Xi 12 DVC Sealed or Ported Box?

[jstenger]

Thanks to the awsome people at Exile, I just bought an Xi 12 DVC. I am looking at two different boxes. The first is a 1.3 cu ft sealed box, which according to Exile, would give me an SQ sound. The second is a 1.6 cu ft ported box, which according to Exile, would give me an SPL sound. Any thoughts on which box to get and why would be great. Thanks.

[Jason05216]

I'm a noob on this stuff, what's a SQ sound and a SPL sound?

[David Analog]

SQ = Higher Sound Quality which usually denotes a broader and more even bandwidth. SPL = Higher Sound Pressure Level which usually denotes a higher or peakier output over a narrower bandwidth.
You can have either SQ or SPL within the context of both a sealed and a ported enclosure.
With the woofer's Thiele/Small parameters (specs), the right bass box computer design, and someone who is adept at using it, you can create an alignment with very predictable results that best suits your likes and dislikes. You are by no means limited to two enclosure options.

[Brianinpdx]

Joe - here's some good enclosure 411 for you that relates to your Exile Xi12D but its also good general information for the group. Lets start with the woofer and amplifier combo. You want to make sure your woofer(s) rated power is similar to the rated power of the amplifier driving it. In your case you've got a conservatively rated 600W woofer being run by a javelin amplifier that produces 800W of CEA certified power. You also want to make sure the power delivered is in alignment with the impedance of the woofer. I get a lot of questions about this... In short that woofer is dual 4 ohm, which means paralleled at 2 ohms, you'll see 800W from the javelin. It works great. Check!

Knowing all this can help one decide which enclosure route to go as well. With 800W on tap from your Javelin, you might opt for a sealed enclosure. I like sealed enclosures that have a lot of power behind them. I don't care for sealed enclosures that are lacking amplifier power. A sealed enclosure is going to be easier to build, take up smaller space, and the music reproduction is generally going to be more linear type of response. Over all, its a more SQ approach than the Ported option (which I'll cover in a moment). In a sealed enclosure, all the bass notes are going to hit with the same amplitude as compared to its ported cousin. From an application point of view, the smaller the sealed enclosure is-- the quicker the roll off is going to be. I call this a SPL alignment which is limiting the frequency range extension of the woofer. The larger the sealed enclosure is the more frequency extension your woofer has (think lower bass notes). So as a rule of thumb, I look at it like this: Sealed: small side of the target CU = SPL / higher power handling. Higher side of the target CU = SQ/ lower power handling. So in the real world, if you drop that Xi12D into a 2.5 cubic box, it will sound wow great, but not handle so much power. That could be a potential problem with 800W powering it. In summary: Sealed boxes sound great over all and we want to make sure the alignment will work with the proper power behind the woofer. For your Xi12D paired with the Javelin your most effective range is 1.1cu up to 1.5cu.

So all that sounds dandy right? Well here comes the Ported school of thought. Ported enclosures don't offer that super linear freq response that the sealed does. In fact they stray away from that notion and instead offer a +3dB bump in output at the port tuning frequency.. which by the way can be manipulated. 3dB is a lot. In acoustical terms thats twice as loud. In simple terms, thats the upside. The downside is that ported enclosures are typically bigger than their sealed cousins and are harder to build and harder to fit into a boat. I usually suggest people not mess with a ported enclosure build if they don't know their way a wood shop because to much can go wrong in the execution / end result. On the plus side, I think ported enclosures are generally a better choice given the open air marine environment the tow boats are in. Remember, you have a lot of noise to compete with: engine, people, wind, water, other boats on the water etc. So that +3 bump makes a meaningful impact in performance. The same enclosure volume ranges apply to the XI12 in the ported world as well. On the small SPL side, your looking at 1.7cu and on the higher range your looking at 2.2cu SQ.

I think people get WAY to carried away chasing after the definition of what SQ really means. To be candid, the over all sound quality is going to be effected more by the poor execution of a enclosure build process than by anything else. I spoke to a Moomba owner today talking about a sealed enclosure and about the 3rd time I stressed caulking the seams (to seal it) and use a gasket around the back side of the woofer (to seal it).. he got it! And once that woofer is mounted, don't go removing the damn woofer period. It's to easy to loose a good seal. To further all this design talk, the quality of materials is important as well. Using MDF is just a plain bad idea. Think sponge. It gets wet, and its done. It gets moisture on it, and its done. Consider a marine plywood or some composite material. A lot of guys ask me about wall thickness to use. What needs to be understood is that if your box walls flex, its not going to perform as predicted. So over build these things and you'll be happier in the long run.

No matter which design you opt for (or woofer for that matter), amazing sound reproduction can be had in either Ported or Sealed. Or Band pass too. There are so many factors that influence the final result, but don't let it paralyze you with crazy tech speak. Keep the design simple. Keep it basic. Build it well... and you'll be happy in the end.

-Brian @ Exile

PS: We could go around and around with this information and debate it till the cows come home. I've purposely left out stuff like subsonic filtering and other areas to talk about. This is just a reference for you to consider what is important to you on your Exile build. Ported or Sealed-- Thats the question my friend. hehe. Enjoy!

[David Analog]

So much info above that is dead in the wrong I can't address it all. It's so wrong you can't debate it.
+ 3 dB is not perceived as twice as loud. + 3 dB equates to double the power which is completely different. Twice as loud would equate to between + 6 to 10 dB which is 4 to 10 X power.
Bass reflex or ported can be super linear and super sound quality depending on your design objective. The bass boost 'can' take place in the roll-off region with zero peak in the response. So you can use the alignment for either extension or amplitude. Most of the ultra expensive studio monitors are ported, what your music is mixed on! A majority of home hi fi speakers in the realm of $10K to $200K are bass-reflex/ported, including the flagship B & W 800 Diamond to the highly acclaimed $210K Wilson Audio. Audiophiles making that type of investment will not settle for less than perfection.
Besides handling less power, an Xi12 will sound terrible in a 2.5 cu.ft. sealed box. It will go deep but will sound flat, acoustically dead and with a distinct midbass null.

You should expect more concise and accurate technical assistance.
Start with the boat and explore how much external enclosure displacement you have available.
Then decide how much tolerance you have for a complex box build.
Then get an exact box design to meet your particular objectives.