From 8adb3bee228c9b16de441033bd26350e18d204e4 Mon Sep 17 00:00:00 2001 From: Thomas Glanzmann Date: Thu, 10 Mar 2022 19:06:05 +0100 Subject: [PATCH 1/1] more notes --- doc/notes.txt | 107 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) diff --git a/doc/notes.txt b/doc/notes.txt index 379bc62..af7a0c6 100644 --- a/doc/notes.txt +++ b/doc/notes.txt @@ -262,3 +262,110 @@ grub-install --removable /boot/efi exit, umounted everything and rebooted. ------------------------------------------------------------------------------------------------------------- +12:41 < chadmed> https://gist.github.com/chadmed/2c772c8fdac8280cb17846388203a213 <- some notes on the speaker system in the j314s, and an asound.conf that makes them sound... okay-ish for now + +## BEGIN NOTES ## + +# HOUSEKEEPING +# All testing conducted with channels set to 40% in alsamixer, +# with no amp gain. + +# Do NOT try to play sound with the speakers set to 100% in alsamixer, +# you will fry the cones! + +# DRIVER MAPPINGS/ALSA QUIRKS +# The speaker array as set up by the ASoC driver maps like +# this on a J314s: +# 0: Left Woofer 1 +# 1: Right Woofer 1 +# 2: Left Tweeter +# 3: Right Tweeter +# 4: Left (Sub)Woofer 2 +# 5: Right (Sub)Woofer 2 + +# ALSA sets up the speaker array on the J314s as a 4.0 surround system, +# with the RL and RR channels duplicated across the woofers like this: +# 2: Front Left +# 3: Front Right +# 0: Rear Left +# 1: Rear Right +# 4: Rear Left +# 5: Rear Right + +# Obviously this is not correct, but for us it does not matter, since +# we can just tell ALSA to route FL and FR to all drivers, presenting +# it to the rest of userspace as a stereo device. Surround sources +# are downmixed appropriately. + +# SOUND CHECK +# Testing reveals that drivers 4 and 5 are likely +# only there to help with bass and sub bass. They +# are extremely bad at reproducing frequencies above +# ~500Hz, and even with the help of the tweeters sound +# rough/deep fried in the mids. Drivers 0 and 1 are obviously +# intended to be the main woofers in the array. + +# If we weren't intending to mimic whatever macOS does, my ear-only +# testing would have me setting up a xover network like this: + +# Freq Range (Hz) | Drivers +# 0-300 | 0 1 4 5 +# 300-6500 | 0 1 +# 6500-20000 | 2 3 + +# Figures based on typical {LP,BP,HP}F rolloff characteristics. + +# Using all 4 woofers below 300Hz moves more air than just using the +# (sub)woofers alone. 3-way loudspeakers work like this conventionally. + +# The ttable in the j314s-array pcm device tries to compensate for the lack of +# EQ right now by greatly reducing the volume of 4 and 5, and slightly reducing +# the volume of 0 and 1 relative to 2 and 3. I have found this gives an acceptably +# clear sound without being too bright or losing too much out of the mids. Bass is +# nonexistent, though I suspect this is just because we have not applied appropriate +# correction to overcome the machine's housing yet. I will not be applying EQ or filtering +# in ALSA using plugins even in the interim because +# a) it's deprecated +# b) it introduces overhead and chews up CPU time + +# FIRs can be applied to a 6 channel slave PCM which would then feed the routing table +# PCM configured below with all coefficients set to 1 + +## END NOTES ## + +# Create a six channel slave for the audio array +pcm_slave.outputs { + pcm "hw:0,0" + channels 6 +} + + +# We need to map L and R to the correct drivers. We can use +# the coefficients in ttable to roughly tune the sound profile. +pcm.j314s-array { + type route + slave outputs + ttable { + 0.0 = 0.65 + 0.2 = 1 + 0.4 = 0.3 + 1.1 = 0.65 + 1.3 = 1 + 1.5 = 0.3 + } +} + + +# Set up a plug and ctl interface for ALSA defaults +# XXX: Does not work for PipeWire, but does work for JACK +# and PulseAudio +pcm.!default { + type plug + slave.pcm j314s-array +} + +ctl.!default { + type hw + card 0 +} +------------------------------------------------------------------------------------------------- -- 2.39.5