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Old 28th June 2004, 07:36 AM   #1
diyAudio Member
Join Date: Apr 2004
Location: middle of wasteland
Default Please advise

Hello forum,
I am new to speakerbuilding and would like some advice. I want to build a pair of subwoofers using some fostex L669 woofers.
These are 18" and incredibly heavy, There are two of them in my dads stuff. He says i can have them if i can use them. He doesn't know how long he has had them "a dogs age" mum said.
Thank you ,
Cookin wiv gas
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Old 28th June 2004, 08:42 AM   #2
Hi John!

Be prepared to build some big enclosures! I don't know these woofers in special, but in general big membranes force big enclosure volumes...

First it would be good (necessary) for you to know the Thiele-Small-parameters of these speakers. You got any datasheet? Or even better: Any possibility to measure the actual parameters?

Then you would be able to determine the right kind of housing for these woofers: Sealed, vented, ...

There are some nice free softwares around the internet, which will assist you in this task ("Audua Speakerworkshop" and "Liberty Praxis"-demo for measuring, "Linearteam WinISD" for simulating the response in different cabinets, and lots more).

Hope that helps a little bit to get you started

Best regards,
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Old 28th June 2004, 10:30 AM   #3
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Join Date: Nov 2002
Location: NZ
measuring t/s specs isnt so hard

id reccomend it,rather than just trying random boxes which may or may not have good result
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Old 28th June 2004, 02:58 PM   #4
diyAudio Member
Join Date: Apr 2004
Location: middle of wasteland
Default fostex L669

Thanks for your help guys,
The T/S paramaters are not to be found, at least not by me.
I have done a net search and turned up nothing, fostex don't list it or have specs
These appear to be old, they are quite scuffed and one has a small repair to the cone. If I play them in free air they go quite low, they sound great . They are rated at 8 ohms and 400 watts according to the lable on them.
Cookin wiv gas
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Old 28th June 2004, 10:38 PM   #5
If you don't want to measure them:
Put each of them in a sealed box of around 100-150 l. You can tune them (at least a little bit) by the amound of damping-stuff you put into the cabinet.
Without knowing the T/S-parameters it is impossible to tell what's the optimal housing for these speakers, but this should work fine. It is much more demanding to find a good vented arrangement by trial and error!

Have fun!
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