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In Reply to: Do you find that your mains and center channel need a sub with a 5.1 setup? posted by Lonely Raven on March 27, 2000 at 09:51:03:
From the opposite end of the spectrum: I like to joke around and say that the only thing missing from the audio portion of my HT setup is one more sub. Currently, I only have 5. Having played around quite a bit, yes, there is significant bass contained in the center channel, IMO. A center channel sub can add significantly to your system, if you like to hit "reference" bass levels.I'm going to pick on one fairly well known sub: the Bag End InfraSub, which claims a flat response down to 8Hz. Reading that spec sheet, my goodness, who would ever need anything else? The problem comes in that the Bag End will only output a flat response at about 90dB. Reference level is 110dB at the listening position, according to THX standards. So the Bag End comes up very short, although it's published specs would lead you to believe otherwise. Their sub simply compresses way too much to be a real contender in HT bass.
Bag End is not alone, although they are one of the worst.
Now consider what you're asking a sub in a HT setup to do for the LFE channel: produce 110dB SPL, at the listening position, at 20Hz or so. Take a sub that is truly capable of producing 110dB at 20Hz; assume that it is ideally placed in the room to assure that response. Unless you're sitting on top of that sub, chances are you'll never come close to 100dB.
Remember: that's just the LFE channel.
Now, let's say that you have one sub, and all your bass is routed to that sub. That means that in addition to the LFE demands, that one sub has to churn out other channel's bass; let's generously say that amounts to 10dB.
In this scenario, in order to realistically achieve reference level, you'll need a sub capable of 120dB+ at 20 Hz.
Good luck finding *that* sub in the marketplace.
What does adding a sub to the center channel do? Well, if nothing else, it offloads some work from the LFE sub. This makes your system more dynamic, and helps to insure that the LFE sub isn't driven to compression.Currently, I have 2 Polk SRT subs and a Sunfire Sub devoted to Front L+R duties, and reroute center + LFE bass to the Front L+R. An additional pair of subs for the surround channels round things out. This is a system with a very strong bottom end, one that can produce reference levels at the listening position. There's a scene in Aliens where the bad critters knock at the airlock door to the lab; that "knocking" produces enough bass in my HT to shake the floor and everything attached to it.
I have had the Sunfire setup as the LFE sub, and re-routed center channel bass to it. The result: somewhat lacking in dynamics. A slight sense of compression, of strain during peak level passages.
I've also had the Sunfire setup as a center channel sub; that sounded great, IMO, and resulted in an extremely dynamic, cohesive front soundstage. The only thing that I felt was lacking was the very low end on certain passages; while the Polk SRT subs are super, they roll off below 20Hz, and adding the Sunfire in reinforces that really deep bottom end nicely. That was done before I built a dedicated 2 channel listening room, so I may go back to using the Sunfire as a center channel sub someday.
The bottom line: don't be afraid to play with different configurations. Yes, it can be a lot of work getting the subs to play nice together. Yes, your family and friends will treat you differently. But if you really want top-flight sound, it's the only way to go.
A final note: it is possible to build a sub that will produce adequate bass to meet the SPL requirement for all channels and then some. However, IMO, not having bass on the surround channels is a huge mistake. Although many claim that bass is omni-directional, there's nothing like bass that wraps around you from all directions. It really contributes very strongly to a seamless soundstage that places you in the center of the action.
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Follow Ups
- Re: Look out, here comes Bubba! (somewhat long) - Bob Wanamaker 17:25:14 03/27/00 (1)
- Good comments... - RichardH 16:36:26 03/28/00 (0)
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