CarAudioForum.com

Go Back   CarAudioForum.com > UseNet Gateway > F.A.Q. > Components

Reply
Old 07-14-2002, 06:22 PM   #1
Lee

Administrator
 
Join Date: May 1997
Location: Pensacola, FL
Posts: 22,209
Lee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond reputeLee has a reputation beyond repute



What is a crossover? ..

Quote:
3.10 What is a crossover? Why would I need one? [JSC]
A crossover is a device which filters signals based on frequency. A high pass crossover is a filter which allows frequencies above a certain point to pass unfiltered; those below that same point still get through, but are attenuated according to the crossover slope. A low pass crossover is just the opposite: the lows pass through, but the highs are attenuated. A band pass crossover is a filter that allows a certain range of frequencies to pass through while attenuating those above and below that range.

There are passive crossovers, which are collections of purely passive (non-powered) devices - mainly capacitors and inductors and sometimes resistors. There are also active crossovers which are powered electrical devices. Passive crossovers are typically placed between the amplifier and the speakers, while active crossovers are typically placed between the head unit and the amplifier. There are a few passive crossovers on the market which are intended for pre-amp use (between the head unit and the amplifier), but the cutoff frequencies (also known as the "crossover point", defined below) of these devices are not typically well-defined since they depend on the input impedance of the amplifier, which varies from amplifier to amplifier.

There are many reasons for using crossovers. One is to filter out deep bass from relatively small drivers. Another is to split the signal in a multi-driver speaker so that the woofer gets the bass, the midrange gets the mids, and the tweeter gets the highs.

Crossovers are categorized by their order and their crossover point. The order of the crossover indicates how steep the attenuation slope is. A first order crossover "rolls off" the signal at -6dB/octave (that is, quarter power per doubling or halving in frequency). A second order crossover has a slope of -12dB/octave; third order is -18dB/octave; etc. The crossover point is generally the frequency at which the -3dB point of the attenuation slope occurs. Thus, a first order high pass crossover at 200Hz is -3dB down at 200Hz, -9dB down at 100Hz, -15dB down at 50Hz, etc.

It should be noted that the slope (rolloff) of a crossover, as defined above, is only an approximation. This issue will be clarified in future revisions of this document.

The expected impedance of a passive crossover is important as well. A crossover which is designed as -6dB/octave at 200Hz high pass with a 4 ohm driver will not have the same crossover frequency with a driver which is not 4 ohms. With crossovers of order higher than one, using the wrong impedance driver will wreak havoc with the frequency response. Don't do it.
Lee is offline   Reply With Quote

Sponsored Links
Help Syrian Refugees Survive. Donate Now!
Or text REFUGEES to 50555 to give $10 to USA for UNHCR
Reply

Bookmarks

Thread Tools
Display Modes

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 Off
HTML code is Off

Forum Jump


All times are GMT. The time now is 09:51 AM.
Powered by vBulletin® - Copyright © 2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 1996 - 2011 by CarAudioForum.com - all rights reserved.