I have a pair of Pioneer S-HF21-LR speakers that I got a couple years back on black friday for $10, and since I've had them I've never been terribly impressed and now I have the urge to tinker with them :yes: For those unacquainted with them, they're the lowest end model in Pioneers current retail-market speakers. Single 5 1/4" woofer with a quote "1-inch (2.5cm) High-Efficiency Semi-Dome Tweeter". Whatever, they're too inefficient (80dB/1w/1m) to even be used as rears with the rest of my speakers in my little home theater setup. I'd have to turn the rear level way up and for that duty my small Polk RM6000 satellites do the job better anyway. they're not great as fronts at all compared to my cheap rack stereo Pioneers or my low-budget floorstanding Kenwoods. So, back to the speakers themselves: On the inside, they didn't really have any kind of dampening material at all except for some really thin polyfill batting stuff at the back. I've since added some (marginally more decent) polyfill stuff to all the other sides (it helped the bass not sound so boomy!), and some small rubber feet to the bottom so they don't vibrate off of my other speakers. There are also no factory sealing gaskets on either of the drivers. The cabinet is 3/8" MDF and actually seems pretty well built. The crossover, on the other hand, is obviously pretty cheap. There are two components - a 1u5 50V capacitor wired to the tweeter and a mysterious orange-ish yellow circular device labeled T60 135 wired to the woofer. Pretty much everything I've learned I've gleaned from trolling these fine forums or otherwise googling, but so far there is a gap in my knowledge and I have no idea what this part is (I can post pictures later tonight). Some kind of low pass, I would obviously think, but what is it? My finer speakers don't have anything like this (except my big rack stereo-era Pioneers...). Both drivers are 8 Ohm rated on the back (I know, ideally I would want to measure impedance at the desired crossover frequency), but bear with me for a moment: I used a calculator i found with Google called "The Passive Crossover Design Calculator" written by a guy named Jeff Bagby, and, using the first-order Butterworth calculator...that's what this has to be, right? At the very least a single capacitor on the tweeter is still a first-order configuration, nevermind the woofer. Anyway, if I'm reading the 1u5 capacitor right, that translates in to 1.5uF and therefore the tweeter is crossed at about 13250hz? Could the impedance vary that much to where 1.5uF would do the trick for the tweeter and I'm just nuts? Could two speakers really be designed as sloppily as the Presidians (I have a set of those, too )? Since they're only a two-way and a pretty cheap design at that isn't it more likely that these suffer some kind of hole in the middle? Is it really feasible that the woofer responds up that high, or is my calculation way, way off? Help?!? No harm in tinkering, I guess, but do I stand a chance of making them better by crossing the tweeter lower and doing something else with the woofer? Do I have a lot to learn before I should be pondering such mysteries ? ... don't answer that . Should I leave well enough alone? Maybe I should have posted this in the "Thinking Out Loud" forum!