Changing a passive crossover to active - Page 3 - 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 7th August 2008, 11:09 AM   #21
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

the esteemed Rod Elliot is no expert on domestic hi-fi loudspeakers.

/sreten.
  Reply With Quote
Old 7th August 2008, 11:38 AM   #22
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Default Re: Re: Re: Changing a passive crossover to active

Quote:
Originally posted by sreten



Active 2-ways are a waste of exspense driving the tweeters
unless you have suitably lower power amplifiers for them.

/sreten.
This is unless you want the system to play loud without lots of distortion and smoked tweeters.

When playing loud, passive crossovers are the #1 cause of tweeter death, particularly 6dB/oct and 12dB/oct ones and the ones that achieve the most ideal acoustic response, because they are also the ones allowing huge amounts of low frequency energy to reach the tweeter. Also, when coils and voice coils get hot their Rdc can increase by 30% or more thus detuning the system.

Only active crossovers allow you to use all-pass filters (and delays) to compensate for driver/enclosure phase shifts and get phase matching and optimum summing without requiring ideal acoustic responses.

Given the same sensitivity, peak power requirements for tweeters are actually equal or higher than for woofers, particularly with recordings involving real instruments and little compression. It's the average HF power what is much less than average LF power, but the crest factor is also much lower for lows, so a smaller amplifier is a huge mistake unless the tweeter has a much greater sensitivity. This is something that you easily learn when setting up the limiters in active filters, because it gives you the chance to analyse actual signal levels after frequency division.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 7th August 2008, 11:49 AM   #23
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default Re: Re: Re: Re: Changing a passive crossover to active

Quote:
Originally posted by Eva
Given the same sensitivity, peak power requirements for tweeters are actually equal or higher than for woofers, particularly with recordings involving real instruments and little compression.
agreed, but no one else wants to believe us.
__________________
regards Andrew T.
  Reply With Quote
Old 7th August 2008, 12:24 PM   #24
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Default Re: Re: Re: Re: Re: Changing a passive crossover to active

Quote:
Originally posted by Eva


Given the same sensitivity, peak power requirements for tweeters are actually equal or higher than for woofers, particularly with recordings involving real instruments and little compression. It's the average HF power what is much less than average LF power, but the crest factor is also much lower for lows, so a smaller amplifier is a huge mistake unless the tweeter has a much greater sensitivity. This is something that you easily learn when setting up the limiters in active filters, because it gives you the chance to analyse actual signal levels after frequency division.

Quote:
Originally posted by AndrewT
agreed, but no one else wants to believe us.
Hi,

This one has been done to death.

The simple fact is for active bi-amping a good c/o point for 2
identical amplifiers is around 350Hz, i.e. a 3-way with active
bass/mid and passive mid/ treble.
Move this up to 3.5kHz and you are simply dead wrong.

The argument implies active amplification is a complete waste
of time, i.e. a 200W amplifier will always be better than 2x100W.
However the active 2x100W can swing the equivalent of 400W ....

/sreten.
  Reply With Quote
Old 7th August 2008, 12:30 PM   #25
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default Re: Re: Re: Re: Re: Re: Changing a passive crossover to active

Quote:
Originally posted by sreten

This one has been done to death...................................
Move this up to 3.5kHz and you are simply dead wrong........
as I said, few if any agree.
__________________
regards Andrew T.
  Reply With Quote
Old 7th August 2008, 12:32 PM   #26
diyAudio Member
 
Robert GS's Avatar
 
Join Date: Sep 2005
Location: Helsingor
why is a 200Watt amplifier always better than 2x100W.

Then a 20000Watt ampilfier will be unbeatable unless someone comes up with a 20001Watt
__________________
GroundSound.com Active Sound - Active Listening
Digital Crossovers, Power Amplifiers and DIY modules
  Reply With Quote
Old 7th August 2008, 12:45 PM   #27
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Quote:
Originally posted by Robert GS
why is a 200Watt amplifier always better than 2x100W.
Hi,

If voltage swing at one frequency was all that mattered then the
200W would always be "better" than frequency split 2 x 100W.

/sreten.
  Reply With Quote
Old 7th August 2008, 12:49 PM   #28
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by Robert GS
why is a 200Watt amplifier always better than 2x100W.

Then a 20000Watt ampilfier will be unbeatable unless someone comes up with a 20001Watt
it depends very much on the spread of frequencies in the music signal.

A single tone played through a 200W amp to a speaker is capable of playing louder than the same single tone played through a 100W amplifier to the same speaker. The other 100W amp is sitting idle waiting for it's frequency range to be utilised.

Now apply a two tone signal. If each tone is in the passband of the respective 100W amps and speakers then you can get xSPL from the pair.
Play the same two tone signal through the 200W amp and the maximum SPL is similar to the 100W+100W amps.

But when the frequencies are widely distributed and playing through multiple amp/speaker combinations, the multiple speaker arrangement is capable of playing louder than the single amp/speaker with the same TOTAL power.
Pink and/or white noise would be the logical extension to this SPL contest. 5 active channels each with 100W available into 90dB sensitivity speakers, will play louder than a single channel 500W amplifier playing into a 90dB speaker operating in wideband mode.

Most commentators forget to tell you the conditions for which their statement applies.
__________________
regards Andrew T.
  Reply With Quote
Old 7th August 2008, 12:58 PM   #29
diyAudio Member
 
Robert GS's Avatar
 
Join Date: Sep 2005
Location: Helsingor
I doubt that this thread started out to be a quest for higher SPL, but a gain of better sound quality. In both cases I would simply say active rules, but there is a financial aspect - which often prevents the obvious choice
__________________
GroundSound.com Active Sound - Active Listening
Digital Crossovers, Power Amplifiers and DIY modules
  Reply With Quote
Old 7th August 2008, 01:41 PM   #30
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Hi sreten

The 350Hz "equal power distribution" point is only valid when average spectral power content is considered. However, when peak power requirements are considered (the true criteria for amplifier size selection), the middle point may be around 1Khz. Have you ever seen the waveform from a trumpet on oscilloscope? It has big killer >5Khz peaks repeating at the fundamental frequency. This requires big tweeter amplifiers for proper playback.

Active systems can produce 6dB higher output than initially expected in the crossover overlap region. Bessel filters (with global EQ to lift the wide 1dB hole that results) may be employed to make that region intentionally wider (like one octave for LR24) without resorting to lower crossover slopes. 250Hz is a great place for this (lots of kick without clipping).

Not to mention that several amplifiers clipping each one its own frequency range sound much better than a single one clipping all frequencies together.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  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
Passive or Active Crossover before amp Zero One Parts 1 6th May 2009 12:17 PM
Passive crossover into active crossover hahfran Multi-Way 16 10th February 2008 06:16 PM
subwoofer crossover passive and active yikchean Subwoofers 3 3rd December 2006 02:18 PM
high pass crossover - active, passive, simple or complex? nick78 Parts 1 23rd May 2006 06:43 AM
using passive crossover before amps to active biamp? cowanrg Multi-Way 7 29th October 2004 01:45 AM


New To Site? Need Help?

All times are GMT. The time now is 12:58 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