5.1 and acoustics (treatment)

hello all again ! i have a question for John and for those here who are obviously much more competent than me. I believe i see a contradiction between John's design and some of the informations you can get from the net. Speaking of acoustic treatment and 5.1 control rooms, the document 5.1Rec from R.A.P.E.W (Sticky here)states that you must provide as much diffusion as you can, John apparently introduces a lot of diffusion (in the mid-highs) with his famous slat resonators, but everywhere else i can read that diffusion will lead to bad translation of the mixes because the listening will lack of precision with 5 speakers creating adverse refractions. Even John Storyk wrote a paper stating that ITU recommendations for RT60 in 5.1 CRs should be lowered from 20 to 30% Who is right here ? Everybody or nobody ? I must admit that i feel slightly confused Philippe

RT60 and diffusion will only be significant if the CR is large enough to actually create true reverberation, and also allows the diffusion treatments to do their job and not impact the listening position with extraneous reflections. the specs and comments you've read are not necessarily at odds. in a small CR where you're only 6-7'/2-2.5m from the speakers, you're already going to be dealing with a lot of reflections all around unless you can absorb things enough so you can accurately tell where the sound is coming from, and on top of that, you don't want it too dead or the imaging won't be right either and the mix won't necessarily translate as well... setting up a 5.1 mix room requires a lot more "little" acoustic treatments to create the right balance between treating the problem frequencies of the room, cutting unwanted reflections, keeping enough life in the room to ensure your imaging is correct, and you don't have too much reverberation... you're not going to do that with "large strokes" of treatments but you can do it with smaller ones...

Who is right here ? Everybody or nobody ? I must admit that i feel slightly confused Philippe

fair enough Phillippe :) The people who wrote that article are highly regarded producer/engineers - NOT studio designers except George Massenburg who we all know is into diffusors hence his total diffusor control room. I'm going to stick my head out here and say that the majority of the contributors to that article therefore are mainly trend followers rather than acousticians - hence the current infatuation with diffusors is reflected in their analysis. For example they stipulate a 13' ceiling - why 13ft, why not 11' 6" or 15' - they give no explanation for that suggestion as they give no explanation for the diffusor comment. In fact the only real suggestion to come out of that whole article is that the rear speakers should be further back than the 110 degrees originally suggested. They don't even say how far back. As you can see from my remarks I'm not very impressed with the article. cheers john

John not talking about this article anymore what would be your recommendations about the the treatment of a 25ft long, 17,4 ft wide, almost 10 ft high 5.1 Control Room ? Philippe

John Sayers wrote:

In fact the only real suggestion to come out of that whole article is that the rear speakers should be further back than the 110 degrees originally suggested. They don't even say how far back. john

Actually they say :

"Conversely, many popular music mixes utilize an “in the band” perspective in which the listener appears to be part of the ensemble and featured performers are placed in the rear surround channels as well as the front channels. These kinds of mixes benefit from the improved rear phantom imaging achieved by placing the surround speakers further back behind the listener, angled in at 135° - 150°. In most cases, this will yield the most satisfying music listening experience while still providing home theater aficionados with an excellent cinematic experience.

And on page 20 :

the P&E Wing recommends surround placement between 110° and 150°, with the optimum range being 135° to 150°

On the drawings (page 18, page 20) the rear speakers are positioned at +-150° Using that positioning doesn't leave much space for a guest couch :( My .02 euros ;)