# 2 way ohm load ?



## brandon75173 (Dec 13, 2009)

I am building two computer speakers and using a parts express pre-assembled x-over. With the woofer being 8 ohm and tweeter being 5 ohm, what is the actual load introduced to the amp when wired straight up to the board on the 8 ohm plugin? http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-144

Thanks

Brandon


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## Anthony (Oct 5, 2006)

Tough to say without modeling it in a program. I imagine it doesn't allow the woofer load to stray below 6 Ohms or so (and can call it an 8 Ohm speaker). The tweeter load is typically not high current so even if it dips pretty low the chance of burning out an amp is small. You could always wire in a 3 Ohm resistor in series to make it an 8 Ohm load.

But the real issue is whether or not the pre-canned crossover is a good idea. There are a lot of subtle nuances in speaker design that are fixed or hidden or accetuated through the crossover. Driver resonance peaks, breakup modes, a non-smooth roll-off, baffle step, etc. you also don't say which drivers you are using. Some have known issues, others are a little better to used with these pre made Xovers.

However, you are in luck. Parts Express has an excellent tech support department and their speaker guys can usually model the drivers you are considering with their pre-canned crossovers and tell you if it is a good fit. They may actually recommend that one, but also recommend a few other components for baffle step, level matching (L-pad), etc. It's definitely worth an e-mail or call to them to find out.

Good luck.


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## dyohn (Apr 17, 2008)

That crossover is designed for an 8-ohm tweeter. If you connect a 5-ohm tweeter to it the Xover high pass point will shift from 3KHz to ~ 4.4KHz while the low pass remains at 3KHz. This is not good. Also, what tweeter and what woofer as you'll most likely need to pad the tweeter to match the woofer's sensitivity.

A properly designed passive crossover will present the impedance of one driver at a time to the amplifier. The load will be woofer's nominal impedance below the Xover knee and the tweeter's above it.


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## brandon75173 (Dec 13, 2009)

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=297-429
http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=297-416

Those are the two I am using. Good advice on calling their tech support. I wasnt sure how knowledgeable they are. I thought about adding L-pads as well. I was going to see how out of balance the tweeter was with the woofer first. I am sure I would end up using them as well, so I will go ahead and order. I will call in the morning and try to get what I need here for the weekend. Thanks guys. I am learning little by little. 

Brandon


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## dyohn (Apr 17, 2008)

If you plan to use the Dayton pre-built crossover you need to use an 8-ohm tweeter. This one is decent and in your price range:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=279-179
And yes, you will need to pad the tweeters. Start by adding enough attenuation to lower the sensitivity to match that listed for your woofer.


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## brandon75173 (Dec 13, 2009)

Go easy on me...........I got the resistors. Do I add one to the + and - side or just positive? I assume both, but want to be sure. 

Thanks

Brandon


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## Anthony (Oct 5, 2006)

before the + terminal. So it will go crossover --> resistor --> + of speaker.


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## brandon75173 (Dec 13, 2009)

Great.....thank you. I thought that could be the case.


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