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Join Date: Nov 2006
Location: Bushnell's Basin, NY
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Beast +1... What aspects of the speaker are you trying to improve?
Let's start with tonal balance. If the replacement drivers are more or less sensitive than the original drivers, the result will be bass- or treble-heavy respectively. Granted, a resistor fixes the latter, but that's an XO change. This is a big issue for my ears, second only to...
If the replacement driver Qtc is differrent, you'd expect low bass to either be boomy or lacking. That could be fixed by a port change, made difficult by use of an oval port, or by blocking off the port.
If the replacment driver frequency response is different, the XO filters will not correct the response back to flat, so there will be more linear distortion. If the replacement driver impedence response is different, crossover frequency can shift resulting in more linear distortion.
What will not happen is no sound. The change will result in a functional speaker, but it may not be any better and could be much worse. Which brings be back to your goal; you want to extend it's capabilities, but you don't say what aspect?
If we assume bass, you'd be better off with a lower Qtc replacement than this. As Curt says on his Aviatrix page, "the high driver Qts of the ND140 precludes use in a traditional vented design." Sealed is an option, but not one that extends bass capabilities.
Does this make sense?