View Full Version : JBL SDEC and multiple surrounds

02-04-2013, 12:29 AM
I am very interested in how JBL handles multiple side surrounds. I thought that adding the correct delay to the surrounds would be enough, but apparently, the signal should be "decorrelated". I saw this article: http://dafx04.na.infn.it/WebProc/Proc/P_280.pdf?utm_campaign=website&utm_source=sendgrid.com&utm_medium=email

Is this something JBL does? I am currently using a BSS London Soundweb for DSP and if the SDEC can do it, so can the BSS. I am just not sure how to approach this.

Anyone ever tried a setup with multiple surrounds or knows how JBL is doing it in the Synthesis setups?


02-06-2013, 04:59 AM
No one? :) Instead of talking about how JBL ARCOS does it, do anybody have input to how it should be done to avoid potential issues having multiple sides?

Titanium Dome
02-06-2013, 05:36 AM
I cannot help you. I have an extra pair of S4Ai surrounds that I did not install in my current room because it is too small. The calibrator said that if the room were longer it would be no problem to add the extra pair of sides, but since we didn't do it, I did not ask anymore about it.

02-07-2013, 01:04 AM
Okay, thanks for your input anyways. I've been talking to a pro-audio guy and the way they do it is, to add some white noise into the speakers (inaudible levels) which decorrelates the signals and thus eliminating the issues by having to sources generating the same signal. I will have to study some more of the logic-concepts in the BSS units as the white noise level should vary when the input signal varies. The idea makes sense to me, even though its a little weird sending noise into the signal on purpose :)

02-07-2013, 08:31 AM
you could put your amp stacks by your extra surround speakers and drive the fans from
an audio signal averaging circuit... :eek: (joking).

More seriously, I don't doubt that what your pro-audio guy is doing has some effect, but
I have a hard time believing that inaudible white noise is going to decorrelate anything.

Can I assume you are talking about multiple surrounds driven from a single channel
(e.g., you're using 11 speakers and N-subs for a 5.1 or 7.1 system)? and you have a large
enough listening space that you need more then 7 full range channels? (ignoring height or
extra front channels). Many surround channel speakers are designed to be somewhat diffuse
already or have suggested placement with is not direct, which provides some decorrelation
(passive forms of some elements described in the referenced paper).

Might it not make sense to just wait for N-channel A/V equipment to arrive where it
synthesizes N-channels discretely? (let the source device do any required decorrelation)
Seemed like Dolby and SRS both had systems on the horizon, awhile ago. (?)

Also... might run this by the AVSform guys... there's a lot of HT sound experience there.

(curious, and thinking out loud ... not a criticism)