Wednesday, January 20, 2010

SAT bass trap 2- diy bass trap

Update SAT bass trap

Somkeone ask me why you use 6 ply of carpet instead of 5,7 or 8 ply. Good question,actually it need a mass of 1.49kg/m2.
Here is the calculation:
The panel surface

1.74 x 0.29 = 0.5046 m2,
1.49 x 0.5046 = 0.75kg

I have weight 1 ply of carpet is around 145gram(less10% to minus the excess)=130.5 gram

So 750 gram/130.5 = 5.74 ply,
So round it up around 6 ply.

I have try out 3 ply carpet at first and it is not working.6 ply give me more satisfactory result. Sometimes we really need to do calculation to cut down the trial and error.
On the 1st version i can varying the depth of the bass absorber panel.
I found that the result is close what i have calculated out.


Thursday, January 14, 2010

SAT bass trap-diy bass trap

Simple as this (SAT)  baSS trap

Last year Koo come and visit me and taught me how nasty my room acoustic is. There is a lot of boom. Last week Koo inform me that he will be coming soon. So during this year I have employ 9 pieces of Helmholtz and 3 panel of bass absorber.The helmholtz will take care of the 120hz and below.

I only manage to finish the last piece of panel absorber last week. Before I make this last pieces of panel actually I have make another 2 pieces bass panel that can be adjustable. This is the simpler version.
The targeted frequency is 148hz.
The dimension of the panel is 174.38cm x 29.14cm x 11cm (internal)
1.49 kg/m2 panel mass.

This is the frame.I just use a few pieces of salvage wood.

After much consideration, i use carpet.The type of carpet we call in punch needle carpet.Rock wool is the best material but beware it may cause rashes.

I use 6 layer.I use staple .Now is 5 layer and later wrap the whole panel with another layer.If you worry the carpet is not strong enough you can put in wire mesh.But 6 layer of carpet might even put off a bullet.

This is the rear side.Just cover with a thin layer of plywood and done!

This is the 1st version oif panel absorber.This design is much more complicated with adjustable depth.
What is the result?

Before I employ any panel absorber, I can detect mid bass boom. At first I put 2 pieces, boom is disappear but there is mid coloration especially male voices. It is easily detectable when playing the Amos lee album.

When I added the 3rd panel the low mid coloration, high and dynamic is gone. So one must take care when we added something to our room it might disturb the whole acoustic sound balance of the room. We must be very careful when doing absorber for frequency more than 100hz. The range of the absorber range is too big and it might hinder the dynamic of a system
Koo, you can come now..


Monday, January 4, 2010

Jadis Pre

A Jadis jp80mc is having some problem and open up for health check. I took the opportunity to take some photo. The jadis jp80mc is separate into power supply and line.Show here is the power supply.This power supply is said universal to Jadis other pre amp like the JPS2.