Possible to upgrade my PMC OB1i?

Hi guys,

I have had my PMC OB1i for a long time now. I have previously done some small things to them. I internally wired out the tri-amp connections so I don't need messy links on the back. I also soldered the internal speaker wire onto the drivers, replacing the horrible crimped connections that were standard.

Could I upgrade the drivers? Maybe replace the woofer with a Purifi unit? Is there anything suitable?

What about the tweeter, I heard ferro fluid can dry out, should I be worried with the age of these speakers? Are crossover components worth changing?

The mechanical and electrical parameters of your woofer are matched to the line in your speaker in order to get the intended frequency response. The purifi drivers will have different electrical and mechanical parameters requiring a different line to get a good frequency response. Without a new matching line (i.e. new appropriately designed speaker cabinet) you will get a wonky frequency response and a downgrade in speaker performance.

Yes old tweeters can have issues with ferro fluid. Some components can go out of spec due to aging. PMC are likely to be a reliable contact for advice.

Generally bringing old speakers back into spec increases the financial value by less than it costs in terms of time and effort. There are exceptions but this is usually the case. Nonetheless it may be worthwhile if the speakers have value to you beyond what they would get on ebay.
PMC OB1s are nice monitors. I've had a pair and loved them. You'd be hard pressed to get anything close to as good for the price of what a complete overhaul of yours will cost. The drivers are for the most part still available or at least should be from various sources. If yours had the scan speak mids and Morel tweeters, they are very much repairable.