Surrounding Subs - Picking Up on Something gel asked

[Benedict_Arnold]

Do you think it's possible to drive, say, four subs, FL, FR, BL and BR, off the pre-amp out RCA sockets of a receiver? AFAIK the RCA sockets don't draw much current, if any, but just supply signal voltages, so it shouldn't harm the receiver or its internally amplified power output. If I wired those up to powered subs around my room, could I get the "oomphs" to track like surround sound?

 

[spiny norman]

I guess it's electrically possible, but you'd need to run all those channels 'full range' (ie as if no subs were being used) and then 'dial in' the subs to slot in underneath the speakers you're using for those channel. And if you're doing that you won't be getting the dedicated LFE channel on discs processed seperately, but mixed in with the main channels, which might not sound as good as having a dedicated sub for that channel.

Unless you're thinking of using one mega-sub for the LFE, and smaller subs on all the main channels. Oh, and don't forget you'll also need a sub for the centre channel.

Whether it will sound any good or just an unholy mess, who knows? With the low frequencies mixed into all channels and thus being handled by the main speakers on those channels, there's an argument that channel steering might be diminished, not enhanced.

 

[Benedict_Arnold]

Yeah, but my main speakers go all the way down to 35 Hz (realistically 90 hz before the response drops off like a cliff edge) anyway, so if I cut off the subs at about 90 Hz and twiddle the knobs a bit there won't be much audible cross-over, right?

And yes, in theory, I could add subs for all seven in-wall channels, and the in-ceilign ones. I have predicted next year's latest and greatest will be in-floor speakers, so I could add those in time too....

However, I think four tracking round the room should be enough, seeing as we're supposed to not be able to track the origins of low frequency sounds anyway.

And what is LFE exactly anyway? It doesn't make the floors shake watching San Andreas or the walls shake watching the latest Blow, Sorry Die-Hard... Sounds, sorry, appears would be a better word in the context, like a "whiter than white" thing to me.

My HT room is wired for four subs with in-wall cables already, so that pain is already taken care of. Perhaps I'll play around if / when I finally get four subs and report back.

 

[spiny norman]

Yeah, but my main speakers go all the way down to 35 Hz (realistically 90 hz before the response drops off like a cliff edge) anyway, so if I cut off the subs at about 90 Hz and twiddle the knobs a bit there won't be much audible cross-over, right?

Given the omnidirectional dispersion of most subs, there could be all kinds of patterns of reinforcement and cancellation all over the room. As I said, the results will be unpredictable, but I'm sure you'll have a giggle trying it.

 

[ellisdj]

using 4 subs will be the opposite - placed correctly they will cancel many of the room modal problems.

This is about 80% predictable in terms of performance as well - see REW Room Sim

 

[Benedict_Arnold]

using 4 subs will be the opposite - placed correctly they will cancel many of the room modal problems.

This is about 80% predictable in terms of performance as well - see REW Room Sim

Interesting software. UI had a play and I got the attached for my media room. A big drop off at 60 Hz and then up and down like the Swiss Alps between 80 and 200 Hz. The 60 Hz I can understand. The speed of sound is 1126 ft/ sec. So for a sound wave to travel 19 feet takes 19/1126 = 0.016 seconds, corresponding to the natural frequency of the room of 1/ 0.016 = 60 Hz. Not much I can do about that.

Are there software packages for analysing entire surround sound setups? I quite fancy doing media rooms as a new part time money maker, and I've already got the CAD tools for room layouts, wiring, etc. I just need to get the acoustic part organized.