Off-Axis symmetry vs off-axis + listening window?

[Johnny_Mac_III]

What is the difference between these two graphs? What should I be looking for on each of the graphs? Thanks in advance.

[curtis]

What is the difference between these two graphs? What should I be looking for on each of the graphs? Thanks in advance.
It's in the description of the measurements.
"Listening window is the averaged response of 5 separate measurements, on-axis, +/- 15 degrees horizontal and +/- 15 degrees vertical."

[davef]

What is the difference between these two graphs? What should I be looking for on each of the graphs? Thanks in advance.

The Symmetry graph is comparing horizontal off-axis response to vertical off-axis response. Listening window is a standard graph and is an average of 5 measurements which better represents what you will hear from the speaker (while sitting in the sweet spot) in a typical environment compared to just the on-axis response measurement.

[Johnny_Mac_III]

Thanks! I've gained so much education from visiting this forum.

Why is there a light blue line and a yellow line for one off-axis measurement? Also, why are the yellow and blue lines together on the vertical, but slightly apart on the horizontal? Trying to learn as much as I can about measurements right now. Thanks again!

[sludgeogre]

Thanks! I've gained so much education from visiting this forum.

Why is there a light blue line and a yellow line for one off-axis measurement? Also, why are the yellow and blue lines together on the vertical, but slightly apart on the horizontal? Trying to learn as much as I can about measurements right now. Thanks again!

There's actually 4 lines for horizontal and 3 for each vertical, each one represents a different relative angle. For the Horizontal set, green is 0 degrees (the sweet spot), yellow is 15 degrees off axis, and so on according to the legend on the graph.

The reason why they deviate is because of being off-axis from the speaker. This is normal for any speaker, but the incredible thing about these measurements for sierra speakers is how the lines are right on top of each other all the way out to about 1000 Hz. This means that the critical midrange sound from the speakers is incredibly uniform in that viewing window (+/- 15 degrees). Many speakers do not exhibit that kind of performance in the critical midrange, meaning that you lose more accuracy outside of the sweet spot.

[Johnny_Mac_III]

Thanks for the reply :) I'm talking about the symmetry plots. For example: if you take a look at the +-15 degrees off axis horizontal for the HTMs, you see a blue line and a yellow line and they are slightly apart. However, if you look at the +-15 degrees for off axis symmetry vertical plot the blu and yellow lines are on top of each other. Why is there both a blue and yellow line for one single off axis plot ? Also, do measurements like these help indicate how large a soundstage a speaker is capable of?

[sludgeogre]

That just means that the vertical dispersion is a little more even than the horizontal dispersion. This is not really an indication of soundstage capability, it is more a measurement of how close the speaker sounds to it's normal sweet spot listening position as you move around the room. If you stand up while listening to the HTM you will barely notice any change in sound, but as you walk from left to right the treble response changes slightly.

As far as soundstage, the HTM's have a really surprisingly huge sound to them. I was floored compared to the crappy Klipsch bookshelves they were replacing. They really disappear as surrounds to my ears.

[davef]

Thanks for the reply :) I'm talking about the symmetry plots. For example: if you take a look at the +-15 degrees off axis horizontal for the HTMs, you see a blue line and a yellow line and they are slightly apart. However, if you look at the +-15 degrees for off axis symmetry vertical plot the blu and yellow lines are on top of each other. Why is there both a blue and yellow line for one single off axis plot ? Also, do measurements like these help indicate how large a soundstage a speaker is capable of?

This is a measurement of both vertical and horizontal symmetry. In the case of vertical symmetry, the blue lines represent the frequency response below the speaker (- degrees) at the angles listed and the yellow line represents the frequency response above the speaker (+ degrees) at the angles listed.

With horizontal symmetry, one color represents the measurement to the left of the speaker, the other is to the right. Perfect vertical symmetry is impossible to achieve in a 2-way or greater speaker (unless using a coincident driver, which presents other problems) because when you are above the speaker, the response from the tweeter will arrive before the woofer, and below the speaker is just the opposite. The fact that we achieve such good symmetry with the Sierra-1 was a rather remarkable achievement - and the original basis for the design of all Sierra line speakers (as well as the layered bamboo enclosures)

This measurement represents how accurate the imaging will be within the overall soundstage as off-axis frequency anomalies often cause problems with imaging. Many consumers confuse a large soundstage with an accurate representation of the soundstage. It is rather easy to create a large soundstage with a speaker, but this sacrifices imaging within the soundstage. The key is an accurate soundstage with proper imaging within the soundstage.

[Johnny_Mac_III]

Awesome! Thanks for the input guys! Very informative stuff.

[Johnny_Mac_III]

My CMT-340se image very well. Did you do any measurements to see when the the horizontal symmetry finnally began to fall apart on those speakers?

[davef]

My CMT-340se image very well. Did you do any measurements to see when the the horizontal symmetry finnally began to fall apart on those speakers?

Horizontal off-axis measurements are posted on the 340 measurement page. Because all drivers are horizontally aligned in a vertical array, off-axis response to the left of a 340 main will be identical of that to the right of the speaker.