Hi,
I am looking for a set of loudspeaker performance characteristics which define the technical requirements necessary to be achieved for the correct delivery of the timbre, response and dynamics of real percussion instruments.
For example a kick drum would require a certain dB SPL, displacement, transient response of X etc...
Comparisons of different enclosure types also welcome... sealed vs ported is well known, but aperiodic, transmission line, horn?
Thanks
I am looking for a set of loudspeaker performance characteristics which define the technical requirements necessary to be achieved for the correct delivery of the timbre, response and dynamics of real percussion instruments.
For example a kick drum would require a certain dB SPL, displacement, transient response of X etc...
Comparisons of different enclosure types also welcome... sealed vs ported is well known, but aperiodic, transmission line, horn?
Thanks
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No Helmholtz resonator (normal bandpass or bass reflex) can reproduce a kick drum with any fidelity. The air inside the enclosure will compress from the transient non sinusoidal signal and the port takes several periods before it reaches full amplitude. Horns or quarter wave resonators does a much better job of sharp nonlinear transient signals.
A large closed box or open/infinite baffle with large enough Sd, low mass, low Qts, low Le and high Bl drivers can do a decent job, but I prefer horns for high fidelity reproduction of drums.
The waveform from a kick drum is not a linear or sinusoidal. Not even close. The loudspeaker must be capable of reproducing an offset asymmetric signal
True - could be classed as a loudspeaker/woofer question, rather than subwoofer.
It's not just a function of frequency response though, and that's partly the reasoning behind my question - Manufacturers commonly just provide a low frequency response value, say -6dB at 21 Hz - but it tell's you very little about the actual sound delivered.
Circlomanen's comments are interesting, and new info for me to digest - I have never heard of offset asymmetric signal before...
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The nonlinear physics of musical instruments - IOPscience
Interesting read about the nonlinear acoustic nature of most instruments.
Interesting read about the nonlinear acoustic nature of most instruments.
Low frequency response won't tell you much. Asymmetrical signals are common, I don't know what is meant by offset
Another interesting thing to note is that the source recording has a huge influence. IE close mic'd kick vs overheads. Totally different animals. Add huge EQ and compression and while it may sound better it does not sounds like a "real drum".
Horns all the way. Life long drummer... IMO a good mid bass horn is essential for percussion. Most people erroneously focus on low end and subs... Percussion rules the mid band. Load them with the most sensitive drivers you can get your hands on.
Horns all the way. Life long drummer... IMO a good mid bass horn is essential for percussion. Most people erroneously focus on low end and subs... Percussion rules the mid band. Load them with the most sensitive drivers you can get your hands on.
If it were possible to characterise a 'sound signature' from a bunch of performance measures then the whole industry of speaker design would be entirely different. Much of the art would suddenly be taken out.
I do not see this happening anytime soon.
In short - there is little you can look at in a set of specifications on a driver that will give you any clue as to how it will sound
I do not see this happening anytime soon.
In short - there is little you can look at in a set of specifications on a driver that will give you any clue as to how it will sound
If we keep away from the breakup modes of the driver cone or diaphragm, then I don´t agree at all.
A high Mms, high Qts, low Sd, low Fs and low Bl driver will tend to flatten everything into sinusoidal wave forms. It will tend to sound resonant, droning and devoid of detail.
A RCF L12P110K in a large front loaded horn will sound detailed, punchy and more organic lifelike due to a superior ability to reproduce nonlinear and non-sinusoidal waveforms.
I had a wee look at the physics of drum waveforms only to be confronted by the hideous 'Bessel Function'! However, I've managed to distill the physics down to the following:
A stretched string can vibrate at its fundamental frequency (fo) and integral multiples thereof (e.g. 3 x fo and 5 x fo).
The equivalent for a stretched drumskin is the fundamental frequency (fo) and non-integral multiples thereof (e.g. 2.962 x fo and 3.6 x fo).
Whereas the harmonics of the string follow a linear progression, the harmonics of the drum skin follow a non-linear progression, so the musical properties of the two are very different.
To complicate matters, a drum skin vibrates in competely different ways if not struck exactly it in the centre - no wonder its waveform is so difficult to reproduce!
A stretched string can vibrate at its fundamental frequency (fo) and integral multiples thereof (e.g. 3 x fo and 5 x fo).
The equivalent for a stretched drumskin is the fundamental frequency (fo) and non-integral multiples thereof (e.g. 2.962 x fo and 3.6 x fo).
Whereas the harmonics of the string follow a linear progression, the harmonics of the drum skin follow a non-linear progression, so the musical properties of the two are very different.
To complicate matters, a drum skin vibrates in competely different ways if not struck exactly it in the centre - no wonder its waveform is so difficult to reproduce!
Looks like this might be the best answer to my question at present...
I was mainly thinking about the basic performance criteria of a speaker, rather than individual drivers e.g. what headline parameters would indicate favorable performance? Am grateful to Circlomanen for the insight.
That sounds reasonable!
To adequately reproduce percussive sounds, a loudspeaker system must have an excellent transient response, not only to high frequencies but also to low frequencies.
In other words, the sound must start and stop without inducing ringing or resonance in the driver or its enclosure.
Several factors influence the transient response of a loudspeaker system:
- The strength of the speaker magnet.
- The cone and surround materials.
- Damping of resonances in the cone.
- Damping of resonances in the enclosure.
Recording technique, sound engineer skills, playback SPL and listening room modal resonance signature each alone have more influence on objective impression on the listener than all other electro-mechano-acoustical parameter of loudspeakers togerher.
There is no single parameter of loudspeaker which define one particular physical property of radiated sound. Usually there is whole co-working set of parameters.
In order to bring kick drum most into the reality it need to be played in propertiary damped environment using non-resonant, low-order acoustical allignment with low-Q high-pass transfer function (matched to particular room gain) so that listening seat-measured response keeps constant level down to infrasound. This system should be capable of non-compressed output at the level of +/-1 Pascal differential pressure level in order to properly define assymetrical pressure wavefrom typical from live kick-drum.
There is no single parameter of loudspeaker which define one particular physical property of radiated sound. Usually there is whole co-working set of parameters.
In order to bring kick drum most into the reality it need to be played in propertiary damped environment using non-resonant, low-order acoustical allignment with low-Q high-pass transfer function (matched to particular room gain) so that listening seat-measured response keeps constant level down to infrasound. This system should be capable of non-compressed output at the level of +/-1 Pascal differential pressure level in order to properly define assymetrical pressure wavefrom typical from live kick-drum.
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There is some transference of meaning with the term non-linearity going on. Everything quoted is valid but not necessarily applicable. Shockwave theory and non-linear acoustics certainly do apply inside wind instruments (and probably at the drum head), but in the far field at humanly tolerable SPL's air is quite linear and the non-linear propagation no longer applies. How a sound is created has little to do with the eventual perception.
BTW yesterday I was <5' from a pipe and drum brigade, pure heaven.
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