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15th January 2015, 02:12 AM  #1 
diyAudio Member
Join Date: Dec 2008

Dynaudio Focus 110 and 140 Crossover Comparison Details
Hi All,
Good day, I know there are a lot of great talent here. So I would really appreciate your answers, feedbacks, and comments on the questions base on the attached Picture layout of both Dynaudio Focus 110 and 140 Crossover schematic. Question: 1) Circuit of Varistor + L4 + 27uF + 10 ohm is a band pass or notch filter for the resonance frequency of the tweeter?  I believe the varistor is the fail safe for the amp consider irregularity of electrolyte cap, is it correct?  Consider the temperament of the electrolyte, what can we expect of the sound when dissipation factor is high or irregular?  Can we perceive the midrange may have some harshness because of non linear behavior of the electrolyte? 2) Circuit 6.8ohm + 1.5uF is for the rising impedance of the tweeter in higher frequency?  Sound wise, what can we perceive if we do not treat this rising impedance, considering the amp will not compensate?  What is your opinion on the sound for well flatten rising impedance? 3) Can I consider the lattice filter of 2 pcs caps and 2pcs Inductors is theoretically to have no contribution to any additional resistance, capacitance, phase, or inductance to the tweeter + and ?  Is the 10uF of the Focus 140 means a wider range of high frequency being subjected to this time delay? If not what is the increased capacitance do? 4) What is your opinion over the additional 22 ohm resistor(not in the Focus 110 crossover) in the crossover for Focus 140 over the Focus 110?  Does it mean the Focus 140 trying to regulate 2 frequency peaks in the high frequency range after the 4.7uF 1st order cross?  Is it better to flatten the impedance peak of Focus 140 using only 1 parallel resistor only instead of 2?  Why do we need the additional 22 ohm resistor in the Focus 140 circuit? 
15th January 2015, 09:02 AM  #2 
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Join Date: Feb 2012

How do you know this is the schematic of said products?
There is still project data available for vintage Dynaudio DIY speakers that employ almost the same filter solution with obviously different part values. Are you sure this is a varistor in series with RLC? In general, your best way to learn what filter does in a circuit is to simulate with a speaker. RLC in parallel with amp out, flattens system impedance, does not change FR. Resistors Rs and Rp define attenuation of tweeter. What you call lattice and series cap shape response. Nothing special and I would say unnecessary complicated. 
15th January 2015, 09:37 AM  #3  
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Join Date: Aug 2014
Location: Laniakea

Quote:
The elco is not in series with the speakers and therefore has no audible influence on the sound. The filter itself is a first order filter (L1 and the 4,7uF cap). If you perceive midrange hardness, that would be my suspect. Quote:
Quote:
The speakers use different mid bass drivers, so the allpass filter needs to be different. Quote:
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15th January 2015, 10:07 AM  #4  
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Join Date: Feb 2012

Quote:
the RC circuit in parallel with bassmid increases the steepness of the LP filter and attenuates higher frequencies. There is no midrange harshness with commercial Dynaudio products. 

15th January 2015, 10:18 AM  #5  
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Join Date: Aug 2014
Location: Laniakea

Quote:
First order filters place a high strain on the tweeter witch could be audible? Just guessing here. I have a very similar Dynaudio design (D28/2 and 17W75XL) and hear no midrange hardness.
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15th January 2015, 11:23 AM  #6 
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Join Date: Aug 2008
Location: Portsmouth UK

Breaking down a complex crossover involves some modelling usually. I did something similar to a B&W Matrix 3:
Could a kind soul please break down this horrid Xover You have a well behaved 4 ohm (?) polycone bass with a simple ca. 1mH coil and Zobel. Only a few 56" woofers will respond to this simplicity, but Dynaudio and Morel are two examples that work. That crisscross lattice tweeter filter is a standard sort of old group delay equaliser, but interestingly, a simple shunt coil does much the same thing. The filter is also found on the ZaphAudio  ZD5  Scan Speak 15W8530K00 and Vifa XT25 So what you have there is second order electrical filters at heart with RC driver impedance correction and some overall LCR crossover impedance correction. And some tweeter attenuation. The Zobel works with attenuation on the tweeter to increase the topend rolloff. A good Dynaudio archive here: Dynaudio archive I would guess the overall acoustic filter is BW3.
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15th January 2015, 11:32 AM  #7  
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Location: Laniakea

Quote:
What are the parts that make up the second order filter?
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15th January 2015, 12:19 PM  #8  
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Join Date: Aug 2008
Location: Portsmouth UK

Quote:
On the tweeter, the lattice filter adds an inductance to the first order capacitor. It's certainly not 6dB/octave overall rolloff. That would sound terrible. But really, it's the wrong way to look at it. You combine the electrical filter with the mechanical filter of the drivers to get something reasonable like 1218dB/octave rolloff and do your thing with phase alignment, however it works out. The example 5" Dynaudio 15 W75 has considerable internal damping and very low inductance. A unique sort of driver. You can see how a second order bass/third order tweeter filter is best combined with natural rolloff below.
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Best Regards from Steve in Portsmouth, UK. 

15th January 2015, 12:39 PM  #9  
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Join Date: Aug 2014
Location: Laniakea

Quote:
If I have time, witch atm I have not, I'll do some measurements and see what the electrical filters are. I agree on the mechanical+electrical filters stuff.
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15th January 2015, 01:16 PM  #10 
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Join Date: Dec 2008

Hi guys,
Thanks a lot for the responds. But will be grateful if you answer the questions in my 1st post. Only Tattoo did answer some of my queries that I am looking for. Sorry for be straight forward, don't mean to be rude. 
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