18 dayton ultimax box design help!!


Novice Member
Hey guys first time on here. Im in the finishing stages of my home theater and need some advice on a sub box enclosure.

After extensive research I feel the Ultimax 18" running on the inuke 3000 will be the best option for me and my budget.

I was looking at "Full Marty" box designs but I actually don't know too mush other than they can hit low and are good for home theaters.

I'm limited to a box of 22" high by 55" wide and around 24" deep but the depth is not too big of a concern as it can be adjusted. Id prefer that the height and with be as close as possible as the box will sit in a pre-build wall cavity.

The end wall is where the screen will be mounted and the hole in the wall to the right is where the box will go with an equipment rack above it.

Also I'm a woodshop teacher so if you want to suggest something difficult to build please do so. If it will sound better Im up for anything.
box measurements.jpg


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Active Member
Have you got to grips with or downloaded WinISD to model it? Im not too great with ported designs so someone else I'm sure could advise better on the best size/output for it.

But the dimensions you have to go with give you a good sized box which gives the ultimax some good breathing room. Is it mainly going to be for Movie usage?

Also have you measured the response in any way from that position in the room with a sub before deciding it will go there? Only asking because it may take some EQ to get the best of it if you are limited with placement options.

Do you have any DSP devices that will be able to EQ or an antimode or anything like that?


Novice Member
Hey thanks I'll try out win ISD. As for the rest I have not measured anything in the room, just hoping to get lucky because I am limited on space so that's the only location I could pull off. Do you think I would be better off using two ultimax 15s instead on the single 18? I can manage to place one 15 in the front right of the room in the location in the picture (front right) and place a second 15 in the rear right.

But I would need to run both 15s on the inuke 3000..

Thanks so much for your input!!


Active Member
If you went 2 x 15's you'd almost certainly have to go sealed as the ultimaxes like a big box, but yes 2 x 15's in theory give you 353.43 cm2 of cone area vs 254.47 cm2 for the one 18, so not a small amount by any means. However having a ported sub vs a sealed will be a different type of sound.

For a very rough graph (like I said Im not good at ported builds in WinISD) of the 2, the Vented 18 will be loud around port tune and then drop off whereas the 2 sealed 15's would give a smoother roll off. But the other caveat is that the 15s have slightly less cone excursion than the 18s do, we're talking 22mm vs 19mm.

Here are the SPL and excursion graphs for a quick mock up I did using a 350L box and 1100w of power and the 18 tuned to 15hz


It basically shows that in the equivalent box, the 18 would have the edge down low (<30hz) because of the port helping to lift the lower end and the 2 x 15's would have it in the higher ranges above 30hz.

Note: the above graphs do show over excursion, this would be when you're really pushing the system and entirely up to you as you can just turn it down a touch, they're not going to be quiet at that volume anyhow.


Novice Member
Thanks again for the insight, I would be able to put the 15s in ported boxes. Both would be in their own boxes one at the front right of the room and the other at the rear right of the room. I could even manage to build a T-wave box for the front one possibly if anyone on here thinks that's a good idea in a theater room. Also would is be a bad idea to have one 15 in a ported bax and another in a sealed enclosure, or would that cause problems?

The Dreamer

Distinguished Member
It is generally recommended to avoid mixing ported and sealed subwoofers - balancing their different characteristics can be problematic, or so I believe (I’ve never tried).

I run 2 UM18s in sealed enclosures from a single inuke 6000 DSP, and they give more bass than most regular folk could ever wish for.

For me, the simplicity of a sealed box design giving a known response and able to dig deeper (if fed the power) than ported designs won the day. I was also depth limited to about 14”, so Marty’s of any sort were not an option.

Of course, a ported design will, at it’s tuned frequency, produce more oomph than a sealed unit for any given power input, but then care has to be taken not to feed the driver too much power, particularly below the tuned frequency, as the driver can easily reach its operating limits. And honestly, how much oomph do you need? Either sealed or ported, when displacing the amount of air an UM18 can, will produce more than enough for most people - so the whole ported vs sealed debate becomes mute!

Whatever you decide, for optimal results, I’d suggest if you go down the multiple sub route, to build them identically. They will blend in better, and you can simply feed them the same power (even driving them from the same amp possibly).

Just my two cents.


Well-known Member
If you’re running 1 of these subs what would a competent and quiet amplifier to pair it with but still giving it plenty of juice?

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