Where to set up the monitors?

pure.fusion

New member
Hi all,

My "studio" if you can all it that is moving to the mext step.

I have a pair of KRK Rokit 6 that I bought as reference to record and mix. For the the moment though, they are on a shelf up against the wall - obviously totally useless for the purpose they were built for 'cause there is a boom in the bass frequences. I've been using headphones to mix which had led to other problems thatI've posted at this forum.

So now, I get to place them anywhere I want in the room I've got. The room is rectangular (of course), has double brick walls and a door on each of it's longer sides and measures roughly 5m x 3.5m (16.5' x 11.5'). One door is in the centre of the wall, the other and the end.

Where do I get the best results for these speakers? Are there some simple rules of thumb?

I understand the principals of near field monitoring and where my monitors need to sit with reference to the listener - height, distance apart, distance from the listener.

Cheers,
FM
 
For a 5 meter room - place yourself (operator) at 190cm from the front wall. Put the speakers so that the front of the speakers are 50cm from the same front wall - facing the operator. Separate the speaker by 162cm center to center. This will put the left and right speaker centers 94cm from the side walls.

This is only a recommended starting point which places you at 38% of the length of the room from the front wall & your speakers form an equilateral triangle with you at one point.

Your previously mentioned 'boom in the bass frequences' is most likely modal. You must treat your room. Build or buy traps for the corners to start with.. you have 12 of them - so take your pick.. use 8 if you can. :D

To treat your side reflection points place absorption panels centered 110cm from the mix position toward the front.

Cheers,
John
 
Excellent. Thanks for your reply. It was quite raw, beginner type question and I really didn't expect anyone to bite.

Great info guys.

John, I did the math for my room (which when I actually measured 6700mm x 3850mm) and that will work well. Ethan, read the article, thanks.

Question to John: Why did you recommend "Put the speakers so that the front of the speakers are 50cm from the same front wall" ? Was 50cm just a starting point? The KRK Rokit 6's are 27cm long. So really, that puts them almost as close to the brick wall as they are now. Is it the close proximity to the wall the is making the bass boom? (Amongst other factors as discussed above).

If I move my monitors back along the equilateral triangle axis, there will be a point to where they will touch the wall. How close is too close to the wall? Or is this not a factor?

The next obvious question is what's the best (cheapest) material to use for absorption panels? Is there a home recording quick and dirty way of doing this? Or is it the costly acoustic foam I see for sale. I bet Brick would bounce sound better than plaster...

Also, Bass traps (Sorry with the questions). You said I have 12 corners? Eh?? I'm feeling a bit stupid - I only count 8 no matter how many times I re-count! Anyway, one bit at a time.

Cheers,
FM
 
Also, Bass traps (Sorry with the questions). You said I have 12 corners? Eh?? I'm feeling a bit stupid - I only count 8 no matter how many times I re-count! Anyway, one bit at a time.

The twelve "corners" you're looking for are the areas where any two walls meet each other. So, from the center of the room, you'd have two on either side of your desk, one between the wall you're facing and the ceiling, and this pattern continues around the room as you turn. I'm pretty sure the last four are corners in the traditional sense, so four around the top of the room.

I'm pretty sure those are the corners that everyone is talking about. I think everyone excludes the points where walls meet the floor.
 
Just to *bump* the thread to get a response from my previous post, I can also ask about the two types of bass traps I found.

One of them seems to be foam related...
http://www.binarydesigns.com.au/bdstore/WPCR2.html

.. and the other seems to be fibreglass panels like this
http://www.radford.edu/shelm/acoustics/bass-traps.html

One better than the other for my cheap home studio?

FM

From what I've seen, the rigid fiberglass ones are the way to go.

This company seems to be one of the best suppliers for the materials you'll need that I've seen online. You'll probably want to look for something similar closer to you, as I'm sure overseas shipping will be a killer, but this should give you a pretty good idea of what you can build on your own.
http://www.atsacoustics.com/cat--DIY-Acoustic-Materials--102.html
 
Cheers mate. Thanks for the follow up.

Yes, this post started me off reading about corners; of which I now know that some of the corners that are being referred to are actually edges. Also reading about bass traps, sound absorbing materials and a whole bunch of other stuff that got really technical.

Not that this scares me, but as an amateur, you look at all the different kinds of bass traps that people are using and building and then you wonder which ones are going to be the most effective.... and you have no idea.

Same with the first reflections. I can put up panels of acoustic tiles (http://www.jaycar.com.au/productResults.asp?keywords=acoustic&keyform=KEYWORD&SUBMIT.x=0&SUBMIT.y=0) ... or follow some other guy who uses heavy curtains that are bunched up to show an un-even surface.

Anyway, we sift through it, make a choice and suck on the result, hoping that you haven't wasted too much money in the process.

All very exciting tho.

FM
 
Question to John: Why did you recommend "Put the speakers so that the front of the speakers are 50cm from the same front wall" ? Was 50cm just a starting point?

Just a starting point given as a minimum distance... move them 25cm further from the wall and adjust the equilateral triangle. Keep the operator position the same.

The KRK Rokit 6's are 27cm long. So really, that puts them almost as close to the brick wall as they are now. Is it the close proximity to the wall the is making the bass boom? (Amongst other factors as discussed above).
Yes, that could definitely be a factor. You will need substantial trapping behind them in the vertical corners if possible.

If I move my monitors back along the equilateral triangle axis, there will be a point to where they will touch the wall. How close is too close to the wall? Or is this not a factor?
Yes it is a factor. You should move them away from the wall until you get the most even LF response on REW or Fuzzmeasure. Beware of SBIR - but sometimes you cannot practically move the speakers out of the boundary region. I do understand - So you must get the best compromise.

The next obvious question is what's the best (cheapest) material to use for absorption panels? Is there a home recording quick and dirty way of doing this? Or is it the costly acoustic foam I see for sale. I bet Brick would bounce sound better than plaster...

The best - (acoustically effective, cost-effective, etc.) would be home-made panels from OC 703 or rock wool with a density of 48kg/m3 or close. I do not recommend densities higher than 80kg/m3 as the absorption coefficients begin to go down...

Not that this scares me, but as an amateur, you look at all the different kinds of bass traps that people are using and building and then you wonder which ones are going to be the most effective.... and you have no idea.

Superchunk style corner traps are very good. Home-build membrane traps will do a little better. When making absorption panels for the walls & ceiling, remember that ideally they should be at least 100mm or 4 inches thick to be effectively broadband absorbers... with a LF cut-off determined by the thickness. - You want absorption down to where your room transitions to the wave region. - If you don't understand... I'll explain.

But, yes, rock wool or compressed fiberglass is your best bet.

Same with the first reflections. I can put up panels of acoustic tiles (http://www.jaycar.com.au/productResults.asp?keywords=acoustic&keyform=KEYWORD&SUBMIT.x=0&SUBMIT.y=0) ... or follow some other guy who uses heavy curtains that are bunched up to show an un-even surface.

Rock on with the rock wool, my friend.

Cheers,
John
 
Excellent John. Thanks for getting back.

I'll digest this, think about implementing some of it. Will take a few weeks.

But a query on one thing. You're suggesting rock wool for first reflections?

I thought Rock Wool for use in bass traps at 100mm thick - from my general reading this adds up and your advice makes sense. Are you saying I can place this at the first reflection point and it will stop mid to high frequencies bouncing as well?

Cheers,
FM
 
FM,

Rock wool 100mm thick does make a good bass trap especially if it has a membrane or it is placed in a corner - sometimes with more absorptive material behind it. But it also makes a very good absorption panel.

The quarter-wavelength (λ/4) rule dictates that a porous absorber for normal incidence must be at least a quarter-wavelength thick at the frequency of interest - this rule changes with the angle of incidence. For example, for a frequency of 1kHz, the minimum absorber thickness should be about 90mm. Lower frequencies require thicker material. So, 100mm of rock wool just about takes care of frequencies from 850Hz and up. Also note that an absorber is less effective at glancing angles and is sometimes 100% reflective at these angles. This often depends on the fabric used.

The above is only written as a theoretical example. In actual practice a 100mm thickness of glass fiber material of 48kg/m3 density has essentially perfect absorption over the 125Hz to 4kHz region. Only 4kHz is listed because the STC curve is only rated to that frequency. The absorption at higher frequencies is also near perfect. :D

Here's a handy little excel calculator for determining where to put the absorption at first reflection points. Enjoy!

Cheers,
John
 
Right, I've had read and a ponder. So let me get this straight...

If I use 100mm of rock wool (or high density insulation 48kg/m3) ay my first reflection points (say one on each side wall and one on the roof) covered in the "correct material", this would not only address the first reflections, but also help in trapping some of the bass. Then, some more bass trapping in the corners, perhaps to address some of the sub 850Hz frequencies would round off treating the room, at least for the first pass.

This would be a good start to adressing the room, yes? Then I'd maybe measure the response with a mic/software setup and try to address any issues from there?

"especially if it has a membrane" , "This often depends on the fabric used"

Material sounds quite relevant. What sort of material are we talking about?

Cheers,
FM
 
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