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Bgavin, techies a few questions.

Discussion in 'Amps and Cabs [BG]' started by ThunderStik, Apr 3, 2003.

  1. ThunderStik

    ThunderStik Guest

    Jun 25, 2001
    Claremore OK.
    1) T/S params are the only way we have to closely predict the way a driver will react in a given situation. My problem is the standard of 1w/1m. How linear does the response stay at half or even full power? Most of us don't just run at 1w.

    2) I was looking at the response graph between an Eminence delta12lf (56oz mag ,BL 14.1) and an Eminence omega pro12 (109oz mag and BL of 17.4) . The delta has a stronger bottom on the plot, I was thinking (correct me if im wrong) that the delta having the weaker mag and having less control over cone motion is what allows it to have a better response at low power on bottom but this is at 1w/1m. I would think that at some point the input power would "overpower" the magnets power to retain a linear response and I would think that it would not take much power to accomplish this as the mag is only 56oz. On the other hand the omega pro with a 109oz mag at 1w/1m the 1 watt would not be enough to generate enough power to put the cone into motion because of the heavy mag yielding a less than desirable plot. But at x amount of power that same mag would have much better control over the cone and things would heat up and "loosen up" actually yielding a better response than the delta 12 but only in a certain power range. Is this off base?

    3) I realize that some of this also pertains to sensitivity and how it is derived. I was just thinking that a driver could specifically built to look good at the industry standard of 1w/1m when in reality that same driver under 1/4-1/2 power will have lost all control and that plot that looked really good has now gone to crap with the driver under load.

    4) Do you find it hard to deal with that most pa's put out less bottom than your rig?
  2. Jim Dombrowski

    Jim Dombrowski Supporting Member

    Jan 16, 2002
    Colorado Springs, CO
  3. (1)
    What you are describing is power compression. Reputable manufacturers such as JBL test for PC and publish the results of running X hours at Y input power. It is specified as a dB number (reduction) from the sensitivity rating.

    PC occurs because of heat. Nearly all the power input to a driver is dissipated as heat, not as sound. When the voice coil heats up, the electrical values change. If you don't drive the cone beyond Xmax, IMO linearity is not affected, only the total amount of acoustic power the driver produces is reduced.

    The Delta 12LF and Omega Pro 12 are two different designs. The 12LF is a BB4 type with a Qts much higher than the more expensive Omega Pro 12 SBB4 type. Transient response in high Qts drivers is measureably poorer than in lower Qts types. The Omega has a 4" voice coil, so more voice coil wire is inside the magnetic gap. The Delta also requires 2x the cabinet size of the Omega. These are on-paper specs... I suspect there is probably a substantial difference in the "hearing" between the two.

    IMO the bigger bottom of the Delta 12 is coincidental. Higher quality (read: priced) drivers usually have larger magnets and voice coils. The higher BL factor usually goes hand-in-hand with a higher quality driver.

    Hard to say. Microsoft can build things that don't work, and they still make money. I think a speaker manufacturer would go broke real quick, once word got out. Drivers are built to a target market and price point. JBL and TAD pro-audio drivers are seriously pricey, and for good reason.

    In my area, all the large PA equipped venues are operated by clods who think they have to operate at 1/32 of a turn below feedback. One place has (3) 18s, (3) 15s, and (6) horns on each side of the stage. Add in a ton of monitors, and turn it all up to bleeding level.

    Even with 25 dB earplugs it is so loud I can hardly stand it from the audience position. The bands all sound distorted and none of the bassists have any pronounced, defined bottom depsite all that equipment.

    Playing outside is the real place where my rig is worth hauling around all that crap. Outdoors, it sounds deep and full... just like a real bass. My band plays with PA only for vocals. We have an El Cheapo 12" + Horn cab on each side for mains, and a pair of 12" monitors. Nothing fancy, but all it has to handle is vocals and flute/sax.

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