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Old 15th February 2007, 11:54 PM   #1
Magura is offline Magura  Denmark
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Default Filter for Abbey's and Fostex FE166

I could bet I have seen those filters somewhere here, but the search didn't show anything.
Anybody remember where it is, or knows what those filters should look like ?

I should maybe note that this is for a regular voltage source amp of about 30W class A single ended

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Magura
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Old 17th February 2007, 03:35 AM   #2
Magura is offline Magura  Denmark
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Hey everybody...wake up!!! I can't imagine that no-one knows what the ballpark figures for such filter should be??

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Old 17th February 2007, 12:15 PM   #3
MJK is offline MJK  United States
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A filter for what purpose? Your request is not clear.
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Old 18th February 2007, 09:49 PM   #4
Magura is offline Magura  Denmark
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You know...the filter you use to trim the response curve....I don't know what it's called. Its purpose is to attenuate the bumps in the curve a bit.

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Old 18th February 2007, 10:32 PM   #5
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I think you're talking about baffle-step compensation. God help us, Terry Cain, may he rest in peace, would have a fit if he knew.

The purpose of BSC is not to take 'bumps' out of the response, but to compensate for baffle-step diffraction (a frequency determined by baffle-width, where the speaker stops projecting sound forward in a 2pi hemispherical pattern, and begins to radiate in a manner approaching 4pi spherical radiation, which causes an apparant drop in SPLs below that frequency because less energy is being directed at the listening position, but is spread around the room). All it does is reduce the sensitivity of the speaker above that frequency so it's all ballanced out. Try a 3.5ohm resistor paralleled with a 1.5mH inductor in the + lead. That's fudged, because I'm not sure just how much of an effect the podular baffle will have. Looks like it needs about a 3db drop according to Nelson Pass's measurements though. I don't want to go too far as you haven't got much grunt to spare with that amp for headroom. Should help a bit though. Martin, any thoughts?

I better now beg the forgiveness of TC's ghost, which will now probably haunt me for the next decade. Terry didn't like circuits, and that's putting it mildly. Still, it's a case of what works best for you. I'd rather have mild electronic compensation and a more even balance than none and one which isn't working for whatever reason (room, system -in this case probably the amp, which without compensation is not ideal for FE166E drivers as it's likely going to over-damp them).
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Old 18th February 2007, 11:08 PM   #6
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Hi,
Fellow member Svante has designed this excellent free software for simulating avtive and passive baffle step compensation methods. http://www.tolvan.com/edge/

Check out the 'Compensation designer' at the bottom right of the page. I have recently used this to build my own line level BSC with excellent results. One (dual) opamp and some resistors and caps is all it takes to get a basic version working. I even powered it with two 9 Volt batteries in the beginning.
It's crazy not to try it when it's this easy.

Unless you mean a notch filter?

Regards,
Martin.
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Old 19th February 2007, 12:24 AM   #7
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Yes, it was a notch filter that occurred to me first when I read the question.
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Old 19th February 2007, 01:01 AM   #8
Magura is offline Magura  Denmark
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Quote:
Originally posted by Scottmoose
I think you're talking about baffle-step compensation. God help us, Terry Cain, may he rest in peace, would have a fit if he knew.
All it does is reduce the sensitivity of the speaker above that frequency so it's all ballanced out. Try a 3.5ohm resistor paralleled with a 1.5mH inductor in the + lead. That's fudged, because I'm not sure just how much of an effect the podular baffle will have. Looks like it needs about a 3db drop according to Nelson Pass's measurements though. I don't want to go too far as you haven't got much grunt to spare with that amp for headroom. Should help a bit though. Martin, any thoughts?

I better now beg the forgiveness of TC's ghost, which will now probably haunt me for the next decade. Terry didn't like circuits, and that's putting it mildly. Still, it's a case of what works best for you. I'd rather have mild electronic compensation and a more even balance than none and one which isn't working for whatever reason (room, system -in this case probably the amp, which without compensation is not ideal for FE166E drivers as it's likely going to over-damp them).

New mantra "I must make sure that I have seen all the replies....I must make sure I have seen all the replies".

Ok, the first half of your post was pretty close to greek to me. What I read here is "mumble, mumble, mumble, try with a 3R5 and a 1.5mH" Bingo

Thanks Scott, this was pretty much what I was looking for...I hope.

Cheers

Magura
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Old 19th February 2007, 01:06 AM   #9
Magura is offline Magura  Denmark
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Quote:
Originally posted by Scottmoose
I better now beg the forgiveness of TC's ghost, which will now probably haunt me for the next decade. Terry didn't like circuits, and that's putting it mildly. Still, it's a case of what works best for you. I'd rather have mild electronic compensation and a more even balance than none and one which isn't working for whatever reason (room, system -in this case probably the amp, which without compensation is not ideal for FE166E drivers as it's likely going to over-damp them).

My amp has a damping factor of about 8, so I would like to believe that it could have been worse??

Cheers

Magura
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Old 19th February 2007, 01:09 AM   #10
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Could someone explain 'over-damped'? My nuforce amps have a damping factor of over 4000 and since they are the only amps I have I've been using them with my FE166Es and other drivers like them. Is this wrong?
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