[Tom_Bombadil]

Okay, there's always a lot of discussion on the bass management capabilities of every DVD-A and SACD player. But I'm trying to understand how much of a real problem this is.


I know that full range signals can be mixed into any of the channels and that most HT audio systems employ limited range speakers, at least in the surround channels. But wouldn't nearly all audio/recording engineers know this? How much deep bass is likely to be mixed into the center and/or surround channels?


If one has top quality, full range front L&R speakers, then isn't it likely that any deep bass that isn't directed into the LFE .1 channel is going to go to the fronts? And if so, wouldn't this largely negate concerns about bass management?


I can understand the concern if one has small satellite speakers all around. Or if some short-sighted recording engineering directed sub-40Hz material into the surround channels. But even if they did, like say the deep bass picked up from a orchestra from the mics used for the surround channels, as long as that bass was also going into the fronts, it shouldn't make much of a difference.


So if one had a good HT audio system with fronts that go down to 30, a center to 45-50, and surrounds to 50-60 - as found in many HT systems - is bass management all that essential using real world recordings?


Tom B.

 

[John Kotches]

Tom,


It really depends on the mixing engineer.


Steely Dan's Two Against Nature is my favorite example, where the Electric bass is mixed across all 5 main speakers, and some LFE to boot.


Regards,

 

[Tom_Bombadil]

Quote:

Originally posted by John Kotches Tom, It really depends on the mixing engineer. Steely Dan's Two Against Nature is my favorite example, where the Electric bass is mixed across all 5 main speakers, and some LFE to boot. Regards,

Does it move from speaker to speaker, or when it is in the surrounds, is it also in the fronts? That is, if the fronts are handling the deep bass (non-directional) from the bass guitar, then you won't be missing anything from the surrounds. But when the bass guitar moves up to higher frequencies (where the vast majority of electric bass resides), and moves into the directional bass frequencies, then most decent surrounds should be perfectly capable of handling it. This would be bass that I would not want to be rerouted into the subwoofer via bass management.


But if the engineer is routing a 32Hz note solely into the right surround channel, where it would be totally lost on most surround speakers, then that's a real problem - without bass management.


I'm trying to get a feel for when a particular system begins to have a real need for a sophisticated form of bass management (in the real world). I know if all speakers go down to 30, it isn't an issue. And if your surrounds only go down to 120, then it is an issue. But what about 50? 65?


Tom B.

 

[John Kotches]

Tom,


The bass doesn't move around within a track-- in some tracks it is in all 5 channels + LFE (the most obvious one is Two Against Nature). I tested this by disconnecting all but one speaker at a time and listening to the speaker.


You will also be "short" some bass if the surrounds can't handle the full range of the bass guitar -- but this disc in particular is mixed pretty bass heavy to begin with, and you might find that "lacking" bass is a good thing. I would guess you want something right around 40Hz, but even that assumes you won't listen to anything like pipe organs, etc.


I have to do some testing, I just replaced my surrounds and haven't played with the in-room response, I'm still tweaking for positioning.

As my system sits:

Mains (in room): 30-20K (spec 35-20k)

CC: ~ 40-20K (spec 45-20K)

Surrounds: 40-20K (spec only, haven't tested)


I use an ICBM with crossover points of 60 on Mains and Surrounds, and 80 on the CC. I get "tighter" bass response from the Subwoofer handling all the really deep stuff. My mains get a little "boomy" near the -3dB point.


I hope this helped you out.


Regards,

 

[Tom_Bombadil]

John,


That's interesting data. I'm trying to approach this from two perspectives. Primarily to develop a better understanding of the real-world factors on this topic, and secondarily for application in my own system.


If, in the real world, deep bass is not being mixed into the surround channels, this would lessen the need for sophisticated bass management. Likewise, if it is mixed into the surrounds, but also into the fronts, then the need for BA would be lessened, in the appropriate system.


For me personally, my fronts' -3dB point in my room is 27Hz and they are extremely clean and tight. When I'm running in two-channel stereo mode, I don't even use my sub. So I have no plans to divert any bass from them to my sub in multichannel, letting my sub handle only what is in the LFE channel. My surrounds go down into the mid-50s, so there is some bass that could be sent to the sub, but unless I become convinced it is essential to do this, I'm inclined to think that I could run DVD-A w/o bass management.


OTOH, the ICBM is a very cheap solution to all of this.


Tom B.

 

[John Kotches]

Tom,


I gave those numbers just to demonstrate the difference between spec and a real world room. I'm sure that the boominess is the implementation of the speaker, so I try to crossover to avoid that one troublesome issue.


I couldn't hear a degradation between bypass and crossover engaged on the ICBM, so even if you just used it as a cheap solution on the surrounds, that wouldn't be the end of the world


I hope this discussion has been of value to you.


Regards,