First pass at overall system plan, DSP multichannel - "simple version"

[john61ct]

context, end goals

Principles: Time of Arrival Delays, vs Phase tuning ?

Relevant https://www.audiosciencereview.com/forum/index.php?threads/sub-with-2ch-amp-and-no-bass-mgmt.71655/post-2608483

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Analog crossovers, only using DSP to treat issues the analog system cannot fix

If I have Main L/R comprised of a mix 2- 3-way speakers + midbass couplers + stereo trueSubs all co-located Those subs easily switched to mono if that turns out to test better, there are also other trueSubs already in mono thus freely placed, can be treated as a single sub-group in the DSP...

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Please only post here to give feedback on this specific combination of hardware - or anything about DSP is especially welcome. Dirac, AV gear etc is not, nor requiring use of a PC as music player / renderer.

if you have suggestions on what is outlined in the above linked more general threads, please discuss in that thread, I will then crosspost back here, those bits (once resolved) relevant to this thread's intended topic(s).

FYI, Schiit SYN is an RCA analog preamp and upmixer to "simulated surround" - input stereo, output 5.1 RCA. That unit is "a given" in my proposed system here, even if only as a placeholder

If you want to discuss SYN specifically, please post here

https://www.audiosciencereview.com/forum/index.php?threads/schiit-syn-dac-preamp-hp-amp-review.68198

Please no anti- Stereo Subs discussion here, maybe post here

Understanding subwoofers

Or you can have full range mains with cardioid down to 40Hz, monopole to 20Hz, side (of MLP) cardioid subs to 40Hz, dual monopole ULF to 15ish Hz directly behind MLP. Finish it off with center tower with cardioid to 40Hz … sounds real good to my ears ;) More than one way to skin the...

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REW to be used throughout, not only for measurement but creating filters, maybe rePhase as well, if FIR is needed.

...

So, on to this specific proposed system:

Wiim Ultra up front, its Stereo output feeds (at FR*) to Schiit SYN directly via USB, TOSlink or analog RCA, tbd.

The SYN F-LR output pair feeds miniDSP 2x4 HD direct RCA analog.

miniDSP use case A:

filter crossovers for top speaker pair in colocated F-LR stack LS50s + DIY "MBM Basstands"

more context if interested

Crossover / Bandpass for LS50 "Bass Stands" and HT/SYN

To try to keep my "Budget tall mid-bass to sub speaker, to act as stand for LS50s" thread https://www.audiosciencereview.com/forum/index.php?threads/budget-tall-mid-bass-to-sub-speaker-to-act-as-stand-for-ls50s.63906/page-4#post-2394261 limited to OTS products like Rythmik FM8, or on the DIY...

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...

If it makes sense to use a high SQ analog HPF on LS50s, AND no phase tuning / flight time delays are needed there, then maybe

miniDSP use case B:

filter crossovers for next speaker pairs down in the F-LR stack - "MBM Basstands" above and a trueSub below, one in each colocated F-LR stack. I want the option of testing, feeding each of those trueSubs decorrelated Stereo signals, or mono if that tests better.

/end F-LR, end miniDSP

...

For all the other (optional) channels, looking at a cheap-as-possible 8ch DSP, likely based on RPi5 (HLC or CamillaDSP) and/ or ADAU1452 (SigmaStudio). Might play with Pico DSPi also, but still in rapid development. To the extent possible all DSPs clock sync'd maybe in-signal but preferably via BNC wird clock.

(And yes, maybe a cheap and "silent" PC with multichannel interface(s, all clocks sync'd) instead but no diversionary tangents on that please.)

SYN Center output feeds up to 3x channels, similar "full stack" as F-LR but obv mono only, ideally slightly higher max-clean SPL is possible.

Rear Surround pair, likely just 2 outputs, but in future less "simple" iterations, might expand Stereo Bass / envelopment experimentation, MBM / subs to be co-located with those, at that point likely more DSP capacity needed for that.

...

We now have up to three additional non-bed output channels to use for (additional?) mono trueSubs, as needed for tackling LF room resonances.

Fed by (either SYN's 80Hz fixed sub output, or more likely from) Wiim Ultra's more flexible mono sub output, since that has strong LF crossover controls - I may want to test overlapping the front bed "stacks" above 80Hz where the MBM couplers are running, maybe even up to the room's Schröder transition.

Wiim also enables some some additional light-handed spot EQs if needed, but not talking any full-on DRC just yet.

Finally, Wiim can correct for flight time delays, at least for between stereo FR overall vs mono trueSubs

miniDSP 2x4 HD can also correct that way, but only within its MBM portion of the stack

...

I plan to first use the two other standalone DSP units

after lots of sub-crawl placement and crossover / flight time iterations, to get ALL the channels aligned wrt FR magnitude and phase, as finely as possible, before this next optional section.

My current thinking, is to next use MSO for creating filters for these mono trueSubs.

Possibly also for any mono trueSubs in the bed "stacks", whether above or below 80Hz - but that gets more complicated.

This is really the area in which I'm least knowledgeable.

@andyc56

@Keith_W

...

Finally, overall DRC. This really should be a separated process and maybe hardware implementation since the system will get moved between spaces, including used outdoors off grid.

In this first "simple" iteration, Wiim + the others can do some basic PEQ / RoomFit

In future I want to experiment - Acourate, GSonic, LinFIR, Umami, DecayCore, FXroute etc

Full-on FIR will require more processing power.


* if the bottom-most subs fed from either Wiim output need it, give the signal a HP rumble filter, e.g. 15Hz, otherwise no FR crossover-related filtering by Wiim I think.

...

HH1 Modularised DSP ™ strategies

 

[Keith_W]

Please draw a diagram with your proposed layout. It's clearer. It's also not obvious how many speakers and subs you are planning to use. The problem I see in your system is that you are planning to implement DSP at two different hardware levels (Wiim and MiniDSP). This can be made to work, but designing the filters may be quite difficult for a beginner.

 

[thcdru2k]

Avoid overlapping bass management whenever possible. If your colocated subs are acting as extension of the main speakers I would integrate left side as one "speaker" than right side as one. Than figure out what is happening when they interact.

 

[john61ct]

Yes that will be my default approach to start, pure L/R stereo. Maybe even jump the gun and try out the several DRC filter creation tools that only work in Stereo mode, no crossovers, or timing / bass management, no multichannel e.g. Gsonic

before moving on to 5.1

If I do get MSO managing freely placed non-bed mono subs, the next step for testing will be to add the Center sub(s) to that group and compare.

MSO is apparently ONLY effective to the extent the speakers it is managing have significant overlaps. And as MIMO (?) having 5+ separate channels may allow for better results than just 2-3.

After that, IF I decide to have more subs (more likely with the bottom-most ones) in the F-LR stacks as mono rather than stereo, then test adding those as well, possibly the total MSO pool could be up to nine.

Of course the result may not get better, or such diminishing returns that I go back to just managing those last only as part of each F-LR stack, and maybe switching even the lowest subs back to Stereo for further testing.

Note also that I may likely only be treating MSO mode as optional, enabled for dance parties and watching films, when smoothing room resonances over a wider LP is desired.

It is possible that with critical music listening at a single LP, I may prefer turning MSO off, and perhaps also (separately) testing turning the non-bed mono trueSubs into Stereo surrounds placed against the side walls, and/or enabling a Center Rear.

Somewhere in there, or perhaps using a cut-down simpler config, is the goal of trying to increase the odds of gaining the perception of envelopment, while I suspect MSO decreases those odds with its emphasis on smoothing resonances.

And then, there are further immersion multichannel and bass management schemes enabled by DSP with lotsa subs to be attempted, without the likes of ART.

It's this testing journey - and my learning curve - that are the primary goals, not just a single "optimal" target result.

Avoid overlapping bass management whenever possible. If your colocated subs are acting as extension of the main speakers I would integrate left side as one "speaker" than right side as one. Than figure out what is happening when they interact.

 

[john61ct]

Please draw a diagram with your proposed layout.

I may do that but it will be very crude, like a phone-photo of a hand drawing.

Meantime have you clarifying questions?

> It's also not obvious how many speakers and subs you are planning to use.

That's because to that extent those decisions have not yet been made. To get down to ~20Hz at decent SPL within my form factor constraints may mean two octaves is not possible. The F-LR MBMs may get down to say 60-70Hz, the Center might get there with just one bigger box

all that remains to be seen from testing actual physical implementation choices.

The Wiim will likely have a very minor role in DSP, practically none in the crossovers and related timing issues. There will (in this thread's thinking) need to be at least two additional DSP units if affordable non-PC options are limited to 8 analog outputs each (explicitly verified clock-sync'd)

> designing the filters may be quite difficult for a beginner

Great, exactly what I'm after! But I agree, baby steps early in the learning curve.

I might even temporarily use Dirac / DLBC and then try to match those results just as a learning exercise. Eventually selling them on once my use of, say Acourate, eventually surpasses them

 

[Keith_W]

Well, making decisions on a system is kind of pointless if you don't know how many speakers and subs you need to control. You need one DAC channel per speaker or sub. So I am counting how many outputs you get from a MiniDSP and it's not enough for a 5.1 system, which makes me wonder why you chose that configuration of DSP. The first thing you need to do is nail down how many DAC channels you need, and for that you need to know how many speakers you need to control. This is why I asked for a diagram, your system, as you laid out, makes no sense.

And, as I have said a few times before, Acourate is the wrong tool for designing minphase IIR filters. I would simply use REW. REW should have more than enough DSP for your needs ... and if you need something more capable than REW for minphase IIR, then you know more about DSP than I do. There are people like that around on ASR, i'm just not one of them.

 

[3ll3d00d]

Way too confusing to read and understand which suggests either the ideas are similarly muddled in your head or you just have difficulty communicating it in written form. For a first system it looks extremely complicated and the probability of failure is surely very high, highly recommend starting simpler and iterating, at least break it down into phases and get each phase working reliably before moving on.

 

[john61ct]

Well, making decisions on a system is kind of pointless if you don't know how many speakers and subs you need to control. You need one DAC channel per speaker or sub. So I am counting how many outputs you get from a MiniDSP and it's not enough for a 5.1 system, which makes me wonder why you chose that configuration of DSP.

I thought I made it clear there is no way I can afford miniDSP even if I thought they were the bee's knees which I don't.

I stated I likely need 16 analog output ports, and will use the miniDSP 2x4 HD for two critical pair in the F-LR stacks.

I found one unit at a crazy low price just for initial learning and practice, and do not plan to buy anymore of them.

> The first thing you need to do is nail down how many DAC channels you need.

Not possible, as stated, until I know more about how tge DIY boxen perform, start building and measure. The context threads give specific counts even xover frequencies but all that is speculative at this point and IMO just gets in the way of the bigger-picture overall architectural issues I'm looking for feedback on.

> And, as I have said a few times before, Acourate is the wrong tool for designing minphase IIR filters.

Yes I realize that. I stated I anticipate I may need to get into FIR and mentioned the FIR creating tools in that light

It would be great if I don't, I hope you're right.

 

[thcdru2k]

I thought I made it clear there is no way I can afford miniDSP even if I thought they were the bee's knees which I don't.

I stated I likely need 16 analog output ports, and will use the miniDSP 2x4 HD for two critical pair in the F-LR stacks.

I found one unit at a crazy low price just for initial learning and practice, and do not plan to buy anymore of them.

> The first thing you need to do is nail down how many DAC channels you need.

Not possible, as stated, until I know more about how tge DIY boxen perform, start building and measure. The context threads give specific counts even xover frequencies but all that is speculative at this point and IMO just gets in the way of the bigger-picture overall architectural issues I'm looking for feedback on.

> And, as I have said a few times before, Acourate is the wrong tool for designing minphase IIR filters.

Yes I realize that. I stated I anticipate I may need to get into FIR and mentioned the FIR creating tools in that light

It would be great if I don't, I hope you're right.

2x4HD when I used it for full range 2.2 DSP resulted in clipping above moderate volumes for me. I never figured out why. For 2.1, with simple crossovers / less filters it is not clipping. Just something to consider

 

[john61ct]

Interesting. One alternative is dedicate it to processing the MSO group only if that turns out to be four or fewer subs.

Having two inputs means I could AB test between Wiim's and SYN's ".1" channel

 

[thcdru2k]

Interesting. One alternative is dedicate it to processing the MSO group only if that turns out to be four or fewer subs.

Having two inputs means I could AB test between Wiim's and SYN's ".1" channel

Yeah I had no issues when I used it for four subs. The clipping was only an issue when I started to ask it to do full range calibration

 

[3ll3d00d]

I asked an llm to summarise for you, is it correct?

                                MUSIC SOURCES
                                      │
                                      ▼
                                WiiM Ultra
                    (streamer / volume / PEQ / delays)
                                      │
                                      ▼
                                 Schiit SYN
                  (derive Centre + Surrounds from Stereo)

     ┌──────────────────────┬──────────────────────┬──────────────────────┐
     │                      │                      │                      │
     ▼                      ▼                      ▼                      ▼

 Front L/R              Centre Out           Surround L/R          Mono Sub Out
     │                      │                      │                      │
     │                      │                      │                      │
     ▼                      ▼                      ▼                      ▼

 miniDSP 2x4 HD         Future DSP           Future DSP         MSO / DSP Engine
(front crossover)       (centre stack)       (rear stack)      (room-mode subs)

     │                      │                      │                      │
     │                      │                      │                      │
     │                      │                      │             ┌────────┼────────┐
     │                      │                      │             │        │        │
     │                      │                      │             ▼        ▼        ▼
     │                      │                      │        RoomSub1 RoomSub2 RoomSub3
     │                      │                      │
     │                      │                      │
     │                      │                      │
     ▼                      ▼                      ▼

┌───────────────┐    ┌───────────────┐    ┌─────────────────┐
│ Front Left    │    │ Centre Stack  │    │ Rear Surrounds  │
│               │    │               │    │                 │
│ LS50          │    │ Centre Spkr   │    │ Rear L          │
│ MBM           │    │ Centre MBM    │    │ Rear R          │
│ Front Sub L   │    │ Centre Sub    │    │ (+ future MBM?) │
└───────────────┘    └───────────────┘    └─────────────────┘

┌───────────────┐
│ Front Right   │
│               │
│ LS50          │
│ MBM           │
│ Front Sub R   │
└───────────────┘


                    MEASUREMENT / OPTIMISATION LAYER

 REW Measurements
        │
        ▼
 Manual delay / phase / crossover tuning
        │
        ▼
 MSO (multi-sub optimisation)
        │
        ▼
 Future FIR room correction
 (Acourate / CamillaDSP / LinFIR etc.)

Stereo Source
      │
      ▼
  WiiM Ultra
      │
      ▼
  Schiit SYN
      │
      ├── Front L/R ──► miniDSP ──► LS50 + MBM + Sub (L/R)
      │
      ├── Centre ─────► DSP ──────► Centre + MBM + Sub
      │
      ├── Surrounds ──► DSP ──────► Rear Speakers
      │
      └── Mono Sub ───► DSP/MSO ──► Distributed Room Subs

 

[3ll3d00d]

If so, I stand by my "that's a complicated setup for a first go" point but not necessarily any harm in that!

 

[john61ct]

I asked an llm to summarise for you, is it correct?

Wow thanks!!

Very hard to parse on my phone, so I'll address each point with a separate comment.

There are only two DSPs. One is the miniDSP 2X4 HD and that is not necessarily devoted to splitting the F-L/R channel.

I'm thinking it may get dedicated to the mono trueSub group if 4x ports is enough.

Of course, if the "otherDSP unit" can go past 8 analog ports cheaply enough, it would be easier to only have the one.

 

[john61ct]

If so, I stand by my "that's a complicated setup for a first go" point but not necessarily any harm in that!

Well going to 7 + base channels as a starting point is geometrically more complex, add height units, no mono bass even more so.

If a Lexicon MC-10 showed up on eBay for under $500 I might be tempted one day LOL

 

[john61ct]

Room-mode subs (MSO maybe managing) are not necessarily limited to away from bed channel stacks.

In fact pretty sure at least one from the F-Center is part of the group. Maybe more from F-L/R stacks if/when they are fed mono.

Some of that mono group may get tested Stereo "side subs" or switched between "critical listening SLP mode" and "family film night" vs "dance party" modes.

Center Rear sub is a possibility, mono so likely always in that Room-mode group.

Maybe an overlay or colour coding best to designate that attribute, meantime can just be represented as a single mono Sub output channel as the bottom-most Center sub for a simplified block diagram - only MSO "knows" its split-output ports are getting varied signals.

If the count does go past four for that group, then it might get its own 8-port RPi as DSP.

 

[john61ct]

As for height of the stacks, cannot say if one or two trueSubs will be needed. If two then Sub1 is the bottom to get to 20Hz or lower, and Sub2 blends with MBM, at least on the front three stacks.

However if the MBM can go from ~200Hz all the way to 40-50Hz (see Wiim Pro Sub thread) then only one trueSub needed below that.

I hope F-C needs no more than two in the stack, but three is possible, likely trueSubs rather than any MBM.

Rear Surround likely just one small FR pair. However if doing Stereo Subs out in the room likely should be collocated there?

In which case maybe no need for more than one mono freely placed, no need for MSO? Or only for "family film night" vs "dance party" modes , stereo room subs only for "critical listening SLP mode".

All tbd by testing...

/end comments on diagram

other that thanks again! I think will help those visually minded...

 

[john61ct]

Reminder, top notch variable Loudness contouring is a must, automatically varying with volume level control.

Pre-amps with Loudness - OSD Pre-1 ?

Most of my source-switchers and volume controls are analog-only, which is my preference. I am also frugal, some months actually poor 8-( I like having physical tone controls, and miss the old variable loudness curve feature, ideally automatically coupled with the volume level, but I guess that...

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Schiit's FB via Eitr 2 (or Mimir) may be superior, phone as remote

but their new Vestri DACamp is now also a multi-use tiny portable candidate, wired between Wiim Ultra USB output and going into Schiit SYN analog

maybe using my Aphex 124 at the far end for clean distance, or worst case PocketADC at LP into SYN's TOSlink (yuck)

If the Chase RLC-1 preamp is just as good, I already own that, easy peasey but a pain to disable the LC. Could be repurposed as relative bass-level only boost (maybe INSTEAD of LC ?)

If GFP-555 is best, gets a little more awkward, no remote.

Ordering integrating OG Analog preamps with Wiim Ultra as hub

I am sure this is DUH! territory for them that-know-more-than-I but thought it might be helpful to log my thought process and maybe get some feedback if I am off track. I want to route all sources through a Wiim Ultra in order that (if I use DSP) its PEQs and Roomfit may help, and also the...

www.audiosciencereview.com

 

[john61ct]

Forgot about this cheap 8ch DAC, one per RPi4B downstream Modularised DSP ™

8ch DSP on a shoestring? (SURE WONDOM AA-AB41173)

The Sure Wondom AA-AB41173 is essentially a multi-channel DAC with USB input. A Bravo SA9128 chip provides USB input, as well as 4 I2S outputs for the bottom board. A connector then routes the I2S signals to four PCM 5121s and provides eight output channels. You only need to provide 5V and data...

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