How I built my bass (broadband) traps...
 

Hi!

There seems to be alot of talk about bass trapping on the board right now so I thought it was a good idea to post some info on how I built mine. I really want to encourage everyone to build their own, it's easy and well worth the effort! kfhkh

Each trap is built as a 17 cm deep frame housing 15 cm (6") of rock wool (not the brand) then the front and back is covered with fabric.

Here is the material for the frame. You can also see four angled metal plates. They are there to prevent the rock wool from slipping out the back.

/Cojo

Here is how they should fit together...

Glue...

That'll work.

If you want to expose a bit more to the world, try drilling some holes in the sides, top and bottom.

Bryan

...and screws.

The finished frame! I'll post some more pictures tomorrow.

/Cojo

Thanks for you're advice! thumbsup

I've thought of doing that. How much more efficient would you think they will get?

/Cojo

thanks for sharing this kfhkh kfhkh kfhkh

cool!kfhkh

Well on a 4x2 4" panel it would give you 50% more exposed area if the sides are open.. 6"? well, check my numbers but that would be 75% more exposed would it not?

Nice DYI dude! kfhkh... You may want to think about putting some FRK on the fronts. This will help with a little more low end and also keep the room from going "DEAD" on the high end.

Glenn

Nice kfhkh

Thanks for this guys.
What is FRK?

FRK/FSK is a scrim facing that comes on some insulation products. It's paper on one side, foil on the other, and has a reinforcing mesh in the middle.

The purpose is two-fold:

- act somewhat like a damped membrane increasing absorbtion at a specific band based on the density of the material behind it.

- reflect upper mids and highs so you can absorb the bottom without overdoing the top and making it too dead.

Bryan

nice

You're right. I did the math and if I could fully expose the side, top and bottom the area would increase about by 80%! With the framing a more realistic figure would be in the 40% area. I didn't think it was so much. Unfortunatly these absorbers are allready done but I've allready plans for another batch so I probably make them with exposed sides.

Thanks for the advice on the FRK. Each trap is made of 3 slabs, I want them to absorb hi end aswell. What about putting FRK so it's facing the front between the first and second slab?

Thanks again! kfhkh

/Cojo

Anytime! kfhkh

Yep, thanks! diddlydoo

To kind! bumpkin

I'll post some more pics this evening!

/Cojo

How do u mean "expose" them?
Do u mean expose the rockwool inside so that on certain sides it isn't covered by wood and heavy material?

Yep, excactly! But it's hard to use all 80% because of the frame. So in round figures 40% would be more realistic.

/Cojo

I'm using a frame made of 1'' by 2'' wood in the back of 2 2" 703 pieces.
Cloth is stapled to the wood frame holding the firberlass is place. This makes the frame much lighter and easier to hang. Is there any problem with building the traps this way?

Ok, the frames are ready and it's time to get the insulation in place. I use a ground slab from Paroc. It's a very hi density mineral wool.

Here's a picture of the label.

The open package.

The first slab gets fitted. It's very tight and if you've done accurate messures it actually stay in place without any need to secure it. I've choosed to secure it anyway.

First slab in place at the back, two more to go in front of this one.

And here it is with all three layers.

Conny,

This is fantastic, and something the acoustic DIY community can benefit from in a big way.

There is s BRAND NEW Acoustics forum just about to go live that is non-commercial and is dedicated entirely to idea and application of DIY ACOUSTIC TREATMENTS..


Would you be interested in sharing your project at this new forum?

Please PM me, or email me through the website.
Your contribution would be enormous and greatlt, greatly appreciated.

Cheers,

Joel DuBay
www.readyacoustics.com

Here's another picture of all four traps ready to get the final treatment! I'll post those pictures later.

/Cojo

Hi.

If you have wood in the back of the 703 you can't distance them from the wall and they will not be as efficiant.

/Cojo

Thanks for replying. I hope I'm not hijacking the OP.

The wood is 2 inches wide and about 1.5 inches deep, so the 703 is 1.5 from the wall (I'm using these on the corners of the room).
Am I missing something?
Thanks.

Aahhh... Now I see! Sorry, I had a hard time reading your sketch. heh

It looks fine! My mistake. kfhkh

/Cojo

If you want them to do mids and highs too, then don't use any FRK/FSK. The point of it is to be able to do more bass control without overdoing the highs.

Bryan

GOSH GOLLY!!!

Those things are massive! Is the board 3/4 or 1 inch?? The wood looks really thick!

They would probably survive a tornado!

Good job, and nice craftmanship....kfhkh

Got it! kfhkh

Ha, ha... yeah they probably will! hittt They are 22mm so it's someway between 3/4 & 1".

/Cojo

Excellent thread! kfhkh

Conny if you don't mind could you also post pictures showing how these traps are mounted onto the walls? I get how the frame is made but still don't know how you would keep them a couple of inches away from the wall..Thanks!

Hi s-cube.

I have not yet decided how and were to mont/place them. Right now they are floor standing. I really dont want to make to many holes in my wall since I have the studio in my apartment right now. Maby I'll make some stands for them instead.

But if I was mounting them on the wall I would probably "hang" them on ordinary shelf consoles. Just make sure the consoles are long enough so you can space the traps out from the wall. If the lower part of the trap tends to tilt in, just put some distances there.

/Cojo

Here is some more pictures. In this picture the frames has just been painted.

This is the strips that's gonna cover up the staples that's holding the fabric in the front of the traps.

HEY cojo...
vey niceeeeeeee man.... you rulezzzzzz as a DIY

can you post how the traps are now... did you gonna mount them on
floor stands... ?

hey also can you post a FREQ response graph...
without the traps and with the traps ...will be niceeeee heh

ROlo.

Me again! :)
Why do the staples need to be covered?
I'm guessing its for freq response reasons more than aesthetic, but I'd love to know exactly what effect they would actually have on the sound.
B

It's just for esthetics. I'll post some more pictures tomorrow when I get home then you will see what I mean! kfhkh

/Cojo

Hi.

I just have them standing on the floor right now. I'm planning on making four more traps but I havn't got the time yet.

I have some premitive graphs, nothing fancy gooof . I recorded a played back sine wave sweep from 20Hz to 200Hz in cubase. I'll post some screenshots tomorrow.

/Cojo

Hey cojo...
i sugest going up to 300hz.... ( many pros sweep up to 300hz ) for bass traping testing...

and also.. dont go so low as 20hz...
unless you have a fancy monitoring system
that goes that low....

most monitors... only go as low as 60hz to 40 on the best of the cases...
to say some... Mr. Bob Katz have a pair of Lipinkis L707 monitors but with Subs
to go to 20hz....

Even the Lipinkis dont go so low alone .. and cost 3000+ each...
Greets
Rolo.

Cojo,

The cost, ...is it translatable per unit to US dollars accurately?? Im not sure if you are using euros or , rocks with holes drilled in them, gold Dabloons, US dollars, German Phennings,....sheep, concrete goats???

IOW how much roughly was the cost for each , minus labor?

I just mounted my broadband absorbers yesterday and heres how I did it. 4" 0f OC703 and or 705 in a 1x8 frame with a 2 inch air space to the wall. A total of 5.5" from the OC to the wall. And then I made some 2" spacers and mounted them to the bottom of the panels.

Ha, ha! heh Exactly like my quote! hittt Nice! kfhkh

/Cojo

I wish I could use rocks with holes or maby concrete goats!? mezed heh

Actually the total cost inclusive paint and fabric was about €34/trap.

/Cojo

Here are the last of the pictures. This is the fabric ready to be stapled.

The staples are in and the fabric is getting trimmed.

Here you can see why I want to hide the staples.

And finally! Here they are, ready to be brought to my studio space. diddlydoo

It took about 4 days for me to build them, but that includes buying all the material as well. I think it probably possible to build them in two days if you plan your work better.

Oh... I almost forgot!

I'll promised you my spartan graphs... Here they are gooof . It's just a sweeped sine wave tone recorded about 1/3 in from the front wall in the center with a sm57 but you could clearly see the difference that only 4 traps do. The upper graph is the untreated room and the lower is the room with four traps (two in each front corner).

I've allready bought more material so I can make 4 traps more. Now I just need some time doing them! heh

/Cojo

I have tried loading up this image at least 20 times, I don't know why it doesn't show? Can somebody see it?

Both of your guys traps look awesome! Makes me want to break out the dusty power tools.....

But, at Glenns prices, plus my laziness and desire to keep all my fingers, I probably wont......wworried

This is how my construction goes:

no ..... ???

PS - just wanted to remind people who are using this (excellent) thread to plan their own bass traps....

http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/61293-diy-broadband-absorber-pictures-posted.html

kfhkh

...and this is one of the sketches, note that not everything is like in reality and everything evolves, colours, construction, problems... what I know now I want to have my table/console different... the back is not solved also to my liking... but I'm moving in as I write this diddlydoo

..and this is one of the sketches, note that not everything is like in reality and everything evolves, colours, construction, problems... what I know now I want to have my table/console different... the back is not solved also to my liking... but I'm moving in as I write this




That looks awsome

thank you so much for sharing..i luv this forumthumbsup thumbsup thumbsup stike stike stike

thumbsup

G-G-G-AAAAG-- GASP!

Thats a nice room.........

thanks cooge

I'm almost finished with the side "panels" and now I'm going to work on polys in front. There are construction problems I need to solve, because making computer model doesn't always tlanslate directly in reality hidz

they look great man!kfhkh kfhkh kfhkh

@matucha: really nice looking room. why the wood-panel in front of the 703? which effect does it have?

my guess:
his plan is to reflect & retain some of the high-freq´s while still absorbing
mid & lower mid freq´s......despite on ear-level (sitting) where you want a RFZ (reflexion free zone) ....am I right??


ethan....glenn.....
guys, down to what center-freq. do you think a plain 18mm OSB-board/hardwood board would reflect ?? any idea...guesses?

tom

danke tom. ich werde diese bauweise definitiv auf meinen studioraum ummüntzendiddlydoo

i got a second and hopefully last question: why the plastic-bags (don´t know the english name for it) on the 703?

tomdarude > exactly --- it is kind of experiment, will see how it is going to work. I've completed just one side up to this moment and the other is just bare construction with that red fabric covered panel attached to it... and it looks like it is going to work ;-)

Also these wood panels work as membranes, they are thick (18mm) so they should get the low bass... possibly ;-)... I tried to touch them when running bass sine sweep and what makes me happy is that each of the field is vibrating at different freq.... ie there is some "broad-band" absorbtion happening.



> OSBs should reflect very well
- it is heavier than wood is
- it has slightly non consistent surface, but I doubt it will have any diffusion effect

The plastic bags cover the rockwool just for the safety reasons (and you can manipulate it without wearing gloves). I saw that in every studio construction I've been to. I was told that it doesn't affect the absobtion a lot... and for basstrap use I think it should be acousticaly "transparent".

i talked with a contruction manager i´m working with in my company about the 703er..in german it´s called trittschall-dämmung as iám right. he said it isn´t as dangerous as a lot of people say. but you are: when you work in your studio every day, it would be dangerous don´t covering them from the air so that you breath them in.
your contruction is not only for audio-treatment, it looks really nice and professional so clients would be proud to work in ithowdy

Those look amazing cojo kfhkh

Thanks!

I'm suprised myself! heh I've learned a lot during the construction so the next ones I build would probably be even better. I really wanted the wooden frame but if I knew the were going to be so heavy I don't know... gooof

Thanks everyone for your support. It has been a pleasure to read! kfhkh

/Cojo

IMHO you can't make it lighter than "wood", ok some less dense wood is lighter, but you can easily damage the surface and the edges. OSB for ex. isn't light at all... it was no fun puting these osb frames on the wall in 2 persons.

And yep, cojo, you have classy lokin traps kfhkh

Yeah I can imagine... those looks really heavy as well but I think you gonna get a nice place when you're ready! kfhkh

Keep the hammer going! hittt

/Cojo

well, this is the end of my hijack of this thread... current situation just after moving in and making temporary setup for testing and getting used --- will continue in a new thread abduction

Cojo...
Nice traps
what hapened with the graphs... ?

cant see them...
did you read my post on the freq response of mainstream nearfields.. ?

Greets
Rolo.

Thanks!

I don't know what happened... it will not show after I've downloaded it? I'll give it a new try.

Yes I read your post about the freq responce. The problem frequences I've experienced when I have mixed in my room is those around 60Hz - 120Hz. That's why I didn't go so high as 300Hz but you're probably right, it may be a good idea! kfhkh

I have a Blue sky monitor one system and I know they can't play 20Hz but I really wanted to see it for my self! diddlydoo heh

/Cojo

Sorry It will not show!?? grrr

Anyway...

I've found this EFT program and I'll try to send some plots when I've figured out how to use it! kfhkh

/Cojo

Ok, lets see if this works...

YES!

This is the low freq response with no treat.

...and here it is with just four traps (one in each front corner and two against the front wall).

That looks rather cool, yet simple. Has me thinking about how I'm going to do it.
How would you go about amking those eliptical wooden deals behind the speakers though? Thats tricky stuff.

If your planing on using backing (I choosed to use MDF for my Gobo's backing),
Leaving an air tight space equal to the thinckess of the isolation between the isolation and the backing will give you much better results in terms of how low your broadband panel "can go".

for example:
Cloth - 6` 703 - 6` Space - Backing

Ok guys...

...the last picture! Here they are at place. I put them at the front wall and one at each front corner. After some testing this position seems to give the best overall response with just four traps. The next thing now is to get a small cloud up and some damping on the side walls.

Thanks for your interest!

hooppie

/Cojo

how much did it cost to make these traps? i'm looking into making some, or buying some from GIK. Which would be cheaper? I figure i will build gobo style stands for the gik's if i bought them.

Also, where can i get 703 in northern california? do they sell it at home depot or do i need to order it online?

The ones that Cojo made should be quite inexpensive, when I calculated all the money I payed to build mine, it was around $200 for one panel. Seems like nothing...

Well, don't keep it a secret. Link please? cooge

Hi.

The cost/trap was 34 euros.

/Cojo

Just trying to figure it out. There are ways how to bend plywood to various shapes (for ex. some chairs are made from that). But I'm going to just force a thin flat plywood into a frame of some kind... with some bulkheads... and for the fabric covered parts I'm going to use perforated sololit with high perforation %, that should act like almost uncovered wool.

Will see, I'm about to start building it...

I would have thought that thin plywood would have been easy to bend to that kind of shape. I wonder if you might need some kind of dampening material stuck behind them (like you get inside a car door or hood). They might vibrate a bit at their resonant frequency.

FWIW you can get flexible MDF (it has parallel grooves cut into it) that you can easily bend into cylinders etc.

That's why I have two packages of rockwool in the yard waiting to be part of it ;-).

I hope it is going to bend well. I also saw this MDF, but I prefer to have the "same" material on the front wall as on the side walls. MDF or sololit is an alternative though...

Do you need the frames ?

I currently have a bunch of panels made like: (1) 1" 705FSK (foil out), backed by (3) 1" 703's. All four are together making a 4" panel wrapped tightly in a homemade burlap "pillowcase".

When I put them in the corners as bass traps, I put the foil side away from the wall, and when I use them as absorbers, I put the foil side to the wall.

I just noticed a lot of people doing frames. Is there a reason other than aesthetics, and increased mounting ability ?

Have I done it wrong ?

You don't need frames. I did the frames just to make them sturdy and look good.

/Cojo

Cojo...

i have read that the more the bass traps you put... the TIghter your freq response
will be ( more flat )

you did make just 4 traps... ? or more ?
you can try with 6 or 8 :)

Greets
Rolo.

BTW NICEEEE SETUP mAN!!!
you rulezzzzzz

Hi and thanks man! diddlydoo

There is so many different brands and types of mineral wool therefor I wanted to start with a few traps just to see if the mineral wool that I used would really work.

I have already done some more traps; two 4" to put on each side of the mix position and a 2" cloud. The plan is to do two more 6" for the back corners and a 2" or maby 4" for the back wall.

So when I'm done I will have six 6", three 4" and one 2". That's ten traps, hopfully it will be enough. Otherwise I'll just do some more! hittt

/Cojo

Cojo, thanx for your detailed report! I'm going to build a good number of traps the same way.

Question: You did use 3 slabs. Would it make a difference if I would use 2 bigger or one big slab? Would be a little bit cheaper and faster to build.

It has been mentionted there should be holes on the top and bottom of the frame. How big should they be and where should they be placed? Should there be holes on the sides also?

What kind of fabric should be used if there are going to be many traps in a small room (to not kill the highs too much).

Thanx guys for all the information.

It's not quite as scientific as that. The idea is to expose as much of the rockwool/fibreglass to the surroundings as possible. So you need as many big holes as you can without weakening the structure of the panel.

There was some traps pictured on GS recently which had loads of 2" holes drilled in the sides/top/bottom, or check out the realtraps ones. This should give you the general idea.

http://www.gearslutz.com/board/so-much-gear-so-little-time/89516-my-insprirations-diy-basstrap-builders.html

I have no idea on this other than i know i should do it for good recordings.. does it make a difference if you have say 4 big ones in each corner as opposed to say 10 smaller onces spaced out around the room?

It is not going to matter as far as absorption goes. The more of the over all area that you expose on the sides the more sound will get into the panel. Don't over think it. kfhkh

Glenn

No. I just used three layers because they didn't have 6" panels at the store.

As orange said. Make them as big you can without weaken the frame.

Don't worry to much if you are not going to cover half the room. I went with a cheap IKEA fabric that had some small stretch.

/Cojo

Glenn, I think Docmattic might be asking about general basstrap placement rather than specifically about 'the holes" ???????

Basstrap placement is important, it's important to treat corners (as bass 'collects' round the corners and you'll get maximum absorbtion) and first reflection points from the speakers to your ears.

I used the same fabric from IKEA kfhkh


Be aware that I don't think that this fabric is flame ******ent - it might or might not be an issue for you.

mezed mezed boy you are totally right. I read the post super fast. Sorry about that.