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Bi_amped system questions
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Old 17th November 2005, 09:21 PM   #11
BobEllis is offline BobEllis  United States
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Almost - you just need to apply baffle step compensation. If you can cross over at the appropriate frequency, it could be as simple as turning up the gain on the sub. If the sup doesn't go that high, a simple op amp based circuit can handle it.
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Old 17th November 2005, 09:30 PM   #12
Cal Weldon is offline Cal Weldon  Canada
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Bi_amped system questions
The FR125 is a good choice. Very versatile driver. You can easily go down to 100Hz with them, depending on your power requirements. The 24dB slope really helps.

Also, 4th order provides quite the separation so it'll be easier to match your woofer.
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Old 18th November 2005, 12:19 AM   #13
jimbo1968 is offline jimbo1968  United Kingdom
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I fancy making spherical enclosures, but I couldn't find any conclusions in the discussions about internal design/resonances etc.

Modelling the fr125s in winISDpro shows that it does easily go down to 120Hz in a sealed enclosure. What difference does volume make for sealed enclosures, is it just bass extension and therefore no problem as I'm cutting the low end off anyway? A 10" sphere size to match my woofers will give 3or4 litres.

PS. how do you model 1sub +2woofers +2fr125s ? Do you double the power & volume & no. of drivers for the woofers and fr125s?
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Old 23rd November 2005, 12:20 PM   #14
jimbo1968 is offline jimbo1968  United Kingdom
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Default baffle step

How do I calculate the reinforcement from the rear wall? ie how much less than 6db baffle step compensation I will need.

My FR125S will be in a pseudo spherical cabinet and will be about 500mm from the the rear wall.

Or should I just build a plain crossover and measure the results before adding BSC?
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Old 24th November 2005, 12:13 PM   #15
jimbo1968 is offline jimbo1968  United Kingdom
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Default my active crossover design - help needed

Summary: My bi-amp system will be FR125S in 6litre sealed enclosure, sitting above 10" driver in 40litre sealed box. Each driver will be driven by a chip amp. The active crossover will be in the amplifier case.

I will build a board per amp, and think I need the following:

Mid/High:
Input Buffer
Adjustable Gain
BSC
HP - 4th order at ~160Hz

Low
Input Buffer
Adjustable Gain(?)
Linkwitz Transform
LP - 4th order at ~160Hz
HP - ?order @ ?10Hz

I've not looked at BSC circuits yet, but saw mentioned somewhere that BSC can be incorporated into the input buffer (I assume that means without additional op-amps). Can I do buffer, gain and BSC all with 1 opamp?

It strikes me that the BSC and LT are doing the same thing, so are the circuits similar? can I use one circuit for both jobs?

For ease of layout on stripboard, should I be looking at single or dual op-amps?

It may be that I can answer these myself with further investigation, but any help to speed me down the right direction is appreciated.
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Old 24th November 2005, 09:13 PM   #16
BobEllis is offline BobEllis  United States
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Linkwitz has examples of both on his site - a great reference for active filters. BSC is at 6 db/octave, LT at 12. Similar but different circuits. Yes, you can use a BSC stage as your input buffer, like Linkwitz does.
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