Yet another Hacker News

How I reverse engineered a commercial spatial audio effect

23 points epestr 2 hours ago 9 comments

clzerv 52 minutes ago | parent

While I appreciate the effort and talent to pull this off, I find the results to be awful. I call this kind of overblown sound processing "Bose barf" since pretty much all Bose audio sounds like this, and it just grates on my nerves. Now TVs, Bluetooth speakers, headphones, etc. all seem to perform this kind of aggressive audio processing to overcome the limits of super cheap tiny drivers. It's getting hard to find devices which have a more neutral sound profile. All this audio processing makes music sound like it's coming out of a garden hose duct taped to a 1950's grade school hall speaker. I can't understand the appeal.

epestr 39 minutes ago | parent

There's a subwoofer slider (around the icon) if the bass feels too heavy, and some songs require it to be toned down if it's already processed to be bass-boosted.

My Jabra headphones don't seem to apply any processing by default, and I prefer how they sound with the processing. If your headphones already boost bass or apply another effect, stacking the processing can be grating (which I've experienced when I record a video and play that through the daemon running).

I guess it's a matter of taste. I just like music sounding as though it's coming from a little farther away, and I suppose the bass-boost might be what you're finding unpleasant.

fwlr 36 minutes ago | parent

You’ll want to get something from Etymotic, they target the “precise and neutral” profile you’re after.

OP wants the `earwax` audio filter in ffmpeg.

epestr 18 minutes ago | parent

Thanks, I hadn't come across earwax before. I listened to the examples here: https://hhsprings.bitbucket.io/docs/programming/examples/ffm...

It sounds very close to what I was going for, and feels much softer to hear. I wasn't able to find anything similar earlier with any search engine or an LLM.

mrob 5 minutes ago | parent

Any headphone/earphone can be EQed to "precise and neutral" if the distortion is low enough. IEMs like the Etymotic IEMs often do well here, but if you dislike things inserted in your ear canal you might prefer planar magnetic headphones. These typically have lower distortion than dynamic drivers, especially in the bass. I have a set of HifiMan HE400se headphones, which used to be exceptionally good value before the price went up a lot recently.

To get the best possible results from equalization you need to do it by ear by comparison to a calibrated reference loudspeaker, but you can still get good results using other people's measurements. And there's no consensus what the best target curve is. Studio control rooms aren't anechoic chambers so "flat" won't necessarily give you the intended sound. You might find AutoEq useful:

https://autoeq.app/

I generally prefer no spatial processing, except in the case of 60s-style hard-panned stereo, which is intended for loudspeakers and does sound a lot better with the "earwax" filter or similar. "Precise and neutral" is a lot more difficult with loudspeakers, both because it's hard to keep distortion low when you're moving a lot of air, and because you have the off-axis response and room acoustics complicating things.

diydsp 24 minutes ago | parent

Same here wrt to Bose. I respect their tech and science but then they add a bogus aesthetic layer on top.

I think it is meant to make jazz sound good. The eq-d bass and attenuated mids make a standup bass more apparent and the piano and vocals more present.

But it made me start to wonder if I started hating my favorite band: I was packing up to move this weekend and stumbled on my CD collection. Many Stereolab CDs. I played them in my basic acoustic waveguide radio. A slick bookshelf I inherited and rarely use.

45 minutes later I was telling myself "god this music sucks...just agonizing repetition." Turns out yes the motorik bass is repetitive...but the other key point of the band is the gentle singing and intricate delicate synth and organ melodies...all foreclosed on by some evil twin combo of an audio eng and marketer overindexing in mid low bass.

andai 42 minutes ago | parent

Interesting article. I don't know much about sound processing but it reminded me of the Fruity Convolver in FL Studio, which can somehow apply the characteristics of one sound (an impulse?) to your audio stream. It has interesting effects built in, reverbs recorded in different unusual spaces, as well as guitar amps.

I would have liked to compare the audio clip from the beginning of the article, at the end too! Instead I had to record my own voice. And there doesn't seem to be a way to toggle the effect on and off? So it's a bit hard to get a sense of what it actually does.

This also reminds me of this cool mp3 from the 2000s — maybe it's on YouTube these days — called virtual barbershop, which was recorded with binaural microphones.

Edit: here she is! https://youtube.com/watch?v=IUDTlvagjJA

_joel 36 minutes ago | parent

Yes, it's called impulse response, used to capture convolutional reverbs, to model "real" sound stages like a large hall or what have you

epestr 24 minutes ago | parent

Yup, that would be an impulse response, and if the room acts as a linear (and time-invariant) filter, then you can easily figure all that out, and the write-up is basically about testing if it's so and how good the reconstruction is.

And there is a way to toggle it: the icon which is orange can be tapped on and off, and you can adjust the "bass" which is built in with the ring around it. Also, it's likely to have no effect on voice, more complex arrangements will have an audible difference.

There is similarly an example on Wikipedia too, which got me interested: https://en.wikipedia.org/wiki/File:BinauralPaper.ogg.