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DIY Tri-corner and on-wall bass traps!

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Santy

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Joined
Aug 23, 2010
Messages
2,617
Points
113
Location
Bengaluru
Hi Folks

I had to relocate to Chennai last year. The room assigned for HT/ music sounded terrible with lot of flutter echo and ringing. So much so that I did not bother to setup my system properly, for over an year. The corner bass traps I made earlier worked pretty well in my previous home but were not adequate for this. Check this link to know how I made them. If you try it, remember to keep the face width of the trap 18 to 24 inches for best results.

The new room was another proof that no matter how good your system is, poor acoustics can screw everything. Acoustic treatment is probably the simplest and cheapest fix though not always the easiest, to improve the sound quality. Many of us continue to upgrade endlessly to improve the SQ (applying band-aids and more band-aids) without treating the core issue.

Though I have done before/ after measurements in the past, I am comfortable these days trusting my ears to see what good things room treatment can do. For the same reason I did not go too scientific finding the room modes, calculating the right size/ density of traps etc. I always believe that it is quite difficult to go wrong with acoustic treatment though you might overdo it. I must also admit that I am a novice in this field so take my work with a pinch of salt.

Like mosquitoes, bass loves corners. They like to hang around where walls meet. But worse are the areas where the walls and the ceiling meet. I always wanted to do a tri-corner bass trap but never really got the time. Now that I was forced to do it, I got going recently and completed four tri-corner bass traps as well as two side wall absorption panels.

I did not keep a track of the cost involved, but let me assure you, it is peanuts compared to the benefits. What is needed is your time, interest and little skills. If you have not done any treatment to your room (besides your carpet, ofcourse), let me assure you, this will be the best 'upgrade' you have done to your system, not just a ‘tweak’.

Materials used: Plywood 0.75 inch thick. Rockwool 50 mm, 120 kg/ cubic metre, fabric, fevicol, metal hooks, screws, nails, cable tie etc. You can use glasswool too if you can find, as some say it is safer. We are going to make all panels 100 mm or about 4 inches deep.

Tools used: Drilling machine, gun tacker, screw driver, saw, scissors, painting brush, duster, measuring tape, scale, marker pen, ladder...


Frames

Since there was this wood workshop next to the plywood store, I got it cut from there, saving lot time and labour.

hL5RE6A.jpg

H9MujDI.jpg

Making square frames was pretty straight forward, however, the triangular ones were a bit tricky. The angle at which the two pieces meet should be 60 degrees. Managed to explain to the carpenter and he did a fair job. The frames were secured with nails and fevicol.

96gG5rM.jpg


Gczj0SR.jpg

The rectangular frame should be of 4 ft x 2 ft, the size of the panels purchased. However to save wood, I had to keep the outer measurements 4x2 and thus I had to trim the rockwool panels to fit. If you are trying this DIY, you could keep the inner measurements 4x2. Same with the triangular traps, I had to chop the mineral wool to fit them. My original calculation of size for the triangular frame is given below. Going forward I will alternate between triangular and rectangular traps as they are built.

SEdIlYT.jpg


Fabric

We will be covering the panel with two layers of fabric to eliminate the slightest fear of hazard. The inner layer was done with used bed spreads. The cloth must not be stretchable at the same time porous enough to allow some air if you blow through it. Let the fabric be solid, light coloured unlike what I did.

For wrapping, you will need a gun tacker ( I used Miles TS-623 with 23/10H pins). You can do this without stapler (using Fevicol SR998) but the gun saves lot of time (and is fun to use ). Punch at 4-5 points on each side.

fhON8ML.jpg

While you do the second side, stretch a bit and while you do the last side, stretch as much as you can without tearing the fabric, ofcourse.

vUeovPH.jpg

dERqaAW.jpg

Now you can use the brush and apply fevicol to close the gaps. Once again stretch and press the fabric, few seconds after applying the glue.

fVWhhQv.jpg

Now do the same with the other three panels.

F8K0DVF.jpg

Meanwhile, I did the same process on the rectangular frames. Place the fabric on the panel, stretch, staple, glue and trim.

LEy80Ib.jpg

I used fishing wires along the width so that they can hold the rockwool tight in place. This seems optional.

AW5e0F7.jpg

B4kYuVv.jpg

MsSIR7k.jpg

Do not wrap the other side yet :)

Stuffing

In the box, there were 6 panels of 4ft x 6ft x 50mm each

eyxtYHM.jpg

Going forward, you will need gloves to protect your hands. Also wear full sleeves shirt, jeans, socks as well as eye gear. Though not as bad as glasswool, these can be itchy as well.

As mentioned earlier, I had to trim the rockwool panel to fit the frame. Two panels in each frame. Use duster to remove the debris formed while cutting / handling.

70a15a3.jpg

ETRJ3Zw.jpg

Repeat for the other panel

TDdcRwN.jpg

Now lets go back to the triangles. Cut the slab as per the sketch.

k8GkfZw.jpg

The side chunk is a waste :( So you get one equilateral triangle and two right triangles (x 2 for each slab of rockwool)

HlNoYUO.jpg

Place them inside the frame as illustrated:

QA49dgM.jpg

CXNw8Ni.jpg

Now repeat for the other panels. There you go, all the panels are ready. The side panels are pretty heavy now!

gsREZBW.jpg

Repeat the wrapping process for the uncovered side, with your base fabric. Ouch, that's gonna take lot of time!

bOPd0gr.jpg

Second layer wrapping

If you want to keep it simple, you can use only one layer of fabric. If so, wrap it such that front side looks clear off pasting job. I picked up a plain, light color for the ceiling traps and an abstract printed fabric for the side ones.

61KUvIL.jpg

Now the corner wrapping can be a bit tricky. Difficult to explain so let the pictures do the talking.

kwmgvrq.jpg

70LdJVH.jpg

k1C6J68.jpg

Don't forget the stretching. You don't want wrinkles on them!

zAxjbQZ.jpg

One panel done

ymIObGd.jpg

All four done. Pat yourselves if you reached this far.

FCOU7hE.jpg








Contd.....
 
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Santy

Well-Known Member
Joined
Aug 23, 2010
Messages
2,617
Points
113
Location
Bengaluru
For mounting, I got these photo frame hooks..

jEGYzqc.jpg

and screwed them onto the frame

qZ6Cvzx.jpg

O4XTGKo.jpg

HjSeukk.jpg

I later realised only two hooks were enough. You can also use these 'C' hooks, will do the job.

5NNREhy.jpg

Now for the wrapping of the side traps. You can choose something with a nice design of your choice (talking about WAF). Follow same process. Stretch, staple, paste, trim.

D423Tal.jpg

klHTwZM.jpg

The corner folding has to be done properly to give it good finish. Follow steps exactly as shown in WIP pics:

5Bcxbd0.jpg

PtfkN4E.jpg

XabFNnO.jpg

Apply glue and crease it

NDujuLI.jpg

Was happy with the finish

DDEnwuY.jpg

Finally this is done

k9eVlN6.jpg

DgoS2jY.jpg

That's it...!!

uSarbSt.jpg

Time to grab a beer!

Mounting

Honestly, this is quite tricky as far as the ceiling thing goes. I have no idea if there is any better / easier way to do it. I took help from a youtube video and I will try to explain.

Use some nylon string to tie the hooks as indicated and use a long cable tie to make a loop at the centre ( do not tighten it)

nHdvaZo.jpg

Z7THDI1.jpg

J8jK272.jpg

The total height of the loop from the panel should be about 15 cm. Now attach a twister tie or another string to the cable tie at its tail end (fold the tail). This has to be quite strong.

ezT0QWw.jpg

Fix a C hook at about 2 inches down the ceiling

LYNrHzh.jpg

q1l5q9y.jpg

Now hang the panel on the hook by the cable tie.

qGdA7N1.jpg


Now slowly pull the long string as you support the panel. The cable tie will drag the panel up towards the ceiling.


46164859172_6c08dacc30_o_d.jpg

Can do some adjustment of string lengths to make it a snug fit but I liked how it looked hovering in the air. It also creates more room behind the panel, increasing the absorption. Complete the other panels.

46164856712_161106445b_o_d.jpg

The side panels can be mounted using some L frame or some strong hooks. I am yet to do it. For now, I just placed them on the floor at the first reflection points.

Along with some foam panels at second reflection points, the "room is sounding" much better. No ringing. No echo. No hanging. No bouncing. Just better sound quality in almost every aspect, you can (or rather cannot) achieve from an expensive upgrade. Will try to post the measurements, if I get time.

Thanks for reading. You have a lot of patience!!
 
Last edited:

srinisundar

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Joined
Sep 29, 2009
Messages
3,348
Points
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Location
chennai
Very nicely briefed and well written and hope nobody should raise doubts.. Having visited your place and heard your system wall traps/ bass traps were helping a lot to get a good sound even-though you have a large glass window behind the system.
 

Alfahath

Active Member
Joined
Sep 7, 2018
Messages
162
Points
28
Location
Chennai
For mounting, I got these photo frame hooks..

jEGYzqc.jpg

and screwed them onto the frame

qZ6Cvzx.jpg

O4XTGKo.jpg

HjSeukk.jpg

I later realised only two hooks were enough. You can also use these 'C' hooks, will do the job.

5NNREhy.jpg

Now for the wrapping of the side traps. You can choose something with a nice design of your choice (talking about WAF). Follow same process. Stretch, staple, paste, trim.

D423Tal.jpg

klHTwZM.jpg

The corner folding has to be done properly to give it good finish. Follow steps exactly as shown in WIP pics:

5Bcxbd0.jpg

PtfkN4E.jpg

XabFNnO.jpg

Apply glue and crease it

NDujuLI.jpg

Was happy with the finish

DDEnwuY.jpg

Finally this is done

k9eVlN6.jpg

DgoS2jY.jpg

That's it...!!

uSarbSt.jpg

Time to grab a beer!

Mounting

Honestly, this is quite tricky as far as the ceiling thing goes. I have no idea if there is any better / easier way to do it. I took help from a youtube video and I will try to explain.

Use some nylon string to tie the hooks as indicated and use a long cable tie to make a loop at the centre ( do not tighten it)

nHdvaZo.jpg

Z7THDI1.jpg

J8jK272.jpg

The total height of the loop from the panel should be about 15 cm. Now attach a twister tie or another string to the cable tie at its tail end (fold the tail). This has to be quite strong.

ezT0QWw.jpg

Fix a C hook at about 2 inches down the ceiling

LYNrHzh.jpg

q1l5q9y.jpg

Now hang the panel on the hook by the cable tie.

qGdA7N1.jpg


Now slowly pull the long string as you support the panel. The cable tie will drag the panel up towards the ceiling.


46164859172_6c08dacc30_o_d.jpg

Can do some adjustment of string lengths to make it a snug fit but I liked how it looked hovering in the air. It also creates more room behind the panel, increasing the absorption. Complete the other panels.

46164856712_161106445b_o_d.jpg

The side panels can be mounted using some L frame or some strong hooks. I am yet to do it. For now, I just placed them on the floor at the first reflection points.

Along with some foam panels at second reflection points, the "room is sounding" much better. No ringing. No echo. No hanging. No bouncing. Just better sound quality in almost every aspect, you can (or rather cannot) achieve from an expensive upgrade. Will try to post the measurements, if I get time.

Thanks for reading. You have a lot of patience!!
Wow! Great effort , good results. Thanks you for sharing it :)
 

MaSh

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Wow that's fantastic. Looking absolutely amazing. Do you have before and after measurements of any kind?

MaSh
 

Santy

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Messages
2,617
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Location
Bengaluru
Thanks everyone, I did not take 'before' measurements but will do 'after' readings some day and post here.
 

captrajesh

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Nicely documented Santy. Only, a few pictures are not showing up. Could you kindly create an online album and shate with us!?
 

smedhavi

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Feb 6, 2007
Messages
768
Points
63
Location
Bangalore
Nice and neat work!
By the way, glass wool is itchy on skin, but rock wool is carcinogenic. I think once it is covered with cloth there is no risk. Just that we need to protect ourselves while working with it. It has excellent sound absorption properties.

Your good looking cat does not seem to be too interested in checking out your new toys :)

Regards,
Sharad Medhavi
 

renjith lal

Active Member
Joined
Nov 23, 2011
Messages
567
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Location
Detroit
Santy I really liked your triangular trap for the corner. I was looking for an option at my place and was wondering how to hold the triangular trap at the corner.

Thanks.
 

Santy

Well-Known Member
Joined
Aug 23, 2010
Messages
2,617
Points
113
Location
Bengaluru
Nicely documented Santy. Only, a few pictures are not showing up. Could you kindly create an online album and shate with us!?

Hi Capt. Thanks. Can you try this link:

Thanks
Nice and neat work!
By the way, glass wool is itchy on skin, but rock wool is carcinogenic. I think once it is covered with cloth there is no risk. Just that we need to protect ourselves while working with it. It has excellent sound absorption properties.

There seems to be many studies concluding rockwool is non-carcinogenic. Also studies which proved otherwise involved large doses I believe. Anyways it is better to use two layers of cloth as I did and advised.

Santy I really liked your triangular trap for the corner. I was looking for an option at my place and was wondering how to hold the triangular trap at the corner.

Thanks.
Thanks. I think I had explained the process of hanging it from the ceiling. Please do check the pictures.
 

elangoas

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Nov 4, 2009
Messages
7,536
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Location
Madrasapattinam
Any other foam based options we can use instead of rockwool.

Acoustic foam seem to have lesser NRC (Noise Reduction Co-efficient) w.r.t low freq.. So my guess is it won't be a substitute for rockwool, which have higher NRC in the low freq range..

Here is info from the net : (just an example)
Noise_Reduction_Coefficient_NRC_Ratings_-_Acoustic_Foam_2_1024x1024.jpg
 
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