Dual SVS Driver Coffee Table Sub Want Advice

Discussion in 'Archived Threads 2001-2004' started by Harold A, Aug 14, 2002.

  1. Harold A

    Harold A Stunt Coordinator

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    I have 2 original SVS drivers that I plan to make a coffee table sub out of. I have played with the design in Win ISD. Here is what I come up with:

    ~9.7 cuft enclosure, with 2 6" ports at 3ft in length that would tune the enclosure to ~18hz if I am using the software correctly.

    How does this look?

    Also, I will be using an Adire AVA250 plate amp to drive this sub. If I wire them in parallel they will present an 2 ohm load to the amp. Is this to low a load to drive with the amp? Or sure I wire then in series and present an 8 ohm load to the amp?

    Thanks

    Once I start I will put out alot more details.
     
  2. ChrisAttebery

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    Harold,

    I don't know about the enclosure, but I would definately wire them in series. 2 ohms will probably smoke the amp pretty quick. They just aren't build for that.



    Chris
     
  3. You also do not need a PAIR 6" ports on that 12" driver!.... That driver has a similar displacement to the shiva. You would be fine with a pair of 4" flaired ports that Adire sells. This also lets you shorten the length a bit!

    (and 2ohms=bad! on most any plate amp)
     
  4. Dustin B

    Dustin B Producer

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    Volume should be good. But I don't think dual 6" ports is such a good idea in an enclosure that size. 37" is a bit long for a 6" port. You really don't want to go any more than 30". A single 6" port does just fine with a Tempest, so dual original SVS drivers should do just fine with a single 6" port as well.

    Also remember that two 6" ports that are 37" long will take up almost 35L (1.25ft^3) inside the enclosure.
     
  5. Harold A

    Harold A Stunt Coordinator

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    Thanks for the advice on the ports. SO far the only sub I have built is my sealed Shiva.

    I had figured that driving the plate amp at a 2 ohm load would lead to bad things but just wanted to check.
     
  6. Patrick Sun

    Patrick Sun Studio Mogul

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    Does anyone know if the SVS drivers are a nominal 4 ohm driver? I was thinking they are an 8 ohm driver. They only have one set of terminal connections.
     
  7. Geoff L

    Geoff L Screenwriter

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    Harold,

    Sticking with the coffee table idea, might you make it into ~{2 seperate encloser}~ inside. Tune to 16hz and drive each side with it's own plate amp.
    =======>
    How big is your room?,, and where will the table be placed, middle of the room against a wall, etc?
    =======>

    The 2 ohm load thing isn't going happen. Can you say poof!
    They will drive a 3-ohm load but this is not recomended and when pushed hard for long periods can shut down.
    Your going to need all the power you can get out of those 4-ohm palte amps (headroom). By not having your coffee table corner loaded your going to loose much of your natural room gain when not corner or wall loaded.

    Unless you need the built in crossover, fully 180 variable phase control,and possibly a boost modification, I see
    130.00 smackers for one plate or better yet 260.00 for two plus shipping, will go a along way toward a larger dedicated power head at Ebay.
    Should be able to find something with 300 aside pretty easy for that kinda change. Maybe one thats capable of driving a 2-ohm load with even more power, not that you will need it but extra headroom is always good especialy if you have to start boosting lower freqs.. If patient at Ebay you could find an amp their and possibly have enough left over for a BFD to help smoothe out and or boost response.

    Just some things you might consider.

    Also if I read corretly, the huge box for the two SVS drivers will require extensive bracing. If you make it into two seperate enclosers in one large coffee box, this might be a better idea. Ports would be shorter for same tuning and some what less bracing.
    Of course you need to port both driver enclosers that make up the one big coffee table box. Port any place -(top, side, front, or back,) also need 1 big 2-channel Amp of 200-watts plus or 2 plate amps.

    Decisions decisions, thats what it's all about.

    Sounds fun and good luck.
    Geoff

    Edit: The old SVS is 4-ohm....
     
  8. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    "Does anyone know if the SVS drivers are a nominal 4 ohm driver?"

    Yes they are 4 ohms.

    "If you make it into two seperate encloser in one large coffee box might, thi might be a better idea. Ports would be shorter for same tuning."

    Are you sure about that? For instance, if I have two seperate boxes that are:
    100L each
    Single 4" x 18" port each

    They should have the same tuning as a single box that is:
    200L
    Dual 4" x 18" ports

    because you have the same port area per box volume. I don't think the port length should change unless you change this ratio.
     
  9. Geoff L

    Geoff L Screenwriter

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    Good point, I didn't explain that part.
    16hz tuning instead of the 18hz.

    I should have been clearer, dropping from the 6" port to the 4" flaired port. The 6" will never fit in the seperate enclosers where as the 4"'s would....
     
  10. Harold A

    Harold A Stunt Coordinator

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    I was not going to mount my plate amp in the enclosure. This wasy when I had the $$$ I could upgrade.

    I have 2 extra channels on my Carver AV-705X but would not have the adjustable cross over. I have a Sony DB930 receiver and the cross over point is stuck at 80hz with no adjustments for phase and what now. However, the amp will drive the SVS driver at 200 watts each
     
  11. Mark Seaton

    Mark Seaton Supporting Actor

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    Just a thought...

    I've thrown this out there before, and if you search for my posts you should find more detail, but I have had an idea for a table style sub which I would offer up.

    The first thing is, for a table, and IMO, for any sub, vibration is an issue. You can reduce it greatly via brute force and weight, but I much prefer the more elegant solution of mounting the drivers in opposing directions. Remember for a subwoofer you really want a rigid enclosure which doesn't resonate within its passband. This goes against the super heavy box, and toward a rigid, well braced box. Being a coffee table, you do have to concern yourself with where the drivers reside, which generally leads most people to go with a down firing solution. Is down firing that bad? No, but it is a compromise, and you still have the walking tendency or a table you really don't want to have to move very often!

    What I suggest:
    There are two method that come to mind for opposed mounting. I do like Martin Logan's badging of "Balanced Force Configuration" as it conveys both the intent and the method. The first method is like Martin Logan, Mirage, Krell, ourselves, and a handfull of others build their subs where the drivers are on opposing sides fo the enclosure. The second option is to mount the drivers facing each other into a manifold of sorts, exactly like many IB subwoofers are configured. This mounting makes the most sense to me for this application, as it protects the drivers from harm, and only requires a grille to cover the opening which can be narrower than the drivers would have been. The opening can also be made to the bottom of the box for an ultra-stealth look.

    Obviously the compromise with this implementation is that you sacrifice internal box volume. In a coffee table type design, this is less of an issue, and why I recommend it.

    Regards,
     
  12. Harold A

    Harold A Stunt Coordinator

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    Mark,

    I am intrigued by your idea of essentially an IB sube for my coffee table design. I am not sure I follow what you are suggesting though.

    Is it to have a small chamber which both subs fire into which is open to the outside of the box and use the rest of the internal volume of the table as an IB of sorts? If so is the volume large enough? I can go with a larger table if need be.

    Is this correct? If not can you explain it a little more.
     
  13. Dustin B

    Dustin B Producer

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    It won't be an IB (unless you want a 50ft^3 coffee table :p)).
    He is just suggesting using the manifold technique you see used by the people who do infinite baffel subs in a sealed or ported coffee table.
    I like the idea of it opening down as well. Just make sure the table is tall enough to leave some space between the top of the manifold and the top of the table, and to have 3"-4" legs. You could then offset the manifold to one side of the table which would allow you to have one drivers back very close to a wall, and the port and the other driver on the other side with lots of space behind them (for the port length). Wish I could draw, picture would be worth a lot more than words [​IMG]
     
  14. Mark Seaton

    Mark Seaton Supporting Actor

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  15. Dustin B

    Dustin B Producer

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    A little off topic, but would you mind explaining what mass loading the driver is Mark? Like how you do it and what its' benefits/drawbacks are?
     
  16. Harold A

    Harold A Stunt Coordinator

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    Mark,

    So is the sub then basically a sealed sub with 2 drivers? I guess I don't fully understand. What advantage is there by having both drivers firing through a singal opening as opposed to out in the room.
     
  17. ChrisAttebery

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    Harold,

    Basically, the sub will be constructed of two seperate boxes whose drivers face each other. The drivers will fire into another box, aka the manifold, that will be open on the bottom. I would make the manifold at least 12" wide the drivers 6" apart so that the drivers will not compress each other. The boxes can be vented, but not into the maifold that connects the drivers.

    The advantage of this system is that the drivers will be firing into each other and balancing the force of the drivers. The sub won't try to walk across your room every time you fire it up.



    Chris
     
  18. Brian Bunge

    Brian Bunge Producer

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    Could you simply have two separate sealed enclosures firing towards each other with the sides and top running the full length and then legs on the bottom? Or is this what everyone is saying? I'm thinking that would make it fairly easy to remove the drivers if necessary.

    I'm planning on building a Tumult sub with an LT into an endtable but I've got a buddy that would probably go for the coffee table route if it was stealth. I figure some nice 4" bun feet on the bottom would work nicely.

    Brian
     
  19. Bryan Michael

    Bryan Michael Supporting Actor

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    for a while i thought you guys were sujusting a iso-baric sub with both drivers in a sandwith and 2 boxes one sealed and one ported
     
  20. Mark Seaton

    Mark Seaton Supporting Actor

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