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Active filter board GB

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#461
Dick,

It looks like your all pass circuits are at their steepest phase shift in the crossover region - see the f0 in the spreadsheet showing 3300 Hz.

Try shifting that up by reducing C7 or R10. 2K7 and 10 nf moves the frequency up to 5900 which should keep the phase change fairly consistent through the crossover region. Without much guidance Linkwitz suggests F0>> crossover frequency. He seems to think around an octave is enough, looking through the example on his website.

Although I cannot see how it would matter for interactions, Linkwitz puts is notches after the all pass sections. Having the notch last would tend to attenuate noise from earlier sections, though. I think you'll always get a bit of electrical phase hiccup with a notch, since it is in effect a high pass and low pass section with split frequencies.

Remember, the phase that you are really concerned with is the phase of the output of the speaker. When you combine the filter with the driver's resonance phase shift, I'll bet that hiccup goes away. Measure to be sure.
 
#462
Thanks Bob,

I agree that changing the order of the different elements won't have any effect.
I can try and shift the fo of the all pass filter and see what that brings, but offhand I would think not much.
The essency indeed is that the notch filter is the problem. I suppose only listening will tell me what is best.
Thanks anyway.
Dick.
 
#469
Boards received

Boards received - top drawer quality at resonable prices - thanks all around to Bob, Jens et al.

On a side note: The Danish customs got hold of Bob nice little package and turned my $39 boards into $60 boards... so i guess my boards are more 'highend' than others - they surely did cost me more😀 (No fault of Bobs of course - just joking)

Looking forward to the continued discussion on our active filters. I'm especilly looking forward to discussing choice of components.

And as I'm doing a three-way active I also need to get some idea of phase change through the boards i.e. will there be a larger phase change for tweeter as it passes 2 boards? - or I'm missing something? Someone allready know the answer please enlighetn me! (Meanwhile - Me think me will construct and measure to see...):smash:
 
#470
I think it is easiest to tweak the mid-tweeter phase alignment first, then add the woofer-top crossover. Tweak mid/woofer alignment as needed.

If you want you can have one board do woofer and tweeter filters, the other do the Midrange bandpass. Some say that this arrangement makes it hard to phase align everything, but I haven't tried it.
 
#471
Hi Bob,
Missed the postman yesterday with the board delivery but picked them up today from the local sorting office. All present and correct, very nice boards- excellent quality for beer-budget money. My audiobuddy Ray, who put in for the larger part of the order was equally impressed and he's seen a fair few boards in his professional capacity. Many thanks to you and Jens for putting this together.
All the best,
John.
 
#475
Random observation:

You seem to have everything else for sale on your web page BUT these filter boards. Have you thought about buying a stash of extras for between massive group buys? There seems to be quite a bit of continuing interest in these boards, but of course there is the issue of fronting the cash. Anyway, this is just me "thinking out loud."

David
 
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