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Bass management/LFE processing question [message #87650] Tue, 30 June 2020 05:17 Go to next message
hakonholmas is currently offline  hakonholmas
Messages: 5
Registered: June 2020
Location: Norway
Junior Member
Hi

Considering the 2882 3D for my setup but I have one question -
Can I make a setup where the LFE-send to the subwoofer is processed with an All pass filter, to phase match the signal with the low passed bass management signals?

here is a link to a video explaining why this is important:

Quote:
You cannot use links until you have posted more than 300 messages.


uh ok, but youtube->meyer sound -> Amie System - Multichannel - Plug and Play (English)
Relevant discussion starts at around 36 minutes
Re: Bass management/LFE processing question [message #87656 is a reply to message #87650] Tue, 30 June 2020 15:57 Go to previous messageGo to next message
bj is currently offline  bj
Messages: 412
Registered: July 2011
Senior Member
Short answer is yes.

The Monitor Controller outputs have DSP graphs associated with them. The graph can host Crossover, delay, all pass, eq, etc. Precisely how you would configure that is a different question. Probably the easiest way to do it would be to pass the LFE though the same LP filter. If that is being sent to an LF driver (rather than a full range) you should have no phase cancellation an the HF rolloff is going to happen in the sub anyway...

But yes, there are Allpass primitives available and you could use SpectraFoo to measure and compensate the filter phase response.
Re: Bass management/LFE processing question [message #87657 is a reply to message #87656] Tue, 30 June 2020 15:58 Go to previous messageGo to next message
bj is currently offline  bj
Messages: 412
Registered: July 2011
Senior Member
Nice presentation by Juan Sierra Lozano, BTW.
Re: Bass management/LFE processing question [message #87662 is a reply to message #87657] Tue, 30 June 2020 17:00 Go to previous messageGo to next message
hakonholmas is currently offline  hakonholmas
Messages: 5
Registered: June 2020
Location: Norway
Junior Member
Great!

Sounds like I´ll be able to do what I need
I have the Meyer Amies so I want to mimic the setup Juan describes in the video without buying the card (it was not available when I purchased the speakers)
I prefer to have software control anyway.
My primary use case is normal stereo mixing, but I´d like to be able to do a properly set up surround system when needed.

I´ll be measuring this using Smaart8 as it is the software I normally use, but Spectra foo sounds very interesting, is it bundled with the interface?


Another possible use case I see for this interface would be temporary cinema deployments in up to 7.1
I´ve done this a few times using either dolby lake or meyer sound processors, but this interface could just as easily do it.
It will keep passing audio even if I disconnect the computer, right?
Re: Bass management/LFE processing question [message #87663 is a reply to message #87662] Tue, 30 June 2020 17:07 Go to previous messageGo to next message
bj is currently offline  bj
Messages: 412
Registered: July 2011
Senior Member
You can read more about SpectraFoo here:

https://mhsecure.com/metric_halo/products/software/spectrafo o.html

It is not included with the interface.

You might be able to make the measurements with Smaart; not sure.

It will continue to pass audio if you disconnect the computer.
Re: Bass management/LFE processing question [message #87666 is a reply to message #87663] Tue, 30 June 2020 18:08 Go to previous messageGo to next message
hakonholmas is currently offline  hakonholmas
Messages: 5
Registered: June 2020
Location: Norway
Junior Member
Thanks, I´ll read up on it

Looks like I might need it. lots of measurement capabilities I don´t have in Smaart.

OK, looking into the graphs now, WOOOW!! I can do pretty much whatever I want here.
The only think I can´t find is the ability to run an FIR-filter
I sometimes use these to flatten the phase of speaker that have too many phase wraps / too much phase delay / untight impulse response
Currently I use a MiniDSP openDRC to run the FIR-filters but having FIR included in my presets for different speaker setups would be killer.
Re: Bass management/LFE processing question [message #87667 is a reply to message #87666] Tue, 30 June 2020 18:43 Go to previous messageGo to next message
hakonholmas is currently offline  hakonholmas
Messages: 5
Registered: June 2020
Location: Norway
Junior Member
Hmm, looking into it more deeply.
Seems like the only low pass/high pass filters available are 2nd order butterworth (12db/octave) and I can stack 2 of those to get 4th order linkwitz riley
Would be great to have a graph block with freely configurable filters, for greater flexibility.

Also, the APF block confuses me. It needs coeficcients, which I could probably figure out how to generate, but the smoother way would be to have a block with these parameters,
Center frequency
Q
Filter order

I realise this might not be top priority for you guys, but if you could put it on your long list of feature requests I´d be happy Smile
Re: Bass management/LFE processing question [message #87671 is a reply to message #87667] Wed, 01 July 2020 18:53 Go to previous messageGo to next message
bj is currently offline  bj
Messages: 412
Registered: July 2011
Senior Member
There is a bandsplit primitive; it is 4th order LR.

It also forms an all pass filter if you sum its outputs. So if you use the bandsplit to do the Bass management, you can run the LFE into another copy of the band split set to the same crossover point and sum its outputs to get a full-range all pass that will have the same phase shift as the LPF output of the bandplit that you use for the bass management on the full mix.

The APF is a simple single pole APF - its a building block.
Re: Bass management/LFE processing question [message #87672 is a reply to message #87671] Thu, 02 July 2020 03:32 Go to previous message
hakonholmas is currently offline  hakonholmas
Messages: 5
Registered: June 2020
Location: Norway
Junior Member
Ah cool. A workaround, but workable Smile

OK, this interface certainly seems like the more flexible option of the ones I´m considering. As far as I can see it is not very common anywhere to have the functionalities of an advanced speaker processor inside computer audio interfaces. This is the closest I´ve seen.
Seems to me like it could be easy for you to make an advanced filter primitive. It would be a great addition to your products, it could completely eliminate the need for a separate crossover/speaker processor.

Might I suggest you take a look at this plugin, for a suggestion of a nice interface to copy:

eecs.qmul.ac.uk/~andrewm/composer/crossoversetup.html
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