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Re: Mono "flanking sub" [message #83020 is a reply to message #81624]

Fri, 15 July 2016 08:49

jonone
Messages: 67
Registered: October 2015

Viscount

Ok makes sense, so I take it you can work out the wall reflection notch by way of measurement to seating position?

More importantly how do you set the volume on your flanking subs to match your mains?

Really appreciate all the detailed answers your giving me, it's really kind! Cool

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Re: Mono "flanking sub" [message #83022 is a reply to message #83020]

Fri, 15 July 2016 10:25

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

Self-interference notches are very apparent in measurements. And they line up exactly as you would expect: At the frequency where path length distance causes a 180° shift, you'll see a 10dB to 20dB notch.

As for subwoofer volume, setting is pretty easy: Just match the subs to the mains. If you have measurement gear, you can set it for overall smooth response. Or you can dial it by ear pretty easily.

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Re: Mono "flanking sub" [message #83023 is a reply to message #81624]

Fri, 15 July 2016 11:09

jonone
Messages: 67
Registered: October 2015

Viscount

So say you play 75db pink noise through just your mains, do you then play the subs on there own and increase them until 75db? Or do you sweep them playing together until the midbass is smooth?

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Re: Mono "flanking sub" [message #83024 is a reply to message #83023]

Fri, 15 July 2016 13:41

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

Sweep them playing together and adjust volume until the amplitude response is smooth. Neither sub bass nor mains should be louder than the other. And yes, the midbass is where you should see this best, because that's where both mains and subs overlap. Both should be equally loud. But the goal isn't really to set them independently to match SPL; The goal is for the system to generate flat amplitude response.

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Re: Mono "flanking sub" [message #83025 is a reply to message #81624]

Fri, 15 July 2016 13:53

jonone
Messages: 67
Registered: October 2015

Viscount

Ok great that is pretty much what I did for my single!

I have tried to look and I'm sure I've asked you before but couldn't find the answer, do you add any delay to the mains or flanking subs to smooth the response?
I imagine because in your method the subs are behind the mains you could delay the mains slightly, does this help to reduce the notch's?

Can you please explain why you do or don't use delay.

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Re: Mono "flanking sub" [message #83028 is a reply to message #83025]

Fri, 15 July 2016 17:16

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

Delay is set by position. That's the point of having the subs behind, beside and below the mains. It creates delay in three dimensions, which no electrical method can do. Having the subs behind the mains delays the direct sound and it makes the reflection from the wall behind the speakers come sooner than the reflection from the mains. This also happens with respect to reflections from other boundaries, in all directions.

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Re: Mono "flanking sub" [message #83029 is a reply to message #81624]

Sat, 16 July 2016 01:37

jonone
Messages: 67
Registered: October 2015

Viscount

That explains it perfectly Wayne!
Do you think delay may still help my setup because mine won't be in totally diffrent 3d space, only except below the mains?

Do you apply delay to you distributed subs? I remember reading geddess recommends an adjustable "phase" dial on subs?

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Re: Mono "flanking sub" [message #83031 is a reply to message #83029]

Sat, 16 July 2016 09:06

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

I use positioning as the sole cure and do not apply any electrical delay. As I said above, electrical delay is a one-dimensional parameter and as such, it cannot correct a three dimensional problem.

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Re: Mono "flanking sub" [message #83032 is a reply to message #81624]

Sat, 16 July 2016 09:25

jonone
Messages: 67
Registered: October 2015

Viscount

It's Interesting that I found adding no delay to my two subs gave the flattest response, this was after hours of trying endless possibilities of delay between the two.

Thanks again for being so helpful! Razz

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Re: Mono "flanking sub" [message #83033 is a reply to message #81624]

Sat, 16 July 2016 11:48

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

Wow.......
page 7 of this thread is a great bit of info.

Ive been wondering about "delay" for the flanking subs as well, but Wayne confirmed my thoughts, with using "positioning".

I see a ton of home theater guys (example AVS forums) use electronic delay as if there is no question about it.

Why would anyone use electronic delay, especially when it only corrects in one plane (depth)?
Perhaps if you cannot adjust your mains from your subs in depth (all the same distance from the front wall), but can have the subs positioned next to (left or right) and lower than the mains, it can be of use?

Ive always felt that electronic delay, used incorrectly, might be as bad as room eq.
We all know what room correction eq does Shocked

Ive seen some stereo mains (typical tower speaker) designed in such a way that the bottom of the front baffle is out in the room more than the top (in other words, a tapered cabinet that is deeper in depth at the bottom than the top).

I understand this is to place the woofer/woofers out closer to the listeners, as to correct for the slight delay in timing/phase between the bottom woofers, mid range, and top tweeters.

If this line of thinking has merit, wouldn't this lead us to believe that placing the flanking subs out in front of the mains, closer to the listeners, with the mains being backed up against the walls might be another way of positioning?

The only thing I can think of is, the mains should be toed in, therefore generally positioning the mains out in the room more than normal, suggesting you put the subs against the front wall.

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