Active crossovers.

Moderator: flatmax

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Active crossovers.

Post by pav » Mon Feb 20, 2017 10:20 pm

From the kickstarter page:
'Example applications [...] Active crossovers, up to 8 way, or 2 speakers each 4 way...'
It might be helpful to share more practical advice in that respect, if possible illustrated by completed projects. I cannot praise enough the work of Richard Taylor: ... are-howto/

He acomplished an implementation of a complex crossover system in Linux ecasound and also reported a successful port to RPi. I think that a specific to Octo and tested-in-practice how-to would open a market of the lesser IT savy melomans.

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Joined: Tue Apr 25, 2017 11:59 am

Re: Active crossovers.

Post by J.Luszczek » Tue Apr 25, 2017 12:11 pm

I'm getting my octo card this week. I plan on using it as digital crossover as well. My plan is to run a plugin host and configure the crossover legs using EQ and filter plugins. The task will be to find the most stable host that reliably boots up into active state. I think that Reaper for Linux will be a good candidate.

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Re: Active crossovers.

Post by J.Luszczek » Sat Apr 29, 2017 11:08 am

Well, this was easier than I thought. I got my Raspberry Pi to boot and connected to it first with SSH and then with VNC Viewer. I installed the Octo drivers per the instructions on this forum, then downloaded Jack audio connection software and finally the unofficial version of Reaper for Linux with Arm processing.
Fired up Reaper, set the audio device to Jack, 6 in, 8 out and created 4 stereo busses in Reaper, each sending to a different pair of outputs.
I added a stereo track, set sends to all 4 busses from it and engaged the record button. I got audio on the input and on all 4 outputs.

I listened to all 8 outputs to verify that they work, changed the inputs in Reaper to the remaining 2 pairs to verify that they all work, and they sure are all working fine.

Next I inserted Parametric EQ and delay on every output bus, set the EQ's to 6 or 7 bands plus High Pass and Low Pass filters, and watched it all function smoothly on the first try. Here is a picture of my VNC session: ... sp=sharing

As you can see the CPU utilization is in the 25% range. I can most likely load a FIR filter on the input for room correction with no real penalty on CPU.

Tomorrow I'm going to try and figure out the GPIO so that I have a volume control on a 10k pot and a mute on a push switch.

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Re: Active crossovers.

Post by flatmax » Sat Apr 29, 2017 2:13 pm

That looks great can you take a screenshot by pressing print screen on your keyboard or something like that.

Upload it here please !

Check out our audiophile quality crossovers :
Please review the Zero sound card on Amazon USA :
Check out our new forum on github :

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Re: Active crossovers.

Post by J.Luszczek » Sun Apr 30, 2017 4:11 am

Report 2.
I went to try Carla audio plugin host this morning and after a bit of fiddling with adding new repositories to the system, because Carla is not in the default repository I was able to download and install it, along with some audio processing plugins. Carla started up and loaded the plugins, then let me connect them and passed audio. I saved the session and restarted it, which resulted in lost connections. The plugins were still there but all the lines connecting them were gone. I will have to ask around to find out how to make it reliable. For now Carla is not an option eventhough it would be easier to make cool setups using it.

Reaper starts and passes audio with no problems and its plugins are more sophisticated and more appropriate for creating crossovers.
For something like whole house sound systems with multiple zones, separate volume controls and source selectors I would probably prefer Carla as the software.

here are a couple of screen shots:


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