RAAL Horizontal and vertical off-axis graphs

[Sivar]

I'm evaluating whether to pay for the RAAL tweeter upgrade (those are some seriously expensive ribbons -- more than even SEAS Beryllium tweeters!).

One chart of serious concern is here (http://www.ascendacoustics.com/pages/products/speakers/SRM2/srm2meas.html):

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It looks like volume drops precipitously above and below just a 5° angle from the tweeter. \
I have heard that ribbon tweeters have a strong tendency to be very directional (though the Carver speakers I've heard have no such problems).
It can't be this bad though, so how am I misinterpreting the graph?

For comparison, look at the chart for Ascend's soft-dome tweeterhere (http://www.ascendacoustics.com/pages/products/speakers/cmt340m/cmt340mmeas.html).

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Notice that the Y-axis varies significantly between 5°, 10°, and 15° but that it does not for the RAAS.
Does this mean that the RAAS tweeter less affected by listening angle than the soft dome tweeter? Is this some new magic ribbon technology, or am I misinterpreting again?

[curtis]

The RAAL has exceptional horizontal off-axis response, and Dave worked hard with RAAL do get the vertical response where he wanted it...and then some.

You are also looking at the CMT-340, which is MTM (mid-tweeter-mid) design, in which, has different vertical dispersion characteristics than that of a TM design (Sierra 1/2).

So, in addition to two different tweeters, you are looking at two entirely different speakers all together.

Sivar...where are you located? Perhaps you can find an Ascend owner in your area for a listen.

[Sivar]

Sivar...where are you located? Perhaps you can find an Ascend owner in your area for a listen.
Curtis,

Thank you for the reply. I guess that's why the RAAS tweeters cost as much as a nice set of speakers -- ribbons without the downside of ribbons.

I understand that I was looking at different speakers altogether, but it was the first cone speaker graph I found so I just went with it. In retrospect, that's not unlike comparing the same engine in a Toyota Camry and a Lotus Elise. Not very valid.

Is the RAAL vertical off-axis response "just fine" for a home theater for listeners of significantly varying heights? I understand that vertical position varies less than horizontal, but there are different chairs, sometimes guests like to sit close, etc..

I am located in Pocatello, ID. I would be surprised to find an Ascend owner nearby, but if one does exist, I would love to give them a try.

[curtis]

Is the RAAL vertical off-axis response "just fine" for a home theater for listeners of significantly varying heights? I understand that vertical position varies less than horizontal, but there are different chairs, sometimes guests like to sit close, etc..

Not knowing your layout, how far from speakers would people be sitting? How many feet vertically off-axis could someone possibly be?

[davef]

Sivar,

With regard to vertical off-axis response, the S2 measurements are actually exceptional. You are looking at +/- 3dB at 10 degrees off-axis with a very small "knee", which would be barely audible in the real world... Please compare to other vertical off-axis graphs for TM style speakers (tweeter-woofer).

How far back will you be seated from the speakers?

Keep in mind, that at 10 feet back and with an accurate listening window of +/- 15 degs, you have a ~5.5 foot high vertical listening window. Which means if you set the speakers at ear-level while you are seated, whether you are seated, standing, or even sitting on the floor, there will not be an audible difference in the highs and mids (at least attributed to the vertical off-axis response). Room response will be more of an influence, and this would be the case for any loudspeaker...

[Sivar]

Sivar,

With regard to vertical off-axis response, the S2 measurements are actually exceptional. You are looking at +/- 3dB at 10 degrees off-axis with a very small "knee", which would be barely audible in the real world... Please compare to other vertical off-axis graphs for TM style speakers (tweeter-woofer).

I appreciate the reply. This may sound clueless of me, but I am really not confident in my interpretation of most charts of speaker metrics. I thought I was, but I've read so much about their interpretation that I don't know anymore.

Would you personally recommend them over Sierra 1's as surrounds? They cost a lot more, but perhaps off-axis will be no more a problem than with Sierra 1's and perhaps they will match better with the RAALs in the other speakers.


How far back will you be seated from the speakers?

I posted an image of my room in this thread (http://forum.ascendacoustics.com/showthread.php?5776-Help-with-my-home-theater-plan-(placement-component-choice-room-problems)).
As you can see, the room is non-ideal. In the uncommon case of someone sitting on the loveseat, if the speakers are high enough on the wall to clear their head, I bet they could get 70° off vertical axis. I don't honestly have a clue how much of a problem this is, or whether I am approaching things in the wrong way, etc..

[davef]

Would you personally recommend them over Sierra 1's as surrounds? They cost a lot more, but perhaps off-axis will be no more a problem than with Sierra 1's and perhaps they will match better with the RAALs in the other speakers.

For the majority of customers, Sierra-2 as rears is overkill. However, if you intend to listen to a lot of multi-channel audio - The two's are the best choice as rears with Sierra Ribbon Towers as fronts.




I posted an image of my room in this thread (http://forum.ascendacoustics.com/showthread.php?5776-Help-with-my-home-theater-plan-(placement-component-choice-room-problems)).
As you can see, the room is non-ideal. In the uncommon case of someone sitting on the loveseat, if the speakers are high enough on the wall to clear their head, I bet they could get 70° off vertical axis. I don't honestly have a clue how much of a problem this is, or whether I am approaching things in the wrong way, etc..

70 degs off vertically is very significant, are you sure about this? Let me know at what height you plan to mount the rears and what the distance would be from each of the rears to the main listening position.

[Sivar]

I had a picture in my head where the surrounds would be on or near the ceiling, which would make positioning much more challenging. Curtis pointed me to the Dolby and THX guidelines which seem far easier to deal with. I guess I have a lot of friends with strange setups.
As you know, I ended up ordering Sierra 2's as surrounds. It was probably not the most frugal choice, but I was concerned that a sonic difference between the soft domes and the ribbons would bug me, even if such a difference were purely a product of my imagination.
I don't upgrade speakers often, so I played it safe.

Thank you for all of your assistance with my questions. If you know how much I have researched audio equipment over the years, you would I hope find it quite a compliment that such rigorous researche resulted in an Ascend purchase.