sub for surround channels??

[mitsubishimania]

Has anyone ever used a sub for their surround channels? Currently I run Def Tech speakers with subs for C/L/R and the smaller BP1.2x in the rear. I've been considering a small sub to increase mid-bass capability in the surround channels. I don't run a separate subwoofer (LFE) at this point, but plan to in the future with a crossover point around 40hz. Any thoughts?

 

[apatel25314]

no because a good sub cannot be localized

 

[mitsubishimania]

I was thinking more for mid-bass than sub-bass. Say 40hz up to 120hz. The BP1.2x use a 4 1/2" midrange driver and they aren't very strong in the mid-bass region.

 

[Dolby CP-200]

Has for independent use I have toyed with this many years ago, but due only having a single smaller 12” sub bass to do this it was a waste of time. The subs need to be placed over a wide range of the rear of the room for this to work correctly.

When seating too close to it, it was great wow, but it’s not often films use a great deal of sub bass extension that goes down between 20Hz and 40Hz.

If one person is seated off from where the rear surround sub bass is placed the effect will be slightly giving away, even if I set the x-over down to 40Hz I was perceiving it to one side, yes I was hearing to one side, I guess that would be the way the bass is refection of the wall and creating a tone that was more to one side of my ear!

So at least three or four would be needed and spaced out behind the rear close to the wall for excellent results.

At the present I use an audio mixer to send all, the low end from the surround channel to the sub bass extension that is placed at the front, films like Star Trek II, Planet of the Apes, Apollo 13, Star Wars episode 1, Terminator 3, those are just some that I could think of.

I would have to start a thread designed to find the most demanding films with deep low end on the surrounds.

 

[no. 5]

I was thinking more for mid-bass than sub-bass. Say 40hz up to 120hz. The BP1.2x use a 4 1/2" midrange driver and they aren't very strong in the mid-bass region.

so it would be more of a 'bass module' than a subwoofer?
placed directly behind your listening postion, perhaps. but it would probably be better to just buy surrounds that have largre drivers.

 

[Dolby CP-200]

no. 5

But how many do you think would stick these in there home cinema. Now than, with a frequency response down to 40hz it’s more than enough I would say four on the back wall and three on the sidewalls that should do it.

JBL 8340 THX approved.

 

[Seth=L]

You guys are forgetting the biggest problem, cancelations. Unless he sets the main sub to receive lower than 40hz only and the bass module for the surrounds only does 40-120hz it wouldn't be very practical considering lots of LFE is in the 60hz range the sub wouldn't play them and the surrounds certainly wouldn't receive them, so now you have dropouts. In most systems you are best off setting all speakers to small anyway and running the receiver's x-over around 80hz. Defeat the x-over on the sub or turn the x-over on the sub completely clockwise. The additional sub for surrounds isn't necessary, practical, or good for sound enhancement.

 

[Dolby CP-200]

Biggest problem with most AVR or AVP that that a fixed x-over is (sub bass masking)!

 

[Seth=L]

Biggest problem with most AVR or AVP that that a fixed x-over is (sub bass masking)!

Please Explain.

 

[Dolby CP-200]

Seth=L

It’s where the output from the surround exceeds Dr. David Marcus death in Star Trek III the Search for Spock where a Klingon knifes him in the chest!

During the presentation at the CIC Empire Leicester square back in 1989 via the JBL THX sound system the whole presence of the scenes impact was flawless! Now it’s something I could do easy at home today.

When I brought my Kenwood KRF-X9050D THX select I noticed this god almighty rumbling that made the above scene disappear! It only took me a few weeks to figure it out and to hatch out a solution that would make it play like I heard and felt it at the Empire.

The deal is to use separate outputs from the all channels and feed them to either separate x-over units and then input there signal though an audio mixer where you have total control over the sub bass and LFE.1 as well.

So if you have Star Trek III play the above scene as described I’ll bet you £1.00 you can’t feel the low that stabs him in the chest that’s down to 40Hz! Because it’s been masked by the output from the surround which is exceeding the center channel only, now if you had huge cinema PA JBL 4675-A like the Empire had, now than.

Play around with this scene I’ve got it down to an art now.

 

[no. 5]

Unless he sets the main sub to receive lower than 40hz only and the bass module for the surrounds only does 40-120hz it wouldn't be very practical considering lots of LFE is in the 60hz range the sub wouldn't play them and the surrounds certainly wouldn't receive them, so now you have dropouts. In most systems you are best off setting all speakers to small anyway and running the receiver's x-over around 80hz.

very good point; above whatever the crossover is set at, the LFE channel is removed.
so, even though the LFE channel goes up to 120Hz if the crossover is set at 40Hz, 80Hz are more or less chucked out (not completely gone though because of the crossover slope).

 

[no. 5]

no. 5

But how many do you think would stick these in there home cinema.

well I would be ok with it.

 

[Seth=L]

well I would be ok with it.

Not good WAF, right.

 

[no. 5]

Not good WAF, right.

yeeeaaahh.

 

[Dolby CP-200]

very good point; above whatever the crossover is set at, the LFE channel is removed.
so, even though the LFE channel goes up to 120Hz if the crossover is set at 40Hz, 80Hz are more or less chucked out (not completely gone though because of the crossover slope).

no. 5

That’s why I run my LFE.1 completely separate from the sub bass extension where the cross over is set to a lower crossover point of 40Hz. I can get plenty out of the three-screen JBL control 5 where some parts of reproduction might be around 100Hz well I need to feel that coming from the centre channel in most common situations.

I would let the LFE.1 play from 20Hz to 120Hz you can never tell if some part of that track might go unheard, well you might be missing the strength of the signal that relates to the visual image on screen.

 

[no. 5]

no. 5

That’s why I run my LFE.1 completely separate from the sub bass extension where the cross over is set to a lower crossover point of 40Hz. I can get plenty out of the three-screen JBL control 5 where some parts of reproduction might be around 100Hz well I need to feel that coming from the centre channel in most common situations.

I would let the LFE.1 play from 20Hz to 120Hz you can never tell if some part of that track might go unheard, well you might be missing the strength of the signal that relates to the visual image on screen.

no sound left behind, eh?