SEAS W15CY001 + Fountek NeoCD3
Copyright 2006 Troels Gravesen
CROSS-
OVER
CABINET MEASURE-
MENTS
KIT
PARTS

I recently had a pair the new Fountek NeoCD3 ribbon tweeters and have compared them to the JP3 true alu-ribbon tweeters. The new tweeters have a ribbon made from laminated material and will probably be less fragile compared to the JP3 pure alu ribbons.
The easiest way to try out the Neos was to set up a small monitor and the SEAS W15CY001 midbass was an obvious choice. You don't find a much better upper midrange and from a 7.5 litres cabinet you get a surprisingly deep bass. I also tried adding a subwoofer from two push-push Dynaudio 21W54s with a crossover around 60-70 Hz/12 dB and it worked fine. The W15s were run fulrange and this obviously sets a limit to loudness but it all performed well up to relatively high levels.

The front panel is 19 x 30 cm and the drives are at the vertical centerline of the panel, acoustic centres are 75 (tweeter) and 95 mm from the ends. The volume is 7.5 litres and the vent is 45 x (ID) 180 mm to give a vent tuning of 48-50 Hz. (40 mm (ID) vent would make approx. 140 mm length). Find more W15-NeoCD3 cabinet details here. And the usual warning: If you change the front panel dimensions and placement of drivers, the crossover will not work as intended.

I'm not going to write a long story on this monitor. I have used the W15 in two other constructions and it's my favourite among 5" drivers. I had my reservations to the new NeoCD3 ribbon made from laminated alu and plastic foil, but I have a hard time hearing any difference in performance from the two tweeters. These NeoCD3s and JP3s are not interchangeable and you cannot replace one by the other without having to fine-tune the crossover. The bump at 1500 Hz from the NeoCD3 takes special precaution and from experience a 4th order filter is required to get the best of the NeoCD3.


NeoCD3 ribbon tweeter.

OBS!
Please observe that Fountek has changed the position of the plus and minus terminals compared
to the JP3 ribbon. On the JP3 the terminal to the right was the positive.
Check the
TJL2W and How to replace the ribbon in the JP3.


The housing appear to be much like the JP3. However, a flat ribbon is used and this should be a
an alu plastic laminate, supposedly more stable compared to the pure alu ribbon.


Notice the heavy neodymium magnets,


Left: Frequency response of NeoCD3. Not as flat as the JP3, but from practical experience a manageable performance.
Right:Impedance profile of NeoCD3 added a 47 uF capacitor. Never measure ribbons without a capacitor in series with the driver.

Horizontal dispersion:
Red = 0, blue = 10, green= 20, yellow = 30,purple = 40,black = 50.
These graphs display a minor dilemma as the average of all the graphs is quite flat from 1,500 to 20,000 Hz, but the on-axis response has a major peak at 1.5 kHz and a steady rise from 3 kHz up to 17,000 Hz. However as you will see later, targeting a flat response on-axis produces best response +/- 30. So we have to treat the NeoCD3 accordingly due to lack of on-axis linearity.

The crossover:


The crossover is 4th order and the low pass section has two notch filters; one to flatten
the response in the upper midrange and one to get rid of cone break-up.

Crossover Kit


Crossover components and drivers from Jantzen Audio: contact@jantzen-audio.com

Measurements

Left: Horizontal dispersion of final system: W15CY001 + NeoCD3. Red = 0, blue = 10, green= 20, yellow = 30,purple = 40,black = 50. First at more than +/- 30 do we have a decline in response from around 500 Hz. Fortunately this follows the SEAS unit as well.
Right:
Impulse response.

Left: Impedance of system. Not a particularly difficult profile. Right: SPL of final construction. A rather flat voicing, but these drivers can take it and they'll tell you right away what's on your recording.