Full-range plus Woofer?


2005-12-31 10:09 am
My project limits me to smaller (3" or 4") full range drivers. Even with bass reflex or backloaded horn designs, I'm not getting the bass I want.

I could add a powered sub but I'm trying to avoid a second amplifier.

Might I simply drive a (sub?)woofer off the signal going to the full range?

Yeah, that would be a two-way speaker. But I wondered if anyone had thoughts on doing this. Just wire the woofer in series with the full-range with a coil in line? I hate crossover's but it seems I would need some sort of filter on the woofer at least. No components on the full range though?

I'm sort of tossing this out there hoping someone knowledgeable can point to a project that did something similar.
whats the problem with adding an active sub off the signal source?

Exactly - but don't overlook the substantial benefits to overall dynamics, SPL and reduction in midrange distortion that can be accomplished with HP filter around the LF turnover point to woofer(s) when using this small a FR driver.

This is of course brain-dead simple with HT receivers or computer based sources & software like minidsp etc, but does require extra components for processing at line level, and the ability to separate "pre" and "power" amp stages for a 2 channel only music system.
Nothing really —*I'm trying to avoid a second amplifier though.

Among other things, the potential difference in sensitivity between drivers can make the filtering rather more complicated than a simple coil for the woofer - indeed this is one of the factors that make passive multiway designs challenging .

I'll forgo describing XOs as inherently "evil" ;), but it's nice to get them outside of the most critical section of the "telephone band".

There are so many advantages to separately powered woofer(s) - ether internal "plate amps" or external - to be avoided on principle alone. What we're describing here is functionally an "active" system.
A big inductor can cost more than a plate amp :p

Add the equally large cap and you can readily put together a decent stereo Class D amp.