I can see the bass rings for longer, but the initial amplitude is the same for all of them. I will prefer the sound to be damped and ring less but keep the initial amplitude untouched. For me I think the half bag acoutica stuff is the best, damps the whole spectrum well and probably the cheapest option too.
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SB Acoustics SB13PFCR25-4 COAX 5" Paper Cone Coaxial
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- #22
Thanks for explaining your preference.
I do want to do a round 2 comparison after I make some steel plates. If I can kill the resonance with a steel plate, that will be the cheapest solution.
I had hifijim from diyaudio over today and he said to fluff out the a-stuff before using it. I will be sure to do that next time. I just grabbed a lump out of the bag and shoved it right into the speaker for the measurements in my previous post.
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- #23
Some distortion measurements at 0.6m
Here is a comparison of the decay for the ETON/BlieSMa 3way VS the SB A coax. Sure one costs many times more than the other but this is just to see what can be seen. The levels are not matched but that should not change how they drop that much. The big difference seems to be what happens around 1khz.
I want to repeat the last test again with my JBLs and have everything level matched.
Here is a comparison of the decay for the ETON/BlieSMa 3way VS the SB A coax. Sure one costs many times more than the other but this is just to see what can be seen. The levels are not matched but that should not change how they drop that much. The big difference seems to be what happens around 1khz.
I want to repeat the last test again with my JBLs and have everything level matched.
What are the SPL for the distortion measurements? The odd order distortion is quite high. What do you think is cause for longer decay at 1 kHz? THe frequency response is higher at that point and odd order distortion is at the same spot. It looks like a resonance, and interestingly the distortion follows. There are another three peaks with the same thing, higher frequency response and higher odd order distortion. I wonder what is the cause that will make resonance and odd order distortion happen at the same time. Very interesting to see those measurements and analyse those stuff.
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- #25
I marked them on the left side of the graphs. About 89db and 80db. I still think the coax is a steal if one only listens below 80db.
I think it is baked into the woofer. Hificompass has a plastic cone cousin to the coax measured:
SB Acoustics SB15MFC30-4 | HiFiCompass
The THD measurements at distance of 20 mm and voltage level of 4 Volt were carried out with High Pass Filter "on" (2nd order Buttreworth type, 20 Hz cutoff, HPF2-20). The THD measurements at distance of 20 mm and voltage level of 5.6 Volt were carried out with High Pass Filter "on" (4th order...
It looks similar to me? The ETON also matches the hificompass waterfall.
So now the debate is what to do about the 1.2khz on the coax: Ignore, move the XO, or something else?
Just ten more dB made that much difference? SB does make low distortion drivers, but only at low volumes..... 1.2 kHz is too low for tweeter to play, so I don't think move crossover will work. From hificompass' measurement the 1 kHz longer decay shifts towards 1.2 kHz, don't know if they originate from the same thing. 1 kHz looks like resonance , 1.2 kHz looks like surround issue. It is such a weird driver to work with. If you want I think you can try edge coating the driver to stiffen up the surround to cone area. It is documented some where on the internet, one example is Trovel G....'s website. I don't know the consequence though, I guess the Kms vs excursion curve will be more ugly, but given the fs of the driver is low I would expect three way crossover at a few hundred Hz would experience no bad effect.
