[doctorcilantro]

Hi all,

I'm settling into our new house and starting down the road of room correction with Audiolense and J. River 18. I think this room has potential, and I cam currently working on some more absorbers. The house is so live with all this tile and a VERY high stairwell in the next room. I actually plan to put absorbers way up on the ceiling in the stairwell to mitigate "family"  noise i.e. 3 & 6 year old. Damn it's live in here!

I'm planning to put some absorbers up in the rear wall up high, since I have a standard sliding glass door there. I'm thinking about (3) 4'x4' panels of rockwool that are 2" thick, 2" off the wall on a frame.

I'm also trying to possibly do the same amount on ceiling to finish off RFZ. I don't think it will be overkill since the house is tile and the room is kind of big, and currently quite live. Maybe I only need (2) of these larger 4'x4' squares up there.

Also planning on building a small mini super chunk. I'll take pics of that idea, and the room shortly.

The rockwool I am using is 70kg/m.

I have some tri-corner panels from Primacoustic that are going in ceiling corners, possibly with a little pink fluff behind them.

I think this room has good potential. Curious about the glass windows and sliding doors 7-8 feet behind my head BEHIND curtains; I wonder if there is a glass tinting-like material I could use to deaden the glass, or if the curtains will be enough. I'd rather not have to hang temp. panels up there if possible.

I'm using the MPR1 mic pre and calibrated mic kit. My subwoofer is broken and I have not yet done unique L/R sweeps. These speakers start to roll off at 80hz.

The speakers are 8ft apart and I have a chair I like to put in front of the velour covered couch at about 8ft.

• 

• 

And another waterfall with 1000ms:

• 
• 

And here is the .mdat file: https://docs.google.com/file/d/0B4DCwTNWPBykMHFyblBsTnZqRHM/edit

[bpape]

In my opinion, you're going way too far with thin absorption only and basically nothing at all in the bottom end.  The waterfalls you posted clearly show very long ringing  with the upper mids and highs already pretty much sufficiently damped.

I would look at some much thicker treatments in corners and potentially some things between the curtains and the windows to at least broaden out what that large area of absorption is already doing.

Bryan

[doctorcilantro]

I have more sweeps to run, and sum individual L/R, but the room is pretty live and none of those large absorbers are up nor are the tri-corners.

I could look into doubling up the panels on the backwall as I can't do any major bass trapping operation in here.

[doctorcilantro]

Here are some questions about getting some bass trapping with these 4' x 2' 70kg/m rockwool panels.

1. Should I double these up when making my panels and just make single 4' x 2' x 4" (2" off wall) so I can move these around and have more flexibility over the 4' x 4'?

2. Can I trap bass by doubling up the ceiling units that are there to mainly just cover first reflections?

I know corners or the best for bass trapping, but what do I achieve with 4" panels wherever I can hang them. Thick is always better correct?

3. What about on the back wall: placing some of the 4' x 2' x 4" straddling the horizontal ceiling/back wall interface. Then below those, place absorbers as planned.

[Alex Reynolds]

Here are some questions about getting some bass trapping with these 4' x 2' 70kg/m rockwool panels.

1. Should I double these up when making my panels and just make single 4' x 2' x 4" (2" off wall) so I can move these around and have more flexibility over the 4' x 4'?

2. Can I trap bass by doubling up the ceiling units that are there to mainly just cover first reflections?

I know corners or the best for bass trapping, but what do I achieve with 4" panels wherever I can hang them. Thick is always better correct?

3. What about on the back wall: placing some of the 4' x 2' x 4" straddling the horizontal ceiling/back wall interface. Then below those, place absorbers as planned.

1. Yes
2. Yes (also yes)
3. Yes
That would all work great but note that 4" absorbers with a 2" air gap will only absorb efficiently down to about 100 Hz and leaves the area under that untouched for the most part. 4" absorber straddling a corner should give good absorption down to about 80 Hz, but you'd want super chunks either in a triangular or square/soffit shape to get down to 50 Hz

[doctorcilantro]

Thanks Alex.

I'm focusing on the back wall absorbers right now and I need to make a design decision.

I built a simple frame and the 4x2 rockwool panel sits on top of the frame. The test unit's corners were rounded as expected but the the sides were quite "pillowy". Trying to make these a little more aesthetically pleasing as opposed to getting a padded room look.

So, I tried a new version which has left me with: panel cut to fit inside frame and a panel sitting atop the frame. Both panels wrapped together as one unit, after cutting first, with poly batting.

So right now when mounted the inner panel would be flush with wall.

My question:

1. Should I putting a plywood backing on these and call it day?

2. Add the same frame or some kind of simple mounting unit to get them 2" off the wall. No plywood.

I hope I explained it clearly, fainting of stomach bug and will draw a pic ASAP.

Thanks
Dr c.

[Alex Reynolds]

Hey Dr. C -
I responded to your post in the music player forum - sorry I didn't see your question here earlier.
I would look into doing a box frame - you can make the box 2" deeper than the actual insulation you use so that it provides a built in air gap. You'd need to secure the absorption in place with netting, fabric, or a piece of wood, or something else so that the insulation doesn't openly flop around inside the panel, but the built in air gap would be beneficial (and also would allow for easier mounting)

[doctorcilantro]

Alex, dumb question, when you say box frame, is the NO plywood backing? The back is open?

I started with a panel on a frame, but then I added a 2nd panel that sits inside the frame, thus flush against the wall.

I could add a full frame on the back, but would have to secure it with screws, OR I could just devise a way to sit the panel 2" off the wall.

I'm not sure my wife will approve (this is our living room) so I think I'm stuck FLUSH to the wall. The Acoustimac panels are sealed and I assume there is just fiberglass in there.

I'm curious if there is some acoustic benefit; why would they add materials and cost when they could leave the back open?

• 

[Alex Reynolds]

There is no acoustic benefit to closing off the back, it's more than likely for stability/sturdiness or perhaps for cost of materials, I don't know.
A 2" air gap will help but I'm not so sure if building an entire separate frame to house the air gap which would need to be screwed in would be worth it really. If it were all one frame then it wouldn't be as difficult.
All I meant was, just like your middle portion that has a frame with absorbent in it, doing that for the entire absorber would help prevent the pillowiness of the corners on the front portion of the trap.

[doctorcilantro]

There is no acoustic benefit to closing off the back, it's more than likely for stability/sturdiness or perhaps for cost of materials, I don't know.
A 2" air gap will help but I'm not so sure if building an entire separate frame to house the air gap which would need to be screwed in would be worth it really. If it were all one frame then it wouldn't be as difficult.
All I meant was, just like your middle portion that has a frame with absorbent in it, doing that for the entire absorber would help prevent the pillowiness of the corners on the front portion of the trap.

Many many thanks. I have finished my ceiling units as well, and I have one more stupid question in my bag of ignorance.

Can I gain the 2" off the wall benefit but just "boosting" the panels off the wall with a small 2" square block mounted in each corner.

My guess would be yes, since the benefit with this type of absorber would be enhanced by simply "getting it out into the room" more.

Correct?

cheers!

[doctorcilantro]

I'm

In my opinion, you're going way too far with thin absorption only and basically nothing at all in the bottom end.  The waterfalls you posted clearly show very long ringing  with the upper mids and highs already pretty much sufficiently damped.

I would look at some much thicker treatments in corners and potentially some things between the curtains and the windows to at least broaden out what that large area of absorption is already doing.

Bryan

If the 50hz is modal which calc. predicted and the measurements show, how can I mitigate this without major bass trapping? I'm stuck in the real world here sharing this spacing and there is effectively only one corner I could do a superchunk.

If I did mount (6) 4" 70kg/m absorbers on back wall, should I be cramming these into ceiling/wall interface to "distort" the room dimensions? Thus affect the mode? Or will this be but a drop in an ocean?

I have a small mini-chunk in the corner which I cut from 1 4' x 2' panel. It made ( triangles and they are stacked and wrapped in poly batting; I was hoping to then turn this into a Helmholtz for 50-55hz by sealing it etc. I might need to make it much bigger though...

Now I'm wondering if I should just diffuse the entire back (7ft above floor-12ft ceiling by 12' wide. Add a pair of 4 x 2 x 4" on each back side wall pushed into the back wall/side wall interface (about 7 feet up). Then add some 2 x 2  x 2" squares on the back ceiling above the wide diffusion panel. The diffusion would not be coming into the ISD at that distance and RealTrap and others demos on diffusion impressed me.

However, moving my 4" absorbers off the side walls I'm worried about losing some of their effectiveness, but then again absorbers would "surround" the diffusion zone.

Regarding null/peak for bass, I sit at about 8 feet from front wall which is at the 38% point mentioned by Ethan Whiner, and the back wall is then 13 feet behind.

Hopefully DRC can help reduce some of these peaks...

[doctorcilantro]

before and after, still some issues but much better!

[bpape]

Can you set the Z axis to 300ms and just zoom in on say 20-1kHz so we can get a better idea of what is going on.

The decay time looks very very short in the room with the treatment up.

[doctorcilantro]

Sure no problemo. In the meantime these are linked to larger versions.