[rockdrummer]

Hello everyone.  I am a lurking new guy here on the acoustics circle.  I have built a few speakers and stands and usually participate on the GR research circle.  Anyway, I am going to start building my own total OB gr research speakers soon.  So far the only projects I have done are for family members.

Here are things I have "learned" recently.  They are par for the course when it comes to things like this.  Many opinions.

1.  Foam is fine.   
2.  Wood is fine.  Could they both be the same?  I assume wood is better.


I know the ob speakers need diffusers on the front wall.  That is where I will start.  (There is a large tv on the front wall also.)
What is making me afraid to begin is not a minimal lost investment of money and time, I'm more looking to do it right the first time. 

I want to go with what works.  I have read that I should build an 18"x18" panel.  I have seen many panels put together also.
I guess after reading many posts for a few days and finishing up with about 3 hours just now, I am simply afraid to pull the trigger on any.

I assume wood must be better than foam. 
I am willing to make a couple panels per side, so hanging heavier panels, or resting them on some kind of diy bass trap, etc.  (I have no clue what I would do) is fine.

Seating position is about 10-12 feet away from the front wall and I don't know where to begin calculations for anything.

One more thing, this has rambled, apologies.  When they say 2x2, is that taking into account the actual finished wood measurements?
And if someone needs to say "it is really difficult to say, you really need to just quit whining and pick one and try it, and tell us how it sounds!" I will.
 

Thanks for your time.
Ben

[Rob Babcock]

Well, wood is fine for a diffuser; heavy but easy to work with and inexpensive.  There are plans online for a QRD (quadratic root diffuser) and a bit of research will find plans for other kinds.  Foam can work work for diffusion at mid to higher frequencies but it's not great for absorption.  Just as a general rule of thumb, almost every room will benefit from bass trapping, particularly in corners, and it's good to have diffusion or absorption at first reflection points (side walls and ceiling, floor if you can- carpet helps).  In general terms smaller rooms tend to benefit from absorption more than diffusion.

The real pros can probably chime in with specific recommendations.   

[Hipper]

Hears a couple of good sources of info:

http://gikacoustics.co.uk/acoustic-advice/

http://realtraps.com/

A good book with lots of other tips is Jim Smiths 'Get Better Sound'.

Generally bass traps are the number one priority to deal principally with the lower frequencies, followed by reflection points and lastly diffusion. In my room anyway I found diffusion the 'icing on the cake' and it's less obvious what it really does. Dealing with bass is the most difficult as the lower frequency you go the more material you need and therefore the more intrusive it will be. The rewards though fully justify this as it will reveal the bass on the recordings and not of your room. The result is a musical bass that really sets up the rest of the music. I can't emphasise this enough!

The general procedure is to position your speakers and listening chair to get the best (flattest) frequency response in the bass area (say 0-500Hz range), then identify what you need in the way of acoustic treatment (others might say that using the room dimensions you can treat the room regardless of speakers etc.). You can do this listening to music and using your ears, with test tones and sound pressure meter, or suitable software and microphone (REW is a free software). Using REW and microphone is not easy to set up and learn but there's plenty of advice and is definitely the most accurate method. The whole business requires a fair amount of learning, time, and frustration!

I bought products from GIK Acoustics (as they operate in the UK) but I spent something like £3,000. I've no doubt I could spend more. For DIY most people seem to use fibreglass (Corning 703 for example), horrible stuff to work with.

[rockdrummer]

Thanks for the responses.  Much appreciated. 

I feel I have learned so much and I am still lost.  But that's the nature of this hobby.  Takes a while, and experience, to get somewhere.  At least for me.

I am still planning on diffusers on the front wall, but I also have decided that superchunk floor to ceiling bass traps using Roxul Safe n sound, in the front corners are also a necessary step to getting better sound too.

My room is basically my entire basement.  From the listening position, the front speakers are on a 14' wide wall.  Then behind the listening position is a large space open farther on both sides, measuring about 25' wide and the very back wall is only about 10 feet wide and is literally 45' from the front wall.  LONG ROOM.

Windows covering the listening portion on the right side with accordion shades.  So I would really like to start with the front wall and do as much as I can there because I really have no other good spots, to my rookie knowledge, that would make a big difference.

So to sum up this, long room with space behind the listener.  Planning diffuser and bass traps in front.  At least I will learn something there.

Again, really appreciate your help.  Of course, any correction in my thinking would be great.

Have a nice day.

Ben

[mresseguie]

Hello, Ben.

This may help you some:

I recently decided to make my own acoustic panels, so I watched some YouTube how to videos and tracked down some insulation material by Roxul. Finding the right Roxul product was a bit tricky since the hardware store in town only had experience with 'standard' insulation panels. I told them I want "A", so they ordered "B" for me. "B" turned out to be 4" thick soft rock wool that looked just like fiberglass insulation. I returned it and located a large wholesale supplier of all kinds of insulation in Portland, OR (90 miles away). I eventually went there and bought a package of "Rockboard 80" 4' x 2' panels--seven panels, I think.

I've made 4 panels so far. Two of them are 2'x4' and two are pillowcase-sized (17"x24"). The larger panels are framed by 1/2' thick x 2 3/8" wide moulding that I got at a discount. I didn't bother framing the pillowcase panels. I set them to the left and right of where my flat panel TV is mounted to my wall/directly behind my center channel speaker. My rear-ported center channel speaker sounds better now. [Though, not wonderful which makes me want to replace it!  ]

I'm slowly putting more together. I've discovered that some fabric is really cheap (pillowcases at ROSS/TJ MAX) and some is really expensive (fabric store). I may buy some sheets at Goodwill if I like the color. I may buy enough for two panels from a quilting supplies store cuz the colors are so cool (but not cheap). Seems like half the price is fabric, which seems crazy to me.

Anyway, my Rockboard 80 seems to do a nice job of correcting nasty reflection points.

Good luck with your schemes!

Michael

[JLM]

Start with the room, then treat it (if necessary).

With all that space I'd cut it back to give a space with dimensions that follow good ratios (more home work).  It's hard to keep proper height/width/depth ratios in basements (most have low headroom).  Floyd E. Toole's "Sound Reproduction" has good information on room design and lots on bass propagation.  Recommend walls/ceiling that don't absorb or transmit sound (double layered 5/8 inch drywall on 12 inch insulated staggered stud spacings would be really nice).  Avoid can lights.  Run dedicated 20 amps/12 gauge electrical circuits and use hospital grade receptacles.  Insulated around any ductwork that passes near and use lined/insulated flexible duct to the room.  I did most of this and don't need treatments (but don't have O.B.s).

2x2 is nominal.

[rockdrummer]

Great info.  Thanks again. 

I probably should have mentioned it is a finished basement.  I also don't know if I'm going to be able to lessen the space size-wise. 
I do have a dedicated circuit.  I have been most interested in the diy side of this hobby so building treatments is exciting. 
I will look for Toole's "Sound Reproduction". 

I will post pictures or at least results when I eventually get some.

Thanks.

Ben

[Glenn Kuras]

Foam can work work for diffusion at mid to higher frequencies but it's not great for absorption.

Acoustic foam will absorb the upper frequencies but will not diffuse. The key though is that, as you said, small rooms suffer more on the lower frequencies where foam will not work. For that you need proper bass trapping.
http://www.gikacoustics.com/video_bass-traps/

[rockdrummer]

Since posting I have decided I will still do superchunk corner traps and probably try skyline diffusers. I am looking forward to that type of project and I like the look. I assume the larger the frequency range diffused, the better?

Thanks again and when I finally get some results I will post them.
Ben

[Glenn Kuras]

Generally in a listening/control room you are better to use 1D (QRD) diffusion vs 2D (skyline). With a 2D it will scatter the sound to the sidewalls, ceiling and floor vs a 1D that will scatter to just the sidewalls.

[rockdrummer]

I understand the diffusion concept but struggle sifting through pros and cons concerning my speakers. Dipole with conventional drivers. Multiple sources seems to say planars should get 1d. Just going horizontal like you said Glenn. Does that benefit image and soundstage mostly? If so then maybe some tall 1d diffusers will be my plan.

I guess anything will probably be an improvement over nothing. I am liking 1d more and more.
Thanks and I will keep going!
Ben