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Thread: Vertical alignment of speakers

  1. #1
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    Vertical alignment of speakers

    I have been told it is allways favoured to vertically align the individual woofers and drivers on a baffle.
    As I understand this is to avoid lobing and getting the individual sources to match up better and improve imaging.

    A speaker like the JBL S9900 follows this aproach, but the JBL Everest DD66000 or DD67000 doesnīt.
    The Everest speakers only use one of their 15" woofers to run up high to the horn. So the center of the "midrange-woofer" isnīt vertically aligned with the center of the horn. It is offset by about 8".
    I wonder how this affects the overal presentation?
    Is this considered to be a major tradeoff in this speaker-layout or is the offset of such small amount that it doesnīt really affect the sound?

    Best regards,
    Olaf

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    Anyone

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    Member jmpsmash's Avatar
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    I am guessing it has to do with comb filtering. once we have separated driver, there will be combfiltering. the question is whether it should happens on the horizontal axis or vertical axis. comb filtering will happen at the overlapped crossover region.

    if we have ppl sitting on a couch, we have more listeners separating horizontally and not vertically. so drivers are aligned vertically for that.

    as for the DD67000, they probably trade off some aesthetics. otherwise the speaker will be L shaped. Now why didn't they put everything vertically, like the K2 9500, that's another question, perhaps for the marketing department.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Dr.db View Post
    I have been told it is allways favoured to vertically align the individual woofers and drivers on a baffle...

    ...I wonder how this affects the overal presentation?
    I wonder too. I made a smaller but similar trade off with my own speakers. I am sure that a vertical alignment is better, but is it actually audible? If audible how much of an impact does it make? On the DD66000/DD67000 speakers Greg Timbers was able to get JBL to spend a fair amount on making the woofers swappable so the extended range woofer was always inboard, and the manual explains that the extended range woofer should be inboard. Obviously being offset does make a difference.

    If I was younger and had more time I'd explore the question, but these days, I'd rather listen to the music.

    I'll say this, I enjoyed the heck out of the DD66000/DD67000 speakers... warts and all. These days I'm enjoying my own speakers with their own warts etc.


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    Senior Member RMC's Avatar
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    Hi Olaf,

    I think the following may answer why a vertical alignment of drivers:

    "The second rule is: put the drivers in a vertical line with little or no horizontal displacement. When speakers are mounted side-by-side, there will be a difference in the path length from each speaker to the listener's ears, producing phase distortion. Sometimes lack of space makes side-by-side mounting inevitable." (David B. Weems, Designing, Building and Testing Your Own Speaker System, 4th ed. p. 26).

    I know, some JBL 43 series monitors for example have drivers that are not vertically aligned.

    Some companies seem to put more emphasis on phase issues than others (not a judgement about JBL's practices). However, Widget's questions do remain relevant in my view. Best regards,

    Richard

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    Thanks a lot for your comments!

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    Administrator Robh3606's Avatar
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    As I understand this is to avoid lobing and getting the individual sources to match up better and improve imaging.
    It does and if you have any doubt listen to a 4311/L100 vs. 4410/L80t as examples. The 4311's are not mirror imaged and not aligned and the imaging suffers compared to the mirror imaged and vertical designs. Look at the polar response plots of the non aligned speakers and you see just how different they are left vs right. Take a look at the differences between the left and right at 20 degrees


    http://www.jblpro.com/pub/obsolete/4411.pdf

    Rob
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    I have to come back to the Everest DD66000 or 67000 with itīs dual woofers.
    Swapping the extended range woofer to the inside makes sense... But they could have avoided this hassle by simply placing both woofers in a vertical line instead of horizontal.

    As Rob pointed out it makes a noticeable difference...

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    Quote Originally Posted by Dr.db View Post
    ... But they could have avoided this hassle by simply placing both woofers in a vertical line instead of horizontal.

    As Rob pointed out it makes a noticeable difference...
    It's not necessary to vertically align the 2 woofers as the wavelengths are so large you'd never hear a difference between vertical/horizontal mounting. However it would have completely changed the design of the speaker from other aspects including aesthetics. Everything is a compromise.

    The mid woofer being off center could effect things at crossover to the horn, but I assume dispersion at crossover is still similar and/or time alignment is addressed in the crossover, although we know GT now runs his active.

    Some speaker builders offset the driver(s) to reduce cabinet diffraction. Nothing is absolute.
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    This is probably a better example of offsetting drivers to reduce diffraction.
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    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Dr.db View Post
    I have to come back to the Everest DD66000 or 67000 with itīs dual woofers.
    Swapping the extended range woofer to the inside makes sense... But they could have avoided this hassle by simply placing both woofers in a vertical line instead of horizontal.

    As Rob pointed out it makes a noticeable difference...
    I have spend considerable time with an Everest DD67000 user trying the reversal of the woofers and other adjustments.
    It really depends on the listening room and how the enclosures are located relative to the side walls and rear wall.

    The effect is not a deal breaker but l generally preferred the main woofers on the inside.
    There are far less subtle issues that will effect the overall performance of a system of this caliber.
    The challenge with a system like the DD67000 is setting it up properly from the get go.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Dr.db View Post
    I have to come back to the Everest DD66000 or 67000 with itīs dual woofers.
    Swapping the extended range woofer to the inside makes sense... But they could have avoided this hassle by simply placing both woofers in a vertical line instead of horizontal.
    Yes, they could have, but did they want to build another M9500? To make the aesthetic statement they wanted to go with, they had no choice but to go with side by side woofers, and due to the size of 15" drivers, they had to be offset.

    In my project, I could have perched the ET-703 up top on a mast or other appendage or extended the cabinet top above the horn and vertically align all of the drivers... during my development phase I did test these various physical layouts prior to construction. I found the sonic trade off to be minimal and wanted a particular aesthetic direction.

    As many of us have said numerous times on this forum, loudspeaker design is all about compromises.


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    Quote Originally Posted by rusty jefferson View Post
    It's not necessary to vertically align the 2 woofers as the wavelengths are so large you'd never hear a difference between vertical/horizontal mounting.
    Thatīs a very interesting approach!
    Do you have any idea of where about the threshold is? Like more than half a wavelength at crossover of vertically missalignment is noticeable...!?


    Quote Originally Posted by Ian Mackenzie View Post
    I have spend considerable time with an Everest DD67000 user trying the reversal of the woofers and other adjustments.
    It really depends on the listening room and how the enclosures are located relative to the side walls and rear wall.
    Swapping the left and right woofers probably affects the room-reflections in particular. I guess it wouldnīt have any effect on the vertically missallignment, since both woofers are off center by the same amount...


    Quote Originally Posted by Mr. Widget View Post
    Yes, they could have, but did they want to build another M9500? To make the aesthetic statement they wanted to go with, they had no choice but to go with side by side woofers, and due to the size of 15" drivers, they had to be offset.
    I have to admit the horizontally mounted dual 15īs look very formidable! With a speaker being this size you canīt ignore the aesthetics, I get that.

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    Administrator Robh3606's Avatar
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    Hello Rusty

    It's not necessary to vertically align the 2 woofers as the wavelengths are so large you'd never hear a difference between vertical/horizontal mounting. However it would have completely changed the design of the speaker from other aspects including aesthetics. Everything is a compromise.
    Well that is a conditional statement that depends on how the woofers are set-up. The Everest only uses the second woofer up to 150Hz so no issues. Now if you ran both woofers over the same range up to the horn then you would have significant issues off axis. All you need to do is look at one of the dual 15 cinema boxes and you can clearly see some real issues in the Vertical axis. If you lay the box on it’s side like the Everest woofers are set up its going to make it very hard to get them to sound right. After about 20degrees or so it quickly starts to degrade the off axis response.

    If you compare the polars in the 4638 you can see how much better the horizontal polars are with a vertical alignment A good argument for setting up the woofers in a vertical vs side by side if running full range.

    Rob
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    Hey Rob,

    Agree completely. It's because the 2nd woofer is playing so low I made the comment.

    The helper isn't technically doing subwoofer duty, but it's similar enough. No need to vertically align our subs. In some cases they are many feet away from a midwoofer.

    I am curious about the midwoofer/horn alignment. I've never heard these speakers.

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