Acoustics of "L" Shaped Rooms?

[Grooves]

So, while I have not decided on which acoustic software program to use as yet I figured I could pick some brains re: my "L" shaped room and maybe what I am up against in trying to make it better.
My listening room is a living room with an attached dining room. My speakers are located at the front of the living room facing the usual length of the room. The dining room is at the front and the opening is about 1/3 the front length of the room. The right speaker has no right boundry/corner since it is located about mid opening of the dining room.
Can anyone share their experience with such a room and talk about some of the problems regarding acoustics and what I may have to look forward to in the way of tretments. I know since I have no acoustical data as yet it may be hard to predict but simply from the stand point of a "L" shaped room there must some things that are known.

 

[garylkoh]

Grooves, are you close to Seattle? We have a Pacific Northwest Audio Society that meet 2nd Thur of every month in Mercer Island. More information on this forum here or at the club's website www.audiosociety.org. The next meeting is 8th Mar - lots of knowledgeable members who may be able to help answer your question. The room we meet in (basement of a church) also has a strange shape and we've managed to make it work pretty well with rudimentary treatment.

 

[NorthStar]

I believe that Dr. Floyd E. Toole has some paper on 'L' shaped rooms,
and their acoustical effects plus the right speaker's positioning and even with multiple subs.

My last room was also an L shaped one,
and like you my main speakers were facing across the longest wall.
Three subs are good for rooms like these, I believe.
And room treatment is important on the short wall of the L shape.
Because one main speaker reflects from it. Best is to use maximum toe-in.
If your speakers were positioned like mine of course.

And listening position is tricky; you have to be inside the front main rectangle,
and use the 1/3, 1/5, 1/7, etc. formula.

But I'm not an expert; I only dealt with that kind of room for so many years.
And it ain't easy, but Gary above seems to be more positive than I. Perhaps.

If you can show me your floor plan with all your speakers and subs,
then I can tell you what I did experiment with for more than 15 years,
and what my best results were. Personally. And what I also learned from that process,
and from my readings, that I can now share in the hope that it can be helpful to you.

Yeah, your floorplan (picture) would be of great help if you could.
With all your furniture, opening(s) to adjacent rooms, and all that Jazz.

 

[Jeff Hedback]

Grooves, a floor plan would indeed be helpful. I have worked with this type situation multiple times and a key treatment point tends to be the areas behind and to the "open space" side of the speaker without the boundary. Of course, that is not always going to be the case. Here are a couple pics of a "similar" type room. My client already had a nice assortment of GIK and Ready Acoustics panels and the effort here was to test & tweak (with a few additional panels).

 

[DonH50]

Can you put your speakers against the other wall, away from the L opening?

My experience has been it is very diffcult to match the sound of two speakers loaded so differently. In the past I have lived with the opening and treated the walls behind the "open" speaker and walls behind and beside the "closed" speaker to try to get them close in frequency response and dispersion. It is almost impossible to match the bass of full-range speakers in this situation. (In my system, with dipole panels, it was nearly impossible to match anything.) One time I actually built a short false wall (a free-standing panel) for the "open" speaker to help the speakers match and that is probably the best I have done. The panel was about 3' - 4' wide and stuck out from the back wall to a little in front of the speaker so it didn't block the walking path. I filled it with mineral wool. Another client liked the idea and used a pair of glass storm doors mounted in a wood frame. Not the best acoustically, and neither scheme helped the deep bass all that much, but it's a suggestion...

I did not have Audyssey or anything like it back then; wonder how much something like that helps in this situation?

 

[Jeff Hedback]

additional thoughts

very good points Don. I did similar in this room.

A key point is the decay time in the 100Hz to 400Hz region. Often the lower bass is actually more unified because of the total cubic volume. But the decay time of the upper bass/lo-mid can be drastically different. First, this would cause a thicker/slower sonic experience. Next, the sound stage would vary too much from recording to recording (due to the lo-mid decay mismatch).

A "L" or even "open" plan is not always a bad thing, but there are definite trade-offs.

As for DRC, Trinnov could certainly help (and others I'm sure), but I might not look toward Audyssey at being able to adjust decay times like just described.

 

[microstrip]

So, while I have not decided on which acoustic software program to use as yet (...)

Grooves,
I have used the inexpensive Cara (Computer Aided Room Acoustics) to model my room. As far as I remember it supported L-shapped rooms. The user interface is user friendly and was very useful mainly to get an idea of the amount of surfaces I had to treat to get a decent RT60. Sometimes we even agreed about its suggestions for speaker placement!

http://www.rhintek.com/cara/cara21desc.php

 

[NorthStar]

I did not have Audyssey or anything like it back then; wonder how much something like that helps in this situation?

Hi Don,

In my L shaped room (from prior), I had Audyssey MultEQ XT (8 positions),
and even Audyssey had a very tough time to EQ the sound (speakers) in that room.
I was only engaging it with Movies, and not with Music as it was worst than without.
I did experiment a lot in that room; speakers positioning, some crucial room treatments,
and of course several Audyssey runs (many many ...).

I bet XT32 would help much more.

Also, the best option, IMHO, is to position your two front main loudspeakers on each side of the best corner, in that room, most likely the largest corner flanked by the two longest walls.
You know, with the center between your two speakers being the corner dead center.
So that way both speakers have a much more similar direct sound.

I know, it is weird to position them like that, but the reward is in the overall sound quality.
We're talking good acoustics here, and not the nicest aesthetics (decor).

Finally, some speakers are more appropriate for L shaped rooms,
like the ones having the port (vent) on front, so they can be nearer to walls.

Cheers,
Bob

 

[Grooves]

My speaker placement is kind of fixed in stone barring some really big improvement from experimenting. But it would have to be a BIG improvement since my TT shelf is fixed to the wall and my dedicated AC would have to be moved. Though Naim speaker cable is fairly cheap as speaker cables go, so moving the speakers without moving my gear is possible. My bass isn't slow but it can be "wooly" at times. I want better "layering" of the bass. The sound stage can move a bit at times but overall it isn't too bad. What I end up doing is moving my listening position forward or backward a bit depending upon the recording to off set too hot a treble or too much bass build up, though the latter changes the least.

I read some about the Cara software and how it can accommodate "L" shaped rooms. Is it worth buying that software in addition to buying XTZ or Omnimic? I could see where it might be an aid but I hoping to get away with oly buying one program if possible.

I will try and post some images or diagram if possible. Hell, I'm still trying to figure which software to buy!

 

[NorthStar]

Grooves, show us your floor plan first, and we'll take it from there.

We'll come up with good suggestions worth exploring.

Like that, in the blind, can't do it properly. Everything is important in your room.

Right now, you ain't buying nothing. We'll work within the confines of good acoustical sense first.
And that doesn't necessarily equate or compound to money.
And REW is free, and there are inexpensive separate EQs, like mini-DSPs, or others of that sort.
Behringer I believe has few.