Transfer Function/Room Boost Calculator?

[Two Moons]

Hello,

Anyone know of a software program or equation that I can use to calculate the transfer function/room boost of low frequncies, with the input being my rooms volume?

Thanks,

Dave

[AudioFreak]

if that alone was all you had to worry about it wouldnt be such a problem ..... depending upon the shape, size and density of whatever is in your listening room, the position of the sub/s and many other variables, the figures can vary dramatically.

[Two Moons]

For now, I'm just looking figure out the boost on frequency independent of room reflections, modes, etc. I realize that this is a simplified account of response, but I want to, at least, take care of this variable. That way I have made the problem of positioning in the room less of a tradeoff between output and smooth response, even though I will not have entirely eliminated the problem.

Am I making any sense?

Dave

[Ignite]

The problem is that depending on placement and room shape alone there could be close to no gain, going all the way up to 10-12dB at 20Hz in a very small (car) room.

Room shape is far more important than it's volume. I'm sure someone with more knowledge of room interactions could suggest a room shape with a small volume that offered very little gain, and a room with much larger volume that offered a huge amount of gain.

You could always measure your room's transfer function. Details on how to do this in a car (it should be rather similar in a room) are available at http://www.diysubwoofers.org/projects/cartf/

In my qualitative experience, room gain isn't nearly as high as most suggest it is unless you consider corner placements.

[jteef]

You can measure your transfer function pretty easily using a cheap radio shack SPL meter and an existing sealed driver that is large enough to produce SPLs above ambient in a relatively anechoic enviornment (the middle of your back yard for example?) in the lower frequencies of interest.

jt

[Ignite]

Originally posted by jteef
You can measure your transfer function pretty easily using a cheap radio shack SPL meter and an existing sealed driver that is large enough to produce SPLs above ambient in a relatively anechoic enviornment (the middle of your back yard for example?) in the lower frequencies of interest.

jt

That is such a great idea I just tested out my new sealed Tempest subwoofer driven with 500W in my back yard. My neighbours complained so I came inside. It is definitely "above ambient" at 20Hz.
And it conforms almost exactly to the WinISD simulation. Slightly deeper response, actually. Must be the extra stuffing.