Acoustical Treatments Master Thread - Page 298

If they are going in the early reflection points then they need to go on the wall to cover the area between where you sit and the speaker. You can use a mirror to figure out where that spot is.
http://www.gikacoustics.com/news_020209.html

If bass traps for corners then it really does not matter. The corner picks up bass through out it.

Thanks for all the help.

Seems like I still have a long way to go with regards to improving my room acoustic. But I'm not going to give up.

My problem right now is the reflection to the ceiling... and how much it will affect my overall acoustic. I may have a problem with DAF (Dad Approval Factor) if I put more panels on the ceiling.

The rug's definitely going to be there to avoid the floor reflection.

Plus drapes over the windows. (Black out curtains)

Then at the moment two panels on the right and two panels on the left.

At least I know that what I'll do will have a MAJOR effect acoustically.

You can only do what you can do, which is better then nothing.

got it up.

(more pics of it in my sig)

How does it sound?

havent had a chance to listen yet.

Hello all,

I've got a question regarding floor treatment on a basement slab.

I haven't read all 9,000 posts in this thread, but I feel like I've read the ones that matter. I have a pretty good handle on basic acoustic principles and sound proofing versus treatment. I haven't begun construction of my home theater yet - I just have all the hardware in place right now. My basement is set up in thirds - typical 50s-era rambler. Laundry/bathroom on one side, furnace/utility on the other, "finished" room in the center (~13x26x8). It's certainly not finished to our liking, so we'll be starting over from scratch at a future date once we finish some other projects.

My question revolves around how to treat the floor. I don't have the luxury of a 9-10' ceiling, so the treatment needs to be thin enough to not adversely affect the seating riser and mounted projector (I will probably end up making some concessions in that regard). I don't want it to feel claustrophobic, but short of buying a new house I'm not sure I can avoid it...

What's the best way to deal with the reflective nature of the slab? 2x4 framed subfloor filled with insulation with pad/carpet over? Just a pad/carpet over the slab itself? What about the corners (floor/wall edges)?

Thanks.

Check my build thread post #25 shows my floor treatment.

http://www.avsforum.com/avs-vb/showt...2#post15187322

Here is a question regarding peaks and nulls caused by LFE waves smashing together (forgive me, I forgot the technical term for this)... Is the rear wall usually the biggest suspect to this problem? I know that bass is mostly omni-directional but I feel that the rear wall would be the highest priority to treat for bass, other than the corners.

I'm considering making a false wall roughly 2' from the back of the theater and filling that new cavity (complete width and height of the rear wall) with fluffy insulation to help with a 30hz peak at my rear seats (and possibly other smaller peaks and dips throughout the seating area). If I do this, the front of the false wall will certainly contain material for mid/high frequency reflection, 1/8" plywood of similar I take it, or just 6 mil plastic maybe? Possibly vertical strips of the mentioned material?

Or, should I skip all of that and build a couple of tuned helmholtz resonators? Maybe some mambrane panel absorbers on the back wall? Hmm..

Also, can a room be "too small" for tuned absorbers to work properly (helmholtz or membrane)? I think I saw Ethan mention that for smaller rooms, other options are recommended. Speaking of Helpmoltz resonators, does it matter where in the room they are placed?

What are your thoughts on those ideas?

Question guys...

My corners have all obstructions if I plan to put a floor to ceiling bass trap. Hard situation, I know!

The corners on the front, after advancing .200m due to the projector cove, will either hit the window or will interfere with the Blu Ray/PS3 Storage that is within the cove.

Are there other options aside from putting it on the corners floor to ceiling?

Chris

Generally, it is the first three, or four, axial room modes which are most troublesome. Axial modes are length, width and height. If you treat only the back wall, you can only affect length modes. You cannot address a width mode with treatments on a back or front wall regardless of the type of treatment used (resonators or otherwise).

From a practical perspective, resolving modal response issues in small rooms requires multiple methods and techniques ... not just some form of absorption ... to address.

I would say that your thread gave me more ideas than just floor treatment! Very nice work. Can I copy some of that?

I doubled up on the curtains behind the couch after reading here that they need to be thick. They are in front of a set of French doors. Will these be effective at diffusion and reflection?

I left the thin ones on top ( to be pretty )and there are blackouts underneath.

Denis gave you the right answer but just to add, generally speaking the back wall is your next place to solve low end problems. Some of it is SBIR (some call this LBIR) and so on. Keep in mind though that modes are not just length though.
As far as what kind of treatment, tuned trapping is GREAT and we install it into a lot of rooms, but if it is not built correct then you may end up wasting a lot of time and money. Basically unless you feel 100% confident in the design (and your skills/understanding) then I would just stick with broad band. FYI it takes a lot of tuned traps on the wall also, so don't think you can build a 2x2 unit and think all the problems are solved. Plan on 15 to 25% of the wall covered.

Sure

It is a Dennis Erskine designed theater and I love it.

Have him design one for you.

What types of treatment do you recommend for low end absorption since I don't have mega room to work with? Also, I figured the back wall was the contributor to the big peak at 33hz, the bob golds calculator shows this... 31.4 hz 35'12", 17'12", 8'12" (1,0,0 Axial). It looks like a length problem to me with my room being 18' long? How would I treat the width and height modes for bass?
I know modes are not only length, but I'm not sure how to treat for width and height modes, I don't know if their even a problem in my room

Hey guys! It's me again with additional queries.

The room has come a looong way... I've long resigned the fact that rockwool in between gypsum board will not help my room acoustics at all and has now shelled almost $700 for acoustic treatments.

If any of you remember my floor plan... you will be familiar with my case. But anyway here's what I did:

Two panels on each side (24x48x4 Rockwool inside)
One panel (24x48x4 Rockwool angled on top of the projector screen side)
Four bass traps (24x43x4 Rockwool) on all corners (4) angled 45 degrees to cover the corners.
Four wood diffusers on the ceiling.

I also will definitely buy a "hairy" carpet since I have engineered wood.

And again, all windows and sliding doors will have drapes over them. (Blackout Curtains)

Question: Since I haven't fired up the equipment yet... the room is on its finishing stage... Did I do great on improving the room acoustics? What else do I need to do?

Maybe next week (a BIG MAYBE) I'll be able to start setting up the equipment already. For now though, all I can do is wait and prepare the room for it.

Well the way to find out is to test the room.
http://www.gikacoustics.com/video_rew_room_eq_wizard_tutorial.html

Thanks Glenn, I should have been more specific. I have measured the room quite a bit but since there are so many room modes (length, width and height), by looking at my graphs, I'm not sure what ones are being problematic. Let me post a few plots later and see what you think

Here are a few graphs for you to take a gander at...

This is my front center seat overlayed with my rear center seat. Blue is rear row...



Rear seat waterfall...



Front seat waterfall..



What areas do you think might be room mode related?

60hz, 80+hz, 110+hz.
What are your room dimensions?
Do you see these peaks if you put the microphone in 4 other places? (sound only matters where the ears are, but questions are answered all over the room, such as within a few inches of a tri-corner)
Can you move your speakers so they don't excite these?

If he has a huge dip at 110+ on the first chart, why does the waterfall show such high DB ?
Grap shows lower than 45db and waterfall shows 75-80 db

Room dimensions are 18 x 10.5 x 7

Speakers are mounted into the wall, they cannot be moved.

Look a little closer at the graphs, the peak in the waterfall is about 125-130hz, the dip is right before that around 110hz. It's a little deceiving while reading the waterfall as the ringing drops of at an "angle" compared to the actual dips/peaks.

Ok upon closer look you are correct, but even then its still a few off but I wont quibble :-).

I've seen your posts on other board as well..remind me again 2 subs? or 1?

I'm trying to follow as much here as I shall be doing the same soon- measuring and treating what I can.

60hz, is near a potential front back axial.
80hz, is near a potential up down axial.
107hz is near a potential left right axial.
125 hz is near a potential front back axial.

I'm wondering if RPG {Modex Corner, Modex Edge, Modex Module}x{63hz, 80hz, 100hz, 125hz} might be useful.
Or some much cheaper superchunks along all bi-corners (four wall-wall bi-corners, and four wall-ceiling bi-corners).

If you do the superchunks, experiment first. Lean 4" of unfinished 703 against the floor-walls, and against the wall-walls, and measure and listen to see what happens.

I've already done superchunks almost floor to ceiling in the rear two corners, a little help with the ringing I think but nothing significant, no room response change anyway.

Those might help a little bit with the 60hz and 125hz, but probably nothing on the 80hz and 107hz. What happens if you take them out?

EDIT: Yea, it looks like that's what they did. A 60hz dip smoothed out a bit, and a 125hz peak dropped down a bit, and no change at 80/107hz.
http://www.avsforum.com/t/1401657/first-run-with-rew-advice-and-tips-please#post_21900503
Edited by BasementBob - 6/8/12 at 8:54pm

You could try adding an active device; these have been well reviewed:

http://www.spatialcomputer.com/page9/page10/page10.html

Any additional information/links wrt well reviewed? I like to read it.

There was a similar such product/approach back in the 80's. I thought Nelson Pass may have been involved, but I'm not sure. It consisted of a tall cylindrical tube product, with transducers top and bottom, placed logically at pressure zones in the room,....floor and ceiling. With two of these in the rear two corners of a room, I recall the reviewer raving about the subsequent acoustic results, and added bass detail and delineation. With a mic, amplification, and an attempt to null the the energy build-up it was well received wrt pro reviewers, but commercially, not so much IIRC.