AVS Forum banner

341 - 360 of 2040 Posts

·
Registered
Joined
·
533 Posts
Good day all,

would anyone be able to answer the question I posed above regarding the AVR gain adjustment. Maybe I'm over thinking things, and should just add the recommended amount of gain to the AVR and move on...

The reason I hesitate is because I have individual subwoofer adjustment on my AVR. since Im using two subs, as I understand it, the doubling of the output adds another +3 db. So if MSO is calling for a total of +8dB gain would I raise each subs gain by +5dB assuming that the two subs combined would then yield the +8dB?

alternatively I guess I could also take this to mean that MSO is accounting for that +3dB based on the number of sub channels, and the +8db gain is just the adjustment needed but not the expected total dB gain....

A third option is, that I could be completely wrong about it all...

Either way, I would appreciate an answer. Thanks in advance
 

·
Registered
Joined
·
42 Posts
Using MSO in my Living Room Home Theatre – Part II

After the first success with MSO-tuned gain, delay and PEQs – I’ve tried a sink-source subwoofer/ bass array setup.

A bass array usually gets recommended, if the room is of perfect rectangular shape, and 2x1, 2x2 or 2x4 identical subwoofers could be placed at specific positions on opposite walls.
Under perfect conditions it corrects room modes as far as possible without the need of EQ-ing and delivers pretty short reverberation time in that area.
But our living room with attached kitchen (L-shape) and the usage of 3 subwoofers are way of perfect conditions – but with the miniDSP 88 BM update it was easy to give it a try…


Again, our living room home theatre…

LivingRoomHomeTheatre_Overview.PNG

First I configured the front subs with identical gain and delay, and bypassed PEQs on all subs. Then I inverted the polarity of the rear sub and measured at PLP with REW’s RTA to find the right delay, so that its inversed moving woofer attenuates the longitudinal modes at its best. And it was no big surprise that the perfect delay was around 19 ms because of the room length (approx. 6,42 m divided by speed of sound 0,34 m/s = 18,9 ms). I had to raise the gain for sub 3 by ~5 dB to reach the right level before it over corrects.

REW_PLP_SSS_combined_response_unoptimized.png

In my first try of MSO sub-only optimization, I’ve added polarity inversion to sub 3 and still let MSO access to delay and gain. It was interesting to see that MSO often came up with a delay for sub3 around 19ms (+/- 1ms). I decided to lock Sub3’s delay at 19ms and made some REW measurements.

Results:
At this time I’ve used 85dB as MSO reference level, until I’ve recognised, that 82.5dB matches perfectly
Frequency/ amplitude domain looked pretty good with 8 PEQs MSO-optimized
But Dirac Live was able to flatten the response further

PEQ-Filters_SourceSinkSubs_8PEQs_Gain+-10_Delay-fixed.png

REW_PLP_SSS_combined_response_optimized_pre+post_Dirac.png

But what happened in the time domain? A “hole” or time shift at the first modal frequency? :confused:
It’s interesting to see, how Dirac tries to correct for the later response of the area below 45Hz. But also the “hole” moved from ~28Hz to 26 Hz

REW_PLP_SSS_optimized_combined_response+Spectrogram_8PEQ_flat.png

REW_PLP_SSS_optimized_combined_response+Spectrogram_8PEQ_flat+Dirac.png

I wondered what causes that “hole”/ time shift... and found out that the reason was a +10dB gain on the inversed Sub3 MSO figured out.
After I locked all gain level and did another optimization run and measurement – it was gone.

PEQ-Filters_SourceSinkSubs_8PEQs_Gain+Delay-fixed.png

REW_PLP_SSS_combined_response_optimized_pre+post_Dirac_fixed_gain.png

REW_PLP_SSS_optimized_combined_response+Spectrogram_8PEQ_flat-fixed-gain+Dirac.png

Finally I measured the different hearing positions again, with MSO optimized 8PEQ settings and Dirac Live (9 Positions measured) to check for the reached seat-to-seat variation. And I’m quite happy with the archived results so far:

REW_Seat2Seat_SSS_combined_response_optimized_pre+post_Dirac_fixed_gain.png

These results encourage me to go for a fourth sub for the back wall an try out what further improvement is possible … :rolleyes:

Any suggestions and feedback welcome…

Regards,
Sven
 

·
Registered
Joined
·
42 Posts
I've just uploaded a new version, 1.17. It has the following changes:

  • Added ability to save scaled PNG files of graphs.
  • Disable reference frequency range controls in Optimization Options, Criteria for sub-only configs whose optimization method is Best match of MLP with other listening positions.
  • Allow low-pass filters to have a maximum legal cutoff frequency of 300 Hz.
  • Delete graphs that have no traces after a config is deleted.
  • Collapse individual config and graph nodes by default.
  • Updated help files.
The PNG file save uses a facility in the graphics library I'm using that allows rendering to any size of rectangle. A side effect is that the library automatically changes the units per division to fit the size of the graph. This isn't under my control. For example, a full size graph might look like this:
Andy, thank you for implementing these optimizations. After a while of working with MSO V.1.17 I have to say that this helped me a lot speeding up the work with MSO!
:nerd:

Regards, Sven
 

·
Registered
Joined
·
1,680 Posts
Hi Sven,

I noticed when I was replying to your earlier post that you're using an unusual way of attaching images, and your comments for your post edit indicated you were having some problems with images. Back when VerticalScope took over the forum, things got weird in regard to image posting. Check out this post by LTD02 for a good way of uploading images and putting them inline in your posts.
 

·
Registered
Joined
·
1,680 Posts
Version 1.18 is out now. It has the following changes:

  • The fixed reference level optimization mode can now be used for "sub + mains" configurations. This can help when the main speakers have a reduced upper bass output as might occur from baffle step effects.
  • LF shelf filters can now have an LF corner as high as 500 Hz to be used for main speakers to help compensate for baffle step effects.
  • Added ability to save graph traces as .frd files.
  • Filter reports of HF shelf filters now contain a high-frequency corner as needed to specify them for Behringer hardware.
  • Filter reports of parametric EQ filters now contain bandwidth in octaves per Bristow-Johnson's PEQ specification. This is for software such as Equalizer APO, and avoids situations for which the hardware or software supplier uses a different definition of Q than what MSO uses.
  • Bug fix: Allow high-pass filters in shared sub channels.
Documentation changes include the following:

 

·
Premium Member
Joined
·
3,071 Posts
I finally was able to get good measurements of my subs and test out MSO. It was very difficult.

REW would think delay was 5ms or 30ms on only a couple measurement positions (which neither is correct).

So I am able to get a pretty flat result which is great. The software works! Thank you Andy.

Problem is flat does not sound so good. Is there a reason target curves can't be applied to subwoofer only configurations?
 

·
Registered
Joined
·
1,680 Posts
Problem is flat does not sound so good. Is there a reason target curves can't be applied to subwoofer only configurations?
I had assumed that for sub-only configurations the final, global EQ would be done using either some other system such as Dirac, or with MSO including the main speakers after the other system has been run. Here's how AV_Mike does it. The final result will reflect both the subs and their interaction with the main speakers. How did you plan on getting the final response to fit the curve without taking into account the main speakers? Maybe I could relax the restriction, but I'd like to understand better what you're doing.

There's lots of things that can go wrong when the main speakers aren't included, such as high-end rolloff due to high-inductance subs affecting the curve.

But I am a two-channel guy and do not run any FIR-based room correction systems, so I'd like to understand as much as possible about how people resolve this dilemma. AV_Mike's post linked above is the most detailed explanation I've read so far.

I finally was able to get good measurements of my subs and test out MSO. It was very difficult.

REW would think delay was 5ms or 30ms on only a couple measurement positions (which neither is correct).

So I am able to get a pretty flat result which is great. The software works! Thank you Andy.
You're welcome!

Keep in mind the calculated delay for subs in REW is not meaningful. The REW documentation on that is here (at the bottom of the page). I also mention in in the MSO documentation here. I've copied the relevant text below.

REW manual said:
If using a timing reference REW can calculate the delay through the system being measured relative to the reference and show it in the measurement Info panel as "System Delay" in milliseconds, with the equivalent distance in feet and metres shown in brackets. Note that delay values are not accurate for subwoofer measurements due to the limited bandwidth of the subwoofer response, the delay estimate is based on the location of the peak of the impulse response and subwoofers have a broad peak and a delayed response.
 

·
Premium Member
Joined
·
3,071 Posts
I had assumed that for sub-only configurations the final, global EQ would be done using either some other system such as Dirac, or with MSO including the main speakers after the other system has been run. Here's how AV_Mike does it. The final result will reflect both the subs and their interaction with the main speakers. How did you plan on getting the final response to fit the curve without taking into account the main speakers? Maybe I could relax the restriction, but I'd like to understand better what you're doing.

There's lots of things that can go wrong when the main speakers aren't included, such as high-end rolloff due to high-inductance subs affecting the curve.

But I am a two-channel guy and do not run any FIR-based room correction systems, so I'd like to understand as much as possible about how people resolve this dilemma. AV_Mike's post linked above is the most detailed explanation I've read so far.
I have a lot of natural energy in the 30-50hz region of my subwoofers. MSO cuts all that down to make it flat 20-150. Then I will boost with Dirac (or simliar) and now I'm boosting a signal that naturally doesn't need as much boost. Limiting my headroom on the input of my minidsp device (8v max input). In the big picture it may not be a big deal as there are other areas of the curve that need shaping.

I'd like to optimize my subs with MSO as closely to how I would have them set with Dirac so when I run Dirac, etc it does less boosting (or less cutting depending on how you look at it).

Make sense?


Keep in mind the calculated delay for subs in REW is not meaningful.
So is a timing reference not important for a sub only configuration? Meaning it does not impact the finished result of MSO?