The weird speaker in the picture below is an updated version of an active 5-way speaker I built about 15 years ago. I wasn't happy with the DSP/amplifiers in the original design, so I stuffed them in a closet until I could finish off new electronics.
Each octagonal "tier" has 8 drivers, and I had wired them so that I could reverse the polarity of the drivers in the back. The original design used relays to reverse the polarity, but in this updated version the polarity is controlled by processing in an ADAU1466 DSP. This approach requires 10 power amps for each speaker, with one amp for the front and one for the back. The DSP processing for the dipole switching/compensation is shown in the SigmaStudio snippet below. Each of the rear drivers has a signal inverter plus a biquad for a shelf filter, plus a gain block to adjust the volume.
I only have one speaker running right now, but I'll get the second one working as soon as we finish refurbishing our upstairs bedroom. I've only got this one speaker running in a small workroom, and there is still a lot of work to adjust the delays and experiment with different crossovers. However, the difference between dipole and monopole mode is fascinating.
I know...the lights are kind of weird, especially when they are flashing to the music 🙂
Each octagonal "tier" has 8 drivers, and I had wired them so that I could reverse the polarity of the drivers in the back. The original design used relays to reverse the polarity, but in this updated version the polarity is controlled by processing in an ADAU1466 DSP. This approach requires 10 power amps for each speaker, with one amp for the front and one for the back. The DSP processing for the dipole switching/compensation is shown in the SigmaStudio snippet below. Each of the rear drivers has a signal inverter plus a biquad for a shelf filter, plus a gain block to adjust the volume.
I only have one speaker running right now, but I'll get the second one working as soon as we finish refurbishing our upstairs bedroom. I've only got this one speaker running in a small workroom, and there is still a lot of work to adjust the delays and experiment with different crossovers. However, the difference between dipole and monopole mode is fascinating.
I know...the lights are kind of weird, especially when they are flashing to the music 🙂
Some more "digital line level" details:
The hardware details are at: http://www.audiodevelopers.com/return-of-the-marthas/
These speakers will allow me to compare omnidirectional "ring arrays" to the same drivers in "dipole mode". Also, I will be able to compare different crossover configurations with instantaneous switching. This is going to be fun, and I'm getting blown away by how good this first speaker sounds.
- The only source is a Wiim Mini music streamer that is buried inside
- The DSP is controlled by an ESP32C3 that provides a Bluetooth interface
- The "Dipole Mode" can be selected by a switch on a cell phone app
- There is a 10-band overall EQ
- Each set of drivers has digital delay and volume controls and a programmable "custom biquad"
- The crossovers can be any topology up to 10 poles
- The speaker can be configured as a 3-way, 4-way, or 5-way system
- Custom settings can be saved and recalled with a single command from the Bluetooth interface
- The SigmaStudio program is shown below
The hardware details are at: http://www.audiodevelopers.com/return-of-the-marthas/
These speakers will allow me to compare omnidirectional "ring arrays" to the same drivers in "dipole mode". Also, I will be able to compare different crossover configurations with instantaneous switching. This is going to be fun, and I'm getting blown away by how good this first speaker sounds.
Nah, they stole my design 🙂. These cabinets were made in 2006 or so.
Ring array configurations were used in many of Roger Russell's McIntosh designs going back much earlier, so that concept isn't new. And, of course, there is nothing new about using reflected sound and dipole radiation. What's really new in these upgraded speakers is the ADAU1466 DSP and the ability to switch operating modes conveniently from a cell phone app. That's why this I started this thread in the Digital Line Level forum--at this point in the design it is largely a software project to control the DSP.
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