Bass management innovativo - che ne pensate?
Con copia e incolla vi chiedo cosa pensate di questa recensione dell'Anthem D1 con riferimento alla gestione dei bassi.
Non ci ho capito molto, e volevo un vostro parere.
The real plum of the speaker setup is the "Room Resonance Filter", better known as the subwoofer single band parametric EQ we've been begging manufacturers for. It is a simple, straightforward tool with settings for center frequency, width, and attenuation. By design, it cannot provide a boost, only a cut. Every room in the world will have its share of nodes, but there is always that one that ruins your day. If it's deep down, you get a fat, burpy sound from your sub. If in the upper bass, it ends up drowning out the really deep notes. I won't bog down this review with the details of how to go about measuring your room and dialing in the filter. Suffice it to say, this one feature can make the difference between "ok bass" and a subwoofer really living up to its potential!
In the D1, you may specify a completely different speaker configuration (large/small etc) for "Music" (the first setup then becomes known as "Cinema"). Then, it is a simple matter of specifying in each input's configuration menu which speaker layout that input is to employ.
You may elect to send the surrounds from the 5.1 analog input to either the sides or rears. For any source you can elect to copy the surrounds to the rears, essentially using two speakers for each surround channel of 5.1 sources (including Pro Logic II).
At any time, using either the remote or the front panel, you can trim, in the range of -10dB/+10dB, any of the channels. This is separate from the master speaker level calibration and is retained by the playback mode. So if you decide you like the surrounds artificially high for Pro Logic II, you can boost them, and that boost will be retained. The exception is any and all THX modes: While you can trim a channel, it will always revert to 0 after the power cycle or even just the input cycle. This is correct and by (THX) design: When you press that THX button, part of the whole point of it is that you know the soundtrack is not being altered by any superfluous adjustments or processing.
Bass Management
And so it has come to this: Bass Management gets its own heading in a review. It probably should not be this complicated, but then again, I think about my days in the Boy Scouts.
Everyone had to have a Swiss Army Knife, and like everything else, they ranged from the mundane "knife and bottle opener", to models a full inch in width with saw, wrench, and tooth pick (tooth pick!?!), to name just a few of the items.
Truth is, there came a time, perhaps even just one time, that each of those tools came in handy. All except that tooth pick. As rough a bunch as we were, nobody dared to whip out their knife after a meal, extract the tooth pick, and go to work with it. Yet there it was, and remains today . . . just in case.
And so it goes with some of these advanced bass management features. Many we may never use, but if you are going to turn out the proverbial Swiss Army Knife of SSPs, you'd better have it all.
There are two "levels" of Bass Management in the D1. Taking the simple route, each pair of speakers and the center channel can be set Large or Small. "Small" crosses over that channel to the subwoofer (or large front speaker if there is no subwoofer) via the THX spec slopes of 2nd order high pass/4th order low pass. There is a selection of crossover frequency from 25 Hz to 160 Hz in 5 Hz increments.
The D1, like the AVM-20, gives you the option to use a variable phase control on the subwoofer. This sort of control is fairly common on subwoofers because prior to comprehensive time alignment in SSPs, this was the only way to "line things up" in terms of the in-room response of the sub/sat crossover. For the most part, it is a little outdated in that respect, but there may be cases where its a handy final tweak. Time Alignment delays the entire signal sent to the subwoofer (to correct for the distance it sits relative to the other speakers). What a variable phase control does is selectively apply a group delay to the subwoofer's output that's proportional to the implemented phase shift. Think of it as a delay only around the crossover frequency. This allows you to adjust the phase of the subwoofer relative to the output you're trying to match.
Academically speaking, if you have THX speakers, there should be no need for the phase control (the linear delay is all we need). In that scenario the electronic and acoustic slopes sum to be in phase. With non-THX speakers where the high-pass characteristics of the acoustic slopes of the loudspeaker itself don't fit into the crossover scenario, simple time-alignment doesn't guarantee the optimal phase relationship. In that situation, it may be beneficial to apply group delay (our aforementioned continuously variable phase control). While we still hope for the day when Anthem will provide a 4th order high pass option (at which point you need only set the crossover frequency about an octave above the speaker's -3dB point), until then, the phase control option might just be the thing to dial the subwoofer in.
Under Advanced Bass Management, the crossover frequency for each pair of speakers and the center can be different from one another. Somewhat counter intuitively, setting up a 5.1 or 7.1 system with a mix of crossover frequencies is not a sure bet to audio nirvana. In our essay "Miscellaneous Ramblings on Subwoofer Crossover Frequencies" we point out that a mix of crossover frequencies will leave the room with an uneven bass response from the various channels because only one low pass is applied to the subwoofer, a fact which will leave you with either holes in the response of some channels, or overlap between some channels and the subwoofer (or a combination of both).
Despite what you may have read on certain forums, Anthem's bass management is not "flawed" or "incorrect" in this regard. The slight holes or overlaps, created by fussing with a mixture of high pass frequencies in the D1, are at least smooth, like a tone control, and is the very reason Anthem gives you the ability to create holes and/or overlaps: The room itself and its effect on system frequency response are often more influential than a less than perfect crossover configuration. With some care, patience, and a great deal of expensive MLS type measuring equipment, it may in some rooms be possible to overcome some of the room's effect on the spectral response of the system as a whole by fudging the individual highpass points this way or that. We offer this up with the caveat that it is either the measuring equipment or the ear which should make the final call and not mere academics. A selection of high-pass points based solely on such things as speaker low frequency extension will almost assuredly not yield the best results. Beyond all that though, there is no "correct" alternative way of doing it. You cannot take a 60 Hz low-pass, an 80 Hz low-pass, and add them to an unfiltered LFE channel and expect to get anything remotely resembling the original soundtrack. Because we are talking about summing electrically, if a manufacturer went this route, you would end up with comb filtering of the subwoofer signal, plain and simple. You would "damage" the signal before it gets to the subwoofer, and the correct energy is no longer there to acoustically mate with the speakers in the room.
In the D1, Anthem now gives you the option to disable the low-pass normally applied to the LFE channel of 5.1 material. Actually, it's not really disabling it, rather it simply adds the LFE channel to the subwoofer signal after the low-pass is applied. In so doing though, you introduce the potential for phase response error (see above). It is for this very reason that the LFE channel is normally combined with all the other material destined for the low pass. Anthem tells us they play with the phase of the LFE channel to partially address these issues, and an impromptu sweep on that channel turned out nothing too odd, but it's not categorically correct. So why is this option even offered? The fact is, if you are going use an inordinately low crossover (say, 30 Hz) this is the only way to get the whole LFE channel. Your call.
To try and put a wrap on Advanced Bass Management, the standard default settings, the 'standard' way to do bass management, was established out of a whole lot of work by some very smart people who took a very comprehensive look at real world scenarios. The ability to customize to your heart's content is a powerful tool, but one capable of drastic steps backwards if not used judiciously.
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