What is your best bass trap?

[anseo]

I need some serious bass trapping, in the area of 40 - 150 Hz. I haven't time to build them myself, so I'd be grateful if anyone would share their experiences with traps that WORK (or don't work..).

Thinking of RPG Modex Plates or Modex Corners. Or maybe Mondo Corner traps from Realtraps.

I was planning to post this on the acoustics forum, but after reading a thread on how to build your own bass trap I was baffled to find that most of them had little understanding of acoustics. That didn't inspire much confidence, so I decided I'd rather ask the studio owners of the high end section.

[Petrus]

The wall behind the monitors is covered with heavy drapery, behind which is a 60 cm deep space filled with: 10 sleeping bags in big cotton sacks, about 6 backpacks, 6 tents, outdoor clothing on hangars, climbing & camping gear etc in steel mesh baskets, one large ski pulk. Oh, Genelec 7071A subwoofer...

Seems to work extremely well. I have tried to concentrate the soft things (down bags and clothing) in the corners a bit.

[anseo]

Buying 10 sleeping bags would be a cheap option :D

But in theory these shouldn't absorp as low a frequency as I need to go.

I have a lot of absorption (rockwool) already and that really helped with things like imaging and bringing down reverbtime, but not for the low frequencies. I have some severe standing waves and need heavy attillery!

[Micah Tolentino]

well if you have money to burn go ahead and buy traps, the most expensive you can find. But why do that when you could put in a little elbow grease, and put in what you know about acoustics and build your own? Then use the rest for new mics and pres?

I can tell you that my "home made" traps did much more trapping then store bought ones, and really tamed 80-150 hz for my room. I used the typical 4' x 2' x 4" wrapped in burlap material in a wooden frame. I offset them from the wall, and Placed in the side listening positions and straddling the rear corners. This did wonders for me. My bass is translating much better now. I've used the auralex stuff for years, but honestly I felt like I wasted thousands of dollars on stuff that didn't address the full spectrum of frequencies. Their LENRD bass traps did absolutely nothing for me

All of the trap info I got from the acoustics forum. Theres some really good knowledge there you just have to know who to listen to. I'd pretty much listen to mainly the GIK acoustics and Realtraps staff. They know their stuff.

[anseo]

Thanks the both you for your comments. If it's better I do it myself, so be it.

I did built a number of the absorbers you mentioned, and they are terrrific, but not for bass trapping in my experience. For instance, there's an ugly standing wave at 76 Hz that's obviously not adressed by these units.

Um, aren't bass traps, like panel absorbers, supposed to be air tight? Because if it's just a frame with rockwool covered with chicken wire and burlap, that's an absorber, right?

[superama]

If its airtight how does the sound get in to be trapped?

Seriously, look at Acoustic Sciences Corporation. I have an Attack Wall in my control room which comprises some serious trapping as well as a Quick Sound Field for live room treatment. Both applications are primarily made up of 9 inch diameter tube traps. At least have a look to inform about treatment within the interior of the room as opposed to treatment just on the walls. If you treat the walls you reduce RT60. If the treatment is away from the walls you reduce the energy in the room and prediffuse the ambient sound reducing undesirable room artifacts such as flutter echos, etc at the same time preserving the RT60 of your live room.

ASC Studio Traps are extremely effective. Check 'em out

[asagaai]

Originally Posted by anseo

I did built a number of the absorbers you mentioned, and they are terrrific, but not for bass trapping in my experience. For instance, there's an ugly standing wave at 76 Hz that's obviously not adressed by these units.

Um, aren't bass traps, like panel absorbers, supposed to be air tight? Because if it's just a frame with rockwool covered with chicken wire and burlap, that's an absorber, right?

Anseo- bass traps do not need to be airtight. Also a bass trap is effectively a bass module absorber- the design will effect the effectiveness of absorbing very low frequencies.

It is recommended that there be a gap behind the bass trap and the wall. Theory being low end goes into the trap (layer or rigid fibreglass) through it, bounces back off wall, and the cavity between the wall and the bass trap fibreglass layer traps the bass. Alton Everest recommends a gap of 6-7 inches between the rear of the fibreglass and the wall.

So although stacking rockwool in the corner is good, even better if you can effect a gap between the "basstrap rear" and the rear of the wall. Alton Everest has written a guide on basstraps- and gives the gap between the wall and rear of the basstrap.

The front of the basstrap can be covered with cloth- which means it is not a basstrap per se- but a broadband absorption trap. To have the trap only absorb low frequencies, you need to place over the front of the trap thick plywood, which then reflects back out the upper and mid frequencies.

You then tune what level frequency your trap absorbs by the size of drill holes in the plywood and the perforation percentage of the plywood surface.

So for instance- no cover or perforation of at least 25% of the front cover results in effective absorption coefficient of 1.0 from about 250 hz all the way flat lining past 10khz. So- this will be a broadband trap, absorbing everything above 250 Hz upwards.

A plywood cover with 0.5% percentage perforation (equates to 26 3/16 holes per square foot drilled into the plywood cover) is a true bass trap- as it starts absorption from 40Hz at some 0.4 absorption coefficient, peaking between 90 and 170hz, and from 200 hz becoming less effective until it does not do much absorption at 900HZ onwards. This is great design for bass trapping but not absorbing the higher frequencies if you are concerned about deadening the room.

After looking at the commercial "basstraps" which I thought was a joke, I bought 7 foot pine corner cupboards, with 4 deep cornershelves. I drilled out the two rear walls of the bass traps facing the rear corner (as well as the top and bottom) with heaps of 3/16 holes to make it effectively "open" at the rear, and on top/bottom. I then stacked up with acoustic rockwool and covered the front with nice black patterned cloth. These I placed 3 inches off the rear corner walls to give a "airpocket" between the room corner and the back of the corner basstraps.

My monitors stand in front of these monsters and I can really say that the results were incredible. I had huge problems before- I use Event ASP8's which really need good bass trapping and had huge issues before hearing the low end- now its great-tight but so deep.

So good that I built a further 2 for the tracking room, for drums, but covered the entire front of the unit with thick plywood. I wanted to absorb low bass at the rear, but reflect back from the front higher frequencies into the tracking room. So I drilled the plywood rear two walls facing the corners with heaps of holes to make the rear "open", and the front had a very thick plywood cover. I drilled that cover with about 0.5% perforation to preserve frequencies above 1000hz in the tracking room as my tracking room is already too dark because of other treatments.

Works great on drums.

Good luck and hope this helps

GJ
Newcastle/OZ

[Jim Williams]

I just open the back door. Works great. Plus it lets the sea breeze through...

Jim Williams
Audio Upgrades

[Swing]

About 8 or 9 years ago I tried to tame a severe hump at around 100hz (if I remember correctly). After a friend helped figured out the problem, I went out and bought some commercial traps spec'd to help at around that frequency (I think I remember the brand but I am unsure so I'll keep it mum). They did not do much at all- just changed the frequency balance a little bit and I still had my hump.

So I asked a friend for help and he spec'd out a DIY solution using particle board, plastic wrap, chicken wire, fiberglass, etc. I put in about 14 hours building 4 traps. The worst part of the experience was that for the first 2 traps I cut the particle board with a cheap hand-held jigsaw I bought. That was unpleasantly difficult and so for the second pair of traps I asked a guy at Home Depot to use one of their giant machines to cut my particle board.

Thereafter my hump was gone and I sold the commercial traps at a little bit of a loss.

I am no longer in the same place, am more than a thousand miles from a Home Depot, and I've been thinking recently about tamping some resonance in my room. I think a few small rockwool panels will fix my small issues. But for anything more serious I think something like GJ's solution is the best route, even if it is not a quick fix as requested by the OP.

[Ethan Winer]

Originally Posted by anseo

Thinking of RPG Modex Plates or Modex Corners. Or maybe Mondo Corner traps from Realtraps.

The RPG stuff is great if a bit pricey. What matters most is size. Small panels or tubes simply can't target frequencies below 100 or 200 Hz. Note that the biggest and baddest bass trap RealTraps sells is our new MegaTraps. They have a front face almost three feet wide, so they absorb well to even lower frequencies than MondoTraps.

--Ethan

[robertshaw]

Owens 705

[Swing]

Ethan, after looking at the realtraps site your megatraps look to be pretty effective. However, after clicking on the photo, which is to support the claim of a very high WAF, I am not so sure the actual WAF is very high: RealTraps - MegaTraps

[Ethan Winer]

^^^ If the traps match the wall color, or are at least similar in color, you don't even see the traps. It just looks like the wall is angled in the corners.

I only wish I had the same color as my walls when I took that photo in the rear of my living room using our black prototypes. And now it's too much of a PITA to replace them with wheat color.

--Ethan

[anseo]

Thanks, most comments above are food for thought.. Pondering about going DIY or commercial units.

My main concern is, if DIY Rockwool panels really can reach bass frequencies, seems to good to be true.

[Swing]

Again, I think what asagaai/GJ has posted is good info. I've also built many rockwell panels, for the same room as those 4 bass traps. And my experience is that rockwool panels which are in managebale sizes will not reach "bass" frequencies, which to me is anything down from around 130hz or so, and the further down the less effective a manageable a rockwool panel will be. Aside from plain diminishing effectiveness at lower frequencies, one problem is that after a certain point the rockwool panels become too thick and too heavy to be constructed easily into a panel format- and that is the point where tube traps are just easier. . . . this is just my own experience . . .

[asagaai]

"Swing" - Aside from plain diminishing effectiveness at lower frequencies, one problem is that after a certain point the rockwool panels become too thick and too heavy to be constructed easily into a panel format- and that is the point where tube traps are just easier. . . . this is just my own experience

Thanks for the endorsement Swing, and I agree- decent bass traps are heavy- the corner units I built took huge amounts acoustic rockwool and are heavy- need 2 people to move - but jeez talk about eating all the bass down low.

And IMHO they look cool- if anyone wants to see how they turn out pull up my webpage in the gearslutz tab and you will see the corner units with Event ASP8's in front in the control room.

Before building these I had a look at commercial corner bass traps and they were a joke for pretty expensive money. Oh- the specs I quoted are not my brilliance but comes from the master- F. Alton Everest in "Master Handbook of Acoustics- 4th edition."

GJ
Newcastle/OZ

[SRS]

Owens Corning 703 in as many corners as possible, and as thick as you can or care to lose the space. Thicker the better. Think "corner chunks" on steroids. The specs and real life performance speak for itself.

[anseo]

Originally Posted by asagaai

A plywood cover with 0.5% percentage perforation (equates to 26 3/16 holes per square foot drilled into the plywood cover) is a true bass trap- as it starts absorption from 40Hz at some 0.4 absorption coefficient, peaking between 90 and 170hz, and from 200 hz becoming less effective until it does not do much absorption at 900HZ onwards. This is great design for bass trapping but not absorbing the higher frequencies if you are concerned about deadening the room.

GJ
Newcastle/OZ

Thanks GJ, this looks like what I'm looking for. There were surprisingly few favourable reviews of commercial traps, so I guess I will first have a go at it myself. If that would prove unsatisfactory, I will probably buy Ethan's corner trap or Modex corner traps.

Er.. holes of 3/16 diameter.. that would translate to almost 5mm drillholes right? Just want to make sure before I mess things up. If there's any construction info on the net or in a book (Alton Everest?) I would really appreciate it if someone would let me know where to look.

[asagaai]

Originally Posted by anseo

Thanks GJ, this looks like what I'm looking for. There were surprisingly few favourable reviews of commercial traps, so I guess I will first have a go at it myself. If that would prove unsatisfactory, I will probably buy Ethan's corner trap or Modex corner traps.

Er.. holes of 3/16 diameter.. that would translate to almost 5mm drillholes right? Just want to make sure before I mess things up. If there's any construction info on the net or in a book (Alton Everest?) I would really appreciate it if someone would let me know where to look.

Hay ANseo- about 3/16 diameter- just go to a hardware store and buy a bit in 3/16- they will stock them.

Also- if you build a corner cabinet like I said-with heaps of volume for rockwool- it will work- and I suspect better than the commercially available ones cause it will have like x 8 times the volume of rockwool in ewach trap.!!!. If they are just to sit in the corners behind the monitors then I personally would leave the front open with a nice patterened cover material, to act as a broadband trap- with the 2 walls of the cabinet facing the walls drilled out as much as possible- again so the 2 rear walls of the basstrap also act as a broadband unit. If you stuff heaps of volume rockwool it still eats bass down low IME, and will control unwanted higher frequency crap which you do not need coming from the 2 corners in front of the mix position

If you are really stuck locating the Master handbook of Acoustics 4th edn, by F Alton Everest send me a pm,

Cheers

[James Lehmann]

You might wanna post this in the dedicated Forum for er... Bass Traps.

Anyhoo - I can confirm that just a couple of RealTraps MondoTraps took care of a major 60-70Hz problem in my room. No question these things really do what they say on the tin. Good company to deal with too. Recommended.

[Multi-Monitors]

I've heard that mattresses work well...

[RKrizman]

Originally Posted by anseo

I need some serious bass trapping, in the area of 40 - 150 Hz. I haven't time to build them myself, so I'd be grateful if anyone would share their experiences with traps that WORK (or don't work..).

If you or anybody knows of anything that can target 40 hz, let me know. I don't think any of the commercial offerings mentioned here can do it.

Also, yes, check out the studio construction forums.

-R

[spectrasound]

I used commercial bass traps in my 27 x 17 x 9h mix room. Took care of upper bass but not a fundamental problem I had at 32 and 64 Hz at the producer's desk. I designed & built one huge floor to ceiling corner trap (triangular 4 ft. wide floor to ceiling) to handle a problematic corner. Home depot materials. Packed very dense fiberglass (from roll, no paper) behind 1 x 3 framing. Chicken wire to hold it in. Made a nice framed cover with fabric to hide this huge and ugly trap. Looks great & nailed the problem,
pun intended. Bumps are gone (measured with band limited RTA) Cost of project $250 + sweat. Your best solution is self-education. I didn't have the cash to bring a pro in, so I became an "amateur pro". Best of luck!

[RKrizman]

How about pix and more details. Exactly what type of fiberglass did you use and how tight, and how, did you pack it? How much did it require to fill that space? Sounds like something I'd like to try.

Thanks,
-R

[kittonian]

The best ones I've come across (and I did quite a bit of research) are the Primacoustic MaxTraps and FullTraps. The MaxTrap is for the corners of the room and the FullTrap is for the flat surfaces. Not only are they really nice fabric covered panels but they are housed in wood with a floated vinyl mass with an air gap between. Excellent design and I've had nothing but outstanding results. I've got 8 MaxTraps, 6 FullTraps ,2 of the Primacoustic Diffusors, and an 8 foot ceiling cloud in my room and it's ridiculously accurate.

[RKrizman]

Let's look at some absorption reports. First the Primacoustic, which rolls off most in the 250 hz range and slopes off from there. See below.


Primacoustic - Acoustical Solutions

The GIK monster trap seems better in the super low end, as its maximum absorption occurs around 80 hz, when mounted across a corner. See this page and scroll down.

GIK Acoustic Panels are tested and certified.

Let's look at Real Traps. Here is data for their Mondo Trap straddling a corner. The absorption peaks at around 140 hz, with a smaller peak at 80 hz.

RealTraps - Product Test Data

The point is that none of these really get down in the mud and nail that 40 -60 hz area. The GIK seems closest by taking a big chunk out at 80 hz, but still...

It drives me nuts that in an otherwise pretty good sounding room, when I walk into the middle of my control room a 40 hz test tone almost completely disappears.

And by the way Joshua (Kittonian), you should tell your friends at Primacoustic to try to maximize their website search data somehow. When I type Primacoustic into Google the first thing that pops up is Real Traps!

-R

[kittonian]

Originally Posted by RKrizman

And by the way Joshua (Kittonian), you should tell your friends at Primacoustic to try to maximize their website search data somehow. When I type Primacoustic into Google the first thing that pops up is Real Traps!
-R

That's actually pretty funny and kudos to Ethan for great SEO.

Regardless of posted specs, I can honestly say that I've been blown away by the flatness of my room after adding in the Primacoustic stuff.

[RKrizman]

Originally Posted by kittonian

That's actually pretty funny and kudos to Ethan for great SEO.

Regardless of posted specs, I can honestly say that I've been blown away by the flatness of my room after adding in the Primacoustic stuff.

Every room is different of course. Like the OP I'm looking for something that will target the ultralows, which quite understandably no shippable commercial product seems to do, although the GIK seems to come closest.

I don't think you can just ignore the published specs. The product ain't gonna do some magic thing that isn't accounted for by those readings.

-R

[RKrizman]

Actually I should correct myself. The OP is looking for trapping in the 40 - 150 hz range. The huge amount of absorption at 80 hz pretty much puts the GIK Monster Trap right in the middle of that.

They're pretty cheap too. (I haven't tried them so this is no endorsement).

-R

[kittonian]

I wasn't saying the published specs should be completely ignored but after hearing about how those tests are performed and the variances in the outcomes, they should be taken with a grain of salt.

I know Primacoustic for example used a very different test facility (sorry can't remember the name offhand) that is notorious for extremely accurate results. Peter (owner of Primacoustic) noted that the test engineers were quite taken aback when they saw the results of his products (in a good way) and even he was surprised at how well they performed.