Consideraciones acerca de medición y ecualización

Aquí otro comentario, esta vez de Sean Olive:

I am the main author of study so I can respond to the questions.

This was a study that compared different room corrections implemented by different products applied to the same loudspeaker system: a B&W N802 and a JBL 1500 Subwoofer. The final curves you see are based on the results after the products measured, processed and applied their corrections to the speakers. We followed the manufacturers' instructions to the letter, and called one of them to get advice and clarification for best results. In some cases, we manually intervened because the product decided to cross over the subwoofer at say 150 Hz in stead of 80 Hz because the algorithm decided the B&W N802 didn't have sufficient bass to be crossed over at 80 Hz (clearly this was not the case). Some of the differences in low frequency roll-offs are based on automated decisions within the algorithm based on the output capability of the subwoofer.

We tried to be as objective as possible, and not intervene too much with how the room correction was implemented. If you read the paper we came conclusion that none of the products were refined to the point that you can rely on them to always make good decisions, and therefore some form of intervention is necessary to get the best results. That means the person doing the room correction needs some knowledge and expertise..not your typical consumer.

Some products did poorly because of the target curve they chose to use, others because they chose to do full-band EQ making the on-axis sound much worse after EQ due to filling in spectral holes in the sound power response. If a speaker has constant directivity then the on-axis/sound power response generally has similar bumps and dips and you can have you cake and eat it too. This is not the case with the B&W, which has a decent on-axis response but a less-than-perfect sound power response along with a bumpy DI. This speaker is particularly problematic for full-band blind room correction EQ as demonstrated in this study.

The lesson learned: if you start out with a decent loudspeaker with good on-axis, smooth sound power and directivity there is nothing you can to do improve it by equalizing above 500 Hz or so (below 500 Hz you have the potential to truly improve the sound at the listening seat by compensating for loudspeaker-room interactions). On the other hand, doesn't have these qualities you can do considerable harm to the speaker's sound by equalizing above 500 Hz as shown in this study. The other lesson learned is that the target curve is an important consideration.

Cheers
Sean Olive,
Senior Research Fellow, Harman X

Floyd Toole:

I don't intend to step on any response that my old friend and research colleague Sean will have to say about this, but there is a fundamental point that you have obviously missed if you have followed this thread from the beginning. There is the direct sound - the first arrival from the loudspeaker which is not - not - influenced by the room above the transition frequency, and then there is the steady-state sound that is made up of the direct sound plus reflections from off-axis sound radiated by the loudspeaker. The direct sound dictates localization - imaging, and is the dominant influence on timbre - sound quality. Reflected sounds are not irrelevant, adding mostly to spatial imaging effects, and contributing secondarily to sound quality. Over most of the frequency range the measurement by an omnidirectional microphone is a steady-state measure: a poor substitute for two ears and a brain - all of which are engaged in the perception of soundstage and imaging. This is a simplification, but it is an essential starting point to understanding why various room EQ systems differ in their results and why, unless one has detailed anechoic data on the loudspeakers, room curves cannot be interpreted.

The claim that Room EQ can turn any loudspeaker in any room into a flawless system is rubbish, but there are people who believe this. This paper, and my book explain it: Toole, F. E. (2015). “The Measurement and Calibration of Sound Reproducing Systems”, J. Audio Eng. Soc., vol. 63, pp.512-541. This is an open-access paper available to non-members at www.aes.org AES E-Library » The Measurement and Calibration of Sound Reproducing Systems

Iniciado por Deboi

Some products did poorly because of the target curve they chose to use, others because they chose to do full-band EQ making the on-axis sound much worse after EQ due to filling in spectral holes in the sound power response. If a speaker has constant directivity then the on-axis/sound power response generally has similar bumps and dips and you can have you cake and eat it too. This is not the case with the B&W, which has a decent on-axis response but a less-than-perfect sound power response along with a bumpy DI. This speaker is particularly problematic for full-band blind room correction EQ as demonstrated in this study.

En ese estudio lo que se demostró en su día es que tras ecualizar las B&W 802 por encima de 500hz (incluida la zona del bache comentado) el sonido mejoró en el blind test subjetivo

A parte, insisto en que los estudios de Floyd Toole se suelen centrar en sistemas multicanal (4.x o 5.x la gran mayoría; ya que suele ir en contra de colocar muchos más canales)... y para que cumpla no sólo en una posición fija de escucha, sino que por lo general busca en los 6 asientos/butacas que suele colocar en alrededores del centro de la sala (el criterio de una buena EQ es muy diferente si buscas buen sonido para "un único punto de escucha dulce; el típico sentado centrado en el sistema"... que si buscas prioridad se mantenga la coherencia en 6 asientos de alrededor (un espacio mucho más amplio): en éste último caso la ecualización necesaria para que en toda la banda funcione no puede ser tan agresiva como en el primer caso)



Audio Musings by Sean Olive: The Harman International Reference Listening Room

Con más detalle:




https://docs.google.com/presentation...t#slide=id.i13


Sigo sin ver tanta variedad de acústica probada: dónde están las trampas de graves y los paneles de grosor considerable colocados en las primeras reflexiones... para obtener con todo ello un RT compensado?


Porque sí, también estoy de acuerdo en que para poner paneles con esos espesores (que no actúan con suficiente eficacia hasta al menos frecuencias cercanas a la FC de la sala) mejor no poner nada porque vas a descompensar todo (de hecho, soy el primero en no recomendar ese tipo de tratamiento en los foros, porque lo he tenido y se perfectamente que ambientalmente deja la zona media y alta demasiado muerta respecto la zona media/baja y baja = muy descompensado)


Un saludete