Distributed Bass

[tomlinmgt]

I wonder about this. With many speakers the sound produced for low frequencies is so low that any harmonics might not be detectable even if the fundamental is. Isn't the amplitude of a harmonic correspondingly less than the original? And doesn't the harmonic get sent to the mains rather than the s/w? The amp/pre/crossover shouldn't be able to distinguish a harmonic in a recording from a fundamental; it's just another frequency that gets routed somewhere. On the other hand, if THE SPEAKER ITSELF is creating a harmonic when producing the fundamental, then it's entirely possible, and should be curable by using a better driver. I wonder if AK's resident Physicist could shed some light on the finer points of the relation of harmonics to fundamentals? Paging Guiller...

My sparse knowledge on this is that subsequent order harmonics are higher than the fundamental frequency by an order of two.

http://www.physicsclassroom.com/Class/sound/U11L4d.cfm

And yes, the harmonics would be sent to the mains and this is why I think some perceive first and second octave content as directional...because the harmonics associated with the (non-directional) fundamental that resides in a non-directional spectral region are directional.

 

[GuyK]

My sparse knowledge on this is that subsequent order harmonics are higher than the fundamental frequency by an order of two...

Yes, the harmonic frequency is higher, but I think the AMPLITUDE is substantially less for each harmonic, i.e. the volume is lower. Fundamental has greatest amplitude, first harmonic has less, second has less yet...I think . And a first octave note might need a second or third harmonic to become audibly directional, so this is my cause for wondering about your postulate. But I really don't know for certain, therefore my trying to summon a physicist that might be able to answer a couple of these questions.

...the harmonics associated with the (non-directional) fundamental that resides in a non-directional spectral region are directional.

Say that ten time, fast?

 

[tomlinmgt]

Say that ten time, fast?

And who said physics can't be fun?

 

[dnewma04]

let me see...from about here:

http://www.audiokarma.org/forums/showthread.php?t=626993&page=14

enjoy!

Thank you, David. That was very enjoyable.

 

[evsentry3]

I haven't had time for that other full entire thread but I'd like to make a few, perhaps unrelated to each other, points.

Harmonics of distortion are different than naturally occurring harmonics...like say of the upright bass. In distortion, a harmonic structure is seen decending as they go up. Not necessarily evenly.

I've not seen a spectrum of a plucked bass string, but I'd be surprised if the amount of and the distribution as it going up looked anything the same as distortion distribution.

A low pass filter as used for subwoofers has a slope. So even though we have say a 75hz value listed, it will have some level present higher. Both the remaining level from the crossover slope and also from distortion present in the driver itself. Looking at that from another angle would also suggest to the thinking man that some drivers might therefore have greater harmonics generated and be more audible to there physical position. Sorry if any of that was discussed, I didn't see that part if so.

I've had for many years a big Hsu sub with a cutoff listed as I think 78hz. I think it's a fourth order crossover. Dr. Hsu urged trying it center behind the listening position as perhaps working well in some rooms. Well I tried it, but I could always detect it's position even when level wise blending in properly. But just detect it's position. So using that unit, I always felt that audible localization began around that frequency.

When some years later, I was able to pick up a second matching one, I felt bass quality to the single position was noticably better quality. I greatly preferred it with two. Wonder the effect of more....?

In the linked long Harmon paper....I noticed it seemed concerned with bass quality for a group of listeners. So I found it's conclusions hard to relate to what I care about, a single listening chair in the sweet spot. I've also not caught any talk in these threads as to if the DB concept should really matter to a single listener in a single location or only those concerned with moving about or multiple people. Seems like that would also be a part of the conversation.

EV3