Sealed subwoofers for home theater

Discussion in 'Archived Threads 2001-2004' started by Tyler, Jun 6, 2001.

  1. Tyler

    Tyler Stunt Coordinator

    Joined:
    May 8, 2001
    Messages:
    112
    Likes Received:
    0
    Trophy Points:
    0
    Dan Wiggins said i should go with a 16" sealed cube for my first DIY sub.
    He said that i should be able to get around 95dB from 20hz and up in room ?
    Is that true
    The woofer will be a SHIVA MKII and a AVA250 plate amp
     
  2. Seungsoo Hwang

    Seungsoo Hwang Stunt Coordinator

    Joined:
    Aug 6, 1999
    Messages:
    204
    Likes Received:
    0
    Trophy Points:
    0
    Well, I dont think Dan would lie to you [​IMG]. It depends on your room size and stuff like that, but I would probably take Dan's word for it. He probably suggested the sealed sub since this is your first, and it is easier to build than a vented design.
     
  3. Tyler

    Tyler Stunt Coordinator

    Joined:
    May 8, 2001
    Messages:
    112
    Likes Received:
    0
    Trophy Points:
    0
    Thanks.
    I hope it will go down to 20hz even 25hz would be good.
    What are the advanteges of a sealed sub and the bad sides or a sealed sub ?
     
  4. Brandon B

    Brandon B Second Unit

    Joined:
    Mar 23, 2001
    Messages:
    263
    Likes Received:
    0
    Trophy Points:
    0
  5. ChrisA

    ChrisA Second Unit

    Joined:
    Nov 25, 1999
    Messages:
    478
    Likes Received:
    0
    Trophy Points:
    0
    From the link provided above which I wholeheartedly disagree with regarding ported/vented enclosure:
    quote: Transient response is degraded, yielding typical group delay curves as high as 50 ms. Muggy, boomy, sluggish, one-note, slow, and inaccurate are common terms associated with vented enclosures.[/quote]
    This is entirely innacurate. Group delay is actually *less* than sealed until you get close to the tuning frequency, especially in extended bass shelf designs with large enclosures. The lower you tune, the lower the point until group delay rises... A large EBS design will give you the advantage of lower group delay and less excursion/distortion near the tuning frequency. It has been reported that it takes approximately 1000 ms of group delay in subwoofer frequencies to become audible. In any case, Extended bass shelf designs have less group delay than sealed up until the point where you approach the tuning frequency. EBS can sound subjectlively better than the best sealed because the subwoofers that can reproduce the most linear bandwidth tend to sound better. SVS, Aerial 10T, are examples of EBS designs. Be wary of commercial subs that do not provide large enough internal cabinet volumes and/or a port that is too small in diameter and/or a driver with inadequate compliance (too small a VAS) for the enlosure... THAT will make it sound as described above. EBS is probably one of the favorite, if not most popular designs for DIY'ers...
    I just noticed they do talk about EBS as a seperate entity. Since EBS is a vented design, it still would be better to clarify that there are many subtypes of vented enclosures that have advantages over sealed enclosures.
     
  6. KonradN

    KonradN Stunt Coordinator

    Joined:
    Dec 3, 2000
    Messages:
    131
    Likes Received:
    0
    Trophy Points:
    0
    i know some songs that have 3 to 4 bass notes hit within a second. I am not exactly sure what group delay is but if it is the time it takes the cone to recover before making another hit then a group delay of a second sounds pretty slow to me.
     
  7. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    0
    Trophy Points:
    0
    Tyler,
    Go with what Dan said, it'll be best for your first sub. Dan reads these boards, so why not just ask him if what he told you is true? Your actual SPL will be determined by the amount of room gain you have. Have you used Adire's LSPCad yet, as advised? It will answer many of your questions.
    Chris,
    Very well put. The quote you took from the article may describe many, or even most, commercial vented designs (less true in modern subs,though), but that does not impugn the loading scheme itself when done properly.
    quote: Be wary of commercial subs that do not provide large enough internal cabinet volumes and/or a port that is too small in diameter and/or a driver with inadequate compliance (too small a VAS) for the enlosure... THAT will make it sound as described above. [/quote]
    Yep. And you just described almost all commercial vented subs. That's the main advantage of DIY bass-reflex...you can give the driver the space it needs, and adequate porting. Even the $4500 Ariel 12" subwoofer might be considered underported by some, with "only" (what appears to be) a flared 4" vent along with a driver similar to the Mass 12 (large displacement) and 400 watts behind it.
    Here's an intersting article which addresses your point about how moving the f3 lower can lower GD in the audible bandwidth. http://www.trueaudio.com/basslst2.htm
    Konrad,
    That article tells a bit about group delay.
     
  8. DanWiggins

    DanWiggins Second Unit

    Joined:
    Aug 15, 1999
    Messages:
    324
    Likes Received:
    0
    Trophy Points:
    0
    Hi all,
    A couple of things: ChrisA is correct about transient response; it all depends upon the tuning. A well-designed vented box can have better transient response than a poorly designed sealed box. While sealed boxes have the POTENTIAL for better transient response, it does not mean they automatically have it!
    Additionally, be aware that one of Tyler's requirements was a small box; originally we had discussed a 100L vented box, but that was, alas, too big. After discussing acceptable sizes for cabinets, Tyler would like a box in the under 60L range. Thus a smaller sealed cabinet is really the best choice here, since venting that small of a cabinet gains you precious little in terms of extension OR maximum SPL, and costs you in terms of transient response and power handling.
    Dan Wiggins
    Adire Audio
    ------------------
     
  9. Han

    Han Second Unit

    Joined:
    Jan 13, 2001
    Messages:
    262
    Likes Received:
    0
    Trophy Points:
    0
    I've actually order a Shiva + AVA250 combo as well. Is it alright to do this in a seal downfiring method? 16 inch cube or 16x16x20 or so rectangular box? And how much ground clearance should I give it, 2-3 inches?
     
  10. DanWiggins

    DanWiggins Second Unit

    Joined:
    Aug 15, 1999
    Messages:
    324
    Likes Received:
    0
    Trophy Points:
    0
    Han,
    I'd recommend a good 3" clearance on the bottom. And yes, downfiring is perfectly acceptable; all our reference designs have downfiring drivers.
    Dan Wiggins
    Adire Audio
    ------------------
     
  11. Brandon B

    Brandon B Second Unit

    Joined:
    Mar 23, 2001
    Messages:
    263
    Likes Received:
    0
    Trophy Points:
    0
    Chris
    I posted the link above. Since I am pretty new to this stuff, it had seemed a pretty informative page to me. If the more knowledgeable posters here think this is a poor page, I'll rerain from referring people to it in the future.
    Or is it pretty good with maybe a disclaimer about the misinfo on ported enclosures?
    BB
     
  12. ChrisA

    ChrisA Second Unit

    Joined:
    Nov 25, 1999
    Messages:
    478
    Likes Received:
    0
    Trophy Points:
    0
    I just think that one sentence that I quoted above is misleading and needs to be re-written in the sense of what Dan, myself and the others have written. It seems to be decent otherwise.
    I do think its funny how glorified that Ariel sub is when anyone could spank it. If only would could convince more people to take the DIY plunge. The Aerial 10T cabinet rigidity and crossbrassing scheme are just poor compared to what is available as a DIY materials and method, and as you mention, the port diameter is too small. A DIY'er would increas the cabinet volume slightly, increase the depth of the cabinet, and also thereby allow for a larger diameter port...
    ------------------
    Pictures: The Worm Hole Theater featuring the Black Hole Subs and Death Star Platform
     
  13. Jack Gilvey

    Jack Gilvey Producer

    Joined:
    Mar 13, 1999
    Messages:
    4,948
    Likes Received:
    0
    Trophy Points:
    0
    I'd agree about the Ariel, Chris. I brought up that point over on this board:
    http://208.186.16.166/cfb/index.cfm?...226&StartRow=1
    ...and was met with vehement disagreement. The guy who disagreed admitted to knowing nothing about DIY, though. I find that the level of informed technical discourse of a board reflects the vitality of its DIY community. It's nonexistent on that board, it seems.
    People find it extremely hard to comprehend, given the prices charged for these commercial subs, that they can be outdone for a fraction of the cost,but it's almost always a case of commercial compromises due to size.
     
  14. Hank Frankenberg

    Hank Frankenberg Cinematographer

    Joined:
    Oct 13, 1998
    Messages:
    2,573
    Likes Received:
    0
    Trophy Points:
    0
    Yes, "...commercial compromizes due to size..." is EXACTLY the problem with basing subwoofer purchase OR design decisions on what you see in retail stores. The shipping costs of a subwoofer are determined by its size/weight, and are a significant percent of its cost to a manufacturer, distributor and dealer. The result is undersized cabinets at retail, and therefore, "boomy" one-note bass from most vented designs. If you can accomodate the correct cabinet size, a vented design, as pointed out above, can be as "fast" as a sealed design. That being said, if small cabinet size is the limiting factor, sealed is it.
     

Share This Page