Vas and diameter of the speaker

dimitri · 22nd November 2002, 11:57 AM

Hello,
there is a nice on-line calculator

http://www.webervst.com/spkrcalc/para.htm

there one can read:

To determine the diameter of the speaker, take the size of the speaker (e.g. 12") times .85

Please can you help me, what is diameter of the speaker?
Is it diameter of the cone itself?
Is it diameter of the cone with rubber surround?
Why .85?

The diameter of the speaker has direct influence on Vas.

Thank you,
Dimitri

SY · 22nd November 2002, 01:06 PM

The .85 is a crude attempt to convert the driver nominal diameter to something approximating the radiating diameter.

dimitri · 25th November 2002, 01:44 PM

OK, but which diameter should I measure with trammel?

SY · 25th November 2002, 02:26 PM

Remember, precision here is useless- Vas varies all over the place with changes in temperature, barometric pressure, and use of the driver. If you use the known-box-volume method of Vas determination, you don't even need Sd.

In any case, you can approximate Sd pretty well by dropping the 0.85 factor and using the diameter of the cone plus half the surround.

dimitri · 27th November 2002, 11:36 AM

Thank you, I have heard about assosiating air mass. I use the known-mass instead of the known-box-volume method because I can adjust the mass to be the same order as vibrating system mass. For the same accuracy I will need several boxes with different volumes. I use white noise instead of sweep, it is much faster.

22nd November 2002, 11:57 AM	#1
dimitri diyAudio Member Join Date: Oct 2002 Location: retired	Vas and diameter of the speaker Hello, there is a nice on-line calculator http://www.webervst.com/spkrcalc/para.htm there one can read: To determine the diameter of the speaker, take the size of the speaker (e.g. 12") times .85 Please can you help me, what is diameter of the speaker? Is it diameter of the cone itself? Is it diameter of the cone with rubber surround? Why .85? The diameter of the speaker has direct influence on Vas. Thank you, Dimitri

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22nd November 2002, 01:06 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	The .85 is a crude attempt to convert the driver nominal diameter to something approximating the radiating diameter.

25th November 2002, 01:44 PM	#3
dimitri diyAudio Member Join Date: Oct 2002 Location: retired	OK, but which diameter should I measure with trammel?

25th November 2002, 02:26 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Remember, precision here is useless- Vas varies all over the place with changes in temperature, barometric pressure, and use of the driver. If you use the known-box-volume method of Vas determination, you don't even need Sd. In any case, you can approximate Sd pretty well by dropping the 0.85 factor and using the diameter of the cone plus half the surround.

27th November 2002, 11:36 AM	#5
dimitri diyAudio Member Join Date: Oct 2002 Location: retired	Thank you, I have heard about assosiating air mass. I use the known-mass instead of the known-box-volume method because I can adjust the mass to be the same order as vibrating system mass. For the same accuracy I will need several boxes with different volumes. I use white noise instead of sweep, it is much faster.

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