a “connection established” notice or something of the sort.
The control panel is pretty straightforward. Each section of the box has a tab where you make your changes. I especially like the matrix panel, where color-coding makes I/O assignments fast and easy to understand. The tabbed layout makes each input, output and DSP function easy to get to and keep track of. I liked the fact that I didn’t have to keep an eye on a DSP meter to make sure I wasn’t going to run out. I liked the “nailed up” approach, knowing that any function I need is going to be available at any time without a compromise in quality or function.
Connecting sources to the unit via the Phoenix connectors was quick and easy. Using a mix of dynamic and condenser mic sources and audio from a video source, I used the matrix mixer and automix function to set up some scenarios. Making changes with LecNet2-based control panel, I proceeded to put the rest of the modules through their paces. Delay — which can be set in time, feet or meters — was easy to navigate and the change in the parameters of the effect was responsive. I would have liked to see a bypass switch so that signal can be compared with or without the delay setting. Having a built-in output source of a 1 kHz tone and pink noise is a nice touch for setting levels and testing connections. Using the macro editor for setting up identical channel parameters can be very useful and was easy to enable, record and apply. Another nice little feature is the ability to label the inputs and outputs. I noticed a slight delay in the response for the compressor and limiter meters, but the operation of the process was good. Overall, moving through the different processes was easy and was met with good results. The unit is clean, responsive to transients, and audio quality is good.
The Lectrosonics DM1612 has great sound quality, while an easy user interface and feature set make it a great choice for the intended applications. Our technicians have always grumbled about the complexity and learning curve of DSP boxes. This unit is easy to understand, program and manipulate. Additionally, as with the other DSPs in this series, using this box won’t back you into a corner when it is time for expansion.