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Discussion Starter #1 (Edited)
I hope to get some brainstorming from you smarties. Lets get low and loud here...

Just pulled the trigger on 2 Ultras. I would really like to put together the optimal vented system with the drivers, enclosures, and the space I'm putting them in. TC Sounds site shows a couple of different vented enclosure sizes spec'd for the Ultras. 6.4 cubes at 20hz and 8 cubes for 15 hz. My current subs fire to the front and vent to the sides. I would like to vent out the front on the new set. Has anyone built a vented Ultra or at least modeled a set?

Playing with winISD a bit - 7.8 cubes at 16hz is about as nice as I can make it look with my limited experience. I can make it a bit smoother with 10 cubes and a giant port. As far as I can tell, I get the same exact thing plus 3db with 4000w as opposed to 1900. I believe x-max will happen with more than 3500w per driver with 16hz tuning, but I could be wrong.

Here's what I have for LFE:
2 18" LMS Ultra, 2 EP4000, and a Reckhorn B-2 for HPF. The room is 12x22 swiss cheese with doorways, windows, vaulted ceiling. Enclosure has one place to go, under the screen, 7x2x2, 6x2x2 would be best for aesthetics. I am replacing a set that occupied the same space. I am ready to sell the EP4000s and order the fp14000 if that is what I need. I am also wanting to replace the Reckhorn with a more accurate unit with a HPF and EQing. Something from minidsp.com maybe?

Here is a 3D rendering that I created in autoCAD for reference ;)
 

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MikeP. is a master with ported enclosures, I am sure he will chime in. The biggest thing with porting an LMS-U is the port velocity as it can move some serious air.

I looked through the build thread database for TC Sounds but did not find a traditional ported build, only sealed and PR builds: http://www.hometheatershack.com/forums/members-diy-subwoofer-database/24411-tc-sounds.html

You might try e-mailing TC sounds directly and tell them your plans, they can sometime take a few days to respond but they have given me design ideas before based on the equipment I wanted to use.

I can try some models and post them here, I am not the most knowledgeable when it comes to ported though but I have built them in the past.
 

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Now I am realizing why porting he LMS Ultra is so tough.

I have been doing a little modeling and had one saved but it was 10cuft with a 10" port tuned to 18hz With the EP4000 bridged and a 15hz hpf. The rear port air velocity is OK at 19.5 m/s peak at 17hz and cone excursion is fine but the port length is 57.5" long :eek:

So your planning on making a new box? What is the max size you can go? Both subs in a single box or in 2 separate boxes?

I am thinking a slot port would be the way to go but you might be able to squeeze a big round port into a single enclosure for both subs since it will be huge.
 

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Discussion Starter #4
The only constraints are 7x2x2' and can be 1 or 2 boxes. I'd prefer 6x2x2. I will need to rebuild for sure. I'll buy more power if I need to, and sell the ep4000s. I was thinking slot ports too because of size and length.
 

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To add to sub_crazy's questions how low do you want to go?

A 10" port can handle a lot of air so 19m/s is nothing. With proper 1.5" round overs or more the 10" port should be able to easily handle double that. That being said it also shows you could go with a smaller port and there for a smaller port length.

But we will wait for your answers first.
 

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The only constraints are 7x2x2' and can be 1 or 2 boxes. I'd prefer 6x2x2. I will need to rebuild for sure. I'll buy more power if I need to, and sell the ep4000s. I was thinking slot ports too because of size and length.
So your preference is about 18cuft in a single enclosure give or take depending on the bracing and thickness of the walls. About 3cuft more or 21cuft for the 7x2x2 option.

One thing that makes me wonder is if the effect of dual opposed works with ported cabinets the same way it does for sealed? Never really though about that till now, I suppose it would work the same saving you some weight for the cabinet and less bracing.

One thing I wanted to caution about the clone amps is they seem to have a high failure rate. There is a LMS Ultra build here were his new clone smoked and needs parts and another I remember with a faulty clone. I also know of another whose clone popped. I have a friend though who has a pair of clones driving quad LMS Ultra's and his has been trouble free. It seems like a roll of the dice with clone amps, just so you know.
 

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To add to sub_crazy's questions how low do you want to go?

A 10" port can handle a lot of air so 19m/s is nothing. With proper 1.5" round overs or more the 10" port should be able to easily handle double that. That being said it also shows you could go with a smaller port and there for a smaller port length.

But we will wait for your answers first.
So how high is acceptable for air velocity? I always thought you should stay under about 24 or so but it makes a difference how big the round over is?

Good question on how low to go. I wonder if 20cuft for 2 LMS U's is LLT range or do you have to go bigger?
 

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Most will say 24m/s. But it all depends on what is being played, port entry and exit and area of port. SO while we all like to stay at or around 24 some ports are fine playing with more air movement without chuffing. But this is mainly because of huge rounded exits and at least a 60% entry compared to exit. With this in play one can push the port harder. And then if playing just music you can push slightly harder. Its a complicated compromise between flare, resonance and size of port to achieve the best results. 24 is just a rough guideline to stay with but without flares on the ends this number should be closer to 15m/s and then lower depending on variables.

I dont think 10" ports have any concrete testing done on them but if 6" ports with very large flare exits and entries can handle 35m/s then magic can happen with a 10" port. But when I say very large I am talking about 3-4" flared ends. This is just a guesstimate but when going from a straight pipe to a rounded flare you are increasing the air flow by as much as 40% before chuffing. Then going from say a 13mm to a 25mm flare you increased it again 40%. But it does not go on and on at this rate of increase. SO for me flare is just as important as diameter to get the most out of the size you want to use.

But as we said I will wait to see what the OP wants to do for tuning. I was going to buy a clone myself but the failures have scared me away. So I hope this clone amp works fine. And dont forget there is also the PR option.
 

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Thanks for the info, you have made me more wise and I appreciate that :TT
 

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Discussion Starter #10 (Edited)
I would like to tune as low as I can to get the most out of the drivers while keeping them safe with a hpf and the perfect amount if power. There is a balancing act there. My round over bit is 1 1/4, but I could make it with some woodworking magic if I use a slot port. I have never understood port speed either. Always learning something new here!

88 x 25 x 21 max outside dimensions. Finally home after a 48 hour shift to take some measurements.
 

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This is going to be a fun build to watch! Subscribed! It seems like what you hit on with seeing only sealed and PR builds is the port airspeed. Check out this build. From what I remember, the only way he could deal with these beasts is by using PRs instead of humongous long ports.
 

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One thing that makes me wonder is if the effect of dual opposed works with ported cabinets the same way it does for sealed?
Are you talking about rocking or walking? No matter what alignment you are looking at, a mass moving extremely fast with a lot of force will create a moment or torque, which causes rocking. Opposed will always be a great idea to cancel those moments created by that moving mass, and will allow more energy to be made into air movement instead of moving a cabinet back and forth.
 

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Discussion Starter #13
I think that when loaded with drivers it will be close to 400 pounds, so maybe it won't be a'rockin?
 

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20 cf tuned to 13 Hz gets you, well, ridiculously loud (125 - 130 db) with 6,000 w (just past xmax).

The issue I see with a tuning this low is that these drivers need a big port and that gives you a low first port resonance. I modeled a 22.5" x 4" slot port. That gives you an FPR of 109 Hz and max port speeds up around 47 f/s. That seems awfully high to me for air velocity.

I'm curious to know from those more experienced if a slot port of this size can handle those air velocities.
 

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Discussion Starter #15
I think the combo of a large slot port and a huge flare is the ticket here, as Chrapladm pointed out the benefits of each and using both. I can build an mdf flare by cutting strips on one side and bending it. I have never done it, but will try. After I make a good pattern, I think I could make it on all 4 edges of the slot.

Some guys in another discussion mention using a PR, but that adds another $600-1200 for 4 of them.
 

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I will be really interested to see how you do the flaring on this! I can guarantee it's going to be a challenge, especially if you plan to flare all four sides of the port exit. It would be considerably easier to just do the top and bottom of the port exit, but if you can do all four sides, that will be a mean-looking port!

I guess one thought I had was doing all four sides and then coping where the corners meet. Then it would just be a challenge to seal the joints.
 

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20 cf tuned to 13 Hz gets you, well, ridiculously loud (125 - 130 db) with 6,000 w (just past xmax).

The issue I see with a tuning this low is that these drivers need a big port and that gives you a low first port resonance. I modeled a 22.5" x 4" slot port. That gives you an FPR of 109 Hz and max port speeds up around 47 f/s. That seems awfully high to me for air velocity.

I'm curious to know from those more experienced if a slot port of this size can handle those air velocities.
Couple issues,

6000W is above the spec'd power handling for the drivers. With the OP's history, I wouldn't go over 4000W. This will only reduce output by 1-2 dB.

47 f/s is only around 14 m/s and is completely acceptable. Are you sure the model is reporting feet/sec?

port resonance is a little too low in my opinion but I'm not sure how much real world effect it is gonna have on the resulting frequency response of the system. It can probably be eq'd out...
 

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My bad. I meant to type m/s.

I modeled two drivers in the enclosure so that is 6,000w total, or does winisd apply the entered power to each driver? I went to the TC sounds site, but could not find a number for power handling. They have two entries on their specs page, but both contain an x.

It seems that TC sounds does not think this driver should be tuned that low, and looking at the first port resonance and port air velocity, I can see why that might be.

I threw my modeling out there for thought. I'm still curious to hear from people with more experience than I what an appropriate tuning would be.

Edit:

I wouldn't go over 4000W. This will only reduce output by 1-2 dB.
Unless the room is very large, with two drivers, the OP may never get to 6,000 watts. I was just trying to model worst case.
 

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Discussion Starter #19
How about this:
Downside is the port speed is 35 m/s, but with 3x16x65" port with 3" flares
8 cubes
15hz
1900w
 

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Hmmm, when I plug your numbers into WINisd, I get a longer port. Looking at the TC sounds site, I wonder if I am working off old driver specs. My file lists 38mm xmax, the TC Sound site lists it at 33.

I'll create a new driver file using the TC Sound specs and try again.

Edit:
New file created. It did not make any difference to the port length however...

When I entered the port size as 16 x 3 it autoadjusts to 16 x 3.26 with a 71" port. If I adjust the port again to 16 x 3 it shortens the port to 65.8" That works.

So, I actually like 9 cubes tuned to 15 hz with that port size. That gives you a 57.8" port with a first port resonance of 117 Hz and a max port velocity of 34 m/s @ 2,000w. This is for a single driver right?
 
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