Whacky resistor question

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khaosman
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Whacky resistor question

Postby khaosman » Fri Jul 07, 2006 6:18 pm

Finally getting around to putting together this speaker for my sister: http://www.partsexpress.com/projectshowcase/unicc/index.htm

However, I don't have all the resistors. I am missing the following values: .220 ohm, .44 ohm, and 1.18ohm resistors. I can find a Mills 1.2ohm resistor at PE that should work well.

But for the other values, I can't find any thing close that is in the non-inductive category. Will other other 10w resistors like this http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=016-.22 work okay? It doesn't state that they are non-inductive. Also, the Mills is a 12watt resistor and it seems most of these are 10w. Not sure if that will make much of a difference or not.

Thanks for the help, I appreciate it. I've been working (more like not working) on these speakers for a long time. I need to finish this project up!
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crazyray
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Postby crazyray » Fri Jul 07, 2006 8:44 pm

From the description on PE:
Dayton Titanium and Audax TWO25F1

All the inductors are 18 gauge and the resistor directly adjacent to the inductor is its DCR. The one exception is R2031 in Net 2, which is a 5 ohm resistor + the inductor DCR of .26 ohm. L2021 in net 1 was deliberately spec'd to have the rather large DCR of 1.18 ohm. This raised the impedance minima at 100 Hz to be just below 5 ohms, and besides making this for all practical purposes an 8 ohm speaker, helps with the baffle step compensation. Changing to a lower DCR inductor will "add" roughly a dB of B.S.C., or adding a 1/2 to 1 ohm resistor in series will remove another dB or so.


For example, on the midrange, L2021 is 0.90 mH. The ERSE 18 ga air core inductor sold by PE has a DCR spec of 0.44. Got it?

The 12 watt rated Mills resistor is just "better" than it has to be...

If you have more questions, I suggest you post on PE's forum. The designer is a regular.

Good luck and enjoy!
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khaosman
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Joined: Thu Feb 06, 2003 4:21 pm
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Postby khaosman » Mon Jul 10, 2006 6:09 pm

Thanks! I'm ordering the parts today, so hopefully I'll have them by the end of the week so I can get this dang thing finished soon. I'll be sure to post pictures and impressions.

I forgot about the PE forum, that is a good idea. I'll be sure to head there if I have any more questions.

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