Austin DIY HT Projects

Discussion in 'Home Theater Forum Meets' started by Nils Luehrmann, Aug 20, 2002.

  1. Jeff Meininger

    Jeff Meininger Second Unit

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    I'm hoping to hear Hank's tempest sometime this weekend.

    If I like what I hear with the crossover set HIGH, then I may very well go with a tempest. I've just heard so much conflicting info from people I trust. Some say 120 Hz crossover is fine for the tempest, and others say it's too high.
     
  2. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Jonathan, I tend to agree with the camp that believes you definitely don't need the same quality in a sub amp as you do in a full frequency range power amp. For my mains, I just bought an Acurus 200X3 and wouldn't think of amping the critical mid-range and even the higher frequencies with a cheap power amp. I maintain that below 80Hz you can't hear distortion and other anomolies that you can hear at higher frequencies where the ear is proven to be much more sensitive. Crown and some other separate amps used by enthusiasts are better than plate amps, maybe a little better in terms of accuracy, but where they shine is in huge amp output and ruggged reliability. Their design heritage is just that, being developed for pro sound reinforcement in clubs, auditoriums and road shows.
    An aside topic. My son is getting an electric guitar ([​IMG] ) for his birthday. I need an inexpensive practice amp for him. Anybody have suggestions beyond the usual music stores/pawn shops?
     
  3. Jonathan DA

    Jonathan DA Screenwriter

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    With sub amps it's all about dynamics and headroom. Most plate amps just can't cut it. I agree with you on distortion, it is very hard to detect at low freqs.
     
  4. Mark Hayenga

    Mark Hayenga Supporting Actor

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    Jeff,
    You're also welcome to come hear my Tempests also. I've got twin 270 liter / 18Hz tuned boxes for them and 325w per from an Adcom 555II. Crossover is active 3rd order @ 100hz via my pre/pro.
    Whatever sub you build, you HAVE to finish it in crushed velvet :)
    Greg,
    The Sharp will definitely be there, so long as it is not required by the parental units (ie the people who actually own it [​IMG]). I would like to see how the HTPC improves scaling.
     
  5. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Mark, would you bring along one of your crushed velvet speaker units? Inquiring minds want to see it.
    My quest is for faux leopard fur (like on the cover of my Ultralounge sampler CD box). I've got a yen to cover a pair of my BoseBusters in fur. Are we a sick group here in Austin, or what?
    Omigosh, I just had a design idea: a BoseBuster in the shape of a martini olive! Somebody stop me![​IMG]
     
  6. Brian Bunge

    Brian Bunge Producer

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    Hank,
    I see your goal is really to be James Bond! I guess all the girls will start calling you "Hankipooh" huh? [​IMG]
    Brian
     
  7. Jeff Meininger

    Jeff Meininger Second Unit

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    Hank: thanks for the demo! Your sub is terrific. It punched me in the chest during lord of the rings. Wow!

    I'm coming away with mixed feelings, though. The sub sounded so much better with the crossover turned down. Up high, where I'm going to have it, it's just not as clean. (I look forward to the day that I have larger mains.) You advised me that a smaller driver won't cure this, so I see no reason to go down to a 12".

    My current two ideas are a 150L sealed tempest sub, or perhaps one of the lambda drivers that Jonathan recommended.

    Jonathan: From what I can tell from the lambda site _and_ stryke site, the PL driver series includes several sub-categories, including SB. (Stryke says SAL series is formerly known as Lambda PL.) I can't find much technical information on the SB12 or SB15, though. It would be a no-go if I couldn't use it in a downfiring position. I'm really stuck on the idea of a tube.

    Anyway, thanks again Hank for showing me what a REAL sub can do.
     
  8. Jonathan DA

    Jonathan DA Screenwriter

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    Jeff, have you done any modelling of the drivers you're considering? You'll quickly find that certain drivers work better in sealed boxes than others. Higher Qts drivers will almost always work better than low Qts drivers. The f3 of a sealed Tempest will not be any better, and may be worse, than an SB12, NHT 1259, or Titanic 1200 in a smaller enclosure. Plus changing from a ported to a sealed box will barely affect the driver's sound at 120Hz. More than likely the reason you thought it didn't sound right at the higher frequencies was because the level of sub was set higher than the level of mains, causing a poor integration at the crossover point. If you carefully matched the levels with a sound meter I'll wager you'd like the sound a lot better. I'd also wager you'd find the bass too quiet at that point, most people prefer an elevated level of bass. This is where the lower crossover point comes in handy, you can have your midbass sounding natural and your lower bass elevated.

    As for the Lambda drivers, what I said is correct, both have the same motor, but the SB drivers are not available with a phase plug to the best of my knowledge. The SAL identification was something that John Janowitz did specifically for Stryke (I believe SAL means Stryke Audio Lambda), whereas if you go to the Lambda site, Nick still refers to them as Premium drivers. It's just an OEM thing.
     
  9. Jeff Meininger

    Jeff Meininger Second Unit

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    Jonathan: Re "OEM thing" - Oh, I see.
    I've done a bit of modeling with lspcad, and some with winisd. I don't trust my modeling, though, because I can't make my curves match the specs in the Adire .pdf files for specific enclosures. Close, but no cigar. I must be doing something wrong, though I'm following the directions at http://www.quux.net/roo/diy/sonosub/lspcad.html. My F3 almost always comes out higher than where adire has it in their docs.
    I'll give WinISD another shot... I haven't explored that one quite as much yet.
     
  10. Jeff Meininger

    Jeff Meininger Second Unit

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    It's about time to start collecting materials. Is there an agreed-upon "best place" in Austin that sells less-than-12-foot lengths of sonotube? Or should I just pick up the yellow pages and let my fingers do the walking?

    Thanks!
     
  11. Paul_Laiming

    Paul_Laiming Auditioning

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    Hey Jeff,
    If you cant find any shorter lengths than 12feet, id be
    willing to split with you. i need to build a sub as well.

    -paul
     
  12. Jeff Meininger

    Jeff Meininger Second Unit

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    Paul: I'm planning on using 18" tube. If you're going to use the same size, splitting it would be great! If you were planning on using 22" tube, you should contact Jeff Todd , as he's looking for tube in that size.
     
  13. JeffTodd

    JeffTodd Stunt Coordinator

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    Paul,

    I am in Houston now and am going to Burrus Concrete supply in the morning to see what I can dig up in the way of 22" tube. I only need around 2ft....so if I can get around a 6' piece for a good price then I could bring some back to Austin. Let me know via email or on here if you are interested....if I can get it that is.
     
  14. Jeff Meininger

    Jeff Meininger Second Unit

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    FYI: I'm switching plans from 18" to 20".
     
  15. JeffTodd

    JeffTodd Stunt Coordinator

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    I picked up 3ft of 22" diameter concrete form for $20. I have all of my endcaps and base cut from .75" MDF. I now have to figure a way to cut this tube down to the length that I need. This stuff sure is addicting....I just can't stop. I don't see an end to this fun.
     
  16. Jeff Meininger

    Jeff Meininger Second Unit

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    I haven't done it before, but I've read volumes. Here's what I know about cutting sonotube to length.

    1a. To get a "square" (level) cut, get some printer paper where the sheets are all still connected. Wrap it tightly around the tube so that the edges overlap neatly, and tape it place as securely as you can. Then you can use the edge of the paper to draw a straight line around the tube. Most people drill a hole into the scrap area, and start cutting along the line (carefully!) with a jigsaw.

    1b. If you want an absolutely razor-sharp edge on your tube, you can use the same paper trick, but INSIDE the tube. Then you can temporarily install an "endcap" plug inside the tube that sits flush with the line. Once it is fixed in place, you can use a router with a "flush" bit to trim the tube flush.

    What was your experience at burrus concrete supply? It sounds like you got a pretty good deal and didn't have to buy a huge length. Did you have to insist, or were they happy to sell you a 3-foot section? Are you happy with the quality of the tube you got (not warped, etc)?
     
  17. JeffTodd

    JeffTodd Stunt Coordinator

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    Thanks for the info on cutting the tube. I think I wil employ the paper wrap trick and then take the circular to it. I only need about 19" of the 36" so I have room to play with.

    My experience with Burrus was great. They had only one length of 22" tube left in the stock, but they were more than willing to give me the 3ft that I needed. The only questions that they asked were "What are you going to do with it?" I must have stood outside and shot the shit with them for about 20 minutes. I only left because the weather was turning nasty (TS Fay was rolling in). The tube appears to be in decent shape. The inside diameter seems to be 22" dead on. My endcaps fit damn snug....I had to basically hammer them in for a test fit.

    Hopefully I will get the SVS driver from Mark Larson soon....I paypalled him on Friday, so I hope to be seeing a nice 12" sub soon. And then the final steps to finishing this project will start. I hope to end up with a 25" total height 22" diameter sub that will be able to be used as a small table (replacing one that currently exists against a wall in the living room.)
     
  18. Jeff Meininger

    Jeff Meininger Second Unit

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    Anyone want to split a 12-foot 20-inch diameter sonotube with me? I found a nice deal ($69 for 12 feet), but they're not willing to sell a partial tube.

    I cross-posted this to the DIY section.
     
  19. Jeff Meininger

    Jeff Meininger Second Unit

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    I'd also be willing to give someone half of the tube (6 feet) for free if you let me borrow a tool or two (router/bits/circle jig/jig saw... whatever you have would help since I must buy/rent the rest) for a weekend. I'd promise to take good care of them. It wouldn't be the first time I've used a router or jig saw.
     
  20. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Jeff, I posted a repy in the main DIY section. Bring the tube over and we'll cut it. I have a couple of routers and you can borrow one and my masonite large circle jig.
     

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