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Multi-Way Conventional loudspeakers with crossovers

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Old 28th January 2013, 03:50 PM   #11
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???
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Old 28th January 2013, 06:09 PM   #12
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Quote:
Originally Posted by turk 182 View Post
ummm!
i had a look at the link and i think you may have that a little wrong.
i may be mistaken but i believe that the components on the left are intended to represent the equivalent of a loudspeaker and the components on the right are the compensation.
No, I dont think so. Please take a look at the the complete article:
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:
i'm a little unclear as to the L pad configuration your planning and where your putting the two ohm resistor so i'll leave that alone.
Please take a look at Figure 6.1 in the same link above. Resistors 2R0 and 12R are the L-pad resistors. My two ohm resistor would be in series with 2R0, on the left side of it connecting to the capacitor and the inductor.i.e. after the filter.

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.
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Old 28th January 2013, 06:45 PM   #13
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Quote:
8 ohms nominal to a 4 ohms nominal makes a difference since the amp now has to send more current due to reduced impedance
As I already told you difference in tweeter is minimal, but hey... you decide.
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Old 28th January 2013, 06:50 PM   #14
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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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Old 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 x-over 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.
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Old 29th January 2013, 08:59 PM   #16
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Hi, Patnio! I'm working now on a similar project for my girlfriend. The foam woofer surrounds on her old 3-ways disintegrated, and I knew at a glance that redesigning the speakers would be more satisfactory than repairing them. I'm converting them to 8" 2-ways with Vifa drivers and 2nd-order Linkwitz-Riley crossovers.

What you propose with your L-pad 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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