Gran decepción con el Pioneer LX86

Iniciado por imported_HUESO

Con unos cascos (HD 598) y utilizando la salida de cascos de tres aparatos distintos (reproductor de CD´s, Amplificador A/V y tarjeta de sonido externa) el sonido percibido después de igualar niveles y reproduciendo la misma pista, al pasar de uno al otro es "claramente distinguible", y se tarda 3 segundos de cambiar de una a otra salida lo puede hacer cualquiera y las conclusiones son claras. Y esta simple prueba no deja de ser una comparativa de tres "minusculos" amplificadores sonando en la misma sala y con las mismas cajas

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La prueba de auriculares que comentas no tiene nada que ver con el caso entre cajas. Los auriculares suele trabajar con impedancias bien diferentes a las de las cajas (entre algunos sistemas sí podrían notarse diferencias dependiendo de sus propias salidas de headphone, ya que la curva de respuesta en frecuencia sí cambiaría lo suficiente como para ser claramente audible).

A parte de lo comentado, tampoco se puede comparar la coloración propia del mejor sistema cajas/sala con la de un auricular "suficientemente bueno"; en el caso del auricular es mucho menor... luego el límite de la detectabilidad de diferencias tampoco es el msimo en ambos casos.

Por otro lado, en matrixhifi se han realizado cambios entre fuentes bajo auriculares y los resultados son los comentados; si hay diferencias audibles las hay medibles y éstas son lo suficientemente marcadas como para que el oido humano las pueda detectar.

De hecho, el sistema de auriculares es el que se utiliza para por ejemplo conocer los límites de audibilidad de THD e IMD. Los resultados tras ello son tajantes de lo "sordos que somos ante éste parámetro" :

The Results

While it is has been recognized for years that human hearing is not very sensitive to low bass frequencies, which must be reproduced with much more power and intensity in order to be heard, what these results show is that our detection threshold for “noise” (made up of harmonically related and non-harmonically related test tones) is practically non-existent at low frequencies. (The “noise” test tones are noise in the sense that they are not musically related to tones commonly found in musical instruments.) In fact, the “noise” tones at 20 Hz and 40 Hz had to be increased to levels louder than the music itself before we even noticed them. Put another way, our ability to hear the test frequency “noise” tones at frequencies of 40 Hz and below is extremely crude. Indeed, the results show we are virtually deaf to these distortions at those frequencies. Even in the mid-bass at 280 Hz and lower, the “noise” can be around -14 dB (20% distortion), about half as loud as the music itself, before we hear it.


Conclusion

Axiom's tests of a wide range of male and female listeners of various ages with normal hearing showed that low-frequency distortion from a subwoofer or wide-range speaker with music signals is undetectable until it reaches gross levels approaching or exceeding the music playback levels. Only in the midrange does our hearing threshold for distortion detection become more acute. For detecting distortion at levels of less than 10%, the test frequencies had to be greater than 500 Hz. At 40 Hz, listeners accepted 100% distortion before they complained. The noise test tones had to reach 8,000 Hz and above before 1% distortion became audible, such is the masking effect of music. Anecdotal reports of listeners' ability to hear low frequency distortion with music programming are unsupported by the Axiom tests, at least until the distortion meets or exceeds the actual music playback level. These results indicate that the “where” of distortion—at what frequency it occurs—is at least as important as the “how much” or overall level of distortion. For the designer, this presents an interesting paradox to beware of: Audible distortion may increase if distortion is lowered at the price of raising its occurrence frequency.

Next episode: The effects of harmonic distortion

The tests done in this experiment are essentially noise tests; things such as mechanical resonances and port noises that are not harmonically related to a specific fundamental contained in the music would be examples of noise distortion. Other types of distortion such as Harmonic Distortion and Intermodulation Distortion have a direct relationship to a frequency being reproduced as part of the music. These types of distortion may be harder to detect than straight noise distortion; a subject for a future round of experiments

http://www.axiomaudio.com/distortion

Luego con este artículo (ver también gráficas adjuntas) ya eliminamos por completo la diferencia que pudiera haber entre THD en el 99% de los amplificadores y fuentes del mercado. Al igual que en este parámetro, se conoce los límites de audibilidad en otros tantos.




Un saludete