What do I need to filter bass to a sub?

Boscoe · 24th June 2010, 10:53 PM

Basically just building my sub and have got a single channel amp which is the complete frequency range but i only want 500Hz and below what do I need to do this for a 4ohm speaker? Can I use a crossover calculator and then use a crossover without the tweet or mid-rand outputs?

Thanks

Boscoe

Boscoe · 24th June 2010, 11:06 PM

Okay so I just found the butterworth 3rd order low pass and it says to use a cap with a certain polarity (late i can't think of the name!) so can I just use electrolytic caps or is ther e a certain type needed?

tinitus · 25th June 2010, 01:51 AM

Quote:

Originally Posted by Boscoe

i only want 500Hz and below

then its basicly considered as a common 3way

chris661 · 25th June 2010, 07:25 AM

Does seem very high for a subwoofer. What are you crossing it over to? (some bookshelf speakers, other drivers in that cabinet...?)

Which driver are you using - you need the impedance curve so you can select the impedance for the frequency you want.

Xoc1 · 25th June 2010, 08:50 AM

500 Hz is just below middle C on a piano.
That is a high note for a sub.
Go get a feel for frequencies, listen to some test tones!

Boscoe · 25th June 2010, 09:42 AM

Okay the driver is one I have just lying around and I'm going to change the frequency to 200Hz.

This is what I'm going to use (in the highlighted area)

I am using two 8ohm drivers with both inphase for a sub woofer.

AndrewT · 25th June 2010, 10:26 AM

3pole filter and 200Hz will pass a lot of mid range to the bass only drivers.
Turning off the satellites, you will clearly recognise the low passed music & songs with all that mid range content.

The filter components will almost certainly be unavailable in 1% values.

5% values are getting a bit wide for a 3pole filter. The tolerance must be tighter for higher pole filters.

4m7H or [4m7H + 100uH] for 4.77
270uF or [220uF+47uF] for 265
1m5H or 1m6H or [1m5+75uH] for 1.59

You may need to add a Zobel correction across the driver terminals to bring the driver load closer to the assumed 8ohms that your calculator uses.

Personally, I would add an active filter in front of the power amp and drive each 8ohm speaker with one half of a stereo amplifier. The active filter could be a CFP which inverts the signal and also capable of summing two (or many) channels to a mono channel.

Xoc1 · 25th June 2010, 01:38 PM

Quote:

I would add an active filter in front of the power amp and drive each 8ohm speaker with one half of a stereo amplifier.

If you use an active filter and a separate amplifier you are far more likely to get a satifactory result.
Also if you are not happy with the frequency response, you will be able to modify it with a few pence worth of components.
At the moment if you build this passive filter, and your not happy with the result (which is very likely) you will end up with a expensive load of junk!

Lee in Montreal · 26th July 2010, 01:39 PM

Paradigm x30 sells used for under $100.
Infiniti makes a similar device.
Or get a 2/3 way stereo active crossover from Behringer for $99.00usd. Being adjustable is a major plus with any project. I have just ordered a CX3400. Or get a costlier digital unit such as the dcx2496 for $299.00

BTW A subwoofer will want a frequency cut-off at 50 or 80Hz. Not 200Hz.

24th June 2010, 10:53 PM	#1
Boscoe diyAudio Member Join Date: Feb 2010 Location: England	What do I need to filter bass to a sub? Basically just building my sub and have got a single channel amp which is the complete frequency range but i only want 500Hz and below what do I need to do this for a 4ohm speaker? Can I use a crossover calculator and then use a crossover without the tweet or mid-rand outputs? Thanks Boscoe

25th June 2010, 07:25 AM	#4
chris661 diyAudio Member Join Date: Feb 2008 Location: Sheffield Blog Entries: 8	Does seem very high for a subwoofer. What are you crossing it over to? (some bookshelf speakers, other drivers in that cabinet...?) Which driver are you using - you need the impedance curve so you can select the impedance for the frequency you want. __________________ "Throwing parts at a failure is like throwing sponges at a rainstorm." - Enzo My setup: http://www.diyaudio.com/forums/multi...tang-band.html

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
bass filter	mlkirchgessner	Car Audio	3	1st March 2007 02:52 PM
Bass beat filter	malc c	Everything Else	9	2nd January 2007 09:57 AM
Active filter for bass dipole	felixx	Multi-Way	1	7th December 2006 12:05 PM
Help Creating Bass boost filter.	PaulHilgeman	Analogue Source	2	28th February 2003 09:44 AM
subwoofer bass extension active filter?	capslock	Subwoofers	8	12th September 2002 05:05 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

24th June 2010, 11:06 PM	#2
Boscoe diyAudio Member Join Date: Feb 2010 Location: England	Okay so I just found the butterworth 3rd order low pass and it says to use a cap with a certain polarity (late i can't think of the name!) so can I just use electrolytic caps or is ther e a certain type needed?

25th June 2010, 09:42 AM	#6
Boscoe diyAudio Member Join Date: Feb 2010 Location: England	Okay the driver is one I have just lying around and I'm going to change the frequency to 200Hz. This is what I'm going to use (in the highlighted area) I am using two 8ohm drivers with both inphase for a sub woofer.

25th June 2010, 10:26 AM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	3pole filter and 200Hz will pass a lot of mid range to the bass only drivers. Turning off the satellites, you will clearly recognise the low passed music & songs with all that mid range content. The filter components will almost certainly be unavailable in 1% values. 5% values are getting a bit wide for a 3pole filter. The tolerance must be tighter for higher pole filters. 4m7H or [4m7H + 100uH] for 4.77 270uF or [220uF+47uF] for 265 1m5H or 1m6H or [1m5+75uH] for 1.59 You may need to add a Zobel correction across the driver terminals to bring the driver load closer to the assumed 8ohms that your calculator uses. Personally, I would add an active filter in front of the power amp and drive each 8ohm speaker with one half of a stereo amplifier. The active filter could be a CFP which inverts the signal and also capable of summing two (or many) channels to a mono channel.

26th July 2010, 01:39 PM	#9
Lee in Montreal diyAudio Member Join Date: Oct 2009	Paradigm x30 sells used for under $100. Infiniti makes a similar device. Or get a 2/3 way stereo active crossover from Behringer for $99.00usd. Being adjustable is a major plus with any project. I have just ordered a CX3400. Or get a costlier digital unit such as the dcx2496 for $299.00 BTW A subwoofer will want a frequency cut-off at 50 or 80Hz. Not 200Hz.