Active vrs passive - Page 87 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th December 2012, 07:04 PM   #861
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by dewardh View Post
This is a possible (theoretical) advantage of series over parallel passive crossover topologies, but with active the amplifier does the same thing even better . . . it "washes out" the effect of the dynamic changes in driver behavior. I'm not convinced that it makes a whole lot of difference, but the immunity from driver effects, dynamic and otherwise, that the intervening amplifier provides is one of the arguments for an active design.
Actually, actives do not wash out dynamic effects. Just another myth. I know a lot of people say that but it is simply not true. What actives do is keep the voltage transfer function constant. That sounds like a big deal but it is current, not voltage, the generates the force applied to the cone. So as the voice coil undergoes dynamic changes in impedance the current and resulting force applied to the cone still vary even though the voltage transfer function remails fixed. If you want to wash out dynamic changes in driver behavior you have to go to current drive.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 10th December 2012, 07:04 PM   #862
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Please do not quote the entire post just above yours. Over-quoting cleaned up.
  Reply With Quote
Old 10th December 2012, 07:08 PM   #863
ORNJ is offline ORNJ  United States
diyAudio Member
 
Join Date: Mar 2011
Location: CA
Quote:
Originally Posted by dewardh View Post
It's just double (3dB) . . . which is pretty much enough to account for crest factor and (passive) crossover losses (in a reasonably designed system). Some people will argue that the passive systems needs even more power, but I think that perhaps they exaggerate . . .
Oh yea, but I was thinking more in terms of draw from the wall though....I like saving a buck anywhere possible.
  Reply With Quote
Old 10th December 2012, 07:08 PM   #864
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by Barleywater View Post
A parallel or series circuit of linear components has linear transfer function at every node.
Parallel and series crossovers, however, have different nodes, and different resulting properties.
  Reply With Quote
Old 10th December 2012, 07:09 PM   #865
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by ORNJ View Post
I am sure that this has been mentioned before on here but I feel that Linkwitz's explanation of why active is better makes perfect sense..

The amplifier has more control over the driver and you can implement different types of crossovers for the best possible sound.
Again, the argument is flawed. What controls the driver is the current through the voice coil. It makes absolutely no different how that current gets there, directly from the amplifier's terminals or through a passive crossover. The only difference between active and passive is that with an active crossover the voltage transfer function is not affected by any variations in driver impedance.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.

Last edited by john k...; 10th December 2012 at 07:12 PM.
  Reply With Quote
Old 10th December 2012, 07:13 PM   #866
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by Barleywater View Post
A parallel or series circuit of linear components has linear transfer function at every node.
But when the values of the driver change, so does the transfer function. In a series XO things move such that things hang together, because everything affects everything. In a parallel circuit, HP & LP are independent.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 10th December 2012, 07:19 PM   #867
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by dewardh View Post
Parallel and series crossovers, however, have different nodes, and different resulting properties.
The linear components can only apply linear change.

As JohnK points out, current drive, which is really just current feedback, in active system that can and does dynamically respond to changing reactance
of driver.

Regards,

Andrew
  Reply With Quote
Old 10th December 2012, 07:23 PM   #868
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by john k... View Post
The only difference between active and passive is that with an active crossover the voltage transferfunction is not affected by any variations in driver impedance.
That's not a trivial difference, and it's maybe not the only one. Depending on how you choose to look at it (perspective) the increased source impedance (caused by series resistance in the passive crossover) does change driver behavior (the higher the source impedance the more it behaves like current drive). There are even books on the subject . that claim current drive reduces distortion. I haven't been able to measure it, but the theory's there . . .
  Reply With Quote
Old 10th December 2012, 07:38 PM   #869
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Hi Deward. I didn't say it was a trivial difference, but that the voltage TF doesn't change does not mean dynamic changes in the driver's impedance are washed out. That is the point that is missed.

I do agree that this is mostly a theoretical argument. both passive annd active speakers, parallel or series, can sound very good, or bad. It's more about good design than one or the other.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 11th December 2012, 04:47 PM   #870
dewardh is offline dewardh  United States
diyAudio Member
 
Join Date: Dec 2005
Location: Berkeley, CA
Quote:
Originally Posted by john k... View Post
I do agree that this is mostly a theoretical argument. both passive annd active speakers, parallel or series, can sound very good, or bad. It's more about good design than one or the other.
I'm sure that's probably true . . .

I've just gotten so in the habit of thinking of "drivers" as having a constant Zin (of about 10k resistive) and equal sensitivity that I sometimes forget the "old ways" . . . (actually I still sometimes use "passive" shaping circuits thrown in there somewhere to adjust the response, sort of like SL did between the mids).
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Active or Passive bjackson Multi-Way 30 4th April 2005 10:49 PM
Passive into active MethMan Multi-Way 8 12th January 2005 04:58 PM
Active of passive audiobomber Multi-Way 9 31st July 2004 02:31 AM
dB loss by using passive crossovers? Active vs Passive and 1st vs 4th order Hybrid fourdoor Multi-Way 3 11th July 2004 09:16 PM


New To Site? Need Help?

All times are GMT. The time now is 10:29 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2