Any one used Vifa PL18 225/8 version?

[JC Fardo]

In advance thanks

[mcp]

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

[peterpan]

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.

[mcp]

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

[JC Fardo]

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

[peterpan]

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

[capslock]

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 PL18WO09-08, but it has a 40 mm voice coil. Maybe the 225 is a custom part for ASE?

Regards,

Eric

[mcp]

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 mid-range back wave.

Regards

[mcp]

Thanks Eric, now I know why I couldn't find a PL18 225/8 in my Vifa catalog.

originally posted by peterpan
Still need some help, is 100p=0.1uF,and 10p=0.01uF ?

100p is not 0.1uF
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 (note-6 decimal places).

nF means nano farad. This is 1 Farad x 10^-9.
So, 1nF=0.000000001 F (note-9 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 (note-12 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

[JC Fardo]

Michael:

I kept the construction as simple as possible

By the tw62 pics the drivers aren´t flush mounted as usual. Right? Any audible difference.

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

JC