While we're talking about this, do you guys think its useful to cross-over the bass from the main channels for video playback?
I think my old AVR used to do that, but of course my new USB DAC doesn't - so should i tell MC to do it? I think it automatically does it when the input does not contain a LFE channel, but not if it does - so should I tell Room Correction to do it?
I would say (from my perspective) that unless your mains are full range or close to it, you'd almost certainly want to cross the bass over, but TheLion is correct, it can be hard to do correctly without a calibrated microphone. And doing it incorrectly can definitely be worse than not doing it. If you want to go down that road, I've spent a lot of time setting up active crossovers and can offer some suggestions, (I'm currently working on a "guide" more or less on this subject, but I'm at least a few months out from finishing it).
Talking about XOs in MC19: Before Matt's tragic accident there has been some discussion of making digital XOs more flexible. It would be really of great benefit to provide e.g. the option of different XO filters: Butterworth is what MC uses now (it would be great to have the option of uneven filter orders with that - e.g. 18 and 36)
Linkwitz-Riley (this is the most often used XO - atm we have to stack 2 Butterworth filters to accomplish LR)
Bessel
perhaps even Neville-Thiele
Is that something you would be able to look into, or is it a topic for Matt's return? Thanks so much!
I would also support this 100%, I've been advocating for this for a little while because JRiver's stock filters don't actually sum very nicely out of the box. That's no fault of JRiver's, it's a fault of even-order butterworth filters, which are the ones built into MC (with the exception of the 6dB filter). As TheLion said, we can work around by cascading two to get Linkwitz-Riley type filters, but someone just trying to use MC for Bass management isn't going to know they need to do that, and we can't currently create certain common or popular filter types (3rd order butterworth, bessel, etc.).
The problem is related to the correlated sound summing problem we discussed above. A butterworth filter is only -3dB at the crossover point, but when you divide a signal using symmetrical even-order butterworth filters, you're dividing a perfectly correlated signal, so the two channels sum 6dB at the crossover freqeuncy. This means that symmetrical even-order butterworths create a +3dB lump at the crossover point, or, worse yet, in the case of 2nd order butterworths (12dB), they create a huge null until you flip the polarity of one of the channels, and then they sum +3dB.
Odd-order butterworth filters (6dB, 18dB, etc.) don't have the same problem: they have partial cancellation due to phase rotation (sometimes called "summing in quadrature"), leading to a more or less flat sum. But the only odd-order option we currently have is 1st order (6dB) which is too shallow to be very useful in most setups. Linkwitz-Riley filters don't have the summing problem because they are -6dB at the crossover frequency, and are more likely to work correctly "out of the box." Here's a comparison chart from the wiki:
http://en.wikipedia.org/wiki/File:Linkwitz_vs_Butterworth.svgNone of this is urgent, since we have a workaround, but I've always felt that (taking the long view) it was worth providing more options and maybe changing the default to linkwitz-riley, because casual users just trying to get bass management set up would be likely to wind up with wacky frequency response ripples using the built in filters. I was actually planning to incorporate some discussion of this in my (still in development) bi-amping/active crossover/subwoofer measurement guide, as it would be easy to illustrate the problems and the ups and downs of different filter types in that context.
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Topic: LFE handling of Video Files (Read 10255 times)