| Forum Home | ||||
| Press F1 | ||||
| Thread ID: 36024 | 2003-07-29 01:51:00 | Low Pass Filter | Ron Bakker (356) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 163567 | 2003-07-29 01:51:00 | I am looking for a schematics for a low pass filter for my little home made sub for the PC. I'm no electro wizz but I think I have enough experience to make up a small circuit. I guess a crossover at about 80hz would be good. I have Googled a bit but not really finding any good sites that just have schematics. |
Ron Bakker (356) | ||
| 163568 | 2003-07-29 02:31:00 | Hi Ron: Good idea. have a look at this site: http://www.diysubwoofers.org/ check out the "Audio DIY Links" for more info on schematics & construction details of air cored inductors. Good luck. |
Bazza (407) | ||
| 163569 | 2003-07-29 02:50:00 | Do you want an active filter (to work at the preamp level), or a passive (coils and capacitors) to work at the output of the power amplifier? A search for "active filter site:edu" would probably find a few, "active filter tutorial" might be better. |
Graham L (2) | ||
| 163570 | 2003-07-29 10:31:00 | If you just want a simple low pass filter to connect between the amplifier and the woofer then a two element consisting of a series inductor followed by a parallel capacitor will give an attenuation of about 12 db per octave which should be ok. If your speaker has 8 ohm impedance then approximately you would need an inductance of 20milliHenries and a capacitance of 200uF. Preferably the inductance should be air cored, and use something like 16 or 18 SWG. The capacitor should be non polar or 2 electrolytics back to back 400uF each. |
Terry Porritt (14) | ||
| 163571 | 2003-07-29 10:34:00 | Forgot to say if the "crossover" frequency was 160Hz instead of 80Hz, then the values of L and C would be halved, ie 10mH and 100uF. | Terry Porritt (14) | ||
| 163572 | 2003-07-29 11:07:00 | Yes, Terry, thats all helpful & correct. However Ron will need to know how to make an inductance for the value specified. It's all available in the URL I posted above for passive low pass filters, together with the specs of cap & induct for several speaker impedances at the desired frequency crossover. As far as the subwoofer crossover, I can select 60 90 or 120 Hz on my system. I prefer 60, but that is just a personal preference. Your intention to design for 80Hz, Ron seems ideal. |
Bazza (407) | ||
| 163573 | 2003-07-29 11:23:00 | I was a bit thick Bazza, I couldnt find the info on filters first time round, but have now: www.colomar.com At least the calcs agree more or less, mine were back of envelope :) |
Terry Porritt (14) | ||
| 163574 | 2003-07-29 11:35:00 | Yes Terry, nah, not thick, you were 100% correct. Sorry if the links were tricky, but it's all there. I just hope Ron can find his way. The link you found there is the one needed.. Cheers. |
Bazza (407) | ||
| 163575 | 2003-07-29 21:55:00 | Cheers Guys I found a low pass filter in a heap of junk in the garage but I could hear higer tones which means that that the cross over is to high. |
Ron Bakker (356) | ||
| 163576 | 2003-07-29 23:26:00 | It is a 40w 4ohm rms speaker I've done some net surfing & reading so I understand most of what you are saying Terry but what does swg stand for. Is it some kind of term for wire guage. |
Ron Bakker (356) | ||
| 1 2 3 | |||||