Practical Domestic Room Acoustics

[Killahertz]

Few have the luxury of a purpose-designed, dedicated room in which to listen their hifi system. Inevitably, therefore, most systems will be used in a room that is of shared function, as well as shared occupancy. Yet shared function, even shared occupancy, need not deter acoustical treatment so vital to the qualitive reproduction of music. One simply needs to look at low to minimal impact OEM solutions and the intelligent use of viable domestic alternatives...

From budget to high-end, there is no system that does not benefit from the consideration of room acoustics. Unfortunately, whilst there exists an excess of technical acoustical theory, there is little that translates into, and defines domestic acoustics - and the application of low-impact OEM and domestic-equivalent treatments.

Enter, stage right, my attempt to redress that balance: Practical Domestic Room Acoustics - an approachable article that translates common theory into practical advice, specific to 2-channel system set-up, and domestic room treatment with both OEM and low-impact doemstic equivalent treatment.

The following link will open a Word doc in your browser:

http://www.killahertz-acoustics.co.uk/practicalacoustics.doc

And this one a downloadable (right-click, save-as) equivalent in zip form:

http://www.killahertz-acoustics.co.uk/practicalacoustics.zip

Any observations/omissions/additions/etc are welcome, either in this or a new thread, PM, or email.

 

[JamPal]

I have made this a sticky, people could add any other work they have done in the same vien. Hopefully we can build a good information resource, and perhaps ultimately a HiFi glossary / encyclopedia (almost) in it's own section.

Cheers,

James,

 

[Uncle Bob]

looks like you've put a lot of serious effort in here :dude:

in common with most people, my domestic v hifi arrangements are a compromise but the article does provide some interestingideas that may prove useful when nextre-decorating in the lounge.

thanks foryour efforts

 

[adam]

Superb articile,well worth a very important sticky.

One object that confuses me is glass,it's always thought of a bad thing to have in a room,due to it's highly reflective nature,but yet,reading the coefficients,it's a good bass trap.

Though I do find the 50-60Hz room mode the worst,this really spoils alot of music,and is hard to cure.

Thanks for the effort and time in writing that work!!!

 

[Killahertz]

James,

Thanks for the sticky

Uncle Bob, Adam - yes, it's taken quite some time. Time in assembling much of the information, but also assessing many of the suggestions/scenarios. Of which there are many. But, I believe that is a bonus, as it allows people to take smaller steps, which i've come to believe is a vitalaspect of domestically acceptable acoustics.Few may be able to follow all suggestions, but most can follow some - and, at the end of theday, it all helps.

PS: Adam - (apologies for hawking another of my articles),but have you looked in Helmholtz resonators for that 50-60Hz problem?:

http://www.audioholics.com/techtips/roomacoustics/Helmholtzresonatorabsorber.php

 

[mosfet]

As good an introduction to the subject as you could hope to read Adam. Well written and covers the important practical stuff without straying into unnecessary complexity. Exactly as you intended.

Perhaps a paragraph or so detailing the mechanism behind porous absorption (convoluted pathways to sound waves incurring energy losses etc) to give better illustration of why acoustic foams and the like are suited to acoustic absorption. And another expanding upon the important relationship between thickness and wavelength for porous absorption - especially the one-quarter and three-quarter wavelengths for any given frequency.

Other than this, damn good!

My next upgrade will be a Madagascar Dragon Tree

 

[Killahertz]

mosfet wrote:

As good an introduction to the subject as you could hope to read Adam. Well written and covers the important practical stuff without straying into unnecessary complexity. Exactly as you intended.

That's good of you to say, thank you

With regard to the operative qualities of foam - I have part of that in an earlier article, that covers(will cover)introductory acoustical theory and design. That one, in the light of this new one, will be updated to be more theory and design - i'll remove what little room-specific information there is. This way, the new one remains accessible to more people.

mosfet wrote:

My next upgrade will be a Madagascar Dragon Tree

I really enjoyed the section on plants. And this is one area that i'll hope to expand on in time, as fresh information becomes available, and more people put them to the test. I've got a couple of people lined up for this, but i'd hope that anyone who uses plants acoustically (or at least tries them), would let me know how they went on - with either positive, negative, or neutral outcome.

 

[mosfet]

The challenge with domestic acoustic treatments is, as you note, finding aesthetically acceptable solutions. So the focus on what can be done without necessarily using foams and fibreglass and so on is good. I think this is what most hi-fi people are looking for.

The other point that is rarely mentioned is the possible health implications of using fibreglass and mineral wools in a domestic setting (both give off microfibres having low bio-solubility meaning possible lung irritation). All the official reports I’ve read have concluded the risk is very low – even so it’s not a risk I’d be prepared to take with my family.

There are alternatives I’ve found – natural insulations such as sheeps wool, flax and coconut fibre board.

I’d also recommend the Studio Tips forum as a particularly good resource for all things acoustic.

 

[earl of sodbury]

mosfet wrote:

... The other point that is rarely mentioned is the possible health implications of using fibreglass and mineral wools in a domestic setting (both give off microfibres having low bio-solubility meaning possible lung irritation). All the official reports I’ve read have concluded the risk is very low – even so it’s not a risk I’d be prepared to take with my family.

Bloody well said that man - I've been banging-on about this for nearly 20 years, but even today there is very little attention paid to this aspect of industrial disease. The fact is any frangible mineral material can cause lung disease, acicular/spicular materials seem to be especially likely to do so...

 

[Killahertz]

mosfet wrote:

The other point that is rarely mentioned is the possible health implications of using fibreglass and mineral wools in a domestic setting (both give off microfibres having low bio-solubility meaning possible lung irritation). All the official reports I’ve read have concluded the risk is very low – even so it’s not a risk I’d be prepared to take with my family.

That's a fair point, and especially in terms of the fibreglass. I personally use, and always advocate the use of, mineral wool over fibreglass, and whilst it is not immune from fibre-loss, it is far less invasive than fibreglass. In fact, i've had several different prototype DIY absorbent panels over theyears- using mineral wool - that haven't been covered, used in my listening room without noticeable effect. That said, my final versions - that I still use - have been covered, as they should really be.

 

[matty]

all our fiber products are treated for fiber migration, though the risk is minimal, its something we do as a matter of course. Fiber and Rockwool panels are used in schools and other public places far more than people realise. Next time your in the bank, those nice fabric covered screens are almost certainly fiberboard, or perhaps in the cinema, the ceiling and wall panels are mostly fiberglass....

There is an australian paper on the subject floating around(parden the pun) that is very good.

Its an excellent articleKillahertz and im glad that i could help. I will get some samples of the transparent absorbers off to you sometime if you like!

 

[Killahertz]

matty wrote:

Its an excellent articleKillahertz and im glad that i could help. I will get some samples of the transparent absorbers off to you sometime if you like!

Thanks Matt. And for the samples, too, that'll be great.

I did notice them, but only towards the end of the article. But, then, i've just noticed the new Modex Plate and Broadband - ideal for domestic use. Looks like an update to the article will be needed sooner rather than later!.

PS: The Modex Plate - are they paintable?.

 

[matty]

Modex plate is indeed paintable

mail me your address and i will sort out some stuff for you

 

[adam]

I managed to "tame" that 58-64Hz hump,by usinging matty's RPG foams and rockwall/fibreglass panels,it's still there,but far more liveable with,there are some CDs that are so poorly recorded in that region,it really can trigger the room off,I was not blessed or born to be a DIY'er

 

[9designs]

Wooow just found this forum, from the excellent article from Killahertz, been searching the net for a few weeks looking for this type of info!!!!

As I'mtrying to "fix" my room...... Spoke to RPG last week.... hopefully someone will come back to me re my inquiry ! :Not Sure:

The Calc spread sheet is great, one question, on the Bass trap cals tab, after picking the material, what is the blue number next to it ??? Is that themass of the board ?

Do you then cut a piece that equals that mass ?WxH being variable....

I think the whole subject is so over looked, when a few hundred pounds on treatment could equal many thousands of equipment upgrades...

The key to me seems blending in to the domestic environment, which is why I'm keen to look at DIY options as well as OEM... If I have any chance of selling this to the wife !!!!

Great info ...many thanks.....

 

[JamPal]

Welcome to the Tent 9 Designs. Glad it's useful .

James.

 

[Killahertz]

9designs wrote:

Wooow just found this forum, from the excellent article from Killahertz, been searching the net for a few weeks looking for this type of info!!!!As I'mtrying to "fix" my room...... Spoke to RPG last week.... hopefully someone will come back to me re my inquiry ! :Not Sure:

The Calc spread sheet is great, one question, on the Bass trap cals tab, after picking the material, what is the blue number next to it ??? Is that themass of the board ?

Do you then cut a piece that equals that mass ?WxH being variable....

I think the whole subject is so over looked, when a few hundred pounds on treatment could equal many thousands of equipment upgrades...

The key to me seems blending in to the domestic environment, which is why I'm keen to look at DIY options as well as OEM... If I have any chance of selling this to the wife !!!!

Great info ...many thanks.....

Thank you for the kind words.

I see you've been using the Mode Calc spreadsheet. It's a good few years old now, that one, yet still a useful set of tools. I suppose I should revise it, but the benefit (and my intent when I first made it) was it's simplicity. That said, you have highlighted a valid point in the lack of labelling, and the panel sizing elements of the resonant panel calculator. I suppose because it was designed to go along with my acoustical theory article, which has a section on the calculation and design of such traps.

Anyway, the blue number to the left of the selected panel material is the panel density (kg/m^2). The greater the panel density, the lower the resonant frequency of the subsequent panel (all else being equal). Realistically, once the panel type and gap are selected the user can size the panel as required - the resonant frequency remains the same. What doesn't remain the same is the potential level of absorption. That is determined by the panel size.

You could, then, have a 1ft^2 panel, but that will have only very little absorbent action, especially with a low resonant frequency, high density panel. Hence, practicality determines a range of panel sizes, dependent upon panel density. For densities up to 5kg/m^2 i'd recommend a minimum panel size of 3ft x 1.5ft, for densities up to 10kg/m^2 i'd recommend a minimum panel size of 4ft x 2ft, and for densities above 10kg/m^2 i'd recommend a minimum panel size of 6ft x 3ft.

The lower and mid-range densities are those more likely to find use, and their panel sizes are relatively modest. Do bear in mind, however, that serious modal (low bass) problems may require the use of multiple panels to create sufficient absorption.

Editted to add: I have updated the modecalc spreadsheet to include labelling, recommended panel sizes, and a couple of other additions.

 

[technobear]

Killahertz wrote:

The following link will open a Word doc in your browser:

http://www.apsalisbury.dsl.pipex.com/practicalacoustics.doc

And this one a downloadable (right-click, save-as) equivalent in zip form:

http://www.apsalisbury.dsl.pipex.com/practicalacoustics.zip

These links are broken :Unhappy:

 

[Killahertz]

technobear wrote:

Killahertz wrote:

The following link will open a Word doc in your browser:

http://www.apsalisbury.dsl.pipex.com/practicalacoustics.doc

And this one a downloadable (right-click, save-as) equivalent in zip form:

http://www.apsalisbury.dsl.pipex.com/practicalacoustics.zip

These links are broken :Unhappy:

Yes, they are. I've checked with ADSL Guide and several Pipex users have reported a problem, so hopefully it is a temporary glitch that Pipex are working on.

I can email the zip if you want?.