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Double checking C5 and R3 values [message #49735] Tue, 18 July 2006 17:55 Go to next message
Norbert is currently offline  Norbert
Messages: 42
Registered: May 2009
Baron
I am looking at the C5 and R3 values for Stage 4 Omega 15 driver.

According to Wayne's crossover table C5 and R3 ahould be 60 uF and 8 Ohms respectively...

Now even if I factor in 25% variation for the Zobel circuit allowance I don't even come cross the values Wayne has for C5. So why the discrepancy?

Omega Pro 15:
Re= 5.28 ohms
Le= 1.04 mH

R3 = 1.25 * 5.28 = 6.6 + 25% = 8.25 Ohms > OK
C3 = Le/Re squared = 1.04 x exp-3/5.28 squared = 37.3 uF +25% = 46.6 uF which is short of 60 uF

Norbert

Re: Double checking C5 and R3 values [message #49740 is a reply to message #49735] Tue, 18 July 2006 22:26 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18689
Registered: January 2001
Illuminati (33rd Degree)

The Omega 15 driver had different specs when I designed the crossover, making the larger Zobel a better deal. But your math is right, so the 40uF cap would work just fine. The 60uF cap will do nicely too, just be five bucks more expensive. Zobels values aren't very critical.


Re: Double checking C5 and R3 values [message #49742 is a reply to message #49740] Wed, 19 July 2006 08:24 Go to previous messageGo to next message
Matts is currently offline  Matts
Messages: 359
Registered: May 2009
Grand Master
I just looked up the specs on the new model, called "Omega Pro 15A" and saw they also lowered the Fs to 33 Hz, but now list the Usable Frequency Range as 51-1.7k Hz, instead of 35-2k Hz. Is there any practical difference here? Looks like the efficiency is still about the same.

Re: Double checking C5 and R3 values [message #49743 is a reply to message #49742] Wed, 19 July 2006 08:37 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18689
Registered: January 2001
Illuminati (33rd Degree)

Eminence does this every couple of years. They change materials or manufacturing processes and the electro-mechanical parameters shift slightly. I've often wished they would chage part numbers or at least provide a version number to indicate changes but they won't even consider this. But they're pretty good about keeping the specs in a compatible range so the driver acts the same. Fortunately, I've not seen them change the diaphragm during these incremental changes, because different cone flex and breakup modes might make the tonal character of the speaker more different than slight T/S changes.


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