chipamp passive preamp / crossover - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

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
Thread Tools Search this Thread
Old 18th October 2006, 08:46 PM   #1
diyAudio Member
Join Date: Jun 2005
Location: Aberystwyth / Llanelli (wales)
Send a message via MSN to DoomPixie
Default chipamp passive preamp / crossover

Hi all,
I have been toying with the idea for a while now for my "compurter room" system and tonight i started doing some experimenting. My findings are that my speakers are only good down to about 60Hz, The speakers are running from a TDA1554Q based chipamp at the moment (cheap and chearfull) which has an input impedance of about 30K (according to the datasheet).

I am in the process of building a pair of 10" active subs for the system and to begin with i want to build a passive preamp / crossover to control it all.

As an initial experiment i tried to build a 1st order passive line level crossover to filter out 100Hz and below from my main speakers. Plugged it in and as expected the level dropped a little but theres more than enough power in the system for my small room anyway so i am happy with that. the main problem i have is it dosnt seem to be filtering much if anything out.. when i play test tones through the system it seems to act the same as before but at a slightly lower level. as in it will play test tones all the way down to about 30Hz but after 60Hz the level starts to drop off and the speakers start to distort (as they did before).

The corssover used 15K resistor and 166nF capacitor (those are the values i calculated that should work to crossover at 100Hz. My question is is there something wrong with my calculations or is the 1st order crossover a complete waste of time? Or is there somethign else i am missing?

Many thanks,
  Reply With Quote
Old 18th October 2006, 10:50 PM   #2
preiter is offline preiter  United States
diyAudio Member
preiter's Avatar
Join Date: May 2006
First order just means that at 30Hz, the volume will be down 12dB from what it was at 60Hz. You may want to go with a 2nd order crossover.
  Reply With Quote
Old 20th October 2006, 12:53 PM   #3
diyAudio Member
Join Date: Oct 2005
Doesn't a 1st order crossover roll off at 6db per octave? This means that the output at 30Hz will be 6db less than at 60Hz, not 12db less.

Obviously the speaker is probably dropping off naturally by 30Hz, but this is a different thing...
  Reply With Quote
Old 20th October 2006, 01:04 PM   #4
diyAudio Moderator
pinkmouse's Avatar
Join Date: Apr 2002
Location: Rotherham, England
If the mains are ported, try blocking the ports, that might well give you another 6dB roll off, giving you something like a 12dB accoustic filter. Any better needs you to measure.
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 23rd October 2006, 09:13 PM   #5
diyAudio Member
Join Date: Jun 2005
Location: Aberystwyth / Llanelli (wales)
Send a message via MSN to DoomPixie
The speakers arent ported unfortunatley, they are based around a 6 1/2" 2 way infinity car driver in a sealed enclosure and they work really well down to about 50Hz.. but seeing as i have a sub in the system anyway i think it might be worth putting a high pass crossover on the mains..
  Reply With Quote


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 crossover into active crossover hahfran Multi-Way 16 10th February 2008 06:16 PM
Chipamp w/crossover question Tex Houston Chip Amps 1 20th November 2007 06:02 AM
Chipamp with crossover question Tex Houston Power Supplies 0 18th November 2007 10:03 PM
what preamp do you use with your chipamp? jarthel Chip Amps 5 26th June 2007 11:35 PM
Passive Crossover for Passive Subwoofer? Toast_Master Subwoofers 23 30th April 2006 12:14 AM

New To Site? Need Help?

All times are GMT. The time now is 06:53 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2