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Old 15th August 2006, 08:06 AM   #1
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Default Active 3 way cross over kit.

I managed to purchase a deleted 3 way stereo active crossover kit, old stock. Can you cross over experts comment on it? Also does it look easy to mod it to a 2 way stereo?


http://www.siliconchip.com.au/cms/A_30278/article.html

But it uses the very old fet input quad opamp the TL074
Is there and new you beaut fet input quad on the market that will sub for this, maybe Analog Devices or Burr Brown?

Cheers George
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Old 15th August 2006, 11:44 AM   #2
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After looking a bit closer I think to make it a 2way instead of a 3 way all I have to do is move the source leg of VR3 (VR6) to pin 14 of IC3d and just use the bass and treble rca's and forget about the mid range one, can anyone double check my thoughts?

Then all I need is a decent subsitutes for the tired old TL074's.

Cheers George
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Old 15th August 2006, 11:53 AM   #3
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Take a look at the OPA4134 as a substitute chip - I think the pinout is the same, but verify for yourself.

For two way use, you have it right, unless you want to EQ your woofer or provice a rumble filter. Then just use the Mid out as your low.

Check out sound.westhost.com for a Linkwitz Reilly crossover calculator. I assume that you will want to change the frequencies.

When using a straight L-R crossover, use drivers that are fairly flat for an octave either side of the crossover point. Don't use drivers with big breakup mode peaks unless you are crossing them out a couple octaves below the beginning of the breakup or you are likely to hear the breakup (AKA distortion).

Enjoy.
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Old 15th August 2006, 12:00 PM   #4
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Thanks Bob I'll look into that opamp.
If I just use the high and the low pass as they are, the high pass goes through 2 opamps but the low pass will have to go through 4 opamps, in my post previous to your's I think it a better way for the low pass, as it too will then only go through 2 opamps like the high pass.

Cheers George
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Old 15th August 2006, 12:08 PM   #5
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Hi,

Its a simple 4th order linkwitz/riley crossover.

Completely ignores most of the issues relating to speaker design.

Take a good look around this site to understand active crossovers :

http://www.linkwitzlab.com/index.html

/sreten.
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Old 15th August 2006, 12:29 PM   #6
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Quote:
Originally posted by sreten
Hi,

Its a simple 4th order linkwitz/riley crossover.

Completely ignores most of the issues relating to speaker design.

/sreten.
Yeah but the kit cost me $15aus, and it's worth a try, all it has to do is give a 24db slope at my chosen point of 300hz without humping up or sagging at the cross over, i don't want it to do anything fancy just give me a clean crossover, and more important not get in the way too much, i still like the minimalist approach, dislike too many ic's between source and speakers

And Bob just looked at the OPA4134 it looks the goods but it looks as though it's only available now in SMD, unless i can find old stock somewhere in DIL.

Cheers George
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Old 15th August 2006, 02:07 PM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by georgehifi


Yeah but the kit cost me $15aus, and it's worth a try, all it has to do is give a 24db slope at my chosen point of 300hz without humping up or sagging at the cross over, i don't want it to do anything fancy just give me a clean crossover, and more important not get in the way too much, i still like the minimalist approach, dislike too many ic's between source and speakers

And Bob just looked at the OPA4134 it looks the goods but it looks as though it's only available now in SMD, unless i can find old stock somewhere in DIL.

Cheers George
Hi,

Its very simple to convert to to a two way at 300Hz.

You need to connect the output of IC1a to the output point of 1C3d.
(i.e. to the inputs of IC3c and IC5d - removing other connections)

/sreten.
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Old 15th August 2006, 02:10 PM   #8
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I've had good results wih the OPA4227 in similar circuits.
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Old 15th August 2006, 02:18 PM   #9
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Got fooled by the data sheet saying it was available in DIP14. How about using it with This ? Quickly exceeds the cost of the crossover, though. You might just give it a listen with the TL074s and see if you want to be bothered changing out the opamps. I've heard good things about the OPA2227, so would assume that the 4227 should be nice, too.

As long as your woofers don't have breakup modes <700 Hz. or so and your mids are flat to 150 Hz. you should get acceptable (if not optimal) results. For that price, it is worth a shot! You could build notch filters if required on prototype boards.

For upgrades, consider the bypass caps at the chips and electrolytics in the power supply. You may want to upgrade the power supply if your first listen shows promise.
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Old 15th August 2006, 09:53 PM   #10
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Quote:
Originally posted by sreten


Hi,

Its very simple to convert to to a two way at 300Hz.

You need to connect the output of IC1a to the output point of 1C3d.
(i.e. to the inputs of IC3c and IC5d - removing other connections)

/sreten.
Yeah Streten that way looks even easier, just use the input IC (IC1a) to drive the midrange out and bass out sections, same as what I had in mind except, you were wprking from the front and I came from the rear, I'll see on the board which is going to look the cleanest way of mutilation surgery.

All the OPamps that have been mentioned are hard to get here in Aus or worth a fortune like $23 each for the OPA4227 from Farnell, what a ripoff. And I need 6 fo them that's $138!!!!!!!!

Cheers George
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