Cant control sub channel anymore.
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First of all, Im not really an audio guy. I cobbled this setup together with limited knowledge, but it worked.
So I have a frankensoundsystem of Edifier 1700BTs paired with the active sub from an old pair of Logitech Z623s.
Sound card set to 5.1. Edifiers plugged into front out, sub plugged into center/sub out. I use EqualizerAPO to control the volume of the sub.
Worked perfectly for a year, but since like a week or two ago, it stopped. I can control R/L channels normally, but for some reason the SUB channel doesnt budge. Ive tried reinstalling APO, sound drivers, peace, you name it. Ive tried all the troubleshooting options in the configurator. Nothing. Im pretty sure there was a Windows update in there somewhere, but usually a reinstall resolves that without a hiccup.
I can do a sound test in my sound driver app and the sub works normally from there.
Any ideas?
And the card is still on 5.1? A Windows update may include an audio driver which may set everything to default.
Card is still 5.1. Windows update was one of my first thoughts too, but I checked and all the options seems to be as I left them.
Perhaps you can attach the Peace config so I can take a look at it?
Solved- ish. What ended up working is copying over the L and R channels over to LFE. But its still a mystery why the configuration that worked for so long suddenly decided to stop.
The config file that worked before:
Channel: SUB
Preamp: 0 dB
Filter: ON LP Fc 100 Hz
Config that I got working now:
Copy: LFE=L+R
Channel: LFE
Preamp: 0 dB
Filter: ON LP Fc 100 Hz
Looking at it now, I have no idea where the "SUB" channel even came from. And how did it work if it wasnt even defined anywhere.
I used Peace for the original configuration. Is it possible Peace did something outside of the config file that got removed when I reinstalled/during windows update?
Edit: Forgot to mention, EqualizerAPO version is the same it was before.
Last edit: Janez Kranjski 2023-09-19
What seems to have happened here is that, previously, something else was doing bass management for you ("bass management" is the technical term for "redirecting main channels bass frequencies to the sub channel" - something has to do it, it doesn't happen magically), but then at some point that something else stopped doing that, so now you have to do it yourself.
It's difficult to tell what happened without understanding how your previous setup was working. It could be that previously your audio driver was doing the bass management implicitly without you realizing it, and the audio driver was updated/replaced so it's not doing that anymore. It could also be that the Windows standard built-in APOs were doing the bass management before, and now for some reason they aren't. Maybe the Windows APOs are now bypassed, or perhaps your speakers are incorrectly configured as "large" in your Windows audio speaker settings.
Note that this config is very incomplete if you want to do bass management in Equalizer APO, and will give incorrect results. You only have half the crossover (you need a highpass filter on the mains otherwise you're getting twice the bass), you need to redirect the bass from the center and surround channels as well, and by convention you need to apply a +10 dB gain to the original signal that was already present in the LFE channel. For more information on bass management and how to do it correctly, see ITU-R BS.775 Annex 7, which is the authoritative specification on this topic and explains these concepts very well.
"SUB" is synonymous to "LFE" in Equalizer APO - they're the same thing and you can use the two terms interchangeably in the Equalizer APO config.
Last edit: Etienne Dechamps 2023-09-19
https://sourceforge.net/p/equalizerapo/wiki/Configuration%20reference/
I don't see SUB channel name defined there in documentation (it should point to channel number 4 but of course it can be a hidden def) so, you're probably right in saying bass management has been done elsewhere earlier.
Regarding LFE there is also an attention in documentation.
The original versions of Equalizer APO only recognized the channel name "SUB", not "LFE". Back in 2016 I asked the developer to change it to LFE, and he did, while still preserving compatibility with the old name to avoid breaking existing configs. So, basically, the "SUB" channel name is technically deprecated and obsolete, which is likely why it's not mentioned in the current docs.
Only when you install Peace again AND it doesn't find the "include: peace.txt" command it will overwrite the config.txt file immediately after the popup message asking confirmation for this overwrite. But when installing a Windows update nothing happens to Peace. It may "break" Equalizer APO. Usually starting its Configurator resolves this.
Thank you Etienne and Peter.
I guess it remains a mystery who did the bass management before, I dont think I am prepared to sink my whole afternoon into figuring it out. I'll write down my current settings and keep an eye out the next time Windows updates.
I've edited the config and this is where I'm at currently. I hope I understood your advice correctly.
Your config looks close to correct. I'd just suggest a couple of improvements:
For Linkwitz-Riley filters you could take a look at and/or copy them from Peace. It has these filters. They are build from the standard LP/HP Equalizer APO filters.
Or perhaps I can build a Peace config for you.
@Etienne Dechamps Isn't it better to first low filter the L, R, etc. and then feed them onto LFE? Or it doesn't matter if it's done afterwards on LFE like Janez did?
Ah, this is a subject of much debate in LFE discussions. Basically, there are 4 possible approaches:
All these approaches are potentially valid, but have different pros and cons.
Approach (1) usually results in the simplest config. Janez's configs follow approach (1), and I personally use it as well.
Approach (4) has the benefit of not throwing away any information - you get to hear everything that it's in the LFE channel, even >120 Hz frequencies - but that's both a blessing and a curse, because even the monitoring systems that the content producers themselves use typically don't do this, and as a result some content can accidentally end up with "garbage" high frequencies in the LFE channel that the producer couldn't hear and therefore didn't notice... but anyone using approach (4) will hear that extra garbage! This is not just theoretical by the way - there is documented evidence of it happening on blockbuster Blu-ray releases. I used approach (4) for a long time but abandoned it when I stumbled upon such content.
Approach (2) seems like a reasonable compromise, but I don't like the idea of >80 Hz LFE content potentially making the sub localizable. Also, it's not a given that the producer's monitoring system is able to reproduce 80-120 Hz content in the LFE channel (the producer could be using approach 1, willingly or not), so there might be garbage there too. Honestly, I think that content producers should basically assume the worst case scenario which is given by approach (1) - i.e. they should not assume that the consumer's playback system will be able to reproduce LFE content between 80 and 120 Hz. They should just stick to <80 Hz for LFE, IMHO.
Approach (3) is really just approach (2) where the cutoff frequency is given by the natural cutoff frequency of the particular subwoofer used (often 250 Hz or whereabouts).
Sadly ITU-R BS.775 does not clearly specify which approach to use. A pedantic, lawyerly reading would suggest that Figure 7 weakly advocates for approach (3).
In the end, the differences between these approaches probably don't matter that much in practice, because most useful LFE content will typically be below the crossover frequency anyway. This is why I usually recommend the simplest config (i.e. approach 1).
Last edit: Etienne Dechamps 2023-09-19
Done!
To be completely honest, I cant really hear these changes, but I trust you guys know your audio and I'm glad I learned something new!
Thank you again, you have been a massive help!
Looks good but it still has that 3 dB bump. But I guess it isn't that important if it sounds right.
Shouldnt that be taken care of by applying the filters twice? The Wiki article Etienne linked has a nice graph for explanation, but maybe I didnt understand it correctly.
That depends on the Q value. According to my Peace implementation you should use a value of 0.707. I'm not sure what default Q value Equalizer APO is using.
I see. EqualizerAPO uses 0.7071 by default, so all should be fine!
In general, when the Q value of a filter is not given, it is usually safe to assume by default that the filter follows a Butterworth characteristic, because Butterworth is the most boring, least surprising, most widely used filter characteristic (it is the fastest possible IIR filter that does not ripple, making it a good default choice for most applications). Butterworth filters are defined by Q=1/sqrt(2), i.e. 0.7071. It would therefore be reasonable to assume Equalizer APO uses a Q of 0.7071 by default, and it does.