Need acoustic design recommendations

[Raider]

Attached (I hope) is a crude drawing, not to exact scale, of the bonus room where I will be placing an HT system. The room is about 16.5 by 16.5 feet, though 2/3 of the wall adjacent to the stairs going down to the kitchen is an open banister and the stairwell effectively adds 3' to that dimension. A hallway continues off of the stairs and opens on the other end into a two story stairway and foyer. Parallel to the stairs off the bonus room, a ridge runs the center of the room where the peak of the ceiling at 10' runs the length of the room. The ceiling tapers to 8' at the wall adjacent to the attic. The walk-in attic runs the length of the room behind the wall opposite the stairs. The wall opposite the closets is about 2/3's windows from about a foot off the floor up to eight feet.

My question is this. What would be more likely the best acoustic orientation for the room. Should the TV be placed along the wall that is backed by the attic? Or should it be placed on the wall between the stairs and the attic?

What acoustic recommendations would you make? I had planned to use some owens-corning 703 panels I would make. I have also considered some sort of bass trap/ diffusor at the peak of the ceiling.

Any recommendations are appreciated.

Thanks

Raider

[DrWho]

hmmmm, I'm not seeing any picture?

[DrWho]

how's this?

[DrWho]

And definetly put the TV along the attic wall

[Raider]

DrWho

Why do you prefer this orientation (TV along the attic wall)?

[mas]

Although I certainly wish the stairway was enclosed and NOT a part of the listening room - as I would much prefer the front of the room to be facing to the left with the ceiling ridge running front to back, I think Doc is right. The LR room symmetry will take precedance and the rear downward sloping ceiling will be a pain to address.

I make the following recomendation in a general fashion - as it is insufficient to do this by feel!

With respect to the ceiling, iIdeally you would want to ab-fusors on the that portion of the deiling. Baring them (as they are quite expensive to purchase in the quantity needed, I would tend to go with a phase grating like that offered by Russ Berger's Space coupler.

The reason for this is simple. What most do not realize is that absorbers are only partially absorptive - and only at certain frequencies! They are actually more reflective than absorptive!!! And due to this characterisitic, there use ong the rear sloping ceiling contributes more to the problem rather than they would to correct the problem. Absorbers will be insufficient to sufficiently damp the hard focused specular Lre reflections. Therefore my effort would be to diffuse the the specular reflections and address the resultant scattered lower energy in other places. The phase grating would allow would efectively mitigate all but energy arriving at an angle perpendicular to the ceiling, which if the speakers are placed in the corners should be at a minimum. thus the majority of the energy would enter into the grating and reflect multiple times off the various incident angles of the grid, resulting in lower energy/ more diffuse reflections into the less critial areas of the room from the surface. Thereafter more diffusion on the side walls would further diffuse and lower the acoustic energy even more resulting in a more distributed and mixed decay of what formerlly high energy specular Lre reflections.

Of course, the ceiling is bit one aspect of a total system which would still be addressed in the standard fashion by identifying the hard early Lre reflections, identifying and surgically creating an initial signal delay gap and dealing with the early specular Lre reflections that must be removed to create this gap. Thus you would still want to address the early reflections, reducing their audible focused energy and using the energy to contribute to a more diffuse mixed field of lower intensity approximating a 'small' well-behaved decaying mixed sound field in the absence of a reverberant field.

Oh, and you will also have an interesting effect due to the rear stair well and the adjoining space. Its hard to say exactly what the best mix would be, but you would in general want to diffuse all the reflections off the back wall and I might attempt to make use of the adjoining space as a coupled space to lend an atmosphere of 'air' into the room - creating the sense of a larger space. But this takes a bit of doing to do it optimally. But at this point this concept is all philosophy, as it is in all practical aspects, impossible to model without measuring it.

Sound confusing? Its not that bad - especially if you can identify the actual reflections, their levels and time signatures. Then you can focus on real issues rather than concepts to address!! Its nice to have the proper tools! Otherwise it is pure philosophy and a touch of emotion - or, make that alot of emotion and a touch of philosophy.

And of course, you will want to address the LF modal response of the room with traps. Again, due to the irregularities of the room, you will need to measure these.

Well, I have jumped about and rambled enough.

If you are interested in learning the basics to this process, may I suggest checking out the reading in the Large and Small Room thread and joining us. Maybe we can get 3 or 4 folks to look at it before next summer and perhaps get to the point where we can actually discuss it [] []

[Raider]

Thanks guys for your input. To some degree, in regard to the surrounds, my speaker choice is being determined by the orientation of the room, for both acoustic and practical reasons. I've been waxing between the wide dispersion of the RS62's and using a tower (RF62 or RF82) because the more controlled directivity and ability to more easily move the speaker for acoustic reasons might be advantageous. I would REALLY appreciate you input on this issue at this point in time as I am trying to finalize my speaker selection. But the basic orientation of the room to me was step one.

I had concerns for either placement orientation as the ceiling will reflect directly to the listening area from the front speakers with either.

Since you guys think the orientation with the ridge running left to right is easier to cope with, I can better focus on the speaker selection. To some degree, I think you have to get a preliminary speaker placement in order to identify what problemns you have, absent any very sophisticated measurement and prediction software.

If pictures would be more helpful, I could try to take some, and post -if I can figure out how .

I plan to use this room as a learning tool, but I think if these thought processes are aired, and documented as I go along, it might help others with the same issues. Sort of a Klipsch lab. I have seen the willingness and generousity like this with several other folks projects. And I think the expertise available here .

I know of no other forum like this with such a diverse and broad support base, including even implemetation of the prodcut into the room.

[mas]

"Since you guys think the orientation with the ridge running left to right is easier to cope with, I can better focus on the speaker selection. To some degree, I think you have to get a preliminary speaker placement in order to identify what problems you have, absent any very sophisticated measurement and prediction software. "

No! This ceiling orientation is NOT easier to cope with! (that crazy guy said, jumping up and down!!! [][][])The ceiling ridge running from front to back is much preferable! The ridge reflections running front to back offer an oblique reflective angle where the reflections will be dispersed over a larger area rather than a hard reflective angle that is going to focus all of the vertical polar radiation down in a very concentrated area too near to the listening position - and the focused specular reflections will be of an intensity that they will be very audible unless adequately treated!!! It is just the the more easily addressable problem compared to the open staircase on a side wall - unless you want to completely enclose your staircase!!![]

But the more significant issue is the room symmetry with the right and left walls being similar, thus presenting similar reflections, etc increasing the consistency of the imaging. Having a stairway on one side and a 'smooth' wall on the other would be - well, who knows, but it wouldn't be pretty! Trust me, I don't like that ceiling orientation, but I hate the stairway being on one side and its impact on the LR imaging even more![]

As far as the ceiling goes, simply using lots of absorption will not work either (as most would be want to do!). The simple reason is that absorption is also amazingly relective - especially at incident angles other than 90 degrees! Absorption does not absorb all frequencies equally, and it reflects more than it absorbs. Thus diffusion will be a better way to go - in as much as you can both scatter the focused specular energy and reduce its intensity at the same time. And you are going to need ALLOT of it over the entire 'rear' ceiling surface. (Another option which I am sure that you, or the wife, or both, will not like, is to create a suspended ceiling using the phase gratings such as are marketed as Space Couplers by pArtScience and distributed by Auralex. RPG makes similar products as do several others. It would also present the subsantial benefit of both taming the ceiling reflection issue And creating a coupled space that would add to the semi-reverberant ambiance of a small room making it seem much larger...But sit down before you look at the price sheets. A good sedative might not be a bad idea either!) In any case this design would work well, especially if you considered mounting the gratings directly over a layer of absorption. Hint! A personal with a bit of initiative and ingenuity 'might' consider making them. Wink Wink Nudge Nudge. And a smart individual might ask how...but I am sure that they would have the discretion and good judgement to do so privately. That's my guess!

But, beyond that general recommendation I would need to make measurements, as to go further would be to be wandering about in the dark on emotion. But know that it is do-able and not as insurmountable as I may be making it sound.[] I just am very seriously opposed to the concept of just throwing lots of absorption around and assuming it will solve the problem. It won't!

As far as speaker placement - the classic corner placement toed in at ~45 degrees offers a myriad number of benefits, from minimizing (but not eliminating) side wall reflections to increasing the apparent efficiency of the speakers.

As I haven't looked, I am wondering aloud just where you are located...

It may be more involved then what you hoped, but may I invite you to take a look and jump on the Large & Small Room Acoustics Thread in the Architectural Forum. It is my desire (and still my intention - hey a fellow can dream can't he!?) to try to get this herd of cats to sit down and take baby steps until we have a group that has a good foundation in the basics of room behavior. From there we can take those same ideas and concepts and go in a variety of ways - from the micro approach to applying the concepts to transducers and speakers, to the macro of clusters and arrays of speakers and their interactions both with each other and with the room/environment...as well as as what the implications of the new measurements tell us...

BTW...I use exclamation points as one would use them on paper - simply for emphasis. I don't play by the silly Net rules where caps imply screaming or that "!!!" means something more than simple emphasis - so if this causes anyone to become apoplectic...ah, well, just get over it.[] [] Oh, and there is nothing on this site that can make me mad - frustrated, disgusted, indifferent... sure...but never mad! (OK, after a PM, that does not mean 'insane'!) [][][]

[Raider]

Gee MAS I didn't mean to make this an aerobic activity.

I initially didn't pick up from yours and Doc's comments that the main reason for the left to right ridge orientation was actually due to the open stairwell on the side, rather than the reflection issues off the ceiling.

I have carefully read Ethan Winer's material which I found to be a useful introduction to the various acoustic principles. Based on that reading I had already planned to try to incorporate diffusion where possible. I am also trying to design a panel that would combine absorption and diffusion. The trick is to find a visual aesthetic that will integrate with traditional architectural elements.

It would seem to me that for my particular situation that floorstanders in each corner of the room in a 5.1 setup might allow better control of dispersion and reflection, and also allow more miinute adjustment later on, than wall mounted surrounds might.

I am located in Nashville ,TN by the way.

I am working through the large/small thread, though I haven't interacted. Right thing at the right time for me. I plan to use this family/bonus/ht room to explore acoustics, while maintaining full functionality of the room, which I am finding to be a considerable form/function design challenge.

I took any punctuation and capitalization as an atttempt to communicate by a guy who's obviously passionate about the subject. I don't allow my self to get mad either, life's too short. and its usually a misunderstanding anyway limited by a one dimensional comminication medium.

Thanks for your input, as always.

[mas]

Raider, you have a PM...

[Raider]

Got it. Thanks MAS. I'll try to get with you this weekend, been kinda busy.

[DrWho]

I initially didn't pick up from yours and Doc's comments that the main reason for the left to right ridge orientation was actually due to the open stairwell on the side, rather than the reflection issues off the ceiling.

lol - you give me too much credit. I thought the ceiling ridge orientation was going the other way - but now I remember having this discussion. You can get away with the downward sloped rear-ceiling if you're willing to put in the time and effort to do it right. It can quickly become a complicated issue (when is acoustics not complicated? lol), but I'm with MAS and would agree that a symmetrical stereo image is more important.

Theroretically though, couldn't you open up part of that attic wall at the top to help balance out the stereo symmetry? It's not like that entire wall is assymetrical. I can think of a lot of cool crazy crap you could do by opening up that wall - you could even just rip the drywall off and cover it with "grill cloth". And then you'd have plenty of room to do some crazy bass trapping and a rear access to your equipment rack on that wall too.