[DougSmith]

This post is a bit long (hopefully to avoid a lot of back and forth clarification), but I will try to stay on point.
 
I have been researching ideas for upgrading the sound system in our living room for some months now.  The core of my present system is an old Marantz 2245 receiver and pair of Advent speakers; I also have a 46” LCD (Sharp D92).  I have a decent budget to work with and am close to making a decision on what to do (more on that later), but I am hoping that a little extra time spent on research will pay off in terms of a system that I will be truly happy with for some years to come, and not one that I will feel compelled to upgrade again within a year or two.

One of my challenges is the overall layout of my living room.  It is a fairly large room, nearly twice as long as it is wide (~15’ x 29’), has a cathedral ceiling (~40 degree slope; 13.5’ to peak, with four large beams across), a floor to ceiling brick fireplace at one end (8’ wide and extending into the room ~3’) and a large picture window, 5’x 6’ with flanking casements. The total volume is ~4,500 cu ft (see picture and floor plan).





The best setup for stereo listening seems to be with the speakers symmetrically aligned with the long the axis of the room (positions A in the floor plan –call that plan A).  However, there is no good way to integrate the TV into plan A, so it is currently located along one of the side walls and the speakers are located at positions B (plan B).  While plan B would permit both HT and stereo use, the speakers have to stay fairly close to the wall to avoid obstructing the traffic flow.  Plan B also has the drawback of early reflections from the window right behind the couch (on the other hand, the window helps with low frequency absorption).  I have tried both orientations and A seems slightly better, but the difference is not large as I thought it might be.  Nevertheless, the seated view of the fireplace and backyard through the picture window for plan A is nicer than the wall and TV for plan B.

Given this situation, I am now thinking that the best path forward is to have two separate speaker systems in the room, one for music listening (layout according to plan A) and one for 5.1 HT (according to plan B).  For the latter, I am assuming that precise virtual imaging will be less of a concern because of the multiple direct sources.  The drawbacks to this approach are the added cost and clutter of having more speakers in the room, but the surrounds for plan B, at least, can be placed fairly unobtrusively near the end walls (positions S in the floorplan).  Do folks think I am on the right track here? 

After a lot of reading and listening, I was very close to going ahead with some ported towers from a well-regarded custom manufacturer for the main speakers (and I still might do a scaled down version of that for HT).  I recently auditioned the Linkwitz Orion, however, and was very impressed by those - even without the rear tweeters.  I really liked the smooth integration, detailed, live sounding presentation and deep, fast bass response.  The Orion is at the top of my list right now, but I would also consider a constant directivity waveguide speaker, like Earl Geddes’ Abbey, which would probably provide a wider sweet spot.  I think both of these options address the problems of early sidewall reflections in a nice way without requiring a lot of room treatments.

On the subject of treatments, finally, there is a fair amount of broadband absorption in the main listening are due to the rug and two couches.  The surfaces in the rear of the room are fairly reflective, though, except for the open hallway (piano, walls, closet, sec desk & exposed floor - see picture). 



The walls are standard exterior construction with ½” wallboard.  There is still a fair amount of high frequency reverberation in the central listening area, but significantly less than there was without the area rug. Given that I will be using dipolar or directional waveguides, my plan is to avoid any further treatments in the main listening area, but maybe to add some additional bass absorption to the wall at the rear of the room.  I could also add some drapes to the large window.  What do folks think about this approach?   

Oh, I almost forgot... I should probably also mention that my wife uses the room for live music and recording as well.

-Doug

[bpape]

Hi Doug

Welcome to AC.

The one thing I see in the room that would benefit from treatment and stay out of the way is to have some panels hung up high, straddling the peak of the ceiling.  This will reduce decay time somewhat and also give you some broadband bass control while not taking any floor space.

Bryan

[DougSmith]

Thanks, Bryan,
You mean directly along the center axis under the peak?

-Doug

[bpape]

Yes.  They'd be hung with the 2'x4' face facing down toward the floor.

Bryan

[DougSmith]

So, I do have some questions about whether I really want broadband absorption or just bass absoption toward the rear of the room. I'm not so sure that the higher frequency reflections are a problem.

-Doug

[bpape]

Up there, its not going to hurt to have something more broadband.  Although, many of the panels that are designed to do bass duties are rolled off in the higher frequency absorption numbers.

Bryan

[Dave G]

Doug,

VERY nice room! 

Listen to Bryan -- he's a pro and knows what he's doing.  You might also contact Audio Circle member "Housteau," who also had to treat a room with a cathedral ceiling.  You can see some of what he did by checking out his gallery.

Good luck.

Dave

[youngho]

Wow, if you're looking at Linkwitz's and Geddes's speakers, you're playing with great quality. I assume you have some major DIY skills. There's a good discussion on www.diyaudio.com about a few issues that have come up while putting together the Abbeys.

A few thoughts and suggestions from an amateur:

1. With the Linkwitz Orions in position A, you might consider adding some broadband absorption to the wall behind the listening position. It looks like you could almost build out a little of the wall above the closet, maybe 4-8", put in quite a bit of fiberglass (at least 3-4") perhaps with an air gap behind it, and cover it with a light-colored acoustically translucent cloth to deaden the back wall slightly. Linkwitz himself seems to favor absorption at the rear wall ("Sound should just rush by the listener and disappear"). Floyd Toole also recommends absorption behind the listening position. I might pull forward the cabinet that is to the right of the and also put some broadband absorption into the back of that nook or else around the cabinet. The corner of the nook also looks like an unobtrusive place to put in a little bass trapping (a panel straddling the corner, even a Tube Trap). Broadband is probably preferable for the rear wall because of the significant reverbation that you're still noticing. In addition, some degree of acoustic symmetry is typically beneficial, and the entry on the other side of the closet acts essentially like a near-perfect absorber. However, if you really desire bass absorption only, another option would be something like the RPG Modex Plate, which would be pretty unobtrusive visually.

2. It doesn't look like there's much space to put any diffusion on the sidewalls in front of the bookshelves. The RPG BAD panels don't look to be super-effective, but might be better than nothing if you do use dipoles at position A, and they're pretty unobtrusive if you get them covered in a light cloth. I'd assume you wouldn't want a 4-8" deep diffusion panel here.

3. For your home theater setup with main speakers positioned at B, you might consider wall-mounted bipoles flanking the window behind the couch, since the surround locations you indicate would be so far away. Another wall-mounted option using the same location might be to use the Magnepan home theater panels (either the MMG W or MC1) which would be rather severely toed in for the surrounds but have the advantage that when a person sits closer to one speaker than the other, he/she is actually sitting closer to the null of the closer speaker! These could fold flat against the wall when not in use. Of course, they would require a subwoofer. Anyway, worth considering...

4. Some ceiling treatment would likely be beneficial. Again, broadband absorption if your room is a little too live. Another option would be diffusion, although thick/deep diffusers are typically needed for true broadband action. If you chose diffusion, you might consider units for lateral, rather than hemispheric, diffusion to promote a feeling of spaciousness from lateral reflections, at least for stereo listening.

[youngho]

Oops, I missed that the ceiling is a little asymmetric with respect to the side walls. That's interesting.

[bpape]

I would agree that if budget and aesthetic considerations will allow, adding some diffusion to the lower parts of the angled ceiling would work very well in addition to the broadband covering the peak.

Bryan

[DougSmith]

Thanks, guys... it sounds like adding some absoption at the peak (maybe rolled off a bit as Bryan suggested) would help smooth out the low frequency nodes.   

Youngbo, the slope of the ceiling is indeed different by a few degrees on the two sides (good catch there) - not sure how much difference that makes.  Some of suggestions you made in (1) were things I have been mulling over.  For (2),  the bookshelves and objects behind speakers at position A will provide some diffusion there - I suppose I could think about adding more if that would help.  (3) Those are some interesting suggestions about surrounds. I have thought about and discounted several options so far. I thought that having them fairly far away might be a good thing, though.  For (4) what exacly were you referring to with regard to lateral diffusion?

Dave, I did find those pictures by Housteau previously. Some of the panels he has look similar to what Bryan was suggesting.  I don't care much for the look of the panels he has atop the walls and would opt for an alternate solution.  I'm sure his system sounds terrific, though.

-Doug

[youngho]

Again, please take any of my suggestions with many grains of salt. I am not a professional, only  an amateur enthusiast, although a reasonably well-read one.

1. I didn't know your thoughts, so I just wanted to offer a few of my own. Hope it didn't waste your time.

2. As you know, Linkwitz suggests diffusing the rear wave from the dipole. In your case, it appears as though the rear wave would bounce off the side wall into the bookshelves, which would indeed offer some diffusion. You do have a lot of reflective surfaces on the lateral walls, though, and so I thought you might consider something like the BAD panels on the side walls next the speakers at position A, which might even make for a little less slap echo when your wife plays guitar.

3. Having conventional surrounds far away does reduce the increase in loudness of the nearer loudspeaker that occurs when one sits off-center. However, sticking them in the corner and firing them down the length of a wall is far from ideal. Bipole wall-mounted speakers have an appropriate radiating pattern for such placement, but you'd want them closer to the listening position, which would put them at more appropriate angles relative to the listening position for a true sense of envelopment (110-130 degrees from forward are recommended). However, you had mentioned an interest in dipoles, and the idea of overtoeing-in in dipole speakers had always struck me as an elegant way to approach the problem of the nearer speaker being louder, and it puts the surrounds at a good angle, too. I hope my explanation was clear.

4. There is psychoacoustic evidence that lateral reflections from certain angles (centered on around 60 degrees from forward) tend to promote a perception of spaciousness. Linkwitz also refers to this on his website. Whether this is desirable is up to every individual. You might even decide that hemispheric diffusion is preferable because of the orthogonal orientation of the home theater setup. However, you had mentioned that your wife does enjoy playing and recording in this room, so I thought that you might want to avoid excessive absorption, and diffusion might help the reverberant field.

5. The differentially sloped ceiling isn't too a big deal. I didn't know whether the peak of the ceiling was exactly in the middle of the room, since it looks that way on one picture but not in the other. I also didn't know whether the angle of 90 degrees or acute. Anyway, even a sloped ceiling worked okay for Floyd Toole:
http://blog.audiovideointeriors.com/casual/106advice/

Once in a while, there's some discussion of how bass "builds up" or "collects" or "accumulates" in corners. I hate this metaphor. I like to think of it as the cumulative effects of two or three axial modes, where pressure gradients are maximal or near-maximal. In a room like this, would anyone argue that bass builds up in the ceiling corner, where there are no opposing parallel walls for the two halves of the ceiling?

Lastly, I assume you've considered the possibility of mounting a retracting screen behind the ceiling beam in front of the fireplace, as well as a projector below the last ceiling beam at the other end of the room.

[Ethan Winer]

I agree with Bryan about absorption under the peak, and the photo below shows what he means. This photo is my home recording studio, which has a high ceiling not unlike yours. I also agree with youngho about needing absorption directly behind your head. Reflections off the glass so close behind you are very damaging at all frequencies.

--Ethan

[DougSmith]

Youngho,
Your suggestions are quite helpful.  Point taken on the BAD panels (or something like those).  From what I have read, broadband diffusion is generally preferable to absorption at the front of a listening space to maintain a sense of spaciousness, which is definitely what I am after.  Some additional diffusion on the particular walls you mentioned to distribute reflected sound from the alcoves created by the fireplace sides seems like a good idea.  Bryan’s suggestion of adding some diffusion to the sloped ceiling also sounds reasonable, but cost could indeed be an issue.  The BAD panels would be fairly unobtrusive, being only 1 or 2 inches thick, but it seems they would soak up the lower frequencies rather than diffusing them.  Maybe that is not such a bad thing – but I’m not sure.  I am thinking also that adding some diffusion to the wall behind the TV would be a good idea.  Your suggestions for broadband absorption at the back are well taken (as Ethan also suggested, referring to the glass behind the listener in plan B, I think). Achieving perfect symmetry at the rear of the room is not possible, but your suggestions for adding some additional absorption behind or next to the secretary desk with glass doors it sound pretty good.  I was also thinking of replacing the closet doors with louvered panels would help avoid the direct reflections from there.

Dipole surrounds for plan B are an option I considered for a while and then dismissed for my application because the real benefit dipoles is in producing a diffuse sound field when they are mounted on a side wall, rather than a rear one as I have.  The hinged Magnepans are an interesting option I had not really considered (although I think I encountered them once before in my internet travels).  I could easily move the couch forward a bit to get the surrounds behind the listener a bit, but 100 degrees or so is probably best I can do.

The ceiling centerline is indeed in the center of the room.  The angle at the peak is about 108 degrees.  I wouldn’t propose that bass builds up there per se, but the general consensus seems to be that it is a good place to absorb it, evening out multiple nodes simultaneously.  Adding absorptive panels below the peak of a cathedral ceiling seems to be fairly popular, and effective.  However, your question is interesting… is this really the best place to locate such absorption in a room like this?  It seems that the main advantage is that it is a fairly unobtrusive place to put a bunch of panels.

The thought of hanging a screen from the beam which is about ~4’ in front of the fireplace did occur to me. In fact, there is a large Da-Lite screen for slide projection hiding behind that beam right now (with a wide angle lens, a projector sitting on the piano does a pretty good job of filling it – although I don’t take slide photos any more).  While adapting that location for HT at night is a viable option (perhaps also with a movable center channel speaker), I would probably still want to use the LCD most of the time for casual viewing – especially during the daytime.  Also, having a screen that close to the fireplace might be an issue when there is a fire burning, which happens quite frequently during the wintertime.  While adding a projector and better quality AT screen would add significant cost, eliminating the need for a second speaker system and allowing proper placement of surround and rear speakers has a lot going for it.  I will probably continue to mull this option over for a while.

- - - - - - - - -

Ethan,
Thanks for your input.  That picture from your studio is exactly what I interpreted Bryan’s advice to be.  I will definitely be looking for a good solution to create some broadband absorption at the back of the room.  If I go ahead with the HT system in plan B, I will most likely be adding some sort of sound absorbing curtains to cover the window at night.  What are your thoughts on diffusion vs absorption for a recording space?

-Doug

[youngho]

Doug, true broadband diffusion would probably require diffusers at least 8" thick. One thing to keep in mind is it can be difficult to predict how the fabric covering changes absorption as the angle of incidence moves away from normal (orthogonal to the panel). Random incidence absorption data is not as helpful here because the rear wave of the dipole is not random incidence. The amount of low frequency absorption would be pretty low from a 1" or 2" surface-mounted panel. Certainly not a critical point.

(edit: sorry, the angle of incidence thing was for fabric-covered absorption or diffusion panels)

In my suggestion of using the Magnepan panels directly flanking the windows, it's important to realize that you would not be using the dipole surrounds as dipole surrounds per se. The application for which you're dismissing them is not relevant here because you would actually be using them as atypical direct radiators with a dispersion pattern that would result in a wider "sweet spot" than typical direct radiators could afford. I first read about it in SoundStage years ago, but 6moons mentions it here: http://6moons.com/audioreviews/magnepan/mmgw.html. Anyway, I have no financial interest in Magnepan, but I thought this application might work well for your setup. Just wanted to give you an idea.

Asymmetric rooms are more difficult to predict. For example, both Everest's and Toole's books include examples of nonrectangular rooms where the modal pattern has been distorted such that a 1,0 mode no longer has an antinode in the corner with an obtuse angle. Since your room has a pentagonal cross-section, I would have to defer the analysis of node and antinode distribution to the experts with either computational or practical experience in these specific matters. Sometimes things don't go as predicted, and rules of thumb don't apply to all situations.

Anyway, if it were me, when it comes to room treatment, I'd probably consider:

1. Working on the wall where the entrance is to put in broadband absorption and create some degree of acoustic symmetry
2. Buying heavy velvet velour drapes to put behind the TV couch, which would also be good for light reflecting of the screen. You can open these up for stereo listening. Also put velour drapes over the windows flanking the TV for acoustic symmetry when listening to stereo. Distributing or spacing out absorption seems to be particularly helpful.
3. Buying the equipment, setting it up, and listening (and maybe measuring) before dragging out the tall ladder and putting too many holes in walls.
4. You didn't mention subwoofers. There's the Geddes approach, which involves four subwoofers randomly placed around the room, including at least one off the floor. Another option would be two smaller subwoofers flanking the TV couch for use in HT only (you could even drive one 90 degrees out of phase with the other a la Greisinger!).

Cheers, happy listening, and let us know how it all works out!

[Ethan Winer]

What are your thoughts on diffusion vs absorption for a recording space?

Unless a room is very small, diffusion is excellent. Your room is definitely large enough to benefit. The downside is cost. Good diffusion costs more than good absorption. If you haven't yet seen my video All About Diffusion it's probably worth watching. Find it on the RealTraps Videos page.

--Ethan

[DougSmith]

Well, more than a year has elapsed, and a new sound system, at least, has materialized in my living room.  I decided to go with a pair of Geddes Abbeys for the mains, located in positions “B”, but further apart so they form an approximate equilateral triangle with respect to the main listening position (center of the couch opposite).  I built the Abbeys from a kit; I also built a pair of subs to help level out the low end (I was planning on adding a third sub, but that now seems to be unnecessary based on measurements). 

The Abbeys are toed in at 45 degrees (as recommended) to provide the best frequency response, reduce early reflections from sidewalls closest to the speakers and to widen the stereo sweet spot.  This works quite effectively.  I listened to the speakers for several months without any subs and enjoyed them immensely, without really knowing what I was missing. But adding in the subs has made a big difference… here are some measurements: Abbeys only ; Subs added and optimized. 

I optimized the low frequency response by placing the two subs in asymmetrical positions (one up front between the mains but closer to the left speaker; one near the rear corner in the nook next to the fireplace) and by adding multiple tight PEQ filters at the position of peaks (some for the mains from 80-200Hz as well), plus some phase adjustment.  The resulting bass response is rich, smooth, deep and articulate.  The imaging is precise, and the soundstage is both wide and deep.  All without any special room treatments!  A waterfall plot is linked here.

I plan to add some heavier curtains (which may help reduce the generalized high frequency noise a bit).  I also need to find a replacement for the TV stand I currently have – either a low cabinet with smooth edges and doors to minimize diffraction, or nothing (mount the TV on the wall and put the electronics somewhere else). The latter would probably be better sound-wise, but more of a pain from the wiring point of view.  Another thing I have considered is replacing the wallboard in the area between the mains (behind the TV) with fabric-covered fiberglass panels to create a more absorptive front wall.  I’m curious what the acoustics experts here think about that idea, as well as whether it is still a good idea to put some absorption or diffusion up in the cathedral ceiling.

- Doug

[jimdgoulding]

Hi Doug.  As to speaker placement (my comments are related to front firing radiators only), it is commonly thought that the wider you can separate your speakers, the better.  I think the goal, rather, should be to find the best relationship of direct radiated information with what is arriving later courtesy of our rooms.  The payoff is image palpability (i.e. 3D thereness to include roundness) and ambience or hall sound recovery when it's a part of a recording.  It don't hurt on studio recordings neither. 

If you intend on sitting on your sofa, in my scenario, you should want to pull your speakers nearer to your position.  This is roughly equivalent to having your speakers wider and sitting further away but you should appreciate a more comfortable realness to things and expansion of space behind your speaker location.

Very nice room you have.

(later)  Oh, you added a post or I missed it somehow.  My suggestions were related to having your speakers in the vicinity of your fireplace and I think Geddes has a rear firing driver, no?  That is very likely a different horse.  I hate that you have to sit against a wall.  Not that I have a perfect listening room or anything.  Cheers.

[DougSmith]

Hi Doug.  As to speaker placement (my comments are related to front firing radiators only), it is commonly thought that the wider you can separate your speakers, the better.  I think the goal, rather, should be to find the best relationship of direct radiated information with what is arriving later courtesy of our rooms.  The payoff is image palpability (i.e. 3D thereness to include roundness) and ambience or hall sound recovery when it's a part of a recording.  It don't hurt on studio recordings neither. 

If you intend on sitting on your sofa, in my scenario, you should want to pull your speakers nearer to your position.  This is roughly equivalent to having your speakers wider and sitting further away but you should appreciate a more comfortable realness to things and expansion of space behind your speaker location.

Very nice room you have.

(later)  Oh, you added a post or I missed it somehow.  My suggestions were related to having your speakers in the vicinity of your fireplace and I think Geddes has a rear firing driver, no?  That is very likely a different horse.  I hate that you have to sit against a wall.  Not that I have a perfect listening room or anything.  Cheers.

The Abbeys have a 12" OS waveguide and 12" woofer.  The speakers are about as far out as I can put them; If I pull them out any farther my wife pushes them back - so we have reached a compromise with the front centers ~2' from the wall.  Earl Geddes' theories on directivity and small room acoustics and distortion perception are an interesting read.   Having the window at my back is not so bad; the imaging is slightly better if I sit up on the front edge of the couch, but the difference is small.  The current setup provides a nice degree of spaciousness in the sound.

- Doug