Future woofer production

[Barleywater]

Originally Posted by planet10

Let us consider Mark's term micro-resonance.



Now in the diy audio world the term resonance brings an instant negative conotation... we want to avoid box resonance, microphonics in tubes & capacitors, room resonances etc.

But the music itself is a resonant structure (can anyone think of a musical instrument that is not a resonant device?). Matter of fact, if one puts any credance in string theory, our entire reality is the observation of low dimension standing waves of vibrations in a higher dimension universe.

From the diagram (the reality is that music is thousand(s) of times more complex), it seems clear to me that Mark's use of micro-resonance means the ability to recreate those subtle resonances in the music without them being swamped by the big ones. To me another way of saying DDR.

Mark?

dave

It seams more likely that "micro resonance" refers to small volume structures such as air in driver surround, basket windows, under dust cap along with resonance modes of diaphragm, surround and spider, all this being brought under control (not used, eliminated) by study and experimentation in design via real measurements combined with manufacturing experience.

When no one frequency has higher resonance than all others produced by driver, flat extended response is result.

Downward Dynamic range seams another way of saying reference from linear response down to floor of harmonic and IM distortion products riding above floor of thermal noise.

[silverhairbp]

Originally Posted by TiMBoZ

I think we're talking about the same thing silverhairbp. I'm just trying to nail down, understand for myself the mechanics of how we hear those characteristics you describe. Bass instruments would have upper bass and midrange resonances. Midrange instruments will have low treble resonances and so on. All overlapping up and down the frequency spectrum. I'm taking 'resonance' to mean that the driver doesn't really move, it just rings or resonates, moves a teeensy, teeensy little bit. But it also needs oscillate move a lot - all at once.

There are exceptions to just having treble harmonics over a musical note. Sometimes treble can dominate a note with harmonics above AND blow the primary note from a single instrument. Consider John Entwhistle's bass play. treble notes are the "fundamental" with bass being at a lower level supporting the note. The strike on a triangle can actually extend well down into the bass if its fairly closely miked. Depending on the voicing of a large pipe organ, treble may be a fundamental with lower harmonics.

But to my ear, there's more than just musical harmonics. It's also about how music excites a hall and creates the ambiance that defines the space in which the recording was made and the image (left-to-right and front-to-back).

I was lucky enough to be in Salzburg and attended mass during the annual performance of [IIRC] Mozart's "Dominicus Missi." Mozart supposedly wrote that piece specifically for that beautiful church. Harmonics were all over the place from a sonic spectrum perspective. Recreating that performance would require that all the glorious hall ambiance st sll those frequencies would need to be captured (within the limitations of the very finest recording equipment) and a system of very high definition, DDR, would be required to even get remotely close.

[TiMBoZ]

For example: A 'resonance' from a double bass would be articulated by an 'oscillation' of the driver becasue the wavelength is longer. The harmonics from a steel string guitar would be articulated by a 'resonance' at the driver because wavelength is short. In simole terms, I can boil it down and call DDR the micro/macro dynamics that occur at driver level.

[golfnut]

"the difference between good hifi and great hifi is what is happening 40 dB down".

I think we have two distinct effects here – both giving rise to the lack of DDR. Let me see if I can offer a physicists perspective...

The first is a muddying of the sound due to an unwanted persistence of movement – Mark described this as a resonance effect. If you think of resonance as an energy storage phenomenon this is an OK description – e.g., the energy provided by the very short term pluck of a string is stored in the strings movement and tension, and slowly radiated as sound. Such energy storage effects occurring in a loudspeaker would have the effect of smearing music out time-wise. Cabinet resonances are a good example - really muddy up the bass end. The same will occur to some degree in drivers at high frequencies where the cone ceases to behave like a piston and more like a mechanical transmission line – reflections off the surround etc. Note that these effects will not show up in distortion measurements, and probably not in impulse response measurements because they are not of long enough duration.

The second effect is due to distortion. All distortion mechanisms, when exited by more than a single tone, will produce intermodulation products – stuff at frequencies that are not present in the original signal. In complex music this results in an enormous number of distortion products with a cumulative effect not very much different from broadband noise. You will not be able to hear anything below this noise - it creates a sort of ‘noise floor’. This is an instantaneous effect – no smearing in time. Crossover distortion in amplifiers is an excellent example because it is more or less independent of the amplitude of a signal - more or less like a permanent noise floor when there is a complex signal present - low level signals disappear in an amp with a lot of crossover distortion – also why Class A amps shine at low levels, - also "the difference between good hifi and great hifi is what is happening 40 dB down".

regards

[Greebster]

Golfnut hit it on the head.

I've equated this 'noise floor' with the likes of a DBX noise reduction, wheezing a bit but not as bad as pumping this into that tangled mess of waveforms upon waveforms clouding the acoustical scene. Then SPLAT with breakup/diffraction effects galor at the driver front/rear and then that of the baffle yadda yadda yadda

seems endless at times

[markaudio]

Originally Posted by planet10

Let us consider Mark's term micro-resonance.



Now in the diy audio world the term resonance brings an instant negative conotation... we want to avoid box resonance, microphonics in tubes & capacitors, room resonances etc.

But the music itself is a resonant structure (can anyone think of a musical instrument that is not a resonant device?). Matter of fact, if one puts any credance in string theory, our entire reality is the observation of low dimension standing waves of vibrations in a higher dimension universe.

From the diagram (the reality is that music is thousand(s) of times more complex), it seems clear to me that Mark's use of micro-resonance means the ability to recreate those subtle resonances in the music without them being swamped by the big ones. To me another way of saying DDR.

Mark?

dave

Hello Dave (Guys),
I'm gradually improving healthwise although remain rather short on energy so please forgive me for typos and poor grammatical construction. My partial dyslexia is having a challenging time along with rest of me right now.

I've weened myself of the painkillers, possibly a bit too soon (ouch) as they were rather nice (spacing me out); They reminding me of rolling a certain leafy material in my mis-spent youth..hum..hum. All the same it feels real good to have enough steam in boiler to be tapping away on this keyboard.

Dave's thinking is really interesting and timely. The world of resonance and micro-resonance is fascinating. Given that every single thing (atom) in this world (possibly the whole universe) has a natural resonance, we humans have evolved to use it as an input from the outside world since our history began. In particular, our hearing is quite remarkable, such that we've learnt to recognise thousands (possibly) millions of different sound patterns over the centuries.

I think DDR is a very interesting idea and may prove useful conceptually to many audio guys. Could I possible suggest a slight change from "downward" to "low" or "lower" Dynamic Range. "Downward" might suggest to some that its a performance factor thats an applied force generated within a drivers power-train to increase LF output. That shouldn't be the case. I think LDR might be a term that maybe easier to conceptualise in this instance.

For my part, as a Mech. Eng., I'm focused on the reproduction of complex signal forms in the form of energy conversion with the most attainable efficiency over the widest possible bandwidth. This approach is more narrow, hence why I rely on qualitative feedback from members, Diyers, custom and OEM system builders; Possibly LDR might offer more qualitative user information in the future.

Forgive me chaps ending here as I'm feeling some discomfort, must do a small walk.

Cheers
Mark.

[gassit]

Look after yourself mate.

[markaudio]

Originally Posted by Barleywater

It seams more likely that "micro resonance" refers to small volume structures such as air in driver surround, basket windows, under dust cap along with resonance modes of diaphragm, surround and spider, all this being brought under control (not used, eliminated) by study and experimentation in design via real measurements combined with manufacturing experience.

When no one frequency has higher resonance than all others produced by driver, flat extended response is result.

Downward Dynamic range seams another way of saying reference from linear response down to floor of harmonic and IM distortion products riding above floor of thermal noise.

Hello Barleywater,
Apologies, only a quick reply from me. I'm specifically referring to and talking about resonance/micro-resonance in the form of emittance from the primary source, the cone. You've perhaps picked on my earlier explanations in other threads for my particular damped frame designs; But this element(s) aren't my focus of discussion on this thread.

"When no one frequency has higher resonance than all others produced by driver, flat extended response is result."
Please explain/illustrate this comment in much greater detail. Please show your research references.

Cheers
Mark.

[Scottmoose]

Presumably he's referring to the need to control / balance the amplitude of the cone resonances in order to achieve a flat frequency response.

[markaudio]

Hi Guys,
I'm filling in some time before seeing the surgeon later today. Following up on Dave's (et al) thinking regarding "Downward Dynamics" or "Low Dynamics", I've made a simple illustrative graph to assist in the discussions (see pic).

Hopefully, members and end-users can more easily appreciate the relationship between power-handling and musical detail. For those making FAST systems, it might be more challenging, should they wish to retain detail in the LF range, to find an LF driver with sufficient low mass capable of generating the micro-resonance necessary to emit detail.

Much depends of end-user project goals. If your purely into "effect" and want allot of power and have little interest in fine music, large subs become a natural choice. However, from my experience (and a very large email bag) many members and end-users aren't fully aware of the emittance limitations of large heavier mass drivers. What should be remembered is that much music in the LF spectrum is musically complex, its emittance signal is also complex, its how we differentiate between the lows of a double bass and acoustic guitar. Both might play to within a few Hz of each other, yet we hear the difference. Hopefully as health permits, I'll further illustrate these points.

Conversely, some end users fail to consider the power handling limitations of full range drivers and push them too hard. I've gone someway to help avoid breakages with the introduction of the Arrestor over-load protector. All the same, it only operates in extreme load condition and begs the question, why push a light-load driver into its distortion range where musical quality suffers.

So, issues of power and detail are important and worthy of greater research prior to making a driver choice. My hope is that this illustration will help engage discussion and promote greater planning in the goals of project building.

Cheers
Mark.