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Old 20th April 2013, 08:09 PM   #11
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If I am implementing the values in my original post above, R1 at 10k resistor, I have that, but I messed up and R2 for the 1st order HP I don't have the 16.6667k resistor required, but have two 25k resistors, which is rAmp. Can I use these in the R2 position of the hp? There is a note at bottom but not sure if that applies here.

For 1st order HP set R2 (leave it out) to infininty and use the value of Ramp as the R for the calculation. ie HP consists of a "single" added cap.

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As well, do I just run the input to a common point and each filter hp/lp branches off from there?
Yes.

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Old 20th April 2013, 08:20 PM   #12
mortron is offline mortron  Canada
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So in the R1 input of the HP, I input my amps 25k, and the value is changed to 50.9296 nf... So would that be my value for the single cap in my HP?
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Old 20th April 2013, 08:58 PM   #13
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Yes, 0.05 uF

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Old 21st April 2013, 01:50 AM   #14
mortron is offline mortron  Canada
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Gotten this far...

I haven't run any wiring, they're just soldered to PCB, with the strips all common to each other... Just in case it doesn't sound good, I figured this enclosure will suffice.


Inputs I'm just wiring right from rca to the board, as I am trying to just use parts about the house, only had to buy resistors n caps.


Do I need to isolate the rcas from the case or is it okay as is?

Sorry it's upside down... I give up on tablets and phones.
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Old 23rd April 2013, 05:06 PM   #15
mortron is offline mortron  Canada
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It's up and running... No hum.

BUT!


I am testing one channel of the high pass. I have my preamp connected to the filter then to the power amp. I run one channel into the preamp, and both channels to the filter, but only one RCA to the amp. With one channel connected to a speaker.


One channel works as it should and displays all proper characteristics. When I disconnect input, and put it into the other channel on the preamp, and turn it way up, to maximum (loud) I get some signal still coming through. I assume this is crosstalk.


Is this the filter causing this? Like due to a common ground? Or will it go away when both channels are connected?


I'm scared to try more, as I'm still unsure if its doing anything bad. Otherwise, I'm quite impressed.
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Old 26th April 2013, 07:45 PM   #16
mortron is offline mortron  Canada
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I have it up and running now... very impressive and problem free.

Now I am going to try more XO frequencies out. This is a great way to get into active amplification, and once again, hats off to you for planting the seed Dave.

I see the issue with loss on the LP. I have my amp turned to the maximum volume setting in order to blend with the HP, which is set to 1/5 volume, if that.

I am just using what's at the electronics shop for components, but once I get a setup I like, is there any benefit in buying more audio specific caps and resistors?

Is the 90 degree phase discrepancy with a 1st/2nd order combo a major issue? I have tried to read up on this, but the acoustic/electrical slope distinction has me lost, and couldn't find anything that would answer my questions easily (probably because it's not that easy )
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Old 26th April 2013, 08:40 PM   #17
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but once I get a setup I like, is there any benefit in buying more audio specific caps and resistors?

Yes, but don't go crazy,

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Is the 90 degree phase discrepancy with a 1st/2nd order combo a major issue?
Text book issues fall aside when you start talking about an actual implementaion. Could be insignificant, or worse, or anywhere in between.

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Old 27th April 2013, 01:41 AM   #18
mortron is offline mortron  Canada
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Thanks Dave,

Really appreciate people championing ideas like this. Tomorrow im grabbing caps to try different cutoff frequencies. The affordability is in line with the DIY spirit as it allows experimentation. And many ideas need to be tried to be realized.

Next up is using Duct Seal on my Visatons.
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Old 27th April 2013, 10:36 AM   #19
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A single pole filter introduces a 90degree phase to the signal.
BUT !!!!!
at the crossover frequency where the signal is down by 3dB, the phase is only 45degrees.
If the treble has a high pass then the phase has changed 45degrees and the bass with it's low pass is also changed by 45degrees, but in the opposite direction. The two drivers are being presented with signals at the crossover frequency that are 90 degrees out of phase.

Let's advance to a 2pole filter for each half of the crossover.
The high pass introduces 90degrees of phase at the -3dB frequency and the low pass introduces an opposite 90degrees of phase at the same -3dB frequency.
The two drivers are being presented with a signal that is in exactly 180degrees of phase opposition. There will be a big "null" in the output where the listener/microphone is exactly the same distance from each driver's apparent source point.
Reverse the phase of ONE driver and this will result in the phase matching at the crossover frequency.

Back to the single pole, where we had that 90degree phase error.
This creates a lobe pointed down, or up, from the directly in front position.
If you stand up you can hear the null or reinforced signal due to the phase induced lobe.
Here a sloping baffle may give a partial cure to the single pole phase anomaly.
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Old 19th May 2013, 07:54 PM   #20
mortron is offline mortron  Canada
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So in listening to this... It is apparent there is much above the xo point on the low pass. Did I do something wrong or is it just inevitable I will hear higher noises? Now low end of vocals but like a lot of music. It's supposed to be 60hz second order electric, but not acting as such.
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