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  1. #1
    Stronzo
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    Talking "Little Thunder"

    I was browsing through a few DIY forums, peaking through other enthusiast’s projects in the galleries when I instantly became attracted to the idea of constructing my own, inexpensive subwoofer. Already convinced of buying a sub for the main system, I decided to build this for the computer rig. I immediately set my budget at $200 in parts, and then began the design work.

    The challenge was to create a small sub that is able to fit in a tight space, yet still maintain incredible output, clarity, and depth. I ended up with a cylinder sub that stands no higher than 19 inches high, and 12 inches wide (the tube itself). In contrast to most cylinders, this one is sealed, with an upward firing woofer. Un-conventional to say the least, as I have never seen a sub quite like this one before. After all the parts (see below) were ordered, it was time to build it. What should have been a weekend project, turned out to take a month and a half. Alas, she is finally complete.

    With nervous anticipation, I hooked her up to the amp and selected some tunes to play. In short, I am completely humbled by its performance. Even throwing out bias, this thing is a dream musically, far surpassing the performance of the HSU STF-2. It also digs a bit deeper than the STF-2, which surprised me considering its small design. Running a few basic sine waves, I noticed it to drop off (rather abruptly) at 23-22 hz. Tight, balanced, accurate… no matter what you throw at it. Color me bias, but it is performing exactly how I thought it would have.

    Now, not everything is gold and sunshine, as she takes a lot more power to sing than I had anticipated, even considering the sealed design. She is also not well suited for movies, at least not on the PC. She just doesn’t have that rumbling authority. Then again, I can only pump out 80 db from the mains at full volume for DVD’s on the PC. Thankfully, theater is not its intended goal.

    Little Thunder is a huge success in the eyes of this maker. She belts out the lows, keeps amazing pace, has personality, and can shake the room (albeit not the house). Construction is over-all modest at best. She would never take the markets by storm, but for this 22 year old – she does the trick.

    Materials used:

    Concrete tube from Lowes
    1/8 screws
    Pass and Seymore Banana plugs
    Typical 16 gauge wire
    Layered Pine (or was that oak, dammit its late)
    Dayton 10’’ Sheilded Driver
    200w Class A/B Plate Amp

    Thanks for looking!


    Below are some pics.

  2. #2
    Stronzo
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    Kinda dusty

  3. #3

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    nothing armor-all cant fix ;)

    good job!

  4. #4

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    Nice job Sean. Looks really nice.

    she takes a lot more power to sing than I had anticipated, even considering the sealed design.
    A sealed design is usually more inefficient (takes more power) to run than a similarly ported design.

    So you going to throw some of that Santana at it? The song that did in the LSi 9?

    Paul

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    Thumbs up

    Looks good, and for only 200 bones. Now it's time to build a Tempest for HT duty;)
    Graham

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    Awesome. What method did you use to fit the end caps to the tube?
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Relations
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  7. #7

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    Sean,

    Once again, fine job with the sub. Normally, I wouldn't do something like this but I am for curiousity's sake and because your words may deter someone from purchasing a very affordable and capable Hsu sub. Remember your fine review of the Hsu STF-2 over at the Hsu forum? As you know, just a week later you hated the thing and got rid of it. I'm still surprised at this because I find the STF-2 very capable with music up to 90 - 95 db which is pretty loud once it is properly calibrated and setup. So why all the praise in one review and then the change in attitude towards it?

    Turns on bright interogation light;)

    p.s. not to say that you like your DIY sub better hey it is your ears and pride in manufacturing but to say it fars exceeds the Hsu in performance?? How??

    From the Hsu forum:

    THE REVIEW

    A few months back, I set out to create a system for the computer with one set goal in mind; to create a system which would boast incredible detail and accuracy throughout the spectrum. With the speakers, receiver, soundcard, and cables already purchased, all that was left was a sub. I needed something that would be incredibly durable, capable of deep extension with admirable output while maintaining accuracy. For weeks I debated between SVS and HSU. Just as I was about to make a decision, fate intervened and made the decision for me. HSU released the new STF series for a very attractive price. I saw their STF-2 for $399 shipped, and immediately pounced on the deal. A 52 lb, 10’’ driver sporting an 800w dynamic BASH amp with extension down to 25 hz, it was really a no-brainer. Did I also mention the 7 year warranty on the woofer, and the two years on parts and labor? There was no way I could decline such an offer.

    Three weeks later, UPS dropped off the print laden box which contained the new sub. I must have looked like a child ripping through their Christmas present as I impatiently ripped (no knives or scissors here) through the box. I was pleasantly surprised to find this sub was more cosmetically appealing than I thought it would be.

    FIRST IMPRESSIONS

    After setting her in the corner on top of a ½ inch thick slab of solid wood, I was ready to begin listening. Quite honestly, I was not so impressed with the sound out of the box. It seemed to lack punch, and its extension seemed only adequate. I found myself turning the volume knob on the sub up to the 12’o clock position just to receive the type of output I was used to. It did not take long for me to realize that what I was hearing was a truly accurate sub that simply did not operate like conventional subs which I have had in the room before. I then found myself setting the volume lower and lower, and finally adjusting the crossover to be dependant on the receiver setting’s.

    THE MUSIC

    Let me just state the obvious, the STF-2 delivers the goods. From the changes in pitch with bass guitars in jazz to the heavy chords of hard rock, the Hsu performed very well. The sub remained solid against the grueling test of orchestral hits, attacking with quickness and force and disappearing as quick as the notes arrived.

    Michael Jackson’s “Thriller” sounded incredibly solid, the bass never once vested more emphasis over the rest of the octaves. You just can’t help but try the moon-dance again. The kick drums and guitars from the Eagles Greatest Hits had a sense of realism and presence that many subs I have heard at a much higher cost simply could not capture. From Dead Can Dance to Outkast, the HSU STF-2 never once showed signs of reaching an excursion or extension limit.

    This sub truly is a performer that very well does its maker’s reputation justice. This sub has passed my reference low-bass tests in both percussion and synthesizer reproductions. For $399, this truly is a bargain in bass.

    CONCLUSIONS

    Chalk up another excellent product from HSU. With HSU entering the mass-market arena with the STF series, this “little” attractive sub sets a whole new standard for price/performance value. This sub may not be the last word in articulate lower octave detail, nor is it capable of reaching sub-sonic at bowel loosening levels. However, for the subtle price of $399, you are purchasing a sub capable of effortlessly blending with nearly any pair of main speakers with musical authority and accuracy along with very admirable SPL levels. To this customer, the HSU STF-2 doesn’t just represent excellent value, it represents what we all should expect from 400 dollars of our hard earned cash.

    Sean

    Gear Associated:

    Receiver: Sony AVD S50ES Digital Drive
    Speakers: Ascend Acoustics CBM-170 Bookshelf
    Soundcard: Turtle Beach Santa Cruz
    Cables: Ixos and Monster
    Software: Foobar2k

  8. #8
    Stronzo
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    Thank you for all the comments guys,

    Dr Spec,

    I simply cut groves in the wood so the tube could snugly slide on in. I secured it with regular carpenters glue, than sealed it off with caulk so no *leaking* could take effect.

    Paul,

    Trying to put me on the spot here? Whats up with that? You sure went through some searching to find that “review” of mine. First and foremost, I trust the readers here are intelligent enough to make their own decisions as to whether or not to purchase a sub like the HSU STF-2. By all means, I believe most, myself included, consider the STF-2 to be one very FINE sub for the retail price. I certainly would never discourage anyone from taking the plunge. But, if someone has the time, and very arcane, basic knowledge of subs – they can build one for the same price, if not cheaper, that can indeed better the STF-2. It is their choice to make.

    In reference to my review, no, I will not read over it again. I don’t need to. The review was spawned from excitement of hearing a clean performing and tame sub-woofer for the first time. It is very easy to get carried away when you are hyped.

    I actually intended on using this sub for my computer rig, alongside my Ascend Acoustics CBM-170’s, that is, until I decided to leave my former employer, Circuit ****ty. I was quite content with that system. I still say the HSU lacked personality, it was accurate bass, but sterile and dry, there was nothing to it. That’s why I would never personally use it for critical listening. You don’t have to agree, but it doesn’t matter in the end. Everyone makes their own choice as to what suits their needs.

    Why do I think mine is better? Well, its not. Its just different. The STF-2 will no doubt have superior SPL levels. If I ported the sub, maybe that would change …. But the STF-2 is definitely suited more for theater in a small room, than Little Thunder. Now, I personally feel Little Thunder is equally as accurate and has some spunk and personality to it. It playing even deeper is a pretty good bonus.

    Its all give and take. I’m proud of her. Could someone do better for 200 bucks? Certainly. But, she is the final piece to my PC-Audio rig, ringing in its completion. Talk about relief..

    Sean

  9. #9

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    Sometimes NEW is what drives US in one way or another to believing it's BETTER.........

    Years ago I had a Pioneer Elite vsx26tx driving a full rt series home theater.I loved the way they went togetherut .Lots of Dynamic range and a match well made.7.1 came around and the Denon avr3801 was killing the market with stellar reviews.I listened to it many times and then had to have one.Another match made well....but after awhile listening to music here and there,the Pioneer Elite I was thinking did things well dare I say better.There was a few things I liked better about the Pioneer over the Denon,but movies in 7.1 was way cool.

    I also noticed over the years that certain products played better with some then others.Matching a system is sometime I learned over time.

    I also get tired of things faster then the average listener.I constantly look for better and better.

    Love hate relationships happen.they happen to me all the time.Sometimes I sit and listen to my system and find no fault in it and enjoy all that I worked so hard to build.Then comes the days where I sit down and think"man this **** needs to get all out"Right now the B&K is on the hot chair for removal.I love the thing sometimes but there are moments I feel it lacks.Call me crazy or what have you but feeling they are.

    I think ATC is alot like me in this respect.He finds things he is happy with for awhile and then one day realizes that it's just a band aid for the time being.

    Money had alot to do with this.My money falls short of what I would really like to own.Having 2 kids,a wife,new house,really comsumes alot of my income.Gas prices going up,food is at a all time high.Just yeaterday we went shopping and spend 249.99 on food..I was in shock when she was finishing the bill.I can't ever remember spending that much on a shopping trip to our local Superfresh...god damn thats alot....

    ATC,
    good luck with your little making.I hope she lasts awhile.....

    Dan
    Last edited by mantis; 05-23-2004 at 08:58 PM.
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.

  10. #10

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    Good job, looks like a fun project!

    Regards,
    PolkTheater


    *hmmm, there is a Lowe's about a mile away, I wonder if they've got those tubes.... *hmm, I've got 2 8ohm 12" subwoofers sitting in the closet.........

  11. #11

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    Sean. My apologies for being so obscure with my previous post. When I mean "how" is it better after you had already written a fine review on the ported Hsu I thought that was a hint. Nah, I didn't have to dig too long to find the review; I have an elephant's memory for some things at times. O.k. really you got yours almost at the same time as I did and I remembered the date.

    I am curious as to why you chose a sealed design vs. the popular ported one like what Polk, Hsu, SVS, etc. all make. Ported and sealed subs both have their advantages and disadvantages. I am no expert here; but I want to learn more.

    Some things that came to my mind were that a sealed design is a much easier design. No port to make on the enclosure which is a do it right or the bass quality will suffer with ported designs. Variables here are the volume of the enclosure and amount of stuffing that one puts in the enclosure. Fixed inputs are the Thiele - Small parameters for the driver Qts, Vas, and Fs. Remember that program I sent you? It calculates the Qtc, total resonance of the speaker system. When we chatted about this a while ago I asked if you were going to make it with a Qtc of 0.707 which is the value from the program that willl give you the flattest FR and lowest F3 for a given driver with the Thiele - Small parameters given by the manufacturer. Some people actually prefer a higher Qtc value to slightly emphasize the bass but anything over 1.2 is considered too boomy.

    Perhaps you just copied someone else's design after they had done all the number crunching and that is fine too. Nothing wrong with making something that has proven to work well.

    Some other things that come to mind about the sealed design that you may like better than a ported design are quick, tight, natural, and good transients often characteristic of sealed designs. As you mention this comes at the comprimise of output. Interestingly, we also talked about placement with the Hsu as your space is limited but you said that you experimented with that and didn't think that was a factor. Often, sealed designs at least in loudspeakers are chosen due to "boundary" limitations such as walls, bookshelves etc. so that the speakers don't sound too boomy.

    Its all good my friend. Actually, I want to build a sealed design sometime in the near future myself for my two channel rig (where the Hsu currently is).

    As far as being in love with something and hating it a month or whatever later, I guess we are all guilty of that in some respect. Otherwise there would be no such thing as the "upgrade bug."

    Paul
    Last edited by pjdami; 05-24-2004 at 12:32 AM.

  12. #12
    Stronzo
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    Dan,

    It is very difficult to choose gear these days. From what I have observed, there is more good equipment, than bad. Sometimes it can be a challenge to pick out something tangible from an already well catered plate.

    As you noted, individuals like us are contented for only a temporary period of time. Thoughts, taste, and even our moods change. Sometimes there can be absolutely nothing wrong with our systems at all, we just simply become tired of that particular sound. Be it whatever it may, it is the way it is.

    Polk Thug,

    I highly recommend you starting a project! It is fun, generally simple, and educational.

    Paul,

    You propose many interesting questions, to which you followed up with answers. This makes my job a lot easier.

    From the beginning concept stages, I had a desire to design a “different” type of sub-woofer. I wanted to create a piece that would flow against the “norm”, even if in a very subtle way.

    The original intent was to port the sub. However, that idea was tossed out not long after I began to realize the limitations of the space it would be in. The corner of the closet is naturally an unstable, bloated region in the room. Even the HSU STF-2 had troubles there. It is also worthy to note that I have never heard a sealed home sub before, as all have been ported. Well, if you cant hear one, mine as well make one yourself, right?

    Going sealed was just the better route. This design completely elminated the worry of possible degredation due to the port interaction with the room. It could blend in better in the intended space, and dig deeper than a ported design, which is fairly paramount to its application. I have been told, from many sources, that sealed subs give you better accuracy, punchy, (essentially, “musical”) bass. Considering the nature of my NHT SB-3’s, and my requirements, it only seemed logical to go fowarth without a port.

    And well, there you have it.

    Sean

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    Here's a graphical representation of the Qtc of a subwoofer in a sealed design. Given the fixed T/S parameters one only has to change the volume of the sealed enclosure to get the desired Qtc.

    I can see why a Qtc of 0.9 may be very popular:
    Attached Images  

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    Nice job sean. Here is the kicker. Finally taking some time off from work. ALL OF NEXT WEEK. COMPLETELY OPEN SCHEDULE. I know I have been really busy and all. So this is the time to hit the audio stores in the area. What do you say? Drop me a line

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    Looking good buddy. Thanks for the inspiration.
    Make it Funky! :)

  16. #16
    Stronzo
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    Brian,

    Awesome. Drop me a line at: coquinino@hotmail.com

    We should be able to arrange something. Sound Approach is still under construction, which is fine. The down side is, the only two worthwhile places are southside. The good news is, they are only maybe 15-20 minutes from one another, and have very nice gear..... IT should be a great time.

    Just gimme your number and I will call so we can arrange something.


    Giddy,

    Thanks bud.

  17. #17

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    Q= O.7 is better with room gain considered. Those are probably for anechoic or quasi anechoic.

    Also, free ware is fine for basic modeling, but nothing beats actually building and testing. More companies than you might suspect use nothing BUT modeling software, build it, and offer it for sale without doing any GP or anechoic FR testing or optimizing whatsoever. Sad, really - but it's true.

    A real designer will eventually hit on a pefect combination of enclosure volume, stuffing, vent, tune point, etc. for a particular driver and there is synergy.

    Could have been Sean just nailed it for that particular driver in a sealed enclosure and it performs optimally. Nice work.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Relations
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  18. #18

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    Sean,

    Just messing around tonight decided to plug in some of those T / S parameters for the sub you built just to have a look see at what the ported vs. sealed designs may yield. I used the WinISD program I sent you a while back.

    I guessed what driver you are using by the picture. Is it the Dayton Parts Express #295-485? If it isn't then this is incorrect for your sub but correct for this particular driver. Kind of new at this but I'm experimenting around a little and thought you might be interested in this.

    Yes, you nailed the Qtc of 0.7 with the volume of 1.6 cu. ft. you mentioned the other night on AIM.

    Now for the interesting revelations. The F3 in that sealed enclosure is 46.24 Hz. In a ported configuration you would need twice the volume at 90.6 liters (vs. 45.3 liters which is equivalent to 1.6 cu. ft.) and a port diameter of 0.102 m with a length of 0.301 m (I know, SI units oh well... to lazy to convert here).

    Here are the resulting plots ported vs. sealed. The ported design doesn't roll off quite as fast and the F3 for it is 26 Hz.

    This is a pretty cool program and it is free. Like Doc mentions though, I'm really interested in what the program yields vs real world results. Looks like I might be getting excited about something new here. A DIY sub for my two channel rig would be a fun little project.

    here's the graph. yellow is sealed; green is ported. the crosshairs on the yellow line is the F3 point:
    Attached Images  
    Last edited by pjdami; 06-01-2004 at 02:27 AM.

  19. #19

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    Here is a closer shot of two. Each of the horizontal green lines (smaller finer ones) are 1 db. Starting point was 88 db @ 1 watt according to the spec sheet.
    Attached Images  

  20. #20
    Stronzo
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    Paul,

    You got the driver right:

    http://www.partsexpress.com/pe/showd...number=295-485

    Those calculations are interesting, though I would say the F3 on the sealed design is entirely off base.

    Interesting nonetheless. Call me old fashioned, but I will stick with instinct and good ole fashioned hearing.

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    hey Sean. Man I just download the newest alpha version of this WinISD program. I can't believe this is freeware! Pretty cool. Just for kicks, let's compare "lilthunder" vs. the Adire Audio Tempest in a sealed design. I know, not a fair comparison but what the heck.

    As for the F3, everything I'm playing around with here shows that the benefits of that "tighter" bass you may be hearing with a sealed design gives up lower frequency response that a ported sub can do. All theoretical and on paper but this is a great way to look at different designs and then test them out.
    Attached Images  

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    Here are some Pro and cons to Sealed vs. Vented design quoted from the help feature of the program:

    "Linearteam WinISD Pro

    Box Types: The Great Debate
    The debate over which design (Sealed vs. Vented vs. Passive radiator vs. Bandpass) is best will, like abortion, likely never end. Suffice it to say that no ONE design is best. They each have their Pro's and Con's. Anyone who tries to convince you otherwise is, at best, a well intentioned fool.

    The keyword when considering which type of enclosure to use is...Trade-Off. There are trade-offs between box types, as well as trade-offs within box types.

    Let's first begin with the Sealed box. This type of box is completely air tight, and uses the air trapped inside of the box as a suspension (like squeezing an empty plastic Coke bottle with the cap on) for the woofer. The "stiffness" of the suspension is determined by the size of the box in relation to the design of the woofer. A larger suspension (bigger box) will allow the woofer to move more freely, thereby yielding a lower bass response, but at a price in power handling, of course. Likewise, a smaller box will raise the low bass cutoff frequency, but will be able to withstand more power. There is a practical limit as to the upper and lower extremes here as well. You can achieve extremely low cutoff frequencies with sealed boxes, if you use so called Linkwitz-Transform equalizer.

    Increasing the box size decreases the Qtc of the box. Lowering the box size raises the Qtc of the box. The suggested range of the Qtc is between 0.5 and 2.0 (the Qtc rating is listed in the Project Window under the Box tab). Overall, here's the scoop on the Sealed box:

    Pluses
    Easiest of all boxes to design and construct.
    Can better handle ultra-low (<30 Hz) frequencies without destroying the woofer.
    Generally the most accurate box in the mid-bass frequencies (better transient response...notes in quick succession are more well defined).
    Can be used with motion feedback.
    Minuses
    Low bass response not as good as in a vented box.
    Lower efficiency than that of a vented box.
    Now, let's move on to the vented, or bass-reflex design. This design incorporates one or more tubes or "ports" which allow air to travel in and out of the box as the speaker cone moves in and out. The number of and size of the ports determines the -3dB point of the box. Frequencies which fall below the -3dB point aren't reproduced very well by the box. Here's the scoop on the vented box:

    Pluses
    Better low frequency response.
    Better efficiency.
    Better power handling in vicinity of tuning frequency.
    Minuses
    More difficult to design/build. If tuning frequency needs to be small, in small box, port length often becomes too awkward to realize properly. In such cases Passive radiator system may be favorable.
    Frequencies below tuning can cause the woofer to overextend itself and therefore be damaged (an electronic low frequency filter can remedy this problem, so called 6th order alignment).

  23. #23
    Stronzo
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    Thanks for the info.

    I am not surprised in the least that the Adire smashes the living hell outta the Dayton. For the price difference, it does what its expected to do (not to mention its a 12'' driver).

    Interesting nonetheless.

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