Comment by digitailor | Hacker News Reader

Comment by digitailor | Hacker News Reader

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Both your comments are heavyweight so I'm not trying to pick sides. (Sum your two perspectives and I think you're close to Ultimate Expert Comment.) I just want to mention that beat is talking about phase alignment between identical signals, which our perceptual network is incredibly sensitive to. Anyone who has ever done multi-mic recording can attest to the very real effect you can hear from lack of phase alignment, even if they have bronze ears. Even worse is if you duplicate two musical recordings and offset one, even by a tiny amount.

This is a critical aspect of crossovers- since they contain the same signal, any phase differences between the intersecting components are easy to pick up by the ear and very difficult to measure since it won't show up as a significant frequency or amplitude differential. In the highly acoustically sensitive area where the crossover occurs, the phase distortion between the two signals is hard to pin down but it's definitely there, it's easy to hear by A/Bing.

I mix on a multiple-monitor setup and the one that is most critical to me sounds like absolute garbage. However, it has a wonderfully "flat" response and allows you to get an idea of what proven aesthetically-unpleasing issues are present. It has no crossover. The goal is not to have perceived rumble, tinniness, or mud on any of the incredibly wide range of listening systems out there. I think this is what beat means by "musical"- flat speakers are actually not pleasant to the ears, but the most empirically useful.

The most famous secret of many respected mix engineers is the Auratone. Michael Jackson's "Bad" was mostly mixed on this little thing. It sounds like absolute garbage aesthetically but reveals more issues in a mix than anything else. It's like when you first saw things under a "blacklight" as a kid and got to see all the particulate matter covering everything, that you can't see with the naked eye.

Here's more about the Auratone. I hope my comment has helped to bridge this critical area of "musicality" vs. empiricism. http://www.trustmeimascientist.com/2012/02/06/auratone-avant...

Postscript- the listening environment is the most important aspect! Always! You can have the best mastering grade monitors on earth in an improperly treated room, and it's all for naught!

> I just want to mention that beat is talking about phase alignment between identical signals, which our perceptual network is incredibly sensitive to.

I wouldn't go that far. If you have two signals emitting from physically separate location and they are out of phase, you just get comb filtering. Is it audible? It can be, but its not the phase you're hearing, it's the drastic frequency notching in amplitude. More importantly, you're going to get comb filtering no matter what you do with a multi-speaker setup. Just move your head a couple inches out of the ideal sweet spot equidistance from each speaker and you'll have created an effective phase shift and get the same type of comb filtering. In other words even with a theoretically perfect pair of time aligned speakers with perfect cross-overs, you'll still get comb filtering if you take various measurements around the listening area. Just moving the mic 4 inches can have drastic effects on the measured response. Incidentally if you've ever seen someone taking a measurement with a sound meter and rhythmically moving the mic around in a strange fashion, they are doing that to try to even the effects of comb filtering.

> This is a critical aspect of crossovers- since they contain the same signal, any phase differences between the intersecting components are easy to pick up by the ear and very difficult to measure since it won't show up as a frequency or amplitude differential.

If you're taking a measurement in the crossover region and there is a phase shift between the drivers you most certainly will see an effect in amplitude as you'll have at least partial wave cancellation. You can certainly take measurements in locations what won't show this, but that is always true. You can take measurements of a perfectly time aligned speaker that make it look like it has phase issues too, if you put the mic in the right spot.

Likely the largest improvement you get from time alignment of the drivers in a multi-way speaker is the ability to control vertical lobe tilting, but you can 'fix' that issue with MTM layouts without time aligning the drivers as well.

I think what one might crudely call the "audiophile phase beef" is not about the comb-filtering that results from misalignment but the non-linear phase response of most crossovers, before the signal hits the air. Most act somewhat like an all-pass filter: a flat frequency response but varying delay across the frequency spectrum. This doesn't affect frequency sweeps or white noise, but results in impulses and clicks being smeared out in time or ringing a bit. The thought among some is that this is audible on percussion sounds, but experimental evidence is dubious as far as I can see. There are some references in the classic Douglas Self crossover book: http://books.google.co.uk/books?id=D9l6JWKKSzUC&lpg=SA2-PA14...

A similar argument which I think more people would agree with is that reflex-loading a speaker hurts the low-frequency group delay, the lack of which is one reason suggested for the supposed clarity of the classic NS10 monitor: http://www.soundonsound.com/sos/sep08/articles/yamahans10.ht...

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