How to identify ALL reflection points easily?

[manishk13]

Hi

I am on the verge of ordering some Anutone wall and ceiling absoprption tiles, backed by synth (equivalent of glass wool). I have adopted the formula of ALTERNATING every 4 feet between Anutone boards (for absoprtion) AND ply (for reflection do that not all sound gets absorbed). Both will run till 7 feet high. Have discussed this with Santosh and Shubhash .

However, opening the floor open for more suggestions. Is the alternating strategy between absorption and reflection ok ? Room is 20 feet long and 16 feet wide. The alternating strategy is being adopted on the side walls as well as the back of the seating position. It will be ALL anutone behind the screen

Is it possible to nail down reflection points exactly rather than blindly alternate between absorption and reflection ? Of coURSE i HAVE DONE THE MIRROR Test and found the first reflection point at 5 feet from the tower speakers.

Also is it ok to treat to 7 feet high instead of only 4 feet from floor ? I just want to be safe

Thanks
Manish

 

[cmsajith]

I am confused about your plan for alternate anutone boards and ply. In another mail also you mentioned the same, but since you had mentioned about Santhosh's setup, i had assumed it as anutone boards at the bottom portion for about 4ft height and the upper portion with ply upto 7ft. Am i correct?

But, if your plan is to put alternate anutone boards and ply upto 7ft ht (vertically), i would not recommend that. There will be 4 set of first reflection points on the side walls (2 set on each) for a stereo setup and a 2 more sets for the center channel. Also there will be another similar set of first reflection points on the ceiling and the floor. You should absorb all the first reflection points. You are not going to loose the liveliness by absorbing them (you will get the liveliness as you are treating only the bottom portion of the room and a small portion of the ceiling), instead it will give you the wide soundstage and prevents the high and mid freq colouration. Also, based on the speaker position, there will not be any first reflection points at 7ft ht. For the front and back walls you should treat wall to wall (Front wall : mid-high freq absorption, Back wall : a mix of mid-high-low as it is near the listener.) For liveliness, you can try diffusers at the backside of the side walls after the first reflection points. Since the listening position is far, you can try diffusers for the second reflection points. But putting diffusers for the 1st reflection points can create undesired results if it is not done properly.

Is you ceiling comes at 7ft? I believe there are two lofts at the side walls and from one of your posts it seems that you are worried about the stability of the wall on removing the loft. If that is the case, i would say remove the loft as it has nothing to do with the stability of the wall as it will be on an RCC lintel, moreover the wall is holding the loft and handling the weight of the loft, unless it is a pillar construction. So if possible, remove it.

If you are planning to keep it as it is, dont close it and create a box structure as it will resonate. Instead consider it as a false ceiling and use it to highlight your upper ceiling (black coloured) by indirect lighting and direct light downwards as wall washers. Make another false ceiling at the ceiling ht with the acoustic treatments. You can try star lighting or some designs on the top ceiling.

In this case you have to use more bass traps, esp tri-corner traps. You have to consider the corners\sides of the loft as the ceiling corners\sides itself and put bass traps below and upper portion of the loft along with the ceiling bass traps. For isolation, you have to treat the upper wall of the loft using ply with glass wool,same as the wall below the loft.

Note : Manish, please dont start new threads as it creates confusion and people will not be ready to check your other threads to find some related info (i had to search to find your issue with the loft) and can result in asking / writing the same info. Better you merge all discussions to a single thread so that it will be useful for others also in future.

 

[Electrify]

Hi Manish,
Your room ratio is quiet okayAssuming you have a ceiling of 8.5 ft and you set the speaker atleast 1.2 meter in front of the rear wall and .8 m from the side wall with a toe in angle of 25 degrees towards the listener at 4.5 meters from the front wall the firs reflection point one the sidewall is 2.2 meters from the front wall. I would think about using absorption panel for the entire front and up to 3m on the side wall. and behind the listener about 1.5 on both sides from the center of the room should be done with acoustic panels which is 1 inch thick 50 mm distance to wall behind. For the other areas you can use ply or ply and acoustic combo. In general to handle different frequencies you could vary the distance between the wall and each of the panel. Also angle the panels towards the listener so that the panels on either side of the sidewall is not parallel to each other.
One thing, the reflection pattern is dependent on the radiating pattern of the driver, I have assumed a generic and not specific for your speakers. Neverthless, it should provide a good idea. Hope this helps

Regards
Shankar