I'm going to make some sound traps for my studio...

frobisher

I know there's a huge amount of info out there on t'net. Has anyone here built their own traps? Got any advice or knowledge on the various rockwool type products available in Ireland, both the common builder stuff and maybe the more audio specialised stuff too?

shayleon

Most of my traps are DIY. Rockwool from ATIL in Dublin. Think it was high density type. Don't forget to spray it lightly with PVA. I then used chicken wire to hold it in place.
cheers.
Shay.

PaulBrewer

I take it we're talking Bass Traps in a small(ish) room?

The problem with rockwool traps is in order for them to 'reach' down to a low frequency a huge amount is needed.

Huge equals using up room real estate - not an option in a smallish room.

The wavelength of 100 hz for example is 3.43 metres. 40hz is 8.58 m.

I believe a quarter wavelength is used to determine the depth necessary so for rockwool to work to 100hz , (which I'd consider the mid of the bass band) one would need .8575 meters deep.

If you wanted to reach 'actual' bass, which is around the low E string of a bass guitar and would cover a large percentage of the used frequency band (probably only a kick would reach down much further in a standard rock band) you'd need rockwool traps of at least 2.145 Metres thick to work.



Say one used a corner max depth of 30cm, about 1 foot it's effective average depth would be 15cm (deepest 30cm/shallowest 0 average =15cm)

If .15 metre is the quarter wave length then the full wavelength is .6 metres or about 572 Hz ..... no where near Bass.

If you take 2 feet deep off each corner of your room it's average is 1ft that still only leaves you at 286 Hz .... still no where near bass... and that's coming out along the wall 2.82842712 feet from each corner.


A practically useless route to take if the science is to be believed ?

Another downside is that having failed to treat your bass you've also introduced a lot of high mid absorption as rockwool is very good at that. So you've skewed your RT even more in favour of bass.

A superior solution in my opinion is a tuned dampened membrane absorber that can reach down to below 40hz and yet be only about 8 inches deep.

How they work is the 'membrane' part is mdf dampened with U5 barrier material with the length and cavity depth determining the frequency about which they work.

This can also be combined with foam to make a 'full range' absorber.
Melamine is the preferred choice as it's easy to work with, has a class A fire rating and does the job!

They're reasonably easy to build but know how and accuracy is necessary.


Old Engineering Wives Tales don't cut it if you're serious.

I should reiterate that I'm only going on recall regarding the 'quarter wavelength' and 'average depth' part of my post but I do know men with superior qualifications in the area to whom I'll send this post.

If they care to reply I'll post it here (once I don't come out of it lookin an eeejit!)

henessjon

can you advise if some is better than nothing ( for my 2x4 control room)


bearing in mind ****z in = ****z out :rolleyes:

ICN

PaulBrewer wrote: »

..What you said..

Hi Paul,

Hope you dont mind - Its something thats on my longest finger to do..

U5 - I'm wondering if thats the Spec of the Materials Absorbency? And what would be suitable to use for this?

And -

The Trap is tuned - Is that to the Room? or simply within itself?

I've seen some formulas out there, but my U factor is low LOL

So if thats correct - If One were to make a BT to absorb "X Freq" - then this would absorb this particular Freq in any room (but depending on size you would need a larger or smaller quantity of them?)


I had to pick something up from one of the corners of my room the other day (The Cleaner had a 1/2 Day). There was Music playing - not crazy loud by any means.. and when I put my head down, the whoomp of the bass was all I could hear.. Felt like I was being mugged! :pac:

studiorat

ICN wrote: »

Hi Paul,


The Trap is tuned - Is that to the Room? or simply within itself?

I've seen some formulas out there, but my U factor is low LOL

So if thats correct - If One were to make a BT to absorb "X Freq" - then this would absorb this particular Freq in any room (but depending on size you would need a larger or smaller quantity of them?)

If I may...
The trap is tuned within it's self to the particular frequency. If the trap is moved from the room it will still absorb that frequency ya see?

Be careful of the formulas online, there's a dodgy formula for Helmholtz resonators floating around the net. It was on the SAE site, basically it's a multiplies sign instead of a plus. This typo however has spread 'round the net like a dose of something because people don't check what they read online.

There's another problem you've brought up here too ICN is that it doesn't really work like that. Apparently, if you start to introduce more boxes into an array, they actually start to affect each other's absorbtion coefficent and the bandwidth of the absorbers.

frobisher

PaulBrewer wrote: »

I take it we're talking Bass Traps in a small(ish) room?

The problem with rockwool traps is in order for them to 'reach' down to a low frequency a huge amount is needed.

Huge equals using up room real estate - not an option in a smallish room.

The wavelength of 100 hz for example is 3.43 metres. 40hz is 8.58 m.

I believe a quarter wavelength is used to determine the depth necessary so for rockwool to work to 100hz , (which I'd consider the mid of the bass band) one would need .8575 meters deep.

If you wanted to reach 'actual' bass, which is around the low E string of a bass guitar and would cover a large percentage of the used frequency band (probably only a kick would reach down much further in a standard rock band) you'd need rockwool traps of at least 2.145 Metres thick to work.



Say one used a corner max depth of 30cm, about 1 foot it's effective average depth would be 15cm (deepest 30cm/shallowest 0 average =15cm)

If .15 metre is the quarter wave length then the full wavelength is .6 metres or about 572 Hz ..... no where near Bass.

If you take 2 feet deep off each corner of your room it's average is 1ft that still only leaves you at 286 Hz .... still no where near bass... and that's coming out along the wall 2.82842712 feet from each corner.


A practically useless route to take if the science is to be believed ?

Another downside is that having failed to treat your bass you've also introduced a lot of high mid absorption as rockwool is very good at that. So you've skewed your RT even more in favour of bass.

A superior solution in my opinion is a tuned dampened membrane absorber that can reach down to below 40hz and yet be only about 8 inches deep.

How they work is the 'membrane' part is mdf dampened with U5 barrier material with the length and cavity depth determining the frequency about which they work.

This can also be combined with foam to make a 'full range' absorber.
Melamine is the preferred choice as it's easy to work with, has a class A fire rating and does the job!

They're reasonably easy to build but know how and accuracy is necessary.


Old Engineering Wives Tales don't cut it if you're serious.

I should reiterate that I'm only going on recall regarding the 'quarter wavelength' and 'average depth' part of my post but I do know men with superior qualifications in the area to whom I'll send this post.

If they care to reply I'll post it here (once I don't come out of it lookin an eeejit!)

One day someone will post something that you will agree on in great detail Paul. I can't bleedin' wait :-)

It's not the bass I'm after. I'm not after an ultra tuned room, I just swapped rooms in the house for my studio and this one has da-ding in the high mid that the other one didn't. I want to get rid of it. So I'm going to make some traps. It's not a question of needing to either get it 100% right or not be bothered, it's about getting as much improvement as I can worth what I have. Knowarra mean?

artvandulet

I seem to remember there being a trick involving wavin pipe and sand.
You cut the pipe to a certain length to get rid of a particular frequency - based on a formula, fill it with sand -block the ends obviously - and hang it from your ceiling.
Someone else might tell you more

frobisher

artvandulet wrote: »

I seem to remember there being a trick involving wavin pipe and sand.
You cut the pipe to a certain length to get rid of a particular frequency - based on a formula, fill it with sand -block the ends obviously - and hang it from your ceiling.
Someone else might tell you more

Wow. Sounds interesting. Paul's right about one thing in this area, there can be a lot of snake oil about. I think it's a cross over from the whacky world of audiophiles that buy covers for the electrical plug sockets so the room sounds better. I kid you not.

I can only imagine some fairly low end as having enough energy in the to move sand inside a sealed Wavin piping. And at those levels I can't see whole lot of absorption. Got a link to any info on it?

PaulBrewer

frobisher wrote: »

it's about getting as much improvement as I can worth what I have. Knowarra mean?

That's the sort of attitude that has the country in the state it in! :eek:

PaulBrewer

ICN wrote: »

B]U5[/B] - I'm wondering if thats the Spec of the Materials Absorbency? And what would be suitable to use for this?

I think it's generic limp plastic like substance. In this instance, as I understand, if your tuned absorber is a bass drum the U5 works as a pillow against that bass drum.
So the Mdf sealed box is tuned to a specific frequency centre and the U5 dampens that i.e turns the energy into heat so the bass effectively goes into the box and instead of coming out again as a reflection it comes out as heat.

The Trap is tuned - Is that to the Room? or simply within itself?

Both I guess . It's tuned to itself insofar as it'd designed to focus on a particular band. The Bandwidth or Q is adjustable by design i.e you plan it to do a job.
That would be dependent on room measurement.

I've seen some formulas out there,

It seems to me from what I've seen working with proper dudes that the maths side ain't for the faint hearted - which may explain my experience of a lot of rooms being pants both here and the UK.

If One were to make a BT to absorb "X Freq" - then this would absorb this particular Freq in any room (but depending on size you would need a larger or smaller quantity of them?)

I believe that to be true - but I have no understanding (yet!) of how one decides how much shizit is needed. As the Rat says everything 'interferes' with everything else. It takes wise men to make it all work, in my experience.

I

had to pick something up from one of the corners of my room the other day (The Cleaner had a 1/2 Day). There was Music playing - not crazy loud by any means.. and when I put my head down, the whoomp of the bass was all I could hear.. Felt like I was being mugged! :pac:

I still don't understand why bass likes corners, but it does. That's why bass treatment gets put there - because it's there it's most effective.

PaulBrewer

artvandulet wrote: »

I seem to remember there being a trick involving wavin pipe and sand.
You cut the pipe to a certain length to get rid of a particular frequency - based on a formula, fill it with sand -block the ends obviously - and hang it from your ceiling.
Someone else might tell you more

How much is a wavin pipe filled with sand going to weigh? Then hang it from the ceiling ?

Let us know how you get on !!

PaulBrewer

frobisher wrote: »

One day someone will post something that you will agree on in great detail Paul. I can't bleedin' wait :-)

It's not the bass I'm after. I'm not after an ultra tuned room, I just swapped rooms in the house for my studio and this one has da-ding in the high mid that the other one didn't. I want to get rid of it. So I'm going to make some traps. It's not a question of needing to either get it 100% right or not be bothered, it's about getting as much improvement as I can worth what I have. Knowarra mean?

What you need is a bit of rock wool ..

ICN

studiorat wrote: »

If I may....

Excellent SR. The last thing you need is wrong info.. Very true!!

ICN

PaulBrewer wrote: »

I think it's generic limp plastic like substance. In this instance, as I understand, if your tuned absorber is a bass drum the U5 works as a pillow against that bass drum.
So the Mdf sealed box is tuned to a specific frequency centre and the U5 dampens that i.e turns the energy into heat so the bass effectively goes into the box and instead of coming out again as a reflection it comes out as heat....

Cheers Paul..


So is U5 is the actual Product/Brand?

frobisher

PaulBrewer wrote: »

What you need is a bit of rock wool ..

Exactly what I was thinking. Which is why I'm wondering if anyone here has experience with it to share with me on doing the same thing.

frobisher

PaulBrewer wrote: »

I still don't understand why bass likes corners, but it does. That's why bass treatment gets put there - because it's there it's most effective.

Maybe that's why so many studios have corner sofa units, like mine does :-) Great trap AND comfy!

PaulBrewer

frobisher wrote: »

Maybe that's why so many studios have corner sofa units, like mine does :-) Great trap AND comfy!

PaulBrewer

Just got a reply from Chris Walls Senior Acoustician with Andy Munro, acoustic designers office re my pontification ....
Chris has designed Mark Knopfler's British Grove Studio and U2's new Dublin recording room.

"Porous absorbers, like Rockwool, work on the velocity component of a sound wave* which is always zero at a room boundary and therefore a maximum a quarter wavelength from a boundary. The quarter wavelength relates to the thickness at which an absorber would be theoretically 100% efficient (i.e. absorb all incident sound).

100mm Rockwool will absorb sound energy below its quarter wavelength frequency (400Hz) but will not be terribly efficient, perhaps 30% at 100Hz. The problem, as you point out, is that it will absorb nearly 100% of incident energy at mid and high frequencies. Using this approach you generally end up with near anechoic mid & high end and a wildly uncontrolled low end. Most of the studios I've seen in Ireland exhibit these characteristics.

Using Helmholtz or limp mass membrane absorbers allows you to absorb low frequencies efficiently without taking up huge amounts of floor space and without killing the mids and highs. It's not complicated to do, it just requires a bit of know how. There's plenty of literature on the theory, and the BBC Guide to Acoustic Practice (free to download) gives some designs together with absorption data. Well worth a look.

* Limp mass membrane absorbers work on the pressure component of a sound wave, which is why they work at a room boundary. "

Here's the link -

http://downloads.bbc.co.uk/rd/pubs/archive/pdffiles/architectural-acoustics/bbc_guideacousticpractice.pdf

fitz

This is turning into quite an educational thread...

madtheory

frobisher, if you build the simple mid/ hi range traps (which is what you described in your OP), it's very easy to convert them for bass trapping, you just put a membrane on the front, i.e. use 1/4-inch plywood to absorb the deepest bass frequencies and 1/8-inch plywood and for the upper bass range. See here:
http://www.ethanwiner.com/basstrap.html

Paul- thanks for the BBC pdf! In return, here's Ethan Winer's brilliant guide:
http://www.ethanwiner.com/acoustics.html

It's actually pretty easy to achieve a 50% improvement in the room response, and it's cheap too. You'll never get it ruler flat, but it's amazing how much easier it is to mix with even a 50% improvement. You realise that your brain does a lot of compensation work! It's a lot less tiring to mix in a treated room.

Rooms that have stud partitions tend to act as bass traps. But you have to measure the room response. This is a great tool:
http://www.hometheatershack.com/roomeq/

So you have to keep measuring the room response, put in traps, measure, move them around, and keep tweaking until you get it as flat as humanly possible. It's cheap and edcuational

PaulBrewer

madtheory wrote: »

frobisher, if you build the simple mid/ hi range traps (which is what you described in your OP), it's very easy to convert them for bass trapping, you just put a membrane on the front, i.e. use 1/4-inch plywood to absorb the deepest bass frequencies and 1/8-inch plywood and for the upper bass range. See here:
http://www.ethanwiner.com/basstrap.html

Paul- thanks for the BBC pdf! In return, here's Ethan Winer's brilliant guide:
http://www.ethanwiner.com/acoustics.html

It's actually pretty easy to achieve a 50% improvement in the room response, and it's cheap too. You'll never get it ruler flat, but it's amazing how much easier it is to mix with even a 50% improvement. You realise that your brain does a lot of compensation work! It's a lot less tiring to mix in a treated room.

Rooms that have stud partitions tend to act as bass traps. But you have to measure the room response. This is a great tool:
http://www.hometheatershack.com/roomeq/

So you have to keep measuring the room response, put in traps, measure, move them around, and keep tweaking until you get it as flat as humanly possible. It's cheap and edcuational

I've had a run in with Mr.Winer on Gearslutz.

I could not get him to answer questions I asked, repeatedly. That didn't inspire my confidence.

Seziertisch

Where does asbestos fit in in the world of acoustic treatment?

PaulBrewer

Seziertisch wrote: »

Where does asbestos fit in in the world of acoustic treatment?

No where I'd imagine! Why do you ask?

madtheory

PaulBrewer wrote: »

I've had a run in with Mr.Winer on Gearslutz.

I could not get him to answer questions I asked, repeatedly. That didn't inspire my confidence.

Have you a link? Anyway, I think it's a very good article. It's a good one to start with because he's a very good writer, makes the F Alton Everest tomes easier to digest. They're not as well written, but are more accurate and in depth technically, and show that Winer's info is sound.

Seziertisch

PaulBrewer wrote: »

No where I'd imagine! Why do you ask?

If anyone was looking for some I could sort them out with a bit from an old cow shed. Easy to work with and 100% non-hazardous ...

PaulBrewer

madtheory wrote: »

Have you a link? Anyway, I think it's a very good article. It's a good one to start with because he's a very good writer, makes the F Alton Everest tomes easier to digest. They're not as well written, but are more accurate and in depth technically, and show that Winer's info is sound.

No was about 6 months ago.

Coincidentally it came from a discussion on bass trapping where it was said that 'one can't have too much bass trapping'

I questioned that and the answer was that in order for there to be the possibility of too much (of which there can be) there'd be no room in a small room.

This may well be the case using a porous bass trap as Mr Winer's company RealTraps make.

However when I asked about Limp Mass Membrane Absorbers all went quiet for a while, until I then got attacked by other people, presumably for questioning .....

Left a very bad taste in my mouth.

madtheory

Could be you were asking a question that comes up a lot...

ICN

PaulBrewer wrote: »

....However when I asked about Limp Mass Membrane Absorbers all went quiet for a while, until I then got attacked by other people, presumably for questioning ......

Sounds like a Trap to me... Groan! :D:D:D

PaulBrewer

madtheory wrote: »

Could be you were asking a question that comes up a lot...

Seemed to me I was asking a question that didn't suit ...:rolleyes:

PaulBrewer

madtheory wrote: »

frobisher, if you build the simple mid/ hi range traps (which is what you described in your OP), it's very easy to convert them for bass trapping, you just put a membrane on the front, i.e. use 1/4-inch plywood to absorb the deepest bass frequencies and 1/8-inch plywood and for the upper bass range. See here:
http://www.ethanwiner.com/basstrap.html

Munro say -

'You'd get a better result using a limp mass such as revac, or 1/8" ply bonded to a barrier mat or similar damping material (I think a lot of DIY studios use roofing felt). The problem with just using ply is that it creates an absorber with a very high Q so it will absorb very effiently but at quite specific frequencies. If you dampen the vibration you broaden the Q, unfortunately at the expense of efficiency, but it gives more usable results in my opinion. You can also get an audible ringing or 'booming' from just using ply as it re-radiates sound. Again the barrier mat dampens the vibration and eliminates this effect.'

studiorat

PaulBrewer wrote: »

Munro say -
l (I think a lot of DIY studios use roofing felt).

And the BBC, they're the guys who figured out the roofing felt thing after all. (F.Alton)

I posted last night giving the equations for the tuned membrane gig. The post got lost for some reason it seems...

Frequency= 600 X Sqr.root (m.d) if I remember correctly.
M is membrane mass
D is cavity depth.

The equation is somewhat simplified and doesn't take volume into account, but by adding a porous absorber actually inside the cavity you can widen the bandwidth and make improve the absorbition coefficient of the unit.

There was a paper given at AES last year by John Storyk of Walters Storyk that concluded that none of the commercial, "tuned" absorption devices they tested were really worth a sh1te.

Now I'd like to throw a spanner in the whole works and make another recommendation, passive loudspeaker membranes can be more effective than convertional membrane systems since loudspeakers are really good at vibrating over a wide range of bandwidths, and they're damped easily. If it's cost effective to cover a wall with them is another question.

Bagend actually make an active absorber basically using loudspeaker that can be tuned as the room requires. http://www.bagend.com/bagend/ETrap.htm I reckon this is the future...

PaulBrewer

studiorat wrote: »

There was a paper given at AES last year by John Storyk of Walters Storyk that concluded that none of the commercial, "tuned" absorption devices they tested were really worth a sh1te.

.

Are there such things? Do you have examples?

Wasn't it Storyk who designed the original Windmill?

madtheory

Cool, roofing felt is as easy to acquire as plywood

PaulBrewer wrote: »

Seemed to me I was asking a question that didn't suit ...:rolleyes:

In fairness, he has answered that question several times, in detail. A search will show that.

studiorat

PaulBrewer wrote: »

Are there such things? Do you have examples?

Wasn't it Storyk who designed the original Windmill?

They weren't allowed actually mention the manufacturers, and were only allowed use examples A, B, C etc. Mainly because some of the companies attending the convention were supplying these products.

WSDG have been going 40 years, Electric Lady in New York was Storyk's first design job. Windmill was a Munro job afaik.

PaulBrewer

studiorat wrote: »

They weren't allowed actually mention the manufacturers, and were only allowed use examples A, B, C etc. Mainly because some of the companies attending the convention were supplying these products.

WSDG have been going 40 years, they did do Electric Lady in New York. Windmill was a Munro job.

I didn't know that.

I think you'll find the original Windmill was Storyk.

I just got a reply from Philip Newell regarding my pontification.

By coincidence he's just written an article for Resolution magazine on exactly the same subject Acoustics in Small Rooms.

He too agrees with Munro's points which was a surprise to me as they have what I would have thought were polar opposite approaches.

As he says -

' The latter part is pretty much in agreement with what you wrote.'

I've asked for his permission to post here but I'd expect that won't be a runner 'til after publication.

PaulBrewer

madtheory wrote: »

Cool, roofing felt is as easy to acquire as plywood

In fairness, he has answered that question several times, in detail. A search will show that.

A polite referral to those posts by him or others would have been graciously received.

However whilst he did reply to some of my posts my questions remained unanswered.

PaulBrewer

Philip Neweill has just given me permission to reproduce his article. This is a draft version of what may or may not be in next month's Resolution Magazine.

Improving the Working Acoustics in Small Rooms

For a long time now, there has been a growing tendency for sound to be recorded, edited, and even mixed in rooms which have had very little attention paid to their acoustics. All sorts of absurdities are now common, with computers being placed in control rooms, and giving rise to background noise levels of over 50 dBA at the listening position. Combine this with the siting of the rooms in complexes of other, similarly untreated rooms, and where levels of over 80 dBA would be likely to begin interfering with the work of the neighbours, and one can forget about the possibility of monitoring any reasonably high dynamic range programme.
The lack of room treatment also usually goes hand in hand with an uneven low frequency response, and these can sometimes vary very widely, not only within a room, but also from room to room. Excessive reflexion from the untreated surfaces can also spoil the stereo imaging and introduce undesirable colouration of the sound. Inappropriately placed equipment can also go a long way to undermining the monitoring reliability. When such rooms are also used for recording voices, the impacts from the foot-falls of people walking on the floor above can also be a source of ruined takes and lost time. These problems are often exacerbated by insufficient height in the rooms to allow for any remedial treatment.
Economic forces and marketing attitudes have put a lot of pressure on studios to rely on computers for a great deal of their processes. The real cost of the recording/editing/mixing equipment has fallen sharply during the last few years, even though the capabilities of the systems has risen. People have become accustommed to falling prices, but the cost of making good rooms, with good acoustics, has probably risen over the same period of time.
The considerable change in the relative cost proportions of the equipment and the acoustic works has encouraged the financial wizards to decide to either minimise the acoustic treatment, or to allow the sound quality to fall and to do nothing at all to the acoustics. As the competition down the road were also probably cutting costs, the quality losses were not seen to be financially important. Concurrently with this, the marketing departments of the equipment manufacturers have been working at full steam to convince people that the new equipment could effectively dispense with most of the need for good acoustics.
To complicate matters further, as people have pushed to impress their ever-less-knowledgeable clients, it has been unfortunate that acoustic work, when finished, has often neither been visible nor touchable, so its ability to astound the clients has been seen as almost zero. It would be much more impressive, in most cases, to confront the clients with something a bit more fashionable, like a new microphone, a new editing program, or a new pre-amp. Also, an increasing number of clients are now people who have had no experience in top flight studios, and they are so inexperienced about recording acoustics that they are often uncomfortable in rooms which have what were traditionally considered to be good acoustics, especially when the rooms, in conjunction with good monitor systems, revealed the awful truth about the real quality of the clients' recordings. Ignorance can be bliss! ....'But it sounded great on my mobile telephone!'
There are many pressures, nowadays, not to do any better than necessary. In other words, if it will cost more to do it better, but only a very few people will hear the benefit, then to go for better results can be merely seen as a waste of money. Nevertheless, there are many recording personnel who work in truly miserable conditions, and who would dearly love to be able to have better acoustics in their rooms. They realise that when the monitoring is coloured by poor control room acoustics, it can be hard to know if there is a clean sound entering the microphones. They also realise that the good sound of an excellent microphone can rarely, if ever, overcome the colouration from a poor room in which it may be placed.
So, what can be done in a moderate manner to help these poor souls who really are looking to do the best that they can, even if they realise that the results will not be quite like those from a truly world class facility? In fact, there are numerous ways to ameliorate the worst of the problems, but the solutions are not always obvious, and there are rarely any truly cheap fixes.
As an example, and as mentioned earlier, the intrusion of the impact of foot-falls from the floor above is a very common problem. Undoubtedly the best solution to this is to offer to pay the neighbours to fit an impact absorbing floor. Where the ceiling height is low, and a heavy false ceiling is out of the question, this may, in reality, be the only viable solution. Anyhow, once the impact noises are in the structure of the building, isolating the ceiling, from below, may only result in the noises then appearing from the walls. They only seemed to be coming from the ceiling because it was the loudest source. That is, the structural borne noise tends to radiate from all surfaces, so, short of isolating the entire room, it can be much more economical to stop the noise from entering the structure. Nevertheless, all this depends on the good will of the neighbours to allow the work to be carried out in their premises, unless the owners of the studio are also the owners of the floor above, of course.
The newer building regulation in many countries are now beginning to address this problem, but many studios are typically in older and cheaper buildings where not very much thought has been given to impact noises. In so many cases, cost and location are the prime factors in choosing buildings, and acoustic considerations are often given little importance until the contracts on the buildings have already been signed. All too often, the buildings that they choose are too small and too structurally weak to permit much acoustic work. From then on, the whole process tends to revolve around lessening the extent of the problems, rather than the creation of the desired conditions.
In relation to the internal acoustics, one useful element which can help almost any small room is a full-range absorber covering either the wall opposite the loudspeakers, in the case of a control/editing room, or the wall towards which a voice-recording microphone will face; that is, behind the actor or singer. Inevitably, these things do take up space, typically at least 60 cm of depth over the whole surface of the wall in question, but they do go a long way towards very effectively flattening a room. The general concept is shown in Figure 1. Once installed, these 'traps' tend to be like a breath of fresh air for the people using the rooms.
Some people eschew the use of so much absorption, and prefer diffusion, but in my experience, in small-to-very-small rooms, diffusers tend to change the colouration, rather than remove it. They still return the energy to the room, and it comes back very quickly in small rooms, merging with the direct sound from which it then cannot be separated. What is more, even diffusers usually need to be of the same degree of depth if they are to function down to the same low frequency limits. This is a big problem with small rooms, there is little space in which to do anything to control them, Unfortunately, the control measures depend on frequency and wavelength, and not on the size of the room that they are controlling!
Self-measuring, self-aligning monitor loudspeakers have also now become quite a popular way of flattening-out the worst of the response problems in small rooms. Nevertheless, there are a few points which must be considered about the nature of their operation before choosing them as a primary solution to a room acoustics problem. In the first instance, they may improve quite drastically the sound in a small region of a room, but they may also worsen the sound elsewhere. In the second instance, where they have D to A converters after the processing, the converters are unlikely to be of the highest standard. If we take the case of an editing/mixing room for television, and if the room is for a single operator and the downstream reproduction quality of the domestic chain is not likely to be of audiophile quality, then the use of such loudspeakers can be a good option for use in a relatively poor room. On the other hand, if we are considering mixing music for a CD, which can be expected to be heard on some excellent hi-fi systems, then the studio recording converters and the domestic reproduction converters will probably in many cases be way superior to the D to As in the loudspeakers. What is more, in music recording and mixing environments, several people may be in the room at the same time, and all may be involved in discussing the mix. In this case they all need to be hearing approximately the same sound, and so could be led into speaking at cross-purposes if the sound varied greatly from one part of the room to the other due to the spacial limitations of the loudspeaker/room correction process.
The problem with the on-board D to A converters is that if their quality is not at least as good as the converters elsewhere in the chain, they can mask the more subtle differences during the decision-making processes. This is unlikely to be a problem in the worlds of television or video, where the differences between reasonable quality convereters are very unlikely to ever be noticed. In the top end of the music industry, however, in good rooms and listening via high resolution loudspeakers, the differences even between very high quality converters can be surprisingly noticeable. Unfortunately, if the on-board D to As in a monitor system are not of comparable quality, the differences between the better converters may be undetectable. This implies that the monitor systems are not resolving that level of detail, so it can be difficult, if not impossible, to know the true level of quality of the recording.
Whether all this is important or not will depend on the standards that the recording/mixing personnel are aiming for, but even if not all are going for audiophile quality, it is still good to be aware of where the limitations exist. It seems to me that an enormous amount of professionals using such systems are totally unaware of the limitations. I have also heard many people claim that they cannot hear the benefit of many of the better converters, when the fact is that they have simply never heard them in high resolution listening conditions.
Think about the reality: if a pair of self-aligning loudspeakers cost 2,500€, the cost of their on-board converters is not likely to be much more than 30 or 40€ each. How can such converters, and through which all the sound is being judged, be expected to sound as transparent as stand-alone converters costing 50 times more?
Personally, I still like to keep monitor chains analogue, albeit of very high quality. I find that it helps me to get a much better perspsctive on the differences between the different digital parts of the process. Nevertheless, to do this removes the option for automatic room-correction, so the only solution is to revert to acoustic treatment. However, as we have already discussed, this needs space. It also tends to have little secondhand value. (But there again, nowadays, nor does much secondhand digital equipment!) The choices boil down to the importance being attached to the sound quality of the end product.
In Resolution V? and V?? there were articles about the E-Trap, which is an electroacoustic absorber, as shown in Figure 2. Such systems are capable of fixing the very worst problems below about 80 Hz, but they only appear to be capable of making a bad room usable. Nevertheless, perhaps it is unfair of me to say 'only', because making a bad room workable may be exactly what some people need, especially in temporary premises. It would be futile to install them in a room that was already quite well controlled, but if somebody was forced to work in a very lumpy room, then the E-Trap could help to make life tolerable.
Of course, another commonly seen form of treatment in small rooms is the use of various shapes and sizes of open-cell polyurethane foam sheets and blocks. So often, the application of these by relatively inexperienced people can lead to rooms which initially sound as though they are controlled, but in fact a lot of colouration can still exist, which will manifest itself in the recordings, and the rooms can still exhibit gross irregularities. Basically, any porous absorber (such as open-cell foams, and fibres) can only absorb well the frequencies whose wavelengths are less than about four times the thickness of the material. Well, at least that is the case when the material is fixed on a rigid wall. If, however, it is spaced away from the wall, the lowest frequency of reasonably good absorption will be that whose quarter-wavelength is similar to the disrtance from the outer surface of the material to the wall. In either case (thicker material, or a thinner material with an air-space behind), space in the room will be consumed. I hesitate to say that space woulds be 'lost' because the amount of floor-space in a control room is not the be-all and end-all of its function.
Just as a rule of thumb, I usually need an average of about 50 cm all round a room to bring it under reasonable control. In some parts of a room, dependent upon its use and the degree of low frequency control that is required, a metre or more may be needed. To begin with a room of 3 m x 4 m and to expect to end up with a working space of the same size is simply not realistic.
So, even foam treatments need a considerable amount of space if they are to be genuinely effective, but in so many cases thin sheets are glued to walls in the forlorn hope that a well-controlled room will be the result. In reality, all that this usually does is absorb the high frequencies. This may initially give people the impression that the room is rather dead, but the truth is that it will probably still be quite lively in the lower voice region, and the recordings, or the monitoring, will probably sound boxy and unnatural.
Even with sponge blocks in the corners of the room, they usually have too little depth over sufficient a surface area to do what many people expect of them. It is a pity that so any people now believe that a few foam sheets and blocks, on the walls, and listening at close distances via less than top-of-the-line loudspeakers, can give them almost ideal monitoring conditions.
As the industries become staffed with people who are ever more likely to be operators, rather than engineers, they aften fail to see (or hear!) the many down-sides that can be introduced when they are concentrating on the fix for one, particular problem; or when they are concentrating on the single up-side of something that they have just been sold. Perhaps with the same disgrace that now faces the 'free-market rules all' philosophy of the last 20 years or so, and the growing awareness that price and value are not synonemous, some long-lost attitudes in the recording industries will return, and a realisation will arrive that 'doing it all as cheaply as possible' is not a sustainable driving force.
The mass-marketing of products also often tends to seek the lowest common denominators, but artistry and professionalism do not sit happily with this type of philosophy. But, there again, the human race tends to be living in an unsustainable bubble at the moment, and some of the only ways that it can even be temporarily sustained are via philosophies which require ever cheaper products for ever bigger markets. The laws of acoustics, on the other hand, operate on a more Universal time scale, and involve principles that know nothing of the pressures of fashions or marketing. In the end, it is these physical laws which dictate that a great sounding, flexible-to-use studio, in a room of only 30 cubic metres (say 4 x 3 x 2.5) is something only for a wild imagination.

PaulBrewer

Mr Newell also made some corrections to my original post -

"Also, may I comment that you should be using the word 'damped', and not dampened. The first means to lose energy through resistance, the second means to make rather wet."

ICN

studiorat wrote: »

..Now I'd like to throw a spanner in the whole works and make another recommendation, passive loudspeaker membranes can be more effective than convertional membrane systems since loudspeakers are really good at vibrating over a wide range of bandwidths, and they're damped easily. If it's cost effective to cover a wall with them is another question.

Bagend actually make an active absorber basically using loudspeaker that can be tuned as the room requires. http://www.bagend.com/bagend/ETrap.htm I reckon this is the future...

Wow - Thats very interesting.. It reminds me of a Physics experiment that we used to do about Newtons 3rd Law of Motion - To every action there is an equal and opposite reaction.

Makes sense.

ICN

PaulBrewer wrote: »

Philip Neweill has just given me permission to reproduce his article. This is a draft version of what may or may not be in next month's Resolution Magazine.

Improving the Working Acoustics in Small Rooms.....

Excellent - Really enjoyed reading that.

Coincendence that he was doing it at same time.. but I suppose this issue is the bane of a lot of peoples lifes. Its always going to be affecting/effecting someone.

Not sure I'm ready to give up 50/60cm around my whole room just yet though! LOL

PaulBrewer

ICN wrote: »

Excellent - Really enjoyed reading that.

Coincendence that he was doing it at same time.. but I suppose this issue is the bane of a lot of peoples lifes. Its always going to be affecting/effecting someone.

Not sure I'm ready to give up 50/60cm around my whole room just yet though! LOL

"This is a big problem with small rooms, there is little space in which to do anything to control them, Unfortunately, the control measures depend on frequency and wavelength, and not on the size of the room that they are controlling"

That's the essence of the article in my opinion.

studiorat

Very poor article by Newell IMO. In general it is a bit vague and quite broad and very thin on useful information, it would seen to serve no other purpose than quantify his own worth as a consultant.

In fact he states that to deal with low frequencies up to 1m is needed. What happened to Munro's tuned membrane?

I thought you didn't like his work Paul? That's the guy in Spain with the crap studio right?

PaulBrewer

studiorat wrote: »

Very poor article by Newell IMO. In general it is a bit vague and quite broad and very thin on useful information, it would seen to serve no other purpose than quantify his own worth as a consultant.

I thought you didn't like his work Paul? That's the guy in Spain right?

I don't like his studios !

However I like him and the fact that we can agree to disagree and continue to discuss subjects such as this is the mark of a good soul.

The article is, as you say broad but it's an article in a magazine - not an Academic paper and should be read as such.

For more in depth information you can read his books.

PaulBrewer

studiorat wrote: »

In fact he states that to deal with low frequencies up to 1m is needed. What happened to Munro's tuned membrane?

He doesn't use them.

The point is that a Metre or more is necessary - not that that approach doesn't work.

studiorat

It's an article for Resolution magazine! Remember? The one John Watkinson writes for, very poor form. The professional one? Reads like Future Music...

PaulBrewer

studiorat wrote: »

Reads like Future Music...

I've never had the opportunity to enjoy that tome .....

What exactly are your criticisms? Are there factual inaccuracies? Or is it you 'just don't like it'.

I did also point out it's a first draft.

I'll gladly relay your observations to Mr. Newell.

studiorat

The title is "Improving the Working Acoustics in Small Rooms"

I count two solutions, two and a half if you count active monitoring which he disregards. I guess he hasn't got a suss on a good dealership for that yet. One of the problems he mentions is about foot fall from the room above. What the hell has that got to do with the Acoustics of the room? Only a complete idiot wouldn't be able to figure out how to solve that.

I wouldn't say factual inaccuracies just a certain broadness that in Resolution looks more like a badly written advertizing feature. But considering the title and the the fact that there's so few actual solutions mentioned I'd say it's more of a rant.

PaulBrewer

studiorat wrote: »

The title is "Improving the Working Acoustics in Small Rooms"

The working title .

I'd say it's more of a rant

.

Perfect for here then!

studiorat

PaulBrewer wrote: »

Perfect for here then!

In reality there's more useful information in a lot of the posts here, and not just hinted at information as in the article.

A better title might be "Why small rooms are Sh1te and only €10,000 can tell you how to fix it"

It's not even remotely amusing...

PaulBrewer

studiorat wrote: »

In reality there's more useful information in a lot of the posts here, and not just hinted at information as in the article.

Thank You.