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Thread: So How Can an Active Crossover Really Outperform a "Tweeked" Passive Crossover?

  1. #1
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    So How Can an Active Crossover Really Outperform a "Tweeked" Passive Crossover?

    I've been doing up the crossovers for the surround speakers. All four will use the W10GTI and 2425Js. The front presence surround speakers will use the JBL 2370 horn (that will hang under the cabinet) whereas the rear surrounds will probably use the P-Audio PH-230 (semi-simulated butt cheeks) that will just fit within the existing cabinet).

    Aftr doing up the crossovers with the 2370s, I connected the PH-230. Using the same crossover for both horns yields totally different response curves even with the same drivers. However, by going in and altering the resistor values in the crossover that change various aspects of the overall curve (quite a bit I might add), I can get both horns to a fairly consistent curve.

    I'm not referring to the low frequency roll off from the horn to the woofer, but rather roll offs, dips, and peaks at various frequencies due to horn shape and irregularities in the driver and horn response patterns.

    How could one hope to modify these simply by changing the low frequency roll off point and curve as is done with an active crossover?

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    Administrator Robh3606's Avatar
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    You could do it with a Digital Loudspeaker Management system but analog won't give you enough flexibility unless you have a Multi band Parametric EQ in there as well. With the combination of the crossover and the EQ you might be able too get things a bit better.

    After doing up the crossovers with the 2370s, I connected the PH-230. Using the same crossover for both horns yields totally different response curves even with the same drivers.
    What is the surprise there???

    Rob

  3. #3
    JBL 4645
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    Quote Originally Posted by Robh3606 View Post
    You could do it with a Digital Loudspeaker Management system but analog won't give you enough flexibility unless you have a Multi band Parametric EQ in there as well. With the combination of the crossover and the EQ you might be able too get things a bit better.



    What is the surprise there???

    Rob
    toddalin

    Like Rob said, and yes it’s doable, the flexibility it offers and monitoring of each loudspeaker element is a neat one. I use a (DCX2496) as you can tell from the (signature) below along with my JBL control series 5 and 1.


    I can only get a few EQ bands and a all six dynamic EQ to operate on the (DCX2496) the more steeper crossover filters I use, the less (free space) I get to use the EQ’s on the (DCX2496)

    Two bands for each LCR HF output and three bands on the centre channel LF output. Want I need is (DEQ2496) for each LCR main input to handle tones that I need to control once they become airborne in the room.

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    Senior Member Akira's Avatar
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    Quote Originally Posted by toddalin View Post

    How could one hope to modify these simply by changing the low frequency roll off point and curve as is done with an active crossover?
    Active crossovers today are extremely sophisticated, and have nothing to do with your description. Units like the DBX drive rack can do a complete analysis of each individual driver and tailor a perfect response x-over curve between components. They also analyze and compensate for the response of the room. High end systems have their entire components integrated with amps, drivers and crossovers each matched and tailored for perfect response and performance. Myer has been doing this for 20 years. Some systems like Tannoy use a combination of bi-amped with a passive design, but for the most part anything on a pro level almost always utilizes a superior active network.

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    Quote Originally Posted by Akira View Post
    Units like the DBX drive rack can do a complete analysis of each individual driver and tailor a perfect response x-over curve between components. They also analyze and compensate for the response of the room.
    Not completely true. I've got a Driverack 260, and while the unit *can* tailor crossover frequencies, slopes, delay, and response curves just about perfectly, it does not do the analysis itself - you have to either use a pre-programmed setup, (most JBL Pro stuff is already there), or program it yourself.

    Likewise, they can do an automated simple realtime 1/3 octave response analysis and resultant curve for a room, but that is at only one location, and does not take more advanced parameters such as phase and time domain into account. For those, you need something like SMAART.

    John

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    Quote Originally Posted by johnaec View Post
    Likewise, they can do an automated simple realtime 1/3 octave response analysis and resultant curve for a room, but that is at only one location, and does not take more advanced parameters such as phase and time domain into account. For those, you need something like SMAART.

    John
    Yes, most people I meet in the sound system industry ignore that function and rely on other analysis methods like SMAART and shock-horror their own ears! Actually, most people use BSS or XTA units here in the UK (they cost more though).

    dbx may have actually alienated some users by installing that function as it's considered more of a marketing tool than anything the serious operator relies on.

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    Senior Member Akira's Avatar
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    Quote Originally Posted by johnaec View Post
    Not completely true. I've got a Driverack 260, and while the unit *can* tailor crossover frequencies, slopes, delay, and response curves just about perfectly, it does not do the analysis itself - you have to either use a pre-programmed setup, (most JBL Pro stuff is already there), or program it yourself.

    Likewise, they can do an automated simple realtime 1/3 octave response analysis and resultant curve for a room, but that is at only one location, and does not take more advanced parameters such as phase and time domain into account. For those, you need something like SMAART.

    John
    So which is better? I don't think a passive design is anywhere near the new electronic designs.
    That doesn't mean they don't have their own appeal and can work beautifully.

    btw, I was referring to smart system analysis in general, of which DBX is only one.

    Also, a little off topic but, do you think an internal amp is better than an external amp? I'm still on the fence on this one.

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    Personally, I prefer active speaker management, (crossover, EQ, phase, etc.).

    I'm not sure what you mean by internal or external amplification. If you mean internally powered speakers, I think the manufacturers do a pretty good job of tuning amp characteristics specifically for the drivers, which can greatly simplify things.

    John

  9. #9
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    Quote Originally Posted by johnaec View Post
    Not completely true. I've got a Driverack 260, and while the unit *can* tailor crossover frequencies, slopes, delay, and response curves just about perfectly, it does not do the analysis itself - you have to either use a pre-programmed setup, (most JBL Pro stuff is already there), or program it yourself.

    Likewise, they can do an automated simple realtime 1/3 octave response analysis and resultant curve for a room, but that is at only one location, and does not take more advanced parameters such as phase and time domain into account. For those, you need something like SMAART.

    John
    johnaec

    Couldn’t you use a (microphone mix) and several microphones of the same make plugged into the mixer and then set the output lead to the dbx rakedrive for testing?

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    Quote Originally Posted by JBL 4645 View Post
    Couldnít you use a (microphone mix) and several microphones of the same make plugged into the mixer and then set the output lead to the dbx rakedrive for testing?
    Maybe in an ideal world, but you'll likely get all kinds of phase cancellations because of all the different locations, and I don't think the summed output would be an accurate representation. Why don't you try it and let us know?

    John

  11. #11
    JBL 4645
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    Quote Originally Posted by johnaec View Post
    Maybe in an ideal world, but you'll likely get all kinds of phase cancellations because of all the different locations, and I don't think the summed output would be an accurate representation. Why don't you try it and let us know?

    John
    johnaec

    I have noticed that when playing wideband pink noise on one front channel and switching between (normal and inverted). Also you can wire the loudspeaker terminals with opposite polarity.

    So what is the simplest thing to look for or listen for? What should a listener be listening for that will give good interaction that the two are perfectly aligned?

    Thanks.

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    Quote Originally Posted by JBL 4645 View Post
    So what is the simplest thing to look for or listen for? What should a listener be listening for that will give good interaction that the two are perfectly aligned
    I don't know of any foolproof way to tell by listening if something is out of phase or alignment. It takes something like SMAART to get that deep...

    John

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