John Sayers' Recording Studio Design Forum

Hi there,

First thing first: THANK YOU in advance for taking the time to read this, if you have something to share even better.

I had started a post about my "to be" studio some months ago. Nothing has changed since then but I have acquired some gear (and money) to finally install it.
You will find attached the skp with all measures, the Bob Golds result and some photos as well. I have not done REW yet as I don't have any doors installed and my monitors have not arrived yet. Also I have listed my minimal ammount of gear and my objectives with this studio. Finally I have some particular questions at the end of this message.

Please note I have calculated the room height basing on the lowest height (3,05m), but as you will see on the skp it raises to the back 1,2 extra meters. I do not know how this affect on room modes, nor how to calculate it altough I believe once I can use REW it won't be neccesary to make extra calculations.

GEAR
Monitors: Alesis Monitor two with RA100 power amplifier
Interface: Maudio fast track
Keyboard/MIDI: Maudio Prokeys Sono
Mic: Audio Technica AT2035
Guitars, amp, etc.

I plan to write music, do some mixes for my friends and track separately.

Questions
1) Where should I place my monitors considering they have a rear bass reflex. I plan making my own monitor stands (I have read some posts about this but would appreciate a simple calculation for a 15kg monitor)
2) For what I understand I should place some low band absorvers to tackle the really low end and it wouldn't hurt some diffusors on the side walls? I know this sounds very amateur but I don't like writing in complex terms.
3) What is your reccommendation for the window, I don't mind reflections while composing but I should consider extra panels (or heavy courtains while mixing? Or should I calculate my normal environment with the windows not covered?

Dimensions
W: 6.1m
L: 4m
H: 3.05 (lowest)
Note: I do not need to heavily isolate it from the exterior, I have no neighbours around.

THANK YOU once again

PS: Photos coming later

Hi there!
Here are some pics of the studio.
You may notice there is no paint (of course as I have to define the kind of treatment on walls) and no floor. Below the studio I have a storage room, no noises there and no need to isolate the studio from it.
Electricity has been divided on lights, equipment (wall sockets) and air conditioning with its correspondent switches. Contruction has been made with standard 9 tube brick and concrete. The ceiling is pine with a very good isolation membrane and tin roof on top. Windows are good heavy aluminium, with double glazing and the gap of air in the middle (I cannot remember how you call that in english altough I have it on the "Build it like a pro" book).

It would be impractical to give you my budget as I live in Argentina and prices are a lot different!!

Let me know if I'm missing any important detail.

Thanks,

Mauricio

Ok, so theres not much you can help me with yet because I still have to make rew analisis.

One quick question, I have Alesis Montitor two:
Dimensions: (WxHxD) 14"x20"x14"
Weight: 34 lbs. each

Where should I place them? I believe I should consider my room proportions for height and distance from the walls. These have a rear reflex so this is something to keep in mind.

I appreciate if you could help me with this considering the dimensions of my room which I described in my earlier posts. Also I would need to build some monitor stands. For this I was considering the two "tubes" filled with sand (the floor is floating concrete) but I am doubtful regarding the rubber right below the speaker as they are quite heavy, any suggestion?

Thank you

Hola Mauricio, y bienvenido al foro! también tenemos una área en español, si prefieres. Pero no hay problema en continuar en inglés!

OK, on to your thread and your questions:

Yes, that will have a big effect on the modal response of the room. You can only use calculators (such as Bob Gold's, which is my favorite) if the room is rectangular. As soon as the room becomes non-rectangular (or example, by splaying one or more walls), then the predictions are no longer valid, since the distances and reflection angles have changed. The predictions for the axial modes of the walls that are still parallel will be correct, but predictions for all modes that involve the non-parallel walls will be incorrect. So the axial modes for those walls, as well as some of the tangential modes and all of the oblique modes will be wrong.

If the walls are just slightly non-parallel then it doesn't matter much, but if there is a big difference then it does matter.

Place them on very massive (heavy) stands, such as brick, concrete or sand-filled metal. The height of the stand should be calculated so that the acoustic axis of the speaker will be 1.2 meters above the floor. Check the manual for your speakers: it should tell you where the acoustic axis is located, but if I recall correctly, on the Alesis Monitor Two it is in line with the tweeter, so the woofer is below and the midd range driver is above.

The best location for those speakers would be right up against the front wall, but since they are rear-ported you will have to leave a gap between them and the wall. I would suggest at least 10 cm between the rear edge of the speaker and the front face of the acoustic absorber on that wall, and since the absorber should be at least 10cm thick, that places the rear of your speaker about
20 cm from the front wall.

The distance between each speaker and the side wall should be about 28% of room width. Your room is 4m wide, so the left speaker will be about 112 cm from the left wall, the right speaker will be about 112 cm from the right wall, and the speakers will be about 176 cm apart (I'm talking about the center line of the front panel of the speaker here). That means that your head should be about 176 from the speakers as well, which will place your head roughly 2.1m from the front wall, and 4m from the back wall. That's actually a good location, since it works out to roughly 36% of room depth, which is good enough (optimal is 38%). So you will have to angle your speakers inwards by 30°, so they are pointing directly at your ears. Start with that setup, and move things around just a bot each way, to see if you can find a better location, but that should work out well.

It is a small room, so you will need a LOT of bass trapping! I would suggest putting superchunks in all the vertical corners, and see how that works out. You might also need superchunks in some of the horizontal corners. You can check how the room is responding using REW, and then figure out if you need more trapping.

You will also need thick absorption on your first reflection points, on the front wall (between the speaker and the wall), and on the rear wall, and a cloud on the ceiling. You might also need additional absorption on the side walls in places, but once again measure the room with REW first, to help decide on that.

If the window is at your first reflection point, but you still want to have natural light, then your best option would be build an absorption panel on a movable stand that you can wheel into place when you need to do critical listening, and take out of the way when you want natural light.

No tan diferente de Chile! Conozco Bs.As. bastante bien, y creo que entiendo la moneda de Argentina. Bueno, mejor dicho: yo lo entiendo hasta el punto que la Cristina K. permite entenderlo! Y eso cambia cada dia, al pareceer...

You cold do that, yes, but you don't need rubber UNDER the stand: you need it on top, between the speaker and the stand. Just build your stand on the floor, to the correct height, place a pad of Sorbothane rubber on top, then place your speakers on top of that.

One more point about your speakers: They will be very close to the front wall, so you will need to roll of the bass response by about 6 dB, starting at the baffle step frequency. Your speakers do not have controls on the back to do that, so you will need a good quality phase-linear crossover or parametric equalizer to do that. Try rolling it off - 4dB first, below the baffle step frequency, and see how that goes. If you are still not getting roughly even power balance, then try rolling off -5 or even -6. You might also need to tweak the frequency up or down a bit, as needed.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hola Soundman, muchisimas gracias por tu respuesta, un abrazo desde Argentina.

I will continue in english so everyone can understand and we do not have to move the thread.

Acoustics: Yes, my room would be very good according to Bob Gold IF it was rectangular but its not. According to what I read I could make use of that wooden ceiling (and height) to have a more natural acoustic rather than a damped shoe box. I know its a lot more trouble and calculations, but the house had already that style of ceiling and if I really cannot cope with it I'll just make it a box...Also, in theory if the slope of the ceiling goes down to the "control" area (monitors) I should be on good track, and this takes me to.......
...
This frightens me a bit.
" Your room is 4m wide, so the left speaker will be about 112 cm from the left wall, the right speaker will be about 112 cm from the right wall, and the speakers will be about 176 cm apart (I'm talking about the center line of the front panel of the speaker here)."

I considered my front wall as the one with the window, and that was the whole plan because of the view, fresh air while composing, etc. I started placing the monitors on the skp as per your description but I found myself 1.9m from the back wall (with the highest ceiling), so I think we are on different plans. I read in Candas audio a handy pdf which elaborated on the proportions and found that (obviously) I should have planned to place the speakers on the "shortest wall". BUT they evaluate the possibility of placing monitors on the longest wall (pic attached)

I thought I found solution but nope, the dimensions produce the following: 4,34m from opposite side wall (which is fine) but Ratio 1 (.447) from the rear wall, that is 2,68m (!!), which means 1,32 from the back wall (!!!!!). If I were to place the speakers 20cm away from the rear wall (as you suggested due to the reflex) it wouldn't let me open the window

...needless to say I'm in big trouble

Theres no point elaborating on the other details you (so kindly) gave me your opinion.

"You cold do that, yes, but you don't need rubber UNDER the stand: you need it on top, between the speaker and the stand. Just build your stand on the floor, to the correct height, place a pad of Sorbothane rubber on top, then place your speakers on top of that."

Yes, I didn't express myself correctly, I meant betwee the speaker and the top. Do you know the translation for sorbothane? No traces of that in Argentina (less probable with Cristina!!)

Gracias nuevamente,

Mauricio

I think you mean Cardas, not Candas, but you can safely ignore 90% of the "advice" you see on that web site, and other audiophile places like it. They are talking about home theaters, not recording studios, which are very different anyway, but the purpose of that web site is to sell you speaker cables that seem to have magical properties. Places that promote snake-oil type products and magical voodoo geometry for acoustics is probably not the best place to get good information on how to build a recording studio! Rather, I would suggest that you purchase some solid, reliable, trusted books about acoustics and studios. Start with "Master Handbook of Acoustics" by F. Alton Everest. It is simply the best introductory book on the subject that I have every seen, and it teaches you how sound waves and room acoustics actually work in the real world, not the way some uninformed people image that things work in their heads... I'd also suggest that you get "Home Recording Studio: Build it Like the Pros", by Rod Gervais, and read John Sayers own work http://johnlsayers.com/Recmanual/index.htm. All of those are very reliable, solid, sound texts on how things REALLY work in acoustics, and how studios are actually built.

Just one quote from that site demonstrates the total lack of understanding of room acoustics. When someone asked how to treat the walls, floor and ceiling of a room, the response was: "Soften the surfaces a much as possible. Use thick padded carpet and linen over cotton batting on the walls (or similar). The batting thickness is proportional to percentage of the area covered and shape of room. As a room goes from rectangular to trapagon in shape the thickness required diminishes dramatically. That said, if you do all surfaces, a 3/8" foam pad under the carpet and 1/8" of a fibrous material or foam on the walls (like linen over cotton batting or a thin polyurethane foam) will suffice if you give a little extra in the corners and at the first reflection points. If only half the surface is covered, probably 1/2" foam would be close, with a double pad under the carpet...". Well, sorry, but if you follow that advice you'll end up with a room that sounds like a dull thuddy cave! In reality, carpet is really, really bad acoustic treatment. It is selective, random and unpredictable (as demonstrated by both Everest and Gervais in acoustic laboratory tests), and does the exact opposite of what a studio needs: Carpet absorbs highs quite well, absorbs mids to a certain extent, and absorbs no lows at all: What studios need is the opposite: A LOT of absorption in the lows, some in the mids, and almost nothing in the highs. Put it this way: how many professional studios do you see with carpet on the walls, floor and ceiling? Answer: ZERO! There's a reason for that. Carpeting a room makes it LOUSY for acoustics. So any place that tells you to carpet the walls of a studio is waaaay off base. Yes, the walls of movie theaters are often carpeted, but that's for a totally different reason. The actual acoustic treatment in cinemas is BEHIND the carpet: the carpet is only there for aesthetic reasons.

If you take a look at the actual acoustic treatment in REAL studios, you will find that " 3/8" foam pad under the carpet on the walls " is something you NEVER see. Rather, you see very large, very thick, very deep absorbers, that are carefully designed and carefully placed in the correct locations to treat the actual acoustic issues found on the room.

Also, the amount of coverage that you need for your treatment has nothing at all to do with whether the room is "rectangular or trapagon in shape", and everything to do with the amount of surface area vs. the room volume vs. the coefficient of absorption of the surfaces, as calculated using the Sabine equation. The percentage of surface area that needs to be absorbent has no direct relationship to room shape. So the claim that rooms with magical shapes need "dramatically diminished" absorption thickness is garbage. The thickness of the absorption that is needed depends on many factors, none of which are related to the room ratio. And since absorption is related to frequency, there is no one single thickness that you can use all around the room to absorb uniformly.

To make matters worse, that web site doesn't even know which end of the room is which! They seem to think the back is the front, and the front is the back! If you sit in your car, what do you call the part that you can see out the windshield? That's the front, right? But according to the web site, they would call that the "back", and the part behind you would be called the "front": Not sure how they came up with that!

OK, so let's set thing straight here: In a studio, the FRONT of the room is where the main speakers are. The front wall is (obviously and logically) the wall that you are facing when you sit down at the console. It is called the "front" wall quite simply because it is in "front" of you! And the wall at your back is called the "back" wall for the same reason.

Your head should be closer to the front wall (close to the speakers) and further away from the back wall. The reason for that is very simple and logical: you want to hear ONLY the direct sound coming from the speakers, not reflections coming from behind you. Theoretically, you do not want to hear any reflections of a sound until at least 20ms after you hear the direct sound, and even then the level should be 20 dB lower than the direct sound. The best way to accomplish that is to put as much distance as possible between your head and the rear wall, with the speakers firing down the longest axis of the room, not the shortest axis, so that the reflections take a long time to get to the rear wall and bounce back to your head. If you have your head close to the rear wall, you hear the reflections too soon, and that "muddies" up your perception of sound. Your head should be far from the rear wall (the one behind your back). You will never see a world-class professional studio where the engineer's head is close to the rear wall. In fact, the theoretical best place for your head is at 38% of the room depth, meaning that your head is 38% away from the speakers, and 62% away from the rear wall. That is the point where the modal peaks and nulls are at the least objectionable levels, regardless of the dimensions or ratio of the room. This is a simple consequence of the way the sound pressure levels and particle velocities change as a standing wave moves about the room, based on the laws of physics. This can be demonstrated with simple geometry.

OK, having said that: If you really have to, then you CAN set up your room with one of the long walls at the front, but it is not the best way to do it.

One final point: The front of the room should also be the place where the ceiling is LOWER. It is the BACK of the room where the ceiling should be highest. And from side to side, the ceiling should be at the same height, so that room symmetry can be maintained correctly.

Then there is something wrong with the way you were doing it! This is the way it should work out, when done correctly:



In fact, I would probably move your speakers a bit further apart and also a bit further away from the front wall, to get the intersect point a bit further back in the room. It should be a few cm behind your head, not inside your head as I am showing here.

No, I said to place them 20 cm from the FRONT wall, not the REAR wall!

You can ignore that: it is all garbage. Positioning speakers in a room has nothing to do with magical geometric "trapagon" shapes (whatever they happen to be!). In reality it is all about the way that the sound waves from the speaker interact with the wall surfaces around it. Technically, this is called the "Speaker Boundary Interface Response", and is defined by the distance between the speaker and the front wall, as compared to the wavelength of the sound waves. At certain frequencies, phase cancellation occurs simply because the wave bounced off the front wall and arrived back at the speaker 180° out of phase, so it cancels itself perfectly. That means you get a "gap" in the response curve at that frequency, and also at twice the frequency, three times the frequency, four times, five times, etc. So you get comb filtering as well as phase cancellation. The frequency where this happens is related ONLY to the distance between the speaker and the front wall. It is NOT related to voodoo or magical geometric ratios. In order to make it happen at frequencies that are lower than the lowest frequencies that the speaker produces, the speakers would have to be at least 2.5m from the front wall. That makes the round trip for the cancelling wave = 5 m, which is half of a 10m wavelength, so the cancellation will only happen below about 34 Hz, where it does not really matter. Since it is impractical to have your speakers way out in the middle of the room, the next best thing is to put them as close as possible to the front wall, which pushes the SBIR frequency up into the low mids, where it also does not matter so much, since absorptive treatment can be applied effectively. For example, if you get the speaker 25 cm away from the front wall, then SBIR happens at 344 Hz. (50 cm round trip, half wave of 1m), but at that frequency a 4" panel of 703 is already effective, with an absorption coefficient of greater than one, so the problem can be greatly damped just by putting 10cm thick 703 on the front wall, between the speaker and the wall.

This is real acoustics, calculated using the real equations of physics, not the voodoo pseudo-science of mythical "golden trapagons". Curiously, if you do a Google search for that term, you'll find a grand total of 435 hits, most of which point back to that same questionable web site. You'll find a lot of questions about "Has anyone every built a room based on this?", and very few answers. I wonder why?

In the real world of acoustics, there is not such thing as a "perfect ratio". There are just good ratios and bad ratios. Scientist such as Bolt, Louden, Sepmeyer and others have done studies on room ratios, and come up with dozens of good ones. Other people (notably Eric Desart) have analyzed all these and found that, in reality, these ratios can be graphed, and show up as regions of good and bad ratios. His work is available on the Studiotips forum, which seems to be offline right now, but you can find it here when the site is back up again:

http://forum.studiotips.com/viewtopic.php?t=684

That's what Bob Golds calculator links to, for rating the ratio.

So what is a ratio anyway? And what makes it "good" or "bad" acoustically? A ratio is just the relationship between length, width and height. Acoustically, a room ratio also describes the relationship between room modes. A "room mode" is just a frequency where wave can bounce around the room once and get back to its starting point exactly in phase with itself. When that happens, you have a "standing wave", which means that the pressure peaks and nulls for the wave always occur at the exact same point in the room, so that specific frequency will always sound louder in some places and very quite in other places. Standing waves, or "modes", only happen at very specific frequencies that are directly related to the room dimensions.

There are three kinds of modes: "axial" modes, where the wave just bounces back and forth between two parallel surfaces; "Tangential" modes, where the wave follows a path that involves four surfaces (two pairs of parallel surfaces), and "Oblique" modes where the wave follows a path that involves all six surfaces (all three pairs of parallel surfaces).

All that a room ratio tells you is how evenly the modes are spread out. Ideally, you want a ratio where the modes are spread out smoothly, not bunched up close to each other, and with no big gaps between them. In a perfect room, there would be several modes for each note on the musical scale, but you'd need a huge room to do that! It would have to measure at least 17m in each direction

So real-world rooms will ALWAYS have modal issues, since it is impossible to get an even modal spread in small rooms. The best you can do is to get a ratio that spreads the modes around as evenly as possible. And one more time: there is no such thing as a "perfect golden" ratio. ALL small rooms have poor modal spread for low frequencies, simply because they are small and sound waves are large! This is a simple fact of life: basic physics. Basic mathematics. Basic geometry. Basic acoustics. There is no voodoo incantation that will make a small room "perfect". There is no ways to get around the laws of physics. The smaller a room is, the more modal problems it will have, regardless of magical geometry.


Now, since your room is not rectangular, there is no simple way to calculate the modal response.

If we look at the ratio at the front of the room, we get this:

FRONT
Room Dimensions: Length=6.1 m, Width=4 m, Height=3.05 m
Room Ratio: 1 : 1.31 : 2
Closest: #6) M. M. Louden: 1971: 2nd best ratio" 1 : 1.3 : 1.9

If we look at the ratio at the back of the room, we get this:

BACK
Room Dimensions: Length=6.1 m, Width=4 m, Height=4.25 m
Room Ratio: 1 : 1.06 : 1.52
Closest #9) M. M. Louden: 1971: 5th best ratio 1 : 1.2 : 1.5

But according to both Everest and Desart, it is possible to estimate performance very roughly by using the average ratio. If we do that with your room, we get this:

AVERAGE:
Room Dimensions: Length=6.1 m, Width=4 m, Height=3.65 m
Room Ratio: 1 : 1.09 : 1.67
Closest: #24) A worst case scenario calculated by RPG 1 : 1.075 : 1.868


That said, there is a way to accurately predict the modal behavior of non-rectangular rooms: by using FEM/FEA software and an expert operator to set the boundary conditions correctly, and interpret the results. That would be expensive, and is not necessary anyway!

In reality, ALL small rooms will have modal issues, and ALL small rooms will need large bass traps to help damp those. So forget about trying to nail a "perfect" ratio, and instead do an actual acoustical analysis of the room (using REW), which will identify where the REAL modal issues are, rather than trying to predict them of guess where they might be. Just run REW on your room, and you will find out where your modal issues are, and you can then figure out what to do about them. No "golden trapagons" needed!

I don't think so! I think you've just been looking in the wrong place, and getting bad information, until you cam to the forum! But now you are in the right place, and all the good, correct, scientific information is right here, so you should be fine!

You can buy it online, directly form the manufacturer. They can ship it to you. It won't be cheap, but there is nothing better for isolating speakers:

http://www.sorbothane.com/material-properties.php

Anyway, please post some more pictures of your room, and also prepare an accurate SketchUp model showing the correct dimensions, and post that here too.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart,
First of all thank you for taking the time to offer your knowledge on the subject, I really appreciate it.
It was my fault not checking on the web site before posting, my bad, and sorry for wasting your time on that. I guess I was a bit desperate to find some relief!! I have read Build it like a Pro from cover to cover as well as other audio books (a few) and many, many "trash" blogs and web pages as you say. Everything you have explained, altough I am familiar with the concepts, sounds brand new when applied to reality by an expert!!

When I built the studio it was in reality a part of the house which was left available, and I adapt it (minor adjustments) until I reached Louden 2nd best, but once again I considered the front as the length and the width as the side walls when it should have been the opposite. Thus ceiling (which couldn't be done other way) is lower in what I considered the front (which was wrong).



Yes, I now understand that it should be placed that way but, in case I would re arrange the room that way, I should place a floating ceiling because reflections would be totally assimetrical...am I right?



Right, I meant FRONT.



Well, that will be a challenge considering I have to be able to open the windows to get fresh air, and that won't happen if I plan to place the speakers 20cm from the front wall, which is a glass surface...not the best bass dampening material

I understand that in the unusual case I could place the speakers somewhere using the front wall as the one with the window (6m) I should place it a bit further from it (further than 20cm) and a very, very serious absorver on the rear wall to avoid early reflections (almost impossible at that distance). If this is acoustically acceptable I woul be
In case its not (very probable) I consider placing the monitors as you describe in your drawing and then keep the window wall as a composition area with the instruments, etc. even with a simple recording system to get the ideas and leave the critical listening to the 4m front wall design. This sounds like a good idea but I really think I shoud even the ceiling as a flat surface or angling it downwards to the speakers.

I will take all measures and more pictures today, THANK YOU once again.

Ok then, here are more photos and an updated skp. Also I have added the monitors with the right measures and a head for calculations.
You may notice there is a difference in height on the left side (I forgot to mention that), its very noticeable on the skp but not SO much on reality.

I was thinking, and maybe its a dumb idea: what if I point the monitors upward? I dont mind sitting higher to make the triangle right. This way I could use the large rear wall (4.1 meters) with some serious isolation, and the front wall with low frequency absorbers which would go as low as the floor. For example if I point the monitors to the highest of the rear wall I have a 4.7m distance (from the center of the front wall). This would be an extreme example but you get the idea. Is this feasible?

Thank you once again for your advice!!

I would not do that, for psycho-acoustical reasons, as well as for practical reasons. The speakers must be aimed at your ears, and in order to point them up and still achieve that, they would have to be down very low, close to the floor, and therefor obstructed by the desk. Also, our brains are not accustomed to hearing sounds coming from below, but very accustomed to sound coming from ahead or even slightly above.

To be really honest, if that were my room I think what I would do is to just build a new ceiling as high as possible, to get the room into a more useful rectangular shape. If this were going to be a live room, I would say to just leave it like it is, but for a control room, I would try to get it more symmetrical, and laid out properly. Small rooms have enough challenges already, without adding to then with strangely angled ceilings!

But that's just my opinion. Others might have different idea.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.