2nd subwoofer question

michael.redfern

Active Member
Ok, before anyone has a go, I've read the threads on using two subs on the same channel (.1) and the problems of colocation etc, but this is a different question. Promise. :)

I've been interested in adding a sub in parallel with my centre channel since hearing one set up in the REL room at the Manchester show a couple of years ago. They were showing the classic scene from the end of Open Range, and the weight of the gunfire was stupendous.

My current setup is in my footer and all speakers are set to small, with all bass to my Monolith. So, my thinking would be that I could add a second, slightly smaller sub (say an XLS200 or new XLS300) using my amp's centre channel output (either low level, or using the neutrik and the centre channel speaker output), and changing the centre channel to large. I think that thru filtering, I could roll off the centre sub where the centre speaker starts to give up.

What are anyone's thoughts on this? Does anyone have a similar setup at home? Would I run into the same sort of problems as a more standard 2 sub setup (I can't see that I would as the two subs would be playing different channels)? :confused:

All thoughts welcome folks! Cheers. :thumbsup:
 

Member 639844

Former Advertiser
Well I dont know alot about using 2 subs, but if your center speaker is small and you set your output as though it was big, then I'd have thought you risk dammaging your center speaker, or at least making the sound worse.
My thought is, that although your sub is in there to help, the signal going to your center speaker will be to much for it and cause distortion or dammage.

But if you want to ty it out, why not try doing that with the sub you have, unplug your monolith and listen to the system without the sub, then wire it into your center speaker and see how much off a difference it makes to the sound, just being careful not to push it too hard too fast. If you notice a good change then get to your local dealership with the results in hand and see what they think of the idea.
 

Member 96948

Distinguished Member
I can't see what the difference is.

With the center set to small, it's bass IS going through a sub anyway - It's just doing it through the far more precise route of a low level crossover, which of course will suck less power from the center channel amp.

The key thing I learned whilst messing around with two subs, was......

.... buy a bigger better sub. Open Range was, excuse the expression, effing awsome through the Ultra.

Russell
 

badbob

Banned
If you really want to do this, ideally the sub should have a high pass filter. Set to large.

AV amp centre out--->Sub--->Centre

So the sub will pass on 50hz+, and then only play 50hz and under (in this case centre has F3 of 50hz)

I'm not sure if the amplifier will stuggle, although full-range signal, there is filtering, the sub takes no power from the amp :confused:
 

Sniper

Active Member
... but as russ.will said - what's the point ... you're already bass managed on the centre if it's set to small (which with a monolith it should!) .. so i don't get it .... If the monolith doesn't cut it ...you "need" a better sub!
 

leon

Active Member
im using 7.5 system i have a 9" sub built into the centre and its amazing there is so much more detail .. i didnt think a centre could be that good ..
http://www.definitivetech.com/loudspeakers/clr/clr.html#3000

try and get a demo some people say 5 subs is to much but when they are balanced and calibrated and not to load the the films come alive
 

Nimby

Distinguished Member
There is certainly no shortage of bass in the Center channel.
I checked it once with my SVS after reading a similar thread.
Not sure I like the idea of daisy chaining the Center speaker off a sub.
The onboard crossovers aren't necessarily of the highest quality.
Proof of the pudding is to try it.
Get a bigger subwoofer if you want awesome.
Have I ever mentioned IB subs around here?
They do awesome quite nicely. :)
 

Member 96948

Distinguished Member
im using 7.5 system i have a 9" sub built into the centre and its amazing there is so much more detail .. i didnt think a centre could be that good ..
http://www.definitivetech.com/loudspeakers/clr/clr.html#3000

try and get a demo some people say 5 subs is to much but when they are balanced and calibrated and not to load the the films come alive
When you say "7.5" system, I take it you are running 5 channels with an active bass 'driver' plus two without, but I'm slightly confused as to what audio standard provides the additional .4 LFE soundtracks.:confused:

Even the most advanced audio codec currently only supplies (a possible) .2 LFE soundtracks, but I'd be interested to hear how you've rerouted the single current .1 LFE soundtrack to provide 5 individual bass sources without cancellation issues.

BTW, as you are running five 50L, 9" subs where are you getting the extra octave that one 100L 12" sub could supply?

Russell
 

Member 96948

Distinguished Member
Do you have a delivery date for your Ultra13 yet? :devil:
An easy assumption to make if you think it's the only interesting sub in the offing.;)

Further more, I'm still considering a pair of DIY 15" sealed servos from Rythmik Audio, but with an offer on this house under consideration and the loss of the house we had placed on offer on, all bets are off for the moment.

Russell
 

michael.redfern

Active Member
Thanks for the replies so far guys. All interesting points.

I'm slightly confused as to what audio standard provides the additional .4 LFE soundtracks.:confused:

Even the most advanced audio codec currently only supplies (a possible) .2 LFE soundtracks, but I'd be interested to hear how you've rerouted the single current .1 LFE soundtrack to provide 5 individual bass sources without cancellation issues.

Well, I based my original question on the fact that DD and DTS provide 5 full range channels and a dedicated .1 and so I would imagine that the optimum way to reproduce this would be to use 5 full range speakers, and a sub. However, since my centre speaker isn't full range, I rereoute the lowest frequencies to the sub via the amp (as we probably all do), thus the sub gets the .1 track, and it has the lowest range from the other 5 speakers too. This is a compromise.

By adding a dedicated sub to the centre channel and setting it to large, surely I am making it into a full range channel? :confused:

I guess that the 7.5 poster above is saying that he runs 5 of hius 7 channels effectively full range, though in the strictest terms this is really a 7.0 system if none of the subs is producing the LFE track.
 

AngelEyes

Distinguished Member
In a lot of cases running your system THX* stylee gives the best performance, even with stonking full range speakers all round. Lots of bass sources calls for a LOT of setup and EQ to get an even response. Personally I can't see the point when putting your money into one good sub would almost always sound better (setup correctly of course :rolleyes:)

*Set all speakers to small, turn off crossover on sub, set subwoofer crossover on amp to 80hz-ish.

Adam
 

Sniper

Active Member
... DIY 15" sealed servos from Rythmik Audio...

Had a look that their site - interesting! Thanks!

How does 1 of em' compare to anything "familiar"?
 

Member 96948

Distinguished Member
Well, I based my original question on the fact that DD and DTS provide 5 full range channels and a dedicated .1 and so I would imagine that the optimum way to reproduce this would be to use 5 full range speakers, and a sub. However, since my centre speaker isn't full range, I rereoute the lowest frequencies to the sub via the amp (as we probably all do), thus the sub gets the .1 track, and it has the lowest range from the other 5 speakers too. This is a compromise.
It's not in terms of minimising in room EQ issues and multiple source cancellations across a number of listening positions. Although my own fiddling showed the usefulness of multiple subs to be slightly equivocal, I wouldn't rule it out for larger rooms. Thing is, unless you've reached the ceiling of performance possible from a single sub, I concluded 2 subs can be bettered by one better one.

There is a worthwhile read here on minimising room interactions with multiple subs. The optimal configurations (using a practical number of subwoofers) has nothing to do with the recommended DD/THX speaker placements, suggesting that sub-bass from the speakers positions is not ideal. That said, the one position that is coincident with a likely speaker position is the arrangement of the sub place centrally on the front wall. Make of that what you will.:)

By adding a dedicated sub to the centre channel and setting it to large, surely I am making it into a full range channel? :confused:
You are, but you're not gaining anything that's not being reproduced already via the amps bass management redirection.

I guess that the 7.5 poster above is saying that he runs 5 of hius 7 channels effectively full range, though in the strictest terms this is really a 7.0 system if none of the subs is producing the LFE track.
That's the way I see it, although I have recently seen it suggested that some modern receivers can reroute the LFE soundtrack. As to whether this entails any sort of DRC or not, I'm not sure nor am I really interested - I do not intend to run subless.:eek::nono:

Russell
 

michael.redfern

Active Member
There is a worthwhile read here on minimising room interactions with multiple subs.

One of the key assumptions in the paper seems to be that they are using several subwoofers for the single LFE channel. I would be using a subwoofer for each of two different channels. They therefore would presumably not be concurrently producing the same output, and would presumably have fewer interactions. Or am I again missing something.

I may have to try borrowing one and see how it works out.

Tbh, I'm just a curious soandso, and like a good debate. :thumbsup:
 

Nimby

Distinguished Member
Widely spaced bass transducers will tend to produce cancellation and reinforcement effects at particular frequencies depending on their physical spacing. These effect may be ameliorated by the subwoofers physical position within the room and may vary dependent on the size of the room.

I have produced a deep movable trough, variable in frequency, depending on the phase setting of only one subwoofer of a pair. The subs were about 8 feet apart.

REW is a useful software tool for quickly checking these effects.

With patience and care it may be possible to reduce room modes by position and phase adjustment of multiple transducers.
 

Member 96948

Distinguished Member
Tbh, I'm just a curious soandso, and like a good debate. :thumbsup:
A mass debate is always a welcome break from the hundrum.:)

So, as you're up for it, can I ask you the following;

Why will redirecting your center's bass to an additional inferior sub be better than redirecting it to the one sizeable sub you already have?

Using Open Range as the example, what about the gun shots could be improved by routing that bass away from the Monolith to a smaller alternative that will sacrifice either depth or headroom, or likely, both?:eek:

Russell
 

michael.redfern

Active Member
Cool, let's debate! :devil:

Why will redirecting your center's bass to an additional inferior sub be better than redirecting it to the one sizeable sub you already have?

I'm not necessarily saying that it categorically will be better, just summising.

Using Open Range as the example, what about the gun shots could be improved by routing that bass away from the Monolith to a smaller alternative that will sacrifice either depth or headroom, or likely, both?:eek:

Well, that's part of what I want to work out. I was assuming that the soundtrack contains bass on both the centre channel track and the LFE track for each shot, and that using a dedicated speaker for each of these component parts would be an improvement. I mean, it would be considered ridiculous to redirect my centre speaker to my main speakers just because they were better quality, right?
 

Sniper

Active Member
I mean, it would be considered ridiculous to redirect my centre speaker to my main speakers just because they were better quality, right?

That's a can of worms you don't want to open! There are arguments in favour of that - no comment!

As for this topic - I can see your point - but i'm still of the opinion that redirecting non-directional bass to a superior single unit is the better option! So if you had the budget for a sub per channel - sum that budget and get a Genelec HTS6 :smashin:
 

AngelEyes

Distinguished Member
Or an IB for a fraction of the price and takes up no space in your room. ;)

What's an IB, I never heard you mention them before?
 

Nimby

Distinguished Member
Where have you been? :D

A true infinite baffle subwoofer uses a room surface as a baffle to avoid out of phase cancellation effects. The rear space (the IB enclosure) can be the loft, underfloor crawl space or even another room. By using large, multiple drivers it offers very low distortion, extension to very low frequencies indeed, incredible dynamics, no coloration and very high sound levels when desired. It is usually inexpensive to build compared with commercial subwoofers yet leaves all of them far behind on performance.

Dare I suggest that you follow my signature link for many illustrated examples? ;)
 

AngelEyes

Distinguished Member
note to self: must insert sarcastic smilies more often ;)
 

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