1 HDC3 18" or 2 HDS300 15"

[Triticum Agricolam]

Who knows. I've seen similar specs on other Brands of woofers where the only difference was the cone size. And how does the box effect that?

The sensitivity number just doesn't really matter for subwoofer usage. The problem with it is there is no standard way to calculate it. Is it 1w/1m, or 2.83v/1m? If they used 2.83v/1m were they 1/2/4 ohm coils? In parallel or in series? All of these will cause different results. What frequency was it measured at? Usually its done at 1,000 hz, how applicable is that going to be at subwoofer frequencies?

The other problem is its measured in free-air. If you put the sub in a ported box, the box gives you a gain in efficiency around tuning, just how much gain is completely dependent on the box specs (size, tuning, etc).

The point is sensitivity is COMPLETELY meaningless for car audio subs.

[RageQuitForLife]

so another quick question, when tuning a ported box, should i tune higher than what i want to listen to? my box right now is tuned at 30hz because i listen to music around 24hz-34hz. so whenever i build another box would it be better to tune it a little higher or would it not really make a difference?

[Triticum Agricolam]

so another quick question, when tuning a ported box, should i tune higher than what i want to listen to? my box right now is tuned at 30hz because i listen to music around 24hz-34hz. so whenever i build another box would it be better to tune it a little higher or would it not really make a difference?

Depends on your goals. Output drop off below tuning pretty quickly in most situations. You can usually get a few Hz of good output below tuning but that's about it. Tuning higher while keeping box volume the same will usually get you higher peak output, but at the expense of low end extension. Everything is a trade off.

When I design boxes for my own use I like to tune to the lowest frequency I want to be able to play. This helps smooth the frequency response, it also helps protect my sub since I don't have a subsonic filter on my amp. I do lose some output doing it this way though, but that doesn't concern me. For you it really depends on what your goal is. It may be helpful to play around with a tone generator to see exactly where your output rolls off on the low and high end, when you build a new box you could make the port adjustable and play around with the tuning to see what works best for you.