Critic's Corner

Similar response, though. What's your crossover?

63.155.0.158

Brian H P

A

In Reply to: RE: Thanks, but I am using the "Old School" Fountek NeoCD3.0, not the more modern one Vance measured. posted by John Marks on February 12, 2023 at 12:14:40

Just from the graph, it looks like a 4th order electrical filter down -6dB at 2.5 to 3kHz would get you a nice 3rd order acoustical rolloff.

True ribbons are fragile, and generally need steep filters to avoid damaging overexcursions at the bottom of their passband. Years ago, a NY importer called Zalytron carried some Raven brand true ribbons from France, and recommended 6th order (or steeper!) highpass filters.

Follow Ups:

Down -6.8dB; 3rd order Butterworth @ 3000Hz. - John Marks 07:46:58 02/17/23 (2)
For the latest go-round, I took the woofer off the crossover and connected it directly to the amplifier. Before that, I had the tweeter level up +2dB because of the wide trough in the FR.
So now the woofer is running flat, but I think that +1dB would be better. Please keep in mind that when JA measured Harbeth's P3ESR, it was +1 in the treble.
One thing I like about the idea of letting the woofer run wild is that one can re-dedicate that money to nicer capacitors on the tweeter.
BTW, Fountek ribbons are "reinforced," which I believe is some kind of film lamination process. So, their ribbons are not only more affordable, they are more robust.
Thanks for your interest,
john

Edits: 02/17/23
- RE: Down -6.8dB; 3rd order Butterworth @ 3000Hz. - Doug Schneider 18:40:47 02/22/23 (0)
  I'd analyze distortion on that for sure. Ribbons tend to have high distortion at lower frequencies -- highly audible distortion. Not controlling the top end of the woofer can result in something nasty if it's just left to fend for itself.
  
  Not saying that would happen -- but it certainly could.
  
  Doug
  SoundStage!
- That's a nice sounding graph! - Brian H P 13:49:24 02/22/23 (0)
  The fellows at ASR might even approve!
  
  The baffle step compensation looks well dialed in, and the slight irregularities above crossover should level out at 15 to 30 degrees off axis. The lift above 8kHz should contribute some sparkle and shimmer high up, without excessive brightness.
  
  I've never worked with true ribbon drivers (fragile! expensive! scary!), but have done a couple of builds with the Bohlender Graebner NEO 3 PDR magnetic planar tweets, which actually have a very similar response curve to your Fountek ribbons. Their superiority to a good dome lies mostly in their "open and airy" character in the top octave.

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