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Author Topic: Need help for stereo subwoofers management - 7.2 setup  (Read 3546 times)

Twangking

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Need help for stereo subwoofers management - 7.2 setup
« on: April 15, 2016, 11:51:59 pm »

Hi everybody,

I need your help for my setup, which seems to be a bit particular. First I would like to apologize if some of my formulations are not correct, I'm French and not so comfortable with English language.


The biggest problem is that I would like to map low frequencies on two different subwoofers, but in stereo. To be clear : left low on left sub, right low on right sub.

The second problem comes from the fact that the Front speakers should be set in small from above 80Hz, and the 5 others (center + surrounds) should be set in small to, but above 200Hz.




Here is my setup in details :

- Front  : Cabasse Baltic II (80Hz - 22KHz)
- Center, surround and surround back : Cabasse ioČ (200Hz - 22KHz)
- Subs : Cabasse Thor II (22Hz - 200Hz) x 2

Audio device : USB Focusrite Scarlett 18i20.



...And what I want it to do:

out 1 - [Front left >80Hz]        
out 2 - [sub left]          
out 3 - [Front right  >80Hz]          
out 4 - [sub right]  

out 5 - [Surround left >200Hz] -> low below 200Hz on out 2
out 6 - [surround back left >200Hz] -> low below 200Hz on out 2
out 7 - [Surround right >200Hz] -> low below 200Hz on out 4
out 8 - [surround right >200Hz] -> low below 200Hz on out 4
out 9 - [center >200Hz] -> low below 200Hz on out 4


Thank you very much for your help.  ;)

Arindelle

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #1 on: April 16, 2016, 03:06:11 am »

bump on this

I was trying to steer the OP in the right direction in the French forum, but I'm no expert on essentially a 7.2 system.

I know some of you have the focusrite, and I'm not sure about the channel mapping. He was trying to do this through room correction, but I think this should be mapped via Parametric EQs? Also, not sure what the Output Format should like for him.

On a side note he also mentioned that maybe it would be good to have a "mono" zone for his two boomers for movies. But I imagine once the stereo is set up, its just a question of adding a zone and zone switch rule if desired.

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mattkhan

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #2 on: April 16, 2016, 03:36:01 am »

I would think you need a more than 10 channel output format (which results in a 7.1 mix target iirc) and I would stick to the usual 7.1 channel mappings but use the last 2 channels as your subwoofer output channels. I say more than 10 because you might find you need to have a few channels spare to use as temporary channels while you mix things around.

You would then have to do all the mixing using PEQ. You would use room correction, if you want, to set to delays amongst the main channels only (you could also do this in PEQ if you want).

The basic process is going to be something like

- attentuate the input main channels by the required amount (to be worked out later but remember to include the LFE adjustment)

sub summing for L
- copy the FL into tmp channel 1, apply HPF
- copy the SL into tmp channel 2, apply HPF
- copy the RL into tmp channel 3, apply HPF
- sum tmp channels 1,2,3 into Lsub channel
- apply delay to alignment Lsub output
- wipe tmp channels 1,2,3

repeat sub summing for for FR, SR, RR with Rsub channel as the target
- apply delays to time align main channels (aligning the l sub to the l speaker and the r sub to the r speaker and verifying that they sum OK by measurements)
- apply gain to bring levels back up to the correct level

2 things are missing from this process because it's not obvious what you want to do

- don't you want to spread the low pass of the C across both subs? you seem to be aiming it at the right sub at the moment which seems odd, if so then you want to cut that channel by another 6dB and then include it in the summing for each sub
- where is the LFE channel going? spread equally across both subs? if so treat as per the C (attenuate by a further 6dB and add to both subs)

Also why the different corner frequencies for the crossovers? Different speakers in each position?

A default starting position for the amount of attentuation to apply is

- reduce all main channels by 15dB
- reduce LFE by 5dB
- apply bass management
- raise all main channels back up by 15dB
- raise LFE channel up by 15dB (but if you do this digitally in jriver, you'll clip so IMV this is ideally done downstream either in an analogue gain stage or some other downstream piece (e.g. if your DAC has variable output levels and a mixer then you could crank it's output gain up and then trim the main channels in its mixer)

I think the above should work but I haven't worked through it in detail so someone might be along to correct me soon.

I recommend you write down the workflow you intend to apply and post it here for review... do a flow chart if you like :)
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Twangking

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #3 on: April 16, 2016, 06:16:27 am »

Yes, I will post a workflow, it will be more clear to understand.  ;)

Twangking

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #4 on: April 16, 2016, 10:54:00 am »

Just a thought :

The LFE channel is mapped on outputs 3 & 4 of the Focusrite.

I could simply copy the front L & Front R with low pass filter, and mix them with the LFE channel in the Focusrite soft. And then map them on out 3 & 4. Too simple to be good ?

No need to modify delays, the subs and front speakers are at the same distance from the sweet spot.

mattkhan

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #5 on: April 16, 2016, 04:53:40 pm »

you still need to manage the gain for each channel so it's not obvious what benefit you get from doing it mixcontrol vs doing it in jriver. Personally I'd do all mixing in one place (dsp studio) otherwise it will get confusing to maintain but that's just my view.
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Twangking

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #6 on: April 17, 2016, 02:54:27 am »

Yes, you are right. Even if I could save the Mix control setting not to loose it, but it will be safer to keep all the process in JRiver. It was just a quick way to do it, as a test.

I will begin by only map the front channels in stereo. I was upset of summing the subs in mono mainly for stereo sources. Mapping the surrounds will be the final touch but I can stand to keep the low section of them on both subs for the time for 7.1 sources.

The setup need two different crossovers because I have two different types of speakers. Front are Cabasse Baltic II, which go down over 80Hz, as center and surrounds are Cabasse IoČ, which only go down over 180Hz.

Thanks for your help.  ;)

haga7584

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Re: Need help for stereo subwoofers management - 7.2 setup
« Reply #7 on: April 11, 2017, 04:56:04 am »

Twangking, did you ever get this working fully?  I'm in the same boat but also want to Bi-amp my fronts.  Reading what you guys are a bit confusing since I'm new to JRiver PEQ.
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