Hi
@Oyster150
Thanks for the pic showing the individual responses ( woofer + horn/driver combo ). It's most enlightening!
Here's your pic again ( reformatted & enlarged for analysis > though the horizontal db lines are still hard to see > they are 5db per line ).
A few things come to mind;
i) Yes, the 1-3K (+5db ) bulge is baked into your horn/driver combo. It shouldn't look like that.
- You'll need to investigate why that's happening.
- It's possible your le85's have compromised HF response ( perhaps, due to crumbling foam touching/damping the diaphragm and reducing HF response above 3K ).
- I would run another sweep of that driver/horn combo from 1/2 meter ( on axis ) without the lense and without the crossover in place. A raw sweep of that combo should look a lot smoother than what you're showing. Set your sweep to start at 300hz at a moderate ( listenable level > such as 80db > assuming you have a USB mic that also tells you db levels ). Post the results here.
ii) Also, I see that you do have too much overlap between the individual woofer and horn sections. I somewhat expected that the woofer would be reaching up higher than intended, based on info about your stated preferences. I'll suggest going back to the lowpass curve that actually matches the Nelson Pass lowpass. I'll post that schematic later ( after you've solved//discovered the reason for the rough response of the horn-driver combo ).
iii) Your horn-driver combo ( with it's Hi-Pass in place ) goes down lower ( to @ 550hz for a minus 3db point ) compared to what Nelson Pass intended with his reworked crossover ( at @ 700hz for a minus 3db point ) . After a couple of days looking for reasons, I tentatively settled on the most unlikely factor for the error.
It now seems to me that N.P. redesigned his L300 crossover for either a re-diaphragmed le85 ( sporting either a D16R2421 or maybe even a D16R2425 diaphragm ) or possibly a complete replacement driver ( and he's not aware of this substitution ) .
- FYI, JBL somewhat "tightened" up the suspension of their small format drivers when they moved to their patented diamond surround ( vs their older "tangential/swirl" surround ).
- The difference in surround types does /did change the lower end performance of these drivers.
Here's a comparison of the raw response of the two driver/diaphragm types ( on the shorter 2307/H91 horn ).
FYI, the 2312/H92 only adds a smidge more LF extension. ;
When I plug in the blue trace ( which has the diamond surround type diaphragm ) into XSim ( using the LC values for the Nelson Pass Hi-Pass ), I get the projected 700hz crossover point. The red trace ( le85 with older tangential surround diaphragm ) gives a much lower ( somewhat > unworkable ) crossover point.
- Unfortunately, N.P.'s Hi-Pass can't be reformulated to use different LC values to raise up the Xover point ( because of how's he's laid out << & isolated >> the LC parts ).
- You might try substituting in, one of your older 2425J drivers ( if you still have them ) // and then rerun a horn sweep with the Hi-Pass in place to see if the crossover point climbs up from 550hz to @ 700hz ( as was intended ).
Here's Nelson Pass's reworked L300 showing the individual ( smoothed ) responses of the woofer and horn driver sections ;
EarlK
