Building proper bass traps

[sploo]

Vaughan,

When I treated my room (using raw rockwool panels, wrapped in wadding) I took a few measurements with 4" thick panels in the corners, and again after making the corner panels pretty much solid (i.e. all the way into the corner).

The difference wasn't great, and I recall reading some advice indicating it's better to have more coverage (i.e. more traps) than to have a few really thick ones (can't remember where I read it, so I can't back that up).

Given the high cost of shipping ready made panels from the US, I'd advise getting rockwool locally, and wrapping it in cotton batting/wadding or those Ready Acoustics bags.

I have no links to Ready Acoustics, and I've not seen their products, but given the time it takes to wrap the panels yourself, the prices on their site look pretty good to me for a ready made bag.

Do try to get a dense panel for the corner bass traps (i.e. 100kg/m3) and a lower density for high frequency panels at the first reflection points (i.e. 45kg/m3). I believe the absorption characteristics of the respective densities are better for low/mid-high respectively, and it certainly worked for me.

 

[Scott R. Foster]

Sploo:

We came up with some absorber design concepts and did some testing [Savant, as he is known here, did all the lab work] and got results consistent with your experience using 100 mm panels versus full wedges like the SuperChunk:

http://forum.studiotips.com/viewtopic.php?t=535

A 24" wide 4" / 100 mm thick panel across the diagonal of the corner is +/- 20% less effective than a SuperChunk [full wedge] with a 34" face [that's a big chunk - AFAIK only Auralex makes a factory-made wedge this large] - but the panel uses only 66% less mineral wool - so for a given amount of wool [or foam], you can have three panels or one SuperChunk.

You'll get more Sabines [absorption] with the three panels. You can see a comparison graph here:

http://forum.studiotips.com/viewtopic.php?t=536

 

[Vaughan Odendaa]

Is rockwool like fiberglass ? I've read through Everast like six times now. I'm basically a pro now.

I definitely like the idea of the bags. Excellent idea. I must say, I'm interested. Scott, you say that one can buy bags for 6" thick. Is that the upper limit ?

Sploo, would it not be a good idea to use 4" thick panels for the first reflection points ? Wouldn't the additional bass trapping be beneficial ? Unless I'm wrong. Please correct me if I'm wrong.

Are there any pictures of clients who have used just the bags with fiberglass ? Scott, if the panels that I've seen from Readytraps look as good as the bag and DIY, then I'm really excited. Not that looks are everything but well, you know.

Thanks. BTW, I contacted Owen Corning South Africa. Apparently they don't know about 703 or 705. They do know about rigid fiberglass and that there are different densities. I find that strange.

--Sincerely,

 

[Scott R. Foster]

Is rockwool like fiberglass ? I've read through Everast like six times now. I'm basically a pro now.

Yeah... and no. Both are mineral wool - one is made from sand and one from rock - heated, drawn into strands, and formed into a panels leaving millions of tiny holes. With Fiberglass look for panels in the 3 lbs. pcf range [48 kg/m3], in rockwool about half again more - though its is common to use fiberglass up to 6 lbs. pcf, and rockwool up to about 8 lbs. pcf.

Denser boards are more expensive [generally] but a bit stiffer, and so easier to work with [especially with rockwool - which is pretty floppy compared to fiberglass panels].

Anything in the above class of materials will work - here is a helpful resource of materials from around the world that illustrates the properties of the materials described above, and could help you identify your best locally available option.

http://www.bobgolds.com/AbsorptionCoefficients.htm

I definitely like the idea of the bags. Excellent idea. I must say, I'm interested. Scott, you say that one can buy bags for 6" thick. Is that the upper limit ?

No... but you get into a diminishing return in a several ways... you get more efficiency having another panel as opposed to increasing thickness above 4".

We offer 6" panels for situations where there isn't room for more panels, and you need each panel to do more... but the inefficiencies rise as panels get thicker. Also you start taking up a lot of room with a panel 6" thick - so before going thicker, If I wanted to get a 6" panel to do even more, I would look to back fill the gap behind the panel.

Are there any pictures of clients who have used just the bags with fiberglass ? Scott, if the panels that I've seen from Readytraps look as good as the bag and DIY, then I'm really excited. Not that looks are everything but well, you know.

Never underestimate the importance of looking cool.

http://www.soundonsound.com/forum/showflat.php?Cat=&Number=373244&page=1&view=collapsed&sb=5&o=&fpart=1#373244

Thanks. BTW, I contacted Owen Corning South Africa. Apparently they don't know about 703 or 705. They do know about rigid fiberglass and that there are different densities. I find that strange.

Maybe email him this pdf or the link and ask him what he has that is equivilent to plain 703:

http://www.owenscorning.com/comminsul/documents/Fiberglas700Series.pdf

Also look to your other local fiberglass and rockwool options - shop for price and material class, not brand name. More on mineral wool selection for broadband applications here:

http://forum.studiotips.com/viewtopic.php?t=48

 

[Audioholics]

Scott, we'll bill you for all the free advertising later. lol

 

[Vaughan Odendaa]

Heheh.

--Sincerely,

 

[Scott R. Foster]

Scott, we'll bill you for all the free advertising later. lol

Fair enough... can pay my bill in basstraps?

 

[Vaughan Odendaa]

Scott, would it be a good idea to use broad band bass traps for the first reflection points as well ? I need as much trapping as I can get, correct ?

What would I gain by using 2" thick panels for the first reflection points rather than 4" ? I keep hearing from some people that you need less density to absorb the mids and highs but my logic is telling me that I could kill two stones with one thick panel.

--Sincerely,

 

[Glenn Kuras]

Scott, would it be a good idea to use broad band bass traps for the first reflection points as well ? I need as much trapping as I can get, correct ?

What would I gain by using 2" thick panels for the first reflection points rather than 4" ? I keep hearing from some people that you need less density to absorb the mids and highs but my logic is telling me that I could kill two stones with one thick panel.

--Sincerely,

You are not going to kill 2 birds with one stone, but using 4" panels will help "A LITTLE" in the bass range when on the first reflections. But really you need to look at cost vs what you are getting out of the panel and go from there. Really it is best to focus bass trapping in the corners and if you have enough there then 2" will work fine for the first reflections.

Glenn

 

[Vaughan Odendaa]

I don't understand why using 4" thick panels won't help much. If I space the panel from the wall by 1.5-2", that should soak up some bass as well as providing me with first reflection control.

If the difference in cost between the high/mid frequency absorber and bass trap is minimal, then my mind is telling me that that would be the most logical choice because I could gain even more low frequency absorbsion as well as treat slap echo.

What are your thoughts ?

--Sincerely,

 

[Glenn Kuras]

I don't understand why using 4" thick panels won't help much. If I space the panel from the wall by 1.5-2", that should soak up some bass as well as providing me with first reflection control.

If the difference in cost between the high/mid frequency absorber and bass trap is minimal, then my mind is telling me that that would be the most logical choice because I could gain even more low frequency absorbsion as well as treat slap echo.

What are your thoughts ?

--Sincerely,

Yes if you have the space and the cost is close to each other then you really have nothing to loss. My point was more about people NOT treating the corners thinking they can just use 4" on the reflections and that should be enough. OK?

 

[Scott R. Foster]

What are your thoughts ?

I think you're right... but no surprise there - you did read the "Master Handbook" six times.

Though you can get a bit more LF performance if you make that gap a bit larger - try a 4" or larger gap instead of 1.5". For an illustration of the concept take a look at myfpie's site:

http://www.gikacoustics.com/absorption.html

[Note to Clint - put this one on Glenn's bill ]

These 4" thick panels have a 1.5" frame and are mounted 5" from the wall in stands - I read that to mean the mineral fiber is gapped 6.5" off the wall. Note that while the LF performance is diminished from a corner mount - there is still some work getting done [8 panels = 40 Sabines at 100 Hz] - not too shabby.

Now compare that to the corner mounted performance of the same panel:

http://www.gikacoustics.com/docs/CornerMount.pdf

118 Sabines for 8 panels at 100 Hz.

This is typical of what you might expect from similarly mounted 4" mineral fiber panel chosen from the class of materials discussed above.

So - bottomline - a series of ceiling and wall mounted 4" panels with a +/- 4" gap will you get you a non-trivial amount of absorption at 100 Hz and below. But, as myfpie correctly explains, it aint a substitute for corner mounted bass trapping.

However, as you have pointed out, if more LF absorption would be beneficial [and this is typically the case in home theaters and control rooms], then the 4" panel is a useful tool even in early reflection control locations [away from the corners]. Moreover, as you have surmised from shopping, the cost differential between 2" and 4" units is trivial - even less difference [in money out of pocket] if you build your own panels from scratch.

So, in typical rooms, for typical applications, you should do it - use all 4" panels - skip the thin stuff. The only time it makes sense to use thin stuff is when you already have all the low frequency control you could want [not typical for normal sized rooms - with typical treatment methods].

If you want to model some absorber profiles for given densities, panel thicknesses, and gaps and get a more in depth view of some of the maths and theory behind all this stuff - check out this spiffy calculator and the related discussion:

http://forum.studiotips.com/viewtopic.php?t=1583

just remember, your calculations are models - not actual results - in room measurements trump everything.

 

[HiFi Jake]

Scott:

I'm bouncing all over the place on business these days, so haven't had much time to stop in and I'm just seeing this now.

If that is what Jake is saying, he is wrong.

In fact the ratio works in the other direction - per the manufacturers' published specs the difference is approximately 1.5 to 1 in favor of the 4" thick RT424 [primarily becaue a Mini-trap is only 3" thick].

Of course I'm not saying that 1 Minitrap will absorb more bass than 3 Ready Traps. But my friend replaced his traps with exactly the same amount of Minitraps, and the bass was tighter and the overall sound was better. That's what my ears tell me, and that's all I'm saying. I can see how it would make more sense for Vaughn to either DIY or buy your bags, because I can imagine shipping to SA would be a serious chunk of change.

But your graph showing 12 of your traps being so close in performance to 18 Minitraps doesn't really seem right either. It certainly doesn't square with the differences I heard. I also saw your argument with Ethan about this on another forum, and Ethan explained to you that you could not ethically compare test results from two different labs, especially for low frequencies. You got pretty nasty about it as I recall. I remember Ethan saying that even the people who certify those labs say that this is the case. And he posted a graph that showed the range of difference. I don't know the science behind it, but if that's the case it seems a little unethical for you to be making that kind of comparison in selling your products.

I asked Scott over at Realtraps about this after I bought a few Minitraps from them, because already I had some GIK traps (which I ended up replacing with some Mondotraps). I liked the look of the Realtraps much better, and I really liked what they did in my friend's room, but I was also somewhat concerned because I was comparing the lab data from both companies. He was actually pretty honest with me about it. He said that it's entirely possible that the GIK traps could absorb more at certain frequencies, but that there wasn't any way he could ethically make a comparison based on that data, because of the differences between labs. He said that all of the products that were listed in the comparison charts on the Realtraps site were all tested in the same lab. He said that they had not had a chance to take any GIK traps into the lab for comparison yet, so he didn't think it was ethical or made any sense to rely entirely on comparing the two sets of data or to dismiss them entirely. I thought that was fair.

I didn't get a chance to compare the GIK traps with the Realtraps in the same way as I did with my friend's Ready traps, because I didn't have the same amount in the same room to compare them. But from what I could tell the Realtraps were at least as effective or better, and the Realtraps look a lot nicer, which was important to my wife and I. Plus I got a lot better help from the Realtraps guys than from GIK.

Jake:

But seriously, what's your buddies name? I'd like to contact him to discuss the matter. We have sold thousands of Ready Traps and have never gotten a return from anyone who disliked the looked. Nor has anyone ever reported an inability to assemble panels using our Ready Bags. If this "buddy" of yours actually had the experience you describe, we never heard from him, and I would like to.

I can mention it to him next time I see him, but I sorta doubt he'll want to bother with it. It's a little too late now anyway, because as I said he tossed them after he got the Realtraps. I know for a fact that he did contact you guys. I don't know if he talked to you or someone else there. He said you guys wanted to send him some more bags for free. LOL. We had a good laugh over that one. He said that was about as useful to him as a broken tricycle. Hehe. He's a funny guy.

But I think he didn't really feel like putting up a fight over it. It wasn't as like they didn't work or something. They certainly improved the sound in his room a great deal. But his wife hated the look of them, and he didn't love the look of them either, so out they went. In the end it was either the Realtraps or live without acoustic treatment. Sometimes if you buy cheap, you end up buying twice, I guess. That's not going to be the case for everybody I'm sure. And if you haven't had the chance to compare with anything else, you're still going to be pretty happy about how much improvement the Ready Traps or the GIK traps will make in the sound of your room.

 

[bpape]

Jake.

I'll apologize if you feel you didn't get the help you needed from us. We try very hard to work with each customer to figure out what the best solution is for their particular room and budget. I regularly work with our customers, sometimes to the extent of dozens of emails and phone calls back and forth to answer any and all questions and come up with the best solution.

Ethan's product is very nice looking indeed. We simply don't choose to put that much money into things that don't affect performance so they're accessible to more people. I also know Ethan and Scott at Real Traps and appreciate their honesty with regard to testing and comparisons outside of spec ranges and continuity of labs, sample placements, etc.

The bottom line is that you've treated your room and are happy with the results.

Bryan

 

[Scott R. Foster]

Hi Jake:

What's your buddy's name?

Thanks,

 

[Vaughan Odendaa]

Jake, is it possible that the bags were not stuffed correctly as per the tutorial on the readytrap site which would explain the ugly look that your friend mentioned ? Just asking.

I wish that there were more pictures of Readytraps because I googled and couldn't find anything at all, besides the pictures on the Readytrap website. Are there any threads that discuss Readytrap's compared to other acoustical solutions ?

So far so good. And to think that I was going to bother to make the panels and frame them. Yeah right. The DIY bags just make so much sense.

--Sincerely,

 

[Vaughan Odendaa]

Shipping of Readytrap's to my location is not cheap. Living in South Africa definitely has it's disadvantages. Shipping alone for a box of three panels is a couple hundred dollars.

Ouch. Then again, that's nothing. Having an SVS PB10 ISD subwoofer shipped to my location cost more than the subwoofer itself ! Unbelievable.

--Sincerely,

 

[HiFi Jake]

Thanks Bryan. Not a big deal. I didn't work with you though. Glenn seems like a nice guy and he was definitely helpful, but I just felt he wasn't able to articulate some things to me as well as the Realtraps guys were. And again your stuff did improve the sound in the room. I don't really mean to talk down your products and I'm sure you guys know what your doing.

I am just so happy with the Realtraps, and I was really impressed with the help I got from Scott Veenstra over there. He really asked a lot of good questions and took a lot of care in answering my questions and coming up with ideas. The Realtraps are a more profesional product and it stands to reason they cost more. They have a more polished look and they seem to be built to last a long time. But it is good you guys offer something a little more accessible too.

Scott:

I'm going to respect my friend's privacy and leave it up to him to decide if he wants to contact you. As I said, I'll certainly let him know you'd like to hear from him. I probably won't see him until sometime after New Years. But it's gotta be his call. I'm sure you can understand.

We probably didn't do the greatest job putting them together. A few of them got a bit scrunchy around the corners. Not sure what we were thinking really. Money isn't really much of an issue for him. Neither of us are really much of a DIY person, but it did look like a relatively easy thing to do from the instructions on your site. Hehe. When his wife first came in and saw them, she just smiled sweetly and said "Yes, it sounds very nice honey. But I'm not having those futons on my walls."

As Bryan said, the bottom line for both of us is that we've treated our rooms and we're happy with the results. And even more important, our wives are happy.

 

[Scott R. Foster]

Hi Jake:

I certainly wouldn't want you to invade anyone's privacy... but if I understand your story, then this indvidual is one of our customers. As such, I don't see how privacy could be an issue, as we already have the person's name, home address, email address, phone number, etcetera on file. You would simply be passing along the fact that our products didn't satisfy.

If your friend spent hundred's of dollars with us I can't imagine why he wouldn't want his money back.

Can you?

I trust you understand that I am merely seeking to get to the bottom of your rather odd story about an unhappy customer. We have never had an experience such as you describe - so the matter is of some interest to me.

Thanks,

 

[Scott R. Foster]

snip
I wish that there were more pictures of Readytraps because I googled and couldn't find anything at all, besides the pictures on the Readytrap website. Are there any threads that discuss Readytrap's compared to other acoustical solutions ?

Vaughan:

I can point you to any number of such - some with user pics - but I don;t want to give the admins here the heebeejeebees about me running ads in a discussion forum, so if you would, either PM me or contact me through our web site, or start a thread here:

http://forum.studiotips.com/

Thanks,