Must Center Channels Always Have Two Woofers?

[Tex-amp]

Oh, but the horizontal dispersion pattern off axis is crucial in proper reproduction whether you are fixed exactly on the center line of not. This is what research by Toole et al shows, no matter if the speaker is on the right side or in the center should not make a difference. Otherwise, off axis dispersion would be of no concern to designers.

Yes, but the off axis window is fairly wide on a good design. If you're sitting outside that area you are likely in front of one of your mains and viewing your display at quite an angle.

 

[Tex-amp]

Oh, but the horizontal dispersion pattern off axis is crucial in proper reproduction whether you are fixed exactly on the center line of not. This is what research by Toole et al shows, no matter if the speaker is on the right side or in the center should not make a difference. Otherwise, off axis dispersion would be of no concern to designers.

Yes, but the on axis window is fairly wide on a good design. If you're sitting outside that area you are likely in front of one of your mains and viewing your display at quite an angle. I'm not saying off axis doesn't contribute to SQ but that you're sitting away off to the side before it is a big issue.

 

[WmAx]

Here is what the article said. Maybe I am not understanding it right?

The original D'Appolito array was was made to improve the horizontal directivity of a vertically arrayed MTM system at the cost of some exacerbated lobing in the vertical plane. When you use a D'Appolito horizontally you radiate those worsened vertical lobes directly into the listening area instead of toward the ceiling and floor. Why is that good?

The graph that follows shows a mean off axis dips what appears to be the crossover points of these speakers.

1. I am not familar with the $ensible $ound issue you are quoting, since I do not subscribe.

2. The article part that you quoted, I can not determine the context, due to no. 1.

3. Was the sysem under test actually a D'Appolito or other network optimized for the MTM's crossover region lobing? Refer to the graphs I provided earlier, an example of a standard L-R network polar plot as well as a D'Apollito network is graphed(solid and dashed lines, respectively) on a MTM in order to demonstrate the potential difference using a D'Appolito network compared to a generic network. Refer to the graph provided in the AES paper as well, which demonstrates to slightly different effect, the reduction of vertical lobe(which btw in that example also increases directivity while also reducing the lobing) magnitude. These examples are based on the crossover point.

-Chris

 

[WmAx]

Yes, but the off axis window is fairly wide on a good design. If you're sitting outside that area you are likely in front of one of your mains and viewing your display at quite an angle.

If the viewing angles are strictly ideal, limited to a somewhat centered position, then it should not make much difference(from a direct arrival sound point of view). However, if like in many homes, the watching positions are all over the room (since most people do not arrange their HT for ideal sound, but instead arrange to fit into the existing room layout), then a typical MTM is not the optimal choice.

Also, the off axis reflections of the center channel within the room have not been considered with the horiztonally positioned MTM, another issue that must be addressed. It has been demonstated(in valid and highly credited perceptual [1]research) that the horiztonal off axis response should be similar to the on-axis response for a speaker to be rated highly in sound quality in blind trials within a normal environment(as opposed to an anechoic chamber where obviously off axis response is irrelevant).

-Chris

[1]Loudspeaker Measurements and Their Relationship to Listener Preferences: Part 2
Floyd E. Toole
JAES, May, 1986, Vol. 34, pages 227-235

 

[mtrycrafts]

1. I am not familar with the $ensible $ound issue you are quoting, since I do not subscribe.

2. The article part that you quoted, I can not determine the context, due to no. 1.

3. Was the sysem under test actually a D'Appolito or other network optimized for the MTM's crossover region lobing? Refer to the graphs I provided earlier, an example of a standard L-R network polar plot as well as a D'Apollito network is graphed(solid and dashed lines, respectively) on a MTM in order to demonstrate the potential difference using a D'Appolito network compared to a generic network. Refer to the graph provided in the AES paper as well, which demonstrates to slightly different effect, the reduction of vertical lobe(which btw in that example also increases directivity while also reducing the lobing) magnitude. These examples are based on the crossover point.

-Chris

This particular article as there are several good ones in this issue, that is why I posted references to it, is talking about the design shortcomings of a horizontal M-T-M layout, what makers claim for them, etc.
Free for the reading at Borders, most likely, next trip to a mall

The MTM you are talking about is for a vertical layout, no? The graph now would apply to the horizontal radiation pattern, right?

 

[WmAx]

This particular article as there are several good ones in this issue, that is why I posted references to it, is talking about the design shortcomings of a horizontal M-T-M layout, what makers claim for them, etc.
Free for the reading at Borders, most likely, next trip to a mall

The only issue here is what context so far as which particular lobing they are talking about, and that actual crossover toplogies used on the analysed designs, which the excerpt provided does not make clear.

The MTM you are talking about is for a vertical layout, no?

Yes, vertical.

The graph now would apply to the horizontal radiation pattern, right?

Right.

-Chris

 

[mtrycrafts]

The only issue here is what context so far as which particular lobing they are talking about, and that actual crossover toplogies used on the analysed designs, which the excerpt provided does not make clear.



quote by me:Quote:
The graph now would apply to the horizontal radiation pattern, right?

You:
Right.

-Chris

Then, do we really want that radiation pattern in the horizontal axis? Doesn't look good at all, no? So, an M-T-M horizontally is not the way to go but it seems to be convenient for fitting speakers with a TV.

 

[WmAx]

Then, do we really want that radiation pattern in the horizontal axis? Doesn't look good at all, no? So, an M-T-M horizontally is not the way to go but it seems to be convenient for fitting speakers with a TV.

Of course not, the radiation pattern, overall, is usually poor for this topology. I never suggested that a horiztonal M-T-M was suitable. I'm not sure, but judging by your response, it seems as if you may have thought I endorsed the use of these for center channel use. I tried to make it clear that I specifically recommend a system with good horiztonal radiation pattern(s), which most MTMs are not sufficient.

-Chris