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25th May 2003, 04:48 PM  #1 
diyAudio Member
Join Date: Jun 2002
Location: Sao Paulo  Brazil

Any one used Vifa PL18 225/8 version?
In advance thanks

26th May 2003, 05:06 AM  #2 
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Join Date: Jul 2002
Location: Vacation Land

Vifa PL18WO0904
Hi JC
I'm not familiar with 225/8 version , but if it is the Vifa PL18 Premium Line model, I know it quite well . I designed 2 speakers with this woofer. You can view them at: http://www.ampslab.com/sm62.htm http://www.ampslab.com/tw62.htm Regards
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Michael Chua 
26th May 2003, 01:55 PM  #3 
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Join Date: Aug 2002
Location: london

Hello MCP, I was looking at your tw62, and saw something like 100p and 10p and 8u2 for your CAP values, please explain what they mean, I know CAP values as uF.

26th May 2003, 02:27 PM  #4 
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Join Date: Jul 2002
Location: Vacation Land

Hi peterpan
That's actually short form used in the industry. 8u2 = 8.2uF 100p=100pF 10p=10pF Ex: 0.1uf=0u1 0.22=0u22 For resistor values: 4.7 ohms=4R7 47 ohms=47R 470ohms=470R 4,700ohms=4K7 47,000ohms=47K Faster to write and less error. Regards
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Michael Chua 
26th May 2003, 02:31 PM  #5 
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Join Date: Jun 2002
Location: Sao Paulo  Brazil

Hi MCP,
Thanks for post. I´m searching PL18 projects on tower cabinet and yours fits my taste. I got same doubts on caps as Pererpan and also some more details about inner bracing and damping method will be very much appreciated Thanks again, JC 
26th May 2003, 03:12 PM  #6 
diyAudio Member
Join Date: Aug 2002
Location: london

Thanks for the reply. Still need some help, is 100p=0.1uF,and 10p=0.01uF ?

26th May 2003, 03:13 PM  #7 
diyAudio Member
Join Date: Feb 2002
Location: Germany

To my knowlege, the 225/8 naming is only used by the German general importer ASE. It means 25 mm VC diameter, 2 layers, 8 Ohms nominal impedance.
The only official Vifa part is the PL18WO0908, but it has a 40 mm voice coil. Maybe the 225 is a custom part for ASE? Regards, Eric 
26th May 2003, 03:15 PM  #8 
diyAudio Member
Join Date: Jul 2002
Location: Vacation Land

Hi JC
I'm glad to hear that the tw62 is what you are looking for. It is a nice speaker, more musical than the bookshelf version  sm62. It is also very practical. As it is, the tweeter height is just about right. You can easily increase the height by making the base plate thicker if you like. About the caps, I think what you may be wondering is what are those across the 8u2, the 100p+100R and 10n+100R. Those are compensation networks. They improve the sound of the tweeter. The main tweeter capacitor is the 8u2 or 8.2uF. This you must have. Then there is the notch filter  1mH+85uF+10R. This helps to reduce the resonance of the tweeter. There is a picture of the internal bracing at: http://www.ampslab.com/step4_cutouts.htm I kept the construction as simple as possible, so that it is easy for diy. The bracing is good enough, but for those with better tools and time they can of course improve on it. The main problem with a design like this, slim and tall, is if you are not careful, the speaker will resonate at a few frequencies, like an echo. Follow my box dimensions and you will be OK. Next important point is internal stuffing. Fill up the space from the bottom to just below the tuning port with loose mineral fibre. This will absorb the main internal echo. Line the back and sides from port upwards to top of speaker with 1 inch thick fibres. That will help to reduce the midrange back wave. Regards
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Michael Chua 
26th May 2003, 03:44 PM  #9  
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Join Date: Jul 2002
Location: Vacation Land

Thanks Eric, now I know why I couldn't find a PL18 225/8 in my Vifa catalog.
Quote:
10p is not 0.01uF In capacitors, you will be working in uF, nF and pF. You will not work in F as F=Farad is a very large value. uF means micro farad. This is equal to 1 Farad x 10^6. Numerically, 1uF=0.000001 F (note6 decimal places). nF means nano farad. This is 1 Farad x 10^9. So, 1nF=0.000000001 F (note9 decimal places). Now comes the smallest, the pF. pF means pico farad. This is equal to 1 Farad x 10^12. Therefore, 1pF=0.000000000001 (note12 decimal places). I think you can see why engineers use uF, nF,pF. It is so much easier than writing all those zeros. Now comes the confusing part. 100pF is the same as 0.1nF. When you convert nF to pF, you multiply by 1000. In other words, 1nF=1000pF and 1uF=1000n. Hence, 0.1uF=100nF and 0.022uF=22nF and 0.001uF=1nF=1000pF Just think in multiples of a thousand. Regards
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Michael Chua 

26th May 2003, 09:01 PM  #10  
diyAudio Member
Join Date: Jun 2002
Location: Sao Paulo  Brazil

Michael:
Quote:
BTW: Very interesting collections of freewares, oscilators, calculators and so on JC 

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