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TOPIC: SHD PEQ Programming with Biquads

SHD PEQ Programming with Biquads 11 months 1 week ago #48926

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Thanks - have been looking at full range measurements - so should be OK.
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SHD PEQ Programming with Biquads 11 months 1 week ago #48927

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Thanks - have been looking at full range - so should be OK.
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SHD PEQ Programming with Biquads 11 months 1 week ago #48949

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I've just been looking at the documentation on using multi-sub optimiser (MSO) with DDRC 88M ( www.minidsp.com/applications/home-theate...-multi-sub-optimizer ) and think at this could be used with my setup - either as 2.2 system or as 2.1

Anyone tried using MSO with just 2 subs?
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SHD PEQ Programming with Biquads 11 months 1 week ago #48950

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miket wrote:
I've just been looking at the documentation on using multi-sub optimiser (MSO) with DDRC 88M ( www.minidsp.com/applications/home-theate...-multi-sub-optimizer ) and think at this could be used with my setup - either as 2.2 system or as 2.1

Anyone tried using MSO with just 2 subs?

I'm not sure how you could make use of this with an SHD?
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SHD PEQ Programming with Biquads 11 months 1 week ago #48951

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From what I can see, MSO generates filters which can be imported into SHD plugin.

I think that this could be done in 2 ways:

(A) 2.2 setup (as I currently have)
(b) 2.1 setup with 2 subs - use SHD routing so that both inputs are fed to both subs (that's what the DDRC 88M document does except that it does it with 3 subs in a home theatre setup
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SHD PEQ Programming with Biquads 11 months 1 week ago #48952

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I did use MSO with my 2x4 HD but it was at least a couple of years ago now so I forget the details, and it was for a somewhat non-standard application.
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SHD PEQ Programming with Biquads 11 months 1 week ago #49006

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Hi,

I've been using MSO to integrate two subwoofers with a pair of stereo
mains. The matrix mixer of my SHD is set as per the attached graphic.

Note that I'm crossing over into the subwoofers below 100 Hz, so both
subwoofer input signals are the summation of the left and right channels.

When you use the 2.2 nomenclature, it appears that you are implying that
one subwoofer would receive only the left channel signal and the other
subwoofer only the right channel? I wouldn't do this unless intending to
cross over at a frequency so high that localization becomes a concern.

The main reason I suggest this is that the principal advantage of having
two or more subwoofers is that they can compensate for each other's
unfortunate acoustic coupling with the room. If one has one or more
bad nulls, hopefully the postion of the other does not have nulls at the
same or nearly same frequency. Basically, they can fill in each other's
nulls. Letting MSO's optimizer adjust the delay of each subwoofer is
one of the most powerful advantages. More so, in my opinion, than
any PEQ filtering.

If applying Dirac filters in addition to PEQ, I suggest using a minimalist
approach when optimizing with MSO. Instead focusing primarily on
achieving good subwoofer integration with the stereo mains.

I did add a modest bass lift to the MSO optimizer. The reason I did so
was that I didn't want to lean too heavily on the Dirac filters to achieve
a fairly wide low frequency boost that would be better handled by
instead bringing up the subwoofer gains. There is a fairly easy way
to import a house curve into the MSO optimizer.

For Preset 1, I loaded Dirac filters that result from Dirac's recommended
house curve. For Preset 2 (all crossovers, PEQ, etc. the same as Preset 1)
the Dirac filters were instead generated with an even more boosted low
frequency. I use Preset 2 for low volume listening to sort of add a Fletcher-
Munson inspired boost. One could use all four Presets to implement a
spectrum of house curves.

I wouldn't presume the best HPF/LPF frequencies and slopes when
implementing the crossover between mains and subs. Instead, let MSO
help you find the optimal HPF/LPF filters. Use the "Configuration" feature
of MSO to advance and preserve competing filter designs. I usually keep
two MSO configurations when optimizing. I label one as the "Champion"
and the other as the "Challenger". If the Challenger eventually beats the
Champion by a substantial margin, it becomes the new reigning Champion
and a new Challenger is brought into the arena to continue the process.

The HPF/LPF filters are also useful as sort of asymmetric PEQ filters.
Their frequency and slope has an affect that is not unlike a PEQ filter
but with a sometimes useful asymmetry. The MSO optimizer can adjust
the HPF/LPF frequencies while optimizing, but not the HPF/LPF filter
type and slope. For comparing HPF/LPF filter types and slopes, the
MSO configuration feature is useful.

The Champion I went with had no PEQ filters on Subwoofer 1 and
only a single PEQ on Subwoofer 2. The mains had only a single shared
PEQ filter around 108 Hz to ease the integration with the subs. The
Q values for the two PEQ's were below 4, so fairly gentle filters.

A very simple and sparse set of manipulations. The pre-MSO room
measurements had me thinking that I had some substantial problems
that would likely require a heavy handed manipulation. Turns out
not to be the case, a gentle and simple application of filters taimed
things nicely.

The result, even with Dirac temporarily turned off sounds really good.
I think it best to have a pre-Dirac configuration that sounds and measures
reasonably well (no big flaws) before proceeding on to performing the
Dirac Live calibration.

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SHD PEQ Programming with Biquads 11 months 1 week ago #49015

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"When you use the 2.2 nomenclature, it appears that you are implying that
one subwoofer would receive only the left channel signal and the other
subwoofer only the right channel? I wouldn't do this unless intending to
cross over at a frequency so high that localization becomes a concern."

Thanks for the very helpful suggestions.

I did a test - listened to series of test tones with one channel active and listened to find at which frequency the sound did not appear to be coming from the middle - it was at about 200Hz.

My initial crossover is at 120Hz (but will try letting MSO find the best one) so I'm guessing that localization wouldn't be an issue even at 120Hz?
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SHD PEQ Programming with Biquads 11 months 1 week ago #49016

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miket wrote:
...so I'm guessing that localization wouldn't be an issue even at 120Hz?

I use a 120 Hz crossover but importantly this is using very steep crossover filters (48 dB/octave LR). This is important as it affects how far above the crossover frequency the sound from the subs extends. This works OK for me with my sub in the front-right corner, not too far away from the right speaker. If I had the sub at the rear of the room it might be more of an issue - I've not tried. The reason I have such a high crossover is mostly because this is the best point to use for phase matching to my main speakers, which is more challenging than or many due to an asymmetric setup.

Higher crossovers also have the advantage of moving the crossover region away from the natural roll-off of main speakers. Where this overlaps with a miniDSP crossover applied to the main speakers you'll get a faster roll-off than just the DSP suggests and so you need to factor this in.
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SHD PEQ Programming with Biquads 11 months 1 week ago #49017

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miket wrote:
I did a test - listened to series of test tones with one channel active and listened to find at which frequency the sound did not appear to be coming from the middle - it was at about 200Hz.

Reading this back I'm a bit confused by what you actually tested here? Was it playing tones sent to both main speakers plus one subwoofer? I'll bet if you played just the sub you'd be able to localise sound to the sub at frequencies lower than 200 Hz.

If you did test as I guessed then at the point you were localising sounds to the center of the soundstage rather than having no discernible direction at all you were already into a frequency range above where you'd want to run the sub.
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SHD PEQ Programming with Biquads 11 months 1 week ago #49018

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Ultrasonic wrote:
miket wrote:
I did a test - listened to series of test tones with one channel active and listened to find at which frequency the sound did not appear to be coming from the middle - it was at about 200Hz.

Reading this back I'm a bit confused by what you actually tested here? Was it playing tones sent to both main speakers plus one subwoofer? I'll bet if you played just the sub you'd be able to localise sound to the sub at frequencies lower than 200 Hz.

If you did test as I guessed then at the point you were localising sounds to the center of the soundstage rather than having no discernible direction at all you were already into a frequency range above where you'd want to run the sub.

Apologies - should have made it clearer. Testing was done by playing test tone to one channel with both main and subwoofer on (using 24dB/Octave filter at 100Hz). I tried it with both left and right channels (separately of course), started at 30Hz, went up at 10Hz intervals (up to 100Hz) and then 100Hz intervals. Listened for the point where the sound started to move from the centre to the left or right.

My subwoofers are located directly underneath each of the main speakers (which are wall-mounted). I was surprised that I didn't hear the image start to move left until 200Hz. Maybe it's because my room is long and thin - the speakers are 2.5 metres apart but the listening position is 5 metres away.
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SHD PEQ Programming with Biquads 11 months 1 week ago #49019

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miket wrote:
Apologies - should have made it clearer. Testing was done by playing test tone to one channel with both main and subwoofer on (using 24dB/Octave filter at 100Hz). I tried it with both left and right channels (separately of course), started at 30Hz, went up at 10Hz intervals (up to 100Hz) and then 100Hz intervals. Listened for the point where the sound started to move from the centre to the left or right.

My subwoofers are located directly underneath each of the main speakers (which are wall-mounted). I was surprised that I didn't hear the image start to move left until 200Hz. Maybe it's because my room is long and thin - the speakers are 2.5 metres apart but the listening position is 5 metres away.

I still don't follow to be honest. Why is the sound ever central? It shouldn't be for playing a single channel.

Are you sending a left channel signal to a left subwoofer and a right channel signal to a right subwoofer? As suggested above I would not do this unless you're forced to by virtue of using an overly high crossover frequency. You're also likely limiting performance if by choosing subwoofer locations directly below the main speakers. It may be this is all you're happy to do aesthetically but from a performance point of view there are likely far better combinations of positions. If your room is roughly cuboidal then the Room Simulator in Room EQ Wizard would be worth experimenting with to give you some ideas of setups to try.
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SHD PEQ Programming with Biquads 11 months 1 week ago #49022

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Ultrasonic wrote:
miket wrote:
Apologies - should have made it clearer. Testing was done by playing test tone to one channel with both main and subwoofer on (using 24dB/Octave filter at 100Hz). I tried it with both left and right channels (separately of course), started at 30Hz, went up at 10Hz intervals (up to 100Hz) and then 100Hz intervals. Listened for the point where the sound started to move from the centre to the left or right.

My subwoofers are located directly underneath each of the main speakers (which are wall-mounted). I was surprised that I didn't hear the image start to move left until 200Hz. Maybe it's because my room is long and thin - the speakers are 2.5 metres apart but the listening position is 5 metres away.

I still don't follow to be honest. Why is the sound ever central? It shouldn't be for playing a single channel.

Are you sending a left channel signal to a left subwoofer and a right channel signal to a right subwoofer? As suggested above I would not do this unless you're forced to by virtue of using an overly high crossover frequency. You're also likely limiting performance if by choosing subwoofer locations directly below the main speakers. It may be this is all you're happy to do aesthetically but from a performance point of view there are likely far better combinations of positions. If your room is roughly cuboidal then the Room Simulator in Room EQ Wizard would be worth experimenting with to give you some ideas of setups to try.

Even bigger apology! Just redid my localisation test. Must have done something wrong before. This time sound remained clearly left or right from about 65Hz upwards. My crossover is at 120Hz (main speakers have natural roll off at 12dB/Octave below 115 Hz) so I think that suggests that I need to stick with separate L and R signals to subwoofers.

Just finished tweaking Dirac calibration. Measurement (at listening position) shows - from 30Hz to 12KHz - deviation from my target curve as:

A Crossover Only - 10dB variation (peaks or dips up to 5dB)
B Crossover + PEQ - 5 dB variation (highest peak 3dB, lowest dip 2dB)
C Crossover + PEQ + Dirac (using single point measurement as suggested) - 1dB variation i.e. no variation more than plus or minus 0.5 dB from target!

Thanks for your suggestions - most helpful.

I'll try out MSO next - partly just to see what it comes up with.
Last Edit: 11 months 1 week ago by miket. Reason: typo
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SHD PEQ Programming with Biquads 11 months 1 week ago #49023

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miket wrote:
Even bigger apology! Just redid my localisation test. Must have done something wrong before. This time sound remained clearly left or right from about 65Hz upwards. My crossover is at 120Hz (main speakers have natural roll off at 12dB/Octave below 115 Hz) so I think that suggests that I need to stick with separate L and R signals to subwoofers.

Ah, right, with main speakers that roll-off from such a high frequency I can see you might be into wanting left and right sub channels, particularly with the required very slow roll-off filter on the sub. I'm still surprised you can localise sound and 65 Hz though. Were you running the test at high volumes? I'm wondering if it was distortion generated somewhere that you were localising rather than the pure 65 Hz signal.

miket wrote:
I'll try out MSO next - partly just to see what it comes up with.

I might be wrong but I think you'll find that MSO is aimed at a single (mono) subwoofer channel rather than the left/right split that you currently have in mind.
Last Edit: 11 months 1 week ago by Ultrasonic.
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SHD PEQ Programming with Biquads 11 months 1 week ago #49037

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I'm in agreement with Ultrasonic on both counts.

It's possible that there is a bit of pyschoacoustic phenomena going on
when conducting this test.

If you're going to take REW measurements for the mains and subwoofers,
perhaps you can share the resultant FRD files with us? I"d like to import
into MSO and see what it predicts.

A link to AndyC's reference page for gathering REW measurements is
below. It'd be good to get measurements with the high/low pass filters
and PEQ defeated. One of the mains will need to be used as an acoustic
timing reference. Start with the master volume of the SHD set low, check
the playback level in REW and ease up the volume until at a useful but
safe level.

www.andyc.diy-audio-engineering.org/mso/html/measuring.html
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