Studio build in Wales, UK...again!

[Gregwor]

One thing I was thinking about Greg, is the flex element of panels. Is there any realistic way of either being able to predict what effect that has on increasing TL or compensating for it?

Well that is certainly beyond the scope of the calculator. Yes, how stiff your sheathing is does affect the transmission loss. Check these pictures out for clarity:

MORE-THAN-FOUR-REGIONS-of-isolation-TL-mass-law--NOHDR.jpg

four-regions-of-isolation--transmission_loss-V2.gif

The bottom line is, unless you use very expensive and custom materials, there's no economical way to change it. The materials endorsed on the forum (specifically drywall and OSB) are the cheapest materials that offer great mass and decent acoustic properties. If you can afford a lead building, please build it and share the build with us on the forum

Greg

[Paulus87]

Thanks Greg for sharing those graphs, I actually remember a time when lead was pretty cheap and it wouldn't have been unthinkable to line the entire studio with it!

Recently I've been pondering again more about controlling early reflections with geometry vs absorption. This has been hit upon a little earlier on in my thread but I am still searching for some answers.

As we know sound waves act differently depending on frequency, there is a gradual progression from high to low, ray like to all encompassing, omni-present. So angling walls to deflect high and high mid frequencies can be done with a fair bit of accuracy, which is what we do when we ray trace in our sketch up models.

But, as we go lower down the spectrum and start reaching the point where sound waves are no longer acting like rays then surely trying to deflect them is futile? Even if your angled walls are dense enough to deflect low frequency the waves are going to bounce off in a large, smudgy mess, a bit like ever-growing ripples in water from a stone's throw causing a fog of phasey low frequency sound to hit your ears?

And in reality, depending on construction, I suspect the lowest of lows are going to either go straight through your walls and carry on out into the outside world, or a certain amount will be attenuated, and some will be slowed down and then reflected back in to the room after being delayed etc.

My questions then;

1. What is the frequency range we need to be concerned with when trying to deflect early reflections in a reflection free zone? Is there a standard like the other guide lines found in various documents such as those in ITU-R BS.1116-3?

In theory, if you have the frequency dispersion charts/data of your monitors then you can work out the angle of that cut off frequency which will enable you to accurately work out what angle(s) are required for your RFZ, in order to meet the standard (if there is such a thing)

2. Would it not be better to have a RFZ which is capable of reflecting the ray like frequencies but at the same time attempting to absorb the rest?

I know that is how a lot of people seem to design their RFZ on here, but it seems that the trademarked RFZ concept does not... it relies purely on hard rigid geometry at the front, with absorption and diffusion at the rear.

Interested to hear the responses,
Paul

[Soundman2020]

But, as we go lower down the spectrum and start reaching the point where sound waves are no longer acting like rays then surely trying to deflect them is futile? Even if your angled walls are dense enough to deflect low frequency the waves are going to bounce off in a large, smudgy mess, a bit like ever-growing ripples in water from a stone's throw causing a fog of phasey low frequency sound to hit your ears?

That's why we build soffits and put the speakers INSIDE them! And it accomplishes exactly the reverse of what you are suggesting: it tightens the bass into clean, crisp, even, smooth coverage... It ELIMINATES the fog that would be present otherwise, from just having speakers out in the room

It's not so much about the density of the baffles, but rather about the SIZE of the baffles. The effect you speaker of, where higher frequencies act more like rays and lower frequencies spread out all over in a sphere, is not due to the actual frequency, but rather due to the wavelength of the frequency as compared to the size of the object that produced it. Waves that are smaller than the front baffle of the speaker are projected forward, because the baffle itself blocks them from going anywhere else. There's a rule of thumb in acoustics, that says that waves are not affected by objects that are smaller than the wavelength, but they ARE affected by objects that are larger then the wavelength. We use this principle on tuning the reflective surfaces in rooms, but it also applies to speakers. Waves produced by the speaker that have a wavelength larger than the smallest dimension of the speaker baffle, WILL wrap around behind the speaker, but waves that are smaller will not.

So what if we put a much bigger baffle on the speaker? Well, that would move the "change over" frequency down the scale. That larger baffle would force waves of a lower frequency to go forward into the room, because it blocks the from going backwards. And if we put a REALLY large baffle on there? Then you could keep ALL of the waves going forward, and not allow ANY of them to go backward. If you do that, it is called a "soffit"... Actually, it's called an "infinite baffle", and it would have to be very large, depending on how low the speaker goes. If the speaker produces sound down to 100 Hz, then a baffle 11 feet wide would keep all the sound going out, stopping it all from going back. But if the speaker goes down to 30 Hz, then the baffle would have to be 38 feet wide. Putting a 38 foot wide baffle on each speaker is going to be a bit difficult in a small room!

On the other hand, if you made the left baffle blend into the left wall, and into the front wall, and into the right baffle, which also blends into the right wall... then you have one hell of a baffle! Adding in the side walls as well, it actually is feasible to get a very wide baffle, even in a small room.... if you do it right. There are some tricks that can help, too. Such a wall would, in fact, keep all of the frequencies in the room, projected forward. And since the speaker itself is INSIDE the wall with just the face coming through to be flush, then any sound that DOES happen to go backwards inside the soffit... well, it just stays inside the soffit! It can't get out, so it stays there and dies.

So even if you can only make your baffle a few feet wide, you can get a drastic improvement in the low end: it gets very tight, very even, very smooth. Here's an example of such a room, and you can see the bass results for yourself, in the graphs from the acoustic analysis: thread about Studio Three Productions' control room. Here's another one that is currently under construction, thread about Steve's high-end control room in New Orleans, and there's some comments in there by the owner, regarding how he was blown away by the bass clarity... and the room isn't even finished yet!

Both of those have soffit-mounted speakers, and both are based on the RFZ design principle. You can see that it works.

And in reality, depending on construction, I suspect the lowest of lows are going to either go straight through your walls and carry on out into the outside world, or a certain amount will be attenuated, and some will be slowed down and then reflected back in to the room after being delayed etc.

Nope! Not if you build your walls and soffits correctly!

1. What is the frequency range we need to be concerned with when trying to deflect early reflections in a reflection free zone?

All of it! However, human hearing starts losing its directional sense in the very low frequencies, so it isn't really necessary to build walls 50 feet wide and high, to reflect the entire spectrum. The general recommendation is that the width of the baffle should be at least three times the diameter of your low frequency driver. In other words, if you have a speaker with an 8" woofer, then you want the soffit baffle to be at least 24" (60cm) wide. Wider is better.

Consider that if the cabinet of your speaker is 10 inches wide, then frequencies below about 1,350 Hz are already able to wrap around, since the wavelength of 1,350 is 10 inches: anything lower than that can potentially wrap around behind it. But if your baffle is 4 feet wide, then you drop that drastically to 280 Hz: everything about 280 Hz has a wavelength that is too short to wrap around the baffle.... That's a huge jump!

In theory, if you have the frequency dispersion charts/data of your monitors then you can work out the angle of that cut off frequency which will enable you to accurately work out what angle(s) are required for your RFZ, in order to meet the standard (if there is such a thing)

To a certain extent, yes... sort of.... But it's better to assume that you just need to make the baffle as wide as you possibly can, so it goes as low as possible... hence, blending the soffits and walls together, into one huge baffle... It is quite feasible that, in a well designed RFZ room, the baffle can appear (from the speaker's point of view) to be 20 feet wide... thus covering down to 56 Hz... but even then below that, the wave still cannot wrap around behind the soffit, because there is no place for it to get in! It's all one solid surface.

2. Would it not be better to have a RFZ which is capable of reflecting the ray like frequencies but at the same time attempting to absorb the rest?

Why? If the baffle is big enough, then ALL the frequencies are "ray like" to a certain extent!

One method for testing the response of speakers is to bury them in the ground outside, facing up towards the sky, so that the really do have an "infinite baffle" around them: dozens of feet in any direction. All of the sound goes out into the hemisphere in front of the speaker. None of it goes behind, because Planet Earth gets in the way....

OK, I'm simplifying and exaggerating a little: Yes, lower frequencies do still tend to spread out across the baffle, while higher frequencies do still project out more like waves.... But the point of an RFZ design is to keep ALL the direct sound heading towards your head alone, at all frequencies you can manage, and any sound that would have been reflected off the side walls pack to your head should instead be reflected towards the rear wall, where it can be attenuated and diffused, before eventually arriving at your ears again, as a more or less diffuse field.

I know that is how a lot of people seem to design their RFZ on here, but it seems that the trademarked RFZ concept does not... it relies purely on hard rigid geometry at the front, with absorption and diffusion at the rear.

If the front end of the room does not reflect sound around the mix position to the rear for absorption and diffusion, then it isn't true RFZ! Because that's what RFZ means! You can't realistically create an RFZ by using absorption alone: You can only do it by angling surfaces appropriately at the front of the room, such that all reflections go past the mix position to the rear side walls and rear wall, where they are reduced in intensity, delayed, and hopefully diffused as well, if possible. That's what RFZ is. Take a look at those two threads that I linked you to: those are both variations on the RFZ concept. Both have hard, solid, rigid surfaces at the front of the room, angled to direct reflections away from the mix position.

Most of John's studios are RFZ based. Most of mine are too. Why? Because it works! Once you experience the results of a properly implemented RFZ room, you'll appreciate just how well it works.


- Stuart -

[Paulus87]

Thank-you Stuart.

The thing is, when I look at John's designs as well as designs from other notable designers the RFZ seem to only work with monitors that have a very limited dispersion, out to about 30 degrees either side of the centre....

I'm sure you're very familiar with these designs, but to illustrate my point...

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

All of those plans have a very sharp knee between the speaker soffits and the angled side walls. There are other designers that use a similar shape to this as well and it is confusing me, which made me think 3 things; either the monitors installed have a very narrow dispersion, or the designers are not worried about first order reflections arriving at the listening position if they arrive 20db down and 20ms after the direct sound.... but as you said there should be NO first order reflections arriving at the listening position. Or the designers are only worried about deflecting first order reflections over a limited frequency range, and are not worried about frequencies below that.


If you ray trace any of those designs out to more than 60 degrees dispersion you will see first order reflections all over the place. I know they are mainly for illustrative purposes, but even if you look at John's more detailed plans, the control room shape and angles are the same. Now John has infinitely more experience and wisdom then me when it comes to control room design, so how come these designs work well are regarded as RFZ if there are reflections all over the listening position?

Paul

[Soundman2020]

The thing is, when I look at John's designs as well as designs from other notable designers the RFZ seem to only work with monitors that have a very limited dispersion, out to about 30 degrees either side of the centre....

I'm not sure why you got that impression! The speakers in the Studio Three Productions control room are Eve Audio SC-407's, which use the AMT type tweeter: it has VERY wide dispersion: way wider than typical dome tweeters. At 60° off-axis, the level is the same as on-axis. 70° off-axis the level is only -2 dB at both 1 kHz and 5 kHz. Even out at 80° it is only -4 dB. And yet, you can see the results we got in that room.

In Steve's room, those are JBL LSR-32's. At 30° off-axis, they are only down about 2 dB, full spectrum. I couldn't find the data I originally had for larger angels, but IIRC it was somthing like -6dB at 60°. In any case, 2 dB down at 30° suggests they go way wider than that.... There's plenty of energy at most frequencies heading out at 40°, 50°, 60° and more.

So no, it isn't true that designs only use speakers with narrow dispersion. I'm not sure where you got that idea from! When I design a room, I do take the speaker into account, of course... In fact, that's where I start! Since the only reason why the CR exists at all is because of the speakers, my philosophy is to design the room around the speakers, as far as possible. So yes, I do consider the polar pattern of the speakers, and the frequencies I'm likely to encounter at high angles: that's all part of the design process.

All of those plans have a very sharp knee between the speaker soffits and the angled side walls.

Correct. How else would you create an RFZ in a small room?

In a large room, there is often the luxury of using other angles, but for a small room, you don't have a lot of choice. You are stuck with whatever angle you can get.

either the monitors installed have a very narrow dispersion,

Not true: see above. I have done many RFZ rooms with speakers that have rather good off-axis response, way beyond 30°.

or the designers are not worried about first order reflections arriving at the listening position

Also not true: In an RFZ room, the early reflections are directed past the mix position wherever possible, or dealt with in other ways if the room dimensions don't allow it.

Or the designers are only worried about deflecting first order reflections over a limited frequency range,

Not entirely true either. We do try to handle as much of the range as possible, sending all of it past the mix position. But you do have to understand that small rooms impose limits on what can be done. The rooms you linked to were designed by John many, many years ago, and specifically for typical small home studios, in garages. Those are also only conceptual plans, not detailed plans. In an actual room, the angles would be adjusted to properly create the RFZ, and additional steps taken if necessary.

The smaller the room, the harder it is to make it work, but that doesn't mean that it is impossible....

If you ray trace any of those designs out to more than 60 degrees dispersion you will see first order reflections all over the place.

Like I said: they are concept designs, not detailed designs. John also did those a long time ago, and if you take a look at his more recent designs, you'll see that they have evolved... he does some things differently today. Acoustic science has advanced over the years, and continues to advance. Maybe 20 years from now RFZ will no longer be the best design: there might be something better. But right now, it's the best thing out there.

so how come these designs work well are regarded as RFZ if there are reflections all over the listening position?

There are ways of dealing with that. In Steve's room, right now they are building some devices that I designed for the side walls that will deal with that type of issue. Since the room isn't quite wide enough to help the angles I wanted originally, I went with a different angle and added treatment to deal with it. When he posts the updated photos in a couple of weeks, I'll add some results from REW tests so you can see how that worked out. In the other example I gave you, you can also see treatment on the side walls, but that isn't related to reflections: That room is wide enough that I could avoid reflections right form the start. In that room, the side wall panels do various things that were needed to get tame the room acoustics. They are not all just plain absorption panels: the maroon fabric hides all the real secrets, inside the panels....

I guess my question to you is simply this: If you don't soffit-mount your speakers and angle the baffles and wings accordingly, then what do you plan to do? How else would you prevent early reflections from getting to the engineer's ears with the first 20ms or so (ideally 30ms)? You can't do successfully it with absorption or diffusion, and having the speakers in the room introduces all those ugly artifacts that flush mounting prevents... so if you don't do that in your room, what do you plan to do to achieve the same goal?


- Stuart -

[AVare]

not worried about first order reflections arriving at the listening position if they arrive 20db down and 20ms after the direct sound

Close. The AES, EBU, ITU Alphagetti spec is that sounds in the first 15 ms be down at least 10 dB. Looking at the control rooms in the link you provided, 2 of the 3 control rooms meet that criteria without needing any detailed scale on the drawings.

Andre

[Paulus87]

Thank-you both Stuart and Andre, it is a privilege to be continuously learning.

Thanks to a combination of your answers and after actually reading the official documentation again properly, I found the answers I was looking for:

EBU Tech - “Early reflections are defined as reflections from boundary surfaces or other surfaces in the room which reach the listening area within the first 15 ms after the arrival of the direct sound. The levels of these reflections should be at least 10 dB below the level of the direct sound for all frequencies in the range 1 kHz to 8 kHz.”

ITU-R BS.1116-3 "Early reflections caused by the boundary surfaces of the listening room, which reach the listening area during a time interval up to 15 ms after the direct sound, should be attenuated in the range 1-8 kHz by at least 10 dB relative to the direct sound.”

The Dolby standards also require all early reflections within 15 ms of the direct sound to be at least 10 dB below the direct sound level over the frequency range 1 kHz to 8 kHz.

So as Andre has said, with the above in mind, John's designs can easily satisfy the required spec without the need for soffit wings. Because John usually uses slats on the side walls, I have come to the conclusion that they are angled just enough to avoid flutter.

However, in my mind, if all first order reflections at all frequencies can be avoided using geometry then this seems optimal, and goes above and beyond the required standards. If you have the space to do it, then why not? I would have thought it be a good thing to achieve. And I agree with Stuart, it makes sense that first order reflection control should be full spectrum - not restricted to a limited range.

Other than what has been said by Stuart in this thread and perhaps other threads, I have not found any documentation that states NO first order reflections should be heard at the mix position, I am sure it exists but I am yet to find it.

To answer your question Stuart, I am planning to do exactly that - flush mount my monitors and control all first order reflections with geometry and diffusion. The reason for starting this discussion was to increase my knowledge and put my mind at ease. Learning about Acoustics and studio design is something I can't get enough of, and the more I learn, the more I realise how little I know

Paul

[AVare]

Other than what has been said by Stuart in this thread and perhaps other threads, I have not found any documentation that states NO first order reflections should be heard at the mix position, I am sure it exists but I am yet to find it.

Is this some form of Welsh humour that I am not familiar with? First, you detailed several documents and quoted from them in the post I am replying to.

Second, as one who is learning acoustics, you should know by now by now terms like "should be heard" are not used when possible and dB are used to specify levels.

Andre

[Paulus87]

Other than what has been said by Stuart in this thread and perhaps other threads, I have not found any documentation that states NO first order reflections should be heard at the mix position, I am sure it exists but I am yet to find it.

Is this some form of Welsh humour that I am not familiar with? First, you detailed several documents and quoted from them in the post I am replying to.

Second, as one who is learning acoustics, you should know by now by now terms like "should be heard" are not used when possible and dB are used to specify levels.

Andre

The documents say that first order reflections should be at -10db 15ms after the direct sound. Stuart has said that no first order reflections (regardless of db level or time delay) should be at the mix position.

Paul

[AVare]

However, in my mind, if all first order reflections at all frequencies can be avoided using geometry then this seems optimal, and goes above and beyond the required standards. If you have the space to do it, then why not? I would have thought it be a good thing to achieve. And I agree with Stuart, it makes sense that first order reflection control should be full spectrum - not restricted to a limited range.

Why? You are getting into a dead end. Read the linked BBC RD document. I suggest you save the RD/PUBS URL as it is a goldmine of data.

http://downloads.bbc.co.uk/rd/pubs/reports/1995-05.pdf

Where did the "full spectrum - not restricted to a limited range" come from? Keeping to the short, as written in EBU 3276 the reconnendations, if followed as much as possible, will guarantee a good room in mostly economically justifiable spaces. In other words it is realistic compromises for a great room. Lower frequency for initial reflection control, greater time and depth (like the 20/20 you wrote earlier) are some of the compromises.

I do not where to put his topic for all to use so it is here. How is your acoustics library going? If you do not have it google Rose Acoustic Practice. It is old but details BBC first class acoustic deign and is free!

Andre

[AVare]

The documents say that first order reflections should be at -10db 15ms after the direct sound. Stuart has said that no first order reflections (regardless of db level or time delay) should be at the mix position.

Thank you for the clarification.

I think we are having a difficulty from paraphrasing. If you thin about it for a moment, there will always reflections that come first, AKA initial reflections. Being inaudible could mean several things. See the attachment for the ranges and perceptions level versus time.

Enjoy

Andre

[Soundman2020]

The documents say that first order reflections should be at -10db 15ms after the direct sound. Stuart has said that no first order reflections (regardless of db level or time delay) should be at the mix position.

I'd suggest that you look into the science of pscyho-acoustics a bit, to understand how our ears and brains actually interpret sounds, and why those documents mention 15ms / -10 dB. There's a "time window" regarding the arrival of reflections after the direct sound, and if the reflection arrives strongly within that time window, then it messes with your ability to accurately determine direction. The time window is listed as anywhere between about 15 ms and 80ms (depending somewhat on the research and how it was done), but it also depends on the LEVEL of the reflection. If the reflection is a lot quieter than the direct sound, then it doesn't really matter. So a reflection that arrives at your ears at -60 dB isn't going to affect your hearing very much at all, even if it arrive very early. -10 dB is subjectively about half as loud as the original sound, but objectively the sound has lost 90% of its power. A 90% reduction in power is 10 dB drop. So a reflection that arrives at -10dB has lost most of it's intensity already. A specular reflection arriving at your ears from a hard, angled surface will NOT have lost 90% of it's energy, and it WILL be within less than 15ms, for sure.... unless the room is large. In order for a reflection to arrive 15ms later than the direct sound, it must have traveled a path about 15 feet longer than the direct sound. So unless your room is quite wide, and the side walls are quite far away from the mix position, the early reflection will arrive within less than 15ms. And if the surfaces are hard, then the level will be greater than -10dB.

So yes, that's what I mean when I say that you want to avoid ALL first order reflections: Obviously, it is impossible to stop absolutely every reflection: attaining 100% perfect absorption in real life is pretty much impossible: you cannot get a level of -90 dB, nor even -50 dB realistically (nor do you want to!). -10 dB is already 90% less energy.

So the goal is to prevent anything from arriving within LESS than 15ms, and/or at a level GREATER than -10 dB. And yes, ITU and EBU do mention the critical range as being 1k to 8k, but in reality for most speakers, that range happens far off-axis, not just in a range of 30° off axis. Take a look at the polar plots or dispersion diagrams for common studio monitors, and you'll notice that the majority show plenty of energy in that range at off-axis angles greater than 30°.

In fact, if you look at some other specs, they go further, and suggest -20 dB / 20ms. -20 dB implies 99% reduction in power.

In fact, the specs are more complex than that: Some design specs mention a concept caller the "Initial Time Delay Gap", and they want "no sound at all" arriving within that window (which might be 15ms, or 20ms, or something else, depending on the spec), then that ITDG is followed by a diffuse sound field that must be -20 dB down (or -10, or whatever). Obviously, the "no sound at all" needs qualifying too: It doesn't mean absolute dead silence 0 dB SPL! I don't recall the actual spec, but it's very significantly quieter than the direct sound, and also significantly quieter than -20.

Andre is right: I should be more careful about using words like "all" without qualifying them. I think the above qualifies what I mean by "all reflections". Obviously, it is impossible to completely eliminate "all" reflections in a typical room that has typical boundaries around it: even anechoic chambers still have some reflections, just at an extremely low levels. When I say "all", I mean all of the reflections that are of concern psycho-acoustically. A reflection at -60 dB is not of great concern to me, regardless of frequency! A reflection at -3 dB certainly is.

As Andre said, it would be good if you do some more research to see what the specs actually mean, and how they might affect your room, and what you can do about it, realistically.


- Stuart -

[Paulus87]

Andre and Stuart,

Thank-you both for taking the time to read through my queries, It seems we are now all in agreement and I am no longer confused. The whole reason I was so confused in the first place is because of Stuart's reply to one of my earlier posts:

Is the criteria for a RFZ simply that any early reflections being deflected off of any surface must reach the listener no sooner than 20ms after the direct sound and attenuated by -20? And as long as that happens the RFZ is effective?

Those are two different pars of the RFZ concept. The first part is that NO first-order reflections arrive at your head. Ever. Nothing. ALL first order reflections are re-directed to the rear of the room, where they are both diffused and absorbed, to create the "diffuse field". That diffuse field must not get back to your ears until at least 20m2 after the direct sound got there, and when it does it should be about 20 dB lower than the direct sound, sustained for a short time if possible, and then decay smoothly and evenly at the correct rate for the room size, with all frequency bands decaying at the same rate, +/- 0.05s

I read that to mean that the "20/20" rule does not apply to first order reflections, but only higher order reflections, and that first order reflections must be deflected regardless of db level and time delay.

My next question then: Is it desirable to go above and beyond the recommended specs of 15ms at -10db, or 20ms at -20 etc if you have the space? I ask because I see rooms designed by people like Wes Lachot or Vincent Van Haaf where the rooms are very large to begin with, the side walls already being far enough apart to meet spec and yet they still angle them out at 30 degrees or more. What is the benefit of this?

To answer your question Andre, my library consists of most of the classics "Build it like the pros", "MHoA", "Acoustics absorbers & diffusers", Newell's "Recording studio design" & "Recording spaces", Roger D'arcy's "Recording Architecture", as well as a lesser known one called "Small Budget Recording Studios" Currently reading the BBC document regarding the CID environments, thanks for sharing Andre.

Paul

[AVare]

Andre and Stuart,

Thank-you both for taking the time to read through my queries, It seems we are now all in agreement and I am no longer confused.

You are welcome.

My next question then: Is it desirable to go above and beyond the recommended specs of 15ms at -10db, or 20ms at -20 etc if you have the space? I ask because I see rooms designed by people like Wes Lachot or Vincent Van Haaf where the rooms are very large to begin with, the side walls already being far enough apart to meet spec and yet they still angle them out at 30 degrees or more. What is the benefit of this?

Not beyond 20/20 minimums.

The splaying has nothing to with initial reflections if the room large enough. If it is large enough that means the width is at least 6 m and flutter echo requires addressing.

To answer your question Andre, my library consists of most of the classics "Build it like the pros", "MHoA", "Acoustics absorbers & diffusers", Newell's "Recording studio design" & "Recording spaces", Roger D'arcy's "Recording Architecture", as well as a lesser known one called "Small Budget Recording Studios" Currently reading the BBC document regarding the CID environments, thanks for sharing Andre.

Nice library. Here is a link to Rose.

http://downloads.bbc.co.uk/rd/pubs/arch ... actice.pdf

Enjoy

Andre

[DanDan]

An offside addition. Ed here is a great builder, of everything. Even those ATC copies, Preamps, everything. I'll bet he has a few locally interesting tips.
http://www.giantwafer.com
DD