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Big Vs. Small (1 Viewer)

Brian AM

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Jan 9, 2002
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There is a huge post over at AVS forum (of which I'm not a member) on the merrits of setting your speaker size to small even when you have a full range speaker. From what I gather, some of those posting have an electronic engineering background, the consensous is that a high quality sub such as our beloved SVS is better able to produce bass than even quality full-range speakers. They claim that the small setting on the receiver/processor causes (depending on the cross over point) everything below 80hz to be sent to the sub. Where as in large mode only the LFE channel is being sent to the sub. Basically a hole is created between the lowest reaches of your full range speaker and the hz that occur in the LFE range. Now this is all a paraphrase and what I remember from reading last night.

My question is, if this theory is correct, then how does it play into DVD-A & SACD? Is the sub able to keep separate the bass for 5 channels and make it sound accurate? I am curious for those that are running DVD-A or SACD, is it worthwhile to spend the extra money on full-range speakers for your surround channels, or for that matter the mains, if everything below 80hz is going to be piped off to the sub? I am trying to decide on minis for my surrounds or just buy 2 sets of towers and use them as the surrounds. Anyone's experiences with multichannel audio would be greatly appreciated.
 

Dustin B

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Mar 10, 2001
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This is multi channel audio's big problem right now, no bass management. SACD and DVDA both require you to run 6 analog cables to your receiver or pre/pro. One for each of the 5 speakers and one for the sub. Which makes using your receiver or pre/pros bass managment impossible. Currently I think you have two options to get bass from your 5 speakers sent to the sub. If there are more someone please point them out.

One is buy a player that has bass management built in. Ie allows you to do the small large speaker settings on the player. I don't know of any off hand that implement good bass managament.

The second is the ICBM from Outlaw audio. You run those 6 cables first through the ICBM and then to the receiver or pre/pro. It then allows you to adjust crossover points on all the channels.

I remember seeing recently that DVDA has finally decided on a format to get the audio info to your receiver or pre/pro in digital form. Firewire. When this becomes available then proper bass management of DVDA will become much easier.
 

StephenL

Second Unit
Joined
Nov 21, 2000
Messages
341
They claim that the small setting on the receiver/processor causes (depending on the cross over point) everything below 80hz to be sent to the sub.
The crossover is not a brick wall. The THX crossover has a high-pass filter frequency response of 12 dB/octive below the -3 dB point of 80 Hz and a low-pass (subwoofer output) frequency response of 24 dB/octive above the -6 dB point of 80 Hz. In other words, the output to the main speakers is down 12 dB at 40 Hz. The THX crossover is designed to work with main speakers that are also down 3 dB at 80 Hz and rolling off at 12 dB/octive. The combined response of the high-pass filter and main speakers is 24 dB/octive below the -6 dB point of 80 Hz, so the high-pass and low-pass response is symmetrical. In theory, this design keeps the main speakers and subwoofer in phase and provides a relatively flat frequency response. These articles explain the THX crossover:
http://www.soundandvisionmag.com/Bu...sp?ArticleID=66
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The M&K BMC 5.1, similar to the Outlaw Audio ICBM, provides bass management for DVD-A and SACD analog outputs. The new Pioneer Elite VSX-49TX receiver provides bass management for its multichannel analog input.
 

Brian AM

Stunt Coordinator
Joined
Jan 9, 2002
Messages
86
Let me see if I am grasping the concept... If you have 5 full-range speakers then you do not need an ICBM? but using "minis" in the rear or center would necessitate the use of an ICBM when listening to DVD-A or SACD. Correct?
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
Depends on the DVDA or SACD disc. Most, yes. Something synthesized really low or something like the 1812 overture, no. Most good full range towers can make it down to 30hz. Almost none can make it down to 20hz properly. There are a reasonable number of subs that can get down there though.
 

MatthewJ S

Supporting Actor
Joined
Feb 27, 2001
Messages
584
I have come to believe, through a lot of experiance and implementation, that employing a crossover point (ussually a steep one) ussually takes a little load off both the amp and the speakers. This being said, I don't much like using 80hz but rather prefer a somewhat lower point...I think that there is enough to be gained from the "tactile" sensations off one's main speakers say down to around 50-60hz and most subs do better playing a more limited freq.(especcially if they are "tuned" specifically lower). I always have someone bring up the theory that a speaker should be able to play flat one full octave below the crossover point selected,however, I don't feel(or haven't in practice heard) the need for this .A speaker that plays well down to 40hz should sound better when not asked to do much below 50hz...an amp that has good power when driving 5(6 or 7) speakers full range will have more when only driving limited range...perhaps this is why companies like

marantz and onkyo(etc) are using less powerfull power supplies...many buyers of budjet receivers will likely run them in small mode anyway...
 

Bob_A

Supporting Actor
Joined
Jul 30, 2000
Messages
876
From what I have seen...some people seem to find that bass information below 80Hz reproduced from both main channels (as opposed to bass information below 80Hz reproduced only from a corner-loaded external sub) may lead to a more coherent and desireable soundstage...but I cannot say for sure because I have not been able to use an external sub in my setup.
 

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