Outline (nothing of substance to see here yet)
Intro
The active line array project described in these pages is the culmination of many years of part-time line array development, starting with the array described in this article: “Case study #3: A line array with DSP“. That early design has proven to be an excellent music and TV speaker. However, that design was started over 11 years ago, and it is now ready for a technology facelift. The links on this page provide the details of the new circuitry and software that will go into the refreshed line array.
I have tried to include enough details of the design to allow others to make their own active line arrays. That means providing the PCB project files, schematics, Sigma Studio code, Arduino code and Android Studio files needed to control the hardware from a cell phone. All of this material will be made available in the pages linked from this top-level outline. There are no restrictions on its use other than you must understand that much of this design was done quickly and in many cases is in need of refinement, editing, refactoring and other improvements. You will be looking at an experimenter’s notebook, not a proven commercial product. Also, please understand that the information is presented “as-is” and that I have limited time to respond to questions.
Rationale
why active line arrays are good. DSP with lots of amps make constant directivity possible. DSP also makes open baffle much easier.
Design overview
goals, block diagrams
Electronics
— Amps
The amplifiers for the midrange and tweeters in a line array do not require much power, and there are quite a few single-chip solutions that can be used for the active line array, but a standout solution is the SSM3582. This page explains why this chip is especially well suited for this application and it details the PCB design and construction of a modular 4-channel board that is a little over 2 square inches. This page also includes the C++ code you will need to initialize these boards.
— Motherboard
— DSP
With at least 20 channels of audio that need to be updated every audio sample, we need a capable digital signal processor (DSP). This page provides an overview of the DSP processing for the active line array and documents the design and construction of one of the DSP boards. The actual DSP “program” that runs on the DSP is detailed in a later section, under “Software”.
— MCU
Hmmm…a fair question is: do I really need or want a computer in my speakers? The answer is no, you don’t need it, but you will probably want it. This page explains what the microcontroller does in the active line array, and why it is more useful than you might expect.
— Power Supply
Software
DSP, Arduino, User interface