DIY Room Treatment Projects

[jomari]

Firsthand, id like for you to learn more about the details regarding acoustic treatments, what certain terminology means, and of course, how to treat them. The theorems, research material, and discussion can be all found in my initial posting:

acoustic treatment research material

Lately we've had a number of discussions in regards to some issues we encounter with our home theater setups. Most of them found in our subwoofer sections as well.

There is a variety of postings that has covered the topic, and i invite others to chime in regarding acoustic treatments and our assortment of DIY projects to attain them.

I hope that we can discuss mostly about our building projects, and continue more discussion about acoustic theories in the first thread ive posted.

Will post further when i get back.

[jomari]

saved for future reference

[jomari]

yet another save for future references

[jomari]

heres another one!

[Big Daddy]

In the past few months, I have done a lot in the acoustic treatment area. Unfortunately, there is a huge beam that runs over the main listening area that divides the room. The HT room used to be a 2-door garage before it was fully converted. The beam has a length of 24 feet and runs across the room. Its width is 6" and hangs about 16" down from the ceiling. The projector is installed in the rear half of the room and it is lowered sufficiently so that the beam does not interfere with it.

ACOUSTIC FOAM & CORNER TRAPS

First, I treated the room with foam and coroner traps. I installed 4 corner traps in the four corners of the room. In addition, I added some foam to the ceiling area directly in the area in front of the main listening area and some on the side walls. I also put some acoustic foam on both sides of the beam. I cannot put anything on the ceiling directly on top of the listening area.

The quality of the sound, particularly the four subwoofers in my HT room became more defined and less tiring. For the first time in my life, I started hearing the speakers more than the room.

This is a picture of room treatment on the side wall and corner trap on top.

SUBWOOFER RISERS[/CENTER]

My next project was to build sub risers along the same line as the Gramma risers from Auralex. I called these DIY risers the Grampa risers. Details are in the Post #2 in the Repairing & Building Subwoofers thread.

I have four subwoofers in the room. Two are 12" round (23" diameter) Hsu subwoofers. One is a 15" DIY subwoofer and the last one is a 12" Acoustic Audio HD-Sub 12 subwoofer. I build two 20" x 20" square risers and two 24" round risers (10" height) for the Hsu subwoofers.

Wow ... just wow! The bass performance improved so much. I measured it with my old reliable Radio Shack SPL meter. The bass sound was close to 10db higher. I had to turn the volume on all the subwoofers down. I also adjusted the sub level in the receiver’s menus to -2db (yes, you read it right). Almost all speakers in the menu are set to negative numbers. The three front speakers are set to zero. I adjusted their levels with the dials on the external amplifier that runs them. The levels are perfectly matched.

I highly recommend risers to everyone. They help both front-firing and down-firing subwoofers. These classifications are in our heads. Waves are waves and go in every direction, particularly the long wavelengths of low frequency sound.

The biggest effect when you raise a subwoofer is that it may become a lot louder. The sound waves interact with the room boundaries (walls, floor, and ceiling) and create standing waves or room modes. The standing waves are different between floor and ceiling, side walls, and end walls, unless any of these dimensions are the same (the worst kind of room is a perfect cube). There are three basic types of modes: axial, tangential, and oblique.

Low frequency wavelengths are much longer (e.g., 56.5ft at 20Hz, 22.6ft at 50Hz, and 11.3ft at 100Hz) than higher frequency wavelengths (e.g., 3.8ft at 300Hz, 1.1ft at 1,000Hz, and 1 inch at 13,000Hz). This is important, especially below 150hz or so. Above 150hz, the waves are small enough that they are not affected by the room size as much. They bounce around every which way. Standing waves only become a significant problem at lower frequencies (below 100 Hz) because we normally set the crossover frequency around 85Hz. Long wavelength bass frequencies travel back and forth bouncing off the walls.

Axial Modes are the strongest and the most important, and the easiest to compute. Tangential Modes are about half as loud, and Oblique Modes are about a quarter as loud. They tend to be the least important, but if an oblique room mode occurs near another mode, that frequency may still be a problem. It is best to calculate all room modes to see where any overlap may be.

The three types of AXIAL modes are LENGTH, WIDTH, and HEIGHT. Knowing the speed of sound and the wavelengths of different frequencies, we can easily calculate these three types of axial modes.

When you move a subwoofer around a room, you are basically trying to deal with horizontal axial resonance modes (length and width). Almost everybody discovers this and tries to deal with it. Unfortunately, the vast majority of people are not aware that subwoofers and waves do not understand horizontal or vertical. By raising a subwoofer, you are actually dealing with the vertical (height) resonance mode.

To fully understand this, read A Guide to Subwoofers (Part II): Standing Waves & Room Modes.

DIFFUSERS

The last project was to build sound Diffusers and install them. Here is a picture of each diffuser.

So far, I have built 10 diffusers and installed them: 5 to the ceiling in the front of the main listening area, 1 to the left and 1 to the right side of the front wall, 2 to the ceiling behind the main listening area, and 1 to the wall directly behind the listening area. As I explained earlier, I could not attach anything directly above the listening are because of the beam.

Of all the crazy tweaks that I have done over the years, the diffusors have had the biggest impact. These are some changes that I noticed:

• The bass sound became more noticeable.
• The sound became three dimensional.
• Two-channel sound resembles surround sound.
• Almost all CD’s sound like live concerts.
• It appears everything is now in 360 degrees. Maybe, I just need to get rid of all the other speakers and keep only one speaker in the front.
• The sound stage has become focused in the middle. It used to favor the right side.
• The room became larger. The room sounds like a hall, restaurant, or theater.
• I don’t recognize my speakers anymore. It appears as if I have purchased new speakers.
• I don’t recognize the HT room anymore. It is a new experience.
• The speakers and the room have become less bright.
• I haven’t had a chance to watch many movies with the diffusors but the few that I have watched have become more enjoyable.
• Many people complain that they have trouble hearing the conversations from the center channel even when the speakers are fully calibrated. It has now become much easier to hear the center channel.
• If I have to use one word to describe the new room, it is MACHO. The room has become more macho.

It is going to take a while to get used to the new sound. I am going to experiment for a while and decide. I definitely like the sound of the movies more, but I am not 100% sure about the sound of two-channel CD music. Maybe, I should wait until my brain adjusts. After all, I have a separate two-channel room with upgraded speakers and a new DIY subwoofer.

I may eventually remove the two diffusers that are closer to the front speakers and move them to the ceiling behind the listening area.

I am tired of all the tweaking. It makes me laugh when people say that they are done with upgrades or they are in the final stages. Someone forgot to explain to me when that is. I have been upgrading, tweaking, wasting time and money since the time of Thomas Edison and I am not even half finished. Thank god for a patient wife.

[Driver_King]

My SDA's tend to do what you mentioned with two channel music- that is make the music seem like it is coming from everywhere. I only wonder what would happen if I made a few of those diffusers for my room. Where did you get that wood though BD? That would actually look nice in my bedroom.

[Big Daddy]

Originally Posted by Driver_King

My SDA's tend to do what you mentioned with two channel music- that is make the music seem like it is coming from everywhere. I only wonder what would happen if I made a few of those diffusers for my room. Where did you get that wood though BD? That would actually look nice in my bedroom.

I got them from Lowe's. CrazyBlue was correct. You make shelves with these, but Big Daddy is the great Improvisor or he may be completely crazy.

[Driver_King]

It looks like I could do this project (eventually). So how about four of these for my room? (Room is approximately 12' by 14' small )

[Big Daddy]

Originally Posted by Driver_King

It looks like I could do this project (eventually). So how about four of these for my room? (Room is approximately 12' by 14' small )

They come in two colors: maple and darker coffee like. I belive the normal price is around $24 because there was a sale sign when I bought them.

It is a good idea to put them over your listening area and to the rear. I couldn't do that because of the beam. It requires patience and experimentation.

[crazyBLUE]

Originally Posted by Big Daddy

They come in two colors: maple and darker coffee like. I belive the normal price is around $24 because there was a sale sign when I bought them.

It is a good idea to put them over your listening area and to the rear. I couldn't do that because of the beam. It requires patience and experimentation.

So for the diffusers it would be over the listening position & the acoustic panels would be over the front sound stage !!

[Big Daddy]

Originally Posted by crazyBLUE

So for the diffusers it would be over the listening position & the acoustic panels would be over the front sound stage !!

Most of the acoustic foams should probably go on the walls. Diffusers usually cover the listening area to the rear. Also some should go on the side walls. None of these are laws that are etched in stone. Every room is different. I can't do anything about the beam, but I will continue to experiment. However, I need to take a break and watch a few movies and enjoy myself. I am getting sick of all these tweakings.

[crazyBLUE]

Originally Posted by Big Daddy

Most of the acoustic foams should probably go on the walls. Diffusers usually cover the listening area to the rear. None of these are laws that are etched in stone. Every room is different. I can't do anything about the beam, but I will continue to experiment. However, I need to take a break and watch a few movies and enjoy myself. I am getting sick of all these tweakings.

I know how you feel believe me ! Out of all the moving ~ tweeking ~ experimenting ~adjusting ~ I've done in last 3 months , If I have not found it I am not going too !!

[Big Daddy]

These diagrams may be helpful or they may confuse you completely.

Reflections.jpg

Absorption.jpg

Diffusion.jpg

Echo.jpg

Treatment.jpg

[crazyBLUE]

That doe's not confuse me in the least ! It makes total sense to me !! Thanks because soon I'll be using this post !!!

[liquidice]

that's a great diagram to follow. I'm guessing here, but I would think you could buy those shelves from Lowe's, and after attaching to the wall, actually place some objects of decoration on them, and it wouldn't necessarily hurt the purpose of the diffuser/shelf. Like little candles or something. Even better, maybe you could cut out the exact dimension of the internal squares of the shelf using absorption material, and glue them to the wall within the shelf. Maybe two of those behind the listener would work? Just guessing here, and trying to find a solution to running this by the "other" one....from an astetics point.

[Big Daddy]

Originally Posted by liquidice

that's a great diagram to follow. I'm guessing here, but I would think you could buy those shelves from Lowe's, and after attaching to the wall, actually place some objects of decoration on them, and it wouldn't necessarily hurt the purpose of the diffuser/shelf. Like little candles or something. Even better, maybe you could cut out the exact dimension of the internal squares of the shelf using absorption material, and glue them to the wall within the shelf. Maybe two of those behind the listener would work? Just guessing here, and trying to find a solution to running this by the "other" one....from an astetics point.

Bookshelves, DVD racks, and those you mentioned help. Sound waves do not know the difference.

[jomari]

Originally Posted by crazyBLUE

So for the diffusers it would be over the listening position & the acoustic panels would be over the front sound stage !!

diffusers are mostly placed closer towards the rear of the room, to 'disperse' the sound produced by the speaker.

great diagram by the BD of course, simple and easy to understand. my compliments.

towards liquids inquiry, most of the times, some people actually would prefer to use bookshelves, and having unevenly organized books, trinkets and the like are used to diffuse the sound relative to what a diffuser does. its not a flat surface, its not uniform, but enough to bring out the characteristics of the speaker.

another thing to consider is that with diffusers tho, we want to acheive two objectives - either we disperse the sound without sacrificing quality, or we absorb it. diffusers can also help reduce echo and inconsistencies. but it can also cause it.

let me go by my previous example again.

imagining you are set in the middle of a quite busy lounge area. with a regular room, you can find yourself listening to the fronts quite clearly, hearing the conversation and able to distinguish certain sentences et al. you should also hear the ambiance in the rear of the room, as well as little nuisances that you wouldnt hear too much.

in a better acoustically treated room, not only will you understand the conversation, you would also distinguish whats being said in the back of your room as well, like chattering boxes surrounding you.

we dont want to color the sound, nor create an echoeing effect, which would give you that spatiality you wanted, but lose quality in the process.

just came from a gathering, so i wasnt able to work on my thread. give me a couple of days (sorry, trying to be human and live outside the net), and will try to compile more detail.

i was hoping for a sticky.

thank you of course to big daddy, crazyblue, and liquidice for heading over here for a great discussion, and hopefully, point us to learning more about this abandoned science in the home theater world.

[liquidice]

do you all see what I was getting at about the shelves though?

and then take some acoustic foam, and cut out the square pattern within the bookshelf/diffuser, and place the acoustic foam within those shelves: creating a diffuser/absorber panel. You would only be putting 4 pieces of foam in the complete squares of the shelf, not the outer half squares...does that make sense? I'm wondering how that would work? I'm already assuming it could work, but how would it sound? I don't think any of us would know unless we actually tried it. And so far, BD would be the only person to try it, but maybe I'm beginning to fall off the "CRAZY" end of all of this. Well, boundaries are meant to be pushed!

[liquidice]

found at least one here. Actually an interesting read. Nutshell: absorbes lower frequencies, diffuses mid and high frequencies, all in one panel. Interesting, I feel I'm on to something here with the "shelf-o-sorb-fuser" idea I'm trying to project into all your minds!!!

[crazyBLUE]

Originally Posted by liquidice

do you all see what I was getting at about the shelves though?

and then take some acoustic foam, and cut out the square pattern within the bookshelf/diffuser, and place the acoustic foam within those shelves: creating a diffuser/absorber panel. You would only be putting 4 pieces of foam in the complete squares of the shelf, not the outer half squares...does that make sense? I'm wondering how that would work? I'm already assuming it could work, but how would it sound? I don't think any of us would know unless we actually tried it. And so far, BD would be the only person to try it, but maybe I'm beginning to fall off the "CRAZY" end of all of this. Well, boundaries are meant to be pushed!

It makes sense to me & I also don't see why it would not work as both !