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Old 18th April 2013, 11:26 AM   #1
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Default 2 x PR vs Ported

I just purchased a TC Sounds LMS Ultra 5400 and I am just wondering if it is better to buy a couple of PRs or port it...

On the TC Sounds website under enclosures it seems you can achieve the same results either way...

LMS-Ultra 5400 18″ Driver | TC Sounds

Very Large Ported
Size Volume Port Length Port Area Tuning
18″ 8.0ft3 90in 6×4in 15Hz

Very Large Dual VMP
Size Volume Number of VMP’s Moving Mass Tuning
12″ 8.4ft3 2×18in 1650g 15Hz

Last edited by Silent Screamer; 18th April 2013 at 11:32 AM.
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Old 18th April 2013, 01:25 PM   #2
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Looking at their spec sheet for recommended enclosures, their port dimensions vs. tuning are WAY, WAY off. A 3.1 cube box with a 4"x4" port only needs a 10.15" long port for a 30hz tuning. Not the 36.5" they list.

Build any of those designs and you'll end up with something MUCH lower than the supposed tuning and a port that's too small. The one you listed is actually tuned to ~9hz.

Without having it winisd, I would guess around 10 cubes with a 15 hz tune and 60-75 in^2 slot port would work pretty good and end up with a reasonable size. I would personally build from medium-high quality plywood.
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Old 18th April 2013, 01:33 PM   #3
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Thanks turbodawg I will throw the specs into Bass Box Pro on the weekend and see what I come up with. Reading through an old thread comparing the 5100 against the 5400, it seems the 5400 may work ok in a sealed enclosure as well.
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Old 18th April 2013, 02:56 PM   #4
tb46 is offline tb46  United States
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Hi Silent Screamer,

Take a look at data-bass.com: Data-Bass

Regards,
__________________
Oliver
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Old 18th April 2013, 08:35 PM   #5
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Default TC Sounds vs. Data-Bass T/S parameters - LMS Ultra 5400

Quote:
Originally Posted by tb46 View Post
Hi Silent Screamer,

Take a look at data-bass.com: Data-Bass
A lot of questions ?!
Look below

Driver : TC Sounds LMS Ultra 5400 18" DVC Subwoofer (2+2 ohm)
Référence : LMS-Ultra 5400

TC Sounds vs. Data-Bass
Fs ( Hz ) : 20.5
VAS ( L ) : 240.7 / 201.1
Re ( Ohms ) : 3.78
Qms : 7.6 / 14.97
Qes : 0.34 / 0.311
Mms ( g ) : 501.3 / 550.3
Sd ( cm2 ) : --- / 1150 (1194.60*)
Inductance Le ( mH ) : 1.96 / 3.57
Xmax ( mm ) +/- : 33.655

* my reference: in the parts express website look here it says that Sd for passive 18" is about Sd: 194.56 sq. cm. I used this parameter as a reference for the LMS-Ultra 5400.

On another note: from the tcsounds website "" Measured with Praxis (voice coil wired in parallel) "" - don't take this to the letter because it says the same for the passive drivers (VMP Passive Radiator). It's obvious that it shows Re measured in series (nominal 4 Ohm). The same measurements are shown in the Parts Express website.
For the data-bass website it doesn't mention the procedure but notice Re is in series also. This might be (small or not) of consequence in the final design of the speakers (enclosures and it's alignments) based on the data sheets used by each.

LMS-Ultra 5400 18″ Driver | TC Sounds
Data-Bass
TC Sounds VMP 18" Passive Radiator 293-684
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Old 18th April 2013, 09:18 PM   #6
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Also you might want to check out these PR's when your modeling.
18" Passive Radiator | PSI Car Audio

I have used a bunch of PR's on different projects including one of these with a 15" tc sounds 3000 and it turned out amazing. I think its the best PR you can get for the money.
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Old 19th April 2013, 11:51 PM   #7
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I spent a bit of time yesterday modeling up sealed, ported and PR enclosures in Bass Box Pro.
the driver selection tool suggests that this driver is far more suited to a closed enclosure than it is a port one.

but upon making a few bigger BR designs I noticed I was getting far better looking graphs using ported boxes, which makes me think while a driver might be better suited to one cabinet type or another by virtue of the TS parameters, should you really use that box type?
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Old 20th April 2013, 02:50 AM   #8
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You should use whichever cabinet type gives you the response curve and output that you are looking for.

A passive radiator design will have ideally exactly the same response and output as a good BR design. You are trading the cost of the PR for a slightly smaller box (the size of the box that was taken up by the port area is removed), and no port compression or noise.

When designing a PR box, I usually design my ideal BR box first and then just model my PR box after that. As an example in your case. I modeled the BR box I would want if I was using that driver in my home theater, then I model a PR design using the PSI radiator I mentioned above to recreate that box. Winisd calculates with the net square footage of the box, so even though the calculated volume is the same in both, the PR box will be minus the size of the port, which in this case is quite big.

A port that is 24"x3"x84 will get you to roughly 17 m/s air speed at your cutoff frequency for a 5 ft3 box. Some studies recommend staying under 10 m/s if you don't ever want to hear it, though usually anything under 30 is ok with me. Anyways that means your port would add an additional 3.5 cubic feet to your box in port area. If you were ok with 30 m/s vent speed than a vent with the same tuning would be 24"x1.5"x41", which would add another .85 cubic ft to your box size. In either case you can see how going with a PR saves you a considerable amount of box size if you are properly designing for port velocity.

I have attached the boxes that I would personally make with that driver for home theater.

Click the image to open in full size.

The box with the Yellow line is an 8ft3 box as TC sounds recommends with 2 18" PR's. I would only build this if space was literally no factor and you never had to move these again. Pretty much all normal rooms will reinforce the lower frequencies and any eqing will most likely eliminate the advantages of this box.

The box design in grey is a normal 5ft3 ported enclosure with the vent length's that I described above. Remember the vents are in addition to the stated enclosure size.

The box design in magenta is a 5ft3 dual PR design tuned to the FS of the driver which is 20.5hz. You will add about 900 grams of weight to both of the 18' PSI PR's to achieve this tuning. The volume taken up by the PR's is also in addition to the calculated volume so in this case you would want to build a box with 5.26 ft3 internal volume.

Also remember that all of these designs will exceed max excursion at 2000 watts (modeled in graph) very quickly below 20 hz. So you need to have a high pass filter at 15hz or so.

Last edited by sylk; 20th April 2013 at 02:54 AM.
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Old 20th April 2013, 02:58 AM   #9
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Here is the sealed recommended box vs the box I would recommend as described above.

Click the image to open in full size.

The PR box in this case is modeled with a 4th order HPF at 15hz to prevent over excursion. You can see that you would not see any benefit to a sealed box until 16.3hz, and you would be giving up considerable output. Also the response of all of these boxes will be changed drastically by whatever room you put it in. You will gain at least 6db on the low end and sometimes 12db in most rooms depending on size of the room and location of the sub.

Any quest for flat frequency response will need room equalization, and any quest for flat frequency response in more than one location will need room equalization and more than one sub.

Last edited by sylk; 20th April 2013 at 03:01 AM.
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Old 20th April 2013, 03:27 AM   #10
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I was possibly thinking about a 3 SW system as suggested in another thread. The 5400 used in something like this "http://www.data-bass.com/data?page=system&id=8" to do the real grunt work, and the two 5100s used up a little higher. Allowing each driver to work in best comfort zone and creating a blended sub.

Earlier Geddes approach was discussed here Underground Sub using different placement and subs to create a blanket of sound.

Last edited by Silent Screamer; 20th April 2013 at 03:48 AM.
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