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Spring projects... [message #50919] Fri, 30 March 2007 10:28 Go to next message
themilford is currently offline  themilford
Messages: 66
Registered: May 2009
Viscount
Long time no post... sorry I haven't contributed more.

but, maybe you can help me with a few questions.

I think I'm going to move the Delta 12LFs from my Karlsons into some proper Theater 3 Pi boxes. (So Wayne I'll need some plans). I have the crossovers and comp/drivers but I have the H295 horns and wonder if I should get the H290s?

Also, I was thinking of putting the Beta-12LTs into the Karlsons... I'd like to try them with some sort of "super tweeter" like the Fostex FT17H (or the T-90A if I can get some cash together).

My last question is: can anybody here figure out what sorta crossover I'll need for this? If I just want to run the 12LT wide-open and put a cap in front of the tweet what value?

Does anybody have any experience with this set up?

Thanks guys,
David

You've got mail! [message #50921 is a reply to message #50919] Sat, 31 March 2007 10:35 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18708
Registered: January 2001
Illuminati (33rd Degree)

Stick with the H290 on the three π's.

As for your other speaker, generally I've found that a simple first-order works best on something like that. First-order crossovers have such wide overlap that the choice of components isn't all that critical. You have about +/-2x window there. So I'd probably suggest something like a 1.0μF to 4.7μF capacitor with a shunt damping resistor of about 12Ω to 20Ω.


Re: You've got mail! [message #50928 is a reply to message #50921] Sun, 01 April 2007 21:48 Go to previous messageGo to next message
themilford is currently offline  themilford
Messages: 66
Registered: May 2009
Viscount
Thanks Waye.

I'll let you know how it goes... Will I need to pad the tweeter? should I just get a cheap L-pad?

Re: You've got mail! [message #50929 is a reply to message #50928] Mon, 02 April 2007 08:37 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18708
Registered: January 2001
Illuminati (33rd Degree)

If you're asking about the Fostex tweeter and the Beta 12 midwoofer, then yes, I'm sure you'll want to pad the tweeter. I prefer fixed voltage dividers made with discrete resistors, but you could also use a variable L-Pad.


Re: You've got mail! [message #50934 is a reply to message #50929] Tue, 03 April 2007 23:43 Go to previous messageGo to next message
themilford is currently offline  themilford
Messages: 66
Registered: May 2009
Viscount
Wayne,

Actually I'm gonna try running the Beta 12 LT which has the whizzer cone... I think it goes up to about 8 or 9k. Would you recommed a smaller cap value then?

I was figuring I would get a cheap L-pad. Find the best setting. Then measure and replace with resistors.

thanks again!




Re: You've got mail! [message #50937 is a reply to message #50934] Wed, 04 April 2007 08:33 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18708
Registered: January 2001
Illuminati (33rd Degree)

A 1.0μF capacitor should work just fine. If you want a little less tweeter, you might try a 0.68μF or 0.47μF cap.


Re: Discrete resistors vs. variable L-Pad [message #50939 is a reply to message #50929] Fri, 06 April 2007 04:58 Go to previous messageGo to next message
dB is currently offline  dB
Messages: 234
Registered: May 2009
Master
Hi,
Wayne, is the variable L-Pad frequency dependent, showing a different L/R "behaviour" with frequency, or just a "neutral" component more like (variable impedance) non inductive discrete resistors?
Or is it necessary to measure L-pad inductance "L" also?
Cheers.

note: I am using L-Pad's in addiction to discrete resistors to achieve a plus/minus output control that you mention earlier in your definitions of a perfect L-Pad xover design.

Re: Discrete resistors vs. variable L-Pad [message #50941 is a reply to message #50939] Fri, 06 April 2007 11:34 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18708
Registered: January 2001
Illuminati (33rd Degree)

Some L-Pads are made to hold their impedance constant, but others are really just potentiometers. The latter will cause crossover characteristics to shift as the slider is moved.


Re: Discrete resistors vs. variable L-Pad - Thanks! [message #50943 is a reply to message #50941] Fri, 06 April 2007 13:23 Go to previous message
dB is currently offline  dB
Messages: 234
Registered: May 2009
Master
Thanks Wayne.
I was afraid that they were inductive, like in resistors. I tried to measure one but is kind of difficult.

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