Home-made Acoustic Panels!

[Santy]

I got a limited quantity of Glasswool from some source and decided to put it for good use. And I am glad I tried it. The difference it has made is quite amazing. I now doubt if people who endlessly upgrade their audio system without focusing on acoustic correction of their room, are going in the right path. Creating an acoustic panel is darn simple if you have time for it ( moderately difficult though).

I used mirror technique and tried the panels on side walls at first reflection points. The sound has become more crisp and accurate now. There is no smearing of high frequencies. The bass slightly became tighter and whatever harshness existed in highs have completely gone. Snare drums are so punchy now. The sound is more focussed and there is more space between instruments now. You can clearly observe that the sound is less bouncing and fast decaying once the panels are in place. :yahoo: All these at a fraction of the cost of upgrading!

Stuff used:
8 panels of Fibreglass wool 4' x 2' each 0.5" thick
Wooden frames of 1" thickness, 2" deep. Total length 24 feet
A cheap and better quality fabric
Stainless steel 'L' angles 16 nos
0.75" and 0.5" screws
'Fevibond' Resin Adhesive
Tools: Screw driver & Hammer (or Drilling machine if you have), Scissors, Arc Saw, Surgical gloves, Measuring tape, Marking pen.


Stage 1:
First, the wood is first cut into pieces; 4 nos of 2' length + 4 nos of 4' length using a saw. You can get it cut from the plywood store where you bought it, if possible.

Arrange the pieces in a perfect rectangular frame as shown, with thinner side facing up. Then place the L angles on the corners, mark the holes with a pen and punch pilot holes using a long nail. Then screw the angles in their place. Repeat for other corners. Now invert the frame and repeat the task. You can use shorter screws this side to make it easier for you.

Stage 2:
Wear the gloves now, place the fibrewool on the floor/ table and spread the cheap fabric on it, better side facing up.

Now place the frame over it such that it slides on the fibre pad and touches the floor.

Now apply adhesive to the bottom half of the wood, throughout the frame on one side. Put adhesive as a sine wave for better results.

Now flapover the fabric and ensure it is stuck to the glue/wood.

Repeat this on the adjacent side of the frame. Now while pasting the fabric on the third and fourth sides, you have to stretch it as far as possible, without tearing it and then stick it (you may have to hold it for a minute till it dries). Do it for small lengths of 1 feet or so. Once done, you can cut the excess fabric (close to the glued area)

Stage 3
I used a slightly used bed spread for the fabric for the facing side. I bought a new one actually with a better design on it. My wife was furious when she knew it was to be cut. hyeah: Later I found it to be not so porous so avoided it. If you blow through the fabric, it should give some resistance but not completely block the air. Also it should not be stretchable.

Now spread the good fabric on the floor/ table, with better side facing down.

Place the panel on top of it, so that the naked side of it is touching the new fabric. The fiber pad may fall off, so be careful.

Ideally, before starting you could make a sandwitch of good fabric, fibreglass wool and then cheap fabric. But it was sounded complex so I did not advise earlier.

Pull out the fabric on all sides so that there are no wrinkles under the panel.

Apply adhesive on top half of the frame side (any) and then on top of the frame.

Paste the fabric on it. Repeat it for the adjacent smaller side.

Now when you do it for third and fourth side, you have to stretch it real hard (without tearing the fabric ofcourse). If its a printed material with some line design like I used, it becomes more difficult since the lines would become waves if it is not evenly stretched. Remember that the fabric is the only thing holding the stuff inside so it should be really tight. Paste it 1 feet at a time so that you can hold it tight till it dries.

Now you can again cut excess fabric, apply some adhesive and stick the new fabric over the previous one.

Once everything is done, you can apply some adhesive on such areas where fabric meets screws or metal- to ensure it does not tear over a period of time.

There you go. The first panel is ready

Repeat it for the other panel (s). It took me another Sunday to complete the other one. They do look sexy, don't they?

You can fix rubber bush or something on back of it to give space between panel and wall or mount it in such a way that some breathing space is seen.

I will post a pic with the panels in their place shortly. My next assignment is to make corner bass traps. Will share W-I-P once ready.

 

[captrajesh]

Thanks for sharing the build pics. Looks very promising indeed.

Looking forward to a review on it's performance.

 

[Record Player]

This is fantastic Santy and thanks for sharing such detailed steps and photos. Awaiting your review on this.

 

[rajadeep]

Santy nice job!!! Looks like have to stop by ur place once more after u fit the panels... I am in the planning process of renovating my house & stuff like this I could really implement in my acoustically crappy hall ...

 

[omishra]

Great Santy! I was planing this one for complete wall but stopped back. Now I will rethink.
Thank you. Please post some observations on pre and post differences. Also what specific location you planned? I am planing back and front wall of speakers as sides are occupied by furniture and window panes.

 

[gramaphone]

I made few of these myself. Also made corner bass traps by sticking 3 high density panels together and cut them to triangle. Bass traps made my sub-woofer sing.
I suggest low density panel for the wall treatment.
Good Job Santy
Gramaphone

 

[spirovious]

Nice job santy,will love to know the improvement in sound quality.

 

[AVM]

Neat job. Thanks for the step by step pictorial representation. Would love to hear on the improvement in SQ.

 

[ranjeetrain]

Good job! Nice and simple. The best thing is extremely detailed instructions to even help noobs such as me :lol:

 

[Santy]

They may appear still; but they are sucking quite some waves and faithfully dispersing them within itself.

I have a problem with the left side panel since it has to be placed right over the bathroom door. hyeah: I am planning to fix it on a slider so that it can be pulled into the position while listening or pushed away when the system is off.

I am yet to properly mount them (i.e to leave space from the wall). For testing the performance, these were placed on chairs on either sides exactly at the first reflection spots.

The improvement in SQ is very much apparent. It created a difference which I believe might be possible only with such kind of system upgrades which I cannot afford now . Infact it gave me a gut feeling that no system upgrade can compensate for the room deficiencies which often screws up the sound royally. I remember how the PMC dealer at the Mumbai meet struggled to stop unwanted waves reaching the sweet spot.

The sound is more focussed now and I could visualize the space between instruments. There is no more smearing of upper mid and high frequencies which brings out the vocals completely separated, especially female vocals. Locating the instruments is much easier now. There is no overhang of drums or guitar notes. They quickly and crisply fade away when the notes end. The snare drum sound in the percussion track of the CD given by Amp_Nut was so fast and enjoyable. I realize that the sound is coming from front and no more emanating from the sides.

There is not much difference in the bass frequencies though (<150 hz) with the panels. So I am quite restless now to make corner bass traps. And also few more panels if possible for the rear and ceiling. For a home setup, its a challenge but I am sure it can give a satisfactory environment in which even budget systems would shine. I strongly recommend treating the room to all people here wondering where the sound is getting messed up. I also suggest to make atleast 3" deep panels (rockwool or glasswool) for best results.

 

[manoj.p]

Santy,

Great job.

Can you also try putting the treatments where reflections from opposite speakers are supposed to come? Put absorber for left speaker on right wall, and for right speaker on left wall. That could help with imaging too.

Try both and let us know.

 

[Santy]

Also what specific location you planned? I am planing back and front wall of speakers as sides are occupied by furniture and window panes.

Om, I think panels placed on the rear (behind speakers) are usually meant to help in the bass department provided it is fairly thick and dense (corner traps). They are not the primary reflection areas.

The first reflection points are more important for preventing unwanted room amplification and mixup of mids and highs. They are at the sides, ceiling, floor and rear wall.

First priority should be the carpet. Second should be the side panels. The ones closest to speaker are absorbing waves from respective speakers and the ones farther are targeted at the opposite speakers. Fourth priority is ceiling (not seen below), fifth should be rear panel (behind listener). Bass traps can be planned anytime as per preference.

Can you also try putting the treatments where reflections from opposite speakers are supposed to come? Put absorber for left speaker on right wall, and for right speaker on left wall. That could help with imaging too.

Yes manoj, that's the ideal way to go but the left wall in my room is not really suitable for this second level of treatment.As per calculation, the panel would be covering half of the door to the entrance of the room. Let me see. :sad:

 

[Staxxx]

Nice job with the panels !! I use the config as above too, but additionally I find a set of diffusors (not absorbers as discussed above) between the speakers on the wall helps in my case.

 

[prem]

Hi Santy

Great job. Looks really nice. Now go for the bass traps. If yours is a rectangular room, you will ideally need 4 bass traps, one at each corner of the room. If you are planning only two, then place them on the wall behind the speakers at the corners. Also you can look at four small triangular pillows at the four top corners of the room to open up the highs.

The panel that you have made for the side walls, you can place a similar one exactly in the centre behind the speakers. Imaging and timing will improve.

 

[himadri]

There is not much difference in the bass frequencies though (<150 hz) with the panels. So I am quite restless now to make corner bass traps.

Congrats Santy
I made 2 chunk traps http://www.hifivision.com/av-enhancers-room-acoustics/21275-diy-bass-traps-smallish-rooms.html
cheers

 

[manoj.p]

Yes manoj, that's the ideal way to go but the left wall in my room is not really suitable for this second level of treatment.As per calculation, the panel would be covering half of the door to the entrance of the room. Let me see. :sad:

Santy,

The opposite speaker reflection is the worst, as it narrows soundstage, muddies up the imaging. Same side speaker reflection can be helpful at times because it widens up the soundstage and gives the feeling of sound coming beyond walls.

If you become creative, then you can put a panel on the entrance door itself. These panels are not that heavy and will not make door too heavy. I would say give it a shot. If there is lots of improvement, then you know what to do next.

Also, one thing you stated absolutely correct. Room treatment improves sound in a room and makes the biggest impact, next to speakers. To think people worry about DAC, power cords, cables and what not to get that result but omit the most important part. One of my friend told me this. Someone asked him, about two processors - one costing $2000 and another $4000. The debate went into how much improvement will $4000 processor bring? His answer was - "I would buy that $2000 receiver and spend rest on room treatments. That will give way better improvement than buying that $4000 processor." hyeah:

 

[himadri]

"I would buy that $2000 receiver and spend rest on room treatments. That will give way better improvement than buying that $4000 processor." hyeah:

Well well. Im sure the AV distributors/dealers would not like this little secret revealed.DIY room treatment gives the maximum befit with minimum money.Your next upgrade can easily get postponed by a few years. However this requires maximum efforts.
Cheers

 

[hydra]

Great going, santy! Thanks for the detailed post with photos. I've been meaning to build a pair with glass wool myself, but I've been procrastinating for no reason at all. Your post should give me the kick in the butt I need, to get started on them.

A few months back, I'd built a pair of panels with plywood panels and eggshell closed cell foam I bought from Bajaao.com, and they made a world of difference. I use them at the first reflection points for diffusion. I lean the panels against the wall. I haven't fixed them to the wall. Mostly because I didn't want to nail anything onto the wall, and also because I'm a compulsive tweaker as far as speaker placement is concerned, and so fixing the panels would render them not so useful when the positions change.

I agree completely with you about getting most out the room before spending any money on upgrades. The bang for the buck quotient is really high in room correction and placement tweaks. Most of the time, the expense involved is 0.00.

 

[gramaphone]

Hello Santy,

I can see your polk LSI 9 standing proudly tr. I have them too and like them. Recently i was re positioning the speakers and observed the sweet spot was some where here as shown in the image . Can you please confirm if you hear any improvement sitting at the marked spot or even forward. Just want to confirm is it the speakers or my room playing the trick.

Thank you
Gramaphone

 

[Santy]

@gramaphone
I also somehow feel the sweet spot is closer to the speakers even after toeing in at roughly 30.

One thing I observed is eventhough these are sensitive to positioning but its so only for horizontal axis. Vertical off axis performance is quite good. At the centre spot, whether I stand or sit or lie down, there is no major shift in the sound.

Let me get closer to the speakers and let you know the difference if any, by tomorrow.

@hydra
Go ahead and start sourcing the materials buddy. You will definitely like what you created.