Bass Traps

[Pitchucold]

Hi Team,

I plan to setup Corner Bass traps for my room which is my HT room and Bedroom.

Front Speaker : Monitor Audio RX 1
Center : Monitor Audio RX Center
Surrounds : JBL Control 1
Sub : Velodyne VX 10.

I am planning to take DIY Route for Corner bass traps. I checked couple of sites and also Purna and Vinay threads.

My Room Size is 19 X 10 Ft ..with ceiling hieght of 10 ft. I am planning to use Glass wool for insulation.

Couple of questions :
1. Can i corner triangular basstraps + Corner basstraps for the entire height.
2. Saw the post by Alok Lala that Glasswool needs to be wrapped in tissue to be safe. Dont get it completely.
3. How much does slab of glasswool costs. Saw National Industrial company offering it in Chennai.

I have attaced photos of my room along.

Any suggestions / help is appreciated.

regards,
Prasanna KV

 

[sdurani]

Don't see any attached photos. Is your main listening position on the 10' wall or 19' wall?

Bass traps have to be very thick (several feet) in order to be effective at low frequencies, but you can address some of your bass problems via placement of speakers and subwoofer.

To be a true bass trap, you need to put some sort of facing (paper or thin wood or plastic) on the front of the trap. This makes sure that mid and high frequencies are reflected and only bass is absorbed. Without this facing you have a broadband absorber, which absorbs at all frequencies, not just the bass.

 

[magma]

the above was achieved by the following in one of our installations

We used a combination of anutone, 3mm MDF and finally grill cloth

But sanjay i have a doubt here
For the bass traps behing the speakers we find normal anutone backing and porous POP work works well too
we havent experienced any ill effects of the Mids and higher frqunceies getting absorbed "behind" the speaker

 

[himadri]

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

 

[Staxxx]

the above was achieved by the following in one of our installations

We used a combination of anutone, 3mm MDF and finally grill cloth

But sanjay i have a doubt here
For the bass traps behing the speakers we find normal anutone backing and porous POP work works well too
we havent experienced any ill effects of the Mids and higher frqunceies getting absorbed "behind" the speaker

I am very surprised that what you mention has worked at all, unless I am misunderstanding your description. Most of the corner bass traps I have seen have all been very chunky and large (mine were 60 cms in depth and width which was the minimum) and need to be very carefully designed and put together so that they are "tuned" to absorb frequencies at a certain level. I think truly effective bass traps are the hardest of room treatments to DIY and get right in a room. Sanjay's comments are good.

There is some good information available on the Jocavi website and other specialists in acoustic treatment panels.

 

[Pitchucold]

Sorry for the delay Guys..Plumbing Line broke at home.. was working with plumber all day to get it fixed.

Thanks Sanjay.

I have added the missed photos.
You have already answered my other question on tissue paper recommendation. I read in another post as well on using plastic cover. I am planning to use PLastic Cover or chart Paper for it. I presume it will work and also hold the glass wool

Thanks Himadri. I have read your post couple of times along with Purna's and Vinay's. I am going to settle like the one you have built. I am going to put it on top AV Rack/Table to the
ceiling on Left Side of Speakers (Facing them) Totale 7 Ft ..3 Ft from ground to rrof) and On the right i am debating on having it in two split parts of 3 ft then existing Bookshelp + another 3 feet to the top or relocate the bookshelf / DVD Rack and have entire 7 ft like left side for uniformity. Your Bass traps looks awesome. Mine being in the bedroom, i think if i can get it done like yours would avoid being an eye sore.

I am also planning to build a Right REar Corner Trap as well. Entire Back side of the room is covered with Wardrope made of wood. Should i exclusively go for rear bass trap as well?

I am guess I would just check it out with Front Bass traps, if needed go for rear as well.

 

[Staxxx]

I think you are going to have great difficulty dialling the sub into that room if you have a problem with booming currently with all the woodwork around. I am not sure a makeshift corner treatment will make much of a difference. And you will definitely need sizable corner traps to tame the Velodyne, if you can at all. The small RX1 speakers do not produce enough low level output to excite the room, I don't think. Have you tried using some spacers (cones) under the sub and speakers instead perhaps? Just a thought before you go through so much trouble.

 

[LIZARDKING]

Hi! I am facing a problem like Pdhanwada. I have a door too in the rear corner, my whole room is treated with 3" of foam, plywood on the panelling and fabric all around. the floor is 4" thick and carpeted. the ceiling has a false ceiling and is stuffed with 3" of foam in the wooden paneling. My room size is 16' by 16'. Its a dedicated room with 4 recliners in a line. The equipment i use is there to read and as you can see I am using a Velodyne dd15+. Earlier I was using my Velodyne spl12 along with the dd15 but not anymore. I still dont find much of a difference by excluding it. I get too much of booming in all corners reaching the corner seats. what can I do with my bass traps? I can have them in three corners but not in the fourth for i have a door there.
Thanks!

 

[magma]

I am very surprised that what you mention has worked at all,

huh ?
the anotone is 1 foot thick ?
why will it not work
please explain ?

 

[Staxxx]

I am sorry I misunderstood the panel from your post. Am I understanding correctly that you stacked panels vertically that were one foot in dimension and then sliced through them diagonally to make the corner traps?
So what frequencies were your bass traps made to be most effective at (or were they across the board?) and how did you determine the requirement please? I am very interested in a similar set up too. Did you get a good frequency response and impulse response curve after installation please to check the efficacy of the installation? Please post. Thanks.

 

[magma]

that is correct

we used this
Anutone - Drywalls . Ceilings . Panelling . Acoustics
board (used several actually ) and sliced it diagonally (for two corners) - 1 foot being the deepest when measured fron flat face to the corner

then we added a3mm mdf frame and covered it with this

Aurica Soundproofing - Wedge Shaped Acoustic Foams, Mopads, Acoustical Foam Panels and Acoustic Foam Panels Distributor & Manufacturer from Mumbai, India


we planned on it to absorb ALL frequencies


i will dig up the freqiuencey response chart too

 

[sdurani]

But sanjay i have a doubt here
For the bass traps behing the speakers we find normal anutone backing and porous POP work works well too
we havent experienced any ill effects of the Mids and higher frqunceies getting absorbed "behind" the speaker

With normal monopole speakers, placing broadband absorption behind the speakers shouldn't result in ill effects, since mid-high frequencies are directional (pointing away from the absorption).

But, if you are placing the bass traps away from the speakers (like front or back corners), then you have to ask yourself whether you want a bass trap (limited to absorbing only the bass, which requires some sort of facing) or a broadband absorber (unfaced to absorb all frequencies).

There is no right or wrong choice, just the one that fits your needs.

 

[sdurani]

You have already answered my other question on tissue paper recommendation. I read in another post as well on using plastic cover. I am planning to use PLastic Cover or chart Paper for it. I presume it will work and also hold the glass wool

Should work. Don't know how low in frequency it will be effective, but it should absorb something.

If you blow across an empty Coke bottle, you can get that small chamber to resonate (make that foooooh sound). If you enlarge that chamber to the size of your room, it will still resonate (produce large peaks & dips at certain frequencies).

For your 10' width, the first 5 of those resonant frequencies will be 57Hz, 113Hz, 170Hz, 226Hz, 283Hz. You can cancel the first one by placing your subwoofer at the midpoint of room width. By comparison, the bass trap needed to absorb a peak in the 50Hz range would have to be a couple feet thick. More practical to do it with subwoofer placement.

The other 4 width modes are above the crossover point, so you can't use subwoofer placement to fix them. However, placing your L/R speakers 20 inches in from your side walls (assuming centre speaker is exactly in the middle) will cancel the remaining 4 resonances. This should get you much smoother frequency response across your entire seating area.

 

[Pitchucold]

Hi Staxx, Sanjay,

Thanks for response. I shall hold bass traps plan for a while and play with positioning of speakers.

Staxxx, How can i fit the cones to bookshelfs ? I thought those are predominatly for Floor standers ? I actually have bookshelves on wooden boxes (with sandfill) with granite top and woofer on a think mat.

Magma, Seek your recommendations for Spaces / cones for Monitor Audio Rx1s ? Do we also need Spacers / cones for RX Center ?

Sanjay,

I am planning to try these two options then

Option 1 :

LEt me try positioning sub at 5 feet from sides and reposition speakers like 20 inches from sides . Problem here would be sub and center channel would be on the same line, like one on top of another with height difference of 2.5 feet.
I was in the assumption that corner location for Sub are the best.

Option 2 :
I am planning to eliminate VX 10 out of equation and check driving front speakers with full range and see how movies sound. I dont have issues with music as i play them only in Pure audio on AVR. which is only stereo with other unwanted circuits/processing turned off

thanks and regards,
Prasanna KV

 

[Staxxx]

You can use blu tac between the cones and the bottom of the speaker...it usually works quite well. I like the suggestion though that Sanjay has given regarding the placement of the sub and speakers. It is particularly important to get the sub placement right in a room and you can get rid of quite a few problems. Bass traps are often not the first remedy to try.

 

[sash]

Pls check my experience here
http://www.hifivision.com/av-enhanc...y-ht-room-acoustic-treatment-need-advice.html
1. I found that corner super chunks are the easiest bass traps to make and they work as far as i can tell.
2. You must make a frame - corner traps will have a triangular frame, with the front open. You must then stack the fibreglass inside it. Thicker the better. Go for fibreglass slabs (higher density) rather than flaky/wooly ones. Easier to work with and absorbs better.
3. You must secure the fibreglass for sure. I used a thin foam of very low density. These are yellow colored sheets you get in all mattress shops. Thin and porous. But they hold the fibreglass well.
4. One another thing - it is important to treat tri corners. The four on ceiling (there are four where walls meet floor but we can ignore that) are important. I haven't done anything for them yet but planning something soon.
5. i haven't treated the ceiling but many think that is important. I think so too but it turned out to be an expensive proposition for me. But atleast try and minimize parallel surfaces anywhere you can. For example putting up irregular claddings on walls and ceiling helps i have heard.
6. I haven't measured the gains. But i can now watch an entire movie without fatigue - which in itself speaks a lot.
7. I will continue to add as much acoustics as i can. My next focus is to reduce parallel surfaces as much as possible.

 

[sdurani]

Problem here would be sub and center channel would be on the same line, like one on top of another with height difference of 2.5 feet.

Why is that a "problem"? On the contrary, if male vocals ever leak into the subwoofer, they will come from the same direction as the rest of the dialogue (centre speaker).

I was in the assumption that corner location for Sub are the best.

Only when it comes to output. The three boundries in a corner (floor and 2 walls) give you a 3dB bass boost. However, if you're looking for quality rather than quantity, then there are locations that give better/smoother response (fewer peaks & dips).

 

[Pitchucold]

Thanks Suraj, Sanjay for response.

Sash, I am trying to play with speaker positioning first then try chunky bass traps route.

As mentioned i tried both the options (with and without sub) for watching movies with lot of action. I preferred the option with Velodyne sub. It makes the sound felt in my sitting position. So i would like to dial sub into the room.

Sanjay, as far positioning suggested by suraj is concerned, my question was not on the technicaly difficulty but more from the positional difficulty. I have placed the speakers at 2 Feet from rear wall and from side wall. Position the center of the center cahnnel at exact center (5 Feet from Either Side).
I could not place the sub at 5 feet due to the racks i have. I could only place it at 1 feet offset to the right. (6 ft from left and 4 ft from right). I could not try on how it sounds in morning due to power outage at home, will try in the evening and let you guy know.

Suraj, I shall check again with Magma on spikes. I checked on the speaker stands. I liked the SAL ALIF Stand with stainless steel square pillar. They look better than DIY stands i did couple of years back. I could not hear a big difference in DIY Stands vs current option. Difference was clear when i was using JBL CTRL 1, but i did not hear a difference with RX 1 with my DIY stands.

http://www.hifivision.com/audio-video-accessories/1461-av-rack-chennai-5.html


In the current option, i have placed the speakers on a box filled with Sand and with granit top. I have this for Fronts and Center. Do i still need to install spike on bookshelfs that stand on granite ?? Attached photos along.

 

[sdurani]

I could not place the sub at 5 feet due to the racks i have. I could only place it at 1 feet offset to the right. (6 ft from left and 4 ft from right).

Mode cancelling will happen with the sub 5 feet from both side walls, but that doesn't mean the sub has to be at/near the front wall. It will work just as well with the subwoofer anywhere along the room's centre line (near the back wall, under the bed, either side of the bed, etc). As long as it is 5 feet from both side walls, you are free to place it anywhere possible across the entire length of the room. Take advantage of that placement flexibility to get better bass.

 

[Staxxx]

Personally I would decouple the speakers from the granite top. But if you feel the difference has been marginal in the past (this could be due to a very well made enclosure), then I would not bother.