Impious

In all honesty I seriously doubt you'd hear a difference between 1.2cuft and 1.5cuft

In all honesty I haven't ran the numbers but generally for good "SQ", meaning better damping and more extended low frequency response, you will want to aim for an enclosure on the larger side. The trade-off with a larger enclosure is less peak output. Also keep in mind there is no such thing as "optimum".....everything is a serious of trade-offs, you just have to select which set of trade-offs best fit your personal preference and goals.

Design the enclosure for desired response, not how much power you are running. http://diysubwoofers.org/misc/portcal.htm That website gives you the formula for recommended minimum port area.

Simplest solution is to sell your amplifier and run one half the size. You don't need 3kw for daily use, especially if you plan on using a single subwoofer.

There is if they were in proper acoustic phase before you inverted them. Exact same amplitude, yes. 180o phase difference as well, which unless you reverse the polarity of one of the drivers will cause a rather severe case of cancellation.

This.

I would love to use a pair of IB315. The downside is my trunk volume (empty) is 14.2^3ft. High qts and large vas of the IB315's make them less than ideal for my use. Am I wrong? With a pair you would get a slight bump in Qtc, some where in the .9 range....which isn't terrible, but depends on your tastes. However you can only expect Qtc to increase from there as you start piling things in the trunk and reducing the volume of the "enclosure". The other issue is the lower F3 which will probably need more EQ work to flatten out than something that starts a shallower slope higher up in the frequency response.

Do as Sean suggested and figure out exactly how much airspace you're able to sacrifice, and then define your goals. You may have a wider and better selection than the SA8v2's. For example, you might be able to go with a single 12" for half the cost and obtain equal or better performance depending on airspace.

The internal "gain" the amplifier applies to the signal is a fixed figure; i.e. the amp works exactly the same amount. The only thing the gain knob on the amp does is allow you to obtain full power from the amp without clipping the signal with varying levels of input voltage. I don't know who you talked to, but if you happen to run into them at competitions again...ignore any further advise they give you as they don't understand the basics. Sure, they "work" in that they do provide a higher voltage input to the amplifier. The problem is the only 2 times that's ever needed in a system is 1) if you have an unavoidable and audible amount of noise introduced into the system during the signal transfer, or 2) if the amplifier is too noisy with a higher gain setting (although this is a result of poor amplifier design and not a problem of low signal voltage). Unless you were trying to fix one of those two issues (which you weren't), then it's unnecessary and a waste of money. The reason you purchased it is exactly the reason they continue to sell; misinformation. It's not. Probably the overcurrent protection circuit is being triggered due to too much input signal for the gain setting, exactly the same thing can occur with any improperly set gain. Honestly.....sell it or see if you can return it. You don't need it, it's not helping you.

I'm presuming you didn't readjust the gain after adding the line driver? If not, turn down the gain. Sounds like you're sending the amp into hard clipping and triggering protection mode. Anytime you do anything that affects the signal level you need to readjust the gain. What was the purpose of adding the line driver? What were you trying to gain? Chances are good the line driver was a completely unnecessary addition to the system that gained you nothing. There are precious few situations in which a line driver is beneficial, in any other situation they are nothing but a waste of money that unnecessarily complicates the system. Sell it and recoup as much of your money back as you can.

IIRC after Adire went defunct Wiggins had to change the name from XBL2, so he just dropped the "2" from the name.

If you were able to set the gains and lower the output level of the amplifier, it would be fine. I wouldn't suggest trying to apply the full 1kw per driver. How much space are you willing to sacrifice for an enclosure? It might be possible to find another driver that fits well within the allotted airspace that would provide overall better performance for an equivalent or lesser price to the SA8v2.

100hz lowpass is perfectly fine. No it's not moving as far but it's also moving significantly faster. Set the SSF somewhere around ~25hz, set the lowpass to where ever you think it sounds best.

my box is 3.2 cubes now and i could NOT see how i would go any bigger without putting the back seats down. if it were even an inch taller or deeper it wouldn't clear the hatch. i barley have any room on the sides either, cursed hump in the interior over the shocks -.- Don't get me wrong people tell me its impressive and loud. but i feel like it could do a little more. my main concern is that even before displacement it falls below recommendations. i understand that people do not always follow the recommendations, but ive heard others say that FI's recommendations are a good guide to go by. and the low end is quite. Below 28ish hertz it has minimum output. Take out your current enclosure and get measurements of the maximum dimensions you have to work with. Unfortunately if you're already close to your maximum dimensions, you aren't going to be able to increase both peak output and low frequency extension. Choose which is most important to you.

FWIW adjusting the gap would have no affect on Fs. Fs is affected by compliance and mass only. As 95Honda said; model the stock driver in the proposed alignment and see what the results are.

That's cool. Don't know details of your design, but the only other XBL tweeter I'm aware of measured extremely well. Not sure what my opinion is worth, but IMO you need to offer the individual drivers for sale

Don't go active. It's not a good plan for you at your current knowledge level. I know it's the new fad, and in the right hands it has definite advantages. But, not everybody has the right hands, and you don't yet. As I said before....work on maximizing your install first, work on increasing your knowledge in the mean time. Once you understand a proper installation and have gained some knowledge, then go active. There is FAR MORE to a quality sounding system than simply going active. A well installed passive setup will far exceed a poorly installed and poorly tuned active setup any day of the week. Now is not the time to jump into an active setup for someone in your position.

Great, you don't need it. Great, then you haven't already wasted money on it. Don't. No problem, it wouldn't help you anyways. What? You set the output of the amplifier to 2V? They were telling you to set the input sensitivity to the 2V setting....not that that info is necessarily "correct" anyways. You would set it based on Ohms Law, if you were using the DMM method....which isn't necessary. But even then if you are using a 0db test tone you will end up unhappy with the results, more than likely. Best to just set it by ear. Neither, set it by ear. If you absolutely feel you must use a DMM to set the gain, then you would set it according to Ohms Law... sqrt(Power*Impedance) = Voltage But, see above. 200, or leave the DMM in the toolbox and set it by ear.

http://zedaudiocorp.com/index.php/products/ra/item/ra.html

For reference, you generally don't want inductors on the same axis that close together. Ideally you would place them in different orientations with a fair amount of separation between them...ie. sit one up on it's side if the other is lying flat, and a few inches apart. This link explains the basics of why: http://www.parts-exp...r.html#inductor Other than that, looks like you're off to a good start.

First I would suggest you stop worrying about "impedance rise". Every speaker and every enclosure is going to have an impedance curve where the impedance fluctuates with frequency. It's going to happen, you can't avoid it, and you don't design your enclosure around it. There are some things the impedance curve can tell you, but for the most part it's not something the average enclosure designer needs to worry about. Design your enclosure based on desired response. As for your question about enclosure efficiency, it doesn't have anything to do with "impedance rise" and everything to do with the mechanical damping provided by the enclosure (the amount of "spring" provided by the air within the enclosure). A larger enclosure is generally less "springy" which in turn decreases mechanical power handling and in a ported enclosure can increase peak SPL. As for "impedance rise" being lower in a larger enclosure....take a look at an impedance graph, you'll notice the larger enclosure actually has a higher impedance at tuning as well as a higher peak impedance (if we keep tuning the same)....and yet, it also has the highest peak output at tuning. How does that work? While the impedance is higher, the driver+enclosure system for a larger enclosure is more efficient and as a result creates more output. If they were plugging one of their multiple ports, as was mentioned it would just "block" the port so it didn't function. If they were plugging the port to simply change the tuning of a vented enclosure with a single port, then it would need to extend the entire length of the port. So you want more peak output? Or more output at lower frequencies?

IMO there can be, but it depends a lot on the vehicle, your goals and the level of your skill in fabrication.

It will probably be a little louder but also sound SIGNIFICANTLY worse. Are you planning on installing the speakers in the stock locations?

Simple solution is to not purchase speaker wire with transparent insulation, then you'll be blissfully ignorant of this problem Like 95 said, sounds like oxidation. Not a huge concern as long as it's not at the connection points, which it's not as I read twice in your post.

Yes, these are XBL Cool beans I've always enjoyed the XBL gear I've played with. Be interested in seeing the specs on them. Did you go with XBL on the tweeter as well? Not many of those out there.