Crossover confusion

Bill F. · 7th November 2006, 05:57 PM

I'm looking at this crossover schematic (sorry it's so small), and it's labeled in a way that has me scratching my head. Do I assume correctly that "0u1" is 0.1uF? And 100p--does it mean 100pF, and isn't that the same as 0.1uF? Why label the same value in two different units?

I'd appreciate some feedback about whether I'm reading this correctly. I'm getting ready to buy parts, and I don't want to screw up.

Also, I'd appreciate it if someone with a little more XO knowledge than I would comment on what the system is doing. It looks like the drivers are connected in phase, and the bass section is plainly 1st-order (or maybe 2nd order with driver rolloff?) Does it look like the tweeter section is trying to achieve a 1st-order slope? Or are there other possible alignments where the drivers would be in phase?

richie00boy · 7th November 2006, 06:35 PM

yes 0u1 = 0.1uF
yes 100p = 100pF
no 100pF = 0.1nF

Bill F. · 7th November 2006, 06:48 PM

Ah! Right you are. I went from micro straight to pico and skipped nano. Thanks for setting me straight.

What on earth do such tiny cap values accomplish here? Seems to me like they're EQing the tweeter rolloff, but wouldn't their onset be way out beyond audibility?

lndm · 7th November 2006, 10:13 PM

The reactance of a 100pF capacitor at 20kHz is around 80kilohms. To me it does seem a bit perfectionistic. What about that lone small inductor on the woofer

Bill F. · 8th November 2006, 02:45 PM

Okay, I think I'm beginning to figure this crossover stuff out. I guess it's a 1st-order XO with impedance correction and shelving EQ on the tweeter. Am I right?

But what about those sections of 100pF in series with 100 ohms? Should I just leave them out, or do they actually do something meaningful?

7th November 2006, 06:35 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	yes 0u1 = 0.1uF yes 100p = 100pF no 100pF = 0.1nF __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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7th November 2006, 06:48 PM	#3
Bill F. diyAudio Member Join Date: Nov 2001 Location: SW MI	Ah! Right you are. I went from micro straight to pico and skipped nano. Thanks for setting me straight. What on earth do such tiny cap values accomplish here? Seems to me like they're EQing the tweeter rolloff, but wouldn't their onset be way out beyond audibility?

7th November 2006, 10:13 PM	#4
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	The reactance of a 100pF capacitor at 20kHz is around 80kilohms. To me it does seem a bit perfectionistic. What about that lone small inductor on the woofer

8th November 2006, 02:45 PM	#5
Bill F. diyAudio Member Join Date: Nov 2001 Location: SW MI	Okay, I think I'm beginning to figure this crossover stuff out. I guess it's a 1st-order XO with impedance correction and shelving EQ on the tweeter. Am I right? But what about those sections of 100pF in series with 100 ohms? Should I just leave them out, or do they actually do something meaningful?

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