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Passive Crossover bypass – Quest / reQuest

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lifespeed

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I would like to revive this thread to enquire about the digital crossover aspect of bi-amping. While there is some detail to pay attention to when bypassing the passive crossovers, particularly in the Quest z, what have people done with regards to PC-based digital crossover (bass management?) and room correction? I'm guessing two DACs driven by AES/EBU sharing a common clock would be one approach, but I would like to hear the details of what has been done.
 

JonFo

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After a decade-long slumber, the thread awakes !

While I've not directly tried this, other computer audio forums have shown it is possible to do a full bass-manged + 2-way crossover, plus DRC, all on a PC.

I would try Jriver MC (I use MC24 myself, but just for playback) and set up the bass management and crossovers using that. And then for extra-credit, fold in Dirac Live DRC.

You might want to peruse the River forum for more details: https://yabb.jriver.com/interact/

But that gets complex quick, and can be challenging even for geeks.

I love the stability I have with my Marantz AV8802 doing all the (primary) bass management and letting the DBX4800 just do crossovers and time alignment of elements within the same speaker.

BTW- my DriveRack is now 12 years old, runs 24/7, never requires a reboot or anything, it just works.
 

jedi35

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Hi Jon, what a pleasure to see this thread come alive again, and to hear from you!! I'm still regretting my chance to meet you and hear your system when I was touring in the Atlanta area. Honestly, so much audio and video equipment(including 2 Sony 4K 3D TVs) are blocking access to my Monoliths that I haven't heard them in years. I plan to remedy that this summer. It's crazy what I have allowed this to happen. I'm sure that I'll be asking for updated advice on setup, measuring, new settings, etc. once I get around to that.

Adrian
 

heathy

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I would like to revive this thread to enquire about the digital crossover aspect of bi-amping. While there is some detail to pay attention to when bypassing the passive crossovers, particularly in the Quest z, what have people done with regards to PC-based digital crossover (bass management?) and room correction? I'm guessing two DACs driven by AES/EBU sharing a common clock would be one approach, but I would like to hear the details of what has been done.
Very interested in this question. ive just purchased a minidsp shd which includes sophisticated room correction (dirac) and the ability to act as a digital crossover ie all filtering done digitaly before analogue signal formed. Currently just using the dirac room correction into a stereo amp(krell fpb400cx) into ML Prodigies. Using room correction alone has made a massive positive difference to the bass. The next step would be to bi amp and then use the internal crossover design settings on the minidsp so that the amps are only working on the signal they need to power the panel or woofer they are driving rather than wasting the energy being filtered out by the crossover. I presume this would have some benefits. the final step would be to go fully live and bypass the crossover completely. would love to go this way but ive got no idea if its even possible without a degree in electronics. one for the future perhaps and i'll keep a keen eye on developments here, thankfully the system sounds very nice as is. all the best, Phil
 

lifespeed

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Very interested in this question. ive just purchased a minidsp shd which includes sophisticated room correction (dirac) and the ability to act as a digital crossover ie all filtering done digitaly before analogue signal formed.
Yes, this one type of implementation I had in mind. I had anticipated using a Lynx AES16 card to output AES/EBU to two AES/EBU DACS like Schitt Yggdrasil, as I have learned I'm partial to the sound of the R2R ladder DAC chip topology. I'm not sure if the better clock of the Lynx card compared to MiniDSP will be significant.

I will comment that an active crossover application really needs to have the ML internal crossover bypassed, as the interaction of two filters will have unintended effects. However, this is simple, non-destructive and easily reversed if needed.

I have also experienced huge improvements from the combination of room treatment and room correction, in my case I'm using REW, although I may try Dirac.
 

heathy

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Yes, this one type of implementation I had in mind. I had anticipated using a Lynx AES16 card to output AES/EBU to two AES/EBU DACS like Schitt Yggdrasil, as I have learned I'm partial to the sound of the R2R ladder DAC chip topology. I'm not sure if the better clock of the Lynx card compared to MiniDSP will be significant.

I will comment that an active crossover application really needs to have the ML internal crossover bypassed, as the interaction of two filters will have unintended effects. However, this is simple, non-destructive and easily reversed if needed.

I have also experienced huge improvements from the combination of room treatment and room correction, in my case I'm using REW, although I may try Dirac.
thanks for the reply lifespeed, i'll post an update if/when I progress through the stages. be interested to hear how your dirac experience goes.
 

JonFo

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I presume this would have some benefits. the final step would be to go fully live and bypass the crossover completely. would love to go this way but ive got no idea if its even possible without a degree in electronics.
Hi, this is the correct way to do it. But you can experiment a bit by setting the Mini DSP to use a high pass for the panel at 340Hz, which is well ahead of the passive in terms of the crossover point.
And for the low-end, you will need to bypass the passive crossover, but that is straightforward, just hardwire the bass input terminals directly to the speaker connections internally. And disconnect the feed to the passive.
 

lifespeed

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Here's the schematic I posted. Off the cuff a modified panel drive circuit would include a large series cap like C2 170uF (which is about 6 ohms at 150Hz) and possibly some series R as shown. To really give an authoritative answer on what would be electrically correct, I would need some guidance on the transformer turns ratio from ML. Then a SPICE simulation would be run to fine-tune, really not a big deal at all.

The goal would be to reduce the high-pass function of the series cap below 150Hz so as to not add another pole to the digital filter. Really all I would want to do is DC-block the transformer. This could mean the pass band to the panel would (theoretically) extend pretty low, probably less than 70Hz. But of course signal content from the digitally crossed-over amp would only contain higher frequency content.

I did notice that, according to this schematic, the stators of the panel are both driven differentially even with a single-ended input. One stator is not ground.
 
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