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Review of Multi-Sub Optimizer

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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. The program was written by AndyC on AVS Forum (discussion thread hosts all discussions, support, bugs etc.)

The documentation states that MSO gives the best results with three or more subs but with two subs, the improvement may be limited. However, good results were obtained in my environment using 2 dissimilar subs.

Ideally, you should be familiar with REW and have a calibrated mic. And a digital signal processor (DSP) is required.


An open plan family room, with limited room treatments (curtains, as much soft material as can be sneaked in!) and very limited choices for placement of speakers and subs. WAF considerations preclude further room treatments.

MSO for Stereo

Stereo was previously running as a 2.1 system using a SVS SB13U sub. After adding a second smaller SVS SB2000 sub and applying the MSO filters, the bass came across tighter and more controlled in the main listening position (MLP).  Even positions to the left and right of MLP are much better than before.

The stereo setup has improved significantly; am (re)discovering the bass in my music library!  :wub:

MSO for Home Theatre

Currently using Anthem Room Correction (ARC) for HT audio and multi-channel music.  However, ARC cannot compensate for spatial variation between seating.

The previous 5.1 setup used the SB13U.   The new 5.2 setup, with the addition of the SB2000 and MSO, gave a noticeable better bass response for movies. MSO+ARC did an excellent job of integrating the subs, better than ARC alone. What was impressive was the evenness of bass response across the listening area.

For multi-channel music, tracks which had a significant amount of bass came across better with MSO.  And more uniform bass across the different listening positions.


MSO is a free, easy-to-use tool to optimise multiple subs. MSO with 2 subs has significantly improved my stereo setup and movies, and to a lesser extent multi-channel music.  What is impressive is the evenness of bass response across the listening area.  Delighted with this upgrade of a second sub and MSO. :D

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    • By Snoopy8

      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, graph offset -15 dB to improve readability.  Similarly, Right3 & 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 arguably made things  worse, e.g. dips beyond 100 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=0.7, Right5=0.5.

      Bass was even across 20 to 90 Hz and the dips between 100 and 200 Hz 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 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


      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.