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Re: The audibility of deep bass research is all wrong

Hi Richard

“Human hearing fades under 30Hz. and can be very poor by 20Hz.
But people do report feeling body pressurization from deep bass even when they don't hear a distinct tone. Surveys tend to miss that effect by asking what people "hear", rather than asking what they hear with their ears, and feel with their body.”

Yes, but the threshold of detection I mentioned is just that, “can you detect anything at all?”. It takes about 110 dB to make 3Hz audible but it then is audible / detectable.

“Even worse, surveys tend to use sine wave tones that makes harmonic distortion MUCH easier to hear, rather than using real music that masks harmonic distortion well.”

Absolutely true, a pure sine wave is certainly the “worst case”.
On the other hand, there are other signals than music, natural and environmental sounds are generally not harmonic, loud low frequency sounds can exist in movie sound tracks with little else to mask “issues”. These are more like sine waves, “naked bass”

“Complex real music may mask harmonic distortion so well that it may have to exceed 10% in a subwoofer before being noticed.”

I would say its higher than that actually. In the AV world (where powerful lf happens against a silent background sometimes), 10% is the level at which the sub is considered to be misbehaving although not unacceptably.
Not only that but if one has NEVER heard low bass without distortion, then what they hear is fine and normal right?
In the Pro-sound area 20 years ago, it was often assumed that having low frequencies simply meant the sound would become muddy.
If they didn’t cut the low end, that’s what happened.
Also about 20 years ago I invented a subwoofer driver that used a servomotor instead of a VC (Servodrive.com, although I don’t work there anymore), these were both very powerful, very low distortion and went down an octave lower than most pro-subwoofers of the day.
It was funny, the “muddiness” formerly associated with “low bass” turned out to be harmonic distortion so powerful that it interfered with the mid bass and mid range spectrum. Adding subwoofers with low distortion didn’t do that at all.

“In summary it's amazing how much harmonic distortion from subwoofers is masked by the music content. The "research" does not correlate with what people hear and feel when listening to the deep bass in (some) music. Even if a subwoofer WAS able to produce loud low distortion 20Hz. test tones, the wood frame house it was located in would most likely make noises far worse than harmonic distortion!”

Well, one could say that since what was being investigated was the “best” case situation with sine waves that the same study with some music track would actually be a different study. One can produce powerful low frequencies with low distortion, it just takes space.

Here is a current design of mine which you might get a kick out of.
It uses a new type of horn called a tapped which uses both sides of the driver radiation.
The second link explains how it works if interested.

http://www.danleysoundlabs.com/DANLEY_dts20.htm

http://www.danleysoundlabs.com/pdf/danley_tapped.pdf


One last issue which is a real problem is that it is hard to measure distortion with a dynamic signal. Loudspeaker non linearity’s get worse rapidly, many problems increase at some “power”, like they square each time the amplitude is doubled etc.
There is no standard for this, not only that, a speakers response curve often changes with level too.
“A tough steak, well done” as they say, ugh.
Back to work, happy listening

Tom Danley



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  • Re: The audibility of deep bass research is all wrong - tomservo 13:15:04 06/16/06 (0)
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