FE168EZ Open Baffle

[audioferret]

How do I calculate the low frequency dropp-off point for the FE168EZ Sigma on an open baffle? SL's Website explains the calculation in terms of finding the Fequal point, but I can't seem to make sense of his math... in Fequal .17v/D, what exactly does v and D stand for and what units should I use?

Also, in line with the Orion design, would the FE168Ez make a suitable pairup with the FT17 Supertweeter in an open baffle? I am considering the pros and cons of using different drivers in the setup. I can design and make my own electronic crossover and amplifier. I would prefer to use crossover points of 250 and 8-10K. I can't seem to find many successful examples of the 168 in an open baffle.

Last, would two FE 108s work with the FT17 in a MTM Open Baffle as an alternative?

[Drew Eckhardt]

Originally posted by audioferret
How do I calculate the low frequency dropp-off point for the FE168EZ Sigma on an open baffle? SL's Website explains the calculation in terms of finding the Fequal point, but I can't seem to make sense of his math... in Fequal .17v/D, what exactly does v and D stand for and what units should I use?

v is the speed of sound at 1130 feet/second
D is the path difference between front and back waves

D is approximately half the width of a flat baffle but should be determined empirically

[audioferret]

I get 42.68 Hz when I multiply 1130 by .17 and then divide by 4.5 inches for half of the width of a 9" baffle.

Is that a correct estimation? I was estimating around 250 Hz based on the table in the "Single-Driver-Website." Does the actual driver used matter or is the primary factor the width of the baffle? If I use .75 inch plywood, do I need to take plywood material or baffle thickness into account?

Thank you for your assistance, I really like the Fostex driver and the pair I mentioned above would have a higher SAF than the current pair in the Orion. The wife is not happy about the cost either, and I need to try to minimize that...

[adolphe]

check your units. I think you're mixing feet and inches. That's why everyone should work in SI units

[audioferret]

Yes, 1130 Feet/second is quite different from 13560 inches per second.

That leaves me with an FEqual coefficient of 2305.2/x where x equals half of the baffle width. Why not just keep the math simple and leave it at 2305.2/x?

I am such an idiot.

[Rudolf]

Originally posted by audioferret
I can't seem to find many successful examples of the 168 in an open baffle.

I wonder if you could find any! With its low Qts and small Xmax the 168E Sigma is a typical horn driver - quite the opposite of what you want for OB.

If you want to get a realistic picture of its behaviour in an OB, try xlbaffle.xls http://baseportal.de/cgi-bin/basepor...&cmd=all&Id=15