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Loudness vs. Power

#21
And you must factor in the sensitivity of the speaker cabinet, too.
A very efficient cabinet will be LOUD with much less power input.

Basically, you want to "pump most air" using the least amount of electricity.
A (folded) horn is a good example of high efficiency.

DEAFENING
... in dBs ...
Jet aircraft, 50 m away. . . 140
Threshold of pain . . . . . . 130
Threshold of discomfort . . 120
Chainsaw, 1 m distance . . 110
Disco, 1 m from speaker . . 100
Diesel truck, 10 m away . . 90
....
With a cabinet rated over 100 dB @1m / 1 watt,
120 dB could be achieved by the 20 dB gain from a 100 W amplifier.
....
A DR250 (with a 10" woofer) is rated at 106dB @ 1m/1 W
http://billfitzmaurice.net/DR250.html
 
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#22
jetgraphics said:
And you must factor in the sensitivity of the speaker cabinet, too.
A very efficient cabinet will be LOUD with much less power input.

Basically, you want to "pump most air" using the least amount of electricity.
A (folded) horn is a good example of high efficiency.

DEAFENING
... in dBs ...
Jet aircraft, 50 m away. . . 140
Threshold of pain . . . . . . 130
Threshold of discomfort . . 120
Chainsaw, 1 m distance . . 110
Disco, 1 m from speaker . . 100
Diesel truck, 10 m away . . 90
....
With a cabinet rated over 100 dB @1m / 1 watt,
120 dB could be achieved by the 20 dB gain from a 100 W amplifier.
....
A DR250 (with a 10" woofer) is rated at 106dB @ 1m/1 W
http://billfitzmaurice.net/DR250.html
Click to expand...

Issue with that cab, is that it starts rolling off in the low end ~150hz, and takes a HARD dive right below 100hz. Might be real punch and loud in the mid bass region, but its not going to pump out the low end like some other of Bill's designs.
 
#25
CL400Peavey said:
Issue with that cab, is that it starts rolling off in the low end ~150hz, and takes a HARD dive right below 100hz. Might be real punch and loud in the mid bass region, but its not going to pump out the low end like some other of Bill's designs.
Click to expand...
Perhaps you missed the vertical scale increments - the "hard dive" was from 106dB to 90dB at 60 Hz.
A typical front loaded speaker cabinet is 88 dB - 93 dB, on average, and also drops off the bass.
Plus, the important audio spectrum is the second harmonic and higher (80+ Hz)
... But if you want that chest crushing thump, you can add a Titan 39 subwoofer with a 12" woofer ... 97 dB at 40 Hz, thereabouts.
... Or two Titan 39's ...
However, according to the bassists that use BFD cabs, the DR250, alone, with the port, is more than sufficient.
Two cabinets are manslaughter.

Addendum: charts of a ported DR250 (10") versus a 1x12"
[Invalid or Expired Link Removed]
About 100 dB at 80 Hz
 
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#27
Personally, I like the idea of a DR200 (8" woofer) + T39 (10" woofer) for a "Concert" bass system.
Certainly get some zing when asked "Whatcha drivin'?"
But it is impractical. Tis better to have a "monitor" bass amp and run into the P.A.
 
#29
el murdoque said:
Adding a second, identical cab to your setup will usually bring a total of 6db increase, 3db from doubling the speaker surface and 3db from the increase of power from the amp due to halved impedance.
But in my experience, you get much more. There's more air being shifted around, resulting in a much fatter low end, even at lower volumes.
I learned that when i added another GS212 cab to my tonehammer500 + GS212 and suddenly had to dial back on the bass knob.
Click to expand...

This... This is exactly my experience aswell i dont see how ill ever need more than my 300 watts head(in terms of power) since i added another 4x10 to the setupd(making it a 8x10). It´s just insane, not only did i dial back the bass knob but i could almost turn back the volume by 50% and still be heard way better than before.
 
#30
Decibels are a ratio of one power level to another, they are not a quantity. A +3dB increase is a doubling of power be it from 10W to 20W or 100W to 200W. Decibels are often misused & misquoted even in textbooks & definitely by some manufacturers.

Our experience of loudness is related to the rms signal level, (similar to the average level), & not the peaks. This is relativley low compared to the instantaneous peak signal level when a string is first plucked, hence the need for a powerful amplifier so as not to clip the peaks & to retain the signal's dynamics.

Some form of compression/limiting though is wise to protect the loudspeaker & our ears. It is useful to have plenty of headroom when the lower notes suck so much power out the amp.

Some good points made in this thread.
 
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#36
jj.833 said:
Is there any psychoacoustics measuring to describe the relation between perceived loudness and frequency?

Example A:
-speaker A has 85 dB SPL/watt at 70 Hz on sensitivity magnitude
-speaker B has 75 dB SPL/watt at 70 Hz
What is 'exactly' the difference? Does it mean that the perceived loudness drops by half on B on this frequency?

Example B:
-speaker C has 85 dB SPL/watt at 500 Hz
-speaker D has 75 dB SPL/watt at 500 Hz
Perceived loudness drops by half on D at 500 Hz?
Click to expand...

Here's an explanation:
http://en.wikipedia.org/wiki/Equal-loudness_contour

704px-Lindos1.svg.png
 

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