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Re: 4PI Plans Request [message #91248 is a reply to message #91247]

Mon, 09 December 2019 16:45

Wayne Parham
Messages: 18726
Registered: January 2001

Illuminati (33rd Degree)

The flanking sub low-pass recommendation of 100Hz second-order is empirical, so you can consider it a starting point and not a hard-fixed number. However, I have found that the slope is always better being gradual than it is being sharper. Fourth-order slopes are too steep. I have also found that low-pass below 80Hz is too low for flanking subs. The range of 100Hz to 120Hz and sometimes as high as 150Hz seems to work best. Much higher than that and the subs become localizeable and draw attention to themselves.

The low-pass and amplitude of flanking subs is set by simultaneous optimization of three things:

1. Amplitude level-setting the subs to the mains, so we gain bass extension at the appropriate SPL. This usually amounts to about 10dB more gain on the subs, because they are usually about 10dB less efficient than the mains.

2. Low-pass that conjugates baffle-step. Cabinets the size of my three Pi and four Pi mains tend to have baffle step in the 100Hz to 200Hz region. Instead of employing compensation in the crossover, we use the flanking subs to provide additional SPL as BSC.

3. Low-pass that mitigates higher-frequency room modes and SBIR from nearest boundaries. The worst anomaly usually comes from the wall directly behind the speakers, but the nearest side wall is sometimes objectionable too, as can be floor bounce. The modal region extends above 100Hz, but distant multisubs cannot be run this high without being localizeable. And the boundary interference notch from the wall behind the speakers seems to almost always be between 80Hz and 120Hz, probably because proximity to the wall behind the speakers is most convenient and/or popular in this range of a few feet. So this makes it useful to have a truncated array in the 80Hz-120Hz region, to counter the interference notches there. The flanking sub and the midwoofer in the mains form a simple two-element array.

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[Message index]

		4PI Plans Request By: Ziggin on Sat, 23 May 2015 03:51
		Re: 4PI Plans Request By: Wayne Parham on Sat, 23 May 2015 06:56
		Re: 4PI Plans Request By: Ziggin on Sat, 23 May 2015 11:58
		Re: 4PI Plans Request By: Wayne Parham on Mon, 25 May 2015 09:15
		Re: 4PI Plans Request By: Rustydog on Wed, 15 November 2017 00:40
		Re: 4PI Plans Request By: Wayne Parham on Thu, 16 November 2017 08:32
		Re: 4PI Plans Request By: Chas1980 on Wed, 20 December 2017 16:08
		Re: 4PI Plans Request By: Wayne Parham on Thu, 21 December 2017 08:36
		Re: 4PI Plans Request By: acamilicko on Mon, 25 December 2017 11:00
		Re: 4PI Plans Request By: Wayne Parham on Mon, 25 December 2017 12:33
		Re: 4PI Plans Request By: booangler on Sat, 06 January 2018 12:11
		Re: 4PI Plans Request By: Wayne Parham on Sat, 06 January 2018 13:22
		Re: 4PI Plans Request By: Quaker on Sat, 28 April 2018 17:25
		Re: 4PI Plans Request By: Wayne Parham on Sun, 29 April 2018 09:24
		Re: 4PI Plans Request By: Casmick on Mon, 30 April 2018 08:42
		Re: 4PI Plans Request By: Wayne Parham on Mon, 30 April 2018 10:24
		Re: 4PI Plans Request By: MH Lumber on Tue, 08 May 2018 17:02
		Re: 4PI Plans Request By: Wayne Parham on Tue, 08 May 2018 17:36
		Re: 4PI Plans Request By: MH Lumber on Fri, 18 May 2018 09:27
		Re: 4PI Plans Request By: Wayne Parham on Fri, 18 May 2018 10:17
		Re: 4PI Plans Request By: jeffx on Sun, 01 July 2018 07:47
		Re: 4PI Plans Request By: Wayne Parham on Sun, 01 July 2018 11:21
		Re: 4PI Plans Request By: grimberg on Fri, 10 August 2018 16:35
		Re: 4PI Plans Request By: Wayne Parham on Sat, 11 August 2018 09:23
		Re: 4PI Plans Request By: mikeincalgary on Wed, 19 September 2018 18:05
		Re: 4PI Plans Request By: Wayne Parham on Thu, 20 September 2018 09:13
		Re: 4PI Plans Request By: DavidM on Sat, 17 November 2018 07:35
		Re: 4PI Plans Request By: Wayne Parham on Sat, 17 November 2018 09:09
		Re: 4PI Plans Request By: kdlsrinu on Fri, 21 December 2018 22:34
		Re: 4PI Plans Request By: Wayne Parham on Sat, 22 December 2018 10:16
		Re: 4PI Plans Request By: tomkristian on Thu, 17 January 2019 14:44
		Re: 4PI Plans Request By: Wayne Parham on Thu, 17 January 2019 15:22
		Re: 4PI Plans Request By: Damkel on Tue, 19 February 2019 13:32
		Re: 4PI Plans Request By: Wayne Parham on Tue, 19 February 2019 16:00
		Re: 4PI Plans Request By: jheredia on Sat, 30 March 2019 20:53
		Re: 4PI Plans Request By: Wayne Parham on Sun, 31 March 2019 10:59
		Re: 4PI Plans Request By: Luithien1 on Sat, 06 April 2019 17:28
		Re: 4PI Plans Request By: Wayne Parham on Sat, 06 April 2019 19:09
		Re: 4PI Plans Request By: Luithien1 on Sun, 07 April 2019 09:09
		Re: 4PI Plans Request By: Wayne Parham on Sun, 07 April 2019 10:36
		Re: 4PI Plans Request By: jtwrace on Tue, 16 April 2019 08:44
		Re: 4PI Plans Request By: Wayne Parham on Tue, 16 April 2019 09:58
		Re: 4PI Plans Request By: Chris8h on Sun, 02 June 2019 15:01
		Re: 4PI Plans Request By: Wayne Parham on Mon, 03 June 2019 09:41
		Re: 4PI Plans Request By: daemonix on Tue, 11 June 2019 12:24
		Re: 4PI Plans Request By: Wayne Parham on Tue, 11 June 2019 14:31
		Re: 4PI Plans Request By: dkalsi on Mon, 01 July 2019 09:12
		Re: 4PI Plans Request By: Wayne Parham on Mon, 01 July 2019 10:40
		Re: 4PI Plans Request By: bigyank on Mon, 01 July 2019 14:26
		Re: 4PI Plans Request By: Wayne Parham on Mon, 01 July 2019 19:53
		Re: 4PI Plans Request By: malyh on Wed, 25 September 2019 04:38
		Re: 4PI Plans Request By: Wayne Parham on Wed, 25 September 2019 08:38
		Re: 4PI Plans Request By: malyh on Thu, 26 September 2019 02:30
		Re: 4PI Plans Request By: Wayne Parham on Thu, 26 September 2019 10:18
		Re: 4PI Plans Request By: bigyank on Thu, 26 September 2019 10:37
		Re: 4PI Plans Request By: Wayne Parham on Thu, 26 September 2019 11:10
		Re: 4PI Plans Request By: Esj on Sun, 01 December 2019 12:20
		Re: 4PI Plans Request By: Wayne Parham on Sun, 01 December 2019 12:50
		Re: 4PI Plans Request By: mathiasb on Mon, 09 December 2019 08:34
		Re: 4PI Plans Request By: Barryso on Mon, 09 December 2019 09:13
		Re: 4PI Plans Request By: mathiasb on Mon, 09 December 2019 09:42
		Re: 4PI Plans Request By: Wayne Parham on Mon, 09 December 2019 10:47
		Re: 4PI Plans Request By: mathiasb on Mon, 09 December 2019 11:40
		Re: 4PI Plans Request By: Wayne Parham on Mon, 09 December 2019 12:25
		Re: 4PI Plans Request By: mathiasb on Mon, 09 December 2019 14:59
		Re: 4PI Plans Request By: Wayne Parham on Mon, 09 December 2019 16:45
		Re: 4PI Plans Request By: mathiasb on Sun, 15 December 2019 22:12
		Re: 4PI Plans Request By: Wayne Parham on Mon, 16 December 2019 09:48
		Re: 4PI Plans Request By: mathiasb on Mon, 16 December 2019 10:07
		Re: 4PI Plans Request By: Sion on Fri, 13 December 2019 20:37
		Re: 4PI Plans Request By: Wayne Parham on Sat, 14 December 2019 09:53
		Re: 4PI Plans Request By: Valentino Beach on Sun, 15 December 2019 21:12
		Re: 4PI Plans Request By: Wayne Parham on Mon, 16 December 2019 09:51
		Re: 4PI Plans Request By: Damkel on Fri, 27 December 2019 13:47
		Re: 4PI Plans Request By: Wayne Parham on Fri, 27 December 2019 17:32
		Re: 4PI Plans Request By: Birdman on Sun, 29 December 2019 22:43
		Re: 4PI Plans Request By: Wayne Parham on Mon, 30 December 2019 11:11
		Re: 4PI Plans Request By: brad n on Thu, 16 January 2020 19:49
		Re: 4PI Plans Request By: Wayne Parham on Fri, 17 January 2020 10:24

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