Back Again with some question

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glicioto

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Joined 2009
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Hi to everybody,

I posted a pseudo-design some days ago. Many answered me saying: don't get crazy with a 3 ways if you are not expert. Hard but True.

I continued to investigate this world and I decided to study some simple 2 ways designs. I started from the ETON 8.1 kit. It seems a good 2 ways assembly and the Xover did not appear so complicated. Studying it I came to the following doubts which prevent me from a complete understanding of the Xover:

1) If I look to the Woof specs I would have suggested a impedance compensation network (Re=8 ohm + Ce=12 muF) and a RLC filter to prevent the 3kHz peak. If I look the proposed schematic I found an inductot for the realization of the low pass 1st order filter (around 900Hz) and a RLC cell. What the RLC is there for? I do not understand very well this.
2) For the Tw, I recognize a 2nd order filter but I cannot define clearly the frequency (in addition: Capacitor value are expressed in mF and not muF). There is also an attenuator (3.3 ohm resistance) compensated by the parallel 12ohm R.
3) Such 1st + 2nd order filter make me think about an asymmetrical acoustical response overlap. Am I wrong?

So, I put on the table my doubts, is there anyone who could help me in this reverse engineering exercise?

Thanks in advance.

Bye
Gli
 
#2
glicioto said:

1) If I look to the Woof specs I would have suggested a impedance compensation network (Re=8 ohm + Ce=12 muF) and a RLC filter to prevent the 3kHz peak. If I look the proposed schematic I found an inductot for the realization of the low pass 1st order filter (around 900Hz) and a RLC cell. What the RLC is there for? I do not understand very well this.
Click to expand...

The RLC is an input impedance correction benefiting the amplifier and should not affect the output transfer function, unless using a low damping factor amplifier. (like a tube amp) IMO this is a Madisound LEAP design character obtained by optimizing or flattening the input impedance, not the output.

glicioto said:

2) For the Tw, I recognize a 2nd order filter but I cannot define clearly the frequency (in addition: Capacitor value are expressed in mF and not muF). There is also an attenuator (3.3 ohm resistance) compensated by the parallel 12ohm R.
3) Such 1st + 2nd order filter make me think about an asymmetrical acoustical response overlap. Am I wrong?
Click to expand...

Yes you are correct. The 2nd order highpass frequency is f =1/(2*PI*sqrt(LC)). This may or may not determine the actual crossover freq. That usually is determined by the intersection of both acoustical transfer functions. The 1st order low pass shown is mostly for BSC correction and then relies on the MB drivers natural 2nd order further up.

The C values shown by ETON/Madisound PDF should be uF not MF. http://www.eton-gmbh.de/dlstream.php?FileId=81



sidebar> The usual problems with big 8" and dome 2ways esp. using low order xovers, are to be found in the offaxis response transition to the tweeter. Can be done correctly with the right MB cone profiles (ie looking at MB on-axis to off-axis rolloff should more or less overlap near the crossover frequency. This should help for wide dispersion transition to the flat flange type domes.
 
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