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
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
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?
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?
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
I envision that jumpers would be wires soldered in place rather than the adjustable set in the MOX
Even though I'm about to order my components for my stripboard crossover, this GB is likely to come in before I start soldering!
Could you maybe expand the wiki to explain what it is we are expressing interest in, ie what the current configuration is and what is being debated. And also how many are needed for typical configurations, as I'm a bit slow tonight.
For my 2-ways I want BSC, 4th order HP, 4th order LP, LT, 1xGain, and a notch/peak or 2. I think the board gives me everything but the Linkwitz Transform.
Can the all-pass section be used as something else instead?
Could you maybe expand the wiki to explain what it is we are expressing interest in, ie what the current configuration is and what is being debated. And also how many are needed for typical configurations, as I'm a bit slow tonight.
For my 2-ways I want BSC, 4th order HP, 4th order LP, LT, 1xGain, and a notch/peak or 2. I think the board gives me everything but the Linkwitz Transform.
Can the all-pass section be used as something else instead?
Wow...this looks great!! I had started to draw something like this up for myself, but Jens' design looks way better than mine.
--I also think that a 4th order allpass section should be included (though I realize that that requires 4 more opamp stages ... 2 more IC's.)
--A on-board PSU I could take or leave, I mean, you'll have a PSU for your amp, right?
--Is it possible to add resistive mixing of L & R channels to use this on a subwoofer, too?
Looking at the schematic, it looks like this is designed as a band-pass board. Is there any way to split out the HP and LP outputs so that the board could be used with both filter sections for one driver, or e.g. HP for tweet and LP for woof.
Potentially, this could reduce the # of boards needed for a project, no? I mean, tweeters generally don't need an LPF section, right?
I suppose if the boards are cheap enough it doesn't matter.
Just my humble $0.02
--Greg
PS -- I'll add myself to the wiki once I figure out how many I'll need.
--I also think that a 4th order allpass section should be included (though I realize that that requires 4 more opamp stages ... 2 more IC's.)
--A on-board PSU I could take or leave, I mean, you'll have a PSU for your amp, right?
--Is it possible to add resistive mixing of L & R channels to use this on a subwoofer, too?
Looking at the schematic, it looks like this is designed as a band-pass board. Is there any way to split out the HP and LP outputs so that the board could be used with both filter sections for one driver, or e.g. HP for tweet and LP for woof.
Potentially, this could reduce the # of boards needed for a project, no? I mean, tweeters generally don't need an LPF section, right?
I suppose if the boards are cheap enough it doesn't matter.
Just my humble $0.02
--Greg
PS -- I'll add myself to the wiki once I figure out how many I'll need.
When you split the HP and LP sections you lose the possibility of using it as a bandpass filter.
I would prefer one input buffer then splitting into two equal sections with EQ,HP,LP and output buffer.
All sections including the HP and LP Op-amps should be jumpered so you can chose between 2 th or 4 th order.HP,LP or BP with or without EQ.
I would also like the option of a input capacitor.
Just my preference though.
btw. is there a reason for using the input buffer for gain instead of the outputbuffer? 6 dB seems a lot, 2 or 3 dB should be more then enough.
regards.
kro5998
I would prefer one input buffer then splitting into two equal sections with EQ,HP,LP and output buffer.
All sections including the HP and LP Op-amps should be jumpered so you can chose between 2 th or 4 th order.HP,LP or BP with or without EQ.
I would also like the option of a input capacitor.
Just my preference though.
btw. is there a reason for using the input buffer for gain instead of the outputbuffer? 6 dB seems a lot, 2 or 3 dB should be more then enough.
regards.
kro5998
Can somebody tell me if this is the sort of thing that I need for my new loudspeaker project ? 
Nuuk,
It really depends on what you need - Once the sections are split, it should handle dipole EQ (1st order Shelving Low Pass + a notch) and still do up to 4th order HP and LP, with an extra notch thrown in. To make the XO shown in your thread would take two boards per channel.
Of course the catch is that we have to sweet talk Jens into making these changes, since I am not able to do layouts. This started as Jens being bored and I semi accidentally I tried to rope him into doing a board for a group buy.
Keep monitoring this thread and see how the board develops.
It really depends on what you need - Once the sections are split, it should handle dipole EQ (1st order Shelving Low Pass + a notch) and still do up to 4th order HP and LP, with an extra notch thrown in. To make the XO shown in your thread would take two boards per channel.
Of course the catch is that we have to sweet talk Jens into making these changes, since I am not able to do layouts. This started as Jens being bored and I semi accidentally I tried to rope him into doing a board for a group buy.
Keep monitoring this thread and see how the board develops.
Hi,
I have decided to create this project in Eagle V4.14 light.
This means that anybody can edit the files for their later requirements because the free version of eagle can handle the board which is limited to 8 x 10 cm.
I will have room for about 8 to 10 dual opamps and their surrounding passive components + a +-15V power supply to drive the whole thing from any transformer (rectifier bridge on board)
May I suggest the following be considered?
1) Input stage (single ended or balanced what gain should it have?) I prefer single ended.
2) Number of filter sections (and outputs) and filter order
3) Number of EQ sections (What topology)
4) Output buffer
5) Anything else??
\Jens
I have decided to create this project in Eagle V4.14 light.
This means that anybody can edit the files for their later requirements because the free version of eagle can handle the board which is limited to 8 x 10 cm.
I will have room for about 8 to 10 dual opamps and their surrounding passive components + a +-15V power supply to drive the whole thing from any transformer (rectifier bridge on board)
May I suggest the following be considered?
1) Input stage (single ended or balanced what gain should it have?) I prefer single ended.
2) Number of filter sections (and outputs) and filter order
3) Number of EQ sections (What topology)
4) Output buffer
5) Anything else??
\Jens
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.