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Are sensitivity ratings misleading?

Discussion in 'Amps and Cabs [BG]' started by Captain Awesome, Oct 13, 2001.

  1. Oct 13, 2001 #1
    Captain Awesome

    Captain Awesome

    Apr 2, 2001
    PDX
    Usually when I look in a bass cab manufacturers' catalog or web site, their multiple 10"-loaded cabs have a higher sensitivity rating than their cabs loaded with single, larger speakers. (such as 103 dB for a 4x10 vs. 98 dB for a 1x15) I assume that the sensitivity ratings are done from a full range signal, would the percieved loudness be different for typical bass guitar usage, since I always hear about 15"s having stronger lows?

    Did my post make any sense? :confused:
     
  2. Oct 13, 2001 #2
    MikeyD

    MikeyD

    Sep 9, 2000
    It's a really good question. You should check out my other posts on this subject. I do not know of any uniform requirement for determining sensitivity. Some say that it is developed with a steady 1 kHz sine tone, and measured directly in front, on axis. That frequency would tend to be rather directional from a typical woofer diaphragm. This means it might beam rather strongly in lobes.

    The other thing that I do not know is whether these measurements are done anechoicly (i.e., with no room reflections, which would have a pronounced effect on what the meter picks up).

    Probably a fairer determiner of sensitivity would be a broadband signal (e.g., white noise or pink noise). I think part of the deal is that a 4x10 will tend to be a bit more directive at most frequencies than 1x15 (in general), which may lead to a higher sensitivity. Also, the 4x10 is probably a more efficient radiating array (has a larger radiating area) at most frequencies than a single 1x15.

    To further add confusion to the issue: sensitivity does not always equate to efficiency. Efficiency is the measure of the TOTAL acoustic power output of the cabinet divided by the electrical power going in. The total output has to include all radiation from all angles, not just the single, on-axis direction from which sensitivity is measured. SO... you might find in some cases a cabinet with lower sensitivity might be *louder* in certain ranges (especially lower ones if placed in a corner) than another cabinet with higher sensitivity. It is truly messy.

    My recommendation: (1) keep reading as much as you can about people's impressions of loudness, (2) listen to many cabinets and take notes, and (3) learn which cabinet manufacturers tend to give realistic sensitivity numbers for the applications in which you expect use their products.

    - Mike
     
  3. Oct 13, 2001 #3
    Geoff St. Germaine

    Geoff St. Germaine Commercial User

    Aug 31, 2001
    Victoria, British Columbia
    The percieved loudness will be different depending on how you eq your sound. The reason that a 4x10 has a higher sensitivity rating is based on many things, number of drivers (4 + horn compared to one), mass of the cone (a 15 in is way bigger) and frequency response. A typical 15in cab will have flatter response into lower frequencies than a 410 and as drivers become less and less efficient at lower frequencies manufacturers voice their drivers to have less response in the higher frequencies in order to maximize the bass content of the reproduced signal. As a result of this the cabs have a lower efficiency. But this is alright for bass as bass has an inherently higher bass frequency content in the signal.

    Geoff