Optimizing subwoofers and integration with mains: multi sub optimizer

The_Forth_Man said:

Hi guys, what I'm about to ask as probably been answered before but I just want to be sure I won't blow anything up.
I usually find my own answers but I've read and watch so much video's about sound theory that my head is spinning. I fear that I need someone to hold my hand on this one.

(I can start my own thread if it's the preferred approach. Just tell me.)

Quick recap 3 years ago after too much spending on my HT I decided to be satisfied and live with it as is. A month agodays I only had my two mismatched subs eq'd by Audysey XT32 but I "Found a great deal" on some Buttkickers LFE I wanted 3 years ago. Forward to know the great deal as become quite the expense and the headache.

I Found out that my old 1000w class AB amp had died in storage So Bought a new one (Inuke 6000dsp) for the kickers.

Then I read that I would be better to feed a clean signal (non-audyssey EQ) to the transducers so I bought a Umik-1. Then I read about BEQ so I bough a MiniDSP HD. Then took some REW measurements only to find out that I had a 10db cut at 57hz at MLP plus some other variations. I fiddled for two weeks to finally get the best result by switching both sub with one another, no our drop around 60hz. While looking at how to set up REW on a Mac I found Jeff Mery's tutorial and decided to try MSO. After taking more measurement I found out that my STSV was very bad and I've been trying a lot of thing in the past week.

After running Sims for a week I ended up with one I though looked good compared to what I had. I specified no boost but looking at the filter's report I see that it as a 15db GAIN block. I'm afraid that my subs won't handle it.

Sub 1 is tuned at 30hz and sub2 at 35hz if that matters. Should I optimize higher and use the transducer to fill the gap?

Click to expand...

As always, good advice from Andy above, but a few things to add ...

In the original measurements, it's clear that your subs are falling off rapidly below their tuning frequencies. You do NOT want to ask a ported sub to produce meaningful SPL below its tuning frequency. That greatly increases the risk of physically damaging the driver.

I would recommend changing the lower limit of your optimization range to 35Hz (limit of the "weaker" sub in this regard). The upper limit stays the same (or could be increased if desired). Be sure to change the "PEQ Parameter Limits" values for the Min and Max Center Frequency to match the new optimization range. You would do this AFTER addressing the measurement issues noted by Andy. Here's a video on taking measurements for MSO using REW. It's shown on the Mac but the process is the same on Windows. (Disclaimer: Those are my videos, but you already mentioned watching them so I don't feel awkward point you at another one.)

Use the Buttkickers to cover the frequencies below 35 Hz. You can run all of this off the miniDSP. Route the input signal to all three outputs (2 subs, 1 buttkicker). MSO filters will go on the output side for just the 2 sub outputs. The output side for the Buttkickers will need a low-pass filter to keep them from playing above 30-35 Hz. I'm not sure what slope is recommended. However, based on the way your subs roll off, I'd probably start with a 4th-order (24 dB/octave) LR filter. You can use the gain features of the miniDSP or the iNuke to fine-tune the feel of the Buttkickers (or keep them from bottoming out if that's happening).

Blackdevil77 said:

I rearranged my rear subs and re-ran MSO today. I’ve been going at it all day, for some reason things aren’t behaving predictably. Run MSO, get a good result, input everything into my DSP and my measured results look nothing like MSOs predicted results. Maybe I should re-measure everything? I noticed the acoustic timing reference isn’t consistent when measuring. I get a different result every time I measure

Click to expand...

If you're not getting reliable measurements, the MSO results will not correspond to final measured results either. If this is indeed the case, then the problem of getting unreliable REW measurements needs to be solved. That problem is outside the scope of this thread though.

See this post and this one for the kind of accuracy (calculated vs. measured) that can be achieved.

Unfortunately, the problem of mismatch between MSO's calculated results and the final measured results is one that's very difficult to solve in a forum Q&A setting. To really track things down requires being physically present during the whole process.

Edit: These topics are now summarized in the MSO FAQ as well.

Some causes of this problem in the past have been:

• Not using an acoustic timing reference in the measurements. See this post for detailed instructions on how to set it up.
• Not using the same acoustic timing reference for all measurements
• (Edit: ) Using an acoustic timing reference whose path to the microphone may be partially obstructed in some listening positions
• (Edit: ) Attempting to use a subwoofer as an acoustic timing reference. The acoustic timing reference must be a full-range speaker.
• (Edit: ) Attempting to use a loopback timing reference with a USB microphone
• Using measurement smoothing, and/or accidentally enabling smoothing during REW measurement export. Exported measurements must not have any smoothing.
• (Edit: ) The miniDSP 2x4 non-HD devices have multiple software plugins available, and not all are compatible with multi-sub setups.
  • Do not use the 2-way advanced or 2-way advanced 2.1 plugins
  • Instead, use the 4-way advanced or 2x4 advanced plugins
  • The 4-way advanced plugin is preferred, as it allows for 6 biquads per channel and a maximum of 7.5 msec delay
  • The 2x4 advanced plugin only allows 5 biquads per channel and 7.2 msec delay.
• (Edit: ) If you're using a Mac and REW for measurements, use one with a native HDMI port when measuring HDMI devices. The use of USB-to-HDMI adapters has been shown to introduce timing errors in certain setups. See this thread for more details.
• (Edit: ) Not using a proper tripod microphone stand for measurements. Here is an example of the correct type of stand to use.
• (Edit: ) Not using vertical orientation of the microphone. The microphone vendor's 90 degree cal file must be used.
• (Edit: ) Using unconventional measurement sequences. The correct sequence is:
  • Place the microphone stand at the first listening position to be measured
  • Mute all subs except for the one to be measured
  • Measure the non-muted sub
  • Repeat for all subs at that listening position
  • Move the microphone stand to the next listening position
• Specifying an incorrect miniDSP sample rate in Tools, Application Options, Hardware. The miniDSP 2x4 HD uses a 96 kHz sample rate, while the non-HD miniDSP 2x4 devices use a 48 kHz sample rate. These MSO settings are stored in the registry, not the project, so if you switch to using another computer, double-check these settings on the second computer.
• Make sure the sample rates chosen in the Windows Sound Control Panel for the input and output sound devices are equal to one another and correct, and that the REW measurement sample rate agrees with what's been chosen in the Windows Sound Control Panel. For example:
  • The miniDSP UMIK-1 microphone uses a fixed 48 kHz sample rate. This means you must do the following:
    • Set the UMIK-1 sample rate in the Windows Sound Control Panel to 48 kHz.
    • Set the HDMI output device sample rate to 48 kHz in the Windows Sound Control Panel.
    • Set the measurement sample rate to 48 kHz in REW.
  • The sample rate of the miniDSP UMIK-2 microphone is user-adjustable. When using this microphone, do the following:
    • Set the UMIK-2 sample rate in the Windows Sound Control Panel to the desired value, say f0. A safe value for f0 is 48 kHz.
    • Some users have reported improved measurement consistency by setting the UMIK-2 buffer size to 4096 in the miniDSP UAC2 Control Panel (Start Menu -> miniDSP).
    • Set the HDMI output device sample rate to the chosen f0 in the Windows Sound Control Panel.
    • Set the measurement sample rate to the chosen f0 in REW.
• (Edit: ) Failing to manually enter the delay and attenuation values into each miniDSP channel after running MSO. Some new miniDSP users mistakenly believe that loading the exported biquad coefficients is all that's needed. Manual attenuation and delay entry into each miniDSP channel is also required.
• (Edit: ) Using delay or gain values from the MSO filters themselves, rather than the filter report. Delay blocks in MSO can contain negative delays. When you run the filter report, the final delays are shown at the end, adjusted so that no negative delays are present. A similar thing is done with gains. The filter report adjusts gain values in dB to be negative, representing an attenuation. This is to accommodate certain miniDSP models that don't allow positive gains.
• Attempting to adjust individual sub levels after optimization using sub amp analog volume controls instead of DSP hardware. After optimization, sub levels should only be adjusted in DSP hardware such as the miniDSP 2x4 HD. If your amp has internal DSP hardware as some Behringer amps do, and that's your only DSP, then that DSP's level control can and should be used.
• (Edit: ) Some miniDSP devices (like the original 2x4 devices or the 4x10) use fixed-point DSP processing, which has degraded accuracy at very low frequencies (see images showing frequency response). The 2x4 HD uses floating-point DSP, which does not have this problem.
• Mixups between MSO sub channel and miniDSP sub channel causing biquad text files to be loaded into the wrong miniDSP channel. The miniDSP channel naming feature can help with this.
• Some AVR or amplifier DSP settings failing to "take" until backing out of the screen in which they are set
• Accidentally taking measurements without first clearing out the miniDSP filters, gains, delays and polarity inversions
• (Edit: ) Accidentally taking measurements with Audyssey Dynamic EQ or Dynamic Volume on. All room correction should be disabled before measuring (except under certain very obscure circumstances).
• (Edit: ) If you get a warning about signal level for the acoustic timing reference in REW when doing a measurement, adjust signal levels until the warning goes away before performing any measurement.
• Failing to clear out the default low-pass and high-pass filters from the miniDSP crossover section before measuring
• (Edit: ) Setting "LPF for LFE" too low if measuring using HDMI channel 4, or crossover too low if measuring with a Left, Right or Center channel stimulus. These should temporarily be set to their maximum allowable values (usually 200 Hz or 250 Hz) prior to measuring for a sub-only optimization.
• (Edit: ) Measuring at too high an SPL, such that significant subwoofer distortion or room object vibrations are present. MSO does its calculations using the Superposition Principle (like a generalization of REW's "A+B" measurement processing function). The Superposition Principle assumes a linear system (see link), which means that distortion of the subs should be negligible. Try to keep typical subwoofer measurement levels at around 85 dB SPL to minimize distortion.
• (Edit: ) The results of including bass shakers and so-called "BOSS" arrangements in the measurements and optimization are likely to be invalid due to nonlinear behavior of the devices.
• (Edit: ) One user had been getting very good correspondence between MSO predictions and final results, but then made some changes to his system. The system developed a slight hum as a result of the changes, and then he began getting poor correspondence between MSO predictions and final results. The hum was interfering with the measurements, especially around 60 Hz and 120 Hz.
• (Edit: ) At the high end of the subwoofer measurement band, microphone placement repeatability can affect correspondence between MSO predictions and final measurements. If you can, measure the MLP last, then keep the microphone in place so that when you go back to verify the combined sub response after optimization, it's in the same location you used for the original measurements.
• (Edit: ) Possible changes in the acoustic environment between when the measurements for import into MSO were originally taken, and the final verification measurements after running MSO.
  • For instance, if the room is well sealed with a door, and the original measurements were taken with the door open, while the verification measurements were taken with the door closed (or vice versa), this difference in measurement conditions could cause discrepancies in the predicted vs. measured response at the lowest frequencies.

There are probably more, but these are the ones I've been able to think of so far.

I'll update this post periodically as more possibilities come to mind and more user experience is incorporated.

andyc56 said:

Your data before optimization has a lot of rolloff at the high end (above 100 Hz). You want these measurements to be as flat as you can up to about 200 Hz (along with the inevitable "hash" you'll see). This can be accomplished in several ways:

• If you are using Left, Right or Center channel inputs, temporarily set the crossover frequency as high as it will go, preferably 200 Hz or 250 Hz.
• If you are using the LFE input (HDMI channel 4 in Windows) set your AVR's "LPF of LFE" (or whatever it's called for your brand of AVR) as high as it will go, again 200-250 Hz if possible
• Many active subs have an "LFE" input that allows bypassing any internal crossover it might have. Use that if you're not currently using it.
• Any "crossover" or "LPF" function of your subs should either be disabled entirely or, failing that, set to as high a frequency as possible.
• In extreme cases, if your AVR has preamp outputs for all channels, you can temporarily connect the miniDSP to one of the front main preamp outputs, and temporarily set the corresponding speaker used to "Large" in the AVR setup. This will run the subs wide open, without any low-pass filter at all.

The idea of a "reference level" in MSO is intended to be the nominal constant level from 100 Hz to 200 Hz that you get when you run the subs wide open. If there is significant rolloff above 100 Hz, this can cause problems with MSO. A similar thing happened to user Conrad Nash a couple of weeks ago. See this post and the posts before and after it for more discussion.

Once that problem is solved, we can talk about getting the most appropriate gain settings. This topic is also discussed in detail in the Fixing the Sub Gain Mismatch topic of the tutorial. It involves using the "Normalize Gains" command after the first optimization. This separates the gain problem into common gain and relative sub gains. Then you constrain the relative sub gains to prevent them from being widely disparate, and re-run the optimization with these new constraints. The picture below shows how to use the Filter Properties Window to adjust filter parameter limits.

View attachment 3202694

Oddly, the gain block representing the overall level of the subs gets ignored, as this function is taken over by your AVR's sub trim level, used only for integrating subs and main speakers. This is discussed in the Why Specify a Reference Level if We're Just Going to Throw it Away? tutorial topic.

I'm not sure what to say about the transducers. Being a two-channel guy, I have no experience with them. My gut feel is that they should not be included in any MSO optimization at all. Maybe others with transducer experience can chime in.

Click to expand...

fattire said:

As always, good advice from Andy above, but a few things to add ...

In the original measurements, it's clear that your subs are falling off rapidly below their tuning frequencies. You do NOT want to ask a ported sub to produce meaningful SPL below its tuning frequency. That greatly increases the risk of physically damaging the driver.

I would recommend changing the lower limit of your optimization range to 35Hz (limit of the "weaker" sub in this regard). The upper limit stays the same (or could be increased if desired). Be sure to change the "PEQ Parameter Limits" values for the Min and Max Center Frequency to match the new optimization range. You would do this AFTER addressing the measurement issues noted by Andy. Here's a video on taking measurements for MSO using REW. It's shown on the Mac but the process is the same on Windows. (Disclaimer: Those are my videos, but you already mentioned watching them so I don't feel awkward point you at another one.)

Use the Buttkickers to cover the frequencies below 35 Hz. You can run all of this off the miniDSP. Route the input signal to all three outputs (2 subs, 1 buttkicker). MSO filters will go on the output side for just the 2 sub outputs. The output side for the Buttkickers will need a low-pass filter to keep them from playing above 30-35 Hz. I'm not sure what slope is recommended. However, based on the way your subs roll off, I'd probably start with a 4th-order (24 dB/octave) LR filter. You can use the gain features of the miniDSP or the iNuke to fine-tune the feel of the Buttkickers (or keep them from bottoming out if that's happening).

Click to expand...

So I seem to be having a problem not related to MSO so as I said I don't mind creating separate post but you've been so helpful and knowledgeable that I'll reply here first (I can edit it out afterwards).

I tried to take some better measurements as suggested by both of you. I did forget to set the LFE crossover in my Denon AVR to 250 and had on 120. I made the new measurements but it didn't make any difference weirdly.
All my speakers are set to small in the AVR and the crossover is set to 250hz So everything 250 and below should be sent to the subs only.

Both my Subs are fed trough their respective sub in (so that should prevent the crossover from their plate amps to act) and I have set the plate amps crossovers at their Max (150 for both) Took some more measurements still the same.

I looked at the miniDSP HD and the xovers are set to bypass on all channels.

I even removed the DSP from the chain but still no luck.

I moved both subs several times and took around 30 measurements and the roll off is still there. Even measured from 2 inches from the woofer and still.... could it still be my room?

I join an old layout I did before starting my basement project. It's mostly accurate except the bar never got built.

Ps. If I put one sub next in the lower left corner of the room (next to the wood stove looking at the screen) I have a huge boost between 20 almost flat to 90 then a steep cut off and silent from a 100hz on.

What else can I try?

Sorry to pollute this thread but I think that I fixed my issue as I stated in another thread I did start regarding my STSV.

I found out that by changing my AVR from Direct to multi channel in I got really different sweep results.
After seeing that result I went ahead and did all my measurements again moving my subs to find the best spots (real life doable ones) and this is what I came up with.

Let me know what you think. @andyc56 @fattire

I downloaded, watched the video, got a great graph for single position three subs and when I loaded to Mini but my sweep wasn't even close so I thought I may have mixed up something so I watched video again copied steps and got a great graph again but still not a similar response when tested in REW. This time I verified each sweep in order and basic names on sub so everything was in order when results came in to limit possible input error.
One thing I may have read wrong because I am remembering two different versions, I thought I saw one tip or tutorial state have sub at nominal distance like distance of mains or center but I thought I also read have distance and trim at zero. I ran Audyssey before doing MSO left everything the way it came up except for crossover change for REW sweep and turned off Audyssey, second attempt I adjusted sub (one output three subs) to 10 feet and raised trim on AVR to -5 just to graph to 75db so I could follow instructions and labels for original optimize to 75db and have correct results without creating more graphs (first one was 73db which is why I raised trim a little) any thoughts to troubleshoot or setup. This is end of Filter list. I tried to add enough info to verify steps but let me know if there is anything else I need to put up to get some help sorting this out.

There are no biquads needed for the shared mains filter channels.

There are no biquads needed for the shared sub filter channels.

Raw uncorrected gain and delay values:
These gain and delay values are for reference only.
Unadjusted gain values of all gain blocks:
FL7 (Sub 1, gain block) gain: -13.82 dB
FL15 (Sub 2, gain block) gain: -11.38 dB
FL23 (Sub 3, gain block) gain: -8.49 dB
Unadjusted delay values of all delay blocks:
FL8 (Sub 1, delay block) delay: 22.54 msec
FL16 (Sub 2, delay block) delay: 12.24 msec

For final gain and delay values, see
"Final gain and delay/distance settings" at end of report.

Final gain and delay/distance settings:
Complete gain settings for chosen fixed SPL target level:
These are for reference only.
Decrease AVR sub out trim gain by 8.00 dB
Sub 1 gain: -5.82 dB
Sub 2 gain: -3.38 dB
Sub 3 gain: -0.49 dB

Minimal gain settings:
Sub 1 gain: -5.33 dB
Sub 2 gain: -2.89 dB
Sub 3 gain: 0.00 dB
Delay settings:
Sub 1 delay: 22.54 msec
Sub 2 delay: 12.24 msec
Sub 3 delay: 0.00 msec

Channel inversions:
No inversions



This is my graph result.

This is REW of gains, delays and EQ applied/imported

MiniDSP





From filter so you can verify PEQ went to correct sub



REW preference to verify I did read the guide and made sure I have a timing reference channel.

Remy.Alexander said:

New to this- figured give it a try over REW-- SO watched a tut video and getting the hang of it but what I fail to see is your able to set the amount of peq filters you can use. For me 10 in 10 out for minidsp hd- so whats the point of having that feature as I dont see a separate filter for the input? id like to be able to use them all if possible.

Click to expand...

The image below shows the relationship between the miniDSP input filters and MSO's shared filters.

Remy.Alexander said:

Also for HC- are we to make our own and upload? Im not seeing an option to implement as its configuring.

Click to expand...

There is currently no target curve editor, but the docs on optimization options discuss how to export a target curve using the target curve example project. That example, together with the parameter tuning feature, can be used in a similar way. Search for "tuning" (without quotes) in the CHM help file to find examples of using the tuning feature of the Properties window.

Remy.Alexander said:

Setting a center FRQ at 10HZ should in theory allow it to set filters to correct under 10 even though minidsp limited to 10hz, is this correct thinking? IE set center FRQ 10hz and use filters to adjust lower

Click to expand...

There's probably some kind of limit for PEQ center frequency when manually entering the data (I don't own one), but you'll want to use the biquad text export from MSO to import into the miniDSP. This technique bypasses the manual data entry limits.

andyc56 said:

The image below shows the relationship between the miniDSP input filters and MSO's shared filters.

View attachment 3204870



There is currently no target curve editor, but the docs on optimization options discuss how to export a target curve using the target curve example project. That example, together with the parameter tuning feature, can be used in a similar way. Search for "tuning" (without quotes) in the CHM help file to find examples of using the tuning feature of the Properties window.



There's probably some kind of limit for PEQ center frequency when manually entering the data (I don't own one), but you'll want to use the biquad text export from MSO to import into the miniDSP. This technique bypasses the manual data entry limits.

Click to expand...

Appreciate the help-mine might be setup wrong lol not getting anything in shared just the actual sub section this is how mines displaying

I would say don't assume more is better, I am troubleshooting why mine doesn't mimic the graph in MSO when I put all parameters and EQ in MiniDSP but I will say the tutorial walks you through starting with 5 PEQ then does a second optimization with 8 PEQ so I followed along and did that but it wasn't much of an improvement. My graph above is using 6-PEQ and if you see the before graph it wasn't pretty my frequency range for optimization in criteria section is 12hz to 120hz and in the video when he sets up he state use a frequency range that is double your assumed x-over but he goes on to say he got his best results when using 120hz on another AVS members setup he was helping with. One thing to remember when using REW is automatically selects how many PEQ it needs and I have seen it range from 6 to 10 but...
Gotta love the but,
MOS might be using 6 PEQ but it is per channel so I am ending with 18 PEQ for my three channels vs 10 PEQ in REW all linked to one channel or copied to additional channels they do not have a separate EQ for EACH channel. He reserves the input side for his BEQ files but still using output only I am guessing you will have enough PEQ slots since they aren't 10 PEQ divided by number of subs like REW.

Now can anyone help with my issue a few posts above.
Do we use Audyssey measurement for Sub distance?
Do we use nominal distance for sub matching mains or center?
Do we use zero distance for sub?