[HN Gopher] DIY Digital Room Correction with Linux
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DIY Digital Room Correction with Linux
Author : pcr910303
Score : 63 points
Date : 2022-10-02 06:35 UTC (3 days ago)
(HTM) web link (th0ma5w.github.io)
(TXT) w3m dump (th0ma5w.github.io)
| scarecrowbob wrote:
| It's fun stuff to mess with, but one difficulty is that you can't
| really affect time-domain issues by modifying output frequencies.
|
| That is, there are likely both issues induced by the phase
| response of the speakers themselves as well as issues introduced
| by reflections in the room which will cause uneven frequency
| responses in these measurements. These issues are inherent in
| speaker systems and acoustic spaces.
|
| If you have a really resonant frequency in a room, notching that
| frequency can help, but then you're compromising that signal; a
| more typical solution is to address reflectivity in the space.
|
| And I hate to be a snob about mics, but yee, I do not like that
| specific mic-- of the many dozens of mics I have used it's
| memorably bad. And you don't need an expensive mic to do these
| measurements; there are a lot of ~$60 omni-directional
| measurement mics that work fine, as their low/mid frequency
| response is good enough for these tasks.
|
| So all in all: hooray for folks experimenting... once you start
| playing with frequency modification, start investigating phase
| response and modal reflections in rooms, as they are super
| interesting.
|
| Like, if you want to hear something really neat, put on a
| recording of a 120hz sine in a very reflective room, and you can
| walk around and hear the nulls and additions. And then you can
| find different frequencies and start to come to terms with the
| complexity there. Quite a fun exercise.
| bob1029 wrote:
| > It's fun stuff to mess with, but one difficulty is that you
| can't really affect time-domain issues by modifying output
| frequencies.
|
| PEQ can take you a surprising distance. Many perceivable issues
| can be substantially reduced by attenuating signal at
| problematic resonant frequencies. At no point ever (IMO) should
| PEQ be used to _boost_ the level of any frequency to make it
| more audible.
|
| FIR filters are where you can fix time-domain issues. The only
| problem is that, depending on the amount of filtering required,
| you may add quite a bit of latency to the signal. IIR filters
| (e.g. for your crossovers and such) are typically much lower
| latency approach. IIRC FIR filtering will also allow for you to
| correct for phase issues.
|
| At the end of the day, the room and its treatments are the most
| important part of the equation. The number of LFE radiators and
| their positions are probably #2. Everything else you can easily
| fix in software.
| m463 wrote:
| > And I hate to be a snob about mics
|
| I wonder if you just need a mic with a calibration file?
|
| this one is less than $25:
|
| https://smile.amazon.com/dp/B00ADR2B84
|
| and you can use the serial number to download a specific
| calibration file
| yamtaddle wrote:
| The biggest problem with home theater setups with surround sound,
| IME, is that no matter what you do most of the seats will get
| _very_ uneven sound (typically, one or more surround speakers
| being much louder than the others). The only fix is to have a
| larger space so the effective "sweet spot" covers more of your
| seating (think: an large-aisle-width space around a 3x2 seat
| configuration) but at that point you're looking at sacrificing a
| mid-sized living room worth of square footage for those 6 total
| viewing seats (and even more, if you scale up from there).
|
| [EDIT] In case it's not clear, the core problem is that for some
| seats, without a large buffer between the seating area and the
| speakers, the nearest surround speaker will be like 5-10% as far
| away as the farthest one. No amount of room-correction can help
| much for _most_ of the seats in such an arrangement. All you can
| do is use a larger space so you can put the speakers farther away
| without changing the size of the seating area (so, add empty
| buffer space around the seating area) so the difference in
| relative distance between the farthest and nearest surround
| speakers is smaller.
| JohnBooty wrote:
| It _cannot_ be understated how much better even modest /mediocre
| speakers can sound when their in-room response is corrected via
| DSP.
|
| (This is essentially why a lot of consumer electronics sound
| surprisingly good these days: onboard DSP is cheap and easy to
| implement. What a blessing!)
|
| Conversely, even "high end" speakers can sound bad if not dialed
| in correctly, especially if your room is rectangular and there
| are a lot of reflections.
| m463 wrote:
| > That seems like a reasonable thing to do, but there is a lot of
| pseudoscience in the audio world that will get you to buy
| platinum tipped styluses for depressing buttons on your remote.
|
| I think there are a LOT of these. I wish I knew when "reasonable"
| or "plausible" pan out.
| tuatoru wrote:
| Room EQ Wizard is your friend.
| eating555 wrote:
| Good to see the detailed write-up! Many others are just a brief
| guide to make you buy their service or product.
| edude03 wrote:
| I've been interested in this topic recently, I hate my AVR, but
| there isn't a better alternative. I've been hoping instead of an
| AVR I could pipe HDMI into my PC and run DIRAC there, but I've
| yet to find a capture card that can capture DTS/Atmos etc, so it
| hasn't been fruitful
| bob1029 wrote:
| I used to run an outboard FIR filter for my subwoofer with
| weights calculated (in part) using REW. I can't recall the actual
| DSP hardware model, but it was a pretty amazing effect when you
| toggled it on/off.
|
| Today, I just have a miniDSP that does basic crossover duty. I
| haven't bothered to do any parametric EQ or more advanced
| filtering in my new office yet. The passive acoustic treatments
| have done such wonders that I probably can't be now.
|
| I don't really like running anything above 80Hz through digital
| filters that I have constructed myself. I've had some success in
| a few areas, but you can instantly tell something isn't quite
| right with certain content.
| MartijnBraam wrote:
| I too did this exact thing with hardware instead of doing it in
| Linux. I used an t.racks DSP 4x4 Mini to apply my REW-measured
| room correction between my sound card and amp, also use it to
| generate the split for my subwoofer.
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