[andycsb]

Bedroom is 10W x 15L x 9H.

Speakers on the short wall with equipment rack in between. Currently have 2' x 4' corner triangular bass traps on both corners of the front wall (wall behind speakers). 2' x 4' absorber panel on side wall first reflection points.

I have 2 absorber panels ( 2' x 4') leftover.

Shall I use them to treat:

a)   secondary reflection points on side walls

or

b)   1 panel in the center of wall and 1 panel in the center of the back wall

or

c)   1 panel behind each speaker (front wall). Front wall is only 10'. Therefore...2 bass traps plus 2 absorber panels will leave only a 2 feet gap in the center of the front wall......overdamping?

Won't be considering treating the ceiling.


Thank you guys for your help.

[JLM]

Here's a quick (and free) suggestion, just try various positions (sit them on the floor or on boxes to elevate). 

What works best is hard to say and is speaker dependent.  Probably the second side wall reflection points would benefit the most if your speakers are front firing with wide dispersion (typical).  But if dipole/bipole design I'd guess directly behind the speakers (as this is a small room the speakers will be closer to the front wall than recommended).

The LEDE (live end, dead end) theory was popular (still is to varying degrees) where the speaker end is fully treated and the opposite end is more reflective.

[andycsb]

@JLM...thanks for your suggestion. Forgot to mention that the entire front wall is draped..not a thick fabric. Covering some windows.

Treating primary and secondary reflection points on the side wall (ie 2 panels on each side wall) would be the "neater" option...ie...room looks less like a studio.... I am secretly hoping that it will be the configuraton that will yield the best results. Better imaging, smoother top end and fuller sound.

Anymore suggestions?

[jimtranr]

How close is your listening position to the back wall? If it's fairly close, then  treating the back wall may be a better option than the second reflection points.

[andycsb]

@jimtranr...the back wall is actually a floor to ceiling wardrobe. There is a bed that is very close alongside it. Listening position about 4' from the wardrobe. If I do treat it with one panel, it would have to be temporary because of the wardrobe that is the back wall.

Have been reading up on past postings in Acoustic Circle about SBIR. What does SBIR sound like?

Thanks.

[richidoo]

I once had exact same assortment, from GIK. I found a great combination as follows:

Place the corner absorbers sideways on the ground, against the sidewalls, with one end of the trap even with the rear of the speaker, and other end extending in front of the speaker. This puts absorption as close to the woofers as possible and made the best result, ime.

Then pull the triangle corner absorbers away from the sidewall about 2 inches, and place a short side of a flat panel on top of the corner traps side edge. So it is sitting on top of the corner trap, tallwise.  Center the panel so it catches the reflection point of the tweeter. This will kill sidewall reflections.

The remaining 2 panels should be placed flat against the front wall (behind the gear, behind the speakers) at the reflection point of the tweeters. Raise the top edge of the panel a foot above the tweeters.

Use thick carpeting/pad on the floor to stop midrange floor bounce and slap echos from the ceiling.

Put speakers as wide as possible, right against the corner traps.
Optionally, use Master Set speaker positioning system before you install the acoustic dampers.

After I sold all the GIKs to a friend, I visited him a few months later and showed him the setup, he liked it better than the traditional setup he was using. His was a long narrows room like yours.

[richidoo]

SBIR is a big dip and a big peak caused by interfering waves from the direct speaker sound and the wall reflection. The frequency of the interference will vary with the distance between the speakers and the wall. 

[andycsb]

Question everyone...where would be the 1st reflecton point in the front wall (behind speakers) and back wall?

[JLM]

Without using basic geometry, the easiest way to find 1st reflection points is to sit in your listening spot and have a friend hold a mirror while moving along the walls of your room.  When you can see the speaker, you've found the 1st reflection points for that speaker.

[andycsb]

Hi everyone,

Have tried one panel behind each speaker. Now treating 2nd reflection points on each side wall (1st point panels are in place already). Not sure which configuration I like better in my room.

Have had my first panels (corner bass traps) not to long ago. To be honest...I did not notice an improvement in bass...bass still lacks punch...kinda loose. Overall sound as in clarity did imrove though.  Absorber panels are just about 1 week old. I am noticing a reduction in sound levels...esp after treating 1st and 2nd reflection points.  I have to turn the volume up a bit. Is that normal?

[richidoo]

Yes, it's normal to lose some efficiency when you add sound absorbers, because they convert acoustic energy to heat.

Look to the speakers for that bass clarity you are seeking. Mild acoustic damping won't do much for that. Very large corner trap absorption will make the lowest bass feel louder, which seems punchier, but still lacks overall bass clarity. Great bass is caused by good transient response and low group delay. Each of those virtues has many foils.

[andycsb]

Thanks for your input Richidoo and JLM.

[andycsb]

@JLM, Richidoo and everyone,

Have you tried QRD or skyline diffusors along the front wall (centre of behind speakers) in a small room such as mine? Your findings on that?

Thanks

[JLM]

Diffusors only work in a limited frequency range, determined by the depth of their cavities (based on size of sound waves which equals 13,000 inches divided by cycles per second).  So a 5,000 Hz sound wave would require a 2.6 inch deep cavities to diffuse, but 500 Hz would require a 26 inch deep slot (which is why they're only effective for mid-treble and higher frequencies).  Even then slot (linear) designs only work in the direction opposite the direction of the slot.  And to be effective diffusors must be made of sound reflective material (nothing thin or lightweight), so they can get very heavy.  Of course they'll only work for the wall/ceiling area they cover.

Your back wall wardrobe could act as a Helmholtz resonator (acting as a large diffusor for a limited frequency rang). 

Unfortunately your room dimensions are far from ideal (two dimensions nearly the same and the third 1.5 times the other dimensions), that reinforces echo at resonant frequencies (use 13,000 inches per second speed of sound to calculate those resonances). 

By the way, what issues are you trying to solve?

[andycsb]

Hi Everyone. @JLM...I am hoping to achieve...better and more precise imaging....smoother and a more balanced overall sound... larger soundstage and image size. Novice here...especially on acoustic treatment.

Anyone tried  polystyrene 2D skyline diffusors? Are they effective? Thinking of placing them at my front wall...either behind the speakers or in the center between the speakers. Or would some QRD 1D wooden diffusors be a better choice?

Thanks.

[jimtranr]

Andy, before you start throwing money at diffusors or whatever, could you post a diagram (hand-drawn or otherwise) of your room that shows the location of your speakers, equipment rack, seating placement, all other furniture, as well as (if applicable) windows, fireplace, and room openings--and the current placement of your panel and triangular traps? You might also indicate wall material (painted drywall? wood paneling?) and whether your ceiling is dead flat or sprayed-on "popcorn." If you have photographs, those would help, too.

Your descriptions have been good, but it might make it easier for others to make recommendations if we can get a more precise "look" at your listening environment.

[Hipper]

I would agree not to spend money on diffusors, yet. They need a certain distance to work properly so in a small room you are going to be restricted with their placement in any case.

If you have money to spend I would invest in more bass traps, the GIK tri-traps that you already have, or better, Soffit Traps. They absorb deeper than Tri-traps - see measurements on the GIK site. Place them with the Tri-traps in the front corners on top of each other. Generally you can't have too many bass traps.

I would also reconsider the idea of absorbing side wall reflections. Floyd Toole in his 'Sound Reproduction' book finds most listeners prefer side wall reflections as it enhances spaciousness. I agree!

The back wall may well be a better place to put some absorbing panels to catch first reflections. Use the other panels on the front wall. I recommend the wooden feet for these panels. This allows you to move them more easily, especially the ones in front of the wardrobe.

Another suggestion is to put your gear down one side if you can. This prevents reflections off that gear, allows more easily placement of panels and also gives you a better impression of the music being there instead of coming from your gear. The penalty is longer speaker cables. This idea comes from Jim Smith's 'Get Better Sound'.

Have you tried using the long wall for your speakers, or is that not practical?

In my humble view, getting the bass right is the biggest priority. When I finally did this (using precise speaker and ear positioning, room treatment, and careful use of an equaliser) it allows everything else to blossom. What you are aiming for is to hear the bass in the music, not from the room. Mind you it does depend on your speaker design to a degree.

GIK offer an advisory service for free and you can then follow their advice as your budget allows.

[optimationman]

Andycsb;  I am new at this acoustic stuff.  I will offer what I have learned.  If you are going to move the equipment rack, do so as soon as possible as it will in my experience change the sound stage.  Try covering the equipment with some fluffy stuff and see what will happen.  It is a long shot, but have you read about floor bounce.  Just another thought.

[jlawson1977]

@andycsb ;  I'm certainly no expert in this area, but I have a similar room ( a bit smaller), and very similar treatments from GIK.  After recently moving into this small room, the challenge began.  Bass was lacking, what was there was loose and undefined.  Lots of flutter and slap echo and a bland sound stage.   I have my speakers 32 1/2" from front wall to baffle and 24" from side wall to center of baffle, and they are about 7' apart.  My listening chair is about 8' back.  I tried lots of speaker and listening chair positions to get placement as right as I could, then started with the treatments.

Here's what worked very well for me: Moved my rack from between speakers;  Heavy draperies on front wall between speakers (also covering a window); Tri-traps in the front corners floor to ceiling; 1 244 Bass trap in front of each Tri-trap column, effectively creating a small super chunk trap; 1 Monster Bass trap in each rear corner, 2x2 absorber panels at 1st reflection point, and several 1x1 and 2x1 acoustic foam panels on rear wall and secondary reflection points.  The result  to my ears is excellent, especially in this very small space.  The bass is now deep, full and tight with little to no slap and flutter echo.  Imaging is quite accurate and my sound stage is quite large.  Even with this much treatment, the room is still quite neutral, neither bright or overly damped. 

I've ended up with about 85 sq.ft of bass trap and absorption covering the walls.  I can't remember where I found it, but I did come across a calculation on the web that indicated a room of my dimensions would need 80-90 sq.ft. of coverage to help control reflections and room nodes.  The site also included some diagrams showing treatment locations.  If I can did it up, I'll post the link.  With a little experimentation, you'll likely find what works best in your room.  Good Luck!

[ssglx]

Lots of talk about bass traps. What kind of speakers are these? Floorstanding? stand mounted? ported? sealed?

I have alot of diffusion, furniture and some 2D QRD, but no bass trapping and little absorption other than an oriental rug. I don't want to lose the microdynamics and I don't have bass issues, even with a suspended floor.

My bookshelves, and floor standers are rear ported and are pulled at least 4 feet out from the wall. That makes a HUGE difference on imaging, bass and midrange in my room.