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flanking subs with small mains [message #75604] Fri, 22 February 2013 13:37 Go to next message
dheflin44 is currently offline  dheflin44
Messages: 47
Registered: November 2012
Location: Carrollton, TX
Baron
Hi Wayne,

My current mains are fairly small (usable output only down to 60 Hz), so I've been searching for a way to blend in flanking subs while using my AVR's bass management to limit the main's extension below 80Hz. Please let me know if you think the general idea below is worth pursuing.

Since the AVR can't output overlapping sub and main outputs when bass management is used, I'd like to generate the overlap by using the line-level inputs on the flanking sub's plate amp to sum the L/R pre-out with the sub pre-out. The built-in low-pass filter in the plate amp could then be used to roll off the flanking subs above 100Hz as prescribed. To get the relative gains correct, the level of the overlapping upper range between the mains and flanking subs would be adjusted manually using measurements. The lower range of the subs (could be flanking and distant subs together) could then be set using Audyssey.

Thanks,
Darrell
Re: flanking subs with small mains [message #75606 is a reply to message #75604] Fri, 22 February 2013 14:01 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18669
Registered: January 2001
Illuminati (33rd Degree)

Let me see if I understand you right. This is what I think you are saying:

1. When bass management is used, the sub output is low-passed and the mains are high-passed at the same frequency.
2. You are considering setting this frequency to 60Hz to 80Hz, but then the mains will be high-passed and the low-passed sub output has all channels summed.
3. You want to provide some sort of "Y" connection to provide both subwoofer and mains signal to each flanking sub, thereby providing both the channel-specific signal and the deep bass signal.

Have I interpreted this correctly?

If so, let me make an alternative suggestion. How about running helper woofers directly off the mains instead? Use a high-efficiency midwoofer in an appropriate cabinet connected directly to the main it is flanking through a 5mH to 10mH coil. You could even use a second woofer just like the one in the mains speaker. Something that has about the same sensitivity as the main speaker. This is a simple solution and will achieve the same result.
Run the LFE channel to a conventional subwoofer or to a few distributed subwoofers in a multisub arrangement:
Re: flanking subs with small mains [message #75607 is a reply to message #75606] Fri, 22 February 2013 15:04 Go to previous messageGo to next message
dheflin44 is currently offline  dheflin44
Messages: 47
Registered: November 2012
Location: Carrollton, TX
Baron
Yes, that's pretty much what I had in mind. I assume you're suggesting running the mains full-range with the helper subs. I was trying to avoid running the mains too low since both my mains and AVR amp are fairly small, and I'm worried about compromising system headroom. If at all possible, I'd prefer to move all of the low bass to only the flanking subs while still getting the mid-bass blending with the mains.

Thanks,
Darrell
Re: flanking subs with small mains [message #75609 is a reply to message #75607] Fri, 22 February 2013 15:25 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18669
Registered: January 2001
Illuminati (33rd Degree)

Keep in mind that the flanking sub / helper woofer approach does most of its thing between 80Hz and 200Hz. So if the mains can run to 80Hz, you can run helper woofers like I described and get as much benefit from them as flanking subs that are typically run deeper. Your sound processor can be configured to high-pass the mains (and the connected helper woofers) at 80Hz.

The only real distinction between what I would call flanking subs and helper woofers is low-frequency extension. Flanking subs are generally run as helper woofers but with deeper bass capability. They do the helper woofer part up high, mitigating the self-interference notches from nearest boundaries. Then down low they act as traditional subs, but of course only with whatever content is in the channel of the main speaker being flanked. This can assist the distributed subs in smoothing lower frequency room modes.

But in your case, I think you're saying you want to high-pass the mains around 80Hz. So I'd probably consider running helper woofers, and not expect deep bass from either the mains or the helper woofers. The helper woofers are still flanking the mains, smoothing the 80-200Hz range, but they're not subs. They're more like a 2.5-way speaker used from 80Hz up, where the second helper woofer is detached from the main cabinet, set a little bit beside, behind and below it.

Then run your LFE channel to a traditional subwoofer or an array of multisubs.

Re: flanking subs with small mains [message #75611 is a reply to message #75609] Fri, 22 February 2013 16:06 Go to previous messageGo to next message
dheflin44 is currently offline  dheflin44
Messages: 47
Registered: November 2012
Location: Carrollton, TX
Baron
Instead of adding an LFE-only sub + helper subs, I'd rather use the flanking subs to serve both the low bass and blended mid-bass. In zheka's second post in the "Flanking Subs vs Helper Woofers" thread, he commented that current HT processors don't provide a straight-forward way of steering the proper signals to the flanking subs while using bass management. I think the method I suggested in my original post may be a viable work-around for this. It requires no extra equipment other than an AVR with pre-outs and a typical plate amp for the flanking subs that has two summing line-level inputs followed by a variable low-pass filter.

Thanks
Darrell
Re: flanking subs with small mains [message #75617 is a reply to message #75611] Fri, 22 February 2013 20:46 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18669
Registered: January 2001
Illuminati (33rd Degree)

Certainly, it is an interesting proposition. My suggestion was simpler, but it doesn't take advantage of the possibility of using the helper woofers as low frequency nodes, i.e. flanking subs. Your idea of using a Y-splitter does provide that. So if you get it going, please report back. Might be pretty cool.

Re: flanking subs with small mains [message #75623 is a reply to message #75617] Sat, 23 February 2013 13:11 Go to previous messageGo to next message
dheflin44 is currently offline  dheflin44
Messages: 47
Registered: November 2012
Location: Carrollton, TX
Baron
I wasn't sure if the explanation I gave in the first post was clear, so here is a diagram.

http://i521.photobucket.com/albums/w337/darrellh_photos/flankingsubconnection_zps172e335d.jpg

Again what I'm attempting is to allow bass management to limit the low-bass extension of the mains while still being able to mix the low-bass and mid-bass frequencies to the flanking subs. The only other way I have found to blend flanking subs using a typical AVR is to use the 'Large' and 'LFE+Main' settings in the bass management setup which effectively bypasses bass management and low-bass will not be filtered from the mains.
Re: flanking subs with small mains [message #75626 is a reply to message #75623] Sat, 23 February 2013 16:10 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18669
Registered: January 2001
Illuminati (33rd Degree)

That's how I visualized it. Sounds like a good idea, in my opinion. Might work with a simple "Y" connection for the sub/main "mixers". Please keep us posted with your progress.

Re: flanking subs with small mains [message #75627 is a reply to message #75626] Sat, 23 February 2013 16:27 Go to previous messageGo to next message
dheflin44 is currently offline  dheflin44
Messages: 47
Registered: November 2012
Location: Carrollton, TX
Baron
I'm confused. The pre-outs are fairly low impedance. How do you mix them on a splitter?
Re: flanking subs with small mains [message #75628 is a reply to message #75627] Sat, 23 February 2013 17:03 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18669
Registered: January 2001
Illuminati (33rd Degree)

What I was saying is the preamp outputs might be connected using a "Y". Depends on the output impedance. Or you might use a series resistor to provide some isolation. Otherwise, you'll need a mixer.

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