avf111 escribió:
Yo voto a que el amigo Toole se levantó un día y dijo voy a dar la nota, y algunos picaron.
Es que, apenas leyéndolo por encima, Toole tampoco parece estar tan emocionado con la dispersión ni tan preocupado con las primeras reflexiones como nuestros queridos compañeros:
“The first requirement of any loudspeaker in a home theater is to deliver strong,
high quality direct sounds to all of the listeners. These sounds define the directions
of sounds steered to the various channels, and of the phantom images
existing between them. As can be seen in Figure 22.2, the front channels meet
this requirement with a moderate 30° horizontal dispersion. The surround
channels in the example arrangement need much wider dispersions to reach all
members of the audience shown in this example. First lateral reflections can be
useful to the front channels, and if it is desired to take advantage of them, the
dispersion requirement for these loudspeakers expands considerably. For the
direct sounds, variations over the angular spread should be minimal, but the
lack of reliable measurement data on loudspeakers makes a technical specification
of the allowable variation futile. Looking to the future, perhaps a measure
based on the difference between the on-axis response and an average over the
appropriate angular window(s) could be developed for loudspeakers in the different
roles (e.g., see listening window data in Figure 18.6). Surround loudspeakers
require a uniform horizontal dispersion exceeding that which can be delivered
by many forward-firing loudspeakers. The on-wall bidirectional in-phase design
exemplified by the product in Figure 18.19b would appear to be a good choice
for this application, although in many theater configurations wide dispersion
conventional forward-firing designs would comfortably suffice, especially if they
were aimed for optimal coverage.” (p. 502)
“The matter of side-wall reflections of L, C, and R loudspeakers warrants some
discussion because of the widespread belief that these reflections should be
eliminated as a matter of ritual. The ritual had its origins in recording control
rooms—listening in stereo—encouraged by alarmist cautions about comb filtering
(see Chapter 9) or degraded speech intelligibility (see Chapter 10) or masking
of other reflections within recordings (Olive and Toole, 1989). When examined,
none of these turn out to be problems. The real factor appears to be spaciousness
(ASW/image broadening), and the possibility that recording engineers, like
musicians, are many times more sensitive to it and the reflections causing it
than ordinary people (see Section 8.1). Even though many (but not all) recording
professionals feel that their recording work is hindered by lateral reflections,
most of them prefer to have them in place for recreational listening.
So what does one do with them in a home listening room? If the loudspeakers
have good off-axis performance, and especially if the customer likes to listen
to stereo music, my recommendation is to leave some blank wall at the locations
of the first lateral reflections from the front loudspeakers. An area with a
small dimension of at least 4 feet (1.2 m) centered on the reflection path is sufficient. Figure 16.6 shows reflected pathways for one room.
Providing reflections for the front rows is probably sufficient.
(…)
There appears to be no evidence in the now substantial literature that these
first-order lateral reflections are problems in normally furnished or the equivalent
moderately treated rooms. If the surround channels are active, it is probable
that the modest spatial contributions of these front-channel reflections will be
masked. If only the front channels, especially the center channel, are active, it
is possible that a small spatial effect may be beneficial. In the grand scheme of
things, these are factors but not the dominant factors.
It is difficult to ignore the advantages, without apparent disadvantages, of
using normal forward-firing loudspeakers with wide dispersion, good off-axis
behavior, and allowing the relevant areas of side walls to reflect. However, in a
multichannel context, this is an issue where the customer and/or the consultant
can express some free will.” (p. 504)
Cada uno que lo interprete como quiera, pero a mi me parecen pocos mimbres para construir un “sin buena dispersión no es HiFi”. Quizá Toole no es tan taxativo porque es consciente de esto:
“■ Loudspeaker AA was a two-way design, 8 in. (200 mm) woofer and 1 in. (25 mm)
tweeter (Rega model 3).
■ Loudspeaker E was a three-way design: 12 in. (300 mm) woofer, 5 in. (110 mm)
midrange, and a 2 in. (50 mm) tweeter (KEF 105.2).
■ Loudspeaker BB was a full-range electrostatic dipole, employing a diaphragm subdivided
into areas driven in a manner to approximate a spherically expanding wavefront. The
center circle, the “tweeter,” was about 3 in. (76 mm) diameter (Quad ESL-63).”
¿Cual es la diferencia en calidad percibida entre esos sistemas, 0,5 sobre 10?
Valoración de cada sistema según el tipo de música (asociado a formas particulares de grabación). Como se puede ver una buena directividad arrasa. Ah, no, espera, parece que no.
avf111 escribió:
En realidad sería interesante comprobar qué sistema en campo MUY cercano es recomendable y definitivo y quitar TODA parte de sugestión que exista, a saber ¿detectamos en PRUEBA CIEGA la dispersión o en qué medida en su caso? ¿el ajuste extremadamente plano? ¿la necesidad de conjunto EQ+sub+Trevi? –por necesidad imperiosa., o simplemente situando en el mismo sitio unas simples cajas con GRAVE SUFICIENTE y en la MISMA POSICIÓN te dan el mismo efecto.
Pues sí. Yo tengo las Trevi Killer en campo cercano, después de todo son sonido de referencia, oye, y como soy un tipo egoísta me interesaría saber qué hacer en la práctica para tener un sonido majete; qué es importante y qué accesorio. Es más, es que al parecer la escucha en campo cercano puede tener serios problemas tanto de presentación espacial como de equilibrio tonal (lo que se aprende leyendo a Toole) y me interesaría más saber cómo conseguir un buen ajuste de cada cosa que andar viendo quién la tiene más gorda.
....... fíjate si te damos ventaja 
.... como prácticamente siempre haces. 