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Thread: Help with speakers and amps

  1. #21
    Quote Originally Posted by conanski View Post
    both drivers work at low frequencies but the lower 15 is low passed at about 500-600hz so only the upper 15 goes all the way up to meet the CD at 2khz
    this eliminates the comb filtering that would occur with both 15" drivers operating at those frequencies.
    What eliminates? The 15"s now do <500Hz both which is going to cause some serious issues in the lo-mid due to phasing, unless the upper is high-passed at 500Hz which I highly doubt it is unless it was a highly specialized, coaxial midrange speaker (ie. squawker) or something.

    15" drivers really should never be run up that high but large format compression drivers that can crossover at lower frequencies are quite expensive so they aren't found in budget boxes.
    I've seen CD horns and horn lenses tech specs state crossover points at 600-800Hz but they become honky and many prefer to xover them higher, like 1..1,2kHz or even 1,8..2kHz (speech contains the most information in the 2,5kHz region which our ears amplify naturally)

  2. #22
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    efinque are you try to learn or just being argumentative? I don't mind explaining if you're willing to listen.
    Paul O'Brien
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  3. #23
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    Ok guys. I just want to know the best way to configure what i have. I can post everything I have if that is best.

  4. #24
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    That would be stereo 2-way with everything through the crossover... 80hz up to the JBLs and 80hz down to the subs. Try it and then come back and tell us what it sounds like.
    Paul O'Brien
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  5. #25
    Quote Originally Posted by conanski View Post
    efinque are you try to learn or just being argumentative?* I don't mind explaining if you're willing to listen.
    No.. this thread just smells weird, either trolling or bullsh*t-generator created PA related talk (I've tried it once, it takes bits from different sites using Google searches based on user-input keywords)

    Then the generator lets you edit the text afterwards (for authenticity)

    Seriously, I checked up those speakers (I guess SF-125 means dual 15" like the JRX-115 which was considered too heavy and sounding muddy by most, regardless, I too wanted/was thinking of buying them at some point) and the JRX-100 is the 215 which is a 1x15" fullrange/monitor (you can't 3-way a 2-driver cab, period).. iirc I heard them at an outdoor festival but it was over 10 years ago (JBL has a name in numbering their products all wrong, to me 215 would mean two-15 and 115 one-15, iirc they did the same kind of thing with their front-loaded horns 4520 which was a dual scoop and 4530 was a single)

    The rig was mostly JBL or so I spied, at least the subs, although it was under the stage, covered by a camouflage net but I saw it in broad daylight as well as in the night (I wonder how I still hear properly, since there were like tens of subs, what a bass zombie I was)

    Apparently they were all the rave back then and large festival systems can't really consist of the higher end speakers due to cost so I assume the rest of the system was JBL too, JRX-line, the SRX (sorry, PRX) is mid-level I think and I remember reading the entry-level JBLs are manufactured elsewhere, in PRC or something.. also the JRX-215 was considered sounding harsh, mid-rangey etc but it was very affordable, from a well respected manufacturer, carpeted and it had a grill (I think many people were "tricked" into buying them and then left wondering how to deal with all the hidden expenses like amplifiers, cabling, processing, transportation etc) but it's wooden afaik and weighs more than it's ABS plastic mid/top-line counterparts (same goes for the dual 15" which is very heavy for one man to carry)

    On a side note : the mid-ranginess (often described as harshness) could actually be a feature, not a deficiency.. you'd have a "louder" vocal PA as a factory default, just EQ off the midrange.

    Anyway, it makes no sense to run any of the enclosures off the xover mid unless part of the system was bi-amped because there's nothing else but subs and the JBL fullrange (unless the tweeters were blown, in which case I'd just replace them.. once I was faced with a case of EV Evid 6.2s with blown tweeters, and one idea was to run them as mids only, the problem was where to get highs and reconfiguring the processor as well as doing cable runs.. there was a pair of 4.2s too but we left them in place, they'd break in a split second with war volumes)

    Then, there's no clue what the system will be used for and in what kind of setting which leaves a lot of doors open for suggestions how to set it up (ie. you can't really rent it out if it's got some state of the art processors and whatnot, biamped cabs etc which require either years of experience in PA or a masters degree in electronics/hebrew)

    Technically you could treat the dual 15" as if it was a 3-way system on it's own, ie. tri-amp it.. but you'd need a separate crossover for that and lots of modifying, custom parts, a fullrange/coaxial mid driver etc which isn't smart in the long run, maybe impressive to some but it comes with a price, one of them being it's a single enclosure.. JBL could've done this I think and some 3-way hifi speakers are exactly like that except the midrange is usually something between the tweeter and the woofer in terms of size, unfortunately in pro audio such speakers are considered toys because they aren't as flexible or modular, ie. you can't properly use them to form a large flown array (or pole mount, I've seen wedges though), making them a mobile DJs choice because they stand out very well due to their height (another thing is piling them on top of subs and high-passing them to form a mobile "poor man's dance stack") but many considered them too heavy and the sound quality mediocre, another thing is if you're some rockstar-DJ.

    OT: Here's a pic of Kool Herc with his car speakers in 1973, they resemble the dual 15"s somewhat



    Another thing that makes it difficult is that you have 4 of each.. I'd put 2 subs per side with the 2 dual 15"s on top of them, then use 2 of the 1x15"s as fills and the other 2 as monitors (you'd get very good SPL from a system like that, plus if you didn't need the monitors you could have them as backup)

  6. #26
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    Efinque... if there is a spambot in this thread it's you.
    Paul O'Brien
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  7. #27
    If there was no need for long cable runs one solution is to plate amp & dsp the SOB (edit : or parts of the system like fills/monitors for quick deployment).. given that they're 2nd hand they could need new drivers or reconing and hacking the box open anyway.

    This would take out the amp rack from the equation, and run them with processing in both ends (they'd add to the weight though) but it greatly simplifies the "user" end, just mark down the xover points (I have no experience with plate amps though, Hypex manufactures OEM modules afaik, so does Dayton Audio and a bunch of less-known companies)

  8. #28
    Quote Originally Posted by Darman View Post
    Ok guys. I just want to know the best way to configure what i have. I can post everything I have if that is best.
    This:
    That would be stereo 2-way with everything through the crossover... 80hz up to the JBLs and 80hz down to the subs.
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

  9. #29
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    Quote Originally Posted by Darman View Post
    Ok guys. I just want to know the best way to configure what i have.
    If you don't have it already download a copy of the user manual for the CX3400. In that you will find how to configure it for 2-way operation, there are mode switches on the back that illuminate lights over the controls on the front that are active in this mode.

    Also make sure all the amps are setup for parallel operation(not bridged mono), that will send the same signal to both channels with a single input cable, and connect 1 speaker to each output.

    There is something else you should check with this being a used system, chances are high at least some of the drivers have been changed because the originals were blown. Start with a single sub and put a sine wave or some bassy music through it, and then without changing anything connect a second sub. The amount of bass produced should be greater obviously, if it isn't then one of the drivers or one of the cables is miswired. Cables should be straight through pin1 to pin 1, pin2 to pin2, etc, drivers can be miswired easily if the internal wiring inside the cab has odd colors instead of red and black, but the fix is easy just reverse the wires.
    You can do the same with the JBL cabs but there is another test you can use with these boxes having drivers you can see, get a 9v battery and touch the + terminal to the + on the speaker, - to the - terminal on the speaker. When you do that the 15" drivers should both move outwords slightly, if one move out and the other goes in that second one is miswired and you need to go in and reverse the wires connecting to it.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

  10. #30
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    Thanks Paul. I will check.

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