Ultimax 15” need help figuring out proper port length

You didn't state what tune you want. Also, sealed will give you more extension over ported and ported will yield more SPL at tune. Here is a tutorial on winisd

I am thinking between 15 and 20 Hz. The one that has the best response I suppose.

Heres some info about a person who did something similar.

Full Marty with Ultimax 15 | AVS Forum

Thanks for the information guys. I’m disabled so my response may be slow sometime, but promise I’m taking the advice seriously.

Its cool, do what you can. Building based off of a Marty (do a search for the Marty sub) and a 15" sub driver will be your easiest option. If you are unable to build the box yourself a cabinet shop can make the cuts for you or you can order a flat pack from a place like GSG Audio.

Someone gave me a 10cf box and it has a 6” round port he cut off for another project. There is enough port left to put a collar and extended it to the length that I am asking about.
I’m using the Dayton DSP1200 amplifier and it has adjustable highpass at 16/18/25 hz . My theater room is about 2400 cf. I’m wanting more spl lower down to the 16hz high pass on my amplifier if that at is to low I am open to suggestions. Again thanks.

alright, with a 10cu/f box and a 6" round port and assuming that amp puts out a full 1000watts

with a 16hz tune it'll damage the driver, you'll need to limit the output to less than 500watts to prevent over excursion. The tube length needs to be 25.25" long.
with a 19hz tune the same thing applies, tube length is 16.6"
with a 25hz tune you can probably get away with this but the excursion is a bit high between 29hz and 37hz but it can take the entirety of the amp. tube length is 7.75" long.

I doubt that it puts out the full 1200 watts also. I also never listen to reference spl usually -15/20 db. Between the 16 and 19hz tune is what Im thinking. Thanks for the simple answer to my questions.

Lennon Blanchard said:

I doubt that it puts out the full 1200 watts also. I also never listen to reference spl usually -15/20 db. Between the 16 and 19hz tune is what Im thinking. Thanks for the simple answer to my questions.

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Is 10cf a little to big? I also have a 7.8cf cabinet that I could just as easily use a also has 6”port.

Lennon Blanchard said:

Is 10cf a little to big? I also have a 7.8cf cabinet that I could just as easily use a also has 6”port.

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When calculating those enclosure volumes are you subtracting the volume taken up by the port?

squiers007 said:

When calculating those enclosure volumes are you subtracting the volume taken up by the port?

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Yes. The box is a bit over 8cf. 7.8 is a rough estimate after port and driver volume.

Lennon Blanchard said:

Yes. The box is a bit over 8cf. 7.8 is a rough estimate after port and driver volume.

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Well, I figured it would of made a bigger difference but there isn't a large difference between the 7.8 and 10 cu/f boxes.

Honestly, the larger box allows your port length to be shorter.

Trimlock said:

Well, I figured it would of made a bigger difference but there isn't a large difference between the 7.8 and 10 cu/f boxes.

Honestly, the larger box allows your port length to be shorter.

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Thanks so much for being patient with me. Would the same port length work for either size box? If you were to have only the options that I have what would you choose and why ? I’m very interested in opinions.I’m thinking maybe f3 at 20hz and lower if possible is what i would like.
10cf 6”port
7.8cf 6”port
3.0cf sealed
Dayton Ultimax 15” Dayton DSP-1200 amplifier with 16/18/25hz high pass options used in a 2400cf closed room for 100% movies. I’m wanting to gain more spl under 30hz. Again than you and anyone else that may have an opinion.

Real world, I'd guess that amp puts out closer to 700-800 watts. Add in DSP, the mechanical robustness of the UM's, and not cranking it to 11 and you should be fine even with the bigger box. The lower tune should help flatten the rise around resonance due to the higher Q(lower damping) of the driver.

Vergiliusm said:

Real world, I'd guess that amp puts out closer to 700-800 watts. Add in DSP, the mechanical robustness of the UM's, and not cranking it to 11 and you should be fine even with the bigger box. The lower tune should help flatten the rise around resonance due to the higher Q(lower damping) of the driver.

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800 watts is what I am thinking too. I’m now thinking of using the smaller 7.8 box if there is not a big difference. I’m wanting more spl under 30hz cause it’s rolling off around 30 in the sealed box and I love the feeling and sound of low bass.

I’m i going to try the 7.8 with a 6”port 15.6” long for a 19hz tune. C someone let me know the port length is ok. And should I expect agood bit lower pant flapping tune
?

Trimlock said:

Port should be 22.5" long for 19hz, at 15.6" it will be a 22hz tune.


There not a massive difference between a 16 and 19hz tune, which is to be expected, 19 is only 20% of an octave above 16. the 19hz tune will be safer, I'm plotting using 1000watts.

View attachment 3146188

The teal is 16hz and pink is 19, the yellow is 25. The pant modulation will be slight, at 110db in the teens, you'll get some assistance with room gain and hoping you aren't on a concrete slab.

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That explanation with a simulation chart is exactly what I wanted to know. The 19hz tune is perfect for what I am after. So 22.5” long 6” port is what i’m going to do. Thanks for the help.