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MultiWay Conventional loudspeakers with crossovers 

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28th January 2013, 03:50 PM  #11 
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Join Date: Oct 2012

???

28th January 2013, 06:09 PM  #12  
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Join Date: Jan 2013

Quote:
Passive Crossover Network Design Figure 3.1 is the equivalent circuit of a woofer, Figure 3.3 is that of the same woofer with a Zobel network. Similarly Figure 3.6 is that of a tweeter. Perhaps it was wrong of me to just link the picture, but it was the only one that was closest to what I wanted to get across. The diagrams are of an actual equivalent circuit that mimics a loudspeaker. I suppose if one simply wanted to represent a loudspeaker, a simple R, L and C components would do. Quote:
My understanding is from an amp's perspective replacing a tweeter/woofer from one that is 8 ohms nominal to a 4 ohms nominal makes a difference since the amp now has to send more current due to reduced impedance. And this has to be compensated somehow. My solution is to use a series resistor as above. IF someone says that it does not make a difference, I would like to know why. 

28th January 2013, 06:45 PM  #13  
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Quote:
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28th January 2013, 06:50 PM  #14 
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Location: Cascais

If you making a new crossover for the new impedance you are fine also, if not make the impedance seen by the crossover the same (similar tweeter impedance). If you want the impedance to raise, from the side of the amp then placed the resistor between the crossover and amp, as I told in #10.
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28th January 2013, 07:22 PM  #15 
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patnio
you are indeed correct i was looking at the circuit bass ackwards. in the immortal words of Homer J. Simpson "dooh!" as to the L pad adding your 2 ohm resistor would reduce your tweeter level but keep in mind this attenuator is after the filter. the resultant new impedance is not going to put undue demands on your amps output it's not like your simply paralleling another driver. me thinks your neglecting the effect your xover has perhaps. still gotta figure out how to properly use the quote thingy Last edited by turk 182; 28th January 2013 at 07:24 PM. 
29th January 2013, 08:59 PM  #16 
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Join Date: Jan 2013

Hi, Patnio! I'm working now on a similar project for my girlfriend. The foam woofer surrounds on her old 3ways disintegrated, and I knew at a glance that redesigning the speakers would be more satisfactory than repairing them. I'm converting them to 8" 2ways with Vifa drivers and 2ndorder LinkwitzRiley crossovers.
What you propose with your Lpad will certainly work; you can add any value you want to the series resistor. But I think you've got the cart before the horse somewhat if you're taking the rated impedances of your various drivers at face value. My 8" Vifa woofer, for example, measures 13 ohms at my crossover point, 9 an octave below, and 19 an octave above. With compensation, it measures 6.4 ohms plus or minus 0.4 from 150Hz to 20,000. So now it's a stable load, but still not 8 ohms. Don't even get me started on the tweeter. The existing crossover in my gf's speakers was just 2 electrolytic capacitors, nothing more. If yours looks similar, I'd suggest you toss it and start from scratch. Regardless, you really don't know how your crossover will act until you know more about your driver's impedance than simply that it's rated at 4, 6, or 8 ohms. Since you're working up to a better build, I recommend you equip yourself to measure the actual impedance of the drivers you're using at various frequencies. Then start with calculated component values for your compensation circuit, test it, and refine as necessary. The calculated circuit for my woofer was 6 ohms in series with 12uf, but I found the best results using 7.5 ohms in series with 15uf. 
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