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DEQX Premate 8 digital active crossover / DSP

voodooless

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You can certainly make a MiniDSP work, and I have said so repeatedly in this thread. But it would be nice if it had more computing power.
Yes, a combination of IIR and FIR should work very well for keeping DSP resources light, propagation delay small an performance still excellent.
Just divide 900 million by the sample rate to get the theoretical maximum number of taps. It's as simple as that ;)
That's if you disregard any other processing done, and the actual memory availability of the DSP for the tabs. In reality, you may need things like delay, which will eat up memory like crazy depending on your needs. Since MiniDSP is a generic solution, it will reserve fixed bits of the DSP even if you don't need them. This may limit you in what you can actually do, vs what the hardware is capable of. Obviously, this makes it easier for the user to understand.

Maybe DEQX does this differently? Would be an interesting feature to have. I I remember correctly, I think even the cheap Behringer DCX2496 has such a DSP resources counter where you can set up the DSP function until it runs out of resources.
 

Tranquility Bass

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Yes, a combination of IIR and FIR should work very well for keeping DSP resources light, propagation delay small an performance still excellent.

That's if you disregard any other processing done, and the actual memory availability of the DSP for the tabs. In reality, you may need things like delay, which will eat up memory like crazy depending on your needs. Since MiniDSP is a generic solution, it will reserve fixed bits of the DSP even if you don't need them. This may limit you in what you can actually do, vs what the hardware is capable of. Obviously, this makes it easier for the user to understand.

Maybe DEQX does this differently? Would be an interesting feature to have. I I remember correctly, I think even the cheap Behringer DCX2496 has such a DSP resources counter where you can set up the DSP function until it runs out of resources.
That's why I said theoretical maximum. Of course other processing will be needed and this will steal away clock cycles for FIR. However the SHARC does have FIR accelerators which can be deployed simultaneously to boost performance further ;) Ideally if you need serious FIR capability then PC hardware is the way to go ;)

cheers
 

Draki

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Not quite, the MiniDSP has 4096 taps in total which can be distributed over 2 to 8 channels. Meaning 512 taps per channel if you distribute the taps equally over all 8 channels. Of course, you shouldn't do this and you should reserve the taps for bass; MiniDSP says that each channel must have a minimum of 2 taps and a maximum of 2048. The DEQX has 4096 taps per channel for 8 channels, i.e. 32,768 taps in total. You can certainly make a MiniDSP work, and I have said so repeatedly in this thread. But it would be nice if it had more computing power.
MiniDSP should really release a 48K version for the Flex series, which now runs on 96K. It would effectively double the available taps.
I had asked, the response was unfortunately they have no plans.
I run the previous OpenDA8, on 48K, and can't fault it.
 

mglobe

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I realize this thread is about the Pre-8, a product that would serve a pretty narrow market. The one that interests me is the Pre-4, which has the functionality essentially of the MiniDSP Flex, and also to a large extent the NAD M66. Still a niche, but I suspect a much larger one. The NAD intrigues me, though I'm not sure if it is enough to make me want to spend the $$$ to upgrade from my Flex. It would be interesting to see how the Pre-4, M66, and Flex compare if/when the M66 and Pre-4 hit the market.
 

mitchco

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Realistically more taps cause more delay in the signal (2048/44.1k is 46mS already), which is why long FIR filters are really only useful for pure audio playback - they will mess with video lip-sync, live sound, monitoring or anything else requiring time synchronisation.
Just a quick note to say that a minimum phase FIR filter used in a zero latency convolver will not have any inherent time delay and therefore suitable for video lipsync.

This example is a stereo triamp system using minimum phase digital XO and digital room correction using 131,072 tap FIR filters with no delay introduced by the convolver or FIR filter:

minphaseFIRfilterwithminphasedigitalxo.png.b694acdd3f22f6119eef0f05639a8457.png


Hang Loose Convolver (HLC) displays the FIR filter latency in samples, which in this case is 0.

Another example using a Mac to decode 7.1.4 Dolby Atmos video content and to apply digital room correction using 65,536 tap minimum phase FIR filters:
https://pttyes.com/Audiophile/M.1665305318.A.4B9 Translate to English. Not that this solution is also using digital XO for bass offloading, so while it is 7.1.4, each speaker has a digital XO and routing the bass through the sub for a total of 23 convolvers required. Still perfect lipsync.

Yes. It would be even more difficult if it was a PC running Linux, given that I would then have to learn Linux.
Hey Keith, If you install a desktop OS, then you don't need to learn Linux :cool: HLC can process 32 channels of convolution using 65,536 tap length FIR filters at 48 kHz sample rate on Raspberry Pi4 with the desktop OS installed: https://audiosciencereview.com/foru...volver-from-accurate-sound.23699/post-1739880 With a few mouse clicks, you are up and running.
 

mcdn

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Just a quick note to say that a minimum phase FIR filter used in a zero latency convolver will not have any inherent time delay and therefore suitable for video lipsync.
But it will still have the group delay of the minimum phase filter? So "zero additional latency". Just checking I am understanding this properly!
 

mcdn

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Sure, but a minimum phase IIR filter still has group delay. Is the claim that a “zero latency” FIR filter has no group delay, or is it just that it has the same group delay as an equivalent IIR filter?
 

voodooless

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Sure, but a minimum phase IIR filter still has group delay. Is the claim that a “zero latency” FIR filter has no group delay, or is it just that it has the same group delay as an equivalent IIR filter?
FIR and IIR minimum phase filters are completely equivalent. They have the same group delay. The reason the FIR filter has no (or very little) propagation delay is that you can start the impulse response all the way at the beginning (you don’t need to “look back in time”).
 

mcdn

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FIR and IIR minimum phase filters are completely equivalent. They have the same group delay. The reason the FIR filter has no (or very little) propagation delay is that you can start the impulse response all the way at the beginning (you don’t need to “look back in time”).
Sorry I'm being a bit dumb perhaps, and still not getting the point. As I understand it, applying a minimum phase filter, whether it's an IIR or FIR filter, to a given signal input, will result in the same signal output in terms of amplitude and phase. Both have "zero latency" in that they give immediate outputs, but both have group delay. A 20Hz signal with a 10Hz low-pass applied is going to be delayed a bit in either case. Is my understanding wrong? (to be clear, for file based playback you can pre-convolve, and the same if your streamer has a plugin, that's not what I'm asking about)
 

voodooless

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A 20Hz signal with a 10Hz low-pass applied is going to be delayed a bit in either case. Is my understanding wrong?
Yes, group delay is a function of phase and frequency response in a minimum phase system.
 

ppataki

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Yes, group delay is a function of phase and frequency response in a minimum phase system.

I would not like to digress much from the original topic but I guess this post I made would show some good examples on that + also shows what happens if you use linear phase filters for the same:

 

eboleyn

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So there are a lot of opinions on this thread about DEQX and it's worth as a product. I thought I'd comment as an existing DEQX and MiniDSP FLEX owner.

I have used a Behringer DCX2496, used BruteFIR (and considered writing my own thing even), and ended up buying a used DEQX HDP-5 (the previous upper end of their product line), then later a MiniDSP FLEX unit. I also have a pair of Hypex FusionAmp FA253 units.

Quick assessment of the various options:
  • The Behringer DCX2496 was a great entry vehicle to try out active DSP crossovers, and I still have my unit for random experiments.
  • The MiniDSP FLEX is a very good value, though limited in its extent and the SW can be a bit convoluted to use depending on what you want to achieve.
    • This is how I run my high-end headphones by my bedside.
  • BruteFIR is awesomely powerful, though very DIY and you have to build the FIR filters entirely by hand, and it's not necessarily as cheap as you'd think because you have to assemble all the components together.
  • The Hypex FusionAmp FA253 units sound pretty amazing, though basically like an integrated Behringer DCX2496 unit (with a lower noise floor!) plus the Hypex amps. For some "living room" speakers which I'm trying to keep as simple as possible, we might stick with these!
  • The DEQX HDP-5 (a 3-way per side stereo unit, so 6 output channels in total) is crazy convenient as it JUST WORKS.
    • I liked it so much after buying it on a lark that it's my main way to run my "super-high-quality" desktop audio setup.
    • The 200+ db/octave linear phase crossover is just the tiniest bit better than the IIR style 48 db/octave crossovers, and it's my go-to.
    • I've liked the DEQX unit so much that I'm in the beta list for the DEQX Pre-8 series.
I feel like DEQX is a bit unfairly maligned. Specifically: So what that they're talking about charging $12K+ for the official release of the Pre-8? It seems like everyone is judging them based on the "DIY factor" of "could I do this cheaper?". Well, I have DIY built speakers which kick the butt of some that have cost many multiples more than the ones I built, and so I don't buy the best $10K or $20K speakers... but so what?

Frankly, the DEQX HDP-5 unit and it's super-convenient editing of crossover settings and creation of high slope linear FIR crossovers has been a ton of fun for me, and has worked great. Is it expensive? Sure. Would I like it to be cheaper? Yeah, honestly, I would, sure. Might that lead to competition that is cheaper but is similarly as convenient? Maybe. ... But til then I will probably continue to use the DEQX stuff at least in some of my setups.

Having said the above, I'll remind readers I said I do use a MiniDSP FLEX for my bedside high-end headphone setup, so I'm not going to go claiming that everyone should go "DEQX everywhere"...

BUT, I do think it's a pretty slick product, and I have enjoyed using them.
 
OP
Keith_W

Keith_W

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That is a very balanced assessment, @eboleyn. I think all of us put different weighting on different features, and ASR's response was quite predictable. It seems as if most people here put a high weighting on the price, and low weighting on convenience and useability. I fall into this group myself, I don't mind a bit of inconvenience and save a bit of money. However, there are some things on my computer based setup which are difficult to do, for example take any external digital signal or analog signal and process it. It is possible, but it is annoying to do - basically I have to dive into menus and reconfigure the system every time I want to switch sources. I am the only person in the house who knows how to do this, even basic functionality (turn it on, listen to music) is too difficult for my wife. My project from now on is to make the system less intimidating and more approachable for others ... something I wouldn't have to worry about if I was using a DEQX.
 

eboleyn

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That is a very balanced assessment, @eboleyn. I think all of us put different weighting on different features, and ASR's response was quite predictable. It seems as if most people here put a high weighting on the price, and low weighting on convenience and useability. I fall into this group myself, I don't mind a bit of inconvenience and save a bit of money. However, there are some things on my computer based setup which are difficult to do, for example take any external digital signal or analog signal and process it. It is possible, but it is annoying to do - basically I have to dive into menus and reconfigure the system every time I want to switch sources. I am the only person in the house who knows how to do this, even basic functionality (turn it on, listen to music) is too difficult for my wife. My project from now on is to make the system less intimidating and more approachable for others ... something I wouldn't have to worry about if I was using a DEQX.

I'm a bit older (over 50), and have done a lot of DIY over the years, and while as you could see from my description in the previous post I've tried many different things, at times there is just not enough time to do it all, so I freely admit I've "cheated" and used products that "just work" at times, with ASR being the one greatest source of knowing what to get... and so sometimes spend my time on things other than the DIY audio stuff. I know, Scandalous!

Haha, indeed my wife made it very clear to me many years ago that convenience and "unobtrusiveness" were at least for her the deciding factors for our shared family setups. She has at times in the past indulged me when I wanted to do something different, like when early in my active bi-amping phase had a Behringer DCX2496 in the living room HT setup. That didn't survive very long though, as it was too much of a pain to manage.

At this time our living room HT setup uses a Yamaha CX-5200 pre and VTV 8-channel Hypex amps, all controlled via a pretty easy-to-understand single remote control. The front 2 speakers are DIY with passive/analog 24 db/octave crossovers and sound very good (the wife said it looked like I was building a bomb with the giant capacitors and inductors, haha!), but ultimately the most important factor for her is that they "just work"... though she still complains that they should be painted dead black (I did say "unobtrusiveness" above, sigh).

Having said that, I still really enjoy the extra bit of clarity from my desktop setup with the DEQX HDP-5, multi-channel Purifi amps, using Purifi mid/woofers, RAAL ribbons, and a Rythmik sub. Yeah it's overkill, but fun overkill, and I'm still playing around with some more exotic things for fun like a Purifi mid/woofer-based line source.
 
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Old Hi-Fi Guy

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Haha, indeed my wife made it very clear to me many years ago that convenience and "unobtrusiveness" were at least for her the deciding factors for our shared family setups. She has at times in the past indulged me when I wanted to do something different, like when early in my active bi-amping phase had a Behringer DCX2496 in the living room HT setup. That didn't survive very long though, as it was too much of a pain to manage.

At this time our living room HT setup uses a Yamaha CX-5200 pre and VTV 8-channel Hypex amps, all controlled via a pretty easy-to-understand single remote control. The front 2 speakers are DIY with passive/analog 24 db/octave crossovers and sound very good (the wife said it looked like I was building a bomb with the giant capacitors and inductors, haha!), but ultimately the most important factor for her is that they "just work"... though she still complains that they should be painted dead black (I did say "unobtrusiveness" above, sigh).

For a moment there I thought we must be married to the same woman!
 

Sined

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Frankly, the DEQX HDP-5 unit and it's super-convenient editing of crossover settings and creation of high slope linear FIR crossovers has been a ton of fun for me, and has worked great. Is it expensive? Sure. Would I like it to be cheaper? Yeah, honestly, I would, sure. Might that lead to competition that is cheaper but is similarly as convenient? Maybe. ... But til then I will probably continue to use the DEQX stuff at least in some of my setups.
Same for me. After reading those comments in this discussion, I thought I may be the only one here who considers his DEQX processor as the best piece of audio equipment I've given to myself as a long time DIY speaker builder: eboleyn, I'm glad to see I'm not the only one! The DEQX processor is such a great tool to measure/calibrate speakers and tune them to your taste and to your room, and all this from a high quality audio DAC and preamp: as I used to say :"I wouldn't live without my DEQX" !!

I agree that a DEQX is not the cheapest way to go, maybe it deserves the "high-end" tag, but, hey... going active for a 3 way speakers is from the start, certainly not the cheapest way to build an audio system : 6 interconnects, 6 channels of amplification, 6 speaker cables... But the SQ I get from my "home made DEQX calibrated" speakers is absolutely incredible and for me, it worth the expense: that's my non objective biased opinion and no one is forced to contest or agree...! I'm so satisfied with the result that I even no longer have any intention to upgrade anything in my system (first time in my audio life...), except only for this new DEQX unit which I assume will be even better and would enable me to add a 4th channel for subs.... But I agree with you guys, $12K US..., I might be a true fan of the DEQX processors, but at this price point, it is too much asked for the benefits I could get over my good old HDP-4.

eboleyn, you mentioned that you registered as a beta tester: Do you have to buy the unit ? How intensive is the testing of the software, test all options for any possible configuration or simply test as you would use it normally ? Could share some information with me on the process? Thanks.
 

eboleyn

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That is a very balanced assessment, @eboleyn. I think all of us put different weighting on different features, and ASR's response was quite predictable. It seems as if most people here put a high weighting on the price, and low weighting on convenience and useability. I fall into this group myself, I don't mind a bit of inconvenience and save a bit of money. However, there are some things on my computer based setup which are difficult to do, for example take any external digital signal or analog signal and process it. It is possible, but it is annoying to do - basically I have to dive into menus and reconfigure the system every time I want to switch sources. I am the only person in the house who knows how to do this, even basic functionality (turn it on, listen to music) is too difficult for my wife. My project from now on is to make the system less intimidating and more approachable for others ... something I wouldn't have to worry about if I was using a DEQX.

I didn't respond directly to the "convenience" point's details before, but thought I'd throw some of it in for amusement (or horror)... but I really tried to make some of the DIY setups work properly and over time it really got exhausting.

First, a point of history: I was actually a video/TV DIY hacker many years before doing audio, due in most part to my sensitive high-frequency hearing. I.e. I could hear the flyback transformers in TV sets even in other rooms of a house and was driven mad by them. Some years later a friend ruined me for lo-fi audio and my audiophile (and then yet later DIY audio) history began.

Examples different setups:
  • Using an old large-format presentation computer monitor as a TV, then later a projector.
    • This had a computer as the input for playing DVDs, etc.
    • It ... mostly worked, but there was no remote control, so the wife made it clear that needed to be better.
  • Using MythTV with centralized recording computer in the house with multiple SFF PC player units.
    • This used a radio frequency remote control. It worked not too badly.
  • Ripped all our CDs (before audio streaming was a Thing) into a big archive, used a custom digital player setup for playlists.
  • Using a Behringer DCX2496 with separate amps per driver.
    • Switching the config between the HT system with surround speakers vs. the 2-channel "optimal music setup" was a bit of a pain.
Examples of convenience issues with nearly all of the setups:
  • Switching everything on/off and making sure that always happened.
  • What do you do when one of the units freezes or crashes in an unpredictable way?
  • With nearly all of the later options with audio involved, switching sound sources between analog and digital, and if the digital input was at a different rate than expected, it would not always work right, esp with FIR filters, which typically required more configuration tweaks on the spot.
  • Using a DEQX unit in the living room setup was one of the best, BUT it still had convenience integration issues with the living room HT/TV setup.
  • Having other people visit and try to use the system, even after I'd gotten the setups to work decently well, had been a Pain.
So, the wife has been dealing with "it mostly works" setups for many years, and over time has gotten gun-shy enough of it that every time even a normal piece of commercial hardware hangs and needs to be rebooted forcefully like unplugging and replugging it in, she gripes about it and says "this doesn't happen to other people". Hah!
 

dziemian

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I had Deqx 2.6 once. I sold it and switched to 8-channel minidsp NanoAVR which offered much more for much less. Then I switched to PC and Dirac Live (stereo plus 4 subs) The only thing which stood out for DEQX was an easy way to add turntable to the system with its analog line in. Nowadays DEQX is nowhere close to Dirac Live with Bass Control add-on, not mention upcoming ART (Active Room Treament). Even the newest Deqx can not control multi subwoofers the way Dirac does.
 

eboleyn

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eboleyn, you mentioned that you registered as a beta tester: Do you have to buy the unit ? How intensive is the testing of the software, test all options for any possible configuration or simply test as you would use it normally ? Could share some information with me on the process? Thanks.

Yes, we have to buy the unit. The SW is considered "Beta, and probably won't do anything to destroy your speakers" ... ok, I exaggerate, but they do caution that while they have been through internal testing and don't expect any serious issues, it would be wise to be a bit careful by, for example, putting protection caps on your tweeters and similar. The unit HW is supposed to be the final HW (with a proviso that if it is not, then for a nominal fee they will upgrade the beta units to the final HW), but the SW of course will continually update through the release SW as final developments, tweaks, and bugfixes are done.

As to the process to get involved, there is a News section of the DEQX website, and also some content on a Facebook page, both of which suggested that a beta program was planned on becoming available, and how to tell them you were interested. From there, eventually they sent out feelers describing that they were planning on having some number of pre-production units available to the first N people who signed up.

Anyway, I don't know what the full status is, but go check out the DEQX News section or whatnot and poke around and if you ask maybe some slots in the beta program might still be open.
 
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