Finally Got the Tempests, Please Help Me Remember What To Do Next!

[Gregg Loewen]

I just received 3 Tempest drivers. I will be using 2 of them to make a dual sonotube, and the 3rd for making a separate tube (much later, ie : January) for my Wife's HT.

Please help me again with the specs, etc.

As a recap:

Very large room 30-34x34 feet, back is open into the second floor so the room isnt sealed. The ceiling is 8 feet.

I currently have dual 12 shiva sonotube that is tuned to 22-23. I want to keep this in my system for now, unless the dual Tempest is able to shake the house by itself. This tube occasionally bottoms out (?).

I will be driving both tubes with a Peavy amp that is stable at 2 ohms with 1200 watts per channel.

I will take Thomas' recommendation and go for a tune of 16. 1 10 inch port diameter, 30 inch diameter tube. Length of port, length of tube?

I can use either 1 or 2 10" ports but would prefer 1 for simplicity's sake. I would like to have a similar design to my current tube which has 2 layers or Mdf? boards internally top and bottom, and one layer of pine board on the top and bottom (not inside the tube).

I would like to change my design slightly. I would like to have the woofers mounted to tne MDF boards and the pine caps mounted around the woofer, so when you look at the caps the speakers will looked recessed. (did that make sense).

I also like Patrick's design where you add legs with wheels so it will be somewhat moveable.

Am I missing any needed / critical info?

Thanks!!

Gregg

[Patrick Sun]

If no one steps in by the time I get home today, I'll see what I whip up for sonotube and port length for you.




PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

[ThomasW]

Gregg

Give me sometime to find the file and I'll post the info. I'm running on a backup HD currently and my box models haven't been moved to this HD




theAudioWorx
Klone-Audio

[Gregg Loewen]

Thanks guys!

Im trying to use WinISD but not sure about things. WinISD doesnt take into account the volume displacement of the drivers and the port/ ports does it?

Gregg

[ThomasW]

Gregg

The only program I know of that compensates for the component displacement is BassBox Pro.

Could you/do you have any interest in doing 2 separate tubes? Jeremy's "Twin towers" comes to mind. That might be a litte more reasonable to live with.




theAudioWorx
Klone-Audio

[Gregg Loewen]

Thomas, I read Jeremy's post about wanting to make a dual with a 24" tube, then talked into 2 tubes. I really dont have a shortage of space and can fit a 30" diameter tube and my current 24" dual shiva beside it in a corner. Then put my left main in front of the 2. I dont think I will have room for all 3.

Do I have room for about a 72"(internal height) x 30" tube? If I dont have a port on the top (only a woofer), how much room do I need between the woofer and the ceiling. My ceiling is made of drop tiles so I can move it to move the tube to an upright position (can therefore be pretty snug, unless a certain amount of room is needed from the the speaker to the ceiling).

Gregg

[ThomasW]

Ok, I don't think we "talked" Jeremy into anything he didn't want
But....

I realize the space is large, but I think the twin Shiva tube is going to be superfluous.

To double check the performance, I ran the "sim" on both BassBox Pro and the full version of LspCAD V4.10.

They are in close agreement. For a tube with a "net" (having subtracted the woofers and port displacement) internal volume of 25 cu ft, use one 12" diameter port 38.5" long. Fill the enclosure 10-20% full with damping material

For the gross volume, simply calculate the volume displaced by the port and 2 drivers. Add that to the net volume, and calculate the height of the tube from there, don't forget compensate the height for the internal portion of the endcaps.

I'd suggest standing in the front yard when you fire this "beast" up for the first time :B

Hope this helps
Thomas




theAudioWorx
Klone-Audio

[Jeremy Santos]

I am very happy with my subs, maybe to happy!! I actually don't want to upgrade a part of my system anymore. Woohooo!!!!! Thanks Thomas. Gregg, listen to what Thomas has to say. You won't regret it.




Jeremy Santos

My Software
Santos Theater

Play It Loud, Play It Clean!!!!!

[Patrick Sun]

GreggL, if you go with ThomasW's design, you're looking at an internal height of about 68", and then add in another 3.5" of endcap thickness for 2 sets of endcap for a final length of 71.5" for a 30" wide piece of sonotube.

But bear in mind, if you do use a 12" port, you'll have roughly 1"-1.5" from the edges of the endcap since the port and Tempest (15") driver take up 27" out of 30" of endcap diameter. Maybe some other porting options need to be explored?




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[ThomasW]

Pat

I looked at this when doing the model. Changing to a single 10" port, isn't all that great for 2-15"s tuned real low. And multiple 10"s get too long. I guess he could somehow create a DIY flared port.

Gee Gregg, can you get 36" tube into the room? :B




theAudioWorx
Klone-Audio

[Gregg Loewen]

Thomas, Pat: Thanks!

So,

71.5 " x 30 " Sonotube
1 12" x 38.5 inch port
10-20 % fill
2 layers of MDF for each cap. These will be internally mounted, then a pine out cap will be be on the external surface.


71.5 " plus legs (6" ?) plus 1.75" for pine caps Total height of 79.75"

My ceiling height in the corner is only 84". Is 5"-6" of clearance (top speaker to ceiling tile) enough? (The port would go on the bottom)

Second question: As Pat mentioned, 15" speaker and 12 " port only leaves 3 inches of room on each cap. Will I need any internal bracing?

Third question the port will butt against the pine board thereby adding 3/4 inch to the port length, so do I subtract 3/4 " from Thomas' calculated port length to account for this?

Thanks again!!

Gregg

[Patrick Sun]

Thomas,

Would going with 22 ft^3, one 10" port 44.3" long, F3 around 21.5Hz be too much of a compromise to get just a little more endcap material on the bottom?




PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

[ThomasW]

Gregg

Yes, subtract the thickness of the pine or any extension added by the endcaps from the length of the port.

I'd certainly brace these endcaps. A couple of 2X2's from top to bottom should limit the flexing.

The outside diameter of the Tempest is probably closer to 15.25". So there is minimal room for the 12" ports. There is no reason the port opening can't literally be touching the edge of the woofer frame. If you do this glue a 1"X2" on edge underneath the endcap in the space between the opening for the port and opening for the Tempest. This will stiffen that area, and provide added strength.

If height is a problem use 4" legs. Or we can drop the tube size down a few cu ft.

Pat

It's Gregg's call if he wants to tune the box higher. He can certainly go with a smaller port and keep the low tuning. I just designed an optimal model with the biggest practical port.

I'll run some other port sizes for the same tuning, and put the info in this post later this evening




theAudioWorx
Klone-Audio

[Gregg Loewen]

Thomas,

Is height a problem? How close can I get to my ceiling without causing the ceiling tiles to break apart ?

[Lexman]

Good thread guys. Greg, that's some serious bass son!

Lex

[ThomasW]

Gregg


They won't be enough pressure for the tiles to break, but the metal support frame might rattle a lot.

Here are some other options for 16Hz tuning.

1)22 cu ft "net", 10" diameter port 28.3" long
2)20 cu ft "net", 10" port 32.1" long

There is really very little difference in the performance of the 3 designs. Above 20Hz they are identical, below 20Hz the larger boxes give some advantage but not all that much. Also the room and it's characteristics will have a bigger impact than the difference between the 25 cu ft and the 20 cu ft tube.

So from a practical standpoint I say go with the 20 cu ft tube. It will be shorter, therefore easier to move around/build/etc.

Here are some more numbers.

If the tuning is raised to 18Hz for a 20 cu ft "net" tube

1)12" port, 36" long
2)10" port, 23.8" long

The 18Hz tuning, with the 20 cu ft tube, and the 10" port, might be the best "compromise", between performance and practicality.

When you get the port material, let me know the actual ID (inside diameter). If it's slightly bigger or smaller, I'll adjust the port length for you.

But it's your decision




theAudioWorx
Klone-Audio

[Gregg Loewen]

Thanks!!

So its:

1 10 inch port 23.8" long

for a 20 cf tube. this will compromise and give a tune of 18hz.

Considering 30" diameter tube, what will be the total length? (2 double layered end caps, with exterior pine caps)

I will do a couple of 2x2s inside to help brace? where should I mount them? ON the sides, or towards the center?

Should I still be using the same amount of filling? (10-20%). And how much does this work out to? Measured in pounds / ounces?? Im assuming the fill is lining the tube?

Thanks again!

Gregg

[ThomasW]

Gregg

The 2x2's should be placed toward the center of the endcaps. This is where the flexing will occur.

The damping material is used around the walls of the tube. Go with 20% since the tube size has been decreased. If the tube size is 20 cu ft then you want 4 cu ft of damping, equally layered inside the tube for a 20% "fill". Do the math for the volume (not weight) based the damping material you buy, and how thick it is.

Use Pat's method to arrive at the proper height. The new port displaces a smaller volume so don't forget to compensate for that.




theAudioWorx
Klone-Audio

[Brian Steeves]

Hi,

I made a single tempest sub recently. It is 10.5ft3 tuned to 18hz. I love it! This plan you guys are concocting is pretty much the same as mine only one more driver and double the volume! Wow, I would love to hear/FEEL the bass that's gonna be comming from that thing!




She said,"you're gonna put that thing WHERE!"

[Patrick Sun]

My method to find the height of the sonotube is to use an Excel spreadsheet that allows me to change the parameters, and then I just iterate until I get the length by looking at the change in volume I get as I lower or raise the value of the length of the tube.

Gregg, click here to get the spreadsheet I used to calculate the length of tube. (BTW, anyone can download and use that spreadsheet, just change the numbers in green and red).

The Red number on the spreadsheet is the internal length number (you'll have to put in the number and see what the final volume is and iterate until you get the right length), and the blue number (down near the end of the spreadsheet is the final length number.

When I put in the new numbers, I got 56" of final length (+/- 0.25") depending on whether you added vertical bracing with 2x2's.

That is going to be one fatboy sub!




PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

[Gregg Loewen]

Pat, Thomas, BIG THANKS!!

One more look:

sonotube: 30" x 56.5" total length
port: 10" x 23.8 inches
2 2x2 braces towards the middle of the caps
20% fill by volume, approximately 4 cf, attached to sides
MDF board x 2 for each cap. Each speaker will be attached to the board. The MDF will be placed internally. Over the boards I will be capping with Pine board. I will substract the thickness of the pineboard from the length of the port.

Am I forgetting anything??

If no changes / suggestions, I will be starting in about 1 week.

I could make the tube a little taller if this will increase preformance?? Maybe 66 inches??

Again mucho thanks!!

Gregg

[ThomasW]

Gregg,

If you make it taller (add more internal volume)then the port length must be changed.

Build it any size you want, and I'll calculate the port.

But as per my above post. There is almost no difference in "real world" performance between the 20 & 25 cu ft subs. There is a tiny difference below 20Hz, and that's it.

Also if you want to see the difference in port sizes for a given "net" volume go here,

http://www.wssh.net/~wattsup/audio/

Scroll down to the gray box that says "Port Designer". Simply enter the info and push the button. It's "guick and dirty", but that's all you'd need, now that the rest of the sub has been modeled.

Other than that, it looks like you're good to go




theAudioWorx
Klone-Audio

[Gregg Loewen]

Thomas,

Since there is no real difference/benefit with increasing the volume any further I will keep with the numbers you and Pat have provided me. Thank you both SO MUCH! I will definitely post credit to you (and HTG) and Pat on any web pages I create showing my new toy.

Thanks again!!

Gregg

[Gregg Loewen]

Hi guys!!

I finally got my router and made a new cap for my current dual shiva, then went on to make caps for the dual Tempest. I figure cut the caps at 30.25 " diameter just in case the tube is a little bigger. Anyways, to make a long story short, the tube ended up being 31" diameter. Will I have to make any changes to my port length, given the new diameter?

Thanks in advance (and continuously).

Now I have to drive back to Home Depot for more MDF.

Gregg

[ThomasW]

Gregg

That's a bummer indeed

There's really a 5-10% "fudge factor" in sub design/specs so there shouldn't be a significant problem.

When you're finally done and ready for the port let me know. I'll recalculate an optimal port for the volume you end up with




theAudioWorx
Klone-Audio

[Andrew Pratt]

fudge factors are our friend Gregg having listened to Jeremy's two twins you're going to be amazed at the bass you're going to get from this monster

[Gregg Loewen]

Hi guys, one last time. Thanks to Andrew for talking me through the bracing stuff. It wont be a problem now.

I think I really want to go with a 16 tune. This will make some sacrifice on output (correct?). But I really dont want any farting, and SWTPM is my favorite demo flick

So one last time:

The tube is actually 31 " diameter. It is currently 66" in length.

There will be 3" of internal end caps and 2 2x2 braces (actually 1.5x1.5).

The port internal diameter is exactly 10", the OD is 10.75". The external cap will add 3/4" to the length of the port.

I want make a 20 cf tube correct? So my internal tube length will be ______ and the total port length will be ______from which I will subtract 3/4 inches to compensate for the pine cap.

Thanks (one last time)

You guys have been great. Ill try to have some pictures up by Friday.

Gregg

[Patrick Sun]

Gregg, according to my calculations, you need a 54" length of sonotube (51" of internal height). You also need 32.5" (really need a 33.2" long port, but .75" of it gets added in on the 3rd endcap layer) long port that's got a Inner Diameter of 10".

With a tune of 16Hz, your F3 looks to be around 19.82Hz. Enjoy!




PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

[Gregg Loewen]

HI guys!!

Any chance of putting this in your archieves??

thanks

Gregg

[Lexman]

Gregg, we don't currently have an archive area. That is something I would like to have, but so far, I haven't been able to convince Mats of it. Maybe someday, I will refresh Mats memory about this need...

Thanks,
Lex