OD Audio 280XL 15" subwoofer enclosure recommendations

[danielmax]

Hi guys! I own an OD Audio 280XL 15" subwoofer (let's say it is custom made here in Italy, below some pictures). I want to report some of its characteristics, which I think they are useful for what I'm asking. It came to me without T/S parameters. Anyway, it has very stiff suspension, an Fs around 45Hz (but it hasn't  broken in yet).  I think it was built more for SPL purposes. Anyway, I want something between SPL and quality. It has about 2.5kW RMS and an xmax of around 22mm one way (real value, measured distance from the top plate to the end of the voice coil).

 

First, airspace. On the basis of your experience, how low is too low? Producers like Sundown Audio recommends values around 4cuft. In my car I go particularly well with 3.5cuft. Is that a little low?

 

Second, port area. I heard 12-16 sqin per cuft is a good range. Because of space I can't go with big values of port area. So, I take 12sqin per cuft, 12*3.5= 42 (sqin).

 

Third, tuning frequency. I heard 32-35Hz is a good range for SPL/quality. So, let's take 33Hz (for the type of music I listen to). Again, on the basis of your experience, does this makes sense?

 

So, 3.5 cu.ft, 33Hz and 42sq.in port area. Is this a reasonable box for a 15" subwoofer? Consider that I have never built an audio system before that... So I don't know how it will sound...

 

And, in the end, just a curiosity... I noticed that it has two spiders. One can be seen from bottom, the other from top. They aren't glued together, and they are about 5cm apart from each other. What does this mean? There are some advantages?

 

Thank you very much for taking the time to consider my doubts, I really appreciate it.

[Joe X]

You need to fully break in and measure parameters to figure net volume and port area, of course you can try contacting the manufacturer.

 

Generic rules for building enclosures work better with average subs, specially port area, most mistakes on generic boxes are due to low port area which results in less output at tuning or port noise.

 

Just by looking at the pics my guess is that you simply won't have enough airspace to do a proper enclosure.

 

[danielmax]

6 minutes ago, Joe X said:

Thank you for the reply. The photo is quite illusory and consider that the cover of the spare tire will be removed, allowing an optional height of 5-6cm. Width 94cm, Depth 40cm and height 43cm. These are the maximum values, if I don't tilt the seats a little bit ahead. If I do that, I will have an extra depth of around 10cm. But this one is only a reserve card, if things go wrong... Then there is the possibility to increase depth again by adapting the shape of the box to the running of the trunk. I calculated that I can put a 4/4.5 cuft net volume box (total volume is around 7-8cuft). But possibly I want to built a quite simply box, and not to tilt the seats. In that situation I can get max 3.5cuft...