On Fri, Jan 28, 2011 at 03:37:21PM +0100, Renato wrote:
> firstname.lastname@example.org wrote:
They have to be of reasonable quality and FR, but any remaining
small errors can easily be calibrated out. You just take the
direct sound (for a good speaker + mic this will be the first few
ms of the IR) as a reference.
A few percent distortion (most speakers will have this) does not
matter if the measurement is done in the correct way: after the
deconvolution the distortion products will appear *before* the
real IR and they can be removed easily.
> Also, do mic vendors offer files with the frequency response of the mic
The high quality ones will have tight specs and usually come with
a measured FR or other calibration data.
There are a few other points to consider.
Most speakers will be directional at all but the lowest frequencies.
It depends on your application if this matters or not. If it does
(e.g. to measure room acoustics according to international standards)
you need an omnidirectional speaker. These are usually made as a
dodecahedron of small speakers. See
for an example.
Also omni mics will have some directionality at high frequencies, and
that is why they come in two forms: calibrated for flat FR on-axis
(plane wave), or for flat FR in a diffuse field (averaged over all
directions). The difference matters only at very high frequencies.
Some measurement come with a small conical diffuser which can be
attached in front to improve diffuse-field response.
There are three of them, and Alleline.
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