Acoustic Advice Needed for My Unfinished Basement Home Theater

Greetings. I have acoustic problems in my basement home theater, and I am hoping I can get some advice on how to best correct given an extremely limited budget.

I have cobbled together the components of my home theater over a number of years, and several years ago we were fortunate enough to purchase a house with a basement that I could use a portion of to be a dedicated home theater. My basement is unfinished, with poured concrete walls and open joists and ductwork in the ceiling. Someday I want to finish at least this portion of the basement, but there is no budget to do that for at least a few years. I did build a partition that I filled with Roxul to minimize the sound from the furnace and hot water tank when I am watching a movie, and it does the job I built it for. Most of the furnace and hot water tank sounds that still come through is via the cold air return duct that has its opening on the HT side of the partition.

Equipment:
Denon AVR-1913
Front L/R – Genesis I’s (from Genesis Physics Corp)
Center – PSB 200c
Surround L/R – PSB Alpha Mini’s
Surround Back L/R – PSB Alpha Mini’s
Subwoofer – Yamaha YST-SW100 (there is no LFE input, so the sound is obtained by routing the L/R mains through it; I believe this limits some of the AVR crossover functions I have available)

This is my first post, so I am hoping I will be able to upload some pictures to help visualize my situation.


As you may have already identified by looking at the pictures/diagrams, there definitely are some acoustic issues. I have problems hearing dialogue and to temporarily compensate, I’ve bumped up the level on the center channel. I also find I need to have the level on the receiver set far louder than I would like. (Don’t get me wrong, at the higher volume it sounds good with no noticeable distortion that I detect, but I would like to be able to hear clearly at lower volume levels.) I have slightly angled the center up toward where the audience head would be, but am thinking I should build a better stand with some scrap 2x4’s that will raise the height of the center to just under the screen, as well as angle it more accurately toward the heads.

My budget is currently pretty tight, so I don’t have the funds to bring in a pro to analyze and recommend. I’ve been trying to search the various forums and articles, and have found a lot of useful information, but have not had the time to review in the depth required to truly understand.

I have 9 pieces of leftover 15.25” Roxul that I’m intending to build some acoustic panels with, and enough 1x3 to make 4 panels. I know they won’t be the 2x4 panels that seem to be most prevalent, but from the posts and articles I have found/read, I thought they would still be beneficial.

1) Am I correct in thinking I would benefit from using this 15.25” Roxul, or should I hold off until I can purchase and build panels with 24” Roxul or OX-703?
2) If I should use what I have, would I be better off with 2 panels of 1 piece/ea (3” thick) and 2 panels of 2 piece/ea (6” thick), or 4 panels of 2 piece/ea (6” thick)?
3) Where should I position? I’ve read about finding the first reflection point using a mirror parallel to the walls.
4) What would the next incremental improvements I should work toward implementing, prior to being able to being able to finish with drywall/drop ceiling, as funding permits? e.g. Build more acoustic panels and put “x”? Build bass traps to put in the ceiling “corners”? Put Roxul in “strategic” ceiling joist cavities, perhaps held in place by some muslin? Etc.

Thanks everyone in advance for taking the time to read my post and offering your advice.

Dave
Edited by ohiodaveht - 2/14/13 at 8:31pm

Thanks for your feedback, Mr. Tim. It sounds like I should try to make as many 1 layer Roxul panels as I can with the Roxul I have, and place them at the reflection points on walls and ceilings, and corners, instead of doubling up on the Roxul in some of them. Correct?

Anything else you would suggest before I someday finish the space?

Thanks again for taking time to advise me.

Dave

Thanks!

Thanks for confirmation on my opinion regarding the center channel. With the 4:3 format of the screen, I can't raise it as high as it likely needs to go without putting on top of the screen, and I'm not ready to try that yet. We'll see whether this weekend I can sneak in cutting some 2x4's and assemble a better stand than I have now. I'll let everyone know how it goes once I'm done.

I meant to upload a different picture than one of them twice, which more clearly showed that the front of the room has a "bump out" to the left of the stairwell that is about 44" deeper than the rest of the room. (It is on my other computer, which is why I still haven't done it.) That "bump out" is where the equipment is to the left of the projector, the door to enter the space, and the front of the stairwell that I put a door in so I could use as storage. Since I had to drywall the interior, I went ahead and stuffed Roxul in as much of the joist cavities that I could reach. The exterior of the stairwell enclosure was already built, but the builder never put in a door because he didn't want the added cost of finishing the interior.

Anyway, I was wondering how this shape affects the acoustics? At the moment I'm assuming I need to sit in the money seat, and adjacent seats, and do the mirror test on that wall as well as the right wall to see where the first reflection points are on each.

I found some videos showing how to make panels where the 1x3's form a "back" frame where spray adhesive and the cloth holds the Roxul in place. I think that will work ok on the walls. I was thinking to avoid the "pillowy" shape one of the videos mentioned, I would cut some pieces of posterboard and staple to the corners to help stiffen those edges. I'm not sure about this design for the ones I hang from the ceiling. I would think the cloth should be strong enough to support the weight of the Roxul, but am interested in your thoughts on it.

Without my checking the reflection points yet, for the ceiling panel(s) do you think I may be better off trying to pick up some additional 1x3(or 4) and make 1 panel that is 94" in length, or make them separate panels just like the wall ones, and potentially space them apart?

There are so many great construction threads and theater builds on this forum. I really appreciate the advice being given.

Dave