Active filter board GB

BobEllis · 20th February 2006, 10:01 PM

Looking for interest in a group buy of active filter boards.

WIKI

Each board will be suitable for a one channel two way will contain provisions for:

input buffer that can include BSC
4th order HP and LP
2 Notch/Peak filters
one output buffer with variable gain

I'd like to see added

2 All pass sections

If we add jumpers to allow re-ordering the sections, the notch filters could act as the output buffer on one stage.

Preliminary board layout HERE

harryeng · 20th February 2006, 10:15 PM

Interested! (And added to the Wiki)

Great work.
Harry

Nisbeth · 20th February 2006, 10:29 PM

Added my interest to the wiki.

FWIW, an on-board PSU would be a plus for me but the all-pass filter option isn't something I think I have much use for

/U.

BobEllis · 20th February 2006, 10:49 PM

See www.linkwitzlab.com/filters.htm (also the crossover page) for a dissertation on the utility of all pass sections. The nutshell version is that they allow you to correct for phase differences due to driver acoustic center offset and crossover induced phase shifts without resorting to staggered frequencies in the high and low pass sections.

I read SL's "Active crossover circuits that do not include phase correction circuitry are only marginally useable." as a bit of pomposity until I tried it. The difference was instantly recognizable on transients. (the drivers were old Focal coated paper woofers and kevlar tweeters) My disinterested then 13 year old son noticed right away when I added the all pass section and stopped playing his video game to listen. Transient attacks became sharper and clearer.

If you build properly sloped baffles you can get away without the all pass.

Maybe the board can grow a little and keep the regs while adding the all pass sections. Jens does the software you are using at home support this?

BobEllis · 21st February 2006, 01:08 AM

For those wondering, this board is intended to be a final board. I suggested jumpers in the MOX thread as a way of making it flexible for a variety of projects, rather than adjustable. Some may need two EQs on a high pass section, some may use it as a bandpass, etc.

I envision that jumpers would be wires soldered in place rather than the adjustable set in the MOX

troystg · 21st February 2006, 01:49 AM

I'm in but my 500Mhz P2 PC is having a hard time with the Wiki...

I guess it's finally time to get that dual core 2.8 GHz I was looking at...

At least I upgraded OS from Windows 3.1 last yr.... LOL

pinkmouse · 21st February 2006, 01:52 AM

The Wiki is having "issues" at the moment...

500? That's 150 faster than my iMac!

troystg · 21st February 2006, 01:56 AM

Off topic but....

Pink mice and iMACs... Your a strange fella...

Can you feel the love Al?

pinkmouse · 21st February 2006, 02:00 AM

All the time, mate, all the time!

I'll have to check my finances, this looks like a good project.

BobEllis · 21st February 2006, 03:59 AM

Just to save bouncing between threads, I have attached a spreadsheet for caclulating component values for HP, LP, shelving LP and notch/peak EQ sections

20th February 2006, 10:01 PM	#1
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	Active filter board GB Looking for interest in a group buy of active filter boards. WIKI Each board will be suitable for a one channel two way will contain provisions for: input buffer that can include BSC 4th order HP and LP 2 Notch/Peak filters one output buffer with variable gain I'd like to see added 2 All pass sections If we add jumpers to allow re-ordering the sections, the notch filters could act as the output buffer on one stage. Preliminary board layout HERE

21st February 2006, 01:49 AM	#6
troystg diyAudio Member Join Date: Apr 2004 Location: Lousy Anna	I'm in but my 500Mhz P2 PC is having a hard time with the Wiki... I guess it's finally time to get that dual core 2.8 GHz I was looking at... At least I upgraded OS from Windows 3.1 last yr.... LOL __________________ Troy Thinking positive doesn't make things better, it makes you a better person.

21st February 2006, 01:52 AM	#7
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	The Wiki is having "issues" at the moment... 500? That's 150 faster than my iMac! __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

21st February 2006, 01:56 AM	#8
troystg diyAudio Member Join Date: Apr 2004 Location: Lousy Anna	Off topic but.... Pink mice and iMACs... Your a strange fella... Can you feel the love Al? __________________ Troy Thinking positive doesn't make things better, it makes you a better person.

21st February 2006, 02:00 AM	#9
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	All the time, mate, all the time! I'll have to check my finances, this looks like a good project. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort


	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

20th February 2006, 10:15 PM	#2
harryeng diyAudio Member Join Date: Dec 2004 Location: Roosendaal	Interested! (And added to the Wiki) Great work. Harry

20th February 2006, 10:29 PM	#3
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	Added my interest to the wiki. FWIW, an on-board PSU would be a plus for me but the all-pass filter option isn't something I think I have much use for /U.

20th February 2006, 10:49 PM	#4
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	See www.linkwitzlab.com/filters.htm (also the crossover page) for a dissertation on the utility of all pass sections. The nutshell version is that they allow you to correct for phase differences due to driver acoustic center offset and crossover induced phase shifts without resorting to staggered frequencies in the high and low pass sections. I read SL's "Active crossover circuits that do not include phase correction circuitry are only marginally useable." as a bit of pomposity until I tried it. The difference was instantly recognizable on transients. (the drivers were old Focal coated paper woofers and kevlar tweeters) My disinterested then 13 year old son noticed right away when I added the all pass section and stopped playing his video game to listen. Transient attacks became sharper and clearer. If you build properly sloped baffles you can get away without the all pass. Maybe the board can grow a little and keep the regs while adding the all pass sections. Jens does the software you are using at home support this?

21st February 2006, 01:08 AM	#5
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	For those wondering, this board is intended to be a final board. I suggested jumpers in the MOX thread as a way of making it flexible for a variety of projects, rather than adjustable. Some may need two EQs on a high pass section, some may use it as a bandpass, etc. I envision that jumpers would be wires soldered in place rather than the adjustable set in the MOX

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

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
Active filter board GB	BobEllis	Solid State	0	21st February 2006 10:30 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