Help chosing the right basstrap design

2377 Views 10 Replies 3 Participants Last post by Bluum, Apr 21, 2008

Discussion Starter · Apr 17, 2008

Hi, I have a little problem with the bass in my listening room.
I'll try to be short and effective.

Problem: Uneven midbass and bass without "punch".
Wish to get: A clearer midbass, a little more punchy bass and a more even frequency response.

Current accoustic treatment: 6 pieces of 5cm thick Rockwool Acoustic plates
Acoustic treatment planned to attain: Thick floor-carpet, bass traps for the three corners, thick curtain to separate the two room part from each other.

Stereo: B&W DM602 S3, NAD C320BEE, SVS SB12+

The room (roomheight = 2,2m):

As you can see, the part of the room where I'm sitting, is allmost square. That results in a huge peak around 46Hz, which sometimes is about 20dB higher than the target. This is evened out by using the PEQ function on mye SVS SB12+.
The speakers are fading out at about 80Hz (run through the lowlevel, highpass filter in the sub).

Here are two graps and two waterfalls. One with, and one without PEQ activated.

Now, lets talk sollutions.
Criterias: Cheap, not to physically big construction
DIY is very much an option, and there are several designs.
The simplest one is probably the "superchunk" design. And with that design, I can use absorbers that are 60x60 cm, and that are 110cm high. These are to be placed behind each speaker, in the corner.
I can't use anything larger, because that simply won't fit.

In the remaining corner, I planned to use two 1,1 meter high ones which are about 42,5x42,5cm.
I don't think I want to build or by a Helmholtz resonant just yet.

Does anybody have a basstrap/absorbentdesign that thy would reccomend me in my room?
Any advice at all would be nice, but more spesific ones are preffered

EDIT: just ask for more info if you feel something is missing

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bpape

· #2 · Apr 18, 2008

Good plan so far. Solid superchunks as high as you can get them in the front corners - floor to ceiling is best.

Treat the corner to the right of the seating the same way.

Move the seat away from the wall that's close behind the seating - this is a major part of the problem. Kill that wall with 2-3" if you can't move it - just be realistic.

The curtain will do nothing other than completely kill the high end and surround field.

Bryan

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Discussion Starter · #3 · Apr 18, 2008

Because of the window on the right side, I am unable to use a floor to ceiling superchunk there, and therefor I dont think I want to have it on the other side either. I have a feeling that the may cause insymmetry, but I might be wrong about that?
In the corner next to me I was hoping on using a smaler superchunk, but instead to use it from floor to ceiling.

What kind of material should I use?
Some kind of Rockwool I gues, but what kind? (I feel weight is an important factor)
I can put some LECA blocks or other solid blocks in the corner if that helps ...

How big should they be these superchuncks?
I planned to use 60x60cm behind the speaker, and 42,5x42,5cm in the last corner, because 60x60cm might be a little big there. (But I'll use 60x60cm if 42,5x42,5cm is way to small)

The purpose of the curtain is to reduce echo from the space behind me, and I expect og demand nothing more

Kill that wall with 2-3" if you can't move it - just be realistic.

What do you mean by that?

I actually just moved my couch about 20cm back (my head is now about 30cm in front of the wall, just not right in front of it), because that resulted in a little more even and higher output around 50-80Hz.

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JohnM

· #4 · Apr 21, 2008

Off topic, but the soundcard cal trace on your measurement indicates there was some sort of loopback/monitoring feedback active when you measured it. It is distorting all your measurements correspondingly, you need to resolve that and get to a flat cal curve, some roll off or ripple at the very highest and lowest frequencies is OK but not what you currently have.

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bpape

· #5 · Apr 21, 2008

What I meant was to use something 2-3" thick on the wall behind your head. If you moved back closer and you're getting better measurements, then likely, it's something coming from the rear area of the room and is not an axial mode.

As for the front, yes, you want to keep symmetry. Do as much as you can and still keep it the same on both sides.

Bryan

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omholt

· #6 · Apr 21, 2008

Have you tried to place the speakers up against the right corner? (in Norwegian to explain where: altså diagonalt mot hjørne til høyre for der anlegget står nå. En på hver side av hjørne) That's something I would try. You'll get the coach a little further away from the wall and you will probably kill standing waves more effectively. It means that one speaker (the right one) will have the window as a first reflection point, but you can always place rockwool panels there when you listen to music.

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Discussion Starter · #7 · Apr 21, 2008

Does the wall affect the sound that much when I don't sit right in front of it?

I don't know what is up with the soundcard, but it is a Creative XtremeMusic soundcard. I think it might be some leakage between the in and output jack. No kind of loopback has been turned on by me, and I have turned off all equalization and similar effects.

When it comes to placing the TV and stereo diagonally in the corner where the right speaker stands now, I have tried it before with wariable success. Besides, it is not very practical in mye eyes. (Theres no room for my computer if I arrange the furniture that way).

The window is about 20cm higher than the speaker, so I dont get any trouble from it.

I like it the way it is now, and I think this placement has potential. I've allmost made up my mind; and I think I'll go for superchunks in the three corners. 60x60cm (24x24"), which means a ~85cm diagonal (33/34"). That oughta do something for the sound.

But I'm insecure about what porous material to use. I've been looking at some Rockwool B-plates, and something we have in Norway called GLAVA Plate 40. Both with "40" as "sounddampingfactor".
Would one of those be suited for a superchunk bass absorbent?

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bpape

· #8 · Apr 21, 2008

You'll still get reflection and bass buildup off that wall that you're very close to - even if it's not right behind you.

Bryan

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Discussion Starter · #9 · Apr 21, 2008

I know about the bass buildup part, but is it that much reflections?
Wouldn't it be enough with a superchunk in the corner and the little CD-rack as a diffusor?

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bpape

· #10 · Apr 21, 2008

Bass buildup is caused by reflections. Corners just happen to be a good place to hit the end of more than one dimension at a time. That flat will will still cause issues. The CD rack will do nothing as a diffusor and bass waves will go right around it like it's not even there.

Bryan

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Discussion Starter · #11 · Apr 21, 2008

Yes, I know the CD-rack won't do anything about the bass, but I was thinking about midrange and treble when I mentioned it

But do you think it is necessary to use 2-3" damping there?

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