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Old 29th September 2004, 04:58 PM   #1
BobK is offline BobK  United States
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Default Electronic Crossover PWB

Attached is a layout for a 3 way electronic crossover. Layout is nearly complete with only the power distribution, decoupling caps, and a few signal routes to finish.

My question is would anyone be interested in purchasing these bare boards? They will be 3x4 inches and, if there is enough interest, in the $20 US price range.

Electrical capability per single channel board is -

1 24db LR Low Pass
1 24db LR Band Pass
1 24db LR High Pass
1 Baffle Step Correction
2 Notch Filters
2 Delay Circuits
2 Buffer Circuits
2 Output Level Pots

Baffle Step and Notch filter RC components will be plugable module circuits onto .1 inch headers X1, SL1, and SL2. The IC's are dual 8pin opamps (I plan on using TI OPA2134's).

I unfortunately will not be able to do much on the finalization until mid October, but could probably have boards available in mid November.

Thoughts, feedback, interest?

BobK
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Old 29th September 2004, 05:53 PM   #2
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Here's one ready to buy.

https://secure11.websitecomplete.com....asp?prod=1126
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Old 29th September 2004, 06:08 PM   #3
BobK is offline BobK  United States
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I know there are a couple of active boards available but I need a three way. Also, to implement an accurate OB design you have to have BS correction, notch filter for most drivers, and phase (delay) compensation. Implementation is much cleaner if you can do this all on one board.
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Old 29th September 2004, 06:59 PM   #4
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Quote:
Originally posted by BobK
I know there are a couple of active boards available but I need a three way. Also, to implement an accurate OB design you have to have BS correction, notch filter for most drivers, and phase (delay) compensation. Implementation is much cleaner if you can do this all on one board.
I would STRONGLY recommend looking at actual capacitor sizes before finalizing layout. Some boards out there specify 0.2 inch (5 mm) spacing between capacitor leads, but available polypropylene parts greater than 0.01 uF will not fit in that space. Using 0.01 uF parts contrains you to resistor values > 100K if you want to cross over around 100 Hz, which some people might not like doing for noise.

I would recommend supporting lead spacings of 5 mm and 10 mm, since that tends to cover the majority of the cases out there, and the occasional 7.5 mm spacing could fairly simply be bent to fit in. Also remember that caps can be fat little bast*rds, too.



Cheers,
Francois.
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Old 29th September 2004, 07:12 PM   #5
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But that is only 2-way...

dave
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Old 29th September 2004, 07:27 PM   #6
BobK is offline BobK  United States
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Francois,

Thanks for your reply. I went back and forth on cap lead spacing and finally decided on .4 inch. This will allow up to a .068uf Vishay Type 715P Polypropylene, or 0.47uf in a Type 225P Polyester.

Thanks again.
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Old 29th September 2004, 08:57 PM   #7
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Sounds like a very complete solution.

Some beginner's questions (for my own understanding) if you don't mind...

The notch, delay, buffer, and output pots would be for the high and band pass circuits?

Could I use this board for a two way speaker and add a subwoofer or woofer later on?

When would you be looking for a commitment?

Any estimates for the cost to populate the board?

regards

Dave
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Old 29th September 2004, 09:23 PM   #8
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How about a schematic and some more details?

Thanks

\Jens
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Old 29th September 2004, 09:55 PM   #9
BobK is offline BobK  United States
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Dave,

The notch circuits can be used to compensate for a peak in a drivers response, or to remove a peak caused by the baffle the driver is mounted on.

The delay circuits are used to compensate the time delay that exists if you mount all of your drivers in the same vertical plane (this is why some passive designs slope the front baffle board). These would be used to delay the tweeter and Mid output so they would be "in phase" at there respective crossover frequencies.

The buffers are used to isolate any filter circuits from following stages. This may be the adjustment pots on the Xover board, or amplifiers you may use that have low input impedences. I will use them between the notch filters and the output level pots.

The pots or trimmers can be used to adjust for efficiency differences between your woofers, mids, and tweeters(only 2). My woofers and mids are more efficient than my tweeter so I will use them to pad the output of the low pass and band pass sections.

You can certainly not use the bandpass section if you are only doing a 2 way. You could reconfigure the board later on to add a woofer.

I would like to order the boards around the end of October. Cost will vary depending on the quality of parts you use. I plan on using OPA2134's but any other dual opamp with the same functionality could be used.

Rough cost -
8 - Opamps @ 2.63
27 - 1% metal film resistors @.20
16 - polyprop caps @ .70
2 trimmers, bypass caps,input cap, headers ~ $11
Power supply ~$20

Rough estimate to do a stereo pair without case would be around
$160.

Hope this helps
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Old 29th September 2004, 10:08 PM   #10
BobK is offline BobK  United States
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Jens,

I don't have a schematic of the board but all of the circuits are from the attached Linkwitz site.

http://web.archive.org/web/200306050...om/filters.htm

I wanted to do a board that would support a varied DIY and prototype environment. The most flexibility would be offered by a board with the above circuits that could be configured by jumpers or point to point wiring between the various functional blocks.

I've admired the projects you have shared with this community and look forward to any suggestions you may have.
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