Chime in!!!! - Thinking of some listening space changes......

[canyoneagle]

I've been thinking of rearranging the living room / listening space, and would love to hear some of your thoughts.

My present listening space is about 13-14 feet wide and open in the rear and on one side (there is a side wall that is about 8 feet long from the front wall before opening up).  the ceiling starts at 8' at the front wall (where the speakers are placed) and vaults to about 16' at the mid-point of the open space (about 15 feet from the front wall).  From this high point there is a wall that extends down to an 8' ceiling for the open space behind the listening area.  Kinda hard to describe........


                                                                                                                "X" = SPEAKER
                                       
                                       <----  low ceiling (8')  --->          16'  <---- vaulted ----> 8'
                                  +=========================+----------------------------+
                                  [                                              .                                         ]
                                  [                                              .                                    X   ]
                                  [                                              . <-- wall (above 8' only)        ]
                                  [                                              .                                         ]       ^
                                  [                                              .                                         ]
                                  [         OPEN to listening area  --->.       LISTENING AREA            ]  13' - 14'
                                  [                                              .                                         ]
                                  [                                              .                                         ]       v
                                  [                                              .                                         ]
                                  [                                              .                                    X   ]
                                  [                                              .        OPEN                          ]
                                  +============      ==========+           V              ---------+
                                  [                                                                                        ]   

                                                                                 /\    <------- 15-16'  ---->     /\


Here's a cross-section:
                                                                                                                            '

                                                                                 T---__
                                                                                 ]        ---__
                                                                                 ]                ---__
                                                                                 ]                       ---___
                                  ==========================]                                ---___
                                  ]                                              i                                        [
                                  ]      4'x7'   plywood painting--->   i       O           O                  [
                                  ]                (free hanging)           i                                  X     [
                                  ]                                                                                X     [
                                  ]__________________________________________________X_  _[

                                                                                        ^            ^            ^
                                                             Std. listening location             I             I
                                                                                   "Critical" listening"          I
                                                                                                               Speakers

As it is, there is a distinct rolloff in bass response in either of the listening locations (although it is a bit better in the "critical" position).  The bass is noticeably deeper (and better) anywhere in the room with the low ceiling, but it immediately drops off when entering the room with the high ceiling.

So, I've been considering reversing the setup, with the speakers 2-3' in front of the hanging plywood painting (below the "high" point , with the listening area in front of the lower wall.  This would mean that the rear ports of the speakers woud essentially be in free space, with the entire "low ceiling" room behind them, and the speakers would be positioned outside the plywood (no hard surfaces directly behind them).  Any thoughts?

I've considered aligning the system along the long wall, but I would not be able to get the speakers very far out.

Thanks for any input!
Warmly,
Michael

[richidoo]

Damn Michael! That is a masterpiece of text char illustration!

The low ceiling causes reflections and resulting nodes that are reinforcing a frequency that needs bumping. 8 foot node is 70Hz. Use modecalc to take a look at what frequencies are dominating your room.
http://www.realtraps.com/modecalc.htm

I can picture what you are proposing. If the short room is well padded with decorative absorbtion, it could work out pretty well. It gets the speakers as far from the vertical walls as possible, kinda... The only thing I am worried about is the 16 foot peak. It is shaped like a horn, aimed right at your head and will create a significant distortion of midrange frequencies and amplify that for you along the way toward your head.  Getting the speakers' front baffles behind that drop wall (placed a little way into the short room) would be a  big help by putting less sound up into that horn, but the hanging picture might be in the way?

I think that tall acute angle corner is the reason why you are dissatisfied with the acoustics. The more acute the corner, the worse the midrange phase distortion it creates and the louder it is amplified. If you have a tall ladder climb up there and sing in different voices, high and low. You will hear how it is messing with your hifi. Then send your wife up there to do the same thing, and listen to how loud it is down below. Ask her to sing something really corny, like "You light up my life" Tell her it is the perfect frequency intervals for acoustic analysis. haha

Can you hang a big tapestry up there? You could put 2" thick absorbtion behind it, and that would quiet down the mids pretty well. The bigger the better. simplytapestries.com has some big ones that look pretty cool. A big rug would work too, you get the idea. It should be an inch or more thick to really cut down the mids down low enough to noticably improve things. You could hang up a big comforter to test the theory before buying something.

To boost bass in the room where it sounds weak, you actually add bass absorption in the corners. It is counter intuitive, but it works. The bass trapping evens out the bass response of the room, boosting frequencies that are too low and lowering frequencies that are too high.  You might need a lot of it to make a noticable dent. Putting it close to the speakers concentrates its effect by absorbing more sound before it has a chance to reflect, but the speakers must be placed next to the sidewall for that trick to work. Trapping works as a percentage of the reflective wall area, or as the precentage of corner length that is treated. Not just near the speakers, the whole inside of the enclosed space. In an open floorplan room like yours and mine, this amout of bass trapping can be difficult to achieve. Too much bass trapping behind the speakers (around the front wall) can also make the room sound dead in contrast to all the untreated sheetrock wall area which is still reflecting and maintaining a high room efficiency. Some speakers are more sensitive to this.  It is a try it and see proposition, but some basic guidelines are helpful.

Since the speakers are single drivers, you can get a lot closer to them and reduce the apparent room affect. Have you tried a 8 foot triangle in the short room? With speakers at the hanging picture, pointed into the short room, with you sitting close to them. Bass would be better too. Good luck!
Rich

[canyoneagle]

Thanks for the kind words on my digital architectural skillz   

Bpape made the same comment regarding the 'horn' shape, and I definitely hear it.  As it is now, we have a 4'x12' killim (flatweave) carpet hanging on the vetical wall (below the 16' peak).  one recommendation was to put something (foam roll, rockwool, etc) in front of the actual peak, and covering that with tapestry.  I've considered that, but havent done much about it YET.  My "critical" listening spot is about 6-7 feet from the drivers (the centers of the speakers are 7-8 feet apart), and that works pretty well, although the reflections can get intense if I'm listening at 'live performance' levels.  The surfaces behind and on the left (as one faces the speakers) are glass, with cloth-covered vertical blinds.  I can detect an improvement with the blinds closed, but still feel that I need to tame the reflection points on the sides and behind the speakers.

Are there any "DIY" solutions for sound panels?  I'm pretty handy, and would love to avoid spending a fortune on treatments (but if I MUST, I will......... )

The horn effect is most noticeable when sitting on the couch.  YIKES!

I'll check the tapestry site - as it happens, I'm needing to get some tapestries for our bedroom - we like tapestries as much as you guys do (from what I gather from other posts you've made).

Okay, time to do some experimenting!

Warmly,
Michael

[richidoo]

There is nothing special about the peak shape at the point, but it's the reflective surfaces coming down from the peak that are the problem. Being acute, they face each other more directly, so they echo more before the sound finally leaves. A 90 degree corner only ruins sound to a certain frequency, maybe 12-24" wavelength. But an acute angle will ruin sound into lower freqs and be more annoying. Blocking off the peak is one way to quiet it, ala 8th Nerve panels. But they are more appropriate for 90 angles. With an acute angle the reflections can occur farther down the wall, so covering one wall completely is better than blocking just the point. So treating one side of it as you are is good enough IMO...  You might be able to put something thicker and more absorbptive down into lower frequencies behind the rug. Or you could cover the whole drop wall in 2" fabric covered FG then hang the rug as a decorative element over it. Or maybe even just some cotton or FG behind the rug only. Adjusting the rug hangers for space behind might not be worth the effort.

Comforters are thick enough to tame midrange echo. Hang up every one you can find or borrow to see if mid echo is what is bothering you. Themore wall area you can cover the better. It's all temporary just so you can listen to the difference before and after with a lot of midrange absorbtion added. If you like it, the ceiling is usually the easiest place to put it if the decorator will allow. If not, the walls, but usually there are so many doors and windows and pictures there is less area and it can look cluttered.

DIY absorbtive panels require covering the absorptive medium to contain any loose FG particles or cotton dust,  then covering for appearance with sonically transparent fabric, and then a way to hang it safely. There are other design elements that can improve performance too. FG is stiff, especially Dow Corning 705, cotton is floppy but it has no FG shards, and works a tad better than FG. It can be bought in bulk from Sensible Sound Solutions. Commercially made absorber panels worthy of hifi usage will also have a thin layer of reflective plastic over the absorbtive media to prevent too much high frequency sounds from being absorbed. Thicker panels will absorb into lower frequencies. Panels placed with a gap behind them to the wall will absorb into lower frequencies. Placing a panel across a corner is ideal for bass trapping. It is a nice idea to build your own, but to be honest, you will be hard pressed to beat GIKs price if you try to duplicate their design and quality in small quantity. If you can do with something skimpy you can probably save money DIY. Local distributors carry the dow corning FG panels, you can find them on corning website. But raw FG panels are not really very cheap anyway. They can be hung from the wall with impaling hooks which may be the cheapest method, but a wooden frame is handy especially if you will be moving it around on the floor, etc.

[canyoneagle]

Yep, I've been to the GIK site, and it seems hard to beat the value there.  Ive also visited Bryan's website (Bpape), and am considering options.

I like the idea of using thick comforters, etc to experiment.  As it happens, my wife and son are out of town until Thursday, so I can envision blankets, comforters, etc to augment the carpets that are already hanging in the room.

The cool thing is that my wife is also a music lover, and is pretty understanding of my audio nervosa 

When she saw the new Omegaudio/Hudson "R" speaker cables, she said "those are gorgeous".

She's a keeper. 

Okay, time to sit in the room and think of stuff to do.......

Thanks again,
Michael

[bpape]

Lots of options in that room.  Gut tells me to continue to face the right side of the drawing.  Hitting that acute corner is an excellent place to kill bass resonances if you straddle that corner with something at least 4" thick.  I agree with Rich that the flat wall also needs to be addressed.  The issue with 2" is that it doesn't do a lot be lot below about 175Hz or so.  Deep male voices will go lower than that.  If you do 2' wide straddling that whole corner, you might be able to do just 2" on that wall or a mix of 2" and diffusion.

Bass absorbtion can increase apparent bass level and depth and help smooth response abberations if done properly.  The way it works is that it keeps the bass from cancelling itself out or reinforcing itself - hence, smoother, deeper, increased HEARD bass.  The bass is always there - it's just that a lot of it get's cancelled out at times.

Another thing you can do to get a HUGE soundstage in a room like that when facing right is to use diffusion on the slanted ceiling.

The last thing you'll likely need to address is the rear wall behind the seating position. This will need to happen either way.  Some of the deepest and worst nulls many times come off that rear wall.  With the distances you have, it can be very low.  6" panels would be an excellent choice.

You can certainly DIY panels if you want.  There are a variety of materials to choose from.  OC703, mineral wool, and acoustical cotton all have excellent properites and each has their place though in some cases, they're pretty much interchangable.

Just be careful with doing the blanket thing and making decisions based on that.  They'll be pretty much upper mid and high frequency absorbant only so it's not going to help the bass issues and it's going to skew the decay time across the spectrum a bit so things may sound 'dead and muddy' to a point.  You'll just have to concentrate on the imaging/high frequency stuff.

Also, if you just want to play, go buy a few rolls of insulation, leave them in the bags and stack them in your vertical corners.  That's something you can play with and balance things a bit and then return.

Just a few thoughts.

Bryan

[canyoneagle]

Thanks for the input, Bryan.  You are the acoustimaster 

On my "play evening", I tacked a couple of foam mattress pads - one behind each speaker, and one on the side wall to cover 1st and 2nd reflection points. I hung a thick quilt across the front wall, and stacked thick cushions in the front corners.

My listening position was about 6-7' from the plane of the drivers (the centers of the drivers are 7' apart).

WOW!

The imaging, soundstage and tone were dramatically better.  The bass seemed more solid and smoother through the range.  This was an encouraging experiment!!!!!!!!

More soon,
Michael

[richidoo]

That's fun!! Now you're hooked! Acoustics is a great tangent/complement to the audio hobby. Because the more addicted you get to acoustic treatment, the higher your enjoyment and the less expensive your gear need be to achieve same listening high. Being FG and wood, it will never cost as much as transformers and tubes... but it can enable much greater performance of the system than incremental and expensive gear upgrades. Experimenting like you're doing is the best way to figure it out, even when you buy commercial treatments, where they go is discovered by ear.
Enjoy!!
Rich