Upgrading tweeters in Monitor Audio 5i speakers

Get a book on speaker design to get a better idea. You'll certianly have to know the frequency response of the tweeter and fundamental/low frequency resonances which would dictate whether or not the driver is suitable replacement (or how much xover mod you want to do). The closer you xover to the low freq resonance of the tweet the steeper the crossover slope will need to be. I doubt the tweets own subenclosure will significantly effect enclosure volume so you can ignore it messing up the performance of the other drivers. However, you'll have to change crossover parts to ones of different values if the impedence of the individual driver (tweeter) varies (which it most likely will)--you'll be changing parts in the xover even if you are maintaining the same type of crossover (assuming you driver is of a proper operation range (some tweets are good down to 2000hz other 3000hz to give examples)). So to do that you need to find the basic Theil/Small parameters of the driver in addition to the crossover type employed. Georgia Audio labs has an online crossover calculator once you have that info. Also, pay attention to the sensitivity/efficiency of the driver. You may have to pad it down to get a smooth frequency response (i.e. the tweeter is 2 db more efficient than you midwoofers (so you may want to get the T/S parameters of those drivers too). If you can't get them you can measure them yourself (david b weems books give some quick methods i believe). Regardless of how well you integrate the tweeter some things will certianly change-off axis frequency response may be different, e.g. a highquality 3/4 inch dome will usually have a better frequency response than a comparable quality 1" dome. Also, you may have to make some basic cabinet modifications to get the new driver to fit. Which, make sure there is enough space to accommadate the new driver, sometimes those mounting plates can take up alot of space, sometimes so much so that acheiving maximum allowable distance between to drivers given x crossover frequency is impossible, and there will be some interference. An example of the latter, at 3000hz 4.5 inches is the max allowable distance (13500/3000=4.5) and if its a 6.5" driver and a 1" tweeter thats already 4.25" driver midpoint to driver midpoints, so surrounding mounting assemblies will suck up that last quarter inch and then some (its not one of the worst sins in speaker design but...) The dynaudio driver may be a little over kill for the monitor audio and you could probably buy a kit speaker for the price of those tweeters that would be an upgrade to the monitor audios. Monitor audio may be able to supply the specs of the individual drivers and the crossove employed. The local library may have some useful books so no money on the info.