From the pages of BK electronics, which sells them:
http://www.bkelec.com/Pro/Drive_Units/pd/pd158.htm
The linear displacement is plus or minus 4 mm. That is because the voice coil winding depth is 19 mm, the voice coil gap height is 11 mm, and (voice coil winding depth - voice coil gap height) / 2 = linear excursion.
Therefore, the stated maximum displacement of 13 mm is the mechanically limited displacment, (always greater than the linear displacement), before damage may occur. The specs do not state if that is plus or minus 13 mm, or just 13 mm from front-to-back. My guess is that a typical 15 inch PA driver would be plus or minus 13 mm-that is about normal.
It apparently is a single coil driver, yet it gives specs of L1 = 1.26 mH and L2 = 2.81 mH. I do not know what this means. Full specs are available as a pdf which is linked on that page. I don't have Acrobat on this computer yet, (just did a full reformat on the hard drive), so I can't access that pdf file yet. You can, if you wish.
http://www.bkelec.com/Pro/Drive_Units/pd/pd158.htm
The linear displacement is plus or minus 4 mm. That is because the voice coil winding depth is 19 mm, the voice coil gap height is 11 mm, and (voice coil winding depth - voice coil gap height) / 2 = linear excursion.
Therefore, the stated maximum displacement of 13 mm is the mechanically limited displacment, (always greater than the linear displacement), before damage may occur. The specs do not state if that is plus or minus 13 mm, or just 13 mm from front-to-back. My guess is that a typical 15 inch PA driver would be plus or minus 13 mm-that is about normal.
It apparently is a single coil driver, yet it gives specs of L1 = 1.26 mH and L2 = 2.81 mH. I do not know what this means. Full specs are available as a pdf which is linked on that page. I don't have Acrobat on this computer yet, (just did a full reformat on the hard drive), so I can't access that pdf file yet. You can, if you wish.
Ussually Le is measured at 1 KHz, but some companies also measure at 10 KHz or other frequencies, IIRC you need L1.
The majority of PA manufacturers uses the latter, for some speakers it holds ground, for some it doesn't. Best is to always calculate Xmax yourself (and sensitivity for that matter) for correct comparison between different speakers.
Johan.
At the moment it's common to calculate Xmax as stated above but adding 1/4 of the gap depth, which would give 6.75 mm.
The majority of PA manufacturers uses the latter, for some speakers it holds ground, for some it doesn't. Best is to always calculate Xmax yourself (and sensitivity for that matter) for correct comparison between different speakers.
Johan.
in case it helps:
I chose PD1550 over 158 because it allowed a lower response (I wanted to get close to 20Hz with no droop in the middle of the response), has a little bigger xmax and claimed low distortion.
Also, and this can be important where PD is concerned, it was readlily available a few months ago.
I checked bluearan.com (probably best UK price), but they are out of stock of both 158 and 1550.
Ken
I chose PD1550 over 158 because it allowed a lower response (I wanted to get close to 20Hz with no droop in the middle of the response), has a little bigger xmax and claimed low distortion.
Also, and this can be important where PD is concerned, it was readlily available a few months ago.
I checked bluearan.com (probably best UK price), but they are out of stock of both 158 and 1550.
Ken
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