Speakerplans.com Homepage
Forum Home Forum Home > General > Advanced Discussion
  New Posts New Posts RSS Feed - Thiele\Small Quiz
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Thiele\Small Quiz

 Post Reply Post Reply Page  12>
Author
Message
Danmounter View Drop Down
Registered User
Registered User


Joined: 04 August 2006
Location: United Kingdom
Status: Offline
Points: 18
Post Options Post Options   Thanks (0) Thanks(0)   Quote Danmounter Quote  Post ReplyReply Direct Link To This Post Topic: Thiele\Small Quiz
    Posted: 16 August 2008 at 1:37am

Can anybody tell me either:

How to convert the parameter Bl (Motor Strength) of a loudspeaker from the rather mysterious Beyma unit of N\A to the usual tesla metre?

 

Also, what exactly does N\A stand for?

Any help will be gratefully received!

 

Dan

Mercedes Sprinter 316, the most exciting way to move PA systems known to mankind...
Back to Top
Centauri View Drop Down
Old Croc
Old Croc


Joined: 29 November 2004
Location: Newcastle Aus
Status: Offline
Points: 1792
Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2008 at 2:33am
As far as I am aware, they are one in the same.  I always took N/A to mean "not applicable" - maybe they feel that T.m are not valid units of measure.
Back to Top
Danmounter View Drop Down
Registered User
Registered User


Joined: 04 August 2006
Location: United Kingdom
Status: Offline
Points: 18
Post Options Post Options   Thanks (0) Thanks(0)   Quote Danmounter Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2008 at 2:38am
Ahhh that's the logical answer, but I did want to get a second opinion. It's either that or it means (According to the S.I. Standard) Newton Amperes, which in turn makes no sense whatsoever! I did sort of hope it was Not Applicable...
Anyone else have two cents on this?
 
 
Mercedes Sprinter 316, the most exciting way to move PA systems known to mankind...
Back to Top
ceharden View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 05 June 2005
Location: Southampton
Status: Offline
Points: 11409
Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2008 at 3:25am
It does indeed stand for Newtons per Ampere.  Which actually makes more sense than Tesla.metres if you think about what it's describing!

The force with which the voice coil will try to move when a current is applied!
Back to Top
Centauri View Drop Down
Old Croc
Old Croc


Joined: 29 November 2004
Location: Newcastle Aus
Status: Offline
Points: 1792
Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2008 at 3:47am
Well that would make more sense.  The BL will vary with voice coil resistance, which will of course determine the current.   If Tesla.metres means "Driver magnetic flux density x voice coil conductor length" (taken from Hornresp help file definitions), then the voice coil resistance would not be taken into account at all, rendering the BL figure pointless.
Back to Top
Matute View Drop Down
Registered User
Registered User


Joined: 28 February 2006
Location: Argentina
Status: Offline
Points: 38
Post Options Post Options   Thanks (0) Thanks(0)   Quote Matute Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2008 at 5:37am
"Hmm... difficult to see... always in motion is the future..."
Back to Top
Danmounter View Drop Down
Registered User
Registered User


Joined: 04 August 2006
Location: United Kingdom
Status: Offline
Points: 18
Post Options Post Options   Thanks (0) Thanks(0)   Quote Danmounter Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2008 at 2:29pm

I thought Newton metres per Ampere would make sense, but not Newtons on their own per se...  The article Matias posted a link to has cleared the confusion up thank you!

I didn't think to check the Hornresp help file...silly me!
 
Thank you to everyone :)
Dan
Mercedes Sprinter 316, the most exciting way to move PA systems known to mankind...
Back to Top
David McBean View Drop Down
Registered User
Registered User


Joined: 11 January 2008
Status: Offline
Points: 45
Post Options Post Options   Thanks (0) Thanks(0)   Quote David McBean Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2008 at 10:52am

Hi Everyone,

 
We know from Faraday’s Law that:

 
f = B * l * i
 
where:

 
f = force in newtons

B = magnetic flux density in tesla

l = conductor length in metres

i = electrical current in amperes

 
Rearranging gives:

 
f / i = B * l

 
The units newton / ampere and telsa * metre are therefore equivalent.

 
It makes little sense however to express magnetic flux density * conductor length in newtons / ampere.  Similarly it is not very logical to express force / current in tesla * metres.  This is why tesla.metre rather than newton/ampere is used as the unit for Bl in Hornresp.

 
Just thought you would like to know :-).
 
Kind regards,

 
David
Back to Top
David McBean View Drop Down
Registered User
Registered User


Joined: 11 January 2008
Status: Offline
Points: 45
Post Options Post Options   Thanks (0) Thanks(0)   Quote David McBean Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2008 at 12:22pm
Originally posted by Centauri Centauri wrote:

The BL will vary with voice coil resistance, which will of course determine the current.
 
Hi Centauri,
 
Just to clarify - Bl and voice coil resistance are entirely separate parameters.  Bl is a function of the magnet strength and voice coil conductor length - it is quite independent of the voice coil resistance.
 
Kind regards,
 
David
Back to Top
Centauri View Drop Down
Old Croc
Old Croc


Joined: 29 November 2004
Location: Newcastle Aus
Status: Offline
Points: 1792
Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2008 at 12:47pm
Hey, David.

Did you join up to post in this thread?

Thanks for the explanations.  I haven't really delved into driver theory much at all, preferring to work with the application of the data.  I hadn't actually realised that Bl IS actually the B and l from Faraday's Law, and as such, of course Telsa.metres would be the appropriate measurement units.  As Bl is an indicator of motor strength, in the context of "motor strength" Newtons per Ampere would make more sense, which is maybe why Beyma use those units.  In this case, maybe the parameter should be specified as "motor strength" rather than "Bl", with either Tesla.metres or Newtons/Amp being equivalent units.

I had assumed there was a correlation between Bl and voice coil resistance due to the change in Bl you get when specifying voice coil resistance in WinISD, however, as neither flux density or conductor length are specified, this would be due to back calculation from other parameters.

Very interesting stuff.

Cheers
Graeme
Back to Top
Contour View Drop Down
Young Croc
Young Croc


Joined: 03 March 2004
Status: Offline
Points: 545
Post Options Post Options   Thanks (0) Thanks(0)   Quote Contour Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2008 at 8:09pm
I always thought mister Lorentz came up with F = B x  i  x L, isn't this force called a 'lorentz' force?
             
Best regards,
 
Walt
Back to Top
David McBean View Drop Down
Registered User
Registered User


Joined: 11 January 2008
Status: Offline
Points: 45
Post Options Post Options   Thanks (0) Thanks(0)   Quote David McBean Quote  Post ReplyReply Direct Link To This Post Posted: 18 August 2008 at 9:09am
Originally posted by Contour Contour wrote:

I always thought mister Lorentz came up with F = B x  i  x L, isn't this force called a 'lorentz' force?
 

Hi Walt,

 
As I understand it, the equation f = B * l * i can be derived from either Faraday’s Law of Electromagnetic Induction (when considered “in reverse”) or from the Lorentz Force Law.  I chose to credit Faraday rather than Lorentz simply because Faraday pre-dated Lorentz.

 
You will note that I was careful not to say that f = B * l * i was Faraday’s Law, but just that “we know from Faraday’s Law that f = B * l * i”.

 
The Lorentz Force Law is normally expressed as:

 
f = q * (E + v x B)

 
where:

 
f  =  force in newtons

q  = particle electrical charge in coulombs

E =  electric field in volts per metre

v =  particle instantaneous velocity in metres per second

x = vector cross-product

B = magnetic field in teslas

 
The discovery of the so-called “Lorentz Force” was actually made before Lorentz’s time, hence my reluctance to give him the credit :-).

 
Kind regards,

 
David


Edited by David McBean - 20 August 2008 at 9:21am
Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.078 seconds.