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Old 22nd June 2005, 09:22 AM   #1
zek is offline zek  Serbia
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Question New project : FR bipole & Sub

This is my new project with two Visaton FRS 8 4 Ohm in closed enclosure as bipole, and Visaton W 170S 8 Ohm in BR or MLTL enclosure as sub.
Can I put two FRS 8 4 Ohm in series to get 8 Ohms total impedance for bipole configuration.
Xover will be around 150-200 Hz/ 6dB

Eny suggestions
Thanks
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Old 22nd June 2005, 09:25 AM   #2
zek is offline zek  Serbia
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Old 23rd June 2005, 06:19 AM   #3
Salas is online now Salas  Greece
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I have done this with an 8 inch woofer. It will not sound best as bipole. I have tested and compared. I recommend you use the dipole connection (i.e. back FRS in inverse polarity). This lends natural cancelation and falling response towards the bass. Better is to use FRS8s in parallel ending up with 4 Ohm. I have found that a 20uF cap in series with the head units and a coil suitable coil feeding the woofer is ok.
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Old 23rd June 2005, 06:39 AM   #4
zek is offline zek  Serbia
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Thank you salas.
What 8" woofer you recommend ?
What about FRS 8 on open baffle ?
With 20uF in series with the FR unit I get abot 1000Hz as crossover point - isn't it too high.
Something about 100-130uF is for 150-200 Hz crossover point.
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Old 23rd June 2005, 09:05 AM   #5
Salas is online now Salas  Greece
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I recommend VISATON TIW 200 XS 8 OHM or AL 200 8 OHM in closed box. You need fast group delay to match the FRS. Closed box sounded best to me.
I have tried low cross and I much prefered the 20uF with the paralleled & dipoled 8 OHM FRS8s (4 Ohm total). This is due to the fact that you end up with just an 85dB sens and the Visatons do make nasty squeaks when losing xmax. They sound far more open with the 20uF and you dont need a heavy & expensive passive cross for the woofer. In case you want to try low, just wire them in dipole and they will drop to about 250Hz due to front-back antiphase destruction.
Please use a box, 3 litres net closed for the upper section. They are not capable for open baffle.
I hope you are not having in mind that Slovenian thing with the manyFRS8s on baffle and the woofer, its completely plagued with comb filtering and overexcursion. Hope I helped. Hvala!
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Old 23rd June 2005, 09:26 AM   #6
zek is offline zek  Serbia
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I don't know what "Slovenian thing" is about.
When I put FRS 8 data into winISD I come with 7.4 litres for 2 of them.
For 250 Hz I get about 5 mH for woofer and 160uF for dipoled 8 OHM FRS8s (4 Ohm total).
Thanks salas - Hvala.
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Old 23rd June 2005, 09:44 AM   #7
Salas is online now Salas  Greece
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Slovenian thing: http://plorec.comcom.si/diy.htm

3 litres, trust me. The Visaton data are off base. See: FR preferences
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Old 23rd June 2005, 12:02 PM   #8
zek is offline zek  Serbia
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Quote:
Originally posted by salas
I recommend VISATON TIW 200 XS 8 OHM or AL 200 8 OHM in closed box....and you dont need a heavy & expensive passive cross for the woofer.
.....and what values for the iductor, and what crossover point (? Hz)

Thanks
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Old 23rd June 2005, 12:31 PM   #9
Salas is online now Salas  Greece
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In mine I have used 3mh on the woofer and 20 uF on the dipoled FRS8s. But I have been measuring precisely and listening a lot.
You cant guess a cross. Given that I had a comparable woofer its a safe starting point. Dont forget that 1st order overlaps severely so 1Khz is only a notion. In my speaker they were playing audibly together from 250Hz.
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Old 23rd June 2005, 01:06 PM   #10
zek is offline zek  Serbia
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Thanks salas for your assistance
Regards
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