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B1 Active Crossover
B1 Active Crossover
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Old 3rd November 2015, 02:57 PM   #441
Rush is offline Rush  United States
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Quote:
Originally Posted by AndrewT View Post
I would recommend separating the EQ and "effects" from the crossover.
A crossover PCB separate from the EQ & effects PCB will make each PCB much simpler and save having to throw away good parts when something is changed.
I agree with Andrew.
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Old 3rd November 2015, 03:04 PM   #442
damuffin is offline damuffin  Canada
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Compression driver EQ would be very popular for the horn crowd. All that is needed is a CR filter with adjustable gain.I agree with Andrew in keeping things simple but the CD EQ is something that should be considered.

Great work it's looking very nice.
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Old 3rd November 2015, 03:54 PM   #443
prooptiki is offline prooptiki  Greece
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Quote:
Originally Posted by AndrewT View Post
I would recommend separating the EQ and "effects" from the crossover.
A crossover PCB separate from the EQ & effects PCB will make each PCB much simpler and save having to throw away good parts when something is changed.
Green areas I believe = separate pcbs !!!
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Old 5th November 2015, 09:06 PM   #444
Kreisky is offline Kreisky  Italy
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Quote:
Originally Posted by Rodeodave View Post
I'd still like to see the pcb happen.

I'm currently reevaluating the configuration of the XO. What's you guys' opinion on the following:
  • BSC followed by another buffer AFTER the low pass
  • Output level control followed by another buffer AFTER the high pass

That way we should end up with better S/N ratio, no? And since tweeters (or midrange in 3 way systems) are generally more sensitive than woofers, only the HP branch needs a relative level control, no?
I suppose (?) AndrewT was suggesting such a configuration in these posts.
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Old 18th November 2015, 05:35 AM   #445
erez1012 is offline erez1012
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Hi expert's
Build this active crossover B1 scheme and its fun 
I have 2 FR speakers, 100Hz cutoff 2 woofer, I want to build only one LF and one amplifier to the woofers.

What is the best way to mix the signal in this B1?
Another Q: the first stage can feed all the filter (HPr,HPl,LP) ?

thanks
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Old 18th November 2015, 08:22 AM   #446
AndrewT is offline AndrewT  Scotland
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The modified tapping point to preserve the HF roll off slope has not been incorporated.

The input Buffer (the first two K170 on the extreme left) is designed to drive the next filtering stages. The Idss of the K170 will determine how many stages can be driven.
The lower Gr grade may be suitable for two filter stages. The Bl grade should easily drive three or more stages. Note each capacitor that follows the Buffer has a 10k2 resistor in series. That makes the filter stage an easy load. All the filter needs is a lowish source impedance to achieve the predicted frequency cut off and Q

If you know your driver sensitivities, you can predict which channel (Hi Pas or Lo Pass) needs a bit of attenuation. It is extremely unlikely that both channels need an attenuation adjustment. In general the higher sensitivity Driver is the treble and this is the one that needs the adjuster and Buffer. The lower sensitivity driver can omit the extra adjuster and omit the Buffer that follows.

Consider whether any input and/or output DC blocking capacitors may give some peace of mind.
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Last edited by AndrewT; 18th November 2015 at 08:28 AM.
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Old 18th November 2015, 08:31 AM   #447
erez1012 is offline erez1012
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i have the BL, so i put one stage buffer for the 2*HP, and one for the mono LF.

So, how i change the stereo to mono for the LP? 2 Resistor in series before the first buffer?

in my case is 100Hz cutoff so:
Frequency = 106.39 Hz
R = 22. k Ohms
C = 68. nF

Last edited by erez1012; 18th November 2015 at 08:35 AM.
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Old 18th November 2015, 08:52 AM   #448
AndrewT is offline AndrewT  Scotland
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For mono you should really be using a summing stage.
The signal out of the summing stage is the SUM of the two input signals when the two signals are in phase.
At LF the signals are supposed to be in phase, thus you can expect the LF summing stage output to be twice the filtered single stereo signal.
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Old 18th November 2015, 09:14 AM   #449
erez1012 is offline erez1012
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twice is good for open baffle woofer.

what about the next scheme, the fet is the first stage from the filter scheme,

just mix the channel with R1,R2.

do i need capacitor?

what about the 220 ohm and 22k from the filter scheme, remove them?
I donít want the signal back to the stereo signal
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Old 18th November 2015, 09:21 AM   #450
AndrewT is offline AndrewT  Scotland
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The resistor method (passive) is not as good as the summing stage (active).

But worth trying. It may be good enough.
Add a gate resistor at the gate.
You can delete the two capacitors.

The two stereo Buffers feed the two input resistors.

An excellent summing and filter stage is the MFB. It uses just one active stage to both sum and filter a 2pole roll -off. The MFB needs an amplifier, not a Buffer. So start with a FET input opamp. opa134 is good enough. It will run from the same supply rails as the B1
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Last edited by AndrewT; 18th November 2015 at 09:25 AM.
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