[bluemeanies]

Hello, I have a dedicated room for 2channel and HT, while using the same speakers for both venues. B&W 803 diamonds.
My acoustics are sound absorption behind my speakers surrounding the walls top to bottom (except for screen), Auralex difussers on the ceiling from the front of the speaker to the listening position..or sweet spot.
I am not complaining about how it sounds which IMO I think pretty damn good.
However as many here know one is always looking for improvement to squeeze ever bit of near perfection out of their system.
So I have been considering side wall difussers locating them a few feet in front of my speakers.
My room dimensions are 25' long. 8' in width with 6'5" ceilings at the screen and 10'.5" to the rear of the room. My speakers are 5' from the rear walls BUT b/c of room constraints they are only 1" from the side walls.
I used trianglization measuring the distance between the speakers to the prime seating position and have been enjoying a pseudo 3dimensional sound.
My thinking with adding the diffusors in front of the speaker would open the soundstage.
I wanted some opinions on this view/option.
Not worth it?, or would it make a difference?
Also any ideas on diy.
What kind of difussers...Fractual? Half tube type?

Thank you,
blue

[JLM]

I assume you meant that your speakers are 5 feet from the front (viewing) wall.

First I'd talk with GIK here at Audio Circle.

Those Auralex diffusors look worthless IMO.  Hollow plastic resonates more than it reflects.  The geometry is not random.  But at least they're light enough to be safely mounted overhead.  Most recommend absorption overhead and diffusion on side walls for direct radiating speakers.  Recommend reading Floyd Toole's "Sound Reproduction" for a good room acoustics primer.

Your room is very long.  Can you shorten it?  Note that width to length is almost exactly 1:3 (any simple ratios invite echo).  And average height is equal to width (also very bad).  As such the room will act like a tube (something designed to amplify sound as a wind instrument) in bass frequencies (in your case 45, 90, and 135 Hz based on the 25ft room length).  My room is nearly ideal for audio: 8ft x 13ft x 21ft (fabiano ratio) and I also started with the Cardas prescribed nearfield setup, so my speakers are close to the side walls too (center of drivers about 1.5ft from side walls, aimed in front of listening position). 

The best diffusors I've found are here:  pmerecords.com/Diffusor.cfm  They're DIY, 1.5ft square/23 pounds each, made of wood (far more inert than hollow plastic), use quadratic random depths, omnidirectional, and cheap/easy to build.

[JWL.GIK]

How thick is the absorption you are using? You didn't mention any bass trapping, which is one of the primary treatment strategies in most small rooms. If you don't yet have any bass traps, I'd start there before upgrading your diffusion situation.

That said, diffusion can certainly help you. Different types of diffusion will help in different tasks. These might help:
http://www.gikacoustics.com/decoding-diffusion-acoustic-solutions/
http://www.gikacoustics.com/diffusion-dimension-download-1d-2d-scattering/

[jk@home]

Speakers are 1" from side walls? Are you using absorption on all the wall reflect points now? Every time I have tried diffusion on the side wall reflect points, it may expand the soundstage, but at the expense of imaging and detail. With the speakers that close to the wall, I don't see how a QRD or PRD would work that well. But if you do get some, they can always be relocated to the front or rear wall.

Maybe a Poly or BAD panel? You could diy a polycylindrical real easy, with some 1/8" HDF board, just as an experiment.

[poseidonsvoice]

Blue,

I and others have enough questions from what you have written that a picture or pictures may be worth a thousand/million words. So please take some high quality snaps and upload them when you have time.

Best,
Anand.

[bluemeanies]

Will post back of room tomorrow
The screen is 8' wide
The speakers are 8'5" apart
The room fans out to a width of 10'5" at the rear
Two ceiling Hgts 6'9" & 6'3"

Thanks

[JLM]

Shocking!

I run really wide (voice coils about 18 inches from side walls) but have the speakers (with beaming 8 inch full range drivers) turned at roughly 50 degrees from the side walls).

I'd pull your speakers as far away from the side walls as possible to not block your view of the screen and angle them towards the listening position.


As set up I expect you're getting extreme bass reinforcement (bloated boom) and confused highs from the nearby side wall reflections blurring with the direct sound from the drivers. 

[jk@home]

Have you tried toeing in the speakers some? In a HT setup, the speakers are usually toed to the center point (but that is to hit multiple seats within the same axis). What is the manufacturer's recommendation for side wall spacing? I get that they have to be pulled apart not to block the screen, but maybe move them a touch closer?

[bluemeanies]

Shocking..I take that as a negative. As mentioned in my previous post I did outline the location of my speakers positioning. They are toed in about a half inch. Despite your assumption that the bass is is bloated and the high being a miss mash of confusion those are not the facts.
The room itself is NOT perfect rectangular room. It was designed along the line s of a movie theater where the walls open up as the room gets deeper.
Orginally the room was a garage with cement flooring.d
To give you an idea of its construction the materials were used from Auralex, the room is suspended on thick rubber U-boats, the ceiling does NOT come in contact with the original ceiling/joists. The walls are approximately 7.5" thick all around. Inside the walls are Auralex sheet block, mineral fiber insulation, with double drywall, .50" & 5/8" suspended using RC-8 resilient channel. Making the drywall suspended from the actual wall itself as well as the ceiling.
This application I feel is the reason my room is not boomy with bass and the highs are clear as glass.

Really JLM the overall sound is very nice and I think you would appreciate it.
As far as moving the speakers closer without blocking the view that won't happen. My view would be blocked and my speakers as is are only a little better than 8' apart.
I am sending a few more pictures and your opinions are appreciated...everyone's opinion.
However don't criticize something you have not heard. Many people, some audiophiles have listened to my system and have been very much impressed.
It may not be to your liking and I get that but for me it's my 2channel system

Thank you all,
blue

[bluemeanies]

[bluemeanies]

I have no idea why these photos are upside down...apologies.
I have posted album covers on the forum just fine.

[JakeJ]

All fixed.

[S Clark]

I suspect that JLM is reacting to just how your arrangement is so far from traditional practice.  His comments are justified by looking at the room.  Regardless of how you built the room,  speakers are incredibly too close to the sides.  I don't see how diffusers are going to help much.
You were asking for opinions.  Don't be upset if they don't match yours.

[bluemeanies]

Thanks...and I was not not upset.
I respect JLM's views and understand why he said what he did.
I wish I could move those 803's from the side walls.
What would be considered a minimum distance from the side walls?
I take your opinion to be true that diffusers would not make a difference.

Thanks,
blue

[S Clark]

Ok, I've got a better perspective on what you're trying to accomplish within the limitation of the room.  I don't see a reason for diffusers on the side walls, but a pair in the center of the screen when listening to stereo could have a positive effect.  I wonder if absorbers on the wall right next to the speakers could have a positive effect.  I've never heard of much positive about egg crate foam, but if you could move one of those panels in front of the speakers it might be worth the experiment.  Also bass traps were mentioned. I'd make those a high priority. 
Wow.  That's a tough layout to work with.  If I could wave my magic wand, I'd cut the screen size by 40%, move the speakers back and out, and move the listening chair forward to compensate for the smaller screen. 
Experiment and good luck.  I"m sure that there are some improvements to be found. 

[youngho]

Most folks would probably recommend at least a few feet from the nearest sidewall. It looks like you might be able to toe in the speakers a little and manage at least a few inches (preferably 3-4") of absorption starting at the side of the front of the speaker and extending out a few feet (preferably 3-4"), though you'd have to move the Sgt Pepper print. The first thing I thought of when seeing your room was page 21 of this: http://www.wghwoodworking.com/audio/LoudspeakersandRoomsPt2.pdf

However, if you like the way the room sounds now, then you might start with taking some basic measurements? Lateral reflections can enhance the perception of spaciousness, and you might find imaging to be narrower but more specific with the absorption.

Many would describe true diffusion as spreading reflections in both space and time, so it's usually recommended that such diffusers be positioned at a distance of at least a few times the lowest wavelengths diffused, which doesn't seem like much of an option in your space (maybe better towards the sides and top of the back of the room?). Many engineered surfaces scatter reflections in space but not time. It doesn't seem like this would be a big help right next to the speakers, though perhaps if you like the way it sounds now, you could experiment with buying four RPG Skyline-type devices (could start with cheap used or knockoff products, Vicoustic and Artnovion make some alternatives, otherwise there are the Auralex Prism and Sustain products) and putting two on each side wall right next to the speakers.

[Letitroll98]

Nice looking room.  I'll second the toe in suggestion, I have a similar front wall dimension and additional toe in worked for me on speakers that everyone says are supposed to fire straight ahead or a very slight toe.  The toe is angled a few feet behind my head, sort of the 1st go to in positioning toe in, it was my last choice, duh.  Mine are about two feet from the sidewall, so just my experience, YMMV, but I would definitely try it if you haven't already, could make your already excellent system even better.  I'll defer to the experts here, but with all the reflective pictures, have you considered absorption at the first reflection?

[jk@home]

To save space, and not have the panels partially blocking the speakers, you could build the sidewall absorbers into the wall, using Owens Corning 703. Never done it, but I imagine someone out there has (AVS forum probably has some examples).

[S Clark]

  I'll defer to the experts here, but with all the reflective pictures, have you considered absorption at the first reflection?

No expert here, but with the speakers next to the sidewalls, the first reflection point is inches in front of the speaker. 

[JLM]

Seriously if it were my room I'd start over.  Shorten the room then turn the layout 90 degrees so those speakers can breathe.  Throw out the treatments (foam looks like it would be effective but is all but useless and as I stated above the diffusors are worthless).  More (space in this case) is not always better.  How often is the room used by more than two?  Do you really use that second row of seating?  (Walls naturally create a bass reinforcement along them, so sitting that close would sound boomy.)  Again you really need to read "Sound Reproduction".

Treatments are just that, treatments (not a cure) for sick rooms/setups.  As stated above your room is shaped like a tube, which the laws of physics dictate must act like a resonator, so shorten the room.  And currently all the bass is generated from the same end of the room, further making it behave like a large musical wind instrument.  Think of moving your hand lengthwise in a shallow bathtub of water.  The waves move along the length of the tub.  When they come to the end they bounce back until they meet the next wave where they will either double in height (amplitude), cancel, or something in between.  That's how bass acts in any residentially sized room.  The shape of the room and where the sound is generated can make the effect worse.  Having a room with equal height/width or simple dimensional multiples just increases echo. Sorry, but your room/setup is the worse of all three factors.  Do a search for "swarm" here on Audio Circle and learn about distributed bass (also covered in Toole's "Sound Reproduction"). 

Some would run to EQ or DSP to "fix" the room/setup, but those methods should also be the last bandaid for the sick room/setup.  Ideally one should first develop the best possible room shape and size (bigger is better but not if shape is sacrificed).  Next would be to develop suitable setup/layout.  Speakers (shoes) would then be chosen to fit the room (foot).  Note that 99% of audiophiles "over buy" gear for the given room.  These steps would take care of 90% of the battle.  Then the room would be measured to find out if/what/where treatments could help.  (Vendors of course would love you to stuff the room with their products.)  Finally if absolutely "necessary" EQ or DSP could be applied (which can only correct for a single listening location and can be seriously "abused").