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Do I treat this as a 6 or 8 ohm driver? [message #50413]

Sat, 23 December 2006 02:28

Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA

Illuminati (2nd Degree)

For building a crossover, say at 3500Hz, is this a 6 or 8 ohm?

Fountek Neo CD2 SPL and impedance graph

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Re: Do I treat this as a 6 or 8 ohm driver? [message #50414 is a reply to message #50413]

Sat, 23 December 2006 10:25

Paul C.
Messages: 218
Registered: May 2009

Master

The sheet says 7 ohm impedance. The graph looks like 7.5 ohms over the region on both sides of 3500 hz.

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Re: Do I treat this as a 6 or 8 ohm driver? [message #50415 is a reply to message #50414]

Sat, 23 December 2006 16:16

Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA

Illuminati (2nd Degree)

The graph sure looks like dead nuts on 6 between 3 and 8K. No?

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Re: Do I treat this as a 6 or 8 ohm driver? [message #50416 is a reply to message #50415]

Sat, 23 December 2006 16:30

Paul C.
Messages: 218
Registered: May 2009

Master

Sorry, I had a typo... it is right on 6.5 ohms in that area, not 7.5 as I mistyped.

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Driver impedance [message #50420 is a reply to message #50416]

Sun, 24 December 2006 17:31

Wayne Parham
Messages: 18737
Registered: January 2001

Illuminati (33rd Degree)

I would probably model the driver in Spice. You can see driver resonance in the lower end of the response curve, and rising impedance from voice coil inductance at the higher frequencies. This will allow you to curve fit and find a model. Then again, the impedance curve is pretty mild, so you might just treat it like a fixed impedance of 6.5Ω and calculate your crossover accordingly.

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Re: Driver impedance [message #50424 is a reply to message #50420]

Mon, 25 December 2006 12:12

Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA

Illuminati (2nd Degree)

That's what I was thinking, too. Since it'll only see 2 watts, I'll use a first order at 3500.
I gave myself the CD-2 ribbons for Hanukkah:) They should be here this week. I cut all the pieces for a 1/2 cu ft box yesterday with the front baffle rising up another 7" to hold it. The top of the 2123 and the bottom of the ribbon will be just a few inches apart.

Finished the 2226 cabs this morning and can't wait to hear the completed system.
Merry Christmas to you, Wayne, and your family, especially the newest Parham(s).

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Re: Driver impedance [message #50427 is a reply to message #50424]

Tue, 26 December 2006 09:54

Wayne Parham
Messages: 18737
Registered: January 2001

Illuminati (33rd Degree)

Thanks, Bill. All the best to you and yours this Hanukkah and always. I hope to see you again soon; It's been too long!

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Re: Do I treat this as a 6 or 8 ohm driver? [message #50429 is a reply to message #50413]

Tue, 26 December 2006 17:50

dB
Messages: 234
Registered: May 2009

Master

Hi bill,
(and) If Wayne doesn't mind, he can check this tread later, for reinsurance.

I used it in a "Spice" simulation sometime before (Feb2006), and boy isn'it great?! (in the graphics & simulations I mean)
So, for the Fountek NeoCD2.0 Ribbon Tweeter I used:
R=6.5
L=0.1mH
And also you can go lower about to 2K/2nd Order easily if you want.
Tell us more when you try, as it sound and the xover you go with.
Wayne is of great help allways,
Personally I would put it up w a 2order, but you decide and later share with us your preference.
Best regards

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Re: Do I treat this as a 6 or 8 ohm driver? [message #50431 is a reply to message #50429]

Wed, 27 December 2006 11:10

Wayne Parham
Messages: 18737
Registered: January 2001

Illuminati (33rd Degree)

6.5Ω and 1.0mH is a very reasonable model for that tweeter. It doesn't include mechanical resonance but that isn't needed unless crossover is very low. If the crossover presents only high frequencies to the tweeter, then its mechanical resonance will not interact much with the circuit. Including voice coil inductance in addition to resistance will give a much clearer picture of what is going on in the circuit.

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