Changing my mind - now want to build TC2000 LLT

[Mattk11]

I originally was going to build two subs with Soundsplinter 18's but I am having trouble with box sizes.

I am really limited to size due to clearance behind my screen wall.

I have been doing some reading on this forum and others and see that the 15" TC2000 driver is well suited for LLT design.

I want the best sounding sub I can build with a ~16Hz tune. I figured out that my max box size can be as large as 16" deep (this dimension is fixed and will have a double wall of MDF on the front baffle) x up to 40" wide X up to 40" tall (height is dictated by the fact I want to stack two). These are outside dimensions. This would give me plenty of clearance behind my screen. I have read a couple build threads that suggest box size of 320-350 liters.

Subs will be used 100% for Home Theater. I will build two boxes, both will be powered by a Crown CE4000 wired to 2800w at 4 ohms mono and equalized by an SMS-1.

Please tell me the ideal internal size and ideal port size and length for a ~16 Hz tune.

Thanks
Matt

[Jerm357]

320 liters tuned to 14.5Hz is what most people are building for TC2000 LLT's. Thats 11.3 cubic feet (net)with a 6" port. Straight Length Port requireds a 27.68" and Flare Length Port required 28.68". Port length calculated with Precision Sound Products Port Length Calculator.

http://www.psp-inc.com/

[Mattk11]

Thanks for the link. That is pretty cool, but does it take the driver into account or does it not matter?

TC Sounds suggested to me an 8 cu ft box with 3 - 4 inch ports each 35" long to tune to 16.5Hz. I am curious why they suggest something so different that is typically done here. Everything on here is so big with larger ports. I read the LLT explanation but I am not sure of the difference that TC suggested and the larger box you are suggesting.

I am not sure if I want to tune it all the way down to 14 Hz, I don't think I can hear below 17 anyway.

Thanks
Matt

[bonehead848]

the threshold for hearing is nothing below 20 Hz. But, that is not to say that it doesnt matter, sub 20 sound does a whole lot of awesome shaking.
Going with a larger box gives the sub more room to get to lower tunings, if you dont want to tune that low you can go with a smaller box.

[Mattk11]

I'm following you on the box size, that is why I want to tune to 16-17 Hz, Don't know if I need to go down to 12 or 14.

Being brand new at this, I just don't know how to do it. I have read everything I could find in relation to these drivers, but just can't find exactly the tune I am looking for. That is why I turned here, you guys know what you are doing.

Thanks

[bonehead848]

Changing port length is what changes tune at a given box size. Here is the graph of what your subs response will look like at what jerm suggested and what tc suggested. You can see that you really dont gain much by going with a smaller box and higher tune. It is simply a case of if you want a box that big or smaller, that is really the only advantage of the tc design, smaller box. If you cannot fit the big box behind your screen then go with the 8 cu ft design, otherwise go with the big box.
Port length on bigger box = 29.87 in
Port length on smaller box = 32.66 in

[Mattk11]

Bonehead (I feel bad calling you that), thanks for the cool graphs. I am now thinking 290L (10.25 ft^3)tuned to 16 Hz. Does that graph well and what size port would it require? Thanks

[bonehead848]

that graphs right between the other two and looks good, port without any flares should be 24.53 inches at 6 inch diameter

[SteveCallas]

If you want to tune to 16hz, a 260 effective liter enclosure would work fine. A little larger would be even better, but 260 would cut it. TC's recommendation comes out to ~226 liters, and that's too small in my opinion, you choke the low end too much.

Three 4" diameter ports would provide you with more port area than a single 6", but managaing three long ports with plenty of clearance at each opening becomes very difficult.

[Mattk11]

Steve, thanks for chiming in. I'm just a little confused by your suggetion on a little larger than 260L. I can go a little larger, so what do you recommend for the 16Hz tune. Need interior box size and port size and lenght. You are the guru for these LLT designs so I am very interested in hearing what you suggest.

As you suggest, I would rather do one port than three since it will definitely be easier.

Thanks

[Jerm357]

Have you tried playing with Winisd yet? WinISD is freeware speaker designing software that you can use to model up your speaker in different boxes and see the different effect by changing box size and tune. It also will tell you how long to make the ports for a given tune. This is what most of us are doing to answer your questions. Just follow the directions in the help file on "Entering your own drivers" Heres the jist of it..........

The suggested procedure for entering driver parameters is following (check first that "Auto calculate unknowns" option is checked):

1. Enter Mms and Cms

This gives fs. If either is not available, then enter fs and other parameter.

2. Enter Sd, Bl and Re

Now, you should get all but Qms (and Qts), Vas. Please note that Vas may not match exactly what is specified by manufacturer, because exact value of Vas depends on environmental parameters. See FAQ.

3. Enter Rms or Qms.

Either one will do, although I tend to prefer Qms over Rms, because it can usually be measured in driver measurement procedures.

4. Enter Hc, Hg and Pe.

If Hc or Hg or either is available, then enter Xmax and optionally either Hc or Hg if available.

5. Enter number of voicecoils.

Give it a try and Im sure we can go from there if you have any problems.

http://www.linearteam.dk/default.aspx?pageid=winisdpro

[Mattk11]

Thanks, downloaded it and installed.

I tried entering the parameters you suggested and could not find the following for the TC-2000:

Sd
Re
Rms
Hc
Hg
Pe

The program would not run because I did not have enough information. Anyone know what those values are?

Thanks

[bonehead848]

ive always entered res for re, put that in and you should have enough. Also make sure you have autocalculate unknowns checked

[Mattk11]

I am still getting a parameter error list box popping up. I seem to still be missing info.

[Mattk11]

OK, got the TC2000 driver saved. When I try to open new project, an error window opens and says: "floating point division by zero" I don't get it. I think I am following the directions.

[brucek]

Yeah, entering driver data into WinISD is cumbersome.

For the single coil 4 ohm driver, enter in order as I've listed below, the green values shown in the pic below, and use TAB after each entry to produce auto values (which are in blue).

Make sure the units are correct - click to select units if needed.

Mms, Cms, Re(s), BL, Qms, Xmax, Vas, Le, fLe @1000, I believe Xlim is 41mm for this driver

Save...........


TC Sounds.jpg

brucek

[Mattk11]

Thanks, this might help but.....

My TC2000s are dual 4ohm VCs. They will be wired to 2 ohms per cabinet. 2 cabinets at 4 ohms mono to the amp.

[brucek]

My TC2000s are dual 4ohm VCs.

Then change Re to 1.595 ohms and BL to 12.40474, and voice coils to 2 in parallel.....

brucek

[Blaser]

Matt,

I think you should follow 14 Hz tune, and you won't regret it

[SteveCallas]

If you are planning on building two, I see no reason not to go for the lower tune. 320 effective liters per enclosure is what I would shoot for, with tuning ~14-15hz. Some have had success in finding 6.5" or even 7" diameter sonotube at hardware stores - I'd make an effort to see if you can find some. If not, 6" diameter will work fine.

[Blaser]

Right, you have to trust Steve....he knows what he is saying

[Mattk11]

I'm down with the lower tune. I will try again to run the graph. Thanks for the input.

[bonehead848]

if you cant find the sono, ive had success with 6" pvc from lowes

[Mattk11]

I'm really getting frustrated. I used the values provided here and still get the "zero point" error.

I can't figure out what to do to change it.

Can anyone run this with a dual 4 ohm VC TC-2000 and as suggested: 320 L tuned to 14 - 15 Hz? I want to find out how long to make a 6" port, 7" port and/or 8" port. Then I can make the decision on port width based on what is available locally. I will make the ports flared with a router in the 3/4" plywood or MDF.

Thanks again and I appreciate everyone's patience.

[Ilkka]

320L and 14 Hz:

6" - 29.7", 210 Hz 1st resonance
7" - 40.7", 157 Hz
8" - 53.7", 123 Hz

6" is the maximum you can use.