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Old 5th February 2010, 05:42 PM   #1
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Question NOS user would appreciate review of PLLXO plans

Hello,
With little time, little money and little electronics knowledge I have gravitated to PLLXOs as a way to bi-amp my system. I have RS 1354a's for the top end in open baffles with two different woofers for bass (quasi Geddes). My plans are to use identical amplifiers for both ranges and split the signal at 100Hz.

I have read what I could find on PLLXOs, finding the site http://www.t-linespeakers.org/tech/f...ssiveHLxo.html to provide the most information. Based on information I've gleaned, I put together a worksheet with the equations and input values:

12 dB / octave PLLXO highpass
.................................................. ...........Equations:
.....R amp...................30,000 Ohm
.....xover........................100 Hz
.....R1..........................3000 Ohm..................R1 input
.....C1.........................530.8 nF....................1/(2*pi*f*R1)
.....R2'.......................15,000 Ohm..................R amp * R2 / R amp + R2
.....R2........................30,000 Ohm..................R2 input
.....C2..........................106.2 nF....................1/(2*pi*f*R2')

6 dB / octave PLLXO lowpass
.................................................. ..........Equations:
.....R amp.....................30,000 Ohm
.....Xover .........................100 Hz
.....R1.............................3000 Ohm...............R1 input
.....C1..............................530.8 nF...............1/(2*pi*f*R1)

First question - with a PLLXO can I mix 1st and 2nd order crossovers?

Second - I changed the calculation of the highpass for R2 (resistor) and R2' (impediance of resistor and amp) so that R2 is input and R2' is calculated.

Third and final - I chose my R1 resistor values as 10 to 15% of the amplifier's input impediance. Is this OK?

If anyone would like a copy of the worksheet I put together for first and second order PLLXOs, put your email in the body of your reply. It is an Excel 97 format which I have uploaded to Google Docs successfully. So if you don't have MS products, get a gmail account and try Google Docs.

Thanks
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Old 5th February 2010, 07:25 PM   #2
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Hi,

No time yet to check your work, but i'd like the spreadsheet. If OK with you, i'll tart it up and post it in the article. We discourage people from posting their emails in posts to minimize spam. You can pull my email off any of my sites (including the TLS.org site)

I used a mixed order PLLXO in Tysen. It worked well. With a 2nd order hi-pass you really need to have an amp with a fairly high input impedance and you can just use that imput impedance as your last R in that part of the circuit.

dave
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