Bass traps

**Fincave** · **10-30-06, 02:14 PM**

Some basic info first:

Room is 4.95m by 3.9m by 2.4m. Floor is laminate ie hard and very reflective, have one carpet on the floor, natural fiber but pretty thin so not doing much for absorption. I have acoustic panels made from rigid fibreglass on the walls, left wall coverage is probably about 45%, right wall coverage 15%, front wall coverage is about 25% and cannot place much more as my screen takes up the rest of the available space. The ceiling is entirely untreated and made of concrete covered in plaster, same as the walls.

Installing the panels improved my sound quite dramatically, I had a lot of echo before doing the 'clapping test', now there is none. My speakers are Amphion Argon2's and can probably be described as very accurate monitors, some people have said that mid and higher frequencies are harsh sounding, I have no problems in that regard. Bass is take care of by a BK Electronics Monolith, more than ample for my small room. Am also using a BFD to tame the subs response, the response is not ruler flat by any means yet, but still pretty good, at least to my ears.

The problem: My only problem is to some of the bass sounding boomy and I was wondering would traps work to solve this?

I was thinking of building my own traps and putting them in the four corners of the room. They would be triangular in shape and would consist of a wooden frame with the front face being a rigid fibreglass panel 30mm in thickness. Am not sure what would be the best material to fill them with, fibreglass or rockwool, both are available here in varying densities. The traps that would be in the front of the room would have a volume of roughly 55 litres and in the rear 110 litres.

1: Will traps solve the boomy sounding bass?

2: What would be the best material to fill traps with?

3: Will the traps I have described be big enough?

**F1 fan** · **10-30-06, 05:38 PM**

A triangular shaped corner trap called Super chunks seems to be popular and effective.It is made up of many wedges of OC703 rigid fibreglass. Here is a link to one way of doing it .see about half way down the page.http://www.radford.edu/~shelm/acoustics/bass-traps.html

**JCD** · **10-30-06, 06:25 PM**

Ethan Winer has a link to his DIY bass traps -- here.

Will it fix your problems? Probably not entirely, but it should help A LOT.
Hopefully Bryan Pape and/or Ethan Winer could chime in with some additional info.

JCD

**Fincave** · **10-31-06, 01:21 AM**

Thanks for the replies! Have actually read both the articles mentioned. The 'super chunks' idea seems to very doable, the only problem being all of the rigid fibreglass panels that I have seen available here in Finland have a coating on the front, presumably to make them acceptable appearance wise and to restrict loose fibres from becoming airborne etc. Cutting up these panels would become quite pricey, probably end up costing about $400 for the two traps I have planned for the front corners, double that for the rear corners. Filling the traps with fibreglass and using a panel for the front face would bring the price down to about $160 for all the traps but am not sure as to how effective they would be. Have to pay another visit to the hardware store and have a look at the available materials.

**drf** · **10-31-06, 02:18 AM**

nice, please keep us posted on how you go with this, I have a very similar sized room which will require similar treatment but am unsure of the best path to take.

I can't imagine you would need 4, but then I am not an expert... yet. Are there particular frequencies that boom?

**bpape** · **10-31-06, 08:32 AM**

You can fill the back with a less dense material as long as you fill it completely. A bit of compression won't hurt either.

It's hard to say if it will be enough as you specificed the volume but not the surface area exposed to the room which is a critical piece of information.

Bryan

**Fincave** · **10-31-06, 08:51 AM**

The front face of the smaller traps would be 60cm X 60cm, the rear traps 60cm X 120 cm high. The traps would be triangular in shape with the sides being roughly 42cm X 42cm X 60cm and would not be placed flush into the corner, probably a gap of 2-3cm all around though they could be flush mounted if it would be beneficial. Hope this info makes sense! Thanks for all assistance!

**bpape** · **10-31-06, 08:57 AM**

Those will help some but may not be enough. For that size room, I'd want a minimum of 4 of the 60x120's. Get them flush into the corner if you can.

Bryan

**Fincave** · **10-31-06, 11:54 AM**

Have done some more reading on the subject of bass traps and came across DIY tube traps. The tubes are apparently available here and are not expensive at all. Anybody with any experience of these traps? The tubes that are available here come in different sizes, wall thickness of 5cm or 10cm, diameter of 10cm, 12,5cm, 16cm and 20cm, all the tubes are 120cm tall. They would be easy to place in the corners and could also be placed in a row along my rear wall behind my sofa. The question being are these effective at all?

Here are some of the links I have been looking at:

the tubes

diy 1

diy 2

info

**geekwithfamily** · **10-31-06, 02:31 PM**

According to Jon Risch the pipe insulation traps don't do anything because the material is too dense. He has instructions to make ASC-esque tube traps by compressing fiberglass insulation around an open cylinder. I just made his "quick and dirty" traps and they helped my room boom (absorbing bass overhang). The great thing about the quick and dirty's is you can just buy some packaged rolls of fiberglass insulation and throw them in your room's corners and see if bass traps help at all. If they don't work out just return them (as they're still in the package) or further insulate your home.

**brucek** · **10-31-06, 02:38 PM**

Quote:

If they don't work out just return them (as they're still in the package) or further insulate your home.

Great idea.........

**Fincave** · **10-31-06, 03:34 PM**

Thanks again for the info and links! Had a thought, not sure if it is doable or feasible so correct me if need be. Basically have two discs, say MDF 2,5cm (1") thick and give them a diameter of 40cm (15,75"), join them using a sturdy dowel rod about 100cm (40") long. Wrap fibreglass insulation around the dowel using duct tape or wire to hold the insulation in place if need be. Not sure how tightly they would need to be wrapped/packed? Then ask my girlfriend very nicely to make a cover for them out of material. I could then place these in the corners and maybe somewhere along the side walls, these could then be used as stands for plants or lamps etc. Suggestions and comments most welcome.

**Ethan Winer** · **11-01-06, 09:59 AM**

> According to Jon Risch the pipe insulation traps don't do anything because the material is too dense. <

That's bad advice. Pipe insulation absolutely works.

--Ethan

**Fincave** · **11-02-06, 05:04 AM**

Probably going to try the tube traps as soon as I can get to the hardware store. Should they not do anything I amy well try the 'quick and dirty' traps. Have more questions though, is BIGGER BETTER? What influence will the internal diameter have and should I go for the thicker wall size. Also, would fiiling the inner cavity with fibreglass have any effect, it kind of makes sense to me that it would make a difference. In the articles I have read both suugest leaving half of the tube reflective and half not, WHY? Am sure will have more questions still. Thank you for all the assistance thus far

**bpape** · **11-02-06, 06:14 AM**

Bigger is better (deeper at least).

I'll sit on the fence between Ethan and Jon. Jon is incorrect that the issue is density. He is correct in that per area of floor taken up, there are a LOT better, more effective, cheaper solutions than pipe insulation. It's not that it can't work.

IF you fill the tube with fluffy stuff, it can work pretty well - if you can get maybe a 16" or larger diameter tube. But, think how far that will stick out into the room. A 2' wide chunk in the corner provides more surface area exposed directly to the room and takes up half the floorspace.

There CAN be issues with density if you expect the tubes to be broadband absorbers. For the same reason that less dense materials work better for reflection absorbers when you have shallow angles of incidence. With a tube, you have TONS of refections at those shallow angles. This is only an issue from say 1kHz up but I personally don't want that area spraying around randomly in my front soundstage.

Bryan

**basementjack** · **11-02-06, 10:41 AM**

I have built a few of the tube traps using the instructions at http://www.teresaudio.com/heaven/traps/traps.html.

They weren't that hard to build, but they weren't that easy either.

The problem for me, being a perfectionist, was the circle tops and bottoms, I used a router and a circle jig and cutting down 1/8 in at a time made a nice template, then I used a 'tracer' bit, mounted to a router in a table, and stacked the template on a roughly cut piece to make the others. It was time consuming and the circle gig, and template bit ended up costing me about $50 USD

I can settle the density question - I weighed a piece after removing the foil, and caluclated how many cubic feet were in the piece I weighed - (these were Knauff 1000deg pipe wrap) - it came out to 3Lb/cubic foot.

I made 2 approx 22 inch diameter, 2 inch wall thickness traps, and 4 appox 13 inch diameter 1.5" thickness traps.

I have to say I didn't notice a huge difference with them.

I will take some room measurements and post them at some point in the next few weeks.

In the mean time, I think the idea insulation rolls from the home store is a great one - as pointed out - it's cheap, easy, and easily reversible.

I'll also comment that The traps look ridiculous. I honestly think the marginal improvement in acoustics doesn't justify the look on my wifes face. There has got to be a better way....

**bpape** · **11-02-06, 12:53 PM**

Looks is certainly an issue - hence my point on the slabs straddling a corner taking up a LOT less space.

Now, if you take that same 22" tube and fill the middle with fluffy fiberglass, I think you'd notice a larger difference in the bottom end.

Bryan

**Fincave** · **11-06-06, 12:13 PM**

Will be picking up some high density rockwool panels tomorrow and ave decided to cut them into wedges and stack them in the front corners. From one package I will be able to get two traps which will be 50cm across and 100cm tall, plus some wood for a frame and some material to cover them and the total cost should be about $25. Hopefully they will make a difference and depending on the results wil make another two for the rear corners. Once I have made the traps will post as to any results.

**JCD** · **11-06-06, 05:18 PM**

Since I'll be working on my room soon (hopefully) and will be addressing the accoustics as well, I look forward to your impressions of the results.

JCD

**F1 fan** · **11-06-06, 07:12 PM**

I am also interested in your results as I plan to to build a pair of these.
May I ask what is the density and thickness of the Rockwool you are using?
I don't think the OC703 product is available in Canada but I have found a Roxul Rockwool product that may work.It is called Drain Board and is 1" thick with a density of 8lbs pcf.It is even dense enough to cut on a table saw.

**bpape** · **11-06-06, 09:21 PM**

Actually, if you want to emulate 703, see if you can get some Roxul RHT40.

Bryan

**F1 fan** · **11-06-06, 10:05 PM**

Quote:

bpape wrote:

Actually, if you want to emulate 703, see if you can get some Roxul RHT40.

Bryan

Thanks Bryan for the tip,it should be no problem getting the RHT40.

The Roxul site states it has a density of 3.5lbs pcf.Would the product I mentioned (see link)with a density of 8lbs pcf be even better suited for bass trapping duties or is that too dense?
http://www.roxul.com/graphics/rx-na/...sh_5-12-06.pdf

**bpape** · **11-07-06, 06:30 AM**

Depends on how you do it. If you're going to use 4" straddling a corner then the 8lb would be a better option. If you're going thicker or even chunking it, no need to spend the extra money. As you increase thickness, you can slack on the density a bit and still get good performance.

For the same money, I'll take 8" of 4.5lb over 4" of 8lb any day.

Bryan

**tjschuhow** · **11-07-06, 10:24 AM**

If you're looking to eliminate unwanted bass at frequencies below 100Hz, you'll need to have some type of material that actually absorbs the acoustic energy. Obviously, right? But typically, fiberglass insulation - even dense 705 FRK mentioned in Winer's article - is acoustically transparent below 100 Hz. So you need another level of function, some type of material or process to swallow up these 10' + energy packed waves.

I've used hanging absorbers in the isolation booth of my studio derived from the formula in 'Acoustics and Psychoacoustics' by Argus. After they were built, I subscribed to Sound on Sound magazine out of the UK and discovered an even handier bass trap built by Paul White, Editor in Chief of SOS. This design is unique in that it's similar to a Helmholtz absorber, yet instead of pegboard, it uses

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