so i have a Kenwood KFC-W3011 12" sub that my cousin gave me in his box that he built. it sounds pretty good in this box but i want to build a different one. mainly because he eventually wants the box back, he is just letting me borrow it to see how i like it.

so for starters the box is almost 3 cubic feet (see picture) and this sub calls for 1.5-2 cubic feet. the port is just a straight port not an L or anything. That part is where im lost.. I dont know what i should do inside the box, do i want a L port? or do i want a straight port? or maybe something else confusing? Ive heard tuning the box to about 35HZ is a pretty good number but im kinda lost there too. there is a sea of information out there and it seems like everyone has different ideas on what to do inside the box.

I've seen a few weird designs on the internet that work with 45 degree angles inside the box to bounce the sound around and out the port which makes sense to me, and which is also why a straight port makes no sense to me; i would think the sound would go straight back, bounce off the back wall and mostly get directed back towards the sub and not out the port. (i could be completely wrong with that idea and most likely am lol)

Complexity of the build is not an issue, i have everything required to build it.


Here is my art work in action lol. this is the Box i have now:




Example one is something like what i saw on the internet and Example two is an L port idea. (SIDE VIEW)







So what might a design like Example one do to the frequency of the box? or how do you figure out what it would be? if i had to guess i would say its still just the length, width and depth of the port then the TOTAL volume of the box (meaning after you subtract all the space taken up by the other walls) I tried looking for these answer's on line but there really isn't one to what this box design will do, and probably for a good reason lol.

Sorry for the long post and the not so easy questions but hopefully this will help someone else that is looking to do the same thing when the questions get answered.

 

You are right and if you'd like help with this I'd be glad to help you out. The "NET" internal volume is the internal volume of the enclosure minus the volume used by the port, the sub and anything else that may be inside such as bracing, parts required to mount/install plexi, etc. Ports usually have the angles and such to help with air flow through the port, but think of it as more of a flow of air such as from a fan than a single sound wave "bouncing" in and out of the box. The shape of the port, whether or not it's straight, L shaped, labyrinth shaped, or anything else is usually dependent on the length of the port needed to achieve the desired tuning. Sometimes a person has to get creative to fit a really long port in a box which is where all those bends and things come from.

At any rate, if you'd like some help, lemme know and give me the max dimensions you'd like to stay within and any other restrictions you'd have.

 

Ahhh ok that makes much more sense.. the Labyrinth shape is to extend the port, i didnt know if all the extra channels would be considered part of the port. that answers how you can have a 60 inch port when tuning your box to a lower frequency.

but i would very much appreciate your help with a design! As far as size of the box goes, the 1.5-2 cubic feet limit of the sub comes before my limits, unless you want to do away with the Sub limit? in that case if you could keep it to about the same size as the box i have now that would be preferable.

I also listen to pretty much every kind of music, Soft rock, rock, metal, hard metal, hip hop, R&B and country. So for tuning the box i really dont know what i would want.

But if you could think of a design you think would be good, that would help greatly! Thanks in advance.

 

I can sure help with that. I would recommend getting a little closer to Kenwood's specs for the sub. Having an enclosure that is much larger than the sub needs tends to cause some problems with boominess in the bottom end and the upper bass to suffer and not sound as fast and tight as it should be. That being said, 1.5 to 2 is a bit small for a twelve as well, 2.25 to 2.5 should be optimal for the sub and it's sound.

 

i was thinking 1.5-2 was to small also but thats not what kenwood claims. here is the site im getting my info from: Kenwood KFC-W3011 12" 4-ohm subwoofer at Crutchfield.com

with this box i do notice the boominess you are talking about tho. but do you have any ideas on what the tuning should be?

thanks for the fast replies

 

I'm thinking 2.25cuft at 33hz should be fantastic...

I'm going to run the T/S of the sub if they're available and try to verify the sub would agree, lol. Most big box manufacturers claim smaller than optimal enclosure sizes to make the product more appealing to consumers though. They've learned that if someone was looking at two subs that had the exact same specs, same everything except enclosure size recommendations. They seem to always pick the one with the smaller enclosure recommendations because they don't want the box to be big. People figure if they can get the same thing in a smaller size then it would be better, so manufacturers started claiming ridiculously small sizes for enclosures. I had a pair of Hifonics subs and they said .9 to 1.2 was recommended for a ported enclosure for a 12" sub. A 12" sub!! Hell, most 10's perform well in that size and several need larger than that.

All I'm saying is that you can't always go by the manufacturers recommendations, not always. It's always good to have them, at least for reference, but they're not always optimal.

 

After doing the math with the measurements you gave me it brings to light some information. Assuming all walls are 3/4" thick the GROSS volume is 3.18cuft, minus the sub and port volumes the enclosure is 2.58cuft NET tuned to about 38hz. The size is decent but the tuning is higher than what generally sounds good for a subwoofer.

Onto the issue...

WinISD shows this thing being real boomy in almost any ported enclosure. The EBP (efficiency bandwidth product, a calculated number used to find whether or not a sub is best suited to a sealed or ported enclosure) strongly suggests a sealed enclosure for this sub. It's probably not going to matter what size ported enclosure it's in it will probably sound boomy. I can get it to level out a little if you want to keep a ported enclosure for it, but it will not likely ever sound as good as a different sub that's better meant for a ported enclosure.

Let me know if you want to keep a ported enclosure or not. I'm usually a big fan and supporter of ported enclosures, but in this case here I'm thinking it's not the best application for this particular subwoofer.

 

Hmm yeah i used that same calculator and it said to stick with sealed. But im willing to do what ever you think is best, you know way more than i do so if you think ported wont sound great then ill do sealed. Sealed is a little easier for me to build to :P lol. but like you im a big fan of ported enclosures. I have the generic sealed wedge shaped box that i have my old kicker sub in (Old as in back when kicker wrote their name on the cone in yellow, so 15 years or so) but i dont think that generic wedge shape box would be the best for the Kenwood.

So just what ever you think will make the sub sound the best is what ill do. i could probably even get two boxes made from the one and a half sheets of MDF that i have.

Oh and yes, its 3/4 inch MDF

 

Well i figured i would bring this back to life. I did end up taking that sub out of the ported and put it into my sealed box and it sounded much better.

But now i believe that sub is on its way out because at low notes and lower volume it sounds like a piece of paper flapping and also not at low volume the sub cuts out (which i believe is a connection) I usually never have my volume over 60% so i dont beat on it, i think its just getting old.

So now im looking at some new subs, maybe something from Polk audio or DCON but i gotta do some research on what will work best for me.

 

You're right about the connection causing the problem with cutting out, however it's typically not a problem you can easily repair. Usually a driver cutting out at low volumes has to do with a tinsel lead having a connection issue where it connects to the voice coil. Whether the cause is actually age, abuse, misuse or any other reason a person can come up with, IMHO it wouldn't happen if it was build correctly in the first place. There's just not a good reason a solder joint should ever fail, or a wire break unless it was just built wrong. Regardless, I believe you're right in thinking a new sub is your next step.

What kind of amp are you using? What kind of music do you listen to most often? How much space are you willing to give up to the enclosure? The answers to these three questions can help a great deal with recommending a sub or subs for your application. While I have found that I truly enjoy the quality and output of the "Made in the USA" subs AA and Fi, SSA, and Incriminator offer there's nothing wrong with subs from Alpine, Polk, Kicker and many other well respected names. No matter what the sub is or how much is spent on it, if the enclosure is designed and built right then it will perform right.