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FE103 - What Port Size?
FE103 - What Port Size?
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Old 23rd December 2005, 03:13 AM   #1
FlaCharlie is offline FlaCharlie  United States
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Default FE103 - What Port Size?

I've got some cabinets that are 10 1/8" x 13 1/4" x 7 1/2" internal. They originally came with a 5 or 6" full range driver and were sealed. I've got a few versions of the Fostex FE103 . . . one pair of the alnico 10F3, a couple pairs of the RS 1197 versions as well as some similar drivers from vintage KLHs - the 3" that they used fullrange in table radios and as mids in the KLH 5 and even tweeters in some models I think. Anyway, I want to use these cabinets and add a port to the rear. I know these cabinets are a bit larger than the BR cabinets I've seen recommended for these but I want to put something together with them. What size port (diameter? length?) would work well? I'd like to get decent bass, given the limitations. Or would something other than BR work better with these cabinets and drivers?? Thanks . . . Charlie
Old 23rd December 2005, 10:58 AM   #2
sreten is offline sreten  United Kingdom
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I suggest you put 2 drivers in each cabinet with one rolled
off to give you baffle step compensation, obviously roll-off
the driver with the poorest treble.

I presume you'd run an alnico Fe103 full range with a RS1137 rolled off.

The port tuning is in the range 60 to 80Hz.

For a 40mm dia port :
80Hz - 70mm
70Hz - 180mm
60Hz - 350mm

Tuning of one driver in the cabinets is very poor.

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Old 23rd December 2005, 01:51 PM   #3
FlaCharlie is offline FlaCharlie  United States
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Default How Is Rolloff Accomplished?

That's an interesting possibility. Are the graphs you attached for two drivers in the cabinet? I'm a novice at speaker building . . . how is rolloff accomplished? What type of part/circuit and what value(s)? This sounds somewhat like a pair of vintage KLH speakers I picked up at a thrift for a couple of bucks. They have two of the ubiquitous KLH 3" drivers in each cab and are ported but they're very thin (13.25" x 17.5" x 2.75") and were made to be hung on a wall. They supposedly have some kind of "compenstation" network or something - not a simple crossover. They're called the Model 14.
Old 23rd December 2005, 03:51 PM   #4
FlaCharlie is offline FlaCharlie  United States
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Default Or Would a Smaller Cabinet Be Better?

I guess I should have mentioned that the alnico 10F3s are currently in sealed cabs that measure about 5" x 8.75" x 5.75" internally. A bit smaller actually since there is some internal bracing. Would I be better off just leaving them alone? Or maybe adding a port to these cabinets? What about just removing the backs - kind of mini open baffle?? I don't really have the tools/skills to build anything from scratch but I have a few small cabinets lying around. I've got another pair that are 7.5" x 9" x 5.75" which don't have backs at the moment but I could add some and make them sealed, ported or aperiodic. Would any of these options work better? Thanks . . . Charlie
Old 23rd December 2005, 04:00 PM   #5
pinkmouse is offline pinkmouse  Europe
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FE103 - What Port Size?

I have closed this thread, please reply on the other. Thanks

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