FE206E BIB short version (140 inches) - Page 2 - diyAudio
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Old 1st February 2009, 03:31 AM   #11
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I forgot to mention that these BIB won't be located in corners but instead up againt a wall on each side of the TV.

Eric
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Old 1st February 2009, 05:44 AM   #12
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Well, the standard minimum distance of a port to a parallel surface is its end correction, but backed up against the wall will create a mirror image that doubles the BIB's mouth (Sm) effective area, so find the effective radius (R) of this 2x larger Sm, then the minimum distance (Dm) = ~0.613*R, so 80.5" - Dm = BIB height.

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Old 1st February 2009, 02:34 PM   #13
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Thanks for the answer.

I'm not sure I'm following you since the Sm is calculated using Vb and the height (L) so I wold first need to find the required L to get Sm so it looks like a vicious circle

Lets say I choose Sm of 90.6 square inches based on a height of 86 inches (too high) then 2 x Sm is 181.2 woule be the new surface and is equal to (4 x pi x Rsquare) so
R = square root of ; (181.2/(4 x pi)) = 3.8 inches

Dm = 2.3 inches

Even by finding these number I'm still stuck since the above is based on a L of 86 inches.

How do I solve this...

Thanks for the help.

Eric
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Old 1st February 2009, 04:35 PM   #14
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By trying a few options?

Note that GM pointed out that's a minimum distance, not an automatic requirement. It's really not that hard.

1/ Assuming factory specs. for the 206, select a reasonable tuning frequency -say, 48Hz, for a 140in line or 70in tall box with a CSA of 111in^2.
2/ Double that to account for the virtual doubling of the terminus size caused by the rear wall, = 222in^2.
3/ 222/pi^0.5 gives 8.4in.
4/ 8.4*0.613 = 5.1492in.
5/ 80.5in - 70in = 10.5in
6/ 10.5in - 5.1492in = 5.3508in.

So, room & to spare.
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Old 1st February 2009, 04:54 PM   #15
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Thanks Scottmoose,

It looks like it would be a trial and error exercice to get the maximum height BIB based on ;

1. The height of the ceiling.
2. Try to account for the required minimal spacing from top of BIB to ceiling.
3. Use the back wall to load into the ceiling.

Can I ask you where you got the CSA of 111 inches square.

I wish I could put these in the living room but it could be pricey in laywer's fee

It looks like I will built the 70 inches high BIB

My brother in law hates FR speaker because the lack of bass, can't wait to see his face when he's gonna hear these.

Thanks,
Eric
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Old 1st February 2009, 05:35 PM   #16
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Are you really that bothered about a couple of Hz?

The CSA is just from the standard T/S alignment for that driver / tuning frequency, rounded to the nearest sensible figure.
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Old 1st February 2009, 05:57 PM   #17
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I just find that 48Hz is high, my floorstander are tuned to 37Hz so I was hoping to go even deeper with the BIB.
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Old 1st February 2009, 06:02 PM   #18
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That's 48Hz at the 1/4 wavelength. F10 will be an octave lower (i.e. 24Hz) & useable down to 30.
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Old 1st February 2009, 08:10 PM   #19
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Default Amazing...

Thanks, now we're talking

My sub also has a F10 of 24Hz and F6 of 30Hz so this is quite amazing for a 8 inches vs my 12 inches sub...

Thanks a lot for the answers.

One more thing; Regarding the internal and external speaker wire I was thinking of using small gauge instead of inserting a 3-4 ohm resistor, would 22 or 24 AWG be OK. Distance will be about 3m from the amplifier (solid state Yamaha)

Thanks,
Eric
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Old 1st February 2009, 09:16 PM   #20
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Should be fine, although you won't get much voltage drop over that distance. If you wish to take that approach, go for the 24ga.
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