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Author Topic: Optimal RT60 for a mastering room?  (Read 15663 times)

antonio

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Optimal RT60 for a mastering room?
« on: May 08, 2009, 06:56:57 am »

Hi all,
according to you which is the optimal reverberation time for a mastering room?
For recording studios and surround sound listening rooms there are suggestion like the one reported in the fig.1
My I think that  according to this suggestion that RT60 for a mastering room  shold be between 0,2 - 0,4 seconds?
Or I should think that mastering room should be more close to the acoustic of a domestic  rooms so according  to the fig. 2 it must be higher,  let’s say between 0,4 – 0,6 seconds?
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Ethan Winer

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Re: Optimal RT60 for a mastering room?
« Reply #1 on: May 08, 2009, 02:58:25 pm »

I'm sure others will chime in, but in my opinion RT60 is not a useful spec for domestic size rooms. Small furnished rooms don't really have true reverberation. Rather, it's a series of reflections that decay over time. The typical goal is to use absorption to get all early reflections to -15 dB or more below the direct signal from the speakers. In this case "early" is defined as reflections arriving within 20 milliseconds of the direct sound.

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antonio

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Re: Optimal RT60 for a mastering room?
« Reply #2 on: May 08, 2009, 03:46:48 pm »

Hi Ethan, you highlight  an interesting point. But even if the domestic rooms may not have a perfect exponential decay they  sound more “alive” , from a reverberation point of view, than a control room in a recording studio.  
In any case, I think that, as much as exist a suggested RT60 for control rooms should be a suggested RT60 for mastering rooms
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Thomas Jouanjean

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Re: Optimal RT60 for a mastering room?
« Reply #3 on: May 08, 2009, 04:15:58 pm »

Most Mastering engineers I've worked with wanted a very analytical environment. It usually resulted in rooms on the dead side, with very tight bass and slightly 'enhanced' stereo image.

IMHO, I'd say Mastering rooms, while still needing to be balanced, are usually very controlled environments in which the engineer can make quick decisions without ever doubting what he hears.

My CRs usually have a higher RT than the Mastering rooms and this is not an arbitrary decision I took, it's the result of what is asked by the clients.

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antonio

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Re: Optimal RT60 for a mastering room?
« Reply #4 on: May 08, 2009, 04:32:08 pm »

Thomas Jouanjean wrote on Fri, 08 May 2009 15:15

Most Mastering engineers I've worked with wanted a very analytical environment. It usually resulted in rooms on the dead side, with very tight bass and slightly 'enhanced' stereo image.

IMHO, I'd say Mastering rooms, while still needing to be balanced, are usually very controlled environments in which the engineer can make quick decisions without ever doubting what he hears.



ok, but in terms of numbers? 0,2 s 0,4 s or what?

And, from your point of view, which is an optimal value?


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Thomas Jouanjean

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Re: Optimal RT60 for a mastering room?
« Reply #5 on: May 08, 2009, 04:56:18 pm »

antonio wrote on Fri, 08 May 2009 15:32



ok, but in terms of numbers? 0,2 s 0,4 s or what?

And, from your point of view, which is an optimal value?




The optimal value varies with the room (volume, etc) - there's no particular recipe. The .4/.2 is a good benchmark though.

You should make sure the reverb is as diffused as it can be and that the decay is linear and homogenous (as little variations as possible between octaves).

Not surprisingly, this comes 'naturally' if the room is well designed. (read: RT is not in my top priorities when designing)
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Thomas Jouanjean
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antonio

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Re: Optimal RT60 for a mastering room?
« Reply #6 on: May 08, 2009, 07:18:00 pm »

Thomas Jouanjean wrote on Fri, 08 May 2009 15:56



Not surprisingly, this comes 'naturally' if the room is well designed. (read: RT is not in my top priorities when designing)


Yes ok , but anyway you must consider it so it’s better if you have a target. If you don’t have a particular target o recipe haw you decide which type and how much absorbing material you put in a room? This affect your RT60? right?

Thomas Jouanjean wrote on Fri, 08 May 2009 15:56



You should make sure the reverb is as diffused as it can be and that the decay is linear and homogenous (as little variations as possible between octaves).



I was assuming that this a necessary condition.  So my question comes after this condition.

Thomas Jouanjean wrote on Fri, 08 May 2009 15:56


The optimal value varies with the room (volume, etc).



Yes  in fact  if we consider de above mentioned formula of the figure 1 : tm=0,25 + (V/Vo) 1/3
It’s  clear that that tm changes with the volume. Sorry if I insist but my question was simple : RT 60 more close to a control room  or to a living room? And if it’s more close to a control room or a living room we should quantify this value otherwise it’s just an useless discussion
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franman

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Re: Optimal RT60 for a mastering room?
« Reply #7 on: May 09, 2009, 01:12:01 am »

Gotta chime in on this one. I don't feel that there is a statistical RT time in small listening rooms. It can't be reliably measured, although you may choose to calculate it.

I agree with Thomas, that all mastering rooms we've done are on the dead side... very short (.2 - .4 if calculated) and I tend to shoot in the same range for control rooms as well.

I also agree with Ethan, that the 'field' in these smaller rooms is really about a proper distribution of reflections and CONTROL of early reflections (shorter than the haas effect).... you really need to avoid early reflection back to the listening position shorter than 19-22msec (open for discussion) and louder the -15 compared to direct signal (also open for discussion)...

These are things we typically measure in the ETC function of the TEF... there is no repeatable RT in these smaller rooms, although you can measure a repeatable RT in a typical living room... tends to more like .5 - .8 depending on volume...

my 10 cents....control early reflections, and make a diffuse return after the haas effect.... this is what RFZ design is all about.
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Thomas Jouanjean

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Re: Optimal RT60 for a mastering room?
« Reply #8 on: May 09, 2009, 06:38:08 am »

Francis summed it all very well...

antonio wrote on Fri, 08 May 2009 18:18


Yes ok , but anyway you must consider it so it’s better if you have a target. If you don’t have a particular target o recipe haw you decide which type and how much absorbing material you put in a room? This affect your RT60? right?


Of course I will check it all out and measure, but it never is a surprise.

What I mean is that once I got the geometry / RFZ / Broadband + LF management, the room is already within the RT 'target'. It's low and well within the .4/.2 benchmark. If it's not then I missed something. Controlled LF implies low RT. Then Diffusion will balance the room properly and even out what (and if it) needs to be.

All designers have *RT* in mind when working - but it's not a variable on it's own, it's one variable that is dependent on other. And Ethan makes a good point in his post about RT.

antonio wrote on Fri, 08 May 2009 18:18

Sorry if I insist but my question was simple : RT 60 more close to a control room  or to a living room? And if it’s more close to a control room or a living room we should quantify this value otherwise it’s just an useless discussion



The trend here is obviously close to a CR. Now to quantify this value with a strict number like .3/.15 would IMHO be strange. It will vary with every project. And it's also a question of taste - which cannot be quantified. The broad benchmark of .4/.2 is a good reference point, but that's it. If the client wants a RT higher than .2 in the higher freq range I will do just that. But also warn him...
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Thomas Jouanjean
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antonio

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Re: Optimal RT60 for a mastering room?
« Reply #9 on: May 09, 2009, 07:44:01 am »

Francis, Thomas, Ethan thanks for your for sharing your knowledge

franman wrote on Sat, 09 May 2009 00:12


.... you really need to avoid early reflection back to the listening position shorter than 19-22msec (open for discussion) and louder the -15 compared to direct signal (also open for discussion)...



Francis  this are very interesting point of discussion especially if it’s possible to connect this numbers to what happens from a listening point of view.
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Ethan Winer

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Re: Optimal RT60 for a mastering room?
« Reply #10 on: May 09, 2009, 03:39:05 pm »

franman wrote on Sat, 09 May 2009 01:12

you really need to avoid early reflection back to the listening position shorter than 19-22msec (open for discussion) and louder the -15 compared to direct signal.


Of course I agree with that, but it brings up a related question for you:

You're probably aware of Floyd Toole of Harmon fame, and his new audio book where he says leaving early reflections intact sounds "better" than absorbing (or diffusing) them. I've never had that experience, not once, not ever. Yet more and more I see people parroting Toole and arguing that early reflection are good and absorbing them is bad.

What the hell is up with that?

--Ethan

avare

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Re: Optimal RT60 for a mastering room?
« Reply #11 on: May 11, 2009, 01:38:47 pm »

Ethan Winer wrote on Sat, 09 May 2009 15:39

You're probably aware of Floyd Toole of Harmon fame, and his new audio book where he says leaving early reflections intact sounds "better" than absorbing (or diffusing) them. I've never had that experience, not once, not ever. Yet more and more I see people parroting Toole and arguing that early reflection are good and absorbing them is bad.

What the hell is up with that?



Toole is writing about what sounds pleasing.  We (professional monitoring) are interested in what is accurate.

Andre
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Greg Reierson

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Re: Optimal RT60 for a mastering room?
« Reply #12 on: May 11, 2009, 01:48:17 pm »

Dave Moulton is into early lateral reflections as well. He's a sharp guy but this seems strange to everyone I've talked to.

http://www.moultonlabs.com/more/nick_batzdorf_interview/


GR
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Ethan Winer

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Re: Optimal RT60 for a mastering room?
« Reply #13 on: May 11, 2009, 03:05:21 pm »

avare wrote on Mon, 11 May 2009 13:38

Toole is writing about what sounds pleasing.


It sure does not sound "pleasing" to my ears! Stop me if I already told this story: Laughing

After having absorbers at the side-wall and ceiling reflection points in my 5.1 living room setup for a few years, I replaced them once with diffusors as an experiment. My wife and I sat down to watch a concert DVD, and in less than five seconds she said "Much worse!" and I had to agree. Now, maybe in a room 30 feet wide, bare walls or diffusion are okay. But not in any of the smaller rooms I usually deal with.

--Ethan

Ethan Winer

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Re: Optimal RT60 for a mastering room?
« Reply #14 on: May 11, 2009, 03:13:45 pm »

Greg Reierson wrote on Mon, 11 May 2009 13:48

Dave Moulton is into early lateral reflections as well. He's a sharp guy but this seems strange to everyone I've talked to.


It seems strange to me too, and I can offer a bit more. The last time this came up (only a few months ago) in another forum, Bob Ohlsson said the same thing. So I arranged to visit Dave Moulton at his home and drove the three hours each way to hear his setup. It was the strangest sounding system I ever heard. Dave has B&O BeoLab speakers in a largish room with only a tiny amount of acoustic treatment on the front wall. Imaging was non-existent, and everything sounded like it was floating in the air four feet above the speakers. There was so much ambience on the music I wanted to ask Dave if he accidentally had his 5.1 processor set to one of those "large hall" type presets, but I didn't want to embarrass either of us so I didn't ask. Laughing

--Ethan

antonio

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Re: Optimal RT60 for a mastering room?
« Reply #15 on: May 13, 2009, 09:27:05 am »

franman wrote on Sat, 09 May 2009 00:12

 you really need to avoid early reflection back to the listening position shorter than 19-22msec (open for discussion) and louder the -15 compared to direct signal (also open for discussion)...



Recently I read an interview of  Geroge Massemburg   ( http://audioproforum.com/index.php?module=Pagesetter&fun c=viewpub&tid=11&pid=3  ).
He explains that in his  studio C at BlackBird Studios  reflections are -40 dB louder than direct sound. He says that it’s like an anechoic chamber but it doesn’t  sound like that.
This concept is quite new.  For shure the idea of listening without having an ambient between you and the speaker is interesting  and it does make sense. I don’t know how much is effective.
Cold be this an improvement  of  the concept of RFZ?
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Thomas Jouanjean

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Re: Optimal RT60 for a mastering room?
« Reply #16 on: May 13, 2009, 11:30:21 am »

AFAIC it's not anechoic-like for sure: decay in the room exists, although not the same type as in a more "classical" CR, and floor is of course reflective.

I remember someone using the word "Ambechoic" to describe the room (RPG engineer I think). It is an excellent way of describing it.  

It is in many ways a RFZ room, based a new way to implement the concept.

One important point: I suspect the very deep diffusors he uses (that go really low, like 100Hz (?) for the walls and 60Hz (?) for the ceiling IIRC)  actually do mechanically absorb a LOT of energy in the LF, and a very healthy amount in the MF and HF range. So while they are primarily diffusors, they are certainly used as absorbers too.

They obviously bring a new concept on the table. It sure is amazing.

But unfortunaytely, for 99,99% of the studios out there this is not a viable option/model. Technically and cost wise. And this is clearely very far away from the average living room.

As an extreme design, it stresses the importance of proper diffusion in a room.

I hope I get to visit it at one point Smile
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J.F.Oros

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Re: Optimal RT60 for a mastering room?
« Reply #17 on: May 13, 2009, 04:23:08 pm »

Thomas Jouanjean wrote on Wed, 13 May 2009 18:30

I remember someone using the word "Ambechoic" to describe the room (RPG engineer I think). It is an excellent way of describing it.
Yeah, I think that was Peter D'Antonio from RPG, who was actually involved in the design of that room.

A few thoughts about this studio you can find in this discussion, from Eric Desart who had the pleasure to visit the room and talk to mr. Massenburg about it.

http://forum.studiotips.com/viewtopic.php?p=36850#36850

(PS : please disregard the whole offtopic messages between me, Bert and the others there  Very Happy)
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Steve Hudson

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Re: Optimal RT60 for a mastering room?
« Reply #18 on: May 14, 2009, 04:08:10 pm »

I had the privilege of meeting George and listening to a variety of music in his room at Blackbird a few summers ago and it sounds unlike any space I've ever been in. Extraordinary integration of the room and the monitors - the imaging across 360 degrees is scary good. If the goal of an RFZ-type room is to minimize the interaction of the room with the sound sources, Mr. Massenburg's room succeeds. Listening to the 5.1 mix of Dark Side of the Moon was one of the most exciting audio experiences I've ever had.
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L_Tofastrud

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Re: Optimal RT60 for a mastering room?
« Reply #19 on: May 25, 2009, 01:50:28 pm »

antonio wrote on Sat, 09 May 2009 05:44

Francis  this are very interesting point of discussion especially if it’s possible to connect this numbers to what happens from a listening point of view.


Read my PDF on reflections at "Home
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L_Tofastrud

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Re: Optimal RT60 for a mastering room?
« Reply #20 on: May 25, 2009, 02:29:01 pm »

Thomas Jouanjean wrote on Wed, 13 May 2009 09:30

One important point: I suspect the very deep diffusors he uses (that go really low, like 100Hz (?) for the walls and 60Hz (?) for the ceiling IIRC)  actually do mechanically absorb a LOT of energy in the LF, and a very healthy amount in the MF and HF range. So while they are primarily diffusors, they are certainly used as absorbers too.

The diffusers certainly reduce the apparent energy in the room but they don't actually absorb the energy as much as redirecting it. Instead of normal "mirror reflections" the incoming sound is spread out in all other directions (hemisphere) an even though the total energy is the same, the energy that reaches the listener is smeared out in time.

Thomas Jouanjean wrote on Wed, 13 May 2009 09:30


They obviously bring a new concept on the table. It sure is amazing.

I designed a recording room in Norway (mid 90's) ago that had diffusers all over. They were regular 1-D type of diffusers but the room definetly had that feeling where it is impossible to determine its size from listening to it. The studio was used for voice-overs and vocals for music and the engineer claimed it was much easier to add reverb to the recordings than what he was used to. Most people can imagine what the sound of a hand clap is in an untreated and a heavily treated room: this diffused room sounded completely different - it had a certain punch that I can only contribute to the incredibly dense return. I used to have TEF ETC measurements of this room but I can't find them now. The "early refelction" was a huge number of densely spaced returns and the "peak return" was rounded off.

Thomas Jouanjean wrote on Wed, 13 May 2009 09:30


But unfortunaytely, for 99,99% of the studios out there this is not a viable option/model. Technically and cost wise. And this is clearely very far away from the average living room.

I agree with the technical/cost issues. I'm not worried about it being different than living rooms though: if the engineer has control it's all good.

Thomas Jouanjean wrote on Wed, 13 May 2009 09:30


As an extreme design, it stresses the importance of proper diffusion in a room.

It is unfortunate that it is costly and space consuming... Real diffusion should not be underestimated as a treatment tool.

Lars Tofastrud
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Thomas Jouanjean

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Re: Optimal RT60 for a mastering room?
« Reply #21 on: May 31, 2009, 01:29:03 pm »

L_Tofastrud wrote on Mon, 25 May 2009 13:29

The diffusers certainly reduce the apparent energy in the room but they don't actually absorb the energy as much as redirecting it. Instead of normal "mirror reflections" the incoming sound is spread out in all other directions (hemisphere) an even though the total energy is the same, the energy that reaches the listener is smeared out in time.


Ok, what you describe is how a diffusor works. I still "suspect" (so I'm not stating a fact but just a thought) that in GM's room there is mechanical absorption form the diffusors in the LF range. Of course it would be hard to determine the exact amount... But I am enclined to believe there is a very healthy amount of it. Those pieces of wood are rather long, I would expect a good amount of them to start vibrating on their loose side and interact with their stiff side (dampening + transfer etc).


L_Tofastrud wrote on Mon, 25 May 2009 13:29

I designed a recording room in Norway (mid 90's) ago that had diffusers all over. They were regular 1-D type of diffusers but the room definetly had that feeling where it is impossible to determine its size from listening to it. The studio was used for voice-overs and vocals for music and the engineer claimed it was much easier to add reverb to the recordings than what he was used to. Most people can imagine what the sound of a hand clap is in an untreated and a heavily treated room: this diffused room sounded completely different - it had a certain punch that I can only contribute to the incredibly dense return. I used to have TEF ETC measurements of this room but I can't find them now. The "early refelction" was a huge number of densely spaced returns and the "peak return" was rounded off.


I would like to visit it next time I'm in Norway! I am very cautious with overusing 1-D diffusors though. I've played with heavy Diffusion in a LR not too long ago with very good results, but what you mention seems like a lot to me... This LR I did works very well, but I would not add more diffusion in there.

L_Tofastrud wrote on Mon, 25 May 2009 13:29

I agree with the technical/cost issues. I'm not worried about it being different than living rooms though: if the engineer has control it's all good.


Agreed, but the original poster was asking Smile

L_Tofastrud wrote on Mon, 25 May 2009 13:29

It is unfortunate that it is costly and space consuming... Real diffusion should not be underestimated as a treatment tool.


+1

(Edit: fixed spelling)

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