Tetsu96's 18" Xcon Sonotube Build - AVS Forum
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Old 07-04-2012, 04:44 PM - Thread Starter
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Hi AVS'ers,

Since build threads usually put smiles on people's faces, I figured I'd give back the forum which has given me so much information and inspiration over the years.

And I should probably start with a warning for anyone who is not yet infected with the bug - this is a sickness. Awareness and education bring about understanding what is good and what is not, and that coupled with everything else you can read about will put you on the track to bigger and better. I was perfectly happy with a Bose Acoustimass system with the 6" woofer unit until I read a bit more and the light bulb went off showing me that all was not right in this world.

Since then, I've moved up to a 12" Bic V1220 Subwoofer (better than the AM-15 bass module but still not great), then an SVS PB10-NSD (best premade sub I bought which I did like, but I'm sure there are a lot better). Somewhere after that came the DIY bug. I picked up a 15" Focal 40V1 sub off craigslist and tried it in a 2.5 cu/ft and then a 4.5 cu/ft enclosure. 4.5 sounded pretty good to me (with an 18Hz Tuning), but excursion was higher than I wanted in the 25-35Hz range and port noise was a definate issue with a 4" port when I wanted the system to stretch it's legs.

And then I got to reading about sonotubes and LLT style designs. If you haven't read it yet, I suggest reading Steve Callas's thread explaining LLT at HTS for detailed information and perspective on these builds, very informative reading.

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/1820-llt-explained.html

Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 04:47 PM - Thread Starter
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Multiple subs is probably the way to go for best SQ, even with LLTs, but I'm a sucker for Craigslist deals and will only build what presents itself in a cost effective manner. In January, a local guy decided to part with his 18" Xcon subwoofer. From what I read on SSA's web site, it seemed like a good sub to throw in even without knowing exactly how well it would do.

For the amp, I went with a QSC RMX 1850, saw one on Ebay for a resonable price and gave it a shot.

Slightly after I bought them, I started keeping up with the Ficar group buy thread which strayed into discussion on the Xcon subwoofer. TY to Bossobass and Ricci and others for more good info and ultimately measurements on the Xcon which differ from SSA's published specs (but seem to model more accurately).

http://www.avsforum.com/t/1380226/ficar-ssd18-group-buy-thread/480#post_21725896

Bottom line I got from the discussion - 31mm xmax and 18" cone move a lot of air, and subwoofers should mostly sound alike once they have the same frequency response (comparing this to say an LMS Ultra as an example, it's an oversimplification which glosses over details like distortion and such, but mostly correct). With a Behringer Feedback Destroyer between the receiver and the sub ampshaping the response, this should be a decent sub.

Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 04:50 PM - Thread Starter
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With the Amp and Sub acquired, and using both SSA's and Ricci's T/S parameters, it was now time to start modelling. I used Bass Box Pro for modelling and wanted to dig as low as possible while keeping excursion under Xmax for the operating range. BBP will plot out curves and account for different levels of stuffing, and also has the ability to plot graphs including room modes. I have no idea what room they use as their baseline and didn't take time time to make my own measurements, so I used their plots as a baseline and planned on a little more bump at the lower end for the room this was going to (8' ceiling, 12.5' wide, and back of room opens up to kitchen (34') and the rest of the house, total sq ft could be up to 2600 sq ft depending on how many doors are open at a given time).

BBP Predicted 114db at 10Hz w/o exceeding Xmax with a 26.7cu ft box tuned to just under 11Hz.

Total size - 72" tall (not including feet), 30.5" wide. The port dimensions are 8" wide and just over 34" long.

The 8" Sonotube was found at Home Depot. The 30" Sonotube wasn't too much harder to find, White Cap Construction carries multiple sizes and there was a location near me. As an FYI for anyone wanting to go big with their builds, the 30" Sonotube is about the largest you can fit through most standard doors without having to take anything off hinges / etc.

Oh - and the sight of that sonotube in the kitchen was driving the wife crazy. "You're not going to leave that in the kitchen forever, are you?!?" Nope, I'm moving it into the living room once it's done, but hopefully you own't notice it too much. smile.gif

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Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 04:56 PM - Thread Starter
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From here, it's a mostly a standard build thread.

2 Sheets of 4x8' MDF would be fine for cutting my caps. I went with triple baffling which is probably overkill for this.

Dampening is one of the things I read you don't really need to do with the sonotube subs except for eggcrate foam, but there is a lot of reasonance which you can easily hear if you make noise inside the tube while building it. I wanted to keep the resonance down to the lower frequencies, and used about 1.5 rolls of batts pink fiberglass insulation to wrap the walls.

I also made a rookie mistake with the router in not taking the bit size into account when cutting holes, so I ended up with 1 cap that had a 19 inch hole which the sub would not mount on. Rather than waste it, I put this inside the sub about 1/4 the way from the top and cut another from some of the leftover MDF I had. I don't really know if this would help break the back wave and any potential ringing, but it's kind of an experiment for me anyway.

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I also made shims out of plywood for mounting the sub. Used T-Nuts which one of the first things you'll read if you use them is not to hammer in the T-Nuts. Oh well, had to pull them out and then remount to get them set a bit better... I still don't think I mounted them as well as I should have, but they feel pretty solid and there's no shake or give for the sub if you press on it so should be fine.

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One other thing I tried was spraying some autobody undercoat into the port to cut port resonance and get the width down just a bit. I tried a very official "hum" test in which I'd hum into the port and find a freequency which would resonate before spraying the undercoat. I didn't hear it as much after, but I may not have heard it because the fumes from the undercoat prevented me from keeping my head near there for too long (takes several days at least to dry, not several hours and the smell sticks around longer than that).

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Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 05:01 PM - Thread Starter
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After everything dried, assembly was fairly smooth. My father in law was in town and gave me a hand with this part, definately a 2 person job. Since the Sonotube is cardboard, there's plenty of give in it and I had a hard time getting the caps to slide in until I started "shoehorn"ing them in with a wide plastic spackle knife. This was doubly important for the piece with the sub mounted as it was at least 120lbs and the stupid cardboard just didn't want that piece to go in without one little bit sticking under the cap on the other side every time we tried to get it mounted.

So after a lot of growling and grunting, they finally did get mounted. I used glue at the ends and then used a rubber mallet to push the pieces down the rest of the way. I also doubled up with glue at the ends where the caps extended past the tube.

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6" legs from home depot stood the unit up just fine, but there's only about 1/2" of screw in them and I get nervous every time I'd have to move it that those legs may break. I did break one and then re-insert and glue, hopefully I won't have to move it again anytime soon. MDF + 1/2 screw legs is not a good combination if you're going to be moving something a lot, but hopefully it's not an issue once it's just standing there.

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We did some unofficial testing at this point and I'm already happy with it. While listening to some screw job (Bear Trap IIRC), we heard something shatter from upstairs. I can't say the wife was happy about a glass vase falling off a shelf due to subwoofer, but my smile went ear to hear.

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Now on to priorities - super bowl time, and I wanted to get to enjoying it for a bit before getting to some of the work that's left. Pushed it into place, and got to chilling.

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Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 05:07 PM - Thread Starter
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Painting was something I took care of at a later date. If I knew how much spray texture paint it would eat up ahead of time, I'd probably have invested in a sprayer. At least 16 cans of spraypaint. Ugh. Still, it came out OK.

Two important lessons when painting with other people are:

1 - It's a fun thing to paint with a buddy, but teach him how to spraypaint first. Spraying textured paint 1/2 an inch away from the target makes a big gloppy mess, and sanding and re-spraying didn't completely fix this. Since nobody sits on or right in front of the sub, it's a minor issue... but annoys me that I let it happen and didn't nip it in the bud.

2 - Don't let him say "I'll come over at 4 and we'll do it then". It got dark out before we finished, and it was hard to see what we were doing from there. I ended up taking the unit inside and finishing it off on a different day. Luckily, we got 98% of it that day so it was touch ups and spots that needed work.

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It looked "decent" after this first run, but it could be better. I put up some sheets and took the spraypaint inside for round 2...

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I was happy after getting it with touchups. Nobody sits right on or in front of the sub, and direct light isn't usually hitting it. Still not perfect, but good enough that there's no need to obsess over it. White seems to work as well, it doesn't ever "vanish" into the room, but it does stand there and try to not be assuming. Like an elephant that wants to hide so it stays real still and silent (until it's not).

Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 05:15 PM - Thread Starter
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I can't say I've kept track of how many times I've run MCACC and tweaked the BFD settings, but it was a lot. It's easy for distortion to creep in when using the BFD and most advice tends torwards the "only do cuts, or maybe 1 or 2 adjustments". As distortion goes, I think the trick is to just do minor bumps up or down, and that having a number of them (say 10) doesn't detract from the SQ much if at all as long as you don't "stack" them.

BTW - room measurements were done with REW and Radioshack SPL meter. The following are my Pre-EQ measurements:

360360

I was suprised at these measurements. I expected with the kitchen back wall, I'd probably get a 14hz-ish bump from room reinforcement. Instead, my lowest mode is right under 10Hz, and 13Hz is a dip. Perhaps having the seats elsewhere would change this, but the sofa stays where it is, so it's on to adjusting frequency response for where we'll be sitting.

My EQ took a house curve of 10db from 80-40hz and leveled out from there. Here's what they look like after:

360360

The average measurements look good after EQ'ing, very smooth (these charts are w/o smoothing), but the difference in seating positions do seem notiicable for the 40-50hz and the 65-75hz ranges. Would bass traps help with this, or would the effort not make a big deal?

After taking the last set of measurements, I ran MCACC a few more times until I was happy with overall sound and sub / speaker integration, and then turned the dial on the 1850 up just a hair for a slightly hot sub.

I do like the sound. I probably want to do something with the windows as window rattle is significant at the lower frequencies before looking into bass traps. Still, It is very cool though in that the sub starts rattling things perceptably @ 9Hz.

Music sounds fantastic, bass slams where it needs to, but the sub never seems "boomy". For movies, what can be said that people don't say about subs with volume & low extension? It's funny - movies like Pulse and LOTR which are often held as benchmarks that stress subwoofers just don't seem to challenge this like they did my Focal or any of my purchased subs. Other movies like Black Hawk Down, How to Train Your Dragon, and of course War of the Worlds stand out even more as sub stress tests. WOTW makes me fear for the house if I go above -12 on the main volume now, and the sub still doesn't sound like it's working too hard.

I don't know if the sickness will push me to do another of these anytime soon, but this was an enjoyable experience. And that said, I am very pleased with the results.

Go big or go home, unless you're already at home. Then you have to go big.
My near 7' tall 18" Xcon Sonotube Subwoofer.
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Old 07-04-2012, 07:39 PM
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Cool! Nice build. Don't see very many LLT's built these days. smile.gif

My Dual 18" LLT subs 120dB down to 10hz

 

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Old 07-06-2012, 01:25 AM
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Quote:
Originally Posted by Scott Simonian View Post

Cool! Nice build. Don't see very many LLT's built these days. smile.gif

Very true, I am re-reading your build thread and may build one cabinet that neoDan designed for you for my Maelstrom-X Gen II 18" (not from the bad batch).

Nice! I bet you really love the results...but it is a sickness as you indicated.

Current Gear: PJ – BenQ PE7700; Receiver - Onkyo TX-SR805; Blu Ray - OppoBDP 103; Turntable - Dual CS-515 w/ Ortofon Super OM10; Amplifiers - OdysseyKhartago, Adcom GFA555, QSC RMX 1850HD; PEQ - Behringer FBD2496 [Near FieldSub], miniDSP 2×4 [Flanking Subs], REW; Speakers - 4 Pi (w/B&C DE250/JBL2226H) × 3 [LCR], Yamaha Crap × 2 [surrounds], Exodus Audio Maelstrom-X18" sealed sub [near field sub], LAB-12 based ported sub tuned to 22 Hz x2 [flanking subs, XO set at 40 Hz]
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Old 07-06-2012, 01:35 AM
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Originally Posted by NWCgrad View Post

Very true, I am re-reading your build thread and may build one cabinet that neoDan designed for you for my Maelstrom-X Gen II 18" (not from the bad batch).
Nice! I bet you really love the results...but it is a sickness and you will be infected with the urge to add more.

Sweet!! I modeled up a quick sim of the gen2 Mal-X18 in my LLT just in case you want to visualize the performance. 1,200w is the upper limit on power input after which you will exceed Xmax quickly.

myLLT1200wExodusMaelstrom-Xgen2.gif

My Dual 18" LLT subs 120dB down to 10hz

 

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