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

[3ll3d00d]

If you want to try out methods of getting an even response and want to use MSO then I would configure the subs as a mono pair under the stereo 3 ways and do a sub only run in mso. I would use far fewer PEQs and also try including an all pass filter. There are multiple strategies you can use here which may sound different in your setup. You can then compare this to a stereo 4 way setup (unlikely to be using MSO) using prefilters (macro 0) which you design (or use something like rew to design) using measurements taken at multple positions Vs a pure acourate setup (single point measurement)

 

[Keith_W]

Thank you. I will try that.

 

[FrantzM]

Hi

I have used MSO and thought my results were good.. that was until two thing as happened:

1. I re-arranged my furniture's: I added a small table in the back of the room. The subwoofer that was in the back will be moved somewhere else.. in the back.
2. My miniDSP died, thanks to my using the wrong power supply.. Sending 51 VDC to it, courtesy of a similar looking power supply that was for a nearby PoE switch.

I am in favor of presenting an optimized subwoofer, call it the MSO-subwoofer to Audyssey. Let Audyssey do its things of integrating the other speakers (L,R,C, Surrounds, Ceiling Atmos) with this MSO-ed virtual sub. I don't intend to use MSO for mains and sub integration, only for subs and let Audyssey via the Windows app take care of the rest.

I will have to re-measure and ... I need to understand and make sure I do it right this time, because reading through the copious documentation, I might have done it all wrong and was simply lucky, so... I am exposing myself here as an utter ignoramus b/c:
I didn't perform the "Timing Reference" step.
I simply measured each subs at the MLP and luckily the levels were the same.

My questions now.
How do I establish the Timing Reference in my system? Is this even necessary?
What is the best way to match the gains/reference levels of the subs at the MLP positions, via REW, before MSO?
Do I need to match the levels of each subs at the MLP? What is the recommended method: Use the subwoofer gains potentiometer? Or use the miniDSP input gains? I personally prefer to use the subwoofer potentiometer to do so but , you know more, so I am asking.

Let me know and I apologize if this has been covered already. In which case point me toward it

Peace.

 

[kiwifi]

Hi
My questions now.
How do I establish the Timing Reference in my system? Is this even necessary?

You are in luck! I have just completed a re-MSO of my four subs today, so it is fresh in my mind.

Yes the timing reference is necessary. Feed the accoustic reference output from REW to one of your main speakers. If you have separate amps, then go directly into the amp. Otherwise use a direct input on you pre-amp, AUX or multi channel input, disable Audyssey for that input.

What is the best way to match the gains/reference levels of the subs at the MLP positions, via REW, before MSO?
Do I need to match the levels of each subs at the MLP? What is the recommended method: Use the subwoofer gains potentiometer? Or use the miniDSP input gains? I personally prefer to use the subwoofer potentiometer to do so but , you know more, so I am asking.

I use Audyssey to set the individual subwoofer gains to 75dB at the MLP. If you run XT32 with the subs turned off, you get the opportunity to set the sub output level.

I use a combination of attenuation in the DSP plus adjustment of the gain knob on the sub. I like to have -12dB of attenuation at each sub output in the DSP, before entering the MSO filters. The MSO filters will be a combination of gain, delays and PEQ filters.

If you use cut only filters, which you should, to maintain headroom, then you will likely need to add some output gain to restore your 75dB levels for each sub, once the MSO filters are installed. Hence the -12dB starting point.

 

[FrantzM]

You are in luck! I have just completed a re-MSO of my four subs today, so it is fresh in my mind.

Yes the timing reference is necessary. Feed the accoustic reference output from REW to one of your main speakers. If you have separate amps, then go directly into the amp. Otherwise use a direct input on you pre-amp, AUX or multi channel input, disable Audyssey for that input.


I use Audyssey to set the individual subwoofer gains to 75dB at the MLP. If you run XT32 with the subs turned off, you get the opportunity to set the sub output level.

I use a combination of attenuation in the DSP plus adjustment of the gain knob on the sub. I like to have -12dB of attenuation at each sub output in the DSP, before entering the MSO filters. The MSO filters will be a combination of gain, delays and PEQ filters.

If you use cut only filters, which you should, to maintain headroom, then you will likely need to add some output gain to restore your 75dB levels for each sub, once the MSO filters are installed. Hence the -12dB starting point.

Thanks FOr the quick reply. I apologize for being dense , but here are some of my questions:

Yes the timing reference is necessary.

Why? Is the acoustic timing reference important in the context of two subs, not Mains + SUB integration? Want to understand what I am doing, help me refine the process for me and remember it.

Feed the acoustic reference output from REW to one of your main speakers.

How? That is where I am lost: That "Timing Reference" is used how? I go to REW and send this Timing Reference to the AVR? How do I do that? How does that relates to the rest of the process? I send it, how it becomes a reference? If it is not henceforth tied to all my other measurements? What am I missing?

I use Audyssey to set the individual subwoofer gains to 75dB at the MLP.

That I get.. I can do that ... but

If you run XT32 with the subs turned off, you get the opportunity to set the sub output level.

Don't understand... Why would I run XT32 with the subs turned off? My process would have been to massage the subs via MSO. Obtain a super-smooth, super flat subwoofer in the room from 15 to 200 Hz, and present this "ultra sub" to Audyssey to integrate it with the mains? Again What am I missing?

I use a combination of attenuation in the DSP plus adjustment of the gain knob on the sub. I like to have -12dB of attenuation at each sub output in the DSP, before entering the MSO filters. The MSO filters will be a combination of gain, delays and PEQ filters.

That would mean what? -12 dB with respect to the max sub output or ??? I understand that the MSO filters are a combination of, in my case , mostly cuts and some positive gains, not much more than 3 dB in my case, since my subwoofers, so far are cheap and with a 150 watts. I will upgrade to better subs, for now they seem quite adequate for my small room, perhaps to my listening levels...

Sooo many questions. I thank you all in advance, because there will be likely more .

Peace.

 

[JStewart]

How? That is where I am lost: That "Timing Reference" is used how? I go to REW and send this Timing Reference to the AVR? How do I do that? How does that relates to the rest of the process? I send it, how it becomes a reference? If it is not henceforth tied to all my other measurements? What am I missing?

From REW help file:
Using a timing reference allows REW to eliminate the variable propagation delays within the computer and interface so that separate measurements have the same absolute timing.

Or put another way, using a timing reference overcomes the fact that your computer sometimes thinks it has more important things to do than your REW measurement

 

[DaveBoswell]

@FrantzM just select the "Use Accoustic Timing Reference" option on the "Measure" dialog box prior to measuring (see below). You will know it is on if you hear a little chirp at the begining and the end of the sweep. The timing reference should come out of the the L or the R speaker. What many do is temporarily re-wire the the Sub Input to the L Speaker Pre-out (if you have a pre-out), disconnect the L Speaker, assign the timing reference to the R speaker, temporarily set the the L and R speakers to Large, and then Measure using the L speaker instead of the LFE. Doing this provides a scenario where the subs are presented with a full range of frequencies with no cross over / LPF applied to the subs while do raw measurements. Once done measuring all the raw measurements, set everything back to the normal setup (and don't forget to re-set the L+R to Small!!)

 

[kiwifi]

Why? Is the acoustic timing reference important in the context of two subs, not Mains + SUB integration? Want to understand what I am doing, help me refine the process for me and remember it.

The acoustic reference is used to calculated the relative delays between subs

Don't understand... Why would I run XT32 with the subs turned off? My process would have been to massage the subs via MSO. Obtain a super-smooth, super flat subwoofer in the room from 15 to 200 Hz, and present this "ultra sub" to Audyssey to integrate it with the mains? Again What am I missing?

Turning off the subs but telling XT32 that you want to measure one, triggers the XT32 screen that allows you to setup the volume levels. Once you are in that screen you power up the subs one by one and set the levels.

That would mean what? -12 dB with respect to the max sub output or ??? I understand that the MSO filters are a combination of, in my case , mostly cuts and some positive gains, not much more than 3 dB in my case, since my subwoofers, so far are cheap and with a 150 watts. I will upgrade to better subs, for now they seem quite adequate for my small room, perhaps to my listening levels...

It is relative to the max input to the DSP without clipping, which is 0dB. By adding -12dB of digital attenuation to the DSP outputs before you start, you have 12dB of headroom to add your digital gains from MSO. Digital clipping can occur when a 0dB input, results in a greater that 0bB output.

 

[kiwifi]

Hopefully this will provide some inspiration for those still on their MSO journey...

Here are the measured results of my latest subwoofer optimization using MSO. For mesurements the REW test signal (from a Motu M4) is fed directly into the DSP (a pair of QSC DSP-4) and the output is measured at the MLP using a Behringer ECM8000.



I have four subs, as listed in my signature. They are randomly, rather than symetrically distributed around the room and are also at different heights, where possible. Despite this the "after MSO" result looks considerably better than the "before", and sounds better too!

The "after MSO" response is what Audyssey XT32 will see when the input to the DSP is connected to the Sub 1 out from the AVR.

FYI: In MSO I am using five shared (input) PEQ filters limited to +0 -12dB gain, plus 3 x PEQ per sub (output) limited to +0 -6dB gain. No stacking.
I have added a 160Hz Butterworth LPF at the input to the DSP and MSO attempts a fit to that curve across the full measured frequency (10 - 240Hz)

 

[zeismoebner]

@andyc56​

Thank you for your fantastic work and inspiration.
You helped me get a lot closer to audio nirvana. I learned that a tidy basement is very important for the entire spectrum and enjoyment of music.
How can we show our appreciation?
How can we at least buy you a coffee?

 

[Badbruno]

Hello MSO users, I new with MSO and have 3 subs I'm integrating into my 2 Channel active 4-way system. Im using a miniDsp HD. Im using REW with Earthworks M23 mic with Focusrite Scarlett. Im only interested in One listening position, some questions I would like to ask to the team here:

1. I would like to print MSO User Guide, has anyone located a PDF file?

2. After MSO creates the PEQs for the three channels, I import them as 96khz txt files. miniDsp imports the biquad files in the advanced section. Is there a method to check the data which was imported in normal human terminology, (freq, gain, Q) so I can compare them to the table in MSO?

3/. Why don't we take measurements in REW at 96khz?

4/. I start with the std 75 db reference level, then run and optimization using * As flat as possible at all listening position ( only have one MLP). I then look over the the Performance report, and look at the Overall Metrics For Configuration and see that I have a 7db Weighted SPL penalty. So should I "add the difference and raise the 75db ref level (75 + 7db) to 82db new reference level?


Thank you Andy this is great software !

thank you everyone for the guidance

Badbruno

 

[Onetrack97]

Hello MSO users, I new with MSO and have 3 subs I'm integrating into my 2 Channel active 4-way system. Im using a miniDsp HD. Im using REW with Earthworks M23 mic with Focusrite Scarlett. Im only interested in One listening position, some questions I would like to ask to the team here:

1. I would like to print MSO User Guide, has anyone located a PDF file?

2. After MSO creates the PEQs for the three channels, I import them as 96khz txt files. miniDsp imports the biquad files in the advanced section. Is there a method to check the data which was imported in normal human terminology, (freq, gain, Q) so I can compare them to the table in MSO?

3/. Why don't we take measurements in REW at 96khz?

4/. I start with the std 75 db reference level, then run and optimization using * As flat as possible at all listening position ( only have one MLP). I then look over the the Performance report, and look at the Overall Metrics For Configuration and see that I have a 7db Weighted SPL penalty. So should I "add the difference and raise the 75db ref level (75 + 7db) to 82db new reference level?


Thank you Andy this is great software !

thank you everyone for the guidance

Badbruno

Back in 2018 when I was using MSO, Andy did have a PDF linked. I didn’t see one for the new 2.0 version.

Go ask your questions on AvsForum:

https://www.avsforum.com/threads/optimizing-subwoofers-and-integration-with-mains-multi-sub-optimizer.2103074

He monitors that forum closely.

 

[Badbruno]

Hello MSO users, I new with MSO and have 3 subs I'm integrating into my 2 Channel active 4-way system. Im using a miniDsp HD. Im using REW with Earthworks M23 mic with Focusrite Scarlett. Im only interested in One listening position, some questions I would like to ask to the team here:

1. I would like to print MSO User Guide, has anyone located a PDF file?

2. After MSO creates the PEQs for the three channels, I import them as 96khz txt files. miniDsp imports the biquad files in the advanced section. Is there a method to check the data which was imported in normal human terminology, (freq, gain, Q) so I can compare them to the table in MSO?

3/. Why don't we take measurements in REW at 96khz?

4/. I start with the std 75 db reference level, then run and optimization using * As flat as possible at all listening position ( only have one MLP). I then look over the the Performance report, and look at the Overall Metrics For Configuration and see that I have a 7db Weighted SPL penalty. So should I "add the difference and raise the 75db ref level (75 + 7db) to 82db new reference level?


Thank you Andy this is great software !

thank you everyone for the guidance

Badbruno

Back in 2018 when I was using MSO, Andy did have a PDF linked. I didn’t see one for the new 2.0 version.

Go ask your questions on AvsForum:

https://www.avsforum.com/threads/optimizing-subwoofers-and-integration-with-mains-multi-sub-optimizer.2103074

He monitors that forum closely.

Thank you OneTrack a great reference

 

[scotchrocks]

Now that MSO has been updated to version 2.0, it now has a multi-stage optimization type that attempts to maximize SPL while optimizing bass response and seat to seat bass variation. This is incredibly useful, as before, MSO could aggressively EQ/align subs at the cost of overall SPL capabilities (SPL penalty), or have subs work much less/more relative to each other, wasting headroom.

In v.2, it calculates the max SPL capability of the system and tries to limit the optimization settings to stay within certain SPL costs. This gives an upper bound to how much SPL you may be losing by running MSO, and it lets you quantify it alongside main listening position (MLP) and seat to seat variation (STSV) targets. So, you can effectively compare the results of different optimization options, like:

	MLP Target Error (dB)	STS Variation Error (dB)	SPL Penalty (dB) (e.g. SPL Cost)
Config 1	1.26	2.25	5.48
Config 2	3.61	2.52	5.69
Config 3	2.20	2.74	3.52

Here, Config 1 has the best target error, but the SPL penalty is 5.48 dB; Config 2 is the worst of the bunch with the highest MLP error and SPL penalty; Config 3 has middling MLP target error but the least SPL penalty. As the user, you can then pick the best option for your use case/preferences. If there is a certain frequency range you are most concerned about (maybe due to your crossover settings), you can also have the optimizations run to a frequency range (e.g. 10-200 Hz, 15-160 Hz). Narrowing the ranges may also better the results since you can apply your DSP filters within a smaller range.

Since I upgraded my speakers recently, I decided to also re-calibrate the subs with v.2 of MSO, and it has significantly improved the bass response over my v.1 results. Here's what I used:

• UMIK 2 mic
• 3 Subwoofers (SVS PC-4000, PC12-Plus)
• miniDSP 2x4HD
• Marantz SR7012

The nice thing is that once you've positioned your subs, you only need to take measurements once (in my case 9 measurements for 3 listening positions x 3 subs). After that, you can just re-simulate things in MSO and load the filters into the miniDSP unit. I did have a couple hiccups with the miniDSP unit with the Marantz receiver that I wanted to note for people using it:

• By default, the input for the 2x4HD is set to accept 2V max. However, the LFE output from the Marantz was pushing beyond that, clipping the input signal. At first, I didn't know that it was input clipping during loud bass scenes, as I thought it was my subs running out of steam, but in fact it was the 2V input clipping. I confirmed this by setting the sub gain very low, which in the same scenes, still had (quiet) clipping.
• To fix this, I switched the internal jumper to accept 4V max. I would recommend anyone running the 2x4HD to use 4V max, although it doesn't appear to be recommended anywhere to do so. This fixed the input clipping regardless of the receiver volume.
• Also, I had to keep the miniDSP gains at 0 for the input and three channel outputs. Initially, I tried to increase the sub volume by adjusting these gain values (since the MSO filters were significantly cutting bass frequencies), but this caused output clipping. Keeping everything at 0 worked fine with no clipping. For some configurations, the sub volume level was detected as too low by Audyssey, so if additional volume is needed, you can use a combination of two options:
  • Adjust the MSO General Options > fixed reference level target: this should be set higher if you want higher output from the filters (e.g. change 75 dB to 95dB). However, it may worsen your optimization results, so experimenting with it may help.
  • Adjust the gain on your subs: You can of course increase the gain on the subs, but in some cases, you may not be able to increase it any further. In that case, you should adjust the MSO target reference level.
• When loading the miniDSP filters, I had to use the menu to load the text file directly using the file browser. Don't try to copy the text into the biquad text input as it won't load properly.

After re-calibrating everything with MSO and re-running Audyssey up to 500 Hz, things are sounding very, very good. There is a ton of LFE output now that MSO preserved in v.2, to the point where I'm needing to turn sub levels down a bit. I think if anyone has an MSO setup running under v.1 and hasn't touched it in a while (like me), it's very much worth re-running things under v.2 to see how it might improve things. I was curious to try Dirac DLBC on a new receiver, but now I think that can wait a bit.

 

[ThELiZ]

Now that MSO has been updated to version 2.0, it now has a multi-stage optimization type that attempts to maximize SPL while optimizing bass response and seat to seat bass variation. This is incredibly useful, as before, MSO could aggressively EQ/align subs at the cost of overall SPL capabilities (SPL penalty), or have subs work much less/more relative to each other, wasting headroom.

In v.2, it calculates the max SPL capability of the system and tries to limit the optimization settings to stay within certain SPL costs. This gives an upper bound to how much SPL you may be losing by running MSO, and it lets you quantify it alongside main listening position (MLP) and seat to seat variation (STSV) targets. So, you can effectively compare the results of different optimization options, like:

	MLP Target Error (dB)	STS Variation Error (dB)	SPL Penalty (dB) (e.g. SPL Cost)
Config 1	1.26	2.25	5.48
Config 2	3.61	2.52	5.69
Config 3	2.20	2.74	3.52

Here, Config 1 has the best target error, but the SPL penalty is 5.48 dB; Config 2 is the worst of the bunch with the highest MLP error and SPL penalty; Config 3 has middling MLP target error but the least SPL penalty. As the user, you can then pick the best option for your use case/preferences. If there is a certain frequency range you are most concerned about (maybe due to your crossover settings), you can also have the optimizations run to a frequency range (e.g. 10-200 Hz, 15-160 Hz). Narrowing the ranges may also better the results since you can apply your DSP filters within a smaller range.

Since I upgraded my speakers recently, I decided to also re-calibrate the subs with v.2 of MSO, and it has significantly improved the bass response over my v.1 results. Here's what I used:

• UMIK 2 mic
• 3 Subwoofers (SVS PC-4000, PC12-Plus)
• miniDSP 2x4HD
• Marantz SR7012

The nice thing is that once you've positioned your subs, you only need to take measurements once (in my case 9 measurements for 3 listening positions x 3 subs). After that, you can just re-simulate things in MSO and load the filters into the miniDSP unit. I did have a couple hiccups with the miniDSP unit with the Marantz receiver that I wanted to note for people using it:

• By default, the input for the 2x4HD is set to accept 2V max. However, the LFE output from the Marantz was pushing beyond that, clipping the input signal. At first, I didn't know that it was input clipping during loud bass scenes, as I thought it was my subs running out of steam, but in fact it was the 2V input clipping. I confirmed this by setting the sub gain very low, which in the same scenes, still had (quiet) clipping.
• To fix this, I switched the internal jumper to accept 4V max. I would recommend anyone running the 2x4HD to use 4V max, although it doesn't appear to be recommended anywhere to do so. This fixed the input clipping regardless of the receiver volume.
• Also, I had to keep the miniDSP gains at 0 for the input and three channel outputs. Initially, I tried to increase the sub volume by adjusting these gain values (since the MSO filters were significantly cutting bass frequencies), but this caused output clipping. Keeping everything at 0 worked fine with no clipping. For some configurations, the sub volume level was detected as too low by Audyssey, so if additional volume is needed, you can use a combination of two options:
  • Adjust the MSO General Options > fixed reference level target: this should be set higher if you want higher output from the filters (e.g. change 75 dB to 95dB). However, it may worsen your optimization results, so experimenting with it may help.
  • Adjust the gain on your subs: You can of course increase the gain on the subs, but in some cases, you may not be able to increase it any further. In that case, you should adjust the MSO target reference level.
• When loading the miniDSP filters, I had to use the menu to load the text file directly using the file browser. Don't try to copy the text into the biquad text input as it won't load properly.

After re-calibrating everything with MSO and re-running Audyssey up to 500 Hz, things are sounding very, very good. There is a ton of LFE output now that MSO preserved in v.2, to the point where I'm needing to turn sub levels down a bit. I think if anyone has an MSO setup running under v.1 and hasn't touched it in a while (like me), it's very much worth re-running things under v.2 to see how it might improve things. I was curious to try Dirac DLBC on a new receiver, but now I think that can wait a bit.

This is great info. Thank you.

With regards to changing the input voltage, is this done on the 4xHD? Is there any issue with doing this?

I get clipping on my subs during loud LFE scenes when the amp is up loud. Maybe this is my issue.

 

[ThELiZ]

This is great info. Thank you.

With regards to changing the input voltage, is this done on the 4xHD? Is there any issue with doing this?

I get clipping on my subs during loud LFE scenes when the amp is up loud. Maybe this is my issue. I’m using Denon x4700H.

 

[scotchrocks]

This is great info. Thank you.

With regards to changing the input voltage, is this done on the 4xHD? Is there any issue with doing this?

I get clipping on my subs during loud LFE scenes when the amp is up loud. Maybe this is my issue.

Yes, this is done directly on the 2x4HD. It's very easy to do; just remove a couple of screws and change the jumper setting: https://docs.minidsp.com/product-manuals/2x4-hd/additional-information/input-jumpers.html

Edit: I think the only real difference is that the level may be attenuated by -6 dB since the input signal voltage range is now doubled. So, things may be quieter on the output end and you might need to raise gain levels on your sub to compensate (or increase your MSO target reference level).

Also, if you have any gain on the input or output channels, I would highly recommend those to be reset to 0 (or negative). Any positive gain caused clipping for me. Hope it resolves your clipping issues.

The torture test scenes I used to detect clipping were the Blade Runner 2049 opening scene and the Interstellar wormhole scene. I specifically turned the sub gain all the way down (-60 dB) and turned the amp to 0 dB reference level to check if I could hear the clipping sound. If you can hear it (should be very quiet), then it's clipping on the miniDSP end and not your subwoofer. Of course, my mains/surrounds were turned off/disconnected during these tests.

 

[Jost Buergi]

I have newbie question regarding the DSP device between AVR and subs. Let's assume we have an AVR (Denon), 1 subwoofer behind the Front Left speaker and 1 behind Front Right. That's a total of 2 subs with equal distance to the MLP. However, no room symmetrical placement of speakers / subs and no "symmetrical" room as well (L shaped). Let's also assume the subs have onboard parametric EQ's and maybe a polarity switch or phase dial.

As the subs are equidistant and EQ's already available I am wondering if an external DSP would still be mandatory for using MSO. If so, why?

 

[Willem]

Those subs would have a more basic functionality, with just filters, and usually only a few of them. Would that work? I don't know. I have a somewhat similar question. I am using MSO and a miniDSP 2x4HD for my three or perhaps later four subs, but I would like to equalize the 80-200 Hz range of my highpassed main speakers as well. I can use the filters on my RME ADI-2 for that, but first, those would also affect the response of the already equalized subwoofers, and they would also be more basic. Or would I do better to simply equalize the subs with MSO, and subsequently use REW to design a few filters for the range of about 80-200 Hz, and implement those on the ADI-2, and separately for each of the two main speakers?

 

[scotchrocks]

I have newbie question regarding the DSP device between AVR and subs. Let's assume we have an AVR (Denon), 1 subwoofer behind the Front Left speaker and 1 behind Front Right. That's a total of 2 subs with equal distance to the MLP. However, no room symmetrical placement of speakers / subs and no "symmetrical" room as well (L shaped). Let's also assume the subs have onboard parametric EQ's and maybe a polarity switch or phase dial.

As the subs are equidistant and EQ's already available I am wondering if an external DSP would still be mandatory for using MSO. If so, why?

MSO has options for setting the number of parametric EQs available (default is 8) so you could theoretically limit the PEQs that are used in optimization to what you have in your subs. You would also need to set delays as well for the subs, which I'm not sure can be done directly in the AVR aside from maybe changing the distance parameters to simulate the delay. You also lose the ability to configure shared PEQs, which can hurt the amount of improvement you'd get. It might be possible to configure MSO with those limitations and see what you get.

I think if you're on the fence, I'd recommend taking the REW measurements for your two subs and seating positions and running it through MSO to see what results you get. You could compare different configurations: some with the full functionality of the miniDSP, and others being limited to what you have available via the AVR and built-in sub PEQs. Based on that, you can decide if it's worth it to get the external DSP.

One thing is that the miniDSP makes it easy to export the PEQ settings from MSO and import them in, so you're not messing with PEQs on the sub. That sounds like a headache to do individually for each sub.