What is E5 in The Loudspeaker design cookbook?

[kimbo]

I've got the forth edition of Vance Dickason's book open in front of me and on p.129 in section 8.41B "Measureing Driver Mass - Delta compliance test method", there is a equation that has what looks like E to the power of five. I can not find it defined anywhere. Can anyone point me in the right direction? The equation is.....

Cmb = Vab / (1.42 x E5 x Sd[squared] )

 

[wintermute]

seems nobody knows

I looked in my 6th edition and it is the same, no explanation of what E is, it is definitely to the power of 5 too. I seem to recall I thought the exact same thing when I read that section before, but decided it wasn't something I would use so moved right along.

If my math was better I'd take a guess as to what it is, but its not so.......

Tony.

 

[richie00boy]

If it's a small 'e' then it could possibly mean exponential, i.e. replace e^5 by 10^5 in your case.

Or maybe it's excursion?

 

[kimbo]

Yeah, shame nobody seems to know. I was hoping to use that method to start figuring out the Cmb as a precursor to calculating the Mmd, compliance etc. The power of five has me stumped.....can't see how the dimensions of the answer could come out correctly unless E is a dimensionless number or constant of some sort.

Anybody else care to hazard a guess?

 

[454Casull]

If it's a small 'e' then it could possibly mean exponential, i.e. replace e^5 by 10^5 in your case.

Or maybe it's excursion?

Small e is generally 2.7182818

 

[kimbo]

Looks like you're right 454Casull! (although lower case e usually stands for natural log) Many thanks.

I was able to find confirmation on the KBapps.com website (recomended for some free calculators http://www.kbapps.com/audio/speakerdesign/calculators/Default.htm ) there is a list of the formulae used, and there is one for Vas which looks like......

Vas = 140000000 * Cms * Sd2

...which can be re-written as

Cms = Vas / (140000000 x Sd [squared] )

and as he has his units in liters instead of cubic meters, we can knock off three zeros, implying that ...

E5 = 100000 or 10 to the power of five!

So it looks like he lapsed into engineer speak of 'exponential five'. It would have been much clearer if he had just written 10 to power 5.

oh well, live and learn. Does anyone see a problem with this resolution?

 

[richie00boy]

Looks like you're right 454Casull!

Oi! Don't let him steal all my glory

 

[kimbo]

Whoops....sorry about that richie00boy. A thousand pardons. You were right on the money.

I was so excited about finding confirmation on kbapps that I was not paying the attention I should have. Unfortunately I do this a fair bit and realise what I have done a bout a nano second after I press the send button....and my boss always opens my emails immediately before I can recall them. Just have to slow down.

Thanks everyone! I'll now proceed to give my calculator a workout.

 

[Circlotron]

Can you really trust this book? ;-)

I looked in my 5th edition and on page 3 it starts by saying "This Fourth Edition of the Loudspeaker Design Cookbook....