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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
jaytor's avatar
jaytor OP
765 posts
 

I spent a while researching the Trinnov Nova, but decided to go with the Danville dspNexus. 

The Nova would have cost $5500 ($3500 + two additional 2-channel licenses at $1000 each) compared to $3000 for the dspNexus. But even at the same cost, the Nova is really designed as a pro-audio studio calibration system and is not as well suited for my purposes. For example, it does not have an IR remote, and it doesn't have an easy way to control the output volume. The user interface is fairly slick, but is designed to be fairly automated and doesn't appear to have the programming flexibility of the Audio Weaver software used by the Danville.

The dspNexus has both a stepped attenuator (in 3db steps) to set the max output level, and digital based volume control that can be controlled by an included IR remote. It is very modular allowing the DSP and DACs to be easily upgraded. Al Clark indicated that they are working on upgrades for both, and a new (significantly more powerful) DSP board will be provided for free later this year. 

Also, the dspNexus will ship on Monday, while the Trinnov is currently backordered. 

ricevs
1,543 posts
 

Minidsp Flex's are way better than you think.  You can use two 4 channel out ones ($500 each) in parallel and get 8 analog channels out with both digital and analog inputs.....I  read that these newer units are using Burr Brown PCM1795 DAC chips....not confirmed.  These units run at 32 bit 96K unless you are using the option Dirac thang which operates at 48k.  The new Flex units run at higher bits and have better distortion, etc. than most of the older stuff.  Built in digital volume control and remote with several presets.  Here are some measurements:

https://www.audiosciencereview.com/forum/index.php?threads/minidsp-flex-review-audio-dsp.30804/

lewinskih01
909 posts
 

@jaytor 

Great system, and sorry I'm arriving 2 weeks late!

I also do DIY, dipole, AMT tweeter driven by SET, although have 4 sealed DIY Rythmik subs. And use DSP for digital xo and room correction. I use Acourate software for this, and believe Audiolense is also great. A great write-up by Mitch Barnett can be found at Computeraudiophile from years ago - there is a basic walk-through and an active xo walk-through, where he explains the setup and process, and results. He late wrote an ebook, and did an article on Audiolense I think.

My setup is an "audiophile" computer running Roon, convolving filters made with Acourate that account for linear phase xo and digital room correction (and time-alignment, etc), that outputs to a 8 channel DAC (Lynx Hilo) thru USB, that drives 8 amps directly connected to the drivers. Hilo has DAC and ADC capability, which is important to take the measurements to create the filters to be convolved. This is sort of the DIY approach to what boxes like DEQX do. One ADC/DAC I've had my eye on is Merging Hapi, but haven't gone there yet.

As I started venturing into active xo, I first used the Rythmik xo to relief my tube amp from reproducing sub frequencies. This was good, but going active with Hilo/Acourate far surpassed this solution. To me there is no going back. Given your DIY skills and willingness to dedicate time to get it done, I suspect you'll be on a similar path.

Please keep us posted on your journey!

jwr159
28 posts
 

Finally got my act together.
 

Since purchasing the DSP Nexus back in June, 2023, I was only bi-amping while still running the audio signal through the passive xover in my speakers for the mid range and tweeter. I recently purchased a third amp and modified my Eminent Tech 8bs to bypass the passive xovers altogether. For subs, I’m using a pair of dipoles. I do not use the 8b subs at all, definitely the weak link with these speakers.

Just today I got the system up and running. First impression is I’m amazed. This is the future of audio. The DSP Nexus in combination with the 8bs and high quality subs is pretty darn stunning.

jaytor's avatar
jaytor OP
765 posts
 

@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?

 

 

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