Crossover impedance spike effects - 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 22nd February 2010, 05:04 PM   #1
webba is offline webba  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Default Crossover impedance spike effects

Hi all!

I am building my first DIY speakers. I've had some assistance with the crossover (actually I did design my own but eventually asked for some help and had a better one 'donated'!).

My question relates to the impedance spike (which I've seen on many crossovers in the same area around 20-50hz) - This is around the resonance frequency of the driver, yes? Could anyone explain what causes it to be so high? Average impedance is around 4 ohm but spike reaches 24ohm.

Also, what are effects this has on the amps ability to deliver current in this range? And the effects on sound output here?

My 'beginners' knowledge tells me it shouldn't give acceptable results in this range. But if thats the case - why do so many designs have this?

I have a valve amp - any particular considerations special to valves?

Thanks in advance!

Andy.
  Reply With Quote
Old 22nd February 2010, 05:37 PM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
The rise in impedance at low frequancy is the findemental resonance of the system. This is where your speaker is rolling off. Except for some careful designed aperiodic systems where one works hard to suppress this resonance, it is a feature of all systems.

Tube amplifiers often have a higher output impedance (not a bad thing, just has to be considered in the light of the amp/cable/speaker system). If you have impedance deviations elsewhere, ie 2 ways commonly have a big spike in impedance at the XO, then the interaction of the impedance of the speaker and the output impedance of the amp will cause variations in the FR that follow the impedance

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 22nd February 2010, 06:34 PM   #3
webba is offline webba  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Just for my information: The fundamental resonance of the system. Is this the sum of the interaction of the drivers / air / enclosure / port? Ie changing any of these would change the resonance? If its one of those things we just have to live with I can understand that, but I'm trying to understand the physical processes that produce it / act on it.

Is it more to do with the magnetic field in the coil at low frequency ie the inductive effect?

My amp has 4 and 8 ohm taps. How does this relate to the output impedance you mention?

Presumably ohms law is applicable here, so if the voltage is constant, but the impedance (resistance) increases, then less current must flow. Is that right?

If less current flows that means the driver doesn't get what it needs to reach the pistonic movement it should have for the signal its being asked to reproduce? (aka roll-off)

Please correct or congratulate me on today's little puzzle. I have many more still to come. (Related to inductor / capacitor choices in crossover and their effects on electrical phase - and while we're at it the effect this may (or may not?) have on acoustic phase? - Anyway leave that for another post...)

Thanks in anticipation...
  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
crossover point - effects of impedance? champ222 Multi-Way 6 17th November 2009 07:41 AM
Effects of modifying an existing passive crossover geolemon Car Audio 13 15th January 2006 08:06 AM
Speaker Spike bjackson Multi-Way 8 9th May 2005 01:12 AM
Delay effects of crossover?? Ken L Multi-Way 10 28th November 2003 01:01 PM
Crossover Impedance... Ignite Multi-Way 0 21st August 2001 09:23 PM


New To Site? Need Help?

All times are GMT. The time now is 09:07 AM.


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