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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
bdp24's avatar
bdp24
9,458 posts
 

@jaytor: Give Danny Richie a call. He’s been involved in some serious investigations into high transparency DSP projects and products. He found the sound of the digital crossover in the Linkwitz LX521 loudspeaker seriously lacking, but there are much better digital systems than the ones Linkwitz used.

Say, I see you now have a pair of 2-woofer H-frames on each side, replacing your precious pair of 3-woofer frames (one per side). Do you have a Rythmik plate amp for each 2-woofer H-frame, for a total of 4 plate amps?

I made the 2-woofer version of the OB Subs, and bought the 8 ohm version of the woofers from Danny, rather than the 16 ohm. That allows the plate amp to feed the woofers their maximum possible output. Being solid state, the amp producers more power into 4 ohms than into 8, of course. And two of the 8 ohm woofers present an approximately 4 ohm load to the amp, while a pair of the 16 ohm an 8 ohm load.

jaytor's avatar
jaytor OP
742 posts
 

@bdp24 - I don’t think Danny is a fan of active crossovers, but partly because a lot of his excellent skills in passive crossover design. But Richard Hollis from Hollis Audio Labs has had some good success (according to others) using DSP crossovers and a system very similar to mine. 
 

I’m using the Rythmik HX800 amps for my woofer towers. Each of the amps has two outputs, each of which drive a pair of 16 ohm speakers in parallel. With this load, they’re rated at 400w for each of the two outputs. 

bdp24's avatar
bdp24
9,458 posts
 

Ah, I see. I haven't kept up with new models from Rythmik. A pair of HX800's makes a lot more sense than four A370's!

jwr159
19 posts
 

Why talk to Danny Ritchie or anyone else. Just call Al Clark at Danville. Interesting guy, claims to have design more DSP boards than anyone on the planet, but has an analog background as well. And Al is generous with his time as well. I purchased the Nexus DSP and love it.  I’ve never tried the miniDSP products, but can’t imagine they are as good. The brand new DEQX boxes are probably 2X or 3X the cost.

erik_squires
15,783 posts
 

My system is digital only, and my speakers are 3-way, so it’s not particularly complicated.

Hard to say how complicated this will be without knowing your system, and what the passive crossover does.

While setting a DSP crossover is as simple as moving sliders around on your screen, entering the right values is more complicated.

A crossover in a passive speaker is almost never "just" high and low pass slopes, but I suppose crossovers for high efficiency speakers are often close to that.

The real question is how well you are able to analyze the current behavior of your speakers and to make the appropriate adjustments.

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