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Discussion Starter · #1 ·
I'm looking around for a box size to fit my available space to house 18" ultimax subwoofers. The Martysub variants are just a little too big for most of my spots (especially if I want to do two of them). I did see an interesting shape in the stonehenge as it would potentially slide behind my couch, but I am a little skeptical of the specs. I may end up with sealed purely due to placement issues, but we shall see!

MiniMarty is 25"x23.5"x38" and tuned to 18hz at about 9 cubic ft
Stonehenge is 30"x30"x16" and tuned to around 18.5hz at 5.4 cubic ft

The MiniMarty has substantially more cubic ft and I assumed to tune lower you need more net internal volume for ported boxes. How would the stongehenge be tuned at 18.5hz given how relatively small it is? Are there downsides to that smaller size?
 

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Discussion Starter · #2 ·
After thinking on it, I assume the difference will be in output levels, with the lower cuft cabinet at a disadvantage even though they are tuned to the same freq?
 

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rule of thumb is the bigger box will have more SPL down low where as the smaller box will have a steeper roll off well before port tuning. Depending on the driver of course.
 

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Also you can actually make the Marties a different shapes as well. I just went through that exercise over the holiday building (4) 'Marties' -- none of which followed the standard configuration. The thing that has to be adhered to is internal volume, port area, port length. One of mine was 12.5" deep and 57.5" long (really on the edge of how shallow you can build one) by 25.25" wide. The other was kind of L-shaped that varries from 12.5" to 18" deep, 42.75 long by 25.25 wide. Both have the same internal volume, same port area and port length.

So, if you need to change the box dimensions you can download the free spreadsheet and have at it. Also you can download cutlist to help you lay that out. I went through 6 sheets of MDF for (4) boxes and had a utilization rate of almost 96%!

Keep in mind these boxes, and I built ones just a bit smaller than the Johnny sub, are big and heavy. 1 1/2 sheets of MDF plus bracing is not to be taken lightly!
 

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I'm looking around for a box size to fit my available space to house 18" ultimax subwoofers. The Martysub variants are just a little too big for most of my spots (especially if I want to do two of them). I did see an interesting shape in the stonehenge as it would potentially slide behind my couch, but I am a little skeptical of the specs. I may end up with sealed purely due to placement issues, but we shall see!



MiniMarty is 25"x23.5"x38" and tuned to 18hz at about 9 cubic ft

Stonehenge is 30"x30"x16" and tuned to around 18.5hz at 5.4 cubic ft



The MiniMarty has substantially more cubic ft and I assumed to tune lower you need more net internal volume for ported boxes. How would the stongehenge be tuned at 18.5hz given how relatively small it is? Are there downsides to that smaller size?


UM18’s don’t like small ported enclosures. Anything less than about 9cuft is making compromises. Jonny sub is as small as you should go but will still be a compromise to 9cuft.
If you cannot build it ported large enough go sealed.
How big is the room you are putting it into? Is the room open to other areas of the “home”? IE open doorways. Or is it a sealed room?


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Discussion Starter · #6 ·
UM18’s don’t like small ported enclosures. Anything less than about 9cuft is making compromises. Jonny sub is as small as you should go but will still be a compromise to 9cuft.
If you cannot build it ported large enough go sealed.
How big is the room you are putting it into? Is the room open to other areas of the “home”? IE open doorways. Or is it a sealed room?


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Room is an L shape, about 1600ft3. It's not possible to seal as it is open to a stairwell, which goes to the upper level which is very open.

Overall it looks like the larger enclosure would work realistically in only 1 spot of the room, but the smaller ported one would allow me to put one under the screen and a 2nd in a corner.

Since this is 90/10 HT/Music, I was thinking ported tuned low would be the way to go. Maybe single eq'd sealed 18 is the right move for now and adding a second since I plan to get an NX6000D amp as well.
 

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UM18’s don’t like small ported enclosures. Anything less than about 9cuft is making compromises. Jonny sub is as small as you should go but will still be a compromise to 9cuft.
If you cannot build it ported large enough go sealed.
How big is the room you are putting it into? Is the room open to other areas of the “home”? IE open doorways. Or is it a sealed room?


Sent from my iPhone using Tapatalk
Room is an L shape, about 1600ft3. It's not possible to seal as it is open to a stairwell, which goes to the upper level which is very open.

Overall it looks like the larger enclosure would work realistically in only 1 spot of the room, but the smaller ported one would allow me to put one under the screen and a 2nd in a corner.

Since this is 90/10 HT/Music, I was thinking ported tuned low would be the way to go. Maybe single eq'd sealed 18 is the right move for now and adding a second since I plan to get an NX6000D amp as well.
go as big as space will allow. I immediately regretted the micro for my ht, although I have since developed a space for it. I ultimately went with 1 Johnny and Marty cube and even then im second guessing the cube. I will build one more though for uniformity but I'm uncertain if that will be a Johnny or another Marty. If you can squeeze in 4, do 2 and 2.
 

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Room is an L shape, about 1600ft3. It's not possible to seal as it is open to a stairwell, which goes to the upper level which is very open.



Overall it looks like the larger enclosure would work realistically in only 1 spot of the room, but the smaller ported one would allow me to put one under the screen and a 2nd in a corner.



Since this is 90/10 HT/Music, I was thinking ported tuned low would be the way to go. Maybe single eq'd sealed 18 is the right move for now and adding a second since I plan to get an NX6000D amp as well.

In an open room to an open rest of the home I would strongly recommend a ported or horn style enclosure. Horns can be very large though. So for what you have stated for requirements, I would stick with ported enclosures. Sealed subs just won’t be efficient or effective enough to pressurize the “room”/open area.

Do you already own the UM18(s)?
If not, look into the VBSS subwoofers. It is a 18” pro-Audio speaker that is very efficient and can be tuned to 15 Hz. If you are not looking to get crazy loud, 2 of them will work with using a very inexpensive NX1000D amplifier. If you want more SPL just add 2 more. The enclosure is smaller in size than the Johnny and mini-marty subs.
Now, if you already own the UM18(s), then use a mini-marty where you can fit it and see if a “cyclops”(modified mini-Marty) will fit under your screen. You can lay any of the Marty subs on their sides to reduce height if needed.
Hope this helps.


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Discussion Starter · #9 ·
In an open room to an open rest of the home I would strongly recommend a ported or horn style enclosure. Horns can be very large though. So for what you have stated for requirements, I would stick with ported enclosures. Sealed subs just won’t be efficient or effective enough to pressurize the “room”/open area.

Do you already own the UM18(s)?
If not, look into the VBSS subwoofers. It is a 18” pro-Audio speaker that is very efficient and can be tuned to 15 Hz. If you are not looking to get crazy loud, 2 of them will work with using a very inexpensive NX1000D amplifier. If you want more SPL just add 2 more. The enclosure is smaller in size than the Johnny and mini-marty subs.
Now, if you already own the UM18(s), then use a mini-marty where you can fit it and see if a “cyclops”(modified mini-Marty) will fit under your screen. You can lay any of the Marty subs on their sides to reduce height if needed.
Hope this helps.


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Thanks for suggestion the other option, I haven't looked into the VBSS subwoofer build before. Since I haven't bought anything yet, I'm wide open for suggestions!

I never listen to movies at reference level, usually in the -10 range at most. Those might cover the needs as long as they dig deep enough. Seems I'd save quite a bit on amp for sure. On their side, I think they would just barely fit under my screen, which is nice.
 

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Thanks for suggestion the other option, I haven't looked into the VBSS subwoofer build before. Since I haven't bought anything yet, I'm wide open for suggestions!



I never listen to movies at reference level, usually in the -10 range at most. Those might cover the needs as long as they dig deep enough. Seems I'd save quite a bit on amp for sure. On their side, I think they would just barely fit under my screen, which is nice.



Search for this thread:
“The V.B.S.S. DIY subwoofer design thread”.
In the first post should have all the dimensions you would need. I would suggest the dedicated 15Hz design. 2-4 of them should be enough for you... the thread is fairly long but filled with great information and guys that have built and experienced the speakers. Plus that thread has all the EQ/DSP settings for the subwoofers that you can download directly into the suggested amplifiers depending on how many you want to run.

2x VBSSs will have insane mid-bass and will have more ultra low frequency response than any big box store bought subwoofer.

4x VBBSs will beat 2x Marty UM18s in chest thumping bass (gun shots/punches/explosions) and are
 
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