I have a 3 way build, but here we're only discussing the mid-range. It's a scan speak 18M4631 in a 14 liter sealed enclosure. Near field measurements here show the raw (no crossover), active 2nd order high pass filter at 200Hz, Passive capacitor (1st order) and the impedance of the speaker in box with no crossover. When I add a single capacitor (150uf) I get a massive resonance centered at 92Hz (red measurement), which is pretty much where the box seems to have an impedance spike. Is this normal? It clearly doesn't happen with an active crossover. It seems to get better with a 2nd order passive filter, but I can't get the slope correct with that and it's causing other problems with the linearity of the driver. Would a sizable amount of stuffing in the box help with this? I've seen this before with other speakers and I'm puzzled.
Other notes:
Scarlet interface, Earthworks M30 microphone with calibration file, Buckey Hypex Ncore Class D amplifier.
Blue measurement is raw nearfield
Orange measurement is active crossover nearfield
Red measurement is the questionable one with a single capacitor high pass filter. See the 92Hz centered increase?
Other notes:
Scarlet interface, Earthworks M30 microphone with calibration file, Buckey Hypex Ncore Class D amplifier.
Blue measurement is raw nearfield
Orange measurement is active crossover nearfield
Red measurement is the questionable one with a single capacitor high pass filter. See the 92Hz centered increase?
Attachments
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That is a normal and expected response.
You need to go with a second order electrical to damp the peak.
See the simulation below with ideal driver' FR, BUT the impedance is the actual one traced from Scan' graph for 18M4631.
Only to get the idea...your actual FR (and impedance) measurement should be used of course.
edit: you should probably move this to "multi way speakers" forum.
You need to go with a second order electrical to damp the peak.
See the simulation below with ideal driver' FR, BUT the impedance is the actual one traced from Scan' graph for 18M4631.
Only to get the idea...your actual FR (and impedance) measurement should be used of course.
edit: you should probably move this to "multi way speakers" forum.
Attachments
Thanks. I was able to deal with it by using a second order electrical slope. I was unsure if there was some other problem going on. I appreciate the help.