2 18" LLT Sonotubes: Preliminary Planning

I have decided to go DIY and build two LLT sonotubes powered with 18" drivers. Now, some of you may recall about a month ago I was in the commercial sub forum asking if two SVS PB-13Us would generate useful infrasonics in my room. And in that thread, I was staunchly against DIY due to cost.

So what changed?

I learned that the 155lb PB-13Us are too heavy to ship to an APO. (About 85lbs over the 70lb USPS limit - and that is before packaging!) Now, I can locally source the PB-13U. However, US pricing is $1,799. German pricing is $2338, VAT tax excluded (I can use a VAT form to not pay the tax) After taking out the $99 shipping cost, that's $440.80 more per sub, $881.60 total.

I won't be ready to begin the build until early 2012, so I have lots of time to plan and make sure I get everything as right as I can make it.

Important considerations:
I am in the US Air Force, currently stationed in Germany. Therefore...

A) Any amplifier I get MUST be dual voltage (110/220V 50/60Hz - so I can use it when I move back to the states)
B) Anything I order from the US MUST have a shipped weight under 70lbs. (USPS will not ship anything over 70lbs, and as far as international FedEx... )

So, here are my preliminary thoughts...

SoundSplinter RL-P18 or Maelstrom X 18 (neither currently available but hopefully by 2012...)
Power: 2x Crown XLS1500, each bridged
Box: Sonotube (or whatever Sonotube equivalent I can acquire in Germany)
Volume: 650L
Port: 8" port, 30/35" (MaelX/SS RL-P18) long, 50mm flare
Tune: 12/12.8Hz (MaelX/SS RL-P18)
Highpass: Signal Chain
Room: 2000cu/ft sealed
Processor: UPA-1 or Yamaha RX-V1900 (both dual voltage)
Use: 95% movies, 4.95% music, .05% "Bass I Love You"

Note: The currently available Fi Q18 was recommended to me. However, I have modeled, and rejected this driver as it has a whopping 10db swing between 17Hz and 80Hz. By comparison, the MalX swings 4db, and the RL-P18 swings 5db.

So, before we start literally talking about nuts and bolts (hurricane, T, woohoo!), how is my planned equipment looking so far?

I understand that an LLT does not require a high pass. Of course, when I model, I see excursion going way past the redline. I know that the signal chain is going to have a rolloff starting somewhere around 10Hz, but I like warm fuzzy feelings. As such, which highpass filter can I insert into the model (not into the finished product, just the WinISD model) which would give me an idea of how my signal chain will attenuate the single digit realm?

Finally, I must confess I originally posted this over at HTS, mainly because they have the "LLT Explained" thread by SteveCallas. But since I see that Steve is also around on this site, and since the population over there seems a bit sparse, I returned home. (I guess I'm spoiled by the fast paced AVS lifestyle) Please forgive me for my infidelity!

Okay, here are my models, available to be nit-piced, scrutinized, and adjusted!

Note: Signal set to give 115db (reference) at 30Hz. (room gain should start kicking in around there) When taking into consideration I will be using 2 subs, this brings the number to 118-121db. Figuring in seating distance, and the db loss incurred in distance doubling, I figure this level will get me at least 115db at the seats. Can the subs play louder? Sure. But I don't see any reason in going past reference.






Summary of questions:
1) Should I instead go for dual Crown XTi 1000s? They will give me 100W less, but they have EQ built in. I may need this, as the BFD does not come in dual voltage models.
2) Speaking of the XTi1000s, I read the thread where they were thoroughly crucified back in 2008, and also read in that thread that Crown was going to work towards fixing the issue. Was it fixed (or was it an issue in the first place?)
3) Which high-pass filter should I model to replicate the low frequency rolloff of my signal chain? Note I won't include an actual filter in the final design, as I understand the signal chain should take care of that for me.
4) Anything obviously wrong with my design?

I ran the huge enclosures past my wife, and she is fine with it. She is awesome! Of course, helps that these are going into a theater room, and not the living room.

For the rolloff, I would like them to pass the War of the Worlds test at reference. I don't have the movie, but I've seen it (not on a huge system, though) Don't like it, so probably won't get it. But if I ever happen to play another movie at reference for demo purposes, and it has a similar infrasonic peak, it would be nice to know I can do it without having to worry about my sonotubes hitting the ceiling...

And yeah, I would go with the Behringers... if they were dual voltage.

Edit: Scott, I ran across your build thread during my research, so in a way, you helped turn me to the LLT side!

Wow, I spent at least an hour and a half researching as a result of your post!

Can you post the parameters, please? I am having a discrepancy between the ISD file from HTS and the T/S specs from FiCarAudio.

From Fi's website:

DUAL 2

Fs: 32.1 Hz
Re: 1.4 Ohms/coil
Qms: 9.37
Qes: .48
Qts: .46
Mms: 347g
Cms: 0.73mm/N
Sd: 1210cm^2
Vas: 149.7 l
Spl: 91.9dB 1W/1m
Bl: 19.65 N/A
Xmax: 28mm
Rms: 1000W

When I try to manually enter, I get a problem right from the start. I enter Mms at 347g, and CMS at .73mm/N, and get an Fs of 10Hz. After playing with it for a while, I figured out the issue. Their CMS value should be .073mm/N, not .73mm/N.

The difference between Fi's T/S specs and the ones from HTS is that the HTS file includes an Le value of 4mH. The Fi specs do not give the 4mH figure. The difference that including 4mH makes is not insignificant...



Green: FiQ18 w/o Le value
Red: FiQ18 with Le value of 4mH
Gray: MaelstromX (with 4mH Le value)

That one value means a difference of 112-119db (7db) from 20-80Hz, and 112-122db (10db) from 20-80Hz. The MaelX and SP RL-P18 have about a 4db swing in that range.

I would like to use the Fi Q18 if it could be tamed a bit. What I really like about it is the excursion below 10Hz doesn't go through the roof like the others:


Green/Red: FiQ18
Gray: MaelX
Blue: RL-P18

If that is truly accurate, I could feed them reference levels with WOTW with a truly flat signal chain, and not hit the 40mm Xmech (if that is the correct Xmech as I have read elsewhere)

I suppose I could PEQ out that hump, but doesn't a lot of EQ add undesireable side effects?

For those of you astute observers, you'll notice that for the FiQ18 chart I posted in this post, I reduced the box volume to 480l, and and tuned them to 14Hz. I did this to try to tame the big huge knee the Q18s have at tuning frequency. As you can see, port resonance is still above 190Hz, so I should be good. And a smaller volume also brought down the port velocity a bit. What negative consequences might I see by slashing 170 liters from the volume? (I did verify the port would still fit in the shorter enclosure)

Thanks!

I did a quick model of the IXL-18. 650L tuned to 14hz, 8" port. Turned up the power to 900W to get my 115db reference. This driver provided the flattest response I have seen so far with this configuration! However, when I checked the cone excursion...



Dang, guess I can't have my cake and eat it too. So, I backed down the wattage, and found that with this tune, it hits Xmax at 570 watts. Flipping back to the SPL screen, I find it gives me about 113db with that input.

So at best, two of these at that level will give me 119db, assuming a 6db gain for having two. But figuring in a 6db loss for actual seating distance, I'm back to 113. So if I calibrate these to reference, I'd be fine 95% of the time. But if I ever turn my system to 0 and forget to turn down the subs by 2db... I may end up looking for new drivers. I could calibrate for 73db, making reference 113db, but then I wouldn't be able to say my system is a "reference" system. I really want this to be the last system I ever buy, and as long as I can make reference, there will be no reason to want to upgrade.

Checking around, I found the Xmech for these is 30mm. Thanks for the referral, but I think I'll stick with the MalX or RL-P18, maybe the Q18 if we can get it's frequency response resolved.

Looks like I need to re-focus the thread here...

Here is my current status in terms of having my main questions answered.

1) Should I instead go for dual Crown XTi 1000s?

Current answer: Yes, as I will need the PEQ which is built in. Behringer makes great products, but they are not dual voltage. The XTi is.

2) Speaking of the XTi1000s, have they been fixed/have they always been good?

Currently unanswered... Can anybody confirm that they are now fixed, and work well as a subwoofer amp? Anybody out there using the 1000?

3) Which high-pass filter should I model to replicate the low frequency rolloff of my signal chain? Note I won't include an actual filter in the final design, as I understand the signal chain should take care of that for me.

Currently unanswered... I don't need recommendations on high pass filters as I do not plan to use one. I just need to know what type of filter I should insert into the WinISD model to replicate the average low frequency rolloff associated with the signal chain.

4) Anything obviously wrong with my design?
Current answer: Looks like my designs are good for the SoundSplinter RL-P18 and Maelstrom X. I want to stick with these so that I have the extra headroom. That way they won't be as stressed, and should ideally last forever. So unless somebody can point me towards a similar performing driver, I will stick with these. If they still aren't available by early 2012, I will revisit and explore other options.

Fi Q18: Rejected unless the modeling discrepancy can be explained/resolved.
Mach 5 Audio IXL-18: Rejected - no headroom.
All Behringer products: Rejected - not dual voltage.

If any of you haven't read it yet, almost everything I learned about LLT I learned from the "LLT Explained" article written by SteveCallas. It's an incredibly thoughtful and informative article, and it convinced me to go LLT instead of sealed. LLT Explained

Okay, I tried modeling that, and it does help. (1st order HP at 7Hz)


Red: FiQ18 unfiltered
Green: FiQ18 filtered
Blue: SoundSplinter RL-P18 filtered
Gray: Maelstrom X 18 filtered

I have also heard a 1st order highpass at 10Hz is indicative of rolloff. From the LLT explained article, it appears that many amps start to roll off at 10Hz. So I also tried a 1st order at 10Hz.


Red: FiQ18 unfiltered
Green: FiQ18 filtered
Blue: SoundSplinter RL-P18 filtered
Gray: Maelstrom X 18 filtered

Gives me a warm fuzzy. But I think I'm probably just going to have to rent War of the Worlds, and loop the torture scene, starting at perhaps -15db, and turning it up one notch each pass, all the way to 0. That way if something starts to bottom, it will be just starting to bottom. I think I recall reading that the FiQ18 has an Xmech of 40mm. That's quite a lot of wiggle room!

Okay, you got me. I tried modeling it, and ended up using two filters. The red line is before filtering, the green is after.


Red: FiQ18 unfiltered
Green: FiQ18 filtered
Blue: SoundSplinter RL-P18
Gray: Maelstrom X 18

Also, I lowered the tuning frequency to 12Hz, and increased the box volume back to 650l. I did this because I noticed it was about 9db lower than the others in the single digits. Now it's keeping up with the RL-P18, but the MaelX still has a good 3-4db on it. (and it's also very close to it's 40mm Xmech) Anyhow, my only gripe (small one) is that the Q18 has that 2db knee at tuning. Yeah, it's only 2db...

I checked the parameters against those listed at the FiCarAudio site. There are two differences between the HTS file and the Fi website. First, the website has Cms at .73mm/N. HTS has it at .073. I believe Fi's website is in error, because inputting a Cms of .73 results in a Fr of 10Hz, not the 32.1Hz listed by Fi. The reasl difference is that the HTS file includes the Le value, and places it at 4mH. If you add that value into your WinISD T/S file, you will get that huge bump at 80Hz. I think the reason the Q18 performs in this manner is because it's Fr is 31Hz. The MaelX and RL-P18 have a Fr of 17Hz and 20Hz respectively. And indeed, if I decrease box volume and tune for 27Hz, the frequency response flattens out considerably, and SPL goes up considerably. So this would indicate to me that the Q18 was designed more for music (down to 30Hz in most cases), and not home theater (single digit content).

On a sidenote, I checked the MaelX and RL-P18 parameter files, and they both have the LE values included.

I did look through their page, and noticed some empty sections. I'll be sure to keep an eye on their site and see what they have to offer in th future.

Wow, I've never seen that before! If I end up using the UMC-1, I will be using a balanced XLR, so looks like the balanced version should work. (I wish they had proper balanced jacks on it, though) And it works wit REW! So I could use two XLS1500s in bridge, and a MiniDSP. Still, it would be more than using two XTi 1000s, and the 1000s probably have a little more of an advanced DSP engine. But as you said, nobody can confirm a fix. Although, some said it wasn't broke to begin with, and it was the testing methodology at fault... More research is called for.

Don't get me started on German standards... too late!

1) German outlets stink. At least the ones in my house do. Half of them were not grounded, or had loose grounds. And they're pressed into the stucco wall, and held in by a couple screws that clamp down on a claw on either side to (ideally) hold it in. Very hard to remove, very hard to replace, very hard to work with. Oh, and German code doesn't even require ground wires. Not to mention the fact that the plugs aren't keyed, so if you have equipment that cares about polarization, you better get a polarity checker before you blow the power supply in your Klipsch RSW-12D by plugging it into a transformer with reversed polarity[raises hand]. I'll take a US outlet any day of the week and twice on Sunday.

2) The ceiling in our theater room bothers me. It has what appears to be some sort of toungue and groove wood paneling (see below) In the front left corner, white powder falls from the ceiling when we walk on the floor above it. I'm actually a bit concerned about what a couple 18s will do to this house. And also,if you look closely at the picture, it appears that the front treatments are crooked. But it's not the treatments. It's actually the ceiling that's crooked! Floors all through the house are like that. Of course, this house is probably easily 100 years old. I don't mind living in it as it is quite sizeable, and has a room I can use as a dedicated theater. But I wouldn't in my wildest dreams ever consider buying it.



3) BMW? Have one. An older one. The mechanics call them "BMTroubleus".

Once I get back to the states, we're buying a house, ideally with an unfinished basement. Once that happens, I will over-engineer a theater room. I plan to make it a room within a room, double offset 5/8" drywall... but that's a thread I'll start several years from now.

/rant

I've been keeping an eye on port resonance in WinISD, and ensuring that they are above 190Hz, per the LLT explained article.

Definitely sounds like the MaelX will be back before SoundSplinter. All Kevin has to do is find a new build house. But SoundSplinter has all their money sunk into one buildhouse which has gone bankrupt, and may have the next batch ready by late summer... Peronally, I don't mind spending extra for the MaelX. In my mind, (barring any further QC issues) their higher power handling means I won't be driving them as hard as the other drivers (relatively speaking). So I would expect them to last longer, if not indefinitely.

Phew, real progress has been made here, folks! Thank you for all our input so far, it is greatly appreciated! So, to update:

1) Dual Crown XLS1500s and Mini DSP. The XLS1500s give me 3db of headroom with all but the MaelX. (maybe 2db headroom there). And the DSP can simply be wired to a 12V adapter.

2) XTis are most likely out. In more ways than one, possibly. On the PartsExpress page, the XTi 4000 and 5000 show as "This part is no longer available". Are they on their way out?

3) Given a HP model of 1st order at 7Hz, looks okay, 1st order at 10Hz, even better. But looks like I'll just have to rent WOTW and loop the scene, turning the volume up in 1db incraments until the drivers sound like they are in distress, or I get to reference. I'll probably do this with the mains and surrounds off.

4) Things are looking good. Probably in the next day or so, I'll post some "SonoSub" design mock-ups, and we can start literally talking about nuts and bolts. And drills. And grills. And roundover bits. And more!

Ah, now "How to Train your Dragon" I have! Unfortunately, I haven't even been able to watch it with my Klipsch... but I have seen it with my Logitec PC sub. Still, I KNOW there are scenes in that movie that had some powerful bass which I have yet to experience...

Can't wait to get home so I can start my Klipsch Sonosub build. While I won't be able to start with the 18s until next year, I'm going to take my Klipsch driver (the one from the sub with the blown power supply) and make a DIY sonotube out of it. That will be my "practice round" before I build the "real deal".

Wow, a reply from Mr. LLT himself!


It's mainly for the peace of mind that if I can run WOTW at reference and not bottom, then I don't ever have to worry about what might happen if I do a reference level demo for somebody. I figure if it can handle WOTW, it can handle anything... until somebody makes an even hotter ULFE mix...


Oh, rest assured, the bookshelves pictured above (Primus 150s) will not be in the final design. I plan to buy either a pair of classic Klipsch RF-7s or RF-83s (both still available new in Germany) and associated speakers. So they should have no problem keeping up with reference. For power, Emotiva XPA-5, and maybe even am XPA-2 down the road. Or a second IXL1500...


About 2000 cubic feet, and both doors can be closed. Once we move back to the states and build my own room, depends on the space I have to work with. But it will be a completely enclosed HT room. That's part of the reason I'm doing 2 18s... most likely extreme overkill for my current room, but I have room to grow.[/quote]

For the Q18s, I haven't discounted them. I'll see how the MaelX looks once it's time to start my build. If it's still not available by then, then I probably will do the Q18.

Well, looks like the design is good! I'm working on finding German sources for tubes. I found one store that sells tubes of all sizes, and can make custom sizes. I'm working on getting a quote for an 800mm ID, 9mm thick tube. (standard thickness is 5mm, but they do custom all the way up to 25mm thick) It looks like good stuff... laminated paper tube, and no films or oils like a lot of Sonotubes, so wood glue should work excellent. But it is 44 Euros per meter. Hopefully they take VAT forms.

http://www.modulor.de/shop/oxid.php/.../listtype/list

I did find actual concrete tube... but it's about 100 Euros per meter!

Thanks!

Actually, I tuned it to 12Hz...

One thing I didn't mention is that I will be doing all sorts of acoustic treatments. As you can see from my theater picture above, the front wall has been treated. I put a pause on that project due to my deployment. But once I get back, that will be getting finished. Then hopefully I can find time to do my Klipsch Sonotube. (we will have a newborn in Sept, and I get back early Aug) Then once we are out of debt by the end of the year, and get our 2010 tax return... time to buy the Klipsch setup, and then the sonotubes (if there is money left over). I am hoping to be able to do the Sonotubes early next year. But I have to get the Klipsch first. They are available in Germany, but who knows for how long. I can't get them shipped from the US via APO, and FedEx International... that would be about $1000 extra.

Status update: Playing with tube diameters. I found out that 800mm is 32 1/4". Our doors are 32". The window is big enough though, but I want to make sure this will fit through the doors of future houses....

As far as the Mach5, I rejected it a while back. It is dangerously close to bottoming out above the tuning frequency. There is a reason I'm doing an LLT design... I want to go low.

Okay, modeled the Mach5 at 350L tuned to 15Hz. First problem is that the port required for that tune is too long. There is not enough clearance between the end of the port and the driver. Second, the first resonance of such a port would be 163Hz. No less than 190hz is recommended. If I adjust for a 12Hz tune so that I don't lose 6db from 12Hz and below, the required excursion to get it to 115db at 30Hz takes the driver 10mm past Xmax at 16Hz! The farthest I can take this driver is 3db below reference without exceeding Xmax. Too many compromises for what I am trying to accomplish.

Okay, on to dimensions! This Sonotube was modeled specifically for the Maelstrom X, which is my first choice, and hopefully available by this time in 2012. Here's what I have.







I know the dimensions look really off with all those fractions. I modeled using mm as that is the dimensions of the stuff available in Europe. Here are some of the critical dimensions in mm.

Tube inner diameter: 750mm
Tube thickness: 9mm
Port inner diameter: 200mm

Overall diameter: 768mm (30 1/4")

Note: The top cover plate will be removable just in case I move in somewhere with a ceiling too low to tilt this monster onto it's end.

Questions:
1) Given the tube length of a little over 5", is it necessary or recommended to put a brace at the halfway point, perhaps flush with the port exit? Of course, large holes would be drilled, and the box volume would be tweaked accordingly. Even if it is unnecessary, it would be a great way to hold and compress insulation up top so no glue is required.

2) As I understand, the top cap and bottom cap assembly are both glued into place. Is this correct? Has anybody made removable endcaps?

3) These will be moved. Overseas. On a cargo ship. How sturdy are the tubes from external impacts? Would it be advisable to go thicker than 9mm on the walls for the purpose of durability, or is 9mm pretty darn strong? Should I consider devising special packaging for these? At the very least, I'm going to make a raw top and bottom plate which will screw directly to the top and bottom of the sub. This will also shorten it by almost a foot, making it easier to pack in the container.

4) How stable will this be? I am considering making the bottom plate wider than the tube itself. Could this be easy to tip over, or will the driver make it bottom heavy enough to not really matter?

Okay, that's all for now. Don't worry, I'm working my way towards the literal nuts and bolts questions! For now, I've downloaded Google Sketch Up and I'm going to play with that tomorrow.