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Discussion in 'Home Theater Projects' started by Travis-J, Jul 9, 2003.

  1. Travis-J

    Travis-J Agent

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    I was planning on building a pair of surrounds, but accidentally bought a pair of paradigm titans, oops.

    So the next project on the list is a powered sub.
    I'd like to try to build one, as price is an issue, I can do woodworking have the tools etc. I use my system for about 60/40 Music/Movies. I don't need thundering base, I just want to fill in the low end. So what do you suggest for drivers and amplifiers?
     
  2. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    What dimensions would you prefer?
    How much do you want to spend?
    Without knowing that stuff this is the best that I can do:

    There's a number of high-value, reasonably-priced components that are always recommended around here. Here's my list. Prices listed are off the top of my head so they may be +/- $10 and you might find them on sale.


    From www.adireaudio.com

    Adire Shiva ($120)
    Adire Tempest ($140)
    Adire Maelstrom ($250?)
    Adire Tumult ($500)

    From www.partsexpress.com
    Dayton 12" DVC ($125)
    Dayton 15" DVC ($140)
    Dayton 12" Titanic Mk2 ($150)
    120 watt plate amp ($100)
    250 watt plate amp ($120)

    From www.stryke.com
    AV12 ($175)
    AV15 ($205)

    From Rhythmic Audio
    350 watt plate amp ($140)

    Sealed 12" subs generally range from 1.2 cu ft to 2.5 cu ft.
    Vented 12" subs from 3 cu ft to 5 cu ft.
    Sealed 15" subs from 2.5 cu ft to 6 cu ft.
    Vented 15" subs from 6 cu ft to 12 cu ft.

    These are net internal volume numbers. Once you narrow down the size and budget then we can get specific. Be sure to check out the tech papers on the Adire website. They have complete plans for 3 sealed alignments and 3 vented alignments for both the Shiva and the Tempest.
     
  3. Travis-J

    Travis-J Agent

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    Size isn't a huge issue, if I can build a better sub cheaper by using a larger enclosure then I'm all for it.

    The tumult and the maelstrom are a bit pricey, what would you suggest from the others u listed. It seems to me go with a rythmic amp most wattage, makes sense right?
    I will post the measurements of my room. The tempest seems good for the price.
     
  4. Travis-J

    Travis-J Agent

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    My room is approximately 15X15 it but it has two extra 6x2.5
    too make it kindof like a T with a fat stem. If that makes sense. Oh and where is a good place to order the Rythmic amp from? I live in BC Canada.
     
  5. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Here's the Rythmik audio page. It's a heck of an amp. Has the most power AND features for your dollar. Some of the woofers I mentioned will max out at about 250 - 300watts in some alignments but its always nice to have extra amp power to spare. And the switch-controlled rumble filter is just way cool. I wish my plate amp had it, but I can't compain too bad since I got the Parts Express 250watt plate amp on sale for $100.

    http://www.rythmikaudio.com/nonservo_product.htm

    With your room you've got about 2000 to 2500 cu ft to fill. Should be pretty easy to fill that with quality bass from a decent sub. For comparison my open floorplan has a 20x30x10 living room/kitchen that opens into a number of other areas and I can still rattle the windows even when I only run one of my subs. For your reference one of them is a Dayton 12" DVC with in 3.5 cu ft tuned to 22Hz and powered with the 250 watt plate amp. The other is an SVS 25-31PC (the original PC).

    You can definately get more bang for your buck if you're willing to live with a bigger enclosure. The value champion is probably a 15" woofer like the Adire Tempest or the Dayton 15" DVC in a big ported enclosure. The Adire tech papers have all the details you'll need. But we're talking about a BIG,BIG enclosure here. 10 cu ft is just freaking huge. I'm pretty sure Adire has got a Canadian distributor so you won't have to worry about duties.

    The AV15 can move quite a bit more air than the Tempest, but its also a bit more expensive and you'll need about 750 watts to really take advantage of it whereas the Tempest will reach its full capabilities with around 300 watts. Of course this all depends on the enclosure as well, but it seems to be the case in most applications.

    Adire also sells plate amps but their prices are not competitive here in the US. For instance, their AVA250 is a virtual twin of the Parts Express 250 watt plate amp but they charge $180 vs $120 from PE. Still, I have no idea how much duties run so it might actually be cheaper for you to buy everything from Adire's Canadian distributor.

    BTW, all the prices I've been listing are US$.
     
  6. Travis-J

    Travis-J Agent

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    Thanks Ya I know where I can order the tempest from in BC so that's good. How is rythmic audio to deal with? I'm kinda new to this whole internet buying thing.
     
  7. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Never actually dealt with Rythmik. Like I said, my amp is the PE 250 watter from Parts Express and they are absolutely great to work with - they did more than their part to help me out when I did something kinda dumb with the amp. They really took care of me and I learned a valuable lesson - the power caps on many amps can stay "hot" for DAYS after being unplugged. I'm not exaggerating at all here. Even though the pre-amp's power supply is sucked dry you could easily have over +/- 50 volts on the amp's power supply rails.
     
  8. JesseSilver

    JesseSilver Extra

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    I have been dealing with Rythmik, and can tell you that Brian Ding is a class-act. I had many questions regarding their 350-se amp and the new Linkwitz transform available for it, and Brian has been nothing but a wealth of information and a great help. His time and efforts go beyond what could possibly be expected for such a great product offered at such a reasonable price.

    No, I don't work for Rythmik, and no he didn't tell me to say this, but that's the kind of service I have thus-far gotten!
     
  9. Allen Ross

    Allen Ross Supporting Actor

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  10. Jack Gilvey

    Jack Gilvey Producer

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  11. Allen Ross

    Allen Ross Supporting Actor

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    i think it does nothing cause you are cutting power to the circuitry which shuts off the out put, you know that click when it first comes on, Its differnt then power amps, my DC 300A II will play for about a min or two at moderate levels before it peters out.

    At least thats what i think i could be wrong i have been in the past a lot [​IMG]
     
  12. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Jack, I agree with Allen. I haven't actually tried unplugging it while it's playing and then measuring the rails. But the amp board has a heck of a lot of capacitance (even with only 2 caps) and the pre-amp power supply goes down pretty quick even when its only powering the LED.

    The problem I ran into is this:
    If you're wanting to mod the pre-amp board you'll likely decide to disconnect it from the amp board just to make it easier to work on (besides, that's what the PE instructions tell you to do). But once the pre-amp board is disconnected the amp board has a "hot" power supply (around +/- 70V) and a floating input. That floating input could be driving the outputs to who-knows-where. Maybe even to the rails.

    So if you happen to touch the two speaker leads together you've just shorted the power supply and maybe accidently welded something! Like I said, that's a lot of capacitance and you'd be likely to see some of the "magic smoke" seeping out of some component. We all know these things don't work once you let out the "magic smoke".

    You've got 3 choices to prevent this:
    1) Take extra precautions to keep the speaker leads from touching. Tape them. Wrap them. Whatever.

    2) Don't disconnect the pre-amp board from the amp board. This keeps the signal input near ground voltage.

    3) Bleed the amp supply rails with two resistors. This is the most difficult because there's not really a great way to clip to the rails (it can be done, but not well) and you don't really want to solder on permanent bleeder resistors since the diode bridge isn't designed for that. If the power rails are discharged to 0V then the diode bridge is stressed pretty hard when the transformer goes to 75V or whatever. Its okay to do that a few times during mods but you'd wear it out if this happened every time you turned the amp off.

    You'd use two resistors to bleed the positive rail to ground and the negative rail to ground. If you bleed the positive to the negative you might not end up exactly at zero volts. And you want to use a pretty big resistor since you've probably got 1/4 watt resistors.

    Power = Voltage^2/Resistance so for 80 watts or so, you'd want 30k ohm or larger resistors. With 30k ohms it might take a good 30 minutes to an hour to get the rails mostly discharged. You can watch them discharge with a multimeter.

    Now you've learned the easy way what I learned the hard way.
     
  13. Travis-J

    Travis-J Agent

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    I'm thinking I will go with a tempest, seeing as I can buy one from near here with cheap shipping. And the rythmic amp seems like the best bang for buck, now all I have to do is wait for g/f approval and $$ hope to start the project in mid-August. If anyone has either of these used for sale let me know, the closer the better, and the cheaper the better.
    Which of the aligments would be A) easiest as I dont have any testing stuff. b) best sounding, like I said I don't need huge bass, just a good low end.
     
  14. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    "for 80 watts or so, you'd want 30k ohm or larger resistors"

    Oops that should read "for 80 volts or so".

    Jack,
    So long as you keep the pre-amp board connected to the amp board you should be okay. Touching the wires shouldn't cause any damage. The problem occurs when you disconnect the bus of wires between them (when doing the resistor mod), allowing the amp's signal input to float.

    Travis,
    Sealed boxes are definitely the easiest. You don't have to worry about matching port sizes to you box to get the right tune and airflow. I'd go with the low-Q sealed alignment for the best sound and good low-bass performance. I've never heard any complaints about this alignment.
     
  15. Brian_DR

    Brian_DR Extra

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    Ryan,

    All current (and future) versions of Rythmik amps have bleeders in them (a small portion of older amps did not, serial number before C000100). This makes the service much safer. I for one, will not have an amp without bleeders. I still think I made the right decision to ask my supplir to add them in. Imagine what it will do to me when I replace those caps [​IMG].

    The surge is a bit more complicated. Most amps without output relay have it. I would recommend to plug the power when the power switch (on our amps) is at off position. Then switch it to on position afterwards.



    Brian D.

    Rythmik Audio
     
  16. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Thanks for the info Brian. You've definitely got a great combination of power, features and value.
     

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