[twitch54]

The back wall is a first reflection by definition.

interesting, for I don't see how the angle of incidence will equal the angle of reflection without encountering another surface before the listeners ear (accounting for toe-in of course) ??

As for the side-walls, it all depends on the room.  If you have a wide/shallow room, then no, the front and back walls are the major issues.  If you have a narrow/deep room then the converse is true.  There are a lot of factors that come into play including distance of speakers from surfaces, length/width/height ratios, symmetry, [non-]parallel surfaces, windows, partial walls, openings in walls, building materials, etc., etc., etc.  A basement with poured cement/rock walls has different issues than a stud and drywall room than a room with floor to ceiling glass windows.

If you have your seating against the back wall, diffusion won't help because diffusion needs distance to work.  Rule of thumb is 1 foot of space for each inch depth of the diffusion wells.  You have to take everything into account, one rule does not apply to all venues.

My room has 3 different back wall depths which causes asymmetry problems.

all good points ! rarely have I see di-poles correctly set up on 'long wall', there's usually compromise either with speaker placement , listening position or both !

[emailtim]

... for I don't see how the angle of incidence will equal the angle of reflection without encountering another surface before the listeners ear (accounting for toe-in of course) ??

Speakers do not beam on perfect tangent with absolutely no off-axis response like a tightly focused laser.  Once you take into account a speaker's off-axis response, it should be pretty obvious.  See the diagram. 

If you shoot pool, the queue can hit the target ball straight on or from behind by using the rail behind the target.  One shot is on-axis and one is off-axis with respect to the target. 

The backwall reflection is no different than the off-axis traces A and B being able to bounce off both side walls.



If you want to drive yourself nuts, check out baffle edge diffraction latencies.

[twitch54]

Speakers do not beam on perfect tangent with absolutely no off-axis response like a tightly focused laser.  Once you take into account a speaker's off-axis response, it should be pretty obvious.  See the diagram. 

If you shoot pool, the queue can hit the target ball straight on or from behind by using the rail behind the target.  One shot is on-axis and one is off-axis with respect to the target. 

The backwall reflection is no different than the off-axis traces A and B being able to bounce off both side walls.

again, you're right, for some reason I was getting all befuddled thinking the Op was dealing with di-pole, had to go back and re-read his opening post ....'open baffle' , my bad !

As for beaming, di-poles (stats) while not lasers are in fact 'beamers' !

[ccomplete]

Wow, lots of stuff to read. There is a lot of opposing information on the best practices given a room or desired effect. A completely neutral mixing environment will have a different goal than a leisurely listening space, at least for me.. I don’t necessarily need my personal system to be 100% neutral, as long as I think it sounds amazing. I’ve heard a lot of mixing rooms and they all seem to lack the soundstage of a well executed listening room. They sound like headphones.. accurate but I find listening rooms to be way more engaging and enjoyable. People argue that soundstage is in itself a coloration and binaural illusion created by the room and it’s treatment.. if thats the case I prefer the effect and enjoy it. I do think the flattest EQ is important though and that’s what I try to achieve with absorption, also to reduce smearing when needed.. and then with diffusion I use it to try to get the best desired soundstage and imaging.

What I was surprised about and the reason I started this post was the huge effect any sort of treatment had on the direct front wall (rear-wave) first reflection point.. with an amazing speaker like the Super V being pulled 6 ft into the well treated room and great gear behind it.. the depth just collapsed. It really made me start thinking about what actually causes the “illusion” of depth.. is it recorded in? How? Or is any soundstage depth really just 100% a product of the room. At every other first reflection point some kind of treatment seemed to enhance the soundstage for the better but this one specifically even with diffusion just totally flattened the front to back staging. I have to think that it’s a (desirable) product of room reflection latency at this point and I’m going to leave it untreated. Now I just have to move some stuff around to get rid of this annoying 6db peak at 400hz.

Has anyone else dealt with one piece of treatment that was a HUGE change more apparent than any other one?

[Tyson]

Absorption on the side walls and diffusion on the rear walls is usually ideal for OB speakers.  I run Super 7s in my downstairs system and this combo works really well for creating a realistic soundstage. 

The nice thing about this being a hobby is that you can experiment yourself and see what works best in your setup.  Theory is a great place to get started but experiment is really the final arbiter. 

[ccomplete]

Absorption on the side walls and diffusion on the rear walls is usually ideal for OB speakers.  I run Super 7s in my downstairs system and this combo works really well for creating a realistic soundstage. 

The nice thing about this being a hobby is that you can experiment yourself and see what works best in your setup.  Theory is a great place to get started but experiment is really the final arbiter.

I agree completely, that’s half the fun.  I made some absorption panels with scatter plates on the side walls and they worked out great. They’re hella cool looking too as a bonus.. This is also the first time I’ve ever implemented ceiling treatments and holy crap, what a great improvement.

[BobM]

I think one of the best accepted methods of applying room treatment is "Live End - Dead End"

- for normal box and horn speakers you generally want the dead end (absorption) to be around the speaker and the live end (diffusion) where you are seated.

- for OB and planers it is reversed. The live end (with diffusion) is around the speaker and the dead end (absorption) is around the listener.

- However, for both I think it would be wise to treat corners with bass traps, no matter where those corners might be.

[emailtim]

Vicoustic products have been popping up all over the place. 

Bass/Broadband trap products are now sporting scatter plates in multiple vendor's product lines (see corner wall traps).

There seems to be a trend towards more diffusion and hybrid absorption with diffusion in their product lines.

This is most likely to keep the room "live" but controlled.



GIK Acoustics has a myriad of scatter plate designs.





I even saw a post that the Japanese Acoustic Grove System wood dowel diffusers are now being offered in a hybrid version with absorption in the back.

[ccomplete]

Vicoustic products have been popping up all over the place. 

Bass/Broadband trap products are now sporting scatter plates in multiple vendor's product lines (see corner wall traps).

Yeah! That’s what I’ve found best for a good balance. I tried with absorption only on the sides and corners and it was very dead sounding and boring. My room doubles as a studio and I have to record the sound of the guitar amps I produce so having too dead a room doesn’t work out too well. It doesn’t sound like a natural environment.

I made these panels to cover up some side windows and deal with reflections, they’re turning out pretty well! I made the scatter plates out of plywood with my laser cutter and threw them over some roxul 60. I still need to cut a few more plates with my laser (especially for the corners) but it takes quite a while. The room is definitely a work in progress, we just moved in!

[emailtim]

...  I made these panels to cover up some side windows and deal with reflections, they’re turning out pretty well! I made the scatter plates out of plywood with my laser cutter and threw them over some roxul 60. ...

You may have a business opportunity there.  The companies so far are not selling the scatter plates by themselves so people can place them over their existing (DIY or commercial) absorbers.

How did you come up with your scatter design ?  I see some folks have posted the binary amplitude hole design that the RPG BAD panel use.  That is a lot of drilling.

[ccomplete]

You may have a business opportunity there.  The companies so far are not selling the scatter plates by themselves so people can place them over their existing (DIY or commercial) absorbers.

How did you come up with your scatter design ?  I see some folks have posted the binary amplitude hole design that the RPG BAD panel use.  That is a lot of drilling.

I thought about it but I would have to find the right material. I used 1/4” plywood but the stuff is so dense it takes my laser a little over an hour to cut all the holes. Hardwood could be cool but more expensive to find 1/4” panels. I think it would get pretty pricey for the time and costs involved. After doing it all myself the sticker shock of some off the shelf units went away completely. Plus I’m pretty busy building amps these days.

The design I basically eyeballed from a GIK design I liked and drew it in my vector program modified to fit a 12”x24” panel that would fit in my laser cutter. I wouldn’t want to use this design for sale since it is technically someone else’s.. plus circles take tremendously longer than straight lines to cut on the laser. This was just a personal project.

They turned out pretty nice in the living room, my girlfriend ended up wanting them out there as art pieces as well.