AVS Forum banner
Status
Not open for further replies.
1 - 20 of 68 Posts

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #1 ·
The back wall of my room is actually the front foyer. To one side of the door wall is a coat closet protruding 40" by 29" into the rectangle of the room. The 40" side is the closet door. The 29" side is a blank wall.


What if I broke through the sheetrock on the blank wall and covered it with fabric? Wouldn't the closet full of coats act as a bass trap?


How to calculate the effect, and how to control it? Opening size?
 

·
Registered
Joined
·
7,656 Posts
It will help absorb sound of all frequencies depending on where in your room it is located. If it is not a sealed enclosure, you want it full of insulation.


If you could steal some space from the closet, you could maybe just take 8-10" of it and seal it off and make the face either slatted or perforated Helmholz design.


Again, without knowing where in the room it is and what your issues are specifically, it's impossible to say what it would do, how to calculate, etc. Got a dimensioned dwg? Got a frequency plot?
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #3 ·
Here's the floorplan of the room. It doesn't yet show most speakers, the closet (you can figure it out - it's the indent at lower left), and an adjacent small room that I think is affecting the room modes.


I'm also setting up to do a better characterization of the modes, but haven't gotten there yet. I think I have a peak at about 32 Hz.

 

floorplan.pdf 23.576171875k . file
 

Attachments

·
Registered
Joined
·
7,656 Posts
Where to start.....


What is in the long narrow space on the right? Is that like under stairs and used for storage?


Are the openings on the left closable doors or just doorways or windows or what?


I assume that the space at the bottom of the dwg with the 2 doors is the closet, right?
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #5 ·
Quote:
Originally posted by bpape
What is in the long narrow space on the right? Is that like under stairs and used for storage?
That's a stairs down, off a hall.

Quote:
Are the openings on the left closable doors or just doorways or windows or what?
Passageways. Not closeable, although there are light control curtains. The upper one is a large room, the lower the small room I was talking about.

Quote:
I assume that the space at the bottom of the dwg with the 2 doors is the closet, right?
No. The central door is the front door. The door on the left opens into the closet. (The other two walls aren't shown.).
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #6 ·
Quote:
you could maybe just take 8-10" of it and seal it off and make the face either slatted or perforated Helmholz design.
Reference, please?
 

·
Registered
Joined
·
7,656 Posts

·
Registered
Joined
·
5,002 Posts

·
Registered
Joined
·
7,656 Posts
Thanks Bob. I didn't remember if they had corrected that or not.


DMF,


Those designs both tend to be rather narrow in the frequencies they will deal with. Sometimes you need that, sometimes you don't. If you need something broader but still dealing with bass only, check out a panel or diaphragm absorber. There are dwgs and calcs on that site for those too.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #10 ·
Thanks. I'm setting up to do the FR measurements now.


One thing I've noticed is that the floor resonates like a mofo. I've ordered a decoupling platform, but I'll take the first set of measurements with strong coupling. The construction is parquet over subfloor (3/4" I think) over two 12' runs of floor joist. It's open below. I wonder if there's some way to dampen the floor itself. Barb suggested acoustic foam, but it seems to me that wouldn't have much effect on LF.


Good sites, btw! It will be interesting to do theoretical vs. actual and find something to blame for the difference. :p
 

·
Registered
Joined
·
7,656 Posts
Just remember that theory for room modes assumes perfectly rectangular spaces, perfectly sealed, and with perfectly rigid walls, floor, and ceiling.


That said, it can still get you in the ballpark.


Hate to tell you but the floor isn't going to stop resonating just because you isolate the sub physically. If the parquet isn't glued down, you might have bigger issues. Normally, you could damp the floor from below somewhat but in this case where the parquet is probably floating, it probably won't do as much good.


Acoustic foam won't do much. You need to damp the panel (subfloor), not the air space.


Also, if your whole floor is hardwood, you are probably going to want to consider either some serious rugs and/or some absorbtion on the ceiling.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #12 ·
The parquet is glued down like it was welded. Believe me! I've tried to get it up!


Area rugs already. Ceiling is likely to remain open.


We'll see what it looks like.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #14 ·
Got my first ETF5 LF response graphs. While I try to figure out how to show them here, let me note the one outstanding anomaly: a huge peak below 20 Hz. Huge as it +30 dB! No obvious harmonic.


I have the SPL meter on a camera tripod with rubber feet. Moved it off the wood floor onto carpet, with little effect on the peak.


What could I be looking at here, the floor? Something else?
 

·
Registered
Joined
·
7,656 Posts
!?!? +30db @

It doesn't look like any of the room dimensions are big enough to excite a mode this low. The only thing I can think of based on your comments is the andjoining room causing a huge mode and the floor not being very rigid. Still, that big a peak that low - I'll wait to see the plots.


Try moving the mic to the left a foot or two and rerun the bass response just for giggles.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #16 ·
Mike on camera stand near middle of room.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #17 ·
Mike laying on ottoman in front of listening position.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #18 ·
I am discovering some really annoying problems with ETF5. E.g. if I ever touch their mixer, I have to re-install the sound card before the line inputs ever unmute.


Is there a forum where this stuff is discussed, preferably with the participation of the vendor?


Edit: Figured out that particular problem. Their mixer mutes the (normally hidden) default mixer Input control, and the M-Audio mixer input controls aren't linked to it. Now I can re-enable the input and use the ETF5 mixer. Question still remains about a forum.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #19 ·
This is the mike still on the ottoman (trying to decouple from the floor). Using the LF sweep tone and the RS SPL calibration file.
 

·
Registered
Joined
·
7,822 Posts
Discussion Starter · #20 ·
Waterfall version of the previous.
 
1 - 20 of 68 Posts
Status
Not open for further replies.
Top