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Thread: JBL 2245 : 10 or 12cft

  1. #16
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by yggdrasil View Post
    800Hz? IMO that will be stretching it.
    I don't think it is impossible. Look at the graph.

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  2. #17
    Senior Member ivica's Avatar
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    Quote Originally Posted by Lee in Montreal View Post
    I don't think it is impossible. Look at the graph.

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    The "problem" is "dotted-line" which is usually 45 deg "off-axis" response, or better to say,
    large driver tends to "beam". Under such you have -5dB on 800Hz

  3. #18
    Administrator Robh3606's Avatar
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    I don't think it is impossible. Look at the graph.
    I think it would be better to look here:

    http://www.audioheritage.org/vbullet...hp?10654-2245H

    Rob
    "I could be arguing in my spare time"

  4. #19
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    I'm not sure about all the different models of speakers JBL made, but there's not many places the 2245 was used as anything but a subwoofer. The 4345 used a 2245, and crossed it out at 290Hz (I think, seems like 320Hz is another figure floating around in my head), but much lower than 800Hz.

  5. #20
    Administrator Robh3606's Avatar
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    Hello Jeff

    Yes and if you look at the impedence curve in the referenced measurement you can see jogs at the dip and peak after 500Hz which is probaly why this is so.

    Rob
    "I could be arguing in my spare time"

  6. #21
    Senior Member ivica's Avatar
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    Quote Originally Posted by Robh3606 View Post
    I think it would be better to look here:

    http://www.audioheritage.org/vbullet...hp?10654-2245H

    Rob
    Unfortunately, there is no "off-axis" response, but I think it is expect-able that over 500Hz, off-axis response stat to 'decline'

  7. #22
    Senior Member 1audiohack's Avatar
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    Build the 12 ft³ version, that way when you get your fingers out of your ears after your primary listening experience you will have the real-estate to add a dog box and a 10" or 12" driver.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  8. #23
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    I always find it odd that many people worry about off axis response but when they build a listening room, the seating position is always smack on axis.....

    Allan

  9. #24
    Senior Member Eaulive's Avatar
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    Quote Originally Posted by Allanvh5150 View Post
    I always find it odd that many people worry about off axis response but when they build a listening room, the seating position is always smack on axis.....

    Allan
    Yes, swet spots sucks, and if the "direct / reflected of the walls" combination is important to you, then it becomes important.
    My avatar: 4520 loaded with 2225H on E140 frames,
    1x 2202H on custom front loaded horn, 2x 2426 on 2370.

  10. #25
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    Quote Originally Posted by Eaulive View Post
    Yes, swet spots sucks, and if the "direct / reflected of the walls" combination is important to you, then it becomes important.
    Who mentioned a sweet spot? I just do not recall any listening rooms where the speakers are pointing at some angle.

    Allan.

  11. #26
    Senior Member ivica's Avatar
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    Quote Originally Posted by Allanvh5150 View Post
    I always find it odd that many people worry about off axis response but when they build a listening room, the seating position is always smack on axis.....

    Allan
    May be for some other members it would be interesting to read Dr. Earl Geddes paper which is dealing with the Speaker Directivity

    http://gedlee.com/downloads/directivity.pdf

    and this too:

    http://decoy.iki.fi/dsound/ambisonic...Kates_1980.pdf


    For my personal experience: I do not like to "directiv" speakers

  12. #27
    Administrator Robh3606's Avatar
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    Who mentioned a sweet spot? I just do not recall any listening rooms where the speakers are pointing at some angle.
    Do you mean facing straight ahead with no toe in towards the listener?? Mine sure are. I have toe in on all three of my fronts and my mains for the stereo rig.

    Rob
    "I could be arguing in my spare time"

  13. #28
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by Allanvh5150 View Post
    I just do not recall any listening rooms where the speakers are pointing at some angle.
    I am surprised you haven't previously seen listening rooms with speakers angled toward the listener's seat. I've been doing it for the past 30 years and as far as I remember, I even think it is how most systems are installed. After all, isn't it what "on-axis" is about?

    Back to the 10 vs 12cft topic, I managed to grab a simulation "software" to work on my Mac. Basically, nothing more than an Excel spreasheet but good enough. The difference between 10 and 12cft is not more than perhaps 2 Hz in F3 and Fb, reduced 50Hz SPL and increased excursion when feeding 350w.

  14. #29
    Administrator Robh3606's Avatar
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    I managed to grab a simulation "software" to work on my Mac.
    That's the point I was making. It took you what 5 minutes if that to find the answer you were looking for.

    Rob
    "I could be arguing in my spare time"

  15. #30
    Senior Member Lee in Montreal's Avatar
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    Quote Originally Posted by Robh3606 View Post
    That's the point I was making. It took you what 5 minutes if that to find the answer you were looking for.
    Actually, it gave me some clues, but didn't answer all my interrogations. Per exemple, the ports is de facto tuned to Fb. I can't find how to tune the port to the driver's Fs 20Hz, or somewhere between Fs and Fb.

    So far it goes like that. 10cft vs 12 cft tuned at Fb 27,3Hz

    Response. The thin green line is the gain/loss between 10 and 12 cft

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    Excursion at 350w

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