Everyone ... Thank you all for the more detailed answers to my questions. I appreciate them. I recognize that my lack of experience in this area must be frustrating to those of you to whom this stuff is old hat. Thanks for taking your own time to educate a newb.
Also, again, I'm a guitar player trying to repair a cheap bass cabinet with blown drivers, on the cheap, and fairly easily. To me, replacing the drivers seems like the cheapest and easiest way to go, since I have to replace the drivers anyway. I just figured that, since I DO have to replace them, I might as well try and upgrade the cabinet a little while I'm at it. It is the info that I originally picked up here on this forum, that led me to consider trying to cover the high-mid hole that the BP102 leaves between itself and the tweeter. That's what I'm trying to do. Upgrade the cabinet, and cover the mid-hole.
I'm not a carpenter, but I could probably manage to replace, move, or extend the divider inside the enclosure to make a sub-enclosure. I don't think I'm capable (or willing, if you prefer) of moving or resizing the port or tweeter, or of somehow 'shrinking' one of the 10" cutouts down to 6" for a mid driver. I could probably change the length of the 'port tube', if that matters.
I've worked on guitar amps (as an amateur) for many years, so I could also probably manage to solder a crossover or high-pass between the drivers, if necessary.
Ok, onward to your latest suggestions ...
1) "The reason for putting two different speakers in there own compartment and crossing them over is to protect the high handling speakers from overexcursion. If they are both in the same compartment, the one that handles the highs can't take the abuse from the lows that other can. Guess which speaker will blow?"
Having done some more reading, it appears that in bass guitar speakers, the RMS-wattage rating is generally a piece of thermal protection info, which leaves your over-excursion problem as a valid concern. So maybe I could put a high pass on the B102, at about 45 or 50 hertz, to protect it from over-excursion?
2) "There is a lot of pressure in that bass cab in the low end. The only place for that pressure to release is through the speakers or ports. That pressure will follow the path of least resistance and one of the two will not handle that pressure. If only one speaker can handle that pressure, I'll leave it to you to guess which one won't."
Wouldn't the path of least resistance be the port?
3) "To answer all of your posts, an acoustical engineer doesn't have to actually build the system to know in advance how it will work. By the same token a civil engineer would advise you not to build the Golden Gate Bridge out of Popsicle Sticks, while an aeronautical engineer would advise you not to build a hang glider with a cast-iron frame. You've been given very good advise by people who have a fair amount of practical acoustical engineering experience; I do it for a living. Ignoring that advise is probably not the wisest course."
I understand the concepts of abstraction, modeling, etc. That's why I'm here asking questions. Nor am I ignoring anyone's advice. That's why I'm still asking questions rather than purchasing drivers. I am, however, replying with further questions to advice offered, in order to make sure that I understand both, A) WHAT is being asserted, and, B) IF the assertion is accurate. (Or, in other words, to determine for myself if the various assertions stand up to critical analysis.)
3) "if you don't know what "displacement limitation" is, then you certainly aren't qualified to make an informed decision on this topic or any of the others you listed here."
Unfortunately, there is no one else to make the decision. No matter whose advice I end up taking, in the end, since it's my cabinet, it will finally have been my decision. I don't WANT to make a bad decision, so I'm attempting to GET informed / qualified!
4) "but hey, you're going to do it anyway regardless of the good advice given, so all i can say is i hope you enjoyed the money you're about to waste."
I don't know that I am going to do it. At the moment, I'm leaning towards foregoing a separate driver for mid-coverage, installing two BP102s, and trying to make up the difference with EQ. I looked at a Frequency Response / SPL chart for the BP102, and it appears to really fall off after about 1750 Hz. But the tweeter takes over at 3500, so there's a gap of about 1750 hertz that's not well-covered by the drivers I have in mind (if I leave out the B102 and just go with two BP102s). The BP102 makes weak response in that range from 1750 to 3500, but not NO response, so I'm thinking maybe I can boost it enough with my head. I have a Yorkville head with pretty extensive and precise EQ on it, so maybe that would work.
Tom
