Help me sort my room boom

JonnyBgoode

Behold my tiny home studio, a garden office which is about 3m x 2.7m, so yeah it's a box.  

pics:

https://drive.google.com/file/d/1FsCdI26_fBnkB6VeALHmgPEWT2OcFDDi/view

https://drive.google.com/file/d/1EOMRNwFMZW-Vl7TL05tEo31FbGXKQnU4/view

I am getting bass resonance in my desk area which is really noticeable playing an electric guitar via interface>amp sim>monitors at pretty low volumes. Its making mixing with the nearfield monitors a problem too. Peak resonance is around 139-156hz (9-11th fret bottom E string is the worst, same frequency on 5th and 4ths strings is not so bad).

As you can see,  floor corners either side of desk are taken up with PC (left)  and guitars/cases (right), but the ceiling corners are bare as is the wall behind my desk/monitors. Behind me on the rear wall at the other end of the studio there's a bookcase on left side with stuff on top in the corner, some bare wall and a bare corner top right.

Suggestions for please for treating this small space and reducing bass resonance. 

Foam bass traps for the ceiling corners behind the desk and wall panels behind the speakers maybe?

Note

-I am shite at DIY and have little spare time so any homemade solutions have to be pretty easy to accomplish  not sawing/building anything

-I am not mixing/mastering stuff for any commercial purposes and so not looking to spend a bomb. 50 quid ish? Although if you think my monitors (Tannor Reveal, nearly 20 yrs old) are part of the problem I'll happily sell them and get something smaller.

Whistler

Acoustic treatment acts like an acoustic sponge to put a brake on sound bouncing around a room uncontrollably, which is what we call reverb(eration).

Acoustic foam is expensive and because of that is made thin. This means it will soak up higher frequencies but leave bass frequencies to still sound boomy. The normal material is the cheapest, lightest, fluffiest everyday mineral wool or fibreglass insulation, just like you probably have in your walls and and loft.

This is a broadband trap, 1200mm x 600mm x 150mm.



Your room will require a number of these to bring the reverb under control; possibly not quite as many as in this room where there are 41 traps in all: They cover the ceiling and all corners - wall to wall corners and wall to ceiling corners.



The back wall will have deep traps and be the main bass trap. You will need to either move your wall heater or work around it.



I see you have your monitors set up for mixing. Broadband traps on the walls (or wall and window in your case) will minimise the bouncing of sounds so that you hear the original signal from your monitors more clearly. You can see that there are gaps between the traops and the walls; that is to help them perform better (ie. to lower frequencies). Attaching a trap to a window is not possibly so a stand can be used so it sits in the right place.



You say DIY is not your thing. You can buy ready made traps from companies such as GIK Acoustics - gikacoustics.co.uk - or get a friend to help. They are simply insulation in wooden frames, covered with a breathable textile - any textile you can breathe through. In the photos I used hessian which was the cheapest option but not the prettiest.

That is the principle of controlling the boomy sound in your room. Each trap cost me under £20 to make.

Musicwolf

Forget foam, it really is of little use.

Rockwool broadbad absorbers are pretty easy to make (I managed it) and there are plenty of 'how to build' vids out there.  You need Rockwool RW3 or equivalent (60kg / m3) and a breathable fabric such as Cara.  The most effective positions are where surfaces meet (corners) but experimentation is the key.

Your room dimensions aren't great as you are not far off being a cube and I expect that your head position is going to be pretty close to the dead centre (the worst place).  When faced with a difficult room it's always worth getting a decent set of open-backed headphones to check the low end.

JonnyBgoode

Whistler said:

That is the principle of controlling the boomy sound in your room. Each trap cost me under £20 to make.

Wow, awesome job, thanks.

Musicwolf said:

Forget foam, it really is of little use.

Rockwool broadbad absorbers are pretty easy to make (I managed it) and there are plenty of 'how to build' vids out there.  You need Rockwool RW3 or equivalent (60kg / m3) and a breathable fabric such as Cara.  The most effective positions are where surfaces meet (corners) but experimentation is the key.

Your room dimensions aren't great as you are not far off being a cube and I expect that your head position is going to be pretty close to the dead centre (the worst place).  When faced with a difficult room it's always worth getting a decent set of open-backed headphones to check the low end.

Ah, my cans are Beyer DT770 so no open back...

Thanks for saving me cash on the foam guys. I have a whole roll of unused rockwool n the loft so it looks like that might be a good start point.

Musicwolf

I'd caution against the fluffy insulation material, it is very low density (better than nothing but RW3 is much better).  Taming the high frequencies is pretty easy, even foam will do this, the problem is at the low end.  If you tame the highs but not the lows you'll end up with a very 'boxy' sounding room.

The way that absorbers work is that they convert the Kinetic Energy of moving air molecules in to tiny amounts of heat.  You want a material that is dense enough to slow the air molecules but not so dense that it becomes another reflecting surface i.e. another wall.  To work effectively you want the absorber to be at a quarter wavelength distance from the wall at the frequency that you are trying to treat.  The air isn't actually moving at the wall, max movement is 1/4 wavelength away.  A 100Hz wave has a wavelength of approx. 3.3m so a quarter wave is 825mm from the wall - that's quite a distance.  My absorbers are 100mm thick and spaced a further 100mm from the wall so their performance is tailing off below 400Hz (although I'm still getting some benefit).

Whistler

Musicwolf said:

I'd caution against the fluffy insulation material, it is very low density (better than nothing but RW3 is much better).

The slabs, whether from Rockwool or another company, have a higher GFR (gas flow resistivity) than the fluffy rolls of insulation. GFR and density (how compact the insulation is) are not exactly the same but for the OP's purpose will be close enough.

Slabs will be ideal for broadband traps, usually 100mm-200mm minimum deep, and the fluffy will be ideal for the bass traps - and bass traps need to be thicker, deeper, for the reasons @Musicwolf gave regarding frequencies and wavelengths.

Edited to add that @Musicwolf 's 100mm thick traps spaced 100mm from the walls and ceiling are very good and probably the best example for the OP to follow.

JonnyBgoode

Having thought about my working space, plus a bit more research, 100mm panels set 100mm away from the walls will be tough to implement in my tiny space plus I really don't have  the time/space/skills to build them. I loathe DIY.

Elsewhere on this forum @Danny1969 suggests using thick (2") canvas art frames, stuffing them with rockwool. Ingenious! and also I read that 50mm traps set 50mm away from walls will help to some extent (this from an acoustic specialist).

So this is my preferred solution, but where do I get these? I've been to my local The Range Store and searched online in tons of places, can't find anything that thick except maybe very small prints. many places don't even list the thickness.

Whistler

Here is the calculator: http://www.acousticmodelling.com/porous.php

Enter 50 for absorber thickness and leave the air gap at 0. Click calculate. The absorption coefficient is above 0.8 from about 1kHz upwards. Now enter 50 in the air gap and click calculate again. Now the absorption coefficient stays above 0.8 from 420Hz, so the air gap (usually the same depth as the trap) costs you nothing yet helps the trap perform a little over twice as good as without the gap.

1 is the ideal, perfect absorption coefficient. 0.8 and above is generally accepted as a realistic, practical coefficient. The lower the coefficient the less effective traps are, down to useless at 0.2 and below.

In the OP you said, "Peak resonance is around 139-156hz." You can see from the caluculator that 50mm traps 50mm off the walls and ceiling are not thick enough to do anything useful at your problem frequency range. If you put 200mm thickness and gap, the recommended minimum from acousticians, in the calculator, you will see why it is the recommended minimum for music. As losing 400mm from each wall and the ceiling is more than bedroom studios can usually accommodate, 100mm thickness and gap are the most commonly used measurements. Put those in the calculator and you will see good performance down to 200Hz and 80Hz, the lowest frequency of a man's voice (women are around 120Hz) and also the lowest note on a 6-string guitar, have some level of trapping effectiveness. More importantly, that gives some help at 139-156Hz.

The one thing I haven't explained is the middle number in the calculator, flow resistivity. That requires you to be able to find out what the GFR (gas flow resistivity) of the material you are using. There is a topic on gearspace.com, here, but it is long, technically detailed and may not be interesting to you. Either way, you have the link. To keep it simple, when you are making traps up to 150mm thick, use the more dense glass or mineral wool insulation which comes in slabs, and when you are making bass traps which will be from 200mm to 1m thick, use the fluffier insulation which comes in rolls. Between 150 and 200mm you could use either as it is a close call as to which will work most efficiently.

I apologise for this being a long reply but I was incensed by your acoustic specialist telling you that 50mm thickness and gap will help solve your problem frequency range. At least now you can see for yourself that it doesn't and you can double-check what so-called specialists tell you in the future. I would hate to think you bought traps only to discover they do not help you at your problem frequency range.

Lastly, coverage. Ideally plan to cover between 20% and 50% of the total surface area in your room. If for now you want, say, to make or buy 2 traps, that is at least a good first step. You can add more when you have the money and the interest to better smooth out your peak frequencies. Place the first traps on your walls at ear level so that you get the best performance from the start.

GIK Acoustics UK and other places sell acoustic traps.

Edit 1: By my calculations, using your garden office's dimensions of 3m (length) x 2.7 (width) x ? (height), the problem frequencies should be around 114Hz and 127Hz if the place was empty.

Edit 2: Tanny Reveal monitors go down to 56Hz.

thermionic

I have a similar sized room (and old Tannoy Reveals!). I bought 4 600mm x 600mm and 2 300mm x 300mm acoustic tiles from Studiospares for about £100. It was tricky to place them with a window on one side wall and a fireplace and door on the opposite wall, but I manged to mount them symmetrically, with the other two large panels on the back wall to tame reflections from the speakers. I could have probably used larger panels behind the speakers in hindsight. There’s not much room for corner bass traps due to the shelving, sloping ceiling, and window/door but I might try and get some foam ones in future. A room this small is not going to get anywhere near perfect so I’m just aiming to take the edge off. I test any important mixes on headphones, a couple of hi-fi systems, and even the car.

https://i.imgur.com/yZIeTCP.jpg

https://i.imgur.com/Nb2jHek.jpg

https://i.imgur.com/3irDI61.jpg

JonnyBgoode

Whistler said:

I apologise for this being a long reply but I was incensed by your acoustic specialist telling you that 50mm thickness and gap will help solve your problem frequency range. At least now you can see for yourself that it doesn't and you can double-check what so-called specialists tell you in the future.

Firstly, many thanks for your time/detailed reply I do appreciate your input, looks like I have little choice other than to buy some proper traps.

I should probably correct any misconception I created with my earlier post, I have not been advised by an acoustic specialist, I was reading a post on this forum in response to someone else. I think the guy used to treat commercial studios, he was really disillusioned and fed up with the industry I recall. I will try and find it again but no luck so far.

JonnyBgoode

thermionic said:

I have a similar sized room (and old Tannoy Reveals!). I bought 4 600mm x 600mm and 2 300mm x 300mm acoustic tiles from Studiospares for about £100.

Looks neat but going by the advice above those tiles would not help my bass boom problem.

Rocker

A zero cost option is to reposition your desk so that the RH speaker is close to where the black guitar is hanging on the wall and the LH speaker is about where your monitor is now.  Both speakers will be firing at an angled wall and you will have your monitor across the RH corner of your room.  Your seating position will feel a little odd at first but as your room is more or less square, you will always have a problem with boom and suckout as sounds bounce up and down the room.  Try the diagonal suggestion before spending any money or time on room treatment solutions.

JonnyBgoode

Rocker said:

A zero cost option is to reposition your desk so that the RH speaker is close to where the black guitar is hanging on the wall and the LH speaker is about where your monitor is now.  Both speakers will be firing at an angled wall and you will have your monitor across the RH corner of your room.  

What an interesting suggestion, thanks!