hi all! im a college student that is sick of not being able to purchase high end audio equipment but loves music. So i did a little research and stumbled upon the mj18. I've decided to do my first DIY sealed subwoofer using a single mj18 and buttkicker amp. I do know that they recommend 2.8 cu ft for a sealed mj18, but It looks as if alot of people are using larger boxes. Since im new to this, im uncertain as to why many of you have deviated from the "recommended" size. I would greatly appreciate if you guys could give me some tips, recommndations, and possibly some box dimensions on building my first sub without using a eq. I will most likely be using 3/4 mdf or plywood. Thanks!

Edited July 17, 200718 yr by sil180sr

thy say it's a Lil choked in 2.8 I say do it in a 3cu.ft box....I have a MJ-18 but it's ported so dont much about what it likes sealed

Edited July 17, 200718 yr by JEREMIAH....

I prefer response in 3.1.

3-4cf for music, 4-6cf for home theatre.

I feel the thing is that you can build a similar size and adjust from there to fit your preference. Either way the MJ is going to have a nice clean and deep sound.

What box dimensions do you guys recommend for this sub? Ive been trying a few sizes and have mostly been getting over 4 cu ft. I dont might the size but will something this large lower the response of the sub? I would like a tight and fast responding sub. Ive been trying to get around 3 cu ft but isnt this sub just too large to acheive something that small? Thanks!

What box dimensions do you guys recommend for this sub? Ive been trying a few sizes and have mostly been getting over 4 cu ft. I dont might the size but will something this large lower the response of the sub? I would like a tight and fast responding sub. Ive been trying to get around 3 cu ft but isnt this sub just too large to acheive something that small? Thanks!

Airspace is airspace. dimensions dont matter. as long as it fits!

How much power do you have???

I have to wonder, if you're going to invest 4 or more cubes, why not port? It seems to me that sealed is only worth it if you are too small to port it.

Some people like smooth frequency response too....

I have the MJ-18 in 2.2 sealed. It is too small, F3 is too high for my liking. Don't get me wrong, it sounds good, but it doesn't have the LF impact I desire. I think 3ft^3 would sound great though.

Sooo, IB I go.

Wouldn't ported have a flatter FR over the targeted bandwidth of the driver? In 3 cubes, ported tuned to 30-35 Hz is definately more flat than sealed from 30-35 Hz up. If you're going for very low frequency extension (<15 Hz) or are in a car, I can see going sealed or IB, but if the target is music, and you're already burning up 3+ cubes, why not go with higher senstivity, flatter FR, and lower cone excursion? Especially if you are not using EQ!

It wont have the proper synergy. And then you have to MAKE SURE you calculate the airspace AFTER port displacement. Otherwise your rear wave will be out of phase and you cant set your gains low.

There...that might help cure the voices in my head.

Im thinking something like a 21" cube for the enclosure. Im using a buttkicker amp to power the sub. Has anyone had a chance to try the mj18 with a 4.2 cu ft sealed enclosure? What do you guys think? Thanks for the replies!

I installed the mj18 with the parts express buttkicker buyout, in about 3cf. It sounds awesome, really deep and smooth response. You will love it. The buttkicker amp is really great, I ended up buying one for myself to power my tc1000 12 at 2ohm.