crossover component formulae |
Post Reply | Page 12> |
Author | ||
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
Posted: 08 March 2017 at 7:33pm |
|
Hi
the formulas for the component values in a second order butterworth filter are: L=Z/(root2.Pi.f) and C=1/(2.root2.Pi.Z.f) are there similar formulae for Linkwitz Riley and Bessel alignments? cheers Phil
|
||
Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2537 |
Post Options
Thanks(0)
|
|
Yes.. there are. |
||
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
|
|
you tease
|
||
_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
Post Options
Thanks(0)
|
|
The formula only apply to resistive loads, and drivers that are ruler flat for a large distance beyond the crossover point.
In other words they are of little use in designing a real crossover. |
||
djk
|
||
madboffin
Old Croc Joined: 03 July 2009 Location: Milton Keynes Status: Offline Points: 1538 |
Post Options
Thanks(0)
|
|
I'm sure I have seen some online calculators that will give the theoretical filter component values. But the only use for a calculated crossover is as a starting point to get you in the ballpark before doing a proper design exercise - for the reason DJK gives in the previous message.
The component values will need a lot of tweaking before they work properly with real drive units. Edited by madboffin - 08 March 2017 at 11:34pm |
||
MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
Post Options
Thanks(0)
|
|
No they wont get you even close to the ball park.
Crossovers are made with acoustical measurements, not by calculators.
|
||
Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
||
madboffin
Old Croc Joined: 03 July 2009 Location: Milton Keynes Status: Offline Points: 1538 |
Post Options
Thanks(0)
|
|
Well they will get you into the back row of seats if not the actual ball park...
When I worked for a major speaker manufacturer (long time ago) we would design crossovers using an iterative process. After examining the frequency response and impedance curves of the drivers (and maybe building zobel networks), the starting point would be a "calculated" set of filters built with component substitution boxes. Then of course, lots of measurements - using either B&K chart recorders or the original TEF analyser (I said it was a long time ago...) The substitution boxes made it easy to change components just by setting switches, so although it involved a lot of adjustments it was not difficult, just very time-consuming. But I used to get through an awful lot of chart paper... Edited by madboffin - 09 March 2017 at 12:13am |
||
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
|
|
guys, I don't want to start a debate about crossover design. I'm actually quite into it and am trying to set up some calculations for filter components loaded with different zobel networks. I need the formulas not online calculators. does anyone know them or should I start trying to work them out from the transfer functions? btw all the crossover i've designed in akabak have come out so near to what I expected that it wasn't worth tweaking them.
|
||
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
|
|
okay the 2nd order LR components are the same value as the first order butterworth components. obvious when you think about it as LR is two cascaded Butterworth filters. Still stumped on the Bessel values.
|
||
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
|
|
won't pretend I understand why but the Bessel values are a factor of root3 different to the LR values - just verified this by tapping numbers into the online calculator. so for normalised 2nd order bessel:
L=root3.Z/2.Pi.f C=1/2.root3.Pi.Z.f |
||
audiomik
Old Croc Joined: 06 April 2010 Location: Bath, UK Status: Offline Points: 2962 |
Post Options
Thanks(0)
|
|
Phil
bench with many components here still if you want to try things empirically! Mik |
||
Warning! May contain Nuts
plus springs, washers, screws, etc, etc. |
||
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
|
|
thanks Mik, will show you what I come up with. Hopefully model once, build once ;)
|
||
Post Reply | Page 12> |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |