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Confused by bass trapping treatment

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Confused by bass trapping treatment

Postby thechrew » Fri Feb 10, 2012 9:55 pm

Hello everybody.

I have a bit confused over some bass trapping issues in my room. Basically, I have realised that frequencies around 132Hz resonate very loudly in my room. I have been doing some sine wave sweeps and the volume stays pretty constant until around 132Hz where it suddenly increases by a tremendous amount in volume and pass 140Hz the volume goes down again. Initially, I found out that this problem was happening only at the listening sweet spot from my nearfields. When I stood up and walked to the back of my room, the sine sweep was pretty constant throughout the frequencies again. I then took my nearfields and pointed them at random directions but the same 'sweet spot' resonance continued.

I have been taking a look at some of the bass trapping options. I live in a flat so any DIY job with Rockwool is pretty hard and going to be out of reach for me and I am not entirely convinced that the Universal Acoustic or Auralex corner bass traps will help me much. I have seen some Rockwool bass traps selling on eBay too. Its not exactly a small amount of money to spend so before I plonked that money, I just wanted to ask around and see if anyone else have had experiences similar to mine and how you solved it.
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Re: Confused by bass trapping treatment

Postby Hugh Robjohns » Sat Feb 11, 2012 3:23 pm

Bass trapping is the solution, and a DIY rockwoold-based traps across the vertical corners of the room tends to be the most cost-effective. Foam bass traps are rarely large enough to make much difference.

I'd recommend building some simple free-standing frames of wood, fill it with rockwool, and wrap it in a breathable fabric (the black weed prevention sheeting sold in garden centres works surprisingly well and is very cheap.

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Re: Confused by bass trapping treatment

Postby thechrew » Sat Feb 11, 2012 7:55 pm

Thanks for your reply Hugh.

I was looking at some ready made structures similar to your description like this http://www.ebay.co.uk/itm/Bass-Traps-Acoustic-Treatment-/300650712812?pt=LH_DefaultDomain_3&hash=item46002dceec#ht_1020wt_1189 on eBay but for that price, I suspect I can get a lot more if I do some DIY. I guess I will have to work around the space restrictions in my flat and try making some bass traps.
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Re: Confused by bass trapping treatment

Postby Mike Stranks » Sat Feb 11, 2012 11:33 pm

If you really want ready-made have a look at Hannibal Acoustics website. Cheaper and bigger!
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Re: Confused by bass trapping treatment

Postby Glenn Kuras » Mon Feb 13, 2012 2:07 pm

Hugh Robjohns wrote:Bass trapping is the solution, and a DIY rockwoold-based traps across the vertical corners of the room tends to be the most cost-effective. Foam bass traps are rarely large enough to make much difference.



hugh

Hugh you might enjoy this report I just did.
http://www.gikacoustics.com/news_020912.html
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Re: Confused by bass trapping treatment

Postby thechrew » Mon Feb 13, 2012 11:02 pm

Mike Stranks wrote:If you really want ready-made have a look at Hannibal Acoustics website. Cheaper and bigger!

Great! I'll check it out immediately
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Re: Confused by bass trapping treatment

Postby Hugh Robjohns » Tue Feb 14, 2012 10:07 am

Glenn Kuras wrote:Hugh you might enjoy this report I just did.

Nice -- and exactly what my own experience had told me. Foam traps generally have more effect at MF and HF and relatively little at the real bottom end.

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Re: Confused by bass trapping treatment

Postby Chump » Tue Feb 14, 2012 11:02 am

I'm in a similar situation - about to build some "Super Chunk" traps (basically what Hugh describes above). However... from the various reponse plots I've seen on the web, it doesn't look as though bass trapping actually makes a huge amount of difference - the response plots still have the fairly drastic peaks and troughs below about 200 Hz.

Does this mean that for a smallish room in a house, there's no getting around the fact that the room response will always exhibit pretty drastc (i.e. 10 - 15 dB) peaks / troughs, and even with bass traps from floor to ceiling in all four corners, these aren't going to go away?

Or does the situation with bass trapping improve more significantly than the plots suggest?
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Re: Confused by bass trapping treatment

Postby Richie Royale » Tue Feb 14, 2012 11:46 am

I made up some chunks like these

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

But as I live in rented accomodation, I bagged up about 50cm blocks at a time and filled the corners behind my monitors from floor to ceiling, securing them with nails. This means I can take them out when I move (hopefully somewhere permanent).

I also made some framed traps for other parts of the room and whilst I'm not finished working on the room, it is definitely better than it was.
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Re: Confused by bass trapping treatment

Postby Hugh Robjohns » Tue Feb 14, 2012 11:47 am

It's all about wavelengths, innit? To soak up those really low frequencies the bass traps need to be physically deep because the wavelengths involved are huge. That's extrenely difficult to do in a small room because by the time the trap is deep enough, you can't open the door or put any gear in the room!

Thankfully, there are other, less massive, ways to deal with deep LF problems, but that involves accurate measurements of the problem frequencies and then calculating the appropriate parameters and positions for building specifically tuned traps.

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Re: Confused by bass trapping treatment

Postby thechrew » Wed Feb 15, 2012 1:57 am

Are such Rockwool stuff suitable for a studio that also functions as a bedroom? I am just a little bit concerned because having a studio in the bedroom means that I will probably be spending a massive amount of time in there and the last thing I want is to be breathing nasty things in constantly.
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Re: Confused by bass trapping treatment

Postby Richie Royale » Wed Feb 15, 2012 9:49 am

Rockwool is a mild irritant, but you can stop loose fibres by giving it a light spraying with watered down PVA glue and allow it to dry, then covering it with breathable fabric. The traps aren't going to be disturbed once in position, so it is nothing to worry about.
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Re: Confused by bass trapping treatment

Postby Martin Walker » Wed Feb 15, 2012 11:21 pm

This ploy is used by lots of acousticians to damp down fibre release, and I've treated my own bass traps in the same way before covering following this advice

I typically work in my studio at least eight hours a day and have done so for many years now without any sensitivity or breathing problems.


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Re: Confused by bass trapping treatment

Postby thechrew » Thu Feb 16, 2012 11:38 pm

Quick question- I know bass trapping should always be focused on the corners but if my room has a few many corners i.e. L-shaped room or pillars in the corner or ceiling to floor wardrobe with some corners more shallow than others, the treatment of which room corner would be most efficient or should all corners be treated?
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Re: Confused by bass trapping treatment

Postby Scramble » Fri Feb 17, 2012 12:01 am

Chrew and Chump: If you want a cheap preview then buy a heap of thick synthetic pillows from a cut-price bed linen store. Stuff as many as you can in to all the corners and other areas where the floor meets the wall (you can also use any spare duvets and blankets, etc. that you have).

You should hear an immediate improvement in the bass, with greatly reduced resonances. I did in my room when I did this -- initially I found that the A on a bass would be ridiculously loud and hang around forever, but a heap of pillows showed me that this problem could be solved. You can then work out (in a very rough-and-ready way, mind you) which areas are causing the problems (it'll probably be most or all of them).

Rockwool works much better, and takes up a lot less space than pillows. Plus it's much lighter so it's easier to hang it up (often the upper corners are troublesome as well). So get some Rockwool to do it properly. But if you're sceptical then the pillows should hopefully convince you that you will tame those rogue frequencies! But if I was you I'd just buy the Rockwool now and get on with it. The thicker the better.
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Re: Confused by bass trapping treatment

Postby Martin Walker » Fri Feb 17, 2012 12:53 am

thechrew wrote:Quick question- I know bass trapping should always be focused on the corners but if my room has a few many corners i.e. L-shaped room or pillars in the corner or ceiling to floor wardrobe with some corners more shallow than others, the treatment of which room corner would be most efficient or should all corners be treated?

In my experience across a few project studios, the most effective place to place the first two corner traps is invariably the front vertical corners, followed by the rear vertical corners (although if any of these corners is close to a door the trap may not be as effective, since a standard internal door will let a lot of the bass out all by itself

Following that it tends to be down to the individual room and how its modes fall - in mine the next best positions for bass traps were mid front and back walls, and the front wall/floor boundary. Yours may be different, and this is why it's worth spending a little time with an acoustic utility like the freeware Room EQ Wizard so you can see the improvement as each trap is moved around.


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Re: Confused by bass trapping treatment

Postby thechrew » Fri Feb 17, 2012 1:56 am

Martin Walker wrote:
thechrew wrote:Quick question- I know bass trapping should always be focused on the corners but if my room has a few many corners i.e. L-shaped room or pillars in the corner or ceiling to floor wardrobe with some corners more shallow than others, the treatment of which room corner would be most efficient or should all corners be treated?

In my experience across a few project studios, the most effective place to place the first two corner traps is invariably the front vertical corners, followed by the rear vertical corners (although if any of these corners is close to a door the trap may not be as effective, since a standard internal door will let a lot of the bass out all by itself

Following that it tends to be down to the individual room and how its modes fall - in mine the next best positions for bass traps were mid front and back walls, and the front wall/floor boundary. Yours may be different, and this is why it's worth spending a little time with an acoustic utility like the freeware Room EQ Wizard so you can see the improvement as each trap is moved around.


Martin

Yup, I have just downloaded the software you mentioned above and so far my guesstimation about the problematic frequencies have been correct.

Having said that, I know this has been mentioned in some older posts but I am finding it difficult to source for online places to buy small quantities of Rockwool for delivery to my home without paying some over the top delivery prices. Not owning a car sure is troublesome. Has anybody discovered any new online Rockwool sources since? I have decided to consider strongly the DIY option because I had an email conversation with Steve from Hannibal Acoustics in which we concluded that for my current situation and budget, some DIY bass traps would be way more cost effective than ready sources.
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