Ported Ultimax UM18 design - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 22 Old 04-17-2017, 12:52 PM - Thread Starter
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Ported Ultimax UM18 design

Guys,
Any concerns with this design? Link to the WinISD for anyone that is interested: https://www.dropbox.com/s/dsxvugp40o...timax.wpr?dl=0

Looking at a 6 cu ft box with a single 4in diameter x 11" long port.

Rear port velocity maxes at 2.4 m/s at 15hz.

This UM18 is spare for me, I'm just looking to build it a proper box and potentially sell it to a neighbor.

Will post pics once I get started.
Thanks!
Jesse
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post #2 of 22 Old 04-17-2017, 01:31 PM
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post #3 of 22 Old 04-17-2017, 09:29 PM
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That port is tiny. Change the input power to 1600w. Velocity goes through the roof.
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post #4 of 22 Old 04-17-2017, 11:44 PM
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Quote:
Originally Posted by jhgkak View Post
Guys,
Any concerns with this design? Link to the WinISD for anyone that is interested: https://www.dropbox.com/s/dsxvugp40o...timax.wpr?dl=0

Looking at a 6 cu ft box with a single 4in diameter x 11" long port.

Rear port velocity maxes at 2.4 m/s at 15hz.

This UM18 is spare for me, I'm just looking to build it a proper box and potentially sell it to a neighbor.

Will post pics once I get started.
Thanks!
Jesse
The box and port is way too small, but Imo the box should simply be sealed. If you want a 18" ported box that is not giant try the rss460ho-4 in a 5-6 cu ft tuned to 20-23Hz with 3 x 4" ports or so.
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post #5 of 22 Old Yesterday, 01:57 AM
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Optimum Cabinet Size (determined using BassBox 6 Pro High Fidelity suggestion)
Sealed Volume 4.22 ft.³ Sealed F3 31 Hz
Vented Volume 11.79 ft.³ Vented F3 16 Hz
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post #6 of 22 Old Yesterday, 06:39 AM - Thread Starter
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Quote:
Originally Posted by splotten View Post
The box and port is way too small, but Imo the box should simply be sealed. If you want a 18" ported box that is not giant try the rss460ho-4 in a 5-6 cu ft tuned to 20-23Hz with 3 x 4" ports or so.
Okay, new design. I'm now thinking 13 cu ft.

I was trying to use 1 or 2 ports I have laying around, to save on woodworking time.
I have two 4.3125" ID ports that are adjustable to 11.75" long, but will buy whatever I need if anyone has a recommendation.

According to WinISD, with a 13 cu ft box tuned to 20 hz, the ports seem to work nicely.

Or is 2.2 m/s too much air velocity (@21hz with 1.6W)?

WinISD project here: https://www.dropbox.com/s/a8hgoxiid1...timax.wpr?dl=0

The guy on this youtube video said over 17 m/s is too much.
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post #7 of 22 Old Yesterday, 07:01 AM
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Ported Ultimax UM18 design

I'm looking at winisd right now the 6 cubic ft box your talking about and doing the smallest port it keeps plugging in for 6 cubic ft with a 6 inch port is 27 inches long tuned at 20 hz. But with that size port in the a 6 cubic ft box your air port velocity starts looking bad 27 hz and lower. Wondering are you open to a slot port? That helps a lot with air port velocity. The box if ported needs to be bigger than 6 cubic ft unfortunately. If you need help with box size and port size and length I can help you out. Since this isn't for your house check with your buddy and see what the max size box he can have in his space.
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post #8 of 22 Old Yesterday, 07:23 AM
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IIRC Port velocity is generally ideally recommended to be at or below 20ms. As long as its below that, you should be fine, and if its a "bit" above it like say up to 25ms, you should still be fine.
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post #9 of 22 Old Yesterday, 08:41 AM - Thread Starter
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Quote:
Originally Posted by eng-399 View Post
I'm looking at winisd right now the 6 cubic ft box your talking about and doing the smallest port it keeps plugging in for 6 cubic ft with a 6 inch port is 27 inches long tuned at 20 hz. But with that size port in the a 6 cubic ft box your air port velocity starts looking bad 27 hz and lower. Wondering are you open to a slot port? That helps a lot with air port velocity. The box if ported needs to be bigger than 6 cubic ft unfortunately. If you need help with box size and port size and length I can help you out. Since this isn't for your house check with your buddy and see what the max size box he can have in his space.
Thanks for your help.

Looking at WinISD, it doesn't look like the 12.0 box is worth it (for me).

In all these plots, the port velocity is under 3.7 m/s at peak. Unless I'm doing something wrong? But literally it is just using a single 4"x11" round port.

Blue is 6.0 cu ft F3 20.3 hz
Green 9.0 cu ft F3 17.0 hz
Red 12.0 cu ft 15.3 hz

Based on this, I think my preference is my 6.0 cu ft box. Just a mix of size/weight/place and minimal gains for the bigger box.
Please correct me if I'm making a mistake!
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post #10 of 22 Old Yesterday, 09:39 AM
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I have a slot ported um18-22 in a small enclosure and haven't had any issues with it yet. it's around 5.5 or 6cf. 17hz to 80hz flat within five decibels according to my REW measurements. it isn't impossible. slot ported is the best way to go to prevent lack of airflow. small isn't probably ideal since it does better in a big box but it's not impossible in something smaller. it just doesn't get fully utilized I'm guessing to its full potential.

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post #11 of 22 Old Yesterday, 09:41 AM
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Quote:
Originally Posted by jhgkak View Post
Thanks for your help.



Looking at WinISD, it doesn't look like the 12.0 box is worth it (for me).



In all these plots, the port velocity is under 3.7 m/s at peak. Unless I'm doing something wrong? But literally it is just using a single 4"x11" round port.



Blue is 6.0 cu ft F3 20.3 hz

Green 9.0 cu ft F3 17.0 hz

Red 12.0 cu ft 15.3 hz



Based on this, I think my preference is my 6.0 cu ft box. Just a mix of size/weight/place and minimal gains for the bigger box.

Please correct me if I'm making a mistake!


For some reason my computer won't do a screen shot today... so I took a picture using my iPhone. Here's a sealed 6 cub box and a 13 cubic ft box tuned to 16hz and slot ported.
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post #12 of 22 Old Yesterday, 10:58 AM - Thread Starter
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Originally Posted by eng-399 View Post
For some reason my computer won't do a screen shot today... so I took a picture using my iPhone. Here's a sealed 6 cub box and a 13 cubic ft box tuned to 16hz and slot ported.
Thanks for double checking my work. Apparently the version of WinISD I'm using is not working right. I loaded .50a7 and am seeing the port velocity now.

Looks like we're going to have to go big!
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post #13 of 22 Old Yesterday, 11:36 AM - Thread Starter
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Originally Posted by eng-399 View Post
For some reason my computer won't do a screen shot today... so I took a picture using my iPhone. Here's a sealed 6 cub box and a 13 cubic ft box tuned to 16hz and slot ported.
Any idea why your SPL is so much higher than mine? I'm using 1.6W. Max is about 91db.
Hot pink is 7.2 cu ft. vs 16 for the light pink.
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post #14 of 22 Old Yesterday, 11:41 AM
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Quote:
Originally Posted by jhgkak View Post
Any idea why your SPL is so much higher than mine? I'm using 1.6W. Max is about 91db.

Hot pink is 7.2 cu ft. vs 16 for the light pink.


The size of the box is different than what I posted and for the parameters that I put into winisd I used what ltd02 has posted in a different thread on what he has in his computer. It could be my mistake I'll take a look and see why both are different. I just helped another person with this sub designing a box and both of our numbers were almost exact on winisd when we were modeling it together and exchanging pictures via pm.
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post #15 of 22 Old Yesterday, 11:43 AM
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post #16 of 22 Old Yesterday, 05:35 PM
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OP, were you checking port velocity at "1.6w"? If so, it will be low, but not indicative of potential issues when you crank the power up...
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I have a UM 18 in a box just under 6 cu. ft that is slot ported. The port has been absolutely quiet. Very impressive for a small vented sub. More output than the sealed 4 cu ft. box that was in it's place.
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post #18 of 22 Old Yesterday, 09:26 PM
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post #19 of 22 Old Today, 04:57 AM - Thread Starter
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Quote:
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OP, were you checking port velocity at "1.6w"? If so, it will be low, but not indicative of potential issues when you crank the power up...
I found the source of the descrepancy. I was using winISD standard. Pro gives very different results.

For the exact same project, the SPL is mostly the same below 100hz, but the rear port velocity is very different.

See image.
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post #20 of 22 Old Today, 04:58 AM - Thread Starter
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Just sent you a pm jhgkak
Thank you so much. I was about to waste a ton of time! Going to delete the WinISD standard now!
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post #21 of 22 Old Today, 06:10 AM
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Quote:
Originally Posted by jhgkak View Post
I found the source of the descrepancy. I was using winISD standard. Pro gives very different results.

For the exact same project, the SPL is mostly the same below 100hz, but the rear port velocity is very different.

See image.
Your old version of winISD is showing the velocity in m/s, your new version is showing the *same velocity* but in ft/s. So I don't think you've found the discrepancy yet.
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