[oneinthepipe]

May I ask a few questions?  My room is very small; approximately 15.5 feet long X 15' wide, but the room narrows to 12.5' wide beyond 5' from the front wall.  The room has 8' ceilings.  There is approximately 200 square feet of floor space.  There are 2' X 4' X 4" bass traps diagonally mounted in the top corners, 2' X 4' X 2" acoustic panels behind the speakers, on the wall behind the listening position, at the first and second reflection points on the side walls, and at the first reflection point on the ceiling.  There are also (3) 2' X 4' X 1" acoustic panels adjoining the 2" panel on the ceiling (a 1" panel is behind the 2" panel, and the other two 1" panels are on the sides of the 2" and 1" panels, creating an 8' X 4' "multi-panel" that is suspended approximately 6" from the ceiling).  My system is two-channel audio.

I would like more bass absorption.

1) At what frequency ranges is plastic transparent to wavelengths?  Does the thickness of the plastic have any effect on the transparency? I was planning to stack or stand multiple panels of 2" 703 for bass traps.  Temporarily or permanently wrapping the panels in plastic would be more convenient than covering them in fabric. 

2) Do bass traps need to be placed symmetrically in a room?  The only places that I can put bass traps at floor level are a) in the corner near the left speaker, b) in the right rear corner of the room (where there is a three foot wide opening into an alcove), and c) behind my listening chair.

3) Would a bass trap behind my listening chair, which is four feet from the rear wall have any effect if the bass trap did not extend above the back of my chair?  I was considering making a 24" X 48" X 24" bass trap from (12) 2' X 4' X 2" 703 panels and laying the trap length-wise on the floor behind the chair.  The chair is leather-covered. 

4) Would bass traps in the two corners help or would they hinder symmetry?  The corners are diagonally opposite.  I can realistically make the bass trap a similar size to the prospective trap in the question above, i.e., 2' X 4' X 2'.  There isn't room for bass traps in the other corners at floor level, and there are already 2' X 4' X 4" traps in the four corners that extend down from the ceiling.

Thank you for your assistance.

[orthobiz]

Pics?

Paul

[bpape]

Symmetry left to right in front of you is important.  I'd not do the 2 diagonal corners unless the opposite corner in the front is open to another large space.

In the rear, it can certainly help in terms of decay times.  Whether it will help with frequency response will depend on whether or not that position is one causing a specfic issue.

There is also the option to do bass control down low on the front wall.

Bryan

[youngho]

May I ask a few questions?  My room is very small; approximately 15.5 feet long X 15' wide, but the room narrows to 12.5' wide beyond 5' from the front wall.  The room has 8' ceilings.  There is approximately 200 square feet of floor space.  There are 2' X 4' X 4" bass traps diagonally mounted in the top corners, 2' X 4' X 2" acoustic panels behind the speakers, on the wall behind the listening position, at the first and second reflection points on the side walls, and at the first reflection point on the ceiling.  There are also (3) 2' X 4' X 1" acoustic panels adjoining the 2" panel on the ceiling (a 1" panel is behind the 2" panel, and the other two 1" panels are on the sides of the 2" and 1" panels, creating an 8' X 4' "multi-panel" that is suspended approximately 6" from the ceiling).  My system is two-channel audio.

I would like more bass absorption.

It does look like you have a lot of absorption from the midrange on up. It's important to note that the 4" thick panels are broadband absorbers, not simply bass traps, unless you have something in front of the fiberglass.

1) At what frequency ranges is plastic transparent to wavelengths?  Does the thickness of the plastic have any effect on the transparency? I was planning to stack or stand multiple panels of 2" 703 for bass traps.  Temporarily or permanently wrapping the panels in plastic would be more convenient than covering them in fabric. 

Judging from the discussion of Tube Traps and FRK (Foil Reinforced Kraft) lined fiberglass panels in F Alton Everest's Master Handbook of Acoustics, my best guess would be below 400-500 Hz or so, but the effects may not be sharp in terms of that transition, nor necessarily linear. Thickness will have an effect (for glass, for example, see http://www.acousticalsurfaces.com/acoustic_IOI/101_13.htm and http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd240_e.html), since the calculation for diaphragmatic absorbers is based on surface density (wt per square ft of surface). The acoustical translucency of fabric seems to be pretty idiosyncratic and difficult to predict, based on the information presented in Floyd Toole's Sound Reproduction.

2) Do bass traps need to be placed symmetrically in a room?  The only places that I can put bass traps at floor level are a) in the corner near the left speaker, b) in the right rear corner of the room (where there is a three foot wide opening into an alcove), and c) behind my listening chair.

Not necessarily, if the primary objective is to address room modes, but many "bass traps" will significantly absorb non-bass frequencies, and symmetry is generally desirable there.

3) Would a bass trap behind my listening chair, which is four feet from the rear wall have any effect if the bass trap did not extend above the back of my chair?  I was considering making a 24" X 48" X 24" bass trap from (12) 2' X 4' X 2" 703 panels and laying the trap length-wise on the floor behind the chair.  The chair is leather-covered. 

Conceivably yes, if it's a true bass trap, but it's not clear to me that you're describing a true bass trap. Also, it would depend on locations of speakers and subwoofers (if any).

To be honest, it sounds like you might consider making some basic measurements so that you can tailor your efforts appropriately instead of  ending up with a completely fiberglass-padded room.

[oneinthepipe]

Thank you for you responses.

The speakers are Salk SongTower with ribbon tweeters.  There aren't any subwoofers. The rear of the speakers are 22" from the front wall and the centers of the drivers are 40" from the side walls.  The speakers are 7.5' apart, and the listening position is 7.5' from the speakers.  The speakers are slightly toed-in from pointing straight ahead. The listening position is 4' from the rear wall. I can move the speakers and the listening chair a little bit, but there isn't a lot of leeway.  I can't put a bass trap on the front wall between the speakers because there is a 5' opening to another room.  A while back, Bryan suggested diffusion on the ceiling, but my wife, who has been very accepting of the audio stuff, and many other of my interests, didn't seem to enthusiastic. She doesn't seem to mind the panels, however.

I don't know how to take sound measurements.  To be honest, although I downloaded Ethan's tone tracks, I couldn't figure out how to burn a CD that played the tracks on the CDP.  I plan to purchase a Behringer microphone after I figure out how to make a test CD or after I purchase a test CD.

I don't know if I have bass problems, but I have repeatedly read that there isn't any such thing as too much bass absorption.  The broadband absorption panels have made such an incredible improvement that I thought more bass absorption could only be helpful.  Hence, the questions about the plastic's transparency and location of the bass traps.  If the plastic or another facing only allowed bass frequencies to be absorbed, then symmertry might not be an issue, I thought, although I assume that I don't want to create additional reflective surfaces.  That is why I pondered the issue of whether a bass trap behind the chair, centered in the room, would have any positive effect.

If I were to "do it over again,"  I would have installed thicker broadband absorption in the corners.

I'll try to post some photos.  Please pardon the walls, etc.  I removed a built-in cabinet and chair molding and haven't started to refinish the walls.

Thank you for your responses.

[youngho]

That's a very interesting room. All the openings and windows make your situation different than a typical small room. What are those panels covered with? Looks almost like some sort of purple suede?

Do you have an iPod? If you know how to use iTunes, you could simply use that to transfer Ethan's MP3 files to your iPod and use that to play the test tones. Otherwise, most computers ship with some sort of CD-writing software like Roxio or Nero.

The simplest and crudest way to take measurements would be the Radio Shack SPL meter. If you have a laptop and a microphone, you could use ETF or Room EQ Wizard. If you don't have a microphone but you do have a laptop, Ethan does have a link to the NTI Minirator.

I do believe that your time and effort would be well spent learning about basic measurements, rather than adding more panels to your room at this point. However, I am no expert, so I'll let the experts steer you to the right course.

[Big Red Machine]

Speakers look great.

There are some things that got me excited.  Like the chance to make some absorptive window shutters, or something that can be folded into action or opened up for natural light.  It would be a fun project.

I think Mrs. Pipe has let you do quite a few things to the room already.  You are not far away from packaging the room into something both acoustically pleasing and aesthetically pleasing, IMO.

You can always buy a Ratshack meter and grab a tripod and run your sweeps manually with a clipboard.  Inputting into RoomEQ is better and I have not done it electronically, only manually input the numbers with correction factors.  So no expert here.  Funny thing with the measurement route is that you get hung up on making a nice curve versus what your ears like sometimes.  

You might be able to just add some triangular traps along the floor spaces behind the seating and some of the furniture as a less painful path.

Are the panels on the walls in frames or ?

[oneinthepipe]

That's a very interesting room. All the openings and windows make your situation different than a typical small room. What are those panels covered with? Looks almost like some sort of purple suede?The fabric is "suede-like".  I bought the panels from acoustimac, bfore I knew about the vendors here, but I had a good experience with Sal @ acoustimac, nonetheless.

Do you have an iPod? If you know how to use iTunes, you could simply use that to transfer Ethan's MP3 files to your iPod and use that to play the test tones. Otherwise, most computers ship with some sort of CD-writing software like Roxio or Nero.Yes, my daughter has an iPod.  I have Macintosh computers, including a MacBook Pro.  I am sure that there is a method of recording the disc.  I tried seven times.  I could play the disc on my computer but not in the Marantz CDP that I use as a transport.

The simplest and crudest way to take measurements would be the Radio Shack SPL meter. If you have a laptop and a microphone, you could use ETF or Room EQ Wizard. If you don't have a microphone but you do have a laptop, Ethan does have a link to the NTI Minirator.  I will order a microphone today.  Ethan recommended a Behringer 8000 on his site. 

I do believe that your time and effort would be well spent learning about basic measurements, rather than adding more panels to your room at this point. However, I am no expert, so I'll let the experts steer you to the right course. I appreciate your help.

[youngho]

Yes, my daughter has an iPod.  I have Macintosh computers, including a MacBook Pro.  I am sure that there is a method of recording the disc.  I tried seven times.  I could play the disc on my computer but not in the Marantz CDP that I use as a transport.

Depending on how old your Marantz CDP is, it may not be able to play MP3s. That's my guess. Are you normally able to play MP3 from CD? If not, you'd have to convert them to WAV files. You could use a minijack to RCA adapter to play the tones right from your laptop.

Best of luck!

[oneinthepipe]

Speakers look great.Thanks, BRM. As you know, I think, I am upgrading to the HT2 TL.  Since my children "gave" me these speakers for my birthday, Jim is also making the HT2 TL in pal dao, and the drivers will be mounted on black baffles, which will result in their appearance to be very similar to that of these ST RT.

There are some things that got me excited.  Like the chance to make some absorptive window shutters, or something that can be folded into action or opened up for natural light.  It would be a fun project.

I think Mrs. Pipe has let you do quite a few things to the room already.  You are not far away from packaging the room into something both acoustically pleasing and aesthetically pleasing, IMO.  Mrs. Pipe is very accommodating.  When I asked her if I could switch rooms with the living room, she reminded me how accommodating she has been by telling me to look in the driveway.  I think that she thinks that my car is another accommodation.  The room will eventually be painted in a shade of burgundy.  The panels should blend nicely.

You can always buy a Ratshack meter and grab a tripod and run your sweeps manually with a clipboard.  Inputting into RoomEQ is better and I have not done it electronically, only manually input the numbers with correction factors.  So no expert here.  Funny thing with the measurement route is that you get hung up on making a nice curve versus what your ears like sometimes.  

You might be able to just add some triangular traps along the floor spaces behind the seating and some of the furniture as a less painful path. I could fit traps behind my listening chair and under the cabinet holding the electronics, but there isn't much legroom under my desk.  Mrs. Pipe wouldn't care, however, if there were a couple of 2' X 4' X 2' traps.  If they were covered in plastic, she would expect me to eventually cover them in some purple fabric.

Are the panels on the walls in frames or ?  The panels have wood frames around the edges, then the frames/panels are slipped into the purple/burgundy covers, which are like bags with zippers, but fit very nicely.  The panels do not have backs, except the 1" panels on the ceiling have thin wood backs and the fabric, which is stapled to the backs, is a different material from but a similar color to the other panels.  The panels, except one of the panels behind my listening chair and three of the corner panels, are not attached directly to the walls but are hanging by wire from hooks in the ceiling.  The 2" panel that is attached to the wall is 2" away from the wall.

[oneinthepipe]

Yes, my daughter has an iPod.  I have Macintosh computers, including a MacBook Pro.  I am sure that there is a method of recording the disc.  I tried seven times.  I could play the disc on my computer but not in the Marantz CDP that I use as a transport.

Depending on how old your Marantz CDP is, it may not be able to play MP3s. That's my guess. Are you normally able to play MP3 from CD? If not, you'd have to convert them to WAV files. You could use a minijack to RCA adapter to play the tones right from your laptop.

Best of luck!

I never played an MP3 before.  I didn't even know the CD that I recorded was an MP3.  My daughter has a minijack to RCA adapter, however, for her iPod, and I will try that.  Thanks.

[bpape]

My guess is that some of what you're experiencing is more a matter of being out of balance than anything else.  There is a lot of thin/very thin absorption and little to nothing of any thickness.  I'd be looking at thickening up the panels over your head, in the corners, and behind you before I worried about adding anything else.

Bryan

[oneinthepipe]

My guess is that some of what you're experiencing is more a matter of being out of balance than anything else.  There is a lot of thin/very thin absorption and little to nothing of any thickness.  I'd be looking at thickening up the panels over your head, in the corners, and behind you before I worried about adding anything else.

Bryan

Bryan, that is something that I learned since reading this forum.  If I were to "do it all over again," every panel would be 4" or 6" thick, at a minimum.  Regardless, it appears that I am going to do it all over again. What thickness panels should I use to replace the suspect panels?   

Thank you.

[oneinthepipe]

Bryan:

If I need to increase a panel's thickness, do I need to replace the panel or can I attach another panel directly to the other panel, i.e., a 2" panel mounted directly in front of a 4" panel to achieve a 6" thickness?

[bpape]

Depending on the construction and the aesthetic considerations, you could just add additional thickness to the rear - provided there is no solid back on the panels in question.

Bryan

[Vinyl-Addict]

I'll offer my 0.02c which may parallel what others have said but here goes anyway:

1) Speakers are very close to the wall behind them. Pull them out a little farther into the room, at the very least soundstage will be improved. Toe the speakers in more so that they fire almost directly at you.

2) Room treatment doesn't have symmetry. I assume this is due to the furnishings in the room?
It would be best to position the panels lower if you don't add additional panels, especially the panels in the corners but as Brian said, you should use
4"-6" thick panels to maximize lower frequency absorption and the corners should definitely be addressed.

3)The right speaker is very close to that small alcove. If you haven't already tried moving the speaker farther away from it, give it a try and see if you like what you hear. I think pulling the speakers out into the room more will help considerably.

4)The last thing I see is probably the most challenging issue and that is the opening to the right side of your listening position. I had a room with an opening in a similar position and it always sounded "confused" megaphone like. Obviously closing it off or placing something there (more panels) would be ideal but you could try moving your chair toward the speakers a little more to see if that improves things.

Having said all that, I know it's tough to deal with acoustics in a less than ideal room so I hope you find a good solution and enjoy the results.

[oneinthepipe]

I can't pull the speakers out too much more from the front wall without moving the listening seat back toward the rear wall.  To compound my problem, I am replacing these speakers with speakers that are 5.5" deeper.  With a room this small, every few inches seems to matter, because I have to sit even closer to the speakers.  Anything closer than 6.5' is too close without toeing-in the speakers drastically.  I can move the right speaker further into the room, however, and move the listening chair and ceiling panels over to the left.  I suppose that I could treat the room more like a 12.5W X 15.5L room with an alcove rather than a 15W X 15.5L room that narrows.  However, I will then have a problem with the opening behind the speakers being off-center.

Regarding the toe-in, the current angle seems to provide the best soundstage/placement combination.  I previously had the speakers pointed inward much more, but the instrument/vocal placement was not as well-defined.  Even in a small room with semi-nearfield listening, the systems sounds good to me.  The bass seems tight and well-defined, and I think that the speakers transmission line is more forgiving to placement than a bass reflex design.  I don't have the  experience as a listener to notice if there are significant peaks or suck-outs, etc., but I know that I can't have too much low frequency absorption in a small room.  I ordered a microphone today and will try to measure the frequency response.

I plan to replace the panels in the corners, behind the listening position, and on the ceiling as Bryan advised.  I am going to pick up (24) unfinished panels of 2" 703 on Thursday from a local distributor.  I'll purchase the covers (and frames) that match my existing panels on-line.  What thickness panels should I use at the different locations? 

[oneinthepipe]

I bought (24) 2" OC 703 panels locally today.  Should I use 6" broadband traps or 8" broadband traps in the corners? 

I appreciate the advice that you have given to others and me.  Before I read this forum and installed the room treatments that I have currently, I thought the problem was with a previous pair of speakers  (they were a problem, but it wasn't the problem that I thought it was).

[oneinthepipe]

Thank you for your comments.  I followed Bryan's advice and increased the thickness of the panels on the ceiling, in the corners, and behind the listening position.  The only 2" thick panels that remain are on the side walls.  I also moved the speakers to the left of the room.  The ceiling has 32 sq. feet of 4" mineral wool, the front corners have 6" OC 703 ceiling to floor, the rear corners have 6" OC 703 ceiling to mid-wall, there are three 6" OC 703 panels against the rear wall, and there are 6" of OC 703 panels behind the speakers.  The room seemed a little dead, and I inserted sheets of very thin kraft paper in the fronts of the 6" panels in the front corners and behind the front 2" sheet in the panels behind the speakers.  The is a substantial improvement in sound.  I appreciate everyone's help.

[bpape]

Glad it worked out well for you.  It's all about a balanced absorption scheme.

Bryan