First reflection without a wall – what’s the solution ???

john4618 · « **on:** 15 Sep 2004, 06:44 pm »

What’s the best way to handle a ‘no wall’ at first reflection situation, if at all ???

My room is L-shaped so I can put a panel at first reflection for my right tower speaker, but since there is no wall next to my left tower speaker should I put a free-standing panel next to the left speaker at the first reflection ???

If I do not put a free-standing panel next to the left speaker at the first reflection then there is a half-wall and an opening about 8 feet away so I’m thinking the sound will hit it and bounce all over, so I’m thinking a free-standing panel next to the left speaker is the solution – I don’t know a lot about room treatments so please set me straight, thanks.

MaxCast · « **Reply #1 on:** 15 Sep 2004, 07:03 pm »

The sound is bouncing around all over anyways

My guess would be to match the right wall with a panel for the left speaker.

warnerwh · « **Reply #2 on:** 16 Sep 2004, 01:57 am »

Everybody's room is different. Some say to damp the first reflection and others are against it. Room treatments/acoustics can easily make a Huge change in the sound. You'll have to try and see yourself. I had a similar situation in the last house with an open space on one side and with just treatment on the entire back wall had pretty good imaging. If it sounds unbalanced then the panel may sound better but I would put some 3 or 4 inch foam on the wall that is nearby myself.
You should read up on acoustics as you can take your system to the next level and then some for much less money than new amps, cables etc. I suspect many people keep trying things without addressing their acoustics or possibly they're stuck due to where their system is and the WAF. I've just finished a dedicated sound room and I'm sure nobody would want their living room to look like my sound room(except me).
A free tweak is to fiddle with speaker and/or listener position if you can. Closer to walls creates more bass, away from walls has better imaging and usually better frequency balance. This is a crude description but at least try changing position and angle of your speakers. This can yield large gains in sound quality. Good Luck

JLM · « **Reply #3 on:** 16 Sep 2004, 10:44 am »

Unless you always sit in the center of the auditorium during live concerts you'll never have perfect symmetry anyway, so why worry about it? Most folks prefer bigger rooms with side walls farther away. I'd just try for effective diffusion/absorption on the nearer side wall and call it a day.

Ethan Winer · « **Reply #4 on:** 16 Sep 2004, 02:15 pm »

John,

> What’s the best way to handle a ‘no wall’ at first reflection situation, if at all ??? <

Do nothing. If there's no wall on one side, then there are no first reflections on that side either. But don't ignore the first reflections off the ceiling.

--Ethan

PhilNYC · « **Reply #5 on:** 16 Sep 2004, 02:50 pm »

If you end up doing nothing for the opening, I'd make sure that the right wall has a highly absorptive panel and a significant bass trap in the right corner behind the speaker.

john4618 · « **Reply #6 on:** 16 Sep 2004, 06:28 pm »

Ethan:

>But don't ignore the first reflections off the ceiling.<

Exactly what do I use on ceiling that's not huge in size since this is in my living room. Would a 2'x4' sheet of owens corning 703 covered with cloth do a good job ???

Phil:

>I'd make sure that the right wall has a highly absorptive panel and a significant bass trap in the right corner behind the speaker.<

Sorry, but exactly what is a "highly absorptive panel" and "significant bass trap" ??? Would 2'x4' sheets of owens corning 703 covered with cloth qualify ???

I really need help about what/how to do room treatments, either DIY or purchased treatments. If I supply a photo will this better help you to help me – or, I just got done putting my entire living room and all my speakers into the CARA software but I can’t figure out how to use CARA to determine what room treatments to do. So if you also have CARA I could email you my .CAD file.

MaxCast · « **Reply #7 on:** 16 Sep 2004, 08:19 pm »

If you plan to buy, I would contact a seller of acoustic treatments give them your budget and go with thier recommendation if it makes sence to you. The mfgs here that sell accoustic products do a good job offering advise while walking the fine line of "not using sales pitches" in the general circles. Plus they make more of a living selling vs. offering diy advise.

If you plan to DIY, I would do a little more research and start with the rec's given in this thread. Ethan's website has much info you should read first. There is a good thread here that explains how to construct diy compressed fiberglass panels.

I'm thinking one or two on the right wall and one or two on the ceiling.?.

Ethan Winer · « **Reply #8 on:** 17 Sep 2004, 03:13 pm »

John,

> Exactly what do I use on ceiling that's not huge in size since this is in my living room. Would a 2'x4' sheet of owens corning 703 covered with cloth do a good job ??? <

How large a surface you need to cover depends directly on how far you are from the speakers and how far apart the speakers are. Do you know the mirror trick? Have a look at the Acoustics FAQ, second in the list on my Articles page:

www.ethanwiner.com/articles.html

In particular, see the sidebar "Creating an RFZ" which explains all about early reflections. It's listed in the Table of Contents at the top right.

--Ethan

PEB · « **Reply #9 on:** 18 Oct 2004, 02:28 pm »

The open left side is no reflection at all. I would not worry about what happens to the sound that exits that area.

I agree with Phil Lam. To match the acoustic hole on the left, you would want high absorption over as wide of bandwidth as possible at the right side 1st reflection.

Your own idea of a free panel on the left is a good one, because the right side's absorption will be less than 100%, nor fully effective below the midrange. So the extra panel "hardens up" the left side somewhat.

Also, I don't agree that the ceiling reflection is terribly important. Don't chase after that one if there is any SAF involved...

Finally, don't be surprised if the balance is pulled to the side opposite of what is intuitive. Reflections cause nodes AND nulls.

Mag · « **Reply #10 on:** 18 Oct 2004, 03:17 pm »

When I was using my L shaped living room I stuck two bookshelf speakers in that section of the room that seemed to do the trick. You can give that a try if you have some extra speakers lying around.

Inscrutable · « **Reply #11 on:** 19 Oct 2004, 09:07 am »

Carlman needs to pop in to this thread. He has a big open doorway on the right side of his listening room. He made a large folding screen with acoustic material, and covered it with somereasonably attractive fabric. It does improve things when he uses it (as well as cutting down dramatically on the sound radiating through the rest of the house).

Lost81 · « **Reply #12 on:** 19 Oct 2004, 09:29 am »

I too have a L-shaped room, the left side opens up to my closet and toilet, and the right side has the door to the room.

When the room door is open, it become a U-shaped room.
However, I don't think it will be very considerate of me to listen to my music with my door open, and so, I covered the rear of my door with sheets of 1/4" thick paper-backed styrofoam, on to which I glued on 4" thick acoustic wedges.

This has the effect of creating an acoustic "hole," mirroring the other (open passage) side of my room. I.e. it becomes a symmetrical "U" instead of the asymmetrical "L".

So, you either create an acoustic "hole" mimicking the physical passageway on the other side, or you create a portable acoustic barrier to "plug up" the open passage way during your listening sessions.

-Lost81

Tonto Yoder · « **Reply #13 on:** 19 Oct 2004, 10:24 am »

You can sometimes find used office panels--the ones that create padded cubicles in a larger office space--fairly cheaply. You MAY have to fashion some way of standing one panel up by creating some sort of legs, or hinge several together to make them self-supporting.

They're common on eBay, but generally in large amounts (i.e. enough to make an office!) but maybe you could find an orphan or two at a used office supply or thrift store.

Lost81 · « **Reply #14 on:** 19 Oct 2004, 10:40 am »

Quote from: Tonto Yoder

You can sometimes find used office panels--the ones that create padded cubicles in a larger office space... They're common on eBay, but generally in large amounts (i.e. enough to make an office!) but maybe you could find an orphan or two at a used office supply or thrift store.

Or, you can just work late one night and swipe a panel or two from the office

Imagine the look on your colleague's face the next morning when he finds one of his cubical walls missing

(Maybe he might not even notice

)

One thing's for sure, they are more difficult to haul out of the office than Milton's Swingline stapler

-Lost81

Tonto Yoder · « **Reply #15 on:** 19 Oct 2004, 11:08 am »

Quote from: Lost81

Or, you can just work late one night and swipe a panel or two from the office
-Lost81

Or just take one or two home each night and bring them back each morning??? One would need a BIG briefcase for this, but it might give the illusion of someone who REALLY takes work home from the office.

Kevin P · « **Reply #16 on:** 19 Oct 2004, 02:51 pm »

The first thing to start with is some measurements at the listening position. A analog Rat Shack meter & a test disk is all that is needed.

After measurements you will have a frame of reference for making improvements and you can measure afterwards to confirm your making progress (or not).

Getting some kind of barrier on one side can help because you will get at least some reflected energy and adding adsorption to the wall side will help. You might also consider asymetrical set-up of the speakers on the end where they are placed. You won't make any progress though until you have measurements.

orthobiz · « **Reply #17 on:** 20 Oct 2004, 01:16 am »

Watch the movie
Office Space
to see the effect of cubicle destruction
on coworkers.

biz

Carlman · « **Reply #18 on:** 20 Oct 2004, 03:22 am »

Quote from: Tonto Yoder

Damn that's HOT!
I want a sound room that looks just like that.

Once I add my audio PC I won't remember whether I'm at work or home...

Tonto Yoder · « **Reply #19 on:** 20 Oct 2004, 03:32 am »

Quote from: Carlman

[Damn that's HOT!
I want a sound room that looks just like that. Once I add my audio PC I won't remember whether I'm at work or home...

Hey, sailor, got a dollar?