Another Bass Traps thread

[elser]

I know this has been done here before. And I've scoured the web trying to learn as much as I can about the subject, but I still find it all a bit bewildering so I'm hoping that if I put up the particulars of my recording space, maybe the geniuses around here can help me put together a plan for putting bass traps in my studio.

Here are the details:

The room measures 11 x 13.5 x 8. The walls are drywall and it sits on a standard foundation with a crawlspace of about 3 feet high under the house. It has a wood floor but I have a throw rug on it basically for warmth, it's cold here in the winter, but the rug can go if that would be better. I have one box of Auralex acoustic tiles placed around the room in spots that seem to me would cause problematic reflections.

I have two Mackie HR824s for monitoring and no sub.

I have significant bumps when running a sine wave test pattern between 33 and 44 hz and again between 129 and 139 hz.

I couldn't figure out how to upload pics here so I put them in my dropbox if anyone wants to take a look at it.

https://www.dropbox.com/sh/sd6afr9ynspv ... 7XHoa?dl=0

Thanks again for all yall's help!
Jon

[Len911]

Jon, this is what I have, and they are portable, meaning, you can either put them in the corners, move them up or down, or surround your subject in the middle of the room. So very versatile.
http://www.auralex.com/product/stand-mounted-lenrds/

I believe they say that bass buildup is most problematic in the corners. You have a fairly small recording space. If you were to record say a bass amp, it might work better to place your mic and amp in the middle of the room surrounded by Lenard bass traps, so you get the bass, and what sound leaks out and bounces off the walls and heading back to the middle will be attenuated again by the lenards in the middle. It might work better than just having permanent bass traps mounted in the corners. You could move them back to the corners when done recording. You could also use them when monitoring your mixes by placing them around the perimeter of your chair and speakers to minimize room reflections as well. Same thing when recording a vocalist. My only complaint is that I wish they came with a round base for the stand instead of 3 feet that stick out and sometimes get entangled,lol!

[fuzzbox]

Hi Jon,
Yes, I agree, this can be confusing. It is the science part of the art of making music, I guess. I'm not an expert but I have studied this for sometime to get my set up working better than it was. Because I master with the same set up I have to beware when applying EQ changes.

You can use a tape measure and a mirror to help you place your Auralex acoustic tiles accurately. As the higher frequencies tend to travel in straight lines.

Essentially then, you need to compensate for those frequency bumps. However, those frequency bumps are a factor of your current room. So that you get a flat frequency response. This means all of the contents and the positions of the contents of the room play apart in the frequency response. Move something and you will get a different reading. Whether that is going to alter your final mix is another matter but technically it will give you a different reading.

Anyway, to compensate you can do this by reducing those frequencies on your master buss with an EQ. How much? It depends on how much of a bump you have. You didn't say what the centre frequecy was. That would give an indication of the wavelength and hence what frequencies need to be compensated for. Interestingly, you can workout what the wavelength of your room. For example, your room is 13.5 feet (I assume it is feet and not metres) from the monitor (which should be off the wall, say 1 foot) to the far wall will give you a frequency of approx 110 Hz. That mean 110 Hz will respond without any interference known as standing waves which can manifest itself as boominess.

Bass is difficult frequency because it is less directional than higher frequencies and hence bounce around the room more that higher frequencies. That is why it needs to be absorbed or trapped to reduce or stop it bouncing around the room giving you the boominess (resonance) that you can hear. Your speakers should be placed facing the longest part of your room and slightly away from the wall. (I couldn't view your diagram as the url was just an empty web page).

Anyway enough of the science.
If you already know about this, I apologise.

My room is much smaller that yours and so is more problematic. So, this is what I ended up doing for my room:

I use reference tracks to A/B your mix regularly.
I use calibrated headphones.
I fitted two bass traps.
I also use a sub (but you don't have to).

My calibrated headphones have a flat response thereby giving me the ideal room. Yep its true, it really does (well... as close as possible). They give really good reliable results. The company already supply calibrated software for a large range of well know makes. Here is their url http://sonarworks.com/headphones/overview/ if you're interested and see if your headphones are already on their list. If not they can, calibrate your headphones.
BTW it doesn't matter which corners you use for your bass traps.

If you didn't already know, the lowest note on a bass guitar is at around 41 Hz so one of your bumps is in that region, so you will get boominess on the low E of the bass for example. (Again if you already know this, apologies. )

Will it affect you mix decisions? More than likely.

It is a complicated issue to resolve and may take several attempts. I would start by using reference tracks, then if you can afford to use/get the calibrated headphones, then the bass traps!

Good luck!

[lesmac]

Most people who install corner bass traps say they notice an improvement in their monitoring [from what I've seen on the web]. The addition of bass traps will absorb a BIT of the build up of bass energy. That in effect raises the threshold of your room meaning you can get a bit more volume/level before the bass room modes take effect.

Put the traps in the corners, the more the merrier. It will help if you sit them out from the walls a bit to lower the frequencies they will be effective to. This is for velocity traps which are made out of rock wool or fibreglass. They are usually the cheapest to make or buy and the easiest to implement rather than pressure traps.

If you can experiment a bit moving your listening position AND one speaker say four to six inches at a time and running your test program that may help to find a spot that is more suitable. Some people play full range material they are familiar with to do this instead of test software. Its weird how room modes and standing waves work, put your head in a different spot in the room and you hear something completely different. There is a rule I think it's 38%. Basically that is the no brainer spot to monitor from length wise in your room.

In short I'd say installing traps is a good idea. Moving your monitoring setup incrementally and measuring is time well spent. Finding out how loud you can monitor before bass frequencies build up is good to know. Compensative EQ is something I haven't looked into yet but will most likely do. Do a bit to go some way towards maximising your rooms potential but don't let it do your head in.

[elser]

Thanks for all the replies. This where I'm at. First off, I'm thinking home made corner bass traps. Primarily for saving on the expense and I don't see a need for moveable traps since I don't record with mics in this room. Any live recording is done in another room in the house. I have limited floor space so getting the traps as close to the wall as possible is preferable. I saw on gearslutz a guy's solution where he just built floor to ceiling corner traps using Rockwool triangles. He devised a wire frame using something like bailing wire to hold them in place and then stacked the triangles on top of one another and then covered each stack on the front side with some type of black cloth. Does this sound effective? It seems to me I could also then use the same technique to put traps in the ceiling to wall corners.

[fuzzbox]

Yep! it's an effective start.
Corner traps saves space and are quick to put in place and is something that is proven to work.

[lesmac]

Just check on the density of the rock wool for those wedges. It might be something like 14kg3 or more. There is an optimum number. Rockwool is way more user friendly than fibreglass so good choice. The good thing about the "super chunks" is that you don't need the density that the Ethan Winer type traps require 96kg3 I think. Definitely if your'e up for it put them on the wall/ceiling corners. I have a wedge of fibreglass wrapped in geo-fabric of that lower density that comes out probably 1.5 meters from the ceiling corner in front of my monitoring position.
I don't know if you picked up the info on why the depth of the traps comes into play. Its because they are "Velocity" traps and the frequencies are attenuated as they travel through the trap, both ways or in all directions. They work MOST effectively at 1/3 of a frequency's wavelength. 100hz being 3m long so the trap is at its optimum 1m out from the boundary. They still work if you don't have the distance but its interesting to know.
I think what you are doing is way better than buying another plug in so good on you, I'm sure you'll reap the benefits.

[fuzzbox]

One more thing... I was cleaning out my studio and I came across a drawing of my mix room. Then I remembered I had it analysed by these guys http://www.vicoustic.com/page/project-request.
For a few dollars you can have your diagram scrutinised by their project team and given examples of what and where to put your acoustic treatments. Of course it may be too late but I thought it may help you. The thing is, you don't have to use their products but you can substitute for others.

[mojobone]

You know where your bumps are, do you know your dips? RT? A sweep with a dB meter gives you two axes; frequency and level, but a waterfall plot adds decay-frequency and level, over time. Shooting the room with pink noise and an omni condenser would give you a much more detailed read on what your room is doing, but based on your room's dimensions, it'll be tough to tame.

Judging by your pics, the space has bigger problems than just where to put bass traps. For starters, even if you install string mutes in the instruments on the third wall, their cavities are gonna ring/resonate, which may or may not be a thing you want, but usually, not. OTOH you could just use the software between your ears to compensate, using reference material that you've heard on multiple systems.

You absolutely can treat the deficiencies of the space, and if left untreated, it'll likely sound boxy when you're in it and mixes made there may sound tubby elsewhere; it's in the nature of small rooms. Without standing in the room and talking, my impression is that your speakers and listening position could be better placed; I am not a fan of placing speakers in front of glass, and I suspect your speakers would work better facing the other way. Trouble is, they'd be firing towards the glass which can sound not-nice. The only wall that can be treated has a big diffuser in front of it; something you'd might maybe normally want behind the mix position. The bookshelf/wall unit would look pretty weird in front of the window, but probably function better acoustically. In theory, that is, because materials and construction also come into play.

Keep in mind, none of what I'm saying should trump what you're hearing; I haven't stood in your room and listened. Listen, measure, try, repeat. Incremental, small improvements add up, so it's worth revisiting the subject, from time to time, and hey, they're still coming out with useful new products.

*edit: Modecalc can give you some frequency info based on room dimensions, but dimensions are one thing and materials can be quite another.

[lesmac]

Hmmm, yeah I just looked at your pics.
First up I'd try rearranging the room, most cost effective action.
Keep your head out of the centre of the room cause thats a bass null.
It may be that a diagonal setup is more suitable. Imagine monitoring and speaker positions and then try and visualise the path audio takes as it travels from the speakers around the room and back to your ears. If you can get the reflections to bounce round and take a long route back to your ears that's good. If you can also place absorption at the first reflexion points, thats good too.
HTH