Re: Coaxial Wedge Collaboration
Hello Michael, whenever you have a moment, I'm curious to hear how this plate amp'd version turned out for you? I hope to build one of these in a few months (have the BMS already) and given a choice, I'd rather my first attempt be a powered version. Thanks much for the design work and all info!
Hi Scott,
The D-Cell504-IS plate amp is a really nice, compact solution but it has one annoyance. (More details later below.)
I'm using the D-Cell504-IS 4ch - 1 ch for the HF and 2 (bridged) for the LF. Each D-Cell504 module is stereo and so the IS 4ch plate has two modules - one w DSP and one without - plus one, shared, power supply.
It can be programmed via Armonia (through a Pronet485 adapter) or with SigmaStudio (through a programming dev board). I opted for latter since SigmaStudio is more flexible, but once the board is connected to SigmaStudio, it's boot firmware is changed such that it can't talk to Armonia. (The Powersoft guys said that reflashing for Armonia is not impossible but does require more tools.) Powersoft provide nice, pre-made SigmaStudio signal flow templates for a number of different configurations.
I found it useful in SigmaStudio to put mute blocks on each output whilst tuning. Without mutes, many parameter changes to DSP blocks cause loud bangs. (One time I thought I'd killed the HF.) I have a large cap in series with the HF anyway.
The limiters in SigmaStudio are ok but are maybe a little rough. (I've designed my own peak and RMS but haven't integrated them yet.)
Now to the annoyance. The DSP is an Analog Devices ADAU1702 SOC with integrated 2 channels of A/D and 4 channels of D/A. The converters are noisy. In SigmaStudio, summing the stereo inputs gives about a 3 dB improvement in SNR but the overall noise is still at least 6 dB too high for my liking and is very audible in a stage wedge. I've tried padding the HF with a series resistor but it's a balance between noise and loosing headroom. For me it's noisy enough that I haven't made any more active wedges and I haven't yet found any other all-in-one compact DSP plate amp solutions. It's a little noisier than commercial active speakers I've listen too. (Maybe I'm too picky). In every other aspect it is a perfect solution.
