2 Brahma's? What would you do?

Discussion in 'Home Theater Projects' started by JoelM, Nov 25, 2003.

  1. JoelM

    JoelM Stunt Coordinator

    Joined:
    Dec 16, 2001
    Messages:
    208
    Likes Received:
    0
    Trophy Points:
    0
    I have 2 Brahma's (15's) laying around from my car audio days and I was thinking of a 10^3 box/Sonotube tuned to 20hz with [email protected] Ohms(any amp suggestions?). I modeled it up and it seems to be a pretty nice flat response from 20hz up. Does this sound good? You see I already am pretty good in the bass department in 2 of my 3 "active" rooms.

    The Living room has 2 SVS25-31CS+'s with a Sampson1000 amp.

    The HT Room has a 4 Tempest Duel Sonotubes tuned to 16hz with 2400 watts.

    I'm hoping the 2 Brahma's will out do the 4 Tempests so I can throw them into the HT room but that is going to be close IMO.
     
  2. Dan Wesnor

    Dan Wesnor Second Unit

    Joined:
    Apr 28, 1999
    Messages:
    389
    Likes Received:
    0
    Trophy Points:
    0
    I'd put them both in one 16" cube with a Linkwitz transform.
     
  3. charles-alb

    charles-alb Auditioning

    Joined:
    Nov 23, 2003
    Messages:
    3
    Likes Received:
    0
    Trophy Points:
    0
    JoelM,

    I new to HT and was wanted to know what you thought of the SVS subs? why did you go with the passive over the powered?

    also does the 4 Tempest Duel Sonotubes sound better than the SVS's? did you custom build them? probably a dumb question but whats a sonotube? any pics? I'm looking to build or buy some subs and I really like LOTS of bass for my HT and music. any suggestions?

    thanks,
    charles
     
  4. Andrew S-

    Andrew S- Stunt Coordinator

    Joined:
    Aug 6, 2003
    Messages:
    67
    Likes Received:
    0
    Trophy Points:
    0
    I like 12 cubes tuned to 21hz a bit better than that 10 tuned to 20.
     
  5. Brian-K-Owens

    Brian-K-Owens Stunt Coordinator

    Joined:
    Feb 6, 2003
    Messages:
    194
    Likes Received:
    0
    Trophy Points:
    0
    I like - How about you send those to me, since I am still in my car audio days!!!!!
     
  6. Kyle Richardson

    Kyle Richardson Screenwriter

    Joined:
    Jan 1, 1998
    Messages:
    1,073
    Likes Received:
    0
    Trophy Points:
    0
    10 cu ft tuned to 20 will work fine. My only concern is how you are going to wire them since you mention 2000w @ 4 ohm. With 2 drivers that have dual 2 ohm coils you cannot obtain a 4 ohm load:
    .5 ohm if VC's parallel and drivers parallel
    2 ohm if VC's parallel and drivers series
    2 ohm if VC's series and drivers parallel
    8 ohm if VC's series and drivers series

    Because of this the best thing to do would be to wire the VC's in series to obtain 2ea 4 ohm loads. Wire these to each channel of a pro amp such as the PLX3002 or PLX3402 and set the amp to send the same signal to both channels from the mono input (dip switches on back allow for this).
     
  7. Phoenix

    Phoenix Agent

    Joined:
    Oct 25, 2002
    Messages:
    30
    Likes Received:
    0
    Trophy Points:
    0

    sure you can. You don't have to use both coils. just hook up one coil of each sub in series. Yes the Pmax will be reduced but it can be done.
     
  8. JoelM

    JoelM Stunt Coordinator

    Joined:
    Dec 16, 2001
    Messages:
    208
    Likes Received:
    0
    Trophy Points:
    0
    Actually you are right about me setting it up in a 2 ohm config. I've owned/built so my subs that I forgot about them being 2ohm DVC's. Maybe I'll pick up 2 of those [email protected] parts express amps for $400 each. I hit a cool 155db in my car back in the day with 2 Revo1500's(3000watts). WinISD modeled up a cool 126DB without in room factors. If I can break 130DB's I'll be happy.

    For the fun of it I hooked up my old 8^3 box from my SUV tuned to 35hz and it was crazy loud in the music department. Blew the 4 Tempests away of course it was very exaggerated and had no low-end for HT. I'm sure when I put this tune lower the output will surpass the Tempests.
     
  9. Kyle Richardson

    Kyle Richardson Screenwriter

    Joined:
    Jan 1, 1998
    Messages:
    1,073
    Likes Received:
    0
    Trophy Points:
    0
    Yes, you are correct but I dont really consider that a good option.
     
  10. Javier_Huerta

    Javier_Huerta Supporting Actor

    Joined:
    Mar 9, 2002
    Messages:
    619
    Likes Received:
    0
    Trophy Points:
    0
    Why is that, Kyle? Wouldn't simply shorting the other voicecoil result in the same T/S parameters?
     
  11. Phoenix

    Phoenix Agent

    Joined:
    Oct 25, 2002
    Messages:
    30
    Likes Received:
    0
    Trophy Points:
    0
    You don't even have to short the coil. Just leave it open. Chances are that you will run out of mechanical power handling before you reach the electrical limits of the driver so the 2nd coil is more for wiring flexibility than performance.
     
  12. Javier_Huerta

    Javier_Huerta Supporting Actor

    Joined:
    Mar 9, 2002
    Messages:
    619
    Likes Received:
    0
    Trophy Points:
    0
    If you leave the second VC open you double the Qts (or Qes, I can't remember), so the driver's sonic character changes completely.

    You'd need to short the VC so that there's some damping from it.
     
  13. DanWiggins

    DanWiggins Second Unit

    Joined:
    Aug 15, 1999
    Messages:
    324
    Likes Received:
    0
    Trophy Points:
    0
    If you use just one voice coil, you halve the BL - the Qes doubles. Of course, shorting the second voice coil lowers the Qms to be equal to the Qes, thus Qts stays unchanged.

    HOWEVER, since you halve the BL, you also lose 3 dB of efficiency. You're better off at that point running the voice coils in series and halve the power delivered, rather than halve the efficiency of the driver (easier on the amp, the driver, and lower power compression to boot).

    You can find more details at http://www.adireaudio.com/tech_papers/rdo_operation.htm .

    Dan Wiggins
    Adire Audio
     

Share This Page