Increase SPL and -3db point with equal cabinett

Discussion in 'Amps and Cabs [BG]' started by jsa0100, Apr 7, 2005.

  1. jsa0100


    Apr 6, 2005
    Does any one know how much increase in SPL
    there is by using a same type of speaker cabinett (ex. 2 x 10")
    by adding a second equal kabinett and place it nexto
    the other ? I have heard 6 db around 50 Hz.
    Also any one knows how much deeper i goes. ?

    lets say 2 systems with one 10" x 2 and 100 W vs
    another with four 10" X 2 and 100 w ?

    I do remeber when i used to play guitar :bag:
    , i could easy hear that a half stack with marshall
    did not have the same low end sound as a full or
    double stack.
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    If you use two identical cabinets you'll get 3dB from the increased radiation area and 3dB from the doubling of power capability for a total of 6dB. The extension of the system will not change appreciably unless it is a horn-loaded system. There also would be a downward shift in the baffle-step frequency, which would be perceived as an increase in mid-bass response.

    Two 2x10 will work identically to one 4x10 if they have the same total impedance load and if the drivers and total box volume and tuning are the same.

    What you heard with your Marshall was the instant 6dB increase in volume when the second cab was parallel wired to the system plus the baffle-step shift. You also would have experienced a loss of high frequency response from the increased driver spacing. Since the overall system level went up the perception was that you were getting more low end response when in fact most of the change was from losing highs.
  3. jsa0100


    Apr 6, 2005
    tnx. for a very good answare.

    Do you know why connecting speakers
    in series should be avoided. ?
    It gives a boomy sound.
    Perheps it's different if they are in
    the same box.
  4. The Clap

    The Clap

    Jan 5, 2004
    Scottsdale, AZ
    Wiring speakers in series/parallel affects the load (impedance) that;s presented to the amplifier. Two 8 ohm speakers in parallel make a 4 ohm load, and two 8 ohm speakers in series make 16 ohms.

    About the only time I'd expect to use series wiring with a guitar cab is in the case of a 4x8 4x10, or 4x12 etc. If all 4 drivers are 8 ohms, you can make the final impedance of the cab 8 ohms by wiring two speakers in parallel and two in series. If all 4 were in parallel, it would be 2 ohms, and in series, 32 ohms. As far as I know, wiring speakers in series does not make them more boomy, it just changes the impedance of the system.
  5. jsa0100


    Apr 6, 2005
    I have a speaker construction book that states:
    "Series connecting of subwoofers should be avoided
    because this could result in unpredictable controll and frequency response of the final speaker system."

    I never thought much about this, until i heard that
    series connecting speakers could give you more bass.

    I thought that series connecting vs parallell
    vould give the same sound (if the sum impedance is the samme),
    for a long time.

    Until i tried it my self.

    i series connected 2 celestion 16 ohm celestion speakers
    and then parallell
    (this tube amp had outputs for 4 - 8 and 16 ohm)

    The sound got louder on low frequency and a bit soft.
    With a transistor amp, the sound got to boomy.

    I have heard that this related to damping

    "damping" is a function of the relative resistance/impedance of the amp and speaker.

    but still can't understand why, or if this is the case. or softer
    base gives an illusion of being louder.
  6. The Clap

    The Clap

    Jan 5, 2004
    Scottsdale, AZ
    The 2 celestions in series represent a 32ohm load, and in parallel, an 8 ohm load. They will draw a lot more power for given knob-settings on your amp in parallel. 16 ohm speakers are generally made with that impedance so you can use 2 in parallel for 8 ohms. I've never tried running a 32 ohm load, but I can't imagine how it would sound better, so in this (and most 2 driver cases) you're going to want to use parallel wiring.
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    If you series wire instead of parallel you lose 3dB of sensitivity right off, so it isn't as loud, and the brain perceives that as a duller tone as. Damping doesn't really enter into it, but both capacitance and inductance do, as voice coils are not purely resistive but are inductive and capacitive as well, and series versus parallel wiring changes the systems inductive and capacitive values and that alters tone.
  8. Joe P

    Joe P

    Jul 15, 2004
    Milwaukee, WI
    Interesting... Yes, that would have to be right because when it comes to reactances, series inductances and parallel capacitances add, while parallel inductances and series capacitances decrease (according to a math function).

    ..SO... an amp looking into series speakers will see MORE inductance, and LESS capacitance than if it were looking at either speaker alone; looking into parallel drivers an amp would see INCREASED capacitance, and DECREASED inductance.

    I guess the next question would be: does a 16-Ohm speaker tend to have twice the inductance and capacitance as an eight"? -will it tend to have 4X more than a 4-Ohm? If that were the case, then if you were targeting 8-Ohms, and were trying to decide to go with two paralleled 16s, or two series'ed 4s... then
    ...Oooooo - I'm going to have to doodle a bit on that one!

    Good stuff, Bill - lookit that: you got me thinking again.