Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: 340 SE Center Orientation

  1. #1
    Join Date
    Mar 2008
    Location
    Juliette, GA
    Posts
    403

    Default 340 SE Center Orientation

    When we ordered our Ascends for our new HT, the plan was to place the center speaker behind an acoustically transparent screen. As the project progressed, various factors were discovered, such as marginal viewing distance if the screen was moved out 2+ feet to accommodate the center, that lead us to just paint the back wall and use it as our screen.

    That has worked out fine, but I had ordered the 340SE center in vertical configuration. Experimentation has shown that there is s significant difference in sound if the center is oriented horizontally, especially off axis. That left me pondering my alternatives. Here they are, listed in order of most likely to least likely:

    1. Use the speaker as is, in vertical orientation. The center sounds fine, but it is now at the bottom of the screen. Our screen is so low that vertically oriented, the speaker is only a few inches off the floor. That leads to two sub-optimum situations; the center is that much further away from the horizontal axis of the L/R mains and the tweeter and bottom woofer are further away from the actor's faces. Once you get involved in the movie, it's not noticeable, but usually at first I do notice it.

    2. "Field modify" the center to be used in horizontal orientation. This is really where my question lies. What is the difference between a horizontal center and a vertical center? Is it driver orientation or more than that? Would it be possible to rotate the tweeter 90 degrees and then have a horizontal center?

    3. Send the center back and either swap for a horizontal center or have Ascend modify it appropriately.

    4. Mount the center above the screen in a vertical orientation. I need to do more precise measurements, but I'm afraid this may either be impossible or very difficult. Horizontal placement above the screen would be do-able. Since faces are usually closer to the top than the bottom of the screen it makes sense, but since our ability to locate sounds in a vertical plane is not great, I wonder if the difference would be worth the effort.

    Any thoughts would be appreciated.

    Doug

  2. #2
    Join Date
    Aug 2003
    Location
    Manhattan Beach, California
    Posts
    7,032

    Default Re: 340 SE Center Orientation

    The orientation of the drivers between the SE's, horizontal or vertical, is the same.

    How far off center would someone be when watching a movie? You are also hearing a significant difference on axis? How far is the center from the back wall compared to the L/R?

    I would call Ascend and discuss.
    -curtis

  3. #3
    Join Date
    Mar 2008
    Location
    Juliette, GA
    Posts
    403

    Default Re: 340 SE Center Orientation

    Quote Originally Posted by curtis View Post
    The orientation of the drivers between the SE's, horizontal or vertical, is the same.
    I would call Ascend and discuss.
    Thanks Curtis. I thought that was the case. Perhaps lobing in horizontally placed WTW speakers is more than a myth. See: http://www.audioholics.com/education...peaker-designs

    The center is placed the same distance from the primary listening position as the L/R speakers. My wife can hear a timbre difference sitting in the sweet spot. She's more objective than me.

    Visitors will be sitting as much as 30 + degrees off axis. I first became suspicious when the grandkids came over to watch Star Wars. They sat in the sweet spot and we sat in the visitor's spot. Deb and I both noticed the dialog seemed low compared to music. Move to on axis and the dialog is louder.

    Since there's no orientation to the drivers, I think I'll just leave it standing vertical. I think I will call Ascend and ask what difference there is, since they do specify horizontal or vertical.

    Doug

  4. #4
    Join Date
    Aug 2003
    Location
    Manhattan Beach, California
    Posts
    7,032

    Default Re: 340 SE Center Orientation

    It isn't a myth, but a generalization.

    A "center" version of the CMT-340SE has the EXBAC circuitry...whether horizontal or vertical. A non-center version does not.

    EXBAC Defined: the front baffle of a loudspeaker creates diffraction losses as longer (lower frequency) sound waves travel along the surface of the front baffle rather then beam forward. This creates problems because these lower frequencies (usually located in the critical midrange response) are 6dB down from the higher frequencies which beam forward. Placing a loudspeaker on top of a TV amplifies these problems by effectively increasing the size of the front baffle, thus creating an effect where vocals can sound nasal and thin. Our EXBAC circuit actually compensates from these losses resulting in an incredibly clean and natural sounding midrange, even when the speaker is placed atop a TV.
    Perhaps this is causing what you are hearing if you do not have the center placed in an area that needs EXBAC.

    Definitely give Ascend a call to discuss.
    -curtis

  5. #5
    Join Date
    Feb 2005
    Location
    Minnesota, US
    Posts
    418

    Default Re: 340 SE Center Orientation

    Dave has discussed lobing and the MTM design before...so here is a link to give some background:

    http://forum.ascendacoustics.com/sho...7&postcount=10

  6. #6
    Join Date
    Aug 2003
    Location
    USA
    Posts
    5,538

    Default Re: 340 SE Center Orientation

    Hi Doug,

    Curtis is correct, that article you referenced is a broad generalization. However, if you do have people sitting as much as 30 degrees off-axis, you will be better off using the center vertically. However, as I have discussed many times, at that extreme off-axis angle, other problems become a factor that are far worse than lobing...

    Quote Originally Posted by DougMac View Post
    Visitors will be sitting as much as 30 + degrees off axis. I first became suspicious when the grandkids came over to watch Star Wars. They sat in the sweet spot and we sat in the visitor's spot. Deb and I both noticed the dialog seemed low compared to music. Move to on axis and the dialog is louder.

    What you are experiencing is not "lobing"... Dialogue is reproduced from the center speaker, music will generally come from the left / right speakers. If you are sitting as much as 30 degrees off axis from the center, I suspect you will be closer to one of the left/right speakers than you are the center. If you have configured your system for the proper levels (and it sounds like you have), if you are 30 degrees off-axis, whatever speaker you are closest to is going to sound louder and drown out the center. There is no way around this. Remember, you configured the speaker levels with you sitting in the sweet spot, anything outside of the sweet spot and the speaker levels become incorrect.

    If you are actually experiencing lobing, dialogue would be muffled with a loss of detail.

    You need to determine if what you are hearing is a lower volume level or a degradation of sound quality. The two are not the same.

    You might try moving off-axis and boosting the center channel level by 3-6dB to compensate for being so far off-axis...

    In addition, it would be helpful if you posted a diagram of your room with the layout of your speakers and dimensions.

    As an example, let us assume you are 12 feet back from the center speaker and the left/right fronts are 10 feet apart.

    On axis listeners are 12 feet away from the center and the left/right speakers are 13 feet away from the listeners. In this configuration, that 1 foot difference might result in the center being 1-2dB louder than the left/right speakers. After adjusting your speaker levels, either the left/right speakers are boosted by this difference or the center is decreased to allow equal volume at the sweet spot listening position.

    If you are 30 degrees off axis from the center (assuming the same perpendicular distance to the front wall) you will now be 14 feet away from the center and 12 feet from the nearest left/right speaker. In this configuration, that left or right speaker is now 2-4dB louder than the center and the levels you originally set further compound the problem because the center level was further decreased (or the left/right mains increased)

    To simplify that closest left or right speaker that is playing music is going to be 3-6dB louder than your speaker that is producing the vocals (your center).

    This is a far more serious problem than lobing, and unfortunately there is no simple solution. Multiple centers would be required, much like a movie theater.
    .
    .
    .
    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  7. #7
    Join Date
    Mar 2008
    Location
    Juliette, GA
    Posts
    403

    Default Re: 340 SE Center Orientation

    I've found the solution! My grandsons were over last night and we watched the great silent film "The General" by Buster Keaton. No dialog, no problem!

    Seriously, thanks for all the responses. I'll try to post a diagram or photos of the room. The difference in center speaker sound is attenuation. The attenuation is more pronounced when the speaker is horizontal. In either orientation, the dialog is clear, it just isn't as balanced with the music.

    I like Dave's idea about bumping up the center by a couple of dbs when we have guests. We don't plan to watch movies with guests that often; when we have company we sit on the porch or around the fireplace and visit. I think that's why we didn't design our HT to be more movie theater like with rows of seating. It has more of a living room feel.

    Based on your responses, the center will stay in vertical orientation below the screen.

    Here's two BTW's. The grandsons loved "The General". They are also big Charlie Chaplin fans. We watched "The General" instead of the planned feature "The Waterhorse" because when I inserted the BD of "The Waterhorse", the PS3 said it had to upgrade before it could play the movie! I had not set up the wireless feature of the PS3. Luckily, that only took a few minutes. I then started to download the update. It was going slowly, then it stopped and I had to start from square one. It turns out the update is 130 meg. We decided it would be too late to start the movie by the time the upgrade was downloaded and installed, so we went to plan B. I can now play "Waterhorse"; I'll have to have them over again to watch.

    Doug

  8. #8
    Join Date
    Feb 2005
    Location
    Minnesota, US
    Posts
    418

    Default Re: 340 SE Center Orientation

    I've found the solution! My grandsons were over last night and we watched the great silent film "The General" by Buster Keaton. No dialog, no problem!
    That's funny

    I'll try to post a diagram or photos of the room.
    I've been looking forward to seeing pics of the new room Doug!

    chuck

  9. #9
    Join Date
    Mar 2008
    Location
    Juliette, GA
    Posts
    403

    Default Here you go, Chuck

    Quote Originally Posted by chas View Post
    I've been looking forward to seeing pics of the new room Doug!

    chuck
    Here's a link to photos of the finished Home Theater. They're not great product shots of the Ascends, I wanted them to be heard, not seen.

    I did ALL the work, except for mudding the sheetrock, hanging the ceiling and laying the carpet. The rest, framing, wiring, plumbing, laying the kitchen floor, painting, etc. was done by Deb and me.

    http://picasaweb.google.com/dougbrucemac/HomeTheater

    Doug

  10. #10
    Join Date
    Feb 2005
    Location
    Minnesota, US
    Posts
    418

    Default Re: 340 SE Center Orientation

    Looks fantastic Doug...when can you start on mine?

    I love the wooden prop! Is that the furniture you got that deal on...great looking stuff...what brand is it?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •