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Thread: 3-way JBL inspired build - 123A - 2420/2307 - supertweeter - DSP crossover

  1. #16
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  3. #18
    Senior Member Ed Zeppeli's Avatar
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    They look fantastic. How are you setting up the Xover?
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

  4. #19
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    Quote Originally Posted by Ed Zeppeli View Post
    They look fantastic. How are you setting up the Xover?
    Thanks Ed. 1250hz 12db/octave between the 123A-1 and the 2420/2307. And 8000hz between the former and the 2405. 24db on the 2420 and 12db on the 2405. I tried a bunch of different combinations. Most measured well but this one sounded most natural, I also like the wider dispersion of the 2405 so I'm crossing it slightly lower than the standard 9,5-10k. What made a big audible difference (but not so much in terms of measurements - probably since I don't have a high-end mic and anechoic chamber) was time aligning the drivers. I've never heard a big 43xx series, and while I've no doubt they sound good, a DSP controlled crossover can really make a difference here in my opinion.

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    Crossover update. 7500hz between 2420 and 2405 with a whopping 36db/octave gives the flattest on- and off-axis (both in the horizontal and vertical plane).
    Changing the slope and/or moving the crossover to anything else seems to give not as good as a response. Perhaps some minor interference issues that are absent with this steep filter.

    I will post some measurements soon enough.

  6. #21
    Senior Member ivica's Avatar
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    2420&2397 and 2405 crossover

    Quote Originally Posted by TimVG View Post
    Crossover update. 7500hz between 2420 and 2405 with a whopping 36db/octave gives the flattest on- and off-axis (both in the horizontal and vertical plane).
    Changing the slope and/or moving the crossover to anything else seems to give not as good as a response. Perhaps some minor interference issues that are absent with this steep filter.

    I will post some measurements soon enough.
    Hi TimVG,

    I have some questions:
    1. Did You apply time delay compensation between the drivers (concerning 2420&2307 delay, relative to the 2405 )?
    2. Did You try LR 24db/oct LR slope filters while applying time delay compensation)?

    regards
    ivica

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    Hi ivica

    Yes, the units are time alligned with respect to the position of the voice coils, but also with respect to ear height relative to the units (between 2307 and 2405).
    I also tried the 24db filter but there is still some interference between the 2420 and 2405 that way. I assume this there is little to be done about this since the wavelength for 7500hz is around 4,5cm, and the distance between the centre of both drivers is far greater than that. So there is bound to be some interference.

    While I'm technically not knowledgeable enough to give a definite answer, I assume the sharp dropoff (combined with the phase shift of a 36dB filter?) gives a smooth response on and off axis nonetheless. The crossover is inaudible (both are actually!) so I'm not worried I should be implementing a different filter.. although there's no harm in experimenting of course.

    Best

    Tim

  8. #23
    Senior Member bldozier's Avatar
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    great job

    the combination kind of looks delicate with out lpads on the baffle.

    did you consider a vintage electronic network, maybe a difference in sound, id like to know which you like better?

  9. #24
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    No, I just have the electronic crossover - not planning on doing passive.

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    Left and right speaker average response of a couple of measurements around the listening position. There are a couple of filters in place to dampen some resonances in the woofers. No EQ whatsoever on either the 2420 or 2405.

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    Fooled around a bit further with time alligning, gain, .. dark arts..

    While the individual response of the speakers hasn't altered much, there is now only one filter in place on both woofers to take out some excess energy, the combined sweep of both speakers has improved, and it's definitely audible.



    Couple of peaks still (keep in mind the 2dB resolution of the graph) and I will try to take care of them next weekend, and do some A/B testing to see which I like better. Thing are sounding great as-is.

  12. #27
    Senior Member ivica's Avatar
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    Quote Originally Posted by TimVG View Post
    Fooled around a bit further with time alligning, gain, .. dark arts..

    While the individual response of the speakers hasn't altered much, there is now only one filter in place on both woofers to take out some excess energy, the combined sweep of both speakers has improved, and it's definitely audible.



    Couple of peaks still (keep in mind the 2dB resolution of the graph) and I will try to take care of them next weekend, and do some A/B testing to see which I like better. Thing are sounding great as-is.
    Hi TimVG,

    Unusual sharp roll-off of 2405 (over about 14kHz).

    regards
    ivica

  13. #28
    Senior Member Ed Zeppeli's Avatar
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    Just and FYI. You can upload a jpg right from your hard drive and it will be stored here. Good thing to do as some links/photo accounts go dead in time.

    Cheers
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

  14. #29
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    Quote Originally Posted by ivica View Post
    Hi TimVG,

    Unusual sharp roll-off of 2405 (over about 14kHz).

    regards
    ivica

    I'm not worried about it. Probably a combination of the high energy loss of the omnidirectional microphone (UMM-6) I use, combined with the fact that the tweeters are about 15° off axis (vertical)

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    While I'm completely loving this system. I always try to get my hands on a spare part - just in case. Since (in terms of max SPL) the weakest link is the 123A.. Guess what I bought.


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