Author Topic: Defining the diameter of a driver  (Read 371 times)

Offline Arno007

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Defining the diameter of a driver
« on: February 26, 2017, 08:50:17 PM »
To all the experts: please create a short definition of the diameter of a driver.
Reading through many diy articles this seems to be a topic of debate. Terms such as cut-out diameter, screw pcd, foam od, foam id, and some others are quoted. Furthermore, in catalogues one can find 8" (200mm) drivers with a screw pcd of 178mm.  :thinking:

Offline bbe22

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Re: Defining the diameter of a driver
« Reply #1 on: February 26, 2017, 09:08:44 PM »
...for measurement purposes it is common to take the dia from the  middle of the surround across to same on the other side. The basket (total) diameter
may be somewhat larger. Doesn't really matter, most times, as long as you know what you are getting, or what you are really after.
Odd shapes have separate issues

Offline Shonver

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Re: Defining the diameter of a driver
« Reply #2 on: February 27, 2017, 12:56:47 AM »
Driver size groupings are only rough guides. When it comes to acoustics, the size parameters that matter are radiating surface area (Sd) and cone excursion (Xmax). Related to Sd, a driver's effective diameter can be roughly determined as described in the previous post.

Reading through many diy articles this seems to be a topic of debate. Terms such as cut-out diameter, screw pcd, foam od, foam id, and some others are quoted. Furthermore, in catalogues one can find 8" (200mm) drivers with a screw pcd of 178mm.  :thinking:

There is nothing to debate. Simply read the data sheet for the respective model. It should tell you everything you need to know. Typically, good drivers have well-written data sheets; the ones not worth bothering with don't.

Some examples:
http://www.tb-speaker.com/uploads/files/33c889df7418fe23abd60ef0245a932c.pdf
http://www.seas.no/images/stories/excel/pdfdataheet/e0015_w15cy001_datasheet.pdf
http://www.scan-speak.dk/datasheet/pdf/22w-8851t00.pdf
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