DSP Active Crossover


I'm considering trying a DSP-based active crossover in my system. I did a search to see how much this has been discussed, and most of the posts are pretty old or about active speakers. DSP technology has changed a fair amount in the last 15-20 years.

My system is digital only, and my speakers are 3-way, so it's not particularly complicated. I've been looking at the Danville Signal dspNexux 2/8 which has two channel in (with digital inputs) and eight balanced analog outputs. This appears to be available with AKM AK4499 DACs which are fairly well regarded sigma-delta DACs (although I don't know how good their implementation is).

This product has a fairly rich DSP software environment for programming filters, time delays, etc., so it should be fairly straightforward to set it up to replace my passive crossovers. 

My biggest reservations are 1) giving up my Denafrips Terminator+ DAC and nice-quality DIY preamp, and 2) using the DAC's digital volume adjustments. 

This unit is about $3K (maybe a bit more with the AK4499 DACs), so isn't terribly expensive. From the limited research I've done, this unit appears to be higher sound quality than the miniDSP or DEQX boxes, but I could be wrong. All my amps have balanced inputs, so I'd prefer to use a unit with balanced outputs. 

So, what I'm wondering is if the benefits of active crossovers and dsp equalization will outweigh the lesser DAC quality (assuming this is the case) and lack of analog volume control (currently using a relay switched attenuator). I'm also wondering if there are other dsp audio processors that I should consider (digital inputs, at least six channels out, ideally with balanced outputs).

128x128jaytor

@lewinskih01 

I received the dspNexus a few days ago, but I've been buried with work so haven't had a chance to do anything with it yet. I've got a measurement mic on order that should be here early next week. I'm hoping to find some time in the next several days to at least hook it up to a computer and download the Audio Weaver software.

Thanks for the info. I found Mitch Barnett's book on Amazon. I'll check it out. I'll also take a look at the Acourate software to see if this will work with my dspNexus. 

@jwr159 

What software did you use to create the filters for your dspNexus? Anything other than Audio Weaver?

 

 

For my  filers, I spoke to Bruce Thigpen at Eminent and pretty much copied what he suggested. For his next gen speakers, he is using DSP, so is aware of what works best. Yes Audio Weaver is what was used to implement the filters. I’m not aware of any other option that is compatible with the DSP Nexus.

Please keep us updated . I’m especially interested in the learning curve, flexibility, and functionality of Audio Weaver.

I have had good luck with a DBX Drive Rack PA 2....am considering upgrading to the DBX VENUS 360....both reasonably inexpensive . Excellent software and Smart App to control all functions from your Smartphone.

The system is a Tri Amped Horn system.....

 

I've made some progress with the dspNexus. This product is still considered an "early adopter" release. The main limitation is documentation. But I've had a couple of video conferences with Emilson, Danville's software engineer, and now have a pretty good feel for how most stuff works. 

I bought a cheap active speaker to use for testing so that I didn't risk damaging my main speakers while I learned how it all works. This has allowed me to verify that the filters are doing what I want. 

Danville provided a sample 3-way crossover design which I have modified to meet my needs, although I'm sure I'll make a lot more changes before finalizing my design. I'm starting out with the crossover points set at 180Hz and 1800Hz, using 8th order (48db/octave) filters. These are the approximate crossover points that my passive crossovers provide, although with much more shallow slopes. 

The Audio Weaver software is very flexible and powerful, but requires that the user set all the filter parameters. In other words, you can't just hook up a measurement mic and have the software automatically determine all the filter parameters to match a target curve. There is a lot more trial and error, but at the same time, you know exactly what processing is being done. 

I have to make some speaker patch cables to connect between my speaker drivers and amps (bypassing the passive crossover), and then I can start testing on my main speakers. I'm hoping to do this over the weekend. 

So far, I have no regrets going for the dspNexus. It seems like a well-engineered and powerful device.