John Sayers' Recording Studio Design Forum Archive

JasonFoi wrote:You could do storeage behind the control room and a machine room under the stairs or vise versa..
Bass trapping covered in wood slats, foil, pegboard, etc will keep the livelyness there and keep the sound light and airy.

Thanks! I don't really need a machine room though. Regarding bass traps: some of these panel absorbers?

http://johnlsayers.com/Recmanual/Titles/Acoustics2.htm

if we make an alley behind the CR then wouldn't we lose even more space?

True, but you DO need to get into the studio somehow! Unless you have another way to get in, there isn't much choice about having an "alley" there. If you don't need the area beyond for storage, then use it for your HVAC silencer boxes...

This was one of the reasons for splaying the wall in the first designs

Right, but that wastes even more space. Compare the area lost to the triangular shape of your splayed walls, and the are lost to a simple rectangular shape...

I like all those adjectives for recording violin and acoustic guitars but not sure how to go about that

It's not easy, which is why you don't see much discussion about that. Live room tuning is very different from CR tuning, in character at least, but it DOES use the same basic principles and same treatment devices.

For live rooms people just say, bigger and non parallel surfaces with the appropriate RT60 is best but it is hard to find more info about this.

We've already looked at "bigger is better" (true!) and "must be non-parallel" (false!), so that just leaves RT-60. And that's a biggie! I's important. Very. But unlike control rooms, there's no real "rules" to follow here, except for general guidelines. In general, classical music and classical instruments sound better with rooms that have longer decay times, while rock, pop, jazz and suchlike can be better with shorter decay times. For vocals, you usually want very little room sound. Acoustic guitar: a bit more. Drums are more like classical, sounding better with longer decay times. Etc. There are actually are some "standards" for this, but they don't agree with each other too well, since this is more subjective than objective. For example, DIN 18041 might recommend a decay time of 1.4 seconds for a certain hall for music, while the OeNorm 8115 might recommend 1.1 seconds for a "music room", but only 900ms for a "rehearsal room"... I'm not sure how you justify the difference there!

Add to that, the consideration that not all RT60 times are equal! Just measuring the overall total RT60 for a room doesn't tell you anything about the evenness of the decay across the spectrum. Two rooms might both have RT60 times of 1 second, but sound very different, because one of them has very long decay times in the low end and very short in the high end, while the other has more evenly balanced decays times. The first room will sound "boomy", and "honky" and "dull", while the other might sound quite good. It's far better to measure the decay times for man frequency ranges across the spectrum, usually done on 1/3 octave "slices", and take a look at those individually and together, to understand the room.

Then there's the issue of direct sound, specular sound, diffuse sound, scattered sound.... You can have two rooms with the exact same decay times but sounding very, very different if one is purely specular (think "bathroom") while the other is purely diffusive. They both might have the same overall RT-60 times of, for example, 800 ms, but the diffusive room will likely sound more pleasant. Scattered sound is similar to diffuse sound, but not identical.

Perhaps because it is subjective and depends on the usage?

Exactly. Think of what type of "signature" you want your room to have, and try to define that in terms of decay times, frequency bands, reflections, etc., rather than just in subjective terms. Eg, a "bright" room would be one that has a lot of high frequency energy bouncing around, with a mix of diffusion and specular reflection, but with the low end under control. A "dull" room would be the opposite: high-end subdued, but more energy in the low end. A "mellow" room would be somewhere in between, but still skewed to more low and low-mid energy. Etc. Think about what it is that makes each of the usual adjectives actually be like it is.

Once you have that in mind, then you can think about how to achieve that: If you want a bright room, you are going to need some serious bass absorption but it will need to be covered with something that reflects back the high end, and does so diffusely: so slot walls, or slotted wedges, or maybe slotted polys, with deep absorption behind. Or to get the "mellow" sound, you'd need less reflection and more high-end absorption, with some low absorption, but not too much.

To figure out how much total absorption a room needs to get you to the RT60 time you are aiming at, use Sabine's equations, which are very simply. There are more modern, more complicated updates to those equations that are more accurate, but not really necessary to go to that extent for a home studio or project studio: keep it simple, and you'll be close. So assume that you calculate that you need 1000 sabins of absorption in your room, you then need to figure out how to spread that around the room. Usually, you want it spread evenly, but not always. For example, you might have one area of your room where you'll be recording drums and grand piano, so you'd have less absorption on the walls around there, but more on the ceiling, except directly above where you might want flat or curved (poly) reflectors, to redirect some of the energy to the far end of the room.

Etc.

If that is the case, there must be something we can fall back on if we want decent acoustic recordings which is the knowledge I am hoping to gain over here.

To be very honest (and you probably already now this), but mic placement is just as critical as room acoustics for getting good recordings. Probably more so! A good engineer can probably get pretty decent tracks even in a not-great room by careful mic selection and mic placement. But lousy mic placement and(or lousy selection of mics will trash any recording, even in the best acoustic environment on the planet! (And of course, good mic placement in a great rooms will get you exceptional recordings...)

If you really aren't sure what acoustic response your room will need, then consider doing variable treatment, so you can modify the response as needed. Here's a variable device that I designed for one of my customers:

Under construction: Nearly finished: Fully completed in finished room:
Acoustic RT60 response with the device "wings" open to various angles, from 0° to 180°: As you can see, there's a nice range of variability in there: As you open the "wings", you get more and more high end and also less and less low end: so this device "tilts" the response from "dull" to "bright". If you have it partly open, then it is somewhat "warm". There's not a huge variation here (around 150 ms difference between fully open and fully closed), because this an isolation room, not a live room: much smaller than a live room, but larger than a vocal booth. Basically, the central slot "wedge" is tuned to deal with some specific issues in the room, while the "wings" and their backing panels are basically absorption. Opening the wing means there is less depth to the bass trap, hence less low absorption, then folding it across the slotted wedge stops that from acting on the room. It's more complex than that, but that's the basic idea.

I must say I am struggling with this one

Me too! Tuning live rooms is not just science: it's partly science, and partly art. You can get creative, try different things, play around with devices to get the rom sounding like YOU want, not necessarily like some specification says.

Could the fact that it is so big mean that shape doesn't matter anymore?

Wellllll... sort of but not really! Look clsoely at that photo: There is treatment on the walls and ceiling, and that can be changed as needed, so it's not just the size of the room that makes it great. Imagine if you went into an aircraft hanger at your local airport that was the same size as this room.... Somehow, I don't think it would have the same acoustics! Size is important, yest, but so is treatment. A couple of weeks ago I was in one of the best performance halls in the country where I live, and I noticed that the UNDERSIDE of the every single seat has built-in acoustic treatment. These are theater-style seats that flip up when nobody is sitting in the, then you fold down the seat when you sit on it. In most halls, a seat with nobody in it changes the overall acoustic response vs. the same seat with someone sitting there. Vy a very tiny amount, sure, but if there's a few hundred seats not occupied for one performance, then they are for the next, that's a big change. But in this hall, each seat is designed to provide the same response when it is folded up as when there is someone sitting in it! Very smart. So the overall acoustic response of the hall doesn't change much if there's 1 thousand people sitting in there, or just 1 person. Pretty cool, I thought. The bottom panel of each seat is basically a curve slotted resonator with some absorption, and seems to mimic the acoustic response of the human body: mostly reflective/diffusive, with some absorption.

Know any small live live rooms that are famous so that I can be inspired please?

Not sure if it is "famous" but John's Spark One container studio is pretty darn impressive! OK, so maybe Studio B at Avatar? http://avatarstudios.net/rooms/studio-b/ bigger than yours, yes, but not huge like Abbey Road. And mostly rectangular.

Or maybe Sun Studio, in Memphis?:
That's the main live room. Big names like Elvis Presley, Jerry Lee Lewis, B.B King, Johnny Cash, U2, John Mellencamp have recorded there. Pretty much rectangular.

Maybe Sunset Sound, in LA?
That's their studio 1 live room.

Also mostly rectangular... Lots of big names ... Van Halen, Paul McCartney, James Taylor, Bee Gees, Doobie Bros., Whitney Houston, Barry Manilow, Rolling Stones, Crosby, Stills, Nash, Yes, Brian Wilson, Beach Boys, Carly Simon, Miles Davis, Louis Armstrong, Sheena Easton, Janis Joplin, Genesis, Kenny Loggins, ...

Feeling a bit better?

So for small instruments like hand percussion or acoustic guitar could you give me some specific treatment advice to get a nice not too dead not too live sound?

I would probably aim for something in the range of 300ms - 500ms or so for acoustic guitar, unless you like to have a lot of room sound.... in that case, maybe 800ms, or even more. And not too much specular: more diffusive than reflective. But that's just my personal preference for acoustic guitar: other people might prefer longer or shorter times. Especially for different genres.

I'd suggest that you do some experimenting: go play your favorite instruments in many places around town, especially places where you have recorded before, and make notes about what sounds good to YOU, what doesn't. What you like, what you don't like. Use REW to measure the IR for a typical setup (full range speaker where the instrument would normally go while tracking, mic at a typical location where you'd place the room mic. Then figure out a profile of what you want, based on that.

Thanks for this very interesting and very educational chat Stuart. I am learning lots!

Me too! Never stop learning. Acoustics is such a huge subject, and still advancing. New techniques, new materials, new ways of doing things, new music styles... Plenty to keep you researching and learning for many, many years.


- Stuart -

Soundman2020 wrote:True, but you DO need to get into the studio somehow! Unless you have another way to get in, there isn't much choice about having an "alley" there.

By "alley" do you mean a rectangular hallway? Both my first designs did have an alley only it was an angled alley so I thought it would waste less space. Maybe the alley was too big? Now that I look at it, it could be much smaller.

Soundman2020 wrote:Right, but that wastes even more space. Compare the area lost to the triangular shape of your splayed walls, and the are lost to a simple rectangular shape...

Ok so how about something like this? See attached image. I added a rectangular hallway too so we could compare.

Soundman2020 wrote:As you can see, there's a nice range of variability in there: As you open the "wings", you get more and more high end and also less and less low end: so this device "tilts" the response from "dull" to "bright". If you have it partly open, then it is somewhat "warm". There's not a huge variation here (around 150 ms difference between fully open and fully closed), because this an isolation room, not a live room: much smaller than a live room, but larger than a vocal booth. Basically, the central slot "wedge" is tuned to deal with some specific issues in the room, while the "wings" and their backing panels are basically absorption. Opening the wing means there is less depth to the bass trap, hence less low absorption, then folding it across the slotted wedge stops that from acting on the room. It's more complex than that, but that's the basic idea. .

The central slot is an angled panel absorber right? I see those a lot on this site and they look awesome. Doesn't the fact that it is angled mean it is tuned to a whole range of frequencies? I definitely plan to build some of those for my studio when I understand them better. Yours looks very good and very clever to have that versatility!!!!

Soundman2020 wrote:Feeling a bit better?

Yeah!

Soundman2020 wrote: I would probably aim for something in the range of 300ms - 500ms or so for acoustic guitar, unless you like to have a lot of room sound.... in that case, maybe 800ms, or even more. And not too much specular: more diffusive than reflective. But that's just my personal preference for acoustic guitar: other people might prefer longer or shorter times. Especially for different genres.

This is great advice thanks. If I punch in my proposed dimensions for my live room into the amroc site, it says that .6 seconds is the recommended RT60 for a "studio" room. By studio, I guess they mean live room. So maybe I should make this my target or slightly less so that it works too for what you recommend for the guitar or perhaps I could have a livelier side of the room and a more dead side of the room?

Your previous revision was fine. Since this is your personal space and it will only be used to record acoustic guitar and hand percussion, the entry way you had will suffice. However, if you think you would ever invite friends over with larger equpment, then a larger entry might be desireable, but the stairs will present their own challenge. Perhaps a better option would be moving the live room to the south and control room to the north, and installing a large door on the south end instead of sealing off the current one completely. Then you could have a loading area directly into the live room at ground level.

JasonFoi wrote:Your previous revision was fine. Since this is your personal space and it will only be used to record acoustic guitar and hand percussion, the entry way you had will suffice. However, if you think you would ever invite friends over with larger equpment, then a larger entry might be desireable, but the stairs will present their own challenge. Perhaps a better option would be moving the live room to the south and control room to the north, and installing a large door on the south end instead of sealing off the current one completely. Then you could have a loading area directly into the live room at ground level.

Thanks for your idea. The "door" on the south (or east in the diagram) is actually a garage door that opens upward and into the actual room so that needs to be sealed off as it won't be able to open once the inner leaf is built. I could remove it and put a normal door but one day if I sell the house it might be better if it was left there.

To fill Stuart in: Stuart this is actually a garage below a house so there are two entrances. There is also a garage door where a car would enter but I planned on sealing that off because of what I explained above.