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#406257 - 07/19/14 10:04 PM Stupid Room Tricks
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5374
Loc: Bowmanville, Ontario, Canada
OK, so I ripped out some furniture in the living room and made room so I could move my 2-channel system out there and get some decent sound. Much better than the dining room with the low ceiling but still not great. Sound is decent, but imaging is iffy, bass is a bit boomy despite having the M40s almost 3 feet out from the wall, and whenever the music gets busy I get that "too many people talking" feeling where everything blurs together.

First step is noticing that speaker distance from side wall is the same as from back wall, and that the arms of the sofa between the speakers might be interfering with the midrange sounds from the speakers. That's what you get when you have an obsessive need for everything to be aligned & centered -- it's all scrunched in around the window.

Realize there's empty space off to the right if I move the rifle rack (I don't normally keep a rifle rack in my living room but I dumped it there after the last hunting trip and haven't gotten around to taking it down to the basement) so I move the right speaker over about 4 feet and left speaker over a foot or so. That leaves a bit more space between the speakers so the couch arms don't interfere, and lets me sit in the right hand seat of the listening sofa so *its* arms aren't interfering with the sound so much.



Bass is smoother, soundstage seems a bit better, but room is still too live. I already have a half dozen cushions from the couches & chair covering first reflection point on the left window and blocking some of the glass in the window on the rear wall, so I don't think it's just that. Start giving the ceiling the ol' hairy eyeball. The sloping-up part in front of me doesn't seem like the problem (angles don't work out) but the sloping-down part behind me seems like it could be acting like a VERY reflective back wall (it's that flattened stucco) in addition to the real back wall & window.

Next step is holding one of the cushions from the couch behind my head to block reflections from the back wall. Makes a bit of a difference but not much. Then I raise the cushion and angle it a bit so it blocks reflections from the lower half of the cathedral ceiling. All of a sudden things sound a lot better.

Not looking forward to prototyping something on the ceiling (peak is 20 feet up, and there's an inch or two of foil-backed foam insulation over the 2x12 rafters so even finding a rafter is going to be the opposite of fun. OK, so maybe I can build some kind of frame to hold a couple of cushions in the right place so I can do some proper listening without my arms bent back over my head.

Seems like too much work, but I go down to check the scrap lumber situation anyways. First thing I see is the roll-up mattress I take camping... hmmm.



It's "powerful ugly" but definitely improves the imaging. Now have a decent soundstage that doesn't fall apart if I move my head a few inches. Still gets too "busy" sometimes though, probably needs some more absorption. Owens Corning fiberglass doesn't seem real easy to find, but Roxul Safe n Sound seems like a decent substitute.

Pick up a pack of 24x48 batts, put a couple on the front wall behind the M40s and "eureka"... there was a dramatic difference even listening to the radio with only the batt on the right installed. Finally a decent listening area for the first time in ~20 years. Yay.



Yes I will make it all look nicer tomorrow. Anyone know a good source for cheap/suitable fabric around here ?

I figure 2 panels on the front wall, 2 panels replacing the mattress, 1 or 2 panels on the back wall, and 2 panels at the first reflection points of the HT upstairs and that will pretty much use up the pack of 8 batts. I can cut the last batt into 4 wedges and make a tiny bass trap for the front left corner of the room, but I'm thinking about just dumping a couple of cheap bales of fiberglass insulation there instead, at least until I figure out what the room needs. Seems like unopened bales of insulation should make good bass traps, anyone tried it ?


Edited by bridgman (07/19/14 10:18 PM)

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#406258 - 07/19/14 10:16 PM Re: Stupid Room Tricks [Re: bridgman]
Socketman Offline
connoisseur

Registered: 07/12/09
Posts: 1189
Loc: Whitehorse YT
Our local Walmart stocks some decent looking material worth a look if you have one near by . Pick up some lumber and get the staple gun fired up . Nick can probly add to this as he made some for his theater. You definitely have a room that is working against you.
_________________________
DOG is GOD spelled backwards.
I blame my terseness on my keyboard. smile

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#406259 - 07/19/14 10:24 PM Re: Stupid Room Tricks [Re: bridgman]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5374
Loc: Bowmanville, Ontario, Canada
Originally Posted By: Socketman
You definitely have a room that is working against you.

Yeah, I had to plan the house in a real hurry and didn't think about acoustics. The builder asked about stepping down the foundation for a home theater and I laughed at him -- "who would want a theater at home ?".

Even worse, I had an idea in the back of my head about putting up a separate building with a dedicated listening room in the imaginary future (you know the one where we have more money ?) and letting the Rives Audio folks go nuts with the design, but in hindsight I probably should have made a nice rectangular house with more walls, more golden rectangles, and fewer windows.


Edited by bridgman (07/19/14 10:26 PM)

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#406260 - 07/19/14 10:59 PM Re: Stupid Room Tricks [Re: bridgman]
nickbuol Offline
connoisseur

Registered: 09/16/04
Posts: 4447
Loc: Marion, IA
Hey, glad that you are getting things figured out acoustically.

My panels that I made were using custom printed fabric so that they were the standard "solid colored rectangle." A number of people over at AVS use this in a 24" x 36" panel that simulates a movie poster, but I opted for some custom artwork to span my panels.

The company is called Spoonflower.com and the two best products are Performance Knit (my personal favorite for acoustical purposes and great print quality) and Silky Faille for slightly crisper images, but a little sacrifice in acoustical performance (only noticeable with measuring equipment and software). The SF is a stiffer material that is a tad bit easier to get nice and square, but if you need to stretch it at all you are kind of out of luck because stretching it actually makes some noticeable distortions. The PK is more stretchy which makes it a little harder to get square, but easily fixed to make it right. That only matters if you have something, like those move poster images, that need to be square. With artwork it looks cool to have the whole image wrap around the sides like a painter's canvas.

If you want just a plain color for cheap locally (Spoonflower is really cheap for what you get, but obviously more than a plain color), you can use a basic solid muslin fabric (a bit too "industrial" for me), or really any fabric that you can literally blow through... Try putting the fabric up to your mouth and think, "If I was a hostage, and they put this over my mouth, would I be able to breathe, or would I pass out." smile If you can breathe through it, then you are pretty good for being passable for covering an absorption panel.

Just make a frame out of whatever wood material you want, take the fabric, lay it down, and warp the frame around to the back and staple it. Look for YouTube videos on canvas stretching for some good techniques.

Then put your insulation material inside.

Keep this in mind...

2" of material with a 2" air gap behind it performs almost as well as 4" of the same material but obviously the 2" is cheaper and the air is free. smile

I went with 2" of OC703 with a 1.5" air gap because I wanted to use readily available lumber and a 1x4 is .75" x 3.5". Works great.

Oh, and yes the Roxul Safe 'n Sound is a VERY common material to use for this application. You did good there!
_________________________
http://ht.buol.us
M60s, VP180, VP150, QS8s, SVS 20-39PCi, HTPC, JVC RS45, Onkyo TX-NR709, Shakers

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#406261 - 07/19/14 11:28 PM Re: Stupid Room Tricks [Re: bridgman]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5374
Loc: Bowmanville, Ontario, Canada
Thanks Nick. I hadn't thought about making the frame deep enough to include the air gap -- that's a great idea and takes care of the inevitable "gee why are your pictures sticking out from the wall ?" questions. Thanks !

I was eyeing another Roxul product at HD called ComfortBoard, probably more like OC 705 I guess ? 1.5" thick and definitely denser / more rigid than the Safe 'n Sound.

The room is feeling just a tiny bit too dead, although I'll let it "break in" for a while before I decide laugh

Guess after all these years I'll finally have to find out what muslin is. And go in a fabric store. Yikes.

EDIT - OK, so Wikipedia says :

1. Not to be confused with Muslim (knew that)

2. A cotton fabric of plain weave (didn't know that)


Edited by bridgman (07/19/14 11:51 PM)

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#406273 - 07/20/14 11:13 PM Re: Stupid Room Tricks [Re: bridgman]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5374
Loc: Bowmanville, Ontario, Canada
OK, took the "ugly" down a bit but still need to work on the "straight"...



The fabric isn't all that transparent (you can breathe through it easily but you know it's there) but I figure the room was a bit too dead anyways. The nice fabric store people looked at me really strangely when I asked for a sample to blow through.

Next time I'll ask for a sample then ask where the washrooms are wink

The panels are currently about 3/4" off the wall, but I'll pick up a couple of post base brackets from HD tomorrow and move them out a few inches.


Edited by bridgman (07/20/14 11:16 PM)

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#406288 - 07/21/14 08:06 PM Re: Stupid Room Tricks [Re: bridgman]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5374
Loc: Bowmanville, Ontario, Canada
You need a big trap if you want to catch big bass :



I tried putting double thickness (2 x 3.5") Safe 'n Sound across the main corners but didn't hear much difference. Walked around looking for where the bass was without the traps (just checked the immediate area, not down the street or anything) and for some reason it seemed to be mostly in one corner behind the left speaker.

So I figured if all the bass was there I might as well put all the SnS there too (a 24" x 48" x 24" pile) and *that* made a difference. Significantly less bass "boom" on certain low notes and generally better low-end sound all round. Call it half way between "before" and "ideal" which seems surprisingly good for a single treatment, even a big-ass one.

The M40's are really starting to live up to their potential (graph below is from a 2001 SoundStage review). Very impressive, especially considering they use them same drivers as M3's but with a larger enclosure and different tuning.



Edited by bridgman (07/21/14 08:17 PM)

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#406291 - 07/21/14 09:11 PM Re: Stupid Room Tricks [Re: bridgman]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5374
Loc: Bowmanville, Ontario, Canada
Originally Posted By: bridgman
... especially considering they use them same drivers as M3's ...

For clarity, my use of "them" in this sentence was a typo, not an attempt to sound folksy.

Originally Posted By: bridgman
Walked around looking for where the bass was without the traps (just checked the immediate area, not down the street or anything)

I learned to do this when Dennis ("Tharkun" ?) was trying to figure out why a pair of EP600's didn't seem to be producing much bass in his listening area. It turned out that a lot of the missing bass was ending up in a small room at the other end of the house, being used as an office and server room.

My first thought was that moving the EP600's into the server room might improve bass in the listening area, but I don't believe that theory was ever tested.


Edited by bridgman (07/21/14 09:12 PM)

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#406292 - 07/21/14 10:24 PM Re: Stupid Room Tricks [Re: bridgman]
Socketman Offline
connoisseur

Registered: 07/12/09
Posts: 1189
Loc: Whitehorse YT
Bass waves are super long and they do some crazy things. The waves come back on themselves and can cancel each other. I am just beginning to study all this on the internet and using software to analyze the room so I know ( hopefully ) what is happening to better address the situation. I am using an antimode in my bedroom and it works darn good. Since you are using towers without subs your only option is bass traps. Keep us posted as you progress.

Richard
_________________________
DOG is GOD spelled backwards.
I blame my terseness on my keyboard. smile

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#406299 - 07/22/14 12:59 PM Re: Stupid Room Tricks [Re: bridgman]
nickbuol Offline
connoisseur

Registered: 09/16/04
Posts: 4447
Loc: Marion, IA
Bass traps in corners should be at least 4" thick and "straddle" the corner to give a good air gap, or be something that completely fills the corner from floor to ceiling.

I went for the latter, because mine are hidden, but a nice framed floor to ceiling piece like the wall ones would look cleaner, but still feel a bit "odd" in a non-dedicated space.
_________________________
http://ht.buol.us
M60s, VP180, VP150, QS8s, SVS 20-39PCi, HTPC, JVC RS45, Onkyo TX-NR709, Shakers

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