Axiom Home Page Forums General Discussion Home Theater Maybe I should start a v4.0 build thread somewhere

Have her kill Nick instead. That'll save all the rest of us, too.

But not till he posts the listening tests.

Crap. If I don't post listening test results,then I am in trouble for not folllowing through, and if I do, then I get killed...

Short version, I spent about 2 hours over the weekend listening to demo material from some of my many demo blu-rays. Keep in mind that I wasn't going for louder bass, but to try to get reduce peaks and nulls. I first started with the new sub against the middle of the back wall, but it was "trapped" by the riser and seats, so it really didn't do much in my room. I then put it into the 1/4 position as shown in the pictures. I adjusted the SVS to match, and then re-ran Audyssey. I reduced the toe-in of the M60s as well as they were too focused on the front two seats.

While I had things torn apart, and before I put the screen back for the Audyssey calibration, I found the crazy first reflection points.

So, back to the test results... I had dramatically reduced all of the nulls, and most of the peaks. I am very happy. It should get better with acoustical panels if I build them like I want... Maybe next month.

Oh wait. I will be killed by then.

It is something like 18 inches off of the ground. I put the screen size, distance of seats, ceiling height, riser height for the second row into a program and it make some recommended heights for how far off the ground the screen should be. We just tweaked it so that people in the front row are not in the way for anyone in the back row. As is, there is only about 5 inches from the top of the screen to the ceiling.

It actually works out really well. No sore necks, and it is very immersive.

A couple of boxes showed up today. It isn't reflected well in the picture, but these boxes were BIG.

The one on the left is six 2" sheets of 2'x4' OC703 rigid insulation. The one on the left is a single 4" sheet of 2'x4' OC703.

Need to build frames for them, and get some fabric to wrap them with. The plans are for four 2'x3' panels for each of the side walls (total of eight 2" thick panels) and one 4" thick 2'x4' panel on the back wall. Should really help improve the sound.

Can I make a suggestion? I would make 4 4" panels and treat the first and second reflection points. Then I would use the rest to make corner traps 1'x4' and straddle the corners up front.

When I was treating my room I went slow and found in my situation that first and second reflections were more than enough. Treating the rear wall sucked too much energy out of the music I was testing with and made everything sound flat.

You are finally doing it! You will be happy I am sure. Detail, focus and localization of sounds are the biggest improvements we have enjoyed. I'm excited for you.

I hear ya. I am lucky to get "approval" for the 2" panels. No way the wife would go for 4" on the side walls.

As for my front wall, I have already treated it, including the corners. I had to search through this thread, but I found a picture.



Here is the link to that part of this thread:

Treating the Front Wall

Also, looking at the 2" vs. the 4" for FRP (First Reflection Points for the others that aren't familiar with the term) knowing that the primary goal is the higher frequencies as a "must" and then the lower frequencies "if possible," you get the following performance as taken from Bob Gold's Absorption Coefficients
(for those that don't know, a score of "1.00" is considered total absorption at the frequency. Anything above a 1.00 is not important really, and things like 0.17 means 17% absorption)

OC703 2"
125Hz : 0.17
250Hz : 0.86
500Hz : 1.14
1000Hz: 1.07
2000Hz: 1.02
4000Hz: 0.98
NRC : 1.00

OC703 4"
125Hz : 0.84
250Hz : 1.24
500Hz : 1.24
1000Hz: 1.08
2000Hz: 1.00
4000Hz: 0.97
NRC : 1.15

So the 2" panel actually performs better at the higher frequencies technically, but in real world are pretty darn close. The 4" bumps up the 250Hz a little, and really ups the 125Hz, but again, those aren't "as critical" when having to make some level of compromise to appease the wife.

As for the room becoming too dead, that is a possibility if I put the 4" panel on the back wall, but I need a little bass absorption and I can't do rear bass traps since the rear corners contain my equipment rack in one corner and media storage on the other corner. I guess that is some level of diffusion, but not helping in the LFE area.

If things become too dead, I can always add craft paper to the face of some of the panels and reflect more high frequencies (decrease the numbers from 250Hz up to 4000Hz) and actually boost the 125Hz bass absorption. I've heard of people doing that first before covering with fabric and getting results similar to using OC703 FRK vs. the regular OC703 like I have.

No matter what I do, I am going to build my frames first and make the panels WITHOUT the fabric cover. I will hang them and see how they sound. Too dead, then I get the graft paper out. Get them the way that I want them and then cover them.

Now if my room was just another foot wider, then I would do just four 4" panels on the sides and *maybe* the one in the back still. But I am fighting what seems like a little "narrow" when walking between the seats and the walls already, plus with 2 rows of seats, the first reflection points were ridiculous.

Here are pieces of take that I used to mark them on just one wall. I marked the FRP for the front left, right, and center for most of the seats before I just stopped and decided to focus on some key seats only. More compromises...



And no, that panel on the floor is not an acoustical panel. It is an AT panel that goes below my screen. I needed to put it somewhere (along with the screen) while I was getting the FRPs. And no again, my family hated the "racing stripe" idea of one long panel from front to back that covers all of the FRPs (sort of like if that WAS an acoustical panel and I just put it on the wall).

Maybe for v5.0 of the theater.... LOL

OK. I haven't posted an update in a while. Things are progressing slowly. I had to send off for some more printed fabric samples. I am trying two different types of fabric and getting 8"x8" samples showing 16 different potential color matches for the artwork. They still having shipped those yet, so they will probably not get here until next week. I am out traveling to Los Angeles and Denver next week.

As you see above, my OC703 is here.

Well, here are some pictures of the frames I built.

I used 1"x4" material (actual dimensions are .75" x 3.5") for the side wall frames and then 1"x6" material (actual dimensions of .75" x 5.5") to make the rear frame. This leaves a 1.5" gap between the OC703 and the wall, which enhances its performance quite a bit actually for the lower frequencies.

Frame for 2" OC703:


Frame for 4" OC703:


I ended up building 7 frames total. Three for each wall that are about 24"x48"x3.5" which will have 2" thick OC703 material and then the rear one is 24"x48"x5.5" for the 4" thick OC703 material.


I built the frames, glued and nailed the corners, glued and nailed a center brace, and then added 90 degree corner brackets for good measure.

Stack of frames:


Then I beveled the front edge all the way around.

This is a side shot of one of the frames showing the bezel on the top:


After that I added some cheap muslin fabric to the back to help hold in any insulation fibers/particles from coming out the back and into the room. This stuff is pretty dense and rigid, but no need to not take some precautions. I got 10 yard of the stuff for $15 tax included at a local fabric store using a 50% off coupon. Yeah, I went to a fabric store.

Here is one of the panels with the muslin stapled in place. It isn't pretty, but it won't be seen:


That brought me up to tonight where I needed to put the OC703 in. I knew that building the frames using lumber that was in 4 foot and 8 foot lengths, cutting this and making a frame would make one of the dimensions a touch short for the OC703 (2' and 4' lengths were cut, but that would give either an interior frame size of 22.5" x 48" or 24" x 46.5". Going with the second option meant less waste and more OC703 in use, so I did that.

So tonight I grabbed the trusty electric "turkey carving knife" and cut off the end of each OC703 sheet to get it to fit inside the panel.

You can see the right side over-hanging the top:


Then trimmed and set into place:


Here are the scraps (I know that there isn't any point of reference for size besides the electric knife):



So I have a good jump on the art for the panels, but I want to get the colors right as they print on the specific fabric before I go any further, so that piece is on hold. Tomorrow night I hope to get the panels hung on the wall for now. They will be removable so that wrapping the art printed on fabric fronts won't be a problem.

PS. My next project is a media server and then HTPC. Parts are already in route for the media server with its 18TB of hard disk space. Fun stuff for another time. HTPC will be in a couple of months once I actually have media ripped on to the server.

I'm doing what I can with my own space, but I'll never come close to yours. Great stuff, Nick.

Aren't you worried about the frames giving you extra reflections? Sure you get one large surface of reflection absorption on the front, but you added four more surfaces to bounce stuff around!

Oh crap. I am so screwed.

Oh wait, I'll just cause those parts "diffusion." Yeah. That sounds good.