Passive Crossover bypass – Quest / reQuest

[lifespeed]

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]

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]

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]

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]

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]

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]

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]

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.

 

[Shaftish]

I´m thinking of do a semi active solution on my ReQuest´s. Just do the bas. Since ReQuest have bi-wire/amp connections a guess that I don´t have do anything else than connect bass driver to bass connections? Seems like a quick job.

 

[Zwick]

Just did it. Even better to go step 2 and bypass the bass crossover circuit completely by using external crossover or amp with crossover. Lots of info here.

 

[Leporello]

I´m thinking of do a semi active solution on my ReQuest´s. Just do the bas. Since ReQuest have bi-wire/amp connections a guess that I don´t have do anything else than connect bass driver to bass connections? Seems like a quick job.

If you just feed the bi-wire bass connection, without doing anything else, you'll still be going through the internal LPF.

 

[Shaftish]

I have now connected a dsp and one more amp for the woofers.
I haven´t done anything with the passiv filter. Seems like a long way back if I don´t like the end result. Or is it worth it?
Or shold I just disconnect woofer filter? I understand that there is were the big benefit is, or am I´m wrong?

I have done this mod Hifi-Zenit - Das Hybrid Bassproblem
So, some of the problems with Logans original filters have been sorted out.

They renovated my panels as well. Hifi-Zenit - Der Elektrostat

 

[DanR]

I have now connected a dsp and one more amp for the woofers.
I haven´t done anything with the passiv filter. Seems like a long way back if I don´t like the end result. Or is it worth it?
Or shold I just disconnect woofer filter? I understand that there is were the big benefit is, or am I´m wrong?

I have done this mod Hifi-Zenit - Das Hybrid Bassproblem
So, some of the problems with Logans original filters have been sorted out.

They renovated my panels as well. Hifi-Zenit - Der Elektrostat

Here’s what I did with my Odysseys
https://www.martinloganowners.com/members/danr.12/

 

[DanR]

Here’s what I did with my Odysseys
https://www.martinloganowners.com/members/danr.12/

That didn’t work well let me try again

 

[DanR]

Go to this thread in the forum
Main discusions and on pg 1 I have pics of how I disconnected my Odyssey factory passive bass xover
Guide for active crossover for Prodigy?

 

[Robert D]

Another option would be to have a shop do all of the work for you. I've got an audiophile store here that would probably do my Prodigies if I asked, or one of the guys could do it off the clock on his own time. Just an option.

 

[Shaftish]

Go to this thread in the forum
Main discusions and on pg 1 I have pics of how I disconnected my Odyssey factory passive bass xover
Guide for active crossover for Prodigy?

Hi DanR, I can´t seem to find the discussion you are refering to.

May I ask what wooer you choosed and why? Do you think that there is better suited woofer out there to my Request?
Regarding DSP, I have tried 2 and they don´t sound all that good throu the panel. I think they are doing a good job with the woofer but the panel have so much better resolution. So I think I will have to run panel straight from my pre-amp wich is kind of sad, Mc275 could use the filter to have more available power to the panels.

 

[DanR]

Lets try this
https://www.martinloganowners.com/threads/guide-for-active-crossover-for-prodigy.19708/
Read thru this and see what you think

 

[DanR]

As for the woofers I chose there are 2 pair in the Odysseys one front and one back on each speaker. I looked at the woofer enclosure volume and went on Parts Express web site and ordered the speakers from them.

 

[DanR]

I’m not sure if parts express ships to Sweden or not