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Crossover help [message #42152] Sun, 10 August 2003 04:40 Go to next message
frankmalz is currently offline  frankmalz
Messages: 11
Registered: May 2009
Chancellor
hello forum,

i wish to build a coax system with the 12cx eminence .The tweeter is the cp380m from beyma.I measured up the frequency response of the system at 1m in a 125 liter enclosure.

My questions are :
where would you start to design the crossover?
which crossover point?
what to do with the rise at 10khz?

Thank you very much for your help!

frank

Here is the graph! (nt) [message #42153 is a reply to message #42152] Sun, 10 August 2003 05:15 Go to previous messageGo to next message
frankmalz is currently offline  frankmalz
Messages: 11
Registered: May 2009
Chancellor
graph
Re: Crossover help [message #42157 is a reply to message #42152] Sun, 10 August 2003 08:12 Go to previous messageGo to next message
Jeff Robinson is currently offline  Jeff Robinson
Messages: 26
Registered: May 2009
Location: KC, MO
Chancellor
I'd be more concerned with the dip at 6.5 kHz. Have you tried moving the measurement mic position to see if it's an artifact?

I'd look at 1.6 kHz for a starting point on the crossover, if you're doing a passive crossover then the 800 Hz resonance of the Beyma will need an impedance notch filter. I'd look at Wayne's crossover document for help with that.

http://www.pispeakers.com/Speaker_Crossover.doc
Jeff Robinson

More measurement files! [message #42159 is a reply to message #42157] Sun, 10 August 2003 10:55 Go to previous messageGo to next message
frankmalz is currently offline  frankmalz
Messages: 11
Registered: May 2009
Chancellor
Hi,
thanks for your helpful replies!!

I loaded the complete measurement files at my yahoo briefcase.
Open "coax".

frank

1.6kHz with Zobel and L-Pad [message #42167 is a reply to message #42159] Mon, 11 August 2003 00:55 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18787
Registered: January 2001
Illuminati (33rd Degree)

I'd go with a ~1.6kHz crossover. For a coaxial arrangement, I might be tempted to use a symmetric crossover. As for the top-octave, it really looks pretty good and so I wouldn't add more energy there. Just use an attenuator to match the Beyma tweeter level with the Eminence midwoofer.

I think you will probably want a Zobel on the Eminence midwoofer, but for the tweeter horn, a series/parallel L-Pad arrangement that attenuates 10dB would be great for double duty - attenuator and damper. Give that a go and check your measurements to see where you're at. If the L-pad doesn't damp the circuit enough, try some different values and maybe even go with Jeff's suggestion of a tank circuit (notch filter) which will act as a resonating damper.

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