Slow vs Fast Speakers

Discussion in 'Amps and Cabs [BG]' started by bgavin, Sep 5, 2001.

  1. The term "fast" is used a lot to describe tight, punchy response and is usually associated with 10" drivers. Conversely, "slow" is used for 15" drivers along with the terms "muddy" and "inarticulate."

    Joris if you are reading, what do you think of an aribtrary number representing the ratio of the Bl product (force) to the Mms (mass) as an indicator of tight response? It seems to me that a higher force-to-mass ratio would exert tighter control and improve transient response.

    I added a column to my Musician's Reference spread sheet for this ratio. Sorting in descending order, it is very apparent that 10" drivers have a much higher ratio (more force applied to less mass) than do the larger drivers. The first 15" driver is the JBL E-130 which doesn't surprise me, considering how efficient it is. The JBL E-140 and E-145 drivers are above both the average and median ratios, implying they are fairly punchy. The Carvin PS10 10" drivers scored much higher than average.

    I also noticed how the true subwoofer drivers are at the very bottom of the ratio. In my own rig, I noticed a signficant increase in punch when I added a pair of JBL E110s and crossed them over at 100 Hz. No mud.
  2. lemonadeisgood


    Aug 22, 2001
    ... ... it's a ring toss game.
  3. Bruce,

    interesting. I'll look into it, and get back to you. I'll have to do some good thinking to determine what the BL/Mms ratio says about a driver.
  4. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Allow me to throw the ringer in... My Peavey 115BXBW cabinet's much MUCH punchier then my Peavey 410TXF.

    Both are incredible cabinets, IMO. But the 115BXBW's VERY punchy and VERY quick.

    I think it's kind of odd how different it is from most 15"'s... It's actually quite a good cab though. Especially in combination with my 410TXF. :)
  5. Bruce, I did the thinking.

    You're forgetting one major parameter: suspension compliance. Has a huge effect on the "speed" of a speaker.

    But, if you were to take Cms into account, you'd simply have an equation that pretty much describes the theoretical efficiency of the driver. Which is

    u0= (9.64E+10*(Fs^3*Vas))/Qes


    Fs = 1/(2*pi*(Cms*Mms)^.5)

    Pleas note, Cms is not a constant. The mechanical impedance of air decreases with rising frequency. No wait this isn't true. I'm rambling. Let me know what you think of this brain storming. I believe I'm not makes much sense.

  6. I'm just in the observing stages on this thing also.

    From a data observation point of view, I sorted my spread sheet by this ratio in descending order, and notice how consistently the JBL drivers are always at or near the top. I also notice how true subwoofer designs are always at the very bottom. Efficiency is a definite factor here. But, there does not appear to be a direct relationship between "No %" efficiency and the Bl/Mms ratio.

    The efficiency formula shows how important the Fs is, due to it being cubed. Small changes in Fs result in large changes in the final result. What I'm trying to determine is if there is a predictor in the T/S data for how well a driver reproduces transients.