95Honda

Good luck...

You don't owe me anything. A single 4" would probably be OK, you just need to see what the vent velocity will get up to. It would also probably be OK as long as you didn't go full retard with power Keep it well under 500 watts or something logical like that... I used to run Brahma 12's (28mm xmax) with single 4" Aeros per sub due to space limitations and they did surprisingly well... Another nice thing about the Aero is it is thin and doesn't eat up as much volume as a slot vent made of 3/4" MDF...

Just watch Iso loading with a box that is almost 2X a single driver's VAS, you can easily run into mechanical limits, especially with Qts as high as those drivers have... SSF filter will not just be useful, but 100% required...

I modeled for 33 Hz, not 24... You can get any volume at any tuning if you can accommodate the vent. Problem is, when you tune really low and have a lot of vent area the vent might eat up as much room in your cars as the actual enclosure does... It starts getting out of hand pretty quick. I'd go sealed or get different drivers. I really don't think they'll sound great vented, I haven't even looked at group delay, but I bet it isn't great, either... Honestly, with those drivers, if you had the skill, I would put one of them in a 4th order band-pass. If you don't have the skill, a pair sealed would be just about as good...

I've never used Torres. I got around 24" long, so that is close enough... I'd go sealed with those drivers... They would probably sound best that way...

I modeled them, they will have roughly 3db of ripple in the pass-band (as expected) with an alignment like you are looking at, this can be a little peaky but you might be fine with it, it can be downright annoying depending on the cabin gain you have... If you went with a box that was roughly 44 x 14 x 17 internal with a 4" x 14" vent you would be around 15 m/s max vent velocity at around 1000 watts, assuming they have an xmax around a 1/2" or so, just a guess on my part... If they have more xmax than that you'll have higher vent velocity, but really, you would probably be OK... They look really nice sealed, and would probably sound pretty good. You would loose a little on the very bottom, but I bet they would sound better...

I didn't model, but that combo looks like it may have a lot of ripple in a 4th order vented alignment... Fs is kind of high for sealed, but with cabin gain they may sound good...

No. Never. You can run your amp into hard clipping at 100 amps draw at a 4 ohm load... Like everyone is telling you, your ears will serve you best. Looking for visible clipping on an O' scope or with some type other type of distortion indicator isn't just pointless, but it's asinine... Here's why... If you listen to any popular music on any FM radio station it is heavily compressed (clipped) from the get-go, before it evens leaves your head unit. I just don't mean a little bit, it is clipped all to hell... Most rap CDs are the same, MP3's, even worse... This is why trying to chase that threshold of a little distortion is so pointless that I don't even understand where people get this crap. A little clipping doesn't hurt a thing, if it did, everyone who listens to the radio would blow their speakers... Manufacturers have to play it safe and tell you to stay away from clipping and that it will ruin their drivers. They only do this because there are too many morons out there who don't know when enough is enough, not because they actually believe the info they are giving you...

Not too many people tune below 30Hz as there isn't a whole lot of content down there. If you truly do listen to music with a lot of 20Hz content, that is where you may want to tune, or go sealed. Ditch the 6x9's BTW, all they do is make everything else sound worse...

The gain knob sets the voltage sensitivity of the amplifier. It doesn't do anything else. At all. No matter who tells you different. At all. Seriously... There is nothing at all wrong with having it cranked WFO if that is how your system works best...

Sure, 80-100 square inches will work OK with any 18" driver at any power level at any excursion. But, without modeling, you have no idea if that is too much (wasted enclosure volume) or too little (compression) vent area. Every alignment is different, and without modeling you cannot calculate optimum vent dimensions, period...

Just remember, it is pointless to measure the overall diameter of ANY stranded cable, it tells you absolutely nothing. You need to measure the diameter of an individual conductor and then multiply that by strand count to calculate gauge. Any other measurement than this is completely misleading...

I thought he had his havoc an 18. That's why I said it was too small. Even if it is an 18 you still have no idea if the port is too small, that is the point. You have to know how much power he has to tell him anything about the port...

How did you measure current (or impedance)?

I am totally confused. You went from "sub has no kick at all" to "this sub got bloody loud and setting off car alarms" If it is bloody loud and walking all over multiple sub set-ups, what is the problem? The dust-cap gets warm, I get that. Have you leaned on it for any length of time? It hasn't blown yet, right? You have a decent amp that does 2.5 KW, right? I guess I don't see the major problem, but I am not getting consistent info from you. Is it not loud enough or are you just worried about the dust cap heat?

You have no idea if that is too small for an 18, or any driver for that matter, without modeling for vent velocity with given power drive level. There is no rule of thumb for port area...

I have no idea where you are getting your info, but it sounds like you are being miss-led. You need to take a step back and think about what you are doing. Research what the amp gain is for. Research cabin gain and most musical material content before you judge the usefulness, or uselessness of your bass boost. Also, you need to get someone who knows what they are doing to help you out. Something is wrong with your install, and it will be mental masturbation trying to figure it out on the internet...

That amp can produce close to 5KW of power, with the right signal. It doesn't necessarily need to be clipped to do that. This is more than that sub is rated for. Also, all clipping indications from the amplifier itself are just based on a comparison between input and output signal. You can run a heavily compressed signal into the amp, it will produce well over 2.5KW and there will be no indication whatsoever of clipping. Also, clipping in itself doesn't hurt anything, at all. It never has. What you need to understand is that you can easily fry that sub with your amp. It is immaterial how you get to that point, just know you can. There is nothing wrong with using bass boost, eq, etc. You just need to understand that you have the potential to overdrive the subwoofer. Be smart, if you hear distortion, turn it down. If you get to a point where you keep turning up the volume, but it isn't getting any louder, you need to stop. When you get burning heat smell, turn it down... It is just a little common sense, that's all... BTW, it should be loud as hell with that amp in a vented enclosure. If it isn't, something is goofed up somewhere, seriously...

I wouldn't worry about. Additionally, there isn't a man alive that can tell you exactly the temp threshold of the dustcap before thermal breakdown of the voice coil, just too many damn variables. Don't overthink this. Use your nose and ears. Also, don't forget that REGARDLESS of your settings, that amp can produce WAY more power than that SP4 is thermally rated for...

Subs only convert a few % of the power they are given into acoustic energy, the rest is heat. Your 2500 watt amp is making the sub dissipate well over 2000 watts of heat. That is why the dust cap is getting hot. Some subs don't have a good thermal connection to the dust cap, yours does, that is why it gets so hot. In reality, it is just helping with heat dissipation.

It will get louder at 1500 watts than any other of the other subs in the line, it is one of their most efficient drivers... The 2500 rating is a thermal capacity rating, it has nothing whatsoever to do with power requirements, at all, in the slightest. Seriously. 1500 watts isn't low power, for any driver.

They are all pretty similar, output class for output class...

If you want a proven design, that works well, build a set of LAB Horns. You could easily do the set under $1000. I have built a set, they sound good too. You need someone who really knows what they are doing with woodwork to help you. If you are honest about it, and really intend to see the project through, there are plenty of adults that will help you, you'll just have to do the legwork. If you are in a High School that has a woodshop, it would be a great project. I built a set of Speakerlab K-horn kits in High School woodshop, it took a month, but was a great project. Search the LAB Horn for plans. Partsexpress sells the 10" Eminence drivers...

Best way to do it, IMO...