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a_tewinkel 6th October 2012 07:38 AM

I would choose the poly driver. It will probably have a slightly lower F3 and has a smoother response in the midrange (around 1 kHz).

sreten 6th October 2012 01:23 PM


Originally Posted by balerit (
Your two speakers must have the same sensitivity so that
means you should use the SB17NRXC35-8. The impedance
at the crossover point will determine your crossover values.


The Book Worm - DIY Audio Ebooks and Manuals - Speakers, Moscode Amplifiers, Electronics, Map Reading, Free Capacitor Intro.


Anyone who makes statements like the above shouldn't be
writing books about speaker design. The above is two
statements of standard beginners errors of fact.

Because of BSC the drivers sensitivities do not need to
be the same. More factors than the speakers impedance
need to be taken into account to arrive at the correct
crossover values for the acoustic target functions.

rgds, sreten.

system7 6th October 2012 02:43 PM

I have found a another kit for the papyrus coned SB driver. This time the Meniscus Mandolin speaker designed by Jeff Bagby. Gotta be good, and far better than any homebrew design. Why reinvent the wheel? :D

The 15L Mandolin has a lower 2kHz crossover than the SB Eka kit, which should see off any cone-breakup horrors:
Mandolin Speaker Kit / Pr

Jeff has also designed a 7.5L version using a smaller SB papyrus driver called the Piccolo:

RockLeeEV 6th October 2012 03:36 PM

soft poly cones are fools gold. They appear to have very smooth frequency response and are perfect for low parts count crossovers. But all that means I'd that you're into breakup very early and audibly over a wide bandwidth. Stiff driver materials may need bit more crossover work, and don't really like mating to cheap tweeters, but also won't be mid fi.

Stiffness vs Damping... would be great to have both but given the choice I will lean towards the former. Have the driver be pistonic over as much of its passband as I can, and hopefully push its narrow band breakup well out of that passband. Sure would love to mess with Infinity's CMMD cones on some scan speak Illuminator motors though. Well I guess.that's what Accutons are!! :eek:

5th element 6th October 2012 05:24 PM


Originally Posted by upking (
The crossover will be a 2nd order Linkwitz-Riley at 2,5khz

I assume by this statement you mean that the final acoustic response of the woofer will look like a 2nd order LWR on axis at 2.5kHz. Simply slapping in a 2nd order LWR electrical network, calculated to text book values will not result in the former, which is what you are wanting to achieve.


Originally Posted by upking (
But the truth is, I don't know the difference between exactly the same speaker but with different cone materials.

All drivers go through break up at some point and its this that really affects how a driver sounds. The best designs crossover before any break-up occurs so that its influence isn't part of the final design. Both the SB drivers go through their main break-up relatively high in frequency such that you can cross over before it becomes an issue.

Wide band drivers typically rely solely on controlled break-up to extend their useful bandwidth. In designs like these you are forced to listen to break-up because you don't have a choice if you want to use a single driver system, or a system that crosses high to the tweeter.


Originally Posted by upking (
Another question, should I consider the on axis curve while calculating the crossover value or the others?

It depends on what axis you're intending on listening to them. Generally speaking though people design to the axis that the loudspeakers will be listened at. This is usually close to being on axis and if designed correctly the off axis curves will also be suitably flat.


Originally Posted by RockLeeEV (
soft poly cones are fools gold.

At first glances it would appear that SB have chosen a poly mix that isn't super soft.


Originally Posted by RockLeeEV (
Well I guess.that's what Accutons are!! :eek:

I guess I'd like to mess with Accuton cones on Scanspeak motors :P Most of Accutons motors are a step down from what Scan can supply. The 6.5" metal coned illuminators look fantastic on paper, save for the ridiculous cost. It'd be nice if scan made a 5" metal illuminator, more focused at midrange performance, but I can't see that happening, I don't think Scan have ever done metal coned midrange driver?

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