[Jay Kadis]

In article ,
(GregS) wrote:

In article ,
(GregS) wrote:
In article
,
bobopi wrote:
On 3 juil, 15:37, (GregS) wrote:
In article
, bobopi
wrote:

Hi everyone,
I'm currently working in a lab dealing with auditory perception and
biology. Since I have a very small sound chamber, I need a flat and
compact loudspeaker with a frequency ranger extending from, say, 125
Hz or 150 Hz to 40 kHz. The depth of the speaker should not be above 6
or 7" (15 to 17.5cm). In a nutshell, something like the Fostex PMO.4
but flatter and slightly shifted to higher frequencies:
http://www.fostexinternational.com/d...pm_series_mkII...
l
Do you have an idea ?
thank you in advance
Boris

How flat and it must be on axis, right ? How far away ?
I crosposted.

greg

actually, the sound chamber is about less than a cubic meter. The
speaker should be put very close (a few centimeters) to the ear of an
animal (a guinea pig), which should prevent the chamber to
dramatically influence the frequency response, well, at least, I
hope...
The speaker probably has to be passive because powered speakers would
introduce 60 Hz signals within the chamber (we perform
electrophysiological recordings).
A one way speaker would be best, but a two way speaker is likely
possible if we put the tweeter in front of the animal's ear, since low
frequencies have less directional properties I think.
I found this model that may be of interest, what do you think about
it ?:
http://www.tannoy-speakers.com/produ...a_File_Web%20V
1.
0
6.pdf
Regards,
Boris

Pretty, almost exactly what you want.
When recording there will be a small amount of magnetic noise from the
speaker.
A magnetically shielded speaker is desirable or mandatory. There are way to
shield or partially shield speakers, but its much easier if they are
designed
that way.
Keep in mind the response is likly to be still ragged. I am going to see if
they have a plot on this.
Recording setups are mostly electrostatic sensitive, but magnetics do have
effects.

I might add, I have never worked with a speaker in a test chamber. There are
static magnetic fields
from the speaker and if there is movement or vibration it will induce into
the electrodes. The magnets are the prime magenetic source. The actual signal
field will be much
smaller. Crossover network coils also radiate.

greg



Is the animal restrained? What kind of electrophysiological measurements
are you making?


Electrode/skin impedances are fairly low, although the preamp gain is
substantial for EEG signals with surface electrodes. If you're doing
intracellular recordings, the very high impedances will present a
definite problem with electrical radiation and magnetically-induced
currents. Implanted depth electrodes would fall nearer to the surface
electrode case.

-Jay

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x------- Jay Kadis ------- x ---- Jay's Attic Studio ----x
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