Help! still having room issues

[djn]

Hi All, I moved to a new house and new listening room. The room is 15"x16" and is dedicated. Of course, the sub nodes where all over the room and with 4 subs scattered around the room it is flat where ever I sit....so no issues there.

Now, I have a room resonance at around 250hz that is very audible and is confirmed with a room calc. So, this is the first time I have had to deal with room issues and I've heard about bass traps but don't really know the best way to approach it. I'd like to make them myself so Annie can pick out the cloth (you know WAF).

behind my system I have a black wall that from the edge of the subs measures 12" and I have a 24" x 24" x 8' slot, between the book case and stair well wall, for the lack of a better word at the back of the room.

I am thinking of making panels for behind the system but don't know how they are made. And a 24" x 24" X 8' tall absorption box (don't know that that is what to call it) for the slot in back of the room.

Am I on the right track? Where can I find out the best way and materials for the panels and tall box??? I've googled it but there are so many sites out there I am not sure is some of it is snake oil or not. Thanks in advance for your help.

Here are pix of the room

[bjorno]

Originally Posted by djn

..Am I on the right track? Where can I find out the best way and materials for the panels and tall box??? I've googled it but there are so many sites out there I am not sure is some of it is snake oil or not. Thanks in advance for your help...

Hi,

Try these calculators:

mh-audio.nl - Acoustic

b


Example Picture added:

[djn]

Wow, thank you B. Here is something else I just thought of. If you look at the picture of the back of the room, you will see a set of louvered doors and those lead to an empty space that is 4' x 4' x 2'. Would filling that with polyfill and taking the doors off help?

[c2cthomas]

DIY Room Treatment Devices Article By Bob Jackson (aka Bob In St. Louis)
Feature Article
RealTraps - All About Diffusion

Lot's of stuff out there on the net. More than enough to get you wrapped around the axle for months to come............

[djn]

Thanks C. Good stuff there. Lots to think about.

[c2cthomas]

BTW - I agree that you are on the right path to audio bliss - the room treatment offers a lot to gain in terms of enjoyment. Of course for those that don't have that luxury (say someone living in a dorm or an apartment) then some good headphones are always worthy of consideration.

Having a good pair of headphones around can serve as a pretty good reference source as well.

Then there are people with hearing such as mine - in which case a couple of soup cans and some string are about as good as it gets....

[cyclecamper]

Re: your empty space

Yes, you could definitely make an effective trap of some kind in that space. But whether you leave the louvers on, open, closed, doors open, closed, or some other drilled door etc. will change completely the balance of what frequencies (and wavefront polarity) are absorbed.

Have you figured out whether this is a simple standing wave between floor and ceiling, or side walls, etc. or some more complicated circular reinforcement? And is your average decay time short or long? If the room is pretty hard it's easier to get into balance, but still too live. I'd start with LEDE principles, absorbers where a mirror would show an image of the speakers from the sweet seat, rear diffusers, heavy drapes instead of blinds on that window, then measure. If measuring is difficult, try the old hand-clap test and train your ear. The carpetted stairs can be a good thing. The foundation-wall 'step' in your walls is a good thing. You can also consider a high-waf bass trap by putting a solid or perforated back on the shelves, with a layer of absorbent ceilng tiles and absorbent foam (between the wall and the shelving uint) and tune it via the size of any perforations and how far you space it from the back wall. Most of all, remember that more narrow-band absorption of the higher frequencies without matching absorption of the lows will make balancing even more difficult. Bass absorbers in the corners can do wonders. But just a curtain on the window might actually make it worse, or can be wondeful if you add matching bass absorption. If you can step your ceiling, put on large crown mouldings, another area run on the floor, those can make a difference too. For every absorber panel I hang to catch a near-field reflection I also add twice the absorption to the back side of some cabinet or painting. If you resort to commercial foam products, you can greatly improve their bass absorption for your money by gluing them to double-thick pieces of acoustical ceiling tile and experiment with mounting them some distance from the nearest wall or ceiling surface. And of course, you can always buy sonotube concrete forms and stuff them more or less or trim their length to tune (and decide whether to treat their exterior or not...just having the rounded shape present is also good, and again be careful not to absorb more treble than bass which is an easy mistake). You can easily improve both your soundstage (by absorbing nearfield reflections) and your overall response if you're careful and balance your changes carefully. And whenever you mount somethign on the wall or ceiling, consider tunign its distance from the wall to optimize the bag for the buck.

I start by clapping my hands and listening carefully. 'cause I can't afford much else LOL. Then maybe a slow frequency sweep (it may take some time for resonances to build) and then maybe some pink noise then critical musical listening. Good luck. After that you probably need real measurement tools.

[cyclecamper]

Look up the math behind RPG diffusers if you have the time.

[djn]

Thanks Cycle. This is all fascinating. Both the Edgarhorns and Heils are know for great imaging, but in this room, the imaging is muddy. It is not an obvious problem that stands out like a sore thumb (like the mid bass issue) but I ran those from a couple years in my old room and they imaged like crazy.

I like the idea of putting 703 on the back of the book case. The would maintain a high WAF. She is very understanding and fully supports my hobby, but like the house to like like something other than a mixing room.

One of the links that C2C posted talked about just placing uncovered 703 around the room to see if it made a diff. and where the best placement was. I think I'll do that this weekend as well as stuff the empty space.

[FrankWW]

You say the room's OK, mostly, with the multiple subs but you have an annoying resonance about 250 Hz.

What's behind the door by the stairs? Is it a closet? What happens when door is opened? Is the 250 Hz still there? If it is a closet, is it empty or full? If you hang lots of heavy clothes* in there it will trap remarkable amounts of bass if the door is open, and you could get the same effect as open door with louvred door.

If it is a closet you might well give that a try before you spend money and energy on other things cuz it just might work!

* I mean lots. Heavy wool coats, things like that.

Imaging. For an experiment you might kill the reflections from the wall behind the speakers. Just hang something heavy and temporary behind the speakers. See what happens.