room dimesnions & baffles

[William Hall Jr.]

When applying Golden Mean ratios to a space which will be the height of almost two stories, and with a trapezoidal-shaped gable, how should one proceed?

Isa there any issue with the aural "stage" being glass (except of course for the 3-feet for the "virtual horn"?

How does one decide whether baffles--on walls, in gable, suspended from gable--should be installed?

Thanks!

[Chris A]

Can you draw a picture of your space? You can upload pictures using the "Options" tab, then use "Add/Update".

Chris

[Chris A]

When applying Golden Mean ratios to a space which will be the height of almost two stories, and with a trapezoidal-shaped gable, how should one proceed?

This is not altogether easy to answer without some understanding of the degree of "trapazoidal-ness" of the ceiling (I'm assuming that is the dimension that you are referring to). Having slanted ceiling space is not easy to deal with, but if the ceiling is already 2 stories high, then the early reflections from ceiling panels shouldn't be a great issue.

Is a there any issue with the aural "stage" being glass (except of course for the 3-feet for the "virtual horn"?

Glass can be an issue, depending on the orientation of the glass to your room dimensions, speaker placement, and your listening position(s).

How does one decide whether baffles--on walls, in gable, suspended from gable--should be installed?

First, I'd look at the whole setup to understand what issues may be there, then do trades on the pros/cons of alternatives.

Chris

[artto]

When applying Golden Mean ratios to a space which will be the height of almost two stories, and with a trapezoidal-shaped gable, how should one proceed?
Isa there any issue with the aural "stage" being glass (except of course for the 3-feet for the "virtual horn"?
How does one decide whether baffles--on walls, in gable, suspended from gable--should be installed?

Thanks!

Using the "golden mean" or "golden ratio" or fibonacci whatever you want to call it, applies only to rooms of rectangular proportions (as most residiential rooms are constructed).

Once you start angling or curving the room surfaces the calculations for determining room modal responses becomes exceedingly more complicated. Furthermore, this affects primarily the bass frequencies. In fact, as a room's size increases, these modal interactions become less and less meaningful, until the wave length of the lowest frequency that is to be produced, is sevearl times less than the shortest room dimension, where it has no usefulness at all.

The idea is to introduce as many, closely, but evenly spaced "modes" as possible. The "modes" are simply where the dimensions of the room coincide with, or are multiples of (or "even" fractions of) the wave lengths of sound being produced in the room.

The lower frequencies tend to "pile up" at the room boundaries, especially at boundary intersections, such as wall/ceiling, or corners.

Acoustical "models" have been historically poor at "predicting" how a room will perform. In my experience, the best thing one can do is avoid the things that produce the most problems in the first place. Small cube proportioned rooms contain the fewest number of modes along with largest number of "strong modes" because of the multiple coinciding room dimensions where they are the same dimensions as the frequency wave lengths. A room that is 15'x15'x15' for instance will have a substantial bass "hump" 75Hz because the wave length of 75Hz is 15 feet. The down side to this is that there will also be a null spot somewhere in the room where this 75Hz tone is almost completely cancelled. And this is really why getting the room proportions "right" becomes important ~ so that you're not cancelling musical tones that you should be hearing.

As far as treating the room goes, what you're basically shooting for is "broadband" diffusion and absorption, meaning that you need to affect a wide range of frequencies uniformily. A 100Hz tone has a wave length of more than 11 feet. Therefore, something corregated with shapes the size of an egg carton will have very little affect at 100Hz and lower.

Use your ears. Clap your hands. Use the SsssZZzzzzzz sound with your mouth. Walk around the room. Listen for buzzy reflections and dead spots. You can also have one person sit in the listening position while another holds a mirror against the room surfaces, gradually moving it around.. Where ever the person in the listening position can see the speaker reflection in the mirror is where there is going to be a direct reflection from the speaker off of the room surface, reflected directly toward the listener. These are your first location choices for treatments, along with corner interesections where the bass piles up.

http://www.ethanwiner.com/acoustics.html#big%20waves

http://www.acoustics101.com/

http://www.auralexuniversity.com/

http://www.google.com/search?hl=en&ie=UTF8&oe=UTF8&q=room+modes

If you find any articles by Arthur Noxon read them. A lot them seem to have been removed from the web