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|19th September 2002, 12:20 PM||#1|
Join Date: Feb 2002
Ciare Nd-magnet PA woofers for sealed box home subwoofer?
Came across these beautiful woofers (www.ciare.com, www.seeburg.net). They have Neodynium magnets, low mechanical losses and usually very benign frequency response in spite of their paper cones + the prices are ok for what they offer.
The 12.00 NdW 12 inch woofer was tested in Hobby Hifi 04/2002 and had exceptionally low distortion figures.
I would like to use one of these woofers in a sealed box subwoofer and use a LT circuit to extend bass response to about 25 Hz.
Unfortunately, their fs is pretty high and Qts pretty low. Hence, configurations with a Q of 0.5 to 0.6 (for good impulse response) have an f3 of >100 Hz. Given the rather low linear excursion, they cannot handle the 16x increase in excursion at the LF end that a LT circuit brings.
What can I do:
- increase Q_es through series resistance: screws up damping factor
- increase m_ms by gluing/sandwiching something onto the cone, preferably increasing stiffness while not allowing resonances. Should lower fs and increase Q. Experience?
PS: the attachment needs to be renamed to .xls
|22nd September 2002, 01:23 AM||#2|
Wizard of Kelts
Low excursion drivers put into sealed subwoofers do not yield high bass output.
To get 112 dB at 1W/1M-actually that figure is pretty close to what you'll get in the whole listening room-you need to move around 2000 cubic centimeters of air.
Multiply the cone area by excursion, (+/-, not front-to-back), and you will see how much air your speaker can move.
It is true that PA speakers are designed to go outside their linear area to an extent, but there are limits.
I posted these charts on this thread for such a situation as this:
Volume Displacement For SPL Chart
Two charts-one in cubic inches, the other in cubic centimeters. When you locate the appropriate chart, pressing F11 is a good idea.
Hope this helps.
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