Sub crossover help

Nathan1k9 · 6th January 2007, 02:02 AM

I'm really new to the DIY audio stuff and well about a year ago i got a sub(Just the sub no box or anything) for my birthday. i designed a box for it but i still need to make a crossover so i don't mess it up. I have my audio coming from my computer to my one receiver and from the sub out to my other receiver which already controls my other 12" sub(was pre built with crossover). What i need is for someone to design a crossover for my new sub so i can get it going. Any help would be appreciated. Thanks

mikee55 · 7th January 2007, 07:58 PM

Look for Rod Elliott or rather Elliott Sound Products

Perhaps why no one has bothered to reply.Google your question then come here.

Cheers mikee55

Nathan1k9 · 7th January 2007, 10:48 PM

K i found/made the plans for the cross over but now i need to know a good place to order or get capacitors and Inductors. Any ideas??

lndm · 8th January 2007, 12:54 AM

Quote:

Originally posted by Nathan1k9
from the sub out

Does this output put out only the bass? If so, a crossover may not be strictly necessary and might actually be less good.

Nathan1k9 · 8th January 2007, 07:14 AM

All it really does is lower the highs. cause i have hooked up the sub to it before and you can hear pretty much all the noise, plus some cracks and pops from the higher frequencies.

lndm · 8th January 2007, 09:17 AM

It sounds possible that the lowering of the highs means a first order rolloff at some frequency. What you could do is decide on an appropriate frequency and apply one more order of rolloff by way of a crossover on the woofer.

This is typically done with one capacitor, one resistor and one inductor. The resistor and capacitor flatten out the woofers impedance and the inductor does the rolloff.

If you had an impedance plot, that would be most helpful, otherwise any information you can give including your desired frequency. If you're not sure of the frequency to choose, post a bit about your system and setup.

Nathan1k9 · 8th January 2007, 11:17 PM

Well the Frequency i would like it to start to roll off would be about 90-100 Hz. The Sub is 8 ohms.

Quote:

The resistor and capacitor flatten out the woofers impedance and the inductor does the rolloff.

How come for all the things I have done to try and make a plan for the cross over it's only shown Capacitors and Inductors?? I have read a little about flattening the impedance but it's never really said how.

lndm · 9th January 2007, 03:30 AM

Learning about crossovers can become steep if too much is mentioned at once and this might be one possible reason that introductions don't go this far. Basically, filter theory is introduced in it's fundamental form - working into a resistor, but a speaker does not strictly behave like a resistor.

A typical speaker's impedance rises from around 100-200Hz or so and up. This will likely be the main area of interest in your case. An inductor's impedance rises with frequency too, and if the speaker and inductor both are rising, the net effect will be somewhat nullified.

If you try to cross over too low, you'll need to consider the speakers rise in impedance around it's resonance. Better to cross over more than three times the resonance frequency and don't worry about this at this point.

The capacitor is typically between a few uF and several tens of uF depending on the speaker. The resistor should be around 1.25 times the DC resistance of the voice coil measured with a multimeter (probably around an 8 ohm resistor in your case). Your inductor might need to be in the vicinity of 10-15mH.

Take one leg of the capacitor and connect it to one terminal of the speaker. Connect the other leg to one leg of the resistor, and connect the other leg of the resistor to the other terminal of the speaker.

Connect one terminal to ground. Connect the other terminal to one leg of the inductor and the other leg to the positive output of the amp.

Hope this helps.

Nathan1k9 · 9th January 2007, 09:32 PM

This helps a lot. I think i'l try a couple different crossovers to see what i can come up with. All i need to know now is a good place to buy resistors, capacitors and inductors. Any good online site to order from?? I haven't been able to find many places here yet. Thanks

lndm · 9th January 2007, 09:53 PM

I'm not from your half of the world and haven't used them, but I've noticed some Canadians mention this place http://www.partsexpress.com/webpage.cfm?WebPage_ID=31

6th January 2007, 02:02 AM	#1
Nathan1k9 diyAudio Member Join Date: Mar 2006 Location: Canada	Sub crossover help I'm really new to the DIY audio stuff and well about a year ago i got a sub(Just the sub no box or anything) for my birthday. i designed a box for it but i still need to make a crossover so i don't mess it up. I have my audio coming from my computer to my one receiver and from the sub out to my other receiver which already controls my other 12" sub(was pre built with crossover). What i need is for someone to design a crossover for my new sub so i can get it going. Any help would be appreciated. Thanks

7th January 2007, 07:58 PM	#2
mikee55 diyAudio Member Join Date: Dec 2005 Location: West Howe	Have a Google!! Look for Rod Elliott or rather Elliott Sound Products Perhaps why no one has bothered to reply.Google your question then come here. Cheers mikee55 __________________ If it don't work, I'll fix it in the mix! Or visit http://lsdp.proboards.com/index.cgi

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7th January 2007, 10:48 PM	#3
Nathan1k9 diyAudio Member Join Date: Mar 2006 Location: Canada	K i found/made the plans for the cross over but now i need to know a good place to order or get capacitors and Inductors. Any ideas??

8th January 2007, 07:14 AM	#5
Nathan1k9 diyAudio Member Join Date: Mar 2006 Location: Canada	All it really does is lower the highs. cause i have hooked up the sub to it before and you can hear pretty much all the noise, plus some cracks and pops from the higher frequencies.

8th January 2007, 09:17 AM	#6
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	It sounds possible that the lowering of the highs means a first order rolloff at some frequency. What you could do is decide on an appropriate frequency and apply one more order of rolloff by way of a crossover on the woofer. This is typically done with one capacitor, one resistor and one inductor. The resistor and capacitor flatten out the woofers impedance and the inductor does the rolloff. If you had an impedance plot, that would be most helpful, otherwise any information you can give including your desired frequency. If you're not sure of the frequency to choose, post a bit about your system and setup.

9th January 2007, 03:30 AM	#8
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Learning about crossovers can become steep if too much is mentioned at once and this might be one possible reason that introductions don't go this far. Basically, filter theory is introduced in it's fundamental form - working into a resistor, but a speaker does not strictly behave like a resistor. A typical speaker's impedance rises from around 100-200Hz or so and up. This will likely be the main area of interest in your case. An inductor's impedance rises with frequency too, and if the speaker and inductor both are rising, the net effect will be somewhat nullified. If you try to cross over too low, you'll need to consider the speakers rise in impedance around it's resonance. Better to cross over more than three times the resonance frequency and don't worry about this at this point. The capacitor is typically between a few uF and several tens of uF depending on the speaker. The resistor should be around 1.25 times the DC resistance of the voice coil measured with a multimeter (probably around an 8 ohm resistor in your case). Your inductor might need to be in the vicinity of 10-15mH. Take one leg of the capacitor and connect it to one terminal of the speaker. Connect the other leg to one leg of the resistor, and connect the other leg of the resistor to the other terminal of the speaker. Connect one terminal to ground. Connect the other terminal to one leg of the inductor and the other leg to the positive output of the amp. Hope this helps.

9th January 2007, 09:32 PM	#9
Nathan1k9 diyAudio Member Join Date: Mar 2006 Location: Canada	This helps a lot. I think i'l try a couple different crossovers to see what i can come up with. All i need to know now is a good place to buy resistors, capacitors and inductors. Any good online site to order from?? I haven't been able to find many places here yet. Thanks

9th January 2007, 09:53 PM	#10
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	I'm not from your half of the world and haven't used them, but I've noticed some Canadians mention this place http://www.partsexpress.com/webpage.cfm?WebPage_ID=31

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