jordan jx125 + jxr6 from vented to closed

[kubi]

Hi there!

I'm going to modify my vented loudspeakers (Jordan JX125 + JXR6) to closed ones to save space in my living-room. Currently it's about 70L per box just for the woofer, which I want to down size as much as possible.

So, I'm talking about the JX125 woofer only.
My idea was to have a closed, high pass filtered design. Qtb = 0.93 would do the job instead of the way lower Qtb at the moment. The distorted frequency response due to the too small box would be corrected with the help of a cap in series with the JX125 driver - the tweeter will remain in its own housing.

According to the formula I know for closed and HP filtered boxes,
V=Vas/((Qtb/Qts)^2-1)
f3=0,7fs/Qts
C=265000*Qts/Re/fs

with

fs=30Hz
Qt=0,45
Vas=53,66l
Re=6Ohm

(from http://www.ejjordan.co.uk/diy/bass)

I end up with

V=53.66L/((0.93/0.45)^2-1)=16,4L
F3=0,7*30Hz/0,45=46,7Hz
C=265000*0,45/6Ohm/30Hz=662,5µF

Good idea or completely crazy brainfart? 17L sounds good to me.
Please let me know what you more experienced guys think before I take apart my current loudspeakers.

BTW: Currently the system is bi-amped (4 x gainclones) with active crossovers (Linkwitz-Riley filters @500Hz, 12dB/Okt). I want to keep that amp for the new boxes. It's cheap (gainclones ), but it's still very good and allows me deep adjustment of all the parameters to make the two drivers match together. That's easier and cheaper than building a decent passive XO, since I'm more an electrician than loudspeaker builder.

Thanks in advance!

[bjorno]

F3=0,7*30Hz/0,45=46,7Hz

Hi,

I got f3= 50,5 Hz and fc=62 Hz for a Qtc of 0.93 at V=16.4L.

I believe that Vb= 36L; Qtc=0.71 and f3=Fc=47 Hz is a better choice from the transient responce reasons.


B