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C5 & R3 values - accuracy of driver [message #35502]

Fri, 15 March 2002 04:05

Super_BQ
Messages: 37
Registered: May 2009

Baron

Hello Wayne,

I'm curious on the accuracy of my Eminence Delta 15A woofer (used in Theater 4 Pi speaker xover). On their spec. page they show:

Coil Inductance (Le) = 0.86 mH
Coil Impedance (Re) = 6.9 ohms

Using the above, C5 = 18uF and R3 = 8.625

But when using my LCR digital multi-meter to measure the actual woofer I get:

Coil Inductance (Le) = 0.66 mH
Coil Impedance (Re) = 6.5 ohms

Using the above, C5 = 15.62uF and R3 = 8.125 ohms

Should I use C5 & R3 values that I measured with my LCR meter or should I just stick with say a 20mH inductor as mentioned from other previous posts? Is it that Eminence's specification shows a "nominal" value and what I get with my LCR meter will be different?

Brendon

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Re: C5 & R3 values - accuracy of driver [message #35506 is a reply to message #35502]

Fri, 15 March 2002 08:49

dbeardsl
Messages: 127
Registered: May 2009

Master

Hmm.. thats really odd that the inductance is off, try measuring a known inductance to make sure yer meter isn't funny. Thats mainly a function of voice coil winds and diameter, don't how that could change much from unit to unit...

I'll let Wayne tackle the "She needs a 15.62uF cap, She needs it not, She needs a 16.52uF Cap, shee needs it not" problem

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Re: C5 & R3 values - accuracy of driver [message #35509 is a reply to message #35502]

Fri, 15 March 2002 11:15

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

A Zobel woofer damper is a very wide tolerance device. You can change values a great degree and not detect a difference in performance. See pages 61 and 62 of the crossover document, where it shows the difference between a damper using 7.35 and 10 ohms, and 20uF and 24uF. You can't tell 'em apart.

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Re: C5 & R3 values - accuracy of driver [message #35514 is a reply to message #35506]

Sat, 16 March 2002 05:23

Super_BQ
Messages: 37
Registered: May 2009

Baron

Yes my LCR meter is pretty accurate (at least for the inductance goes). I also find it funny that both drivers are not identical spec (with reasonable variances). For each speakers i get an:

Le of 0.66mH & 0.64mH
Re of 6.5 & 6.4 ohms

So for C5 i've installed 15uF Solen capacitor and for R3 I used 7.5 ohm resistor.

Also just finished doing a super duty bracing for the cabinets and letting it set as we speak. Will give a final review after good break-in.

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the past [message #35516 is a reply to message #35502]

Sat, 16 March 2002 11:13

dbeardsl
Messages: 127
Registered: May 2009

Master

Are these the same speakers you said sounded thin a while ago? if so, what did you do to fix them?

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Re: the past [message #35522 is a reply to message #35516]

Sun, 17 March 2002 00:22

Super_BQ
Messages: 37
Registered: May 2009

Baron

Yes they DID sound thin but after doing a super bracing effort on both speakers and RE-DOING the xover - it MADE A WHOLE WORLD OF DIFFERENCE! - will post pictures soon.

The Theater 4 Pi aren't really broken in yet but so far.. they are quite dynamic and fast in sound.

Right now i'm a little annoyed of mis-placing 4 of the woofer screws...

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