What is the effect of using diffusers? ... and other room acoustics Q's

[paulspencer]

What is the benefit of using diffusers as room treatment? In which parts of the room are they best placed? Should they be used for ceilings, and in particular cathedral ceilings? What is their subjective impact, in particular on imaging?

Are they effective for a broad bandwidth? It seems to me that it's hard to cater to a broad bandwidth as for most of the audible range the wavelength will be much larger than the dimensions of the diffusers.

Anyone know any good articles on this topic?

I would like to try placing offcuts of timber on the rear wall and possibly ceiling, similar in a way to some stone walls, with bits of timber cut at different angles of different sizes.

 

[sreten]

Consider that your room is lined with mirrors.

From your seating position the image of the speaker you
see where the diffusor is shows the off axis output of the
speaker it would be interacting with for first reflections.

Front, rear wall and ceiling mounting will have minimal effect.

Side wall mounting on the reflected position of your speaker
will have the most first reflection effect. A series of wooden
cd holding cases set twisted 45 degrees towards you to form
a /\/\/\/\/\ effect is an idea I came up with. One either side.

A standard studio techique it to place all the equipment and stuff
on a large open shelfing unit against the back wall to break up
rear reflections.

Good information is hard to come by.

🙂 sreten.

 

[chris ma]

Reflect and absorb should work together. You do not want the room to be too bright or too dead.

There is a thread here link to a site and you can read the articals about room treatments.

http://www.diyaudio.com/forums/showthread.php?postid=68561#post68561


This is how I located mine..
Good Luck

 

[Bill Fitzpatrick]

Paul:

Do a google search: schroeder diffuser

You should find plenty of info and possibly plans for making them.

 

[Ken L]

Anyone know any good articles on this topic?

This is the best article I have come across.

http://www.asc-hifi.com/articles/iar89.htm


And this is the best diy I have come across on how to clone the ASC traps

http://ic.net/~jtgale/diy2.htm

another DIY method to build the traps -

http://teresaudio.com/haven/traps/traps.html

Ought to be something of use to you within those links.

Nothing about timbers _grin_

Note that proper use of the traps depends on rotating them at the proper angle - which relates to the fact that they are absorbent on one side (one full half of the trap)

The best sound I have ever heard was in a room with some of the ASC traps.

Regards

Ken L

 

[phase_accurate]

Here you will find a picture of a Schröder diffusor:

http://www.strauss-elektroakustik.com/english/se_akustik/fs_se_acustic.html

Regards

Charles

 

[Karoliina]

What is the benefit of using diffusers as room treatment? In which parts of the room are they best placed? Should they be used for ceilings, and in particular cathedral ceilings? What is their subjective impact, in particular on imaging?

It depends on the use intended for the room. In general
it have been recommended that the ceiling should
be totally dampened and non-reflective surface where
the rear wall can contain some diffuse material.

With my experience however, I prefer fully dampened
room. We have acoustic panels in all walls and ceiling
in our home theater and it works very well with 5.1 material.
It doesn't work with stereo sound source however, the
sound is too dry. But with multichannel in mind, more damping
material is ok and less diffusors are needed.

Our home theater is comparable in reflectivity to local small THX
theater that has quite zero level of audible reflections
(not 100% anechoic if measured, but subjectively anechoic).

Best Wishes,
Karoliina
---
http://www.karoliinasalminen.com/forums/viewforum.php?f=4
http://www.karoliinasalminen.com/forums/viewforum.php?f=10

 

[Karoliina]

Sorry, I didn't remember to answer completely, so here is an addition:

Diffusers increase the controlled reflectivity of the room and thus brighten its tonal balance where dampening makes it darker.

 

[phase_accurate]

While dampening makes a room less reverberant it also "eats" acoustic power which in turn leads to the need for larger speakers and increased amplifier power which isn't only advantageous (larger speakers with worse spatial reproduction, larger THD and IMD, ......).

I recommend reading the parts about spatial reproduction within the following:

http://www.celticaudio.co.uk/technical2.htm

Diffusors can improve audio reproduction by a great deal. Not by killing reverberation but by changeing the reverberation characteristics.


Regards

Charles

 

[Ken L]

I recommend reading ........

http://www.celticaudio.co.uk/technical2.htm

that's a great link charles!

I'm reading through the whole page, it's pretty good stuff.

Thanks for posting it.

Regards

Ken L

 

[paulspencer]

For some reason I didn't get any email notification of responses so I didn't realise I had replies. Thanks to everyone who replied. I'm looking at all the links and there is some very interesting information ... more from me later ...