Using Multi Subs & MSO To Get Even Bass In Room & Across Sitting Positions

[Guest]

Introduction

The purpose of this post is to re-introduce a software tool that configures multiple subwoofers (subs) to produce smooth bass in a room and at the same time, make it even across sitting positions.  A common misconception of adding subs for music is that they will artificially boost the bass.  Well integrated subs help restore the missing bass caused by the room and brings the body back to music.

 

The usual approach to managing bass was room treatment first, followed by careful placement of speakers & subs. Hardware and/or software, often expensive, were also used. This case study shows why MSO is a good cost-effective software option.

 

What is MSO?

Multi-Sub Optimiser (MSO) is a FREE software tool to optimize multiple sub woofers by integrating the subs with main speakers and improving the evenness of bass response across the whole listening area. MSO is especially useful in non-dedicated rooms where there is limited (or no?) room treatment and WAF considerations dictate sub size, number and placements.  MSO also solves the difficult task of getting even bass across seating positions e.g. in multi row home theatres.

 

MSO runs on a Windows laptop and requires a digital signal processor (DSP) and a calibrated microphone for use with REW (Room Equalisation Wizard) measurement software. There is some learning effort and time required to understand the concepts and set up the optimisation, but the results are worth it!  There is excellent documentation and a good tutorial.

 

The program was written by AndyC on AVS Forum (discussion thread hosts all discussions, support, bugs etc.). Andy @andyc56 specifically joined SNA to support MSO.

 

Why MSO? – A Case Study

2 channel system was located in a non-dedicated open plan family room with high ceiling, hardwood floor on slab, blank wall in front, large windows with blinds on right, sliding glass doors with heavy curtains behind, left side opened to kitchen.  Thick rug, cushions and sofas (with some sound absorbing foam underneath) completed the “room treatment”.

 

 

 

Main speakers were a pair of active SGR CX3Bs (Mk 1) and the measurements showed how good the speakers were by themselves. However, the room muddied the bass and there was less body in the music.

 

 

Listening positions were in a single row with the main listening position (MLP) in the centre. Right4 was better half’s favourite spot and depending on how far she stretched her legs on the sofa, Left2 became a regular listening spot!   Left1 opened out to kitchen. The middle positions Left 2 and Right 3 graphs were offset -15 dB to improve readability.  Similarly,  outside positions Left 1 & Right4 offset -30 dB for readability.

 

 

 

Subs were SVS SB13U and SB2000, located using “thirds criteria” in the front.  The room had limited options for subs placement and WAF considerations further restricted things. The unintegrated subs  (no adjustments to phasing, no eq, no cross over etc.)  made things  worse between 65 and 90 Hz.

 

 

MSO used gains, delays, cross overs and PEQs to optimise the subs. Weightings for seating positions were Left1=0.5, Left2=0.9, MLP=1.0, Right4=0.8, Right5=0.5.  A target curve was used to lift the bass and compensate for large and open room.  

 

 

Bass was even across 20 to 90 Hz and the dips were removed.  More impressive was the evenness across listening positions, even in Left1.  Right4’s improvement was under appreciated (everything was treated as muzak! SIGH!).  The graphs showed that excellent results could be achieved with dual subs and MSO, but what about listening tests?

 

 

Using a SoTM SMS-200 Ultra network player and a Gieseler Groß DAC, Diana Krall’s My Love (double bass), Bach’s Tocatta & Fugue (organ) and Fleetwood Mac’s Dreams (drums) showed how good the bass was.  MSO brought the body back to the music and was probably the key enabler for further improving the 2 channel setup. Without MSO, I doubt I would have appreciated and enjoyed the Groß DAC as much.

 

 

While this was 2 channel focused, MSO was also good for the home theatre. Using a different subs-only configuration, MSO took movies up a notch with additional slam on Anthem MRX 710 setup in same room. It made my favourite movie opening scene in Fellowship of the Rings superb. Was (and still am) no bass head, but understood why so many pursue this!

 

 

SNA Reviews & Impressions

There were at least 2 threads on MSO in the Room Acoustics, Construction and Design sub-forum.  Below were the reviews and impressions posted by members (will update if there are more posts):

baMarek  8 Sep 16

BradC 22 Nov 16

mcb 23 Apr 17

Snoopy8 5 Jun 17

 

 

 

Conclusion

 

This case study has shown that MSO is a good cost-effective software option to overcome the bass issues brought about by the room.  Hopefully, some here will try it for your setup.  And more than happy to assist you in your journey.

 

 

 

 

 

Edited May 17, 2018 by Snoopy8
Updated graphs, changes to text to reflect current situation

[frednork]

Thanks for that, I havent heard of it. A couple of questions.

 

To achieve your result do you need to be running MSO to modify the signal?

 

Could you just do this on the bass of your speakers? ie no subwoofers to get similar effect

 

[Mike13]

Good article. I’ll post my results when I work it out. Doesn’t it work with Mac too?

[Guest]

46 minutes ago, frednork said:

Thanks for that, I havent heard of it. A couple of questions.

 

To achieve your result do you need to be running MSO to modify the signal?

 

Could you just do this on the bass of your speakers? ie no subwoofers to get similar effect

MSO is not widely known, hence this post. 

 

MSO imports REW measurements for the mains and subs and use them to optimise. It calculates gains, delays, crossovers and parametric equalization values to be entered into a DSP. These are for the subs, mains are not touched. It is the DSP which manages the subs' signal.

 

MSO requires a minimum of 2 subs. There is complicated mathematics behind it for the subs to "fill in"  for the mains, thus giving a smoother bass response. This is a highly simplified description. For a more detailed description, see start of tutorial.

 

Hope this answers your questions..

4 minutes ago, Mike13 said:

Good article. I’ll post my results when I work it out. Doesn’t it work with Mac too?

Whoa!  Got you too inspired! . Still have quite a long way to go and we need to confirm that your subs can do the job.

 

Sorry, Windows only, you will need to run Win emulation or borrow a Win laptop.

 

 

[Mike13]

Realised two important things tonight while testing out a super high quality DAC (Gieseler Gross), thanks Clay@Gieseler Audio. 

 

1) I need to fix my bass, i now understand my two subs are muddying the music, but some songs just sound thin without added bass and this isn’t the speakers. 

 

2) my Hulgich speakers have ridiculous amounts of bass for newer songs by themselves and sound awesome. 

[almikel]

Hi Snoop,

what DSP do you use?

 

Mike

[Guest]

19 minutes ago, almikel said:

Hi Snoop,

what DSP do you use?

 

Mike

Behringer DCX2496 with Behringer Mods which improved the input and output stages significantly.

[Guest]

Have managed to further improve the bass response using a target curve (see bottom of Reference manual: page 13) 

 

The inspiration for this target curve came from this post:

 

MSO result using above target curve.  MLP is main listening position, L4, L3, R2, R1 are positions on sofa to left, right of MLP.

 

 

The results are very good, with the kick drum becoming tighter, and now with a snap.  Interestingly, had to reduce the boost in the bass region of the target curve because the tapering off of the bass was so effective.  Note that you may need to experiment with the target curve to suit your room.

 

Hope this helps you in your MSO journey.

[Mike13]

Nice flat curve there @Snoopy8

[andyc56]

On 11/12/2018 at 5:25 AM, Snoopy8 said:

Have managed to further improve the bass response using a target curve (see bottom of Reference manual: page 13) 

 

The inspiration for this target curve came from this post:

 

Just as an FYI, the target curve in that downloadable project in the MSO documentation you referenced came from an article by Sean Olive, Todd Welti, and Elisabeth McMullin from Harman.  The article is called "Listener Preferences for In-Room Loudspeaker and Headphone Target Responses" and can be found here.  Todd Welti discusses that article and other subjects here.

[Guest]

Thank you @andyc56 for your continuing support even though we have relatively few users here.

 

I am still amazed at how well MSO does the job. The better half was wondering why I was spending so much time looking at squiggles on the laptop!   

 

MSO has allowed me to overcome many of the limitations of putting a decent system in a large open plan family room. It has stopped the need to get more subs (dual subs was at WAF limit!). 

[davewantsmoore]

On 11/12/2018 at 10:25 PM, Snoopy8 said:

target curve

What is the purpose of the -20dB @ 20Hz target?   Is your system really small?! (sorry I didn't read back)

 

How come you only achieve -10dB @ 20Hz in the measured result?

[Guest]

57 minutes ago, davewantsmoore said:

What is the purpose of the -20dB @ 20Hz target?   Is your system really small?! (sorry I didn't read back)

Naughty!  If you had read back, you will see that the target curve was inspired by this post:

 

1 hour ago, davewantsmoore said:

How come you only achieve -10dB @ 20Hz in the measured result?

Good pickup!  I had default limits on the MSO filters which I could have lowered to push the calculated (not measured) results down.  I may yet try that.

[Guest]

This post is no longer relevant because of flawed thinking.  It is not possible to keep 2 USB DACs in synch because both DACs are operating asynchronously.  The DACS will drift over time. Have used strike through on text and removed the diagram so that people are not misled.

 

After a year’s absence and 2 setup changes, decided to use MSO to integrate dual subs with the Kii Three (see thread).

 

The measuring process for MSO involved measuring the mains together and individual subs, at the main listening position and to left and right.  Usually, measuring involved using a DAC’s USB port, but with dual USB outputs, had to use REW’s file measuring capability.   The setup was configured this way for measuring:

 

 

 

 

The measurement of the results showed a good match to the theoretical curve.  It confirmed that MSO process was done properly and the DSP parameters were entered correctly.

 

There was a noticeable difference in the SQ, with more body at normal listening levels. Without the subs, the bass was “more polite”.  At higher listening levels, the bass response became even better, and you can even feel it. I had the bass that I wanted that further improved the already excellent SQ of the Kii Three.

  

Edited April 21, 2021 by Snoopy8
Post no longer relevant

[WasM]

Did you optimise for MLP only or more?

What DSP unit are you using and does it allow timing alignment?

[Guest]

47 minutes ago, WasM said:

Did you optimise for MLP only or more?

What DSP unit are you using and does it allow timing alignment?

MSO requires a minimum of 3 positions for dual subs, and MLP had highest weight i.e. importance.  

 

Using a Behringer DCX2496, will work with MiniDSP 2x4HD and other DSPs.

 

MSO uses a number of different DSP parameters including gain, delay, low pass filter and PEQs.  So, yes to time alignment.

 

One thing to note is MSO does not touch the mains, and only applies DSP to the subs. A very simplistic way to describe it is that MSO "fills the bass troughs".

 

 

[WasM]

I've got two SVS subs and been using the in-built DSP to input the filters. 

Results have been very good with 4 of the 8 positions improving, with the MLP aligning with the sliding tilt target response

Been thinking if its worthwhile getting a dedicated DSP to:

• Set different DSP modes - Cinema, Music, Live
• Buy external DAC with bypass for cinema

[Guest]

26 minutes ago, WasM said:

I've got two SVS subs and been using the in-built DSP to input the filters. 

Results have been very good with 4 of the 8 positions improving, with the MLP aligning with the sliding tilt target response

Been thinking if its worthwhile getting a dedicated DSP to:

• Set different DSP modes - Cinema, Music, Live
• Buy external DAC with bypass for cinema

If you are looking for even bass over different seating positions, MSO is the way to go.  Am using it on its own  with stereo setup and with Dirac Live (MSO sub only option) for HT.  Your different modes may be achievable with different target curves, but I need more info.

 

Don't use understand what you mean by external DAC. Please describe your setup in more detail.

[WasM]

PM sent, thought it best to keep this focused on MSO than setups.

[Satanica]

@Snoopy8 I thought I would ask you a question or two regarding MSO and your setup(s) here rather than in the Kii THREE thread.

 

In that thread you said: "MSO works not only in lower bass, but up to 200 Hz.".

So you've EQ'd your subwoofers with MSO from 0 to 200Hz?

How are you running your sub(s) i.e. do you have a low pass filter on them?

Edited April 1, 2021 by Satanica

[Satanica]

In the Kii THREE thread you also said: "I can use different target curves and store various profiles in the DSP.".

So can you specify subwoofer(s) target curves with MSO?

My assumption was that it has a fixed target curve of flat.

If you can actually specify a target curve with MSO then I assume it would only be for the subwoofer(s) and not the mains.

And the way I also see it is any low pass filters will limit the range of the target curve(s) effectiveness.

Or maybe I'm not understanding this correctly.

Edited April 1, 2021 by Satanica

[Guest]

MSO takes a very different approach. Have a look at the picture on this page of online doc (which is excellent)

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

 

For each sub, you define a number of filters, gain, delay, PEQS, low pass filters. MSO then runs through a process of adjusting these filters so that each of the subs "fill in the bass troughs of the mains".  It is my simplistic way to describe how MSO work.  The maths is complicated and beyond my understanding.  By I do know the results are good.

 

Probably the best way to learn is to go through the online tutorial which has an example you can work with.  It will be difficult process but if you persist, it will make sense eventually.  Once you do a bit of online reading, you can look at the different strategies, including using the subs only option to integrate the subs before running Dirac Live.

 

You can set target curves here (lower down in page) and can even generate accurate target curves.

 

Enough for the time being; there is a lot to swallow...

[Satanica]

I've had a bit of a read and from what I can gather you are using MSO with a Geddes style optimisation strategy where the mains are run full range and subwoofer(s) are potentially run with a considerably wider range than conventional approaches.

[Guest]

1 hour ago, Satanica said:

I've had a bit of a read and from what I can gather you are using MSO with a Geddes style optimisation strategy where the mains are run full range and subwoofer(s) are potentially run with a considerably wider range than conventional approaches.

Correct.

 

----

I have used MSO on a separate DSP with Dirac Live on another box, but never in the same box.  Can the SHD Studio do both Dirac Live and apply MSO filters at the same time? 

 

** Also, can Dirac Live measure the subs with MSO filters applied?

Edited April 1, 2021 by Snoopy8
Added **

[Satanica]

5 hours ago, Snoopy8 said:

Correct.

 

I finally get it, the penny has dropped.

 

5 hours ago, Snoopy8 said:

Can the SHD Studio do both Dirac Live and apply MSO filters at the same time?

 

You can have seperate PEQ's, gains, delays etc outside of Dirac that can be set in the SHD although I don't know if you can import those settings into the SHD series from REW or MSO.

I assume you can import them into the Beringher 2496 (which you have and are doing) or potentially other miniDSP units and one would need one of these or equivalent anyway for D/A conversion and long delays for the subwoofer(s) if required. The SHD series can only delay by a maximum of 30ms which I know is not enough for the Kii THREE's. I have a MiniDSP OpenDRC DA8 which can apply much longer delays even though I don't need much.

 

5 hours ago, Snoopy8 said:

Also, can Dirac Live measure the subs with MSO filters applied?

 

Well as per above if you measured with REW and then ran MSO and then exported and imported into a Behringer or miniDSP or eqivalent unit and then ran Dirac over the Left and Right Speakers with subwoofer(s) on and working with them I can't see right now at least why not.

Edited April 1, 2021 by Satanica