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Old 15th June 2012, 05:07 PM   #1
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Default Active xover help.

I have this xover and want to add some EQ. A notch filter centered on 2kHz with 3dB of cut, and baffle step comp. for a 300mm wide cabinet. Can anyone advise?
I will post more details later.http://www.diyaudio.com/forums/galle...hematic_22.png

Last edited by awkwardbydesign; 15th June 2012 at 09:55 PM.
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Old 15th June 2012, 07:57 PM   #2
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Your thumbnail drawing doesn't seem to enlarge.
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Old 15th June 2012, 08:06 PM   #3
tinitus is offline tinitus  Europe
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nope

may be caused by enlarging before uploading

anyway, you will find some curcuit describtions on ESP site
look in the Crossovers and Effects section, and also in the Musical Instrument section
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Old 15th June 2012, 09:56 PM   #4
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Fixt. I'll give more details tomorrow. I've looked on the ESP site and still need help!

Last edited by awkwardbydesign; 15th June 2012 at 09:58 PM.
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Old 15th June 2012, 10:07 PM   #5
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If those are XLR connectors, they're connected very non-standard. Beware of compatability. Or maybe it's just typos.

All good fortune,
Chris
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Old 15th June 2012, 11:14 PM   #6
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I find puzzling things in this schematic, such as 1. an inverting input buffer that lowers input signal to about 1/7th , with the non-inverting input connected to ground through a noise generating 2,7Kohm, 2. + and - have been reversed in the drawing for the filter opamps. It is the topology of a VCVS filter, which is a bandpass configuration. I don't think it will even work. 3. Why capacitive coupling to the output buffers? Input is already decoupled.

Perhaps you can visit Sigfried Linkwitz' site, where you can learn a lot about designing Sallen-Key filter based xovers, which are guaranteed to work.

vac
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Old 16th June 2012, 03:28 PM   #7
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Quote:
Originally Posted by Chris Hornbeck View Post
If those are XLR connectors, they're connected very non-standard. Beware of compatability. Or maybe it's just typos.

All good fortune,
Chris
They are typos. I don't know how to change them in TinyCad, which is were I drew this. I am not very good with computers, and this is my first attempt to post a schematic.
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Old 16th June 2012, 04:21 PM   #8
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Quote:
Originally Posted by vacuphile View Post
I find puzzling things in this schematic, such as 1. an inverting input buffer that lowers input signal to about 1/7th , with the non-inverting input connected to ground through a noise generating 2,7Kohm, 2. + and - have been reversed in the drawing for the filter opamps. It is the topology of a VCVS filter, which is a bandpass configuration. I don't think it will even work. 3. Why capacitive coupling to the output buffers? Input is already decoupled.

Perhaps you can visit Sigfried Linkwitz' site, where you can learn a lot about designing Sallen-Key filter based xovers, which are guaranteed to work.

vac
You are correct, + and - are the wrong way round. Please be patient with me, as I am struggling to use the CAD programme, and I can't put things in the way I want to. I used an opamp symbol, but must have picked the wrong one!
This design does work, I have been using it on and off since 1982 as a 2 way, but I have only just added the 2 MF circuits. The new 4 way setup is installed in it's case, so I don't want to start again! Everything is to Ben Duncan's original specs. with some updates, such as the Linkwitz alignment resistors for the MF1 and MF2 bandpass filters. I will only be using MF2 for the midrange.
Originally there were also caps after the output buffer opamps, but they have been cut. I wasn't sure if it would be safe to also remove the caps before the buffers.
I am fine making speaker cabs, casework, etc, but the electronic calculations give me a headache! Which is why I need help.
The input buffer attenuatiion was explained in the original notes as compensating for the gain later on. I hope that makes sense, as I am just following a published design (HiFi News March 1981).
What I am hoping to do is add is an equalising circuit, perhaps like the ESP Constant Q Graphic Equaliser project#75, before the attenuator pots. Also if possible I would like to stick with the AD825 opamp, as long as it is stable in this configuration, as I find I like the sound of them. Of course, I am open to advice on that.
I realise I am asking quite a lot, but I just don't have the expertise myself.
Also I want to add baffle step compensation, perhaps a simple circuit like the ESP design, which I hope could be added after the output buffer opamp. That is less important at the moment, as it could be added to the speaker as a passive.
I will try to add pics or diagrams if I can work out how.http://i1134.photobucket.com/albums/...n/Untitled.jpg http://i1134.photobucket.com/albums/...leparts011.jpg

Last edited by awkwardbydesign; 16th June 2012 at 04:37 PM.
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Old 16th June 2012, 11:12 PM   #9
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Has the schematic posted before been deleted because of IP?
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Old 17th June 2012, 08:50 AM   #10
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Quote:
Originally Posted by vacuphile View Post
Has the schematic posted before been deleted because of IP?
Don't understand, what does "IP" mean? I edited the first post to make the schematic readable, is that what you mean? Or have I accidently deleted something else? I don't think I posted a different layout, but I AM struggling to get the images posted. Sorry about that, I realise I am not making it easy for anyone who might want to help, and I can only get to the computer occasionally.
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