Multi-Sub Optimizer (MSO): Lessons Learned, Tips & Tricks

[markstein]

I am in the process of making some tweaks to my 2.2 system, and wanted to use MSO. I've got an Okto Pro 8 on the way and want to run MSO for sub alignment.

Is there an idiot's guide somewhere?

Some basic questions:

• Do you measure both subs and mains or just subs (there seems some differing opinions in the info I have seen).
• If so, do you measure with crossover applied or not.

But really, these are just initial queries so any pointers would be gratefully received.

There is a great online manual available. You should work through it step by step.

MSO User Guide

The User Guide for Multi-Sub Optimizer, with detailed usage instructions for all program features.

www.andyc.diy-audio-engineering.org

 

[WeekendWarrior]

There is a great online manual available. You should work through it step by step.

MSO User Guide

The User Guide for Multi-Sub Optimizer, with detailed usage instructions for all program features.

www.andyc.diy-audio-engineering.org

Yes, I'd seen that but it seems mainly focussed on home theatre. I'll have a more thorough look but was wondering if there was a "how to" guide for stereo + subs applications.

 

[WeekendWarrior]

Ok, finally happy with setup. Things I learned for a 2 channel setup with 2 (passive) subwoofers and 2 main speakers, using MSO in the ''subs only'' mode.

I contemplated and experimented with the "subs and mains" mode but it had up and downsides. For instance the multi run option is not available, wich makes MSO V2.0 such an outstanding kit. Marrying the mains later is no problem and as long as you dont adjust gain and or especially delay, its no big deal. I found adding an All Pass filter to one or both mains was enough to cure any null.

Before going into MSO
- Start by levelling to subs and mains as much as possible, and only then make the measurements for MSO - level both channels and L+R input mono per sub, not stereo as MSO doesnt work for stereo;
- Then make sure you test the subs with only L or R input per sub, as this is how you will do the MSO measurements;
- Measurements is 50% of the work. Make sure to test fixed position and MMM techniques and analyse the results, different SPL's and analyseagain. Look at waterfall and if higher SPL measurements differ from lower;
- Its very, VERY important to recognise what is room influence and what isnt. Do you have the same problem at various measuring positions, or is it just at this or that position? Make a note of wich null or bump is to be left alone;
- Make sure there is at least a 40db difference with floor noise. When you finally happy and familiar with how your un-optimised channels perform, turn on acoustic reference and make the MSO measurements;
- Make sure and then make sure again the output matrix is correctly configured for the acoustic timing MUST HAVE. You have no idea how many hours i lost by making mistakes with importing the wrong measurements into MSO;

Into MSO
Some basic MSO graph settings advised by @DaveBoswell but might as well put it here when you have no time to watch his (fantastic) MSO V2.0 tutorial on youtube

Graphic settings
Axis assigments:
Left axis - Magnitude, Right Axis - Phase
Axis Parameters:
Limits for left Y axis: keep 60 db between up and down.
Limits for right Y axis: min value -360 max value 1800. deg/div: 180

In MSO Application settings make sure you choose the correct sample rate for your DSP.
Change PEQ settings to: max Q 9.0(8.6 is Dave's advice).
Max - db cut to: -15.
Change delay to 0 and 10 (instead of -10).
Change gain to max -5 and 5.
Change All Pass 2nd order max allowable Q to min 0.1 and max 0.6.

Some other usefull personal preferences in his video.

- Subs only config its better to implement an LPF in MSO than later in MiniDSP for instance;
- Every little boost added made it worse to only cut configs;
- Test with different reference SPL's;
- In addition: test where you make the cut low and high, wich window you want optimised. Sometimes its better to set lower limit at 30hz instead of 15hz for instance;
- Try to keep the output PEQs to about 4 or 5 per channel;
- After finalising and exporting still gives problems around the XO region, use REW to investigate wich main is giving problems with phase, then insert one or two All Pass second order filters with max Q of 0.7 AWAY from the XO frequency - put it 20hz lower or high but NOT on top of the XO;
- It helps to create 2 or 3 end result-configs, for instance with 3 different reference SPL's and see how that works in the DSP and the REW final measurements.


Note: the UMIK 1 has deficienies below 20hz. I suspect its not even that good below 30hz. Its very good for general use but remember its limitations.
Also: read as much as possible on the MSO threads at AVSforums and the MSO User Guide at creator @andyc56

https://www.andyc.diy-audio-engineering.org/mso/html/

https://www.avsforum.com/threads/op...-sub-optimizer.2103074/page-168#post-61897597

Another note: MSO was originally built for AVR use, equipment with one subwoofer output. Please note that most help at the AVS forum runs on such use, having 4 subs home theater setups and not 2 channel configs like we use a lot on this forum. Keep this also in mind when watching these great tutorials on youtube.



https://www.youtube.com/@jeffmery


For reference on my setup

Quad 34 pre amp (fed analogue sources) left and Right
into MiniDSP DDRC-24** (downgraded to 2x4HD to use MSO input filters)
output 1 (left) and 2 (right): Quad 606mki to main speakers (Revel F208)
output 3 (left and right) and 4 (left and right): Behringer inuke 6000D (in stereo mode*, all dsp turned off)
MSO config with 90hz LPF LR4 24dB filter, both in MiniDSP input and output 3 and 4
Mains output 3 and 4 has MiniDSP XO HPF filter at 100hz, 24dB LR4 (because F208 is front ported, sounds better unplugged)
2 Dayton Ultimax UMii 15" in DIY sealed 85 liter cabinets.

UMIK1
REW
MSO V2.0

*I can put the behringer in dual mono but it doesnt make any difference.

** The MiniDSp when you use the USB cable into the PC to work the plugin, it can put some unwanted extra distortion and funny noises when you move the mouse. I bought a simple €1 USB isolator and that fixed everything. For Dirac setup it needs the USB cable. Without, you can also use the MiniDSP Wifi dongle. (I use that now since the amps and MiniDSP are a few meters away from the PC and my desk). At the moment I see no added function for Dirac. I dont want the expensive F208 to lose their character and even when tried, I just could never make it work and it also made REW measurements worse.

A very last note: MSO is a very nice very complex program where you can lose yourself for hours, days, weeks with manipulating the tiniest detail. For me as nerd, I love it. When you are not, I hope the above helps to figure stuff out quicker. You dont need to spend weeks like me for basic upgrade results. In fact in a few days I already had good optimisation. I just like to know each tiny detail. Do respect it requires some study. If you figured out REW to a reasonable degree then youll figure out MSO too. Again, the end result is much better than any other correction program. Imo.

Perhaps I should have searched this thread a bit better...maybe this is what I'm after.

 

[andyc56]

Yes, I'd seen that but it seems mainly focussed on home theatre. I'll have a more thorough look but was wondering if there was a "how to" guide for stereo + subs applications.

Perhaps I should have searched this thread a bit better...maybe this is what I'm after.

The situation with regard to using MSO with two-channel systems where you're trying to integrate subs and mains is confusing. It's mostly the result of historical aspects of its development that I describe in a post on another forum. Because its development was driven by users' experiences on AVS Forum, its emphasis grew over time to be tilted heavily toward home theater (even though I'm a two-channel guy myself). A future version (V3) that's planned, but won't be released until 2027, aims to correct these flaws. But it's a big undertaking, as other enhancements are being added as well.

One thing to be concerned about for everyone, but especially two-channel users is the need to avoid incompatible hardware. In the docs, I mostly talk about "AVRs" in a generic way. If you're a two-channel user not using an AVR, this places the burden on you to understand the concept of bass management and implement it as used in AVRs. That means summing bass to mono, adding sub EQ that's common to all subs, then splitting the sub signal into as many paths as you have subs, with EQ and delay for each one. The approach of "rolling your own bass management" with dedicated DSP hardware is harder than using an AVR, because an AVR does this work for you.

An approach that's harder than using dedicated DSP hardware to implement bass management is to use a multi-channel DAC and implement the bass management in software. If you're a Windows user, it's possible to use Equalizer APO to do the "roll your own" bass management and EQ. This is described in a "Tech Topics" article in the MSO docs, and should be considered an "experts-only" technique. You'd have a better chance of success using a dedicated DSP such as the one described in this post.

Being a new user and choosing the "hardest of the hard" approach means a tough road ahead. The amount of support needed to get a new user up to speed on all the concepts needed to be successful with such an approach is outside what I normally do. The idea of having extensive documentation is to cover these bases, and if the user is lost, it becomes prohibitively time-consuming to teach all the concepts needed to point them in the right direction.

 

[WeekendWarrior]

The situation with regard to using MSO with two-channel systems where you're trying to integrate subs and mains is confusing. It's mostly the result of historical aspects of its development that I describe in a post on another forum. Because its development was driven by users' experiences on AVS Forum, its emphasis grew over time to be tilted heavily toward home theater (even though I'm a two-channel guy myself). A future version (V3) that's planned, but won't be released until 2027, aims to correct these flaws. But it's a big undertaking, as other enhancements are being added as well.

One thing to be concerned about for everyone, but especially two-channel users is the need to avoid incompatible hardware. In the docs, I mostly talk about "AVRs" in a generic way. If you're a two-channel user not using an AVR, this places the burden on you to understand and implement the concept of bass management as used in AVRs. That means summing bass to mono, adding sub EQ that's common to all subs, then splitting the sub signal into as many paths as you have subs, with EQ and delay for each one. This "roll your own bass management" approach is harder than using an AVR, because an AVR does this work for you.

Regarding the use of an 8-channel DAC to implement such a system, that's even harder than using dedicated DSP hardware. If you're a Windows user, it's possible to use Equalizer APO to do the "roll your own" bass management and EQ. This is described in a "Tech Topics" article in the MSO docs, and should be considered an "experts-only" technique. You'd have a better chance of success using a dedicated DSP such as the one described in this post.

Being a new user and choosing the "hardest of the hard" approach means a tough road ahead. The amount of support needed to get a new user up to speed on all the concepts needed to be successful with such an approach is outside what I normally do. The idea of having extensive documentation is to cover these bases, and if the user is lost, it becomes prohibitively time-consuming to teach all the concepts needed to point them in the right direction.

Thanks for your reply.

Yes, I believe my hardware is compatible and I had planned to use Roon as my DSP engine, which can (I understand) provide independent DSP to any/ all DAC channels. I hear your warning about complexity though, and perhaps I'll stick to REW for sub integration for now until V3...appreciate your prompt reply!

 

[-Matt-]

A future version (V3) that's planned, but won't be released until 2027, aims to correct these flaws. But it's a big undertaking, as other enhancements are being added as well.

@andyc56 It is great to hear that MSO is still receiving updates and enhancements. Thank you, and keep up the good work.

 

[DaveBoswell]

Thanks for your reply.

Yes, I believe my hardware is compatible and I had planned to use Roon as my DSP engine, which can (I understand) provide independent DSP to any/ all DAC channels. I hear your warning about complexity though, and perhaps I'll stick to REW for sub integration for now until V3...appreciate your prompt reply!

If you have not done so already, I recommend you check out the MSO tutorial videos Jeff Mery (aka @fattire on AVS) posted some years back on Youtube - while they are a bit dated as @andyc56 has made many enhancements to the app since the time the videos were made, the videos still give you a very good foundation of the basics of the measuring, uploading and optimizing process in MSO. I posted a tutorial video as well a year or so ago (link in my sig below) which is for some of the more advanced features in V2.0 (at the time) and how to interpret the graphical outputs MSO provides. The UI in MSO has changed a bit since then but for the most part the main concepts in the video are still valid.

That said, the videos are primarily for Sub Only configs as that has been the main focus over the last few years per Andy's note above. Looking forward to seeing what he cooks up in v3.0!

Hope this helps.

 

[john61ct]

Still noobish, but my current thinking is to do Sub Only. I have a surround setup planned without AVR, and most woofer/sub speakers are part of co-located stacks fed by the bed channels, mostly LCR.

The mono trueSubs (strictly under <80Hz) to be managed by MSO will have their own separate DSP, so far plan is an RPi5 with the HiFiBerry 8ch DAC HAT interface, using Pipewire native IIR filtering.

Likely fed by a LPF split off the Center channel, but there are also two sub mono outputs upstream, including Wiim Ultra, so will test those too.

These can ofc be freely placed, will try to optimise placements to handle room effects before applying MSO.

The fact that this mono trueSub group is not tied into the BNC clocking on the other interface/converters handling the FR Stereo domain

could mean some clock drift effects, but this whole mono sub group being <80Hz gives a lot more leeway before phase issues become acoustically perceptable.

Going this way "Modularised DSP ™" will make it easy to not only switch to different signal sources, but to simply drop the group completely when space is limited going on the road

or to experiment in enabling envelopment, all subs being stereo.

 

[win]

@andyc56 It is great to hear that MSO is still receiving updates and enhancements. Thank you, and keep up the good work.

Was gonna say the same. I use my MSO-tuned 2.4 system every day and still can't believe how smooth the bass is. I also use Dirac (via flex htx).

Andy is a saint.

 

[andyc56]

Andy is a saint.

Oh man, I cracked up when I saw this. Nothing could be further from the truth. In fact, I have a well-deserved reputation for orneriness. For instance, my ignore list on AVS now has around 700 people on it.

MSO continues to be developed mostly as something to keep my mind active in retirement, which I've heard can help stave off age-related mental decline.

But thanks for the undeserved compliment! I'm glad your system is working well.

 

[Keith_W]

Anybody who writes and distributes a high end tool like this for free deserves compliments. You could be making money from it, but instead you are giving to the community.

 

[PaulF2020]

Was gonna say the same. I use my MSO-tuned 2.4 system every day and still can't believe how smooth the bass is. I also use Dirac (via flex htx).

Andy is a saint.

Do you use MSO + Dirac? If so how exactly you're using it?

My understanding is that MSO filters will only make sense to apply on per-channel basis since Dirac then applies correction to entire channel.

 

[Onetrack97]

Do you use MSO + Dirac? If so how exactly you're using it?

My understanding is that MSO filters will only make sense to apply on per-channel basis since Dirac then applies correction to entire channel.

I used MSO for 7 years, first with Yamaha YPAO, then with Marantz Audyssey MultiEQ.

I purchased Dirac DLBC and tried it with MSO, all subs going through the MiniDSP. It worked well.

Then I tried DLBC with the subs connected directly to the AV30. I was able to achieve similar results but I did spend some time working on the LF. I will stay with this because now my subs use the balanced cables which eliminated some hum.

 

[win]

Do you use MSO + Dirac? If so how exactly you're using it?

My understanding is that MSO filters will only make sense to apply on per-channel basis since Dirac then applies correction to entire channel.

You tune the combination of your subs for best performance with MSO, using DSP for each individual sub. They all receive and play the same channel, usually mono summed low pass 80hz. So they end up playing a single channel in concert.

Then, you tune each channel with Dirac afterwards. It will individually tune the filters for left, right, and your mono summed bass channel, not seeing your unique subwoofer curves at all.