Page 1 of 5 123 ... LastLast
Results 1 to 10 of 46

Thread: Help with speakers and amps

  1. #1
    New Member
    Join Date
    Apr 2020
    Location
    Pnw
    Posts
    16

    Help with speakers and amps

    Needing connection advice here.
    I have 4-QSC2450 amps and 2-QSC EX4000 amps.
    I have 4-CerwinVega EL36B subs, 4-JBL SF125, and 4-JBL JRX100. All the JBL's are quasi 3-way speakers with built in crossovers.
    When I acquired this system it had a Behringer CX3400 Super-X Pro Crossover.
    Since there are not any horns in this system, it does not make since to use the crossover. When it was demo'd to me it sounded just OK, but I could tell something was not quite right. Thus getting the system for a very good deal.
    The CX3400 crossover was in 3-way stereo mode. Subs on lows and out to the EX4000 amps, then to the EL36B cabs (2 left 2 right). Mids went out to 2 of the 2450's, then to 4 of the JBL's (2 left 2 right). Highs went out to 2 of the 2450's, then to 4 of the JBL's (2left 2 right).
    I am at a conclusion to either get horns (more money and more space), or not to use the CX3400.
    If I don't use the x-over, I guess just daisy chain the amps (1 EX4000 and 2 2450's for left and same for right). Keep the EX4000 for the EL36B's, and the 2450's for the JBL's.
    Am I on the scope of this? Any other ideas? Please advise.

  2. #2
    Since there are not any horns in this system, it does not make since to use the crossover.
    I see no reason why you shouldn't. You could get another processor like a dbx though, the Behringer isn't exactly for professional use yet people use them because they're very affordable (and get the job done)

    I am at a conclusion to either get horns (more money and more space), or not to use the CX3400.
    Afaik there aren't many sub horns on the market, unless you build your own.

    If I don't use the x-over, I guess just daisy chain the amps
    You risk breaking the amplifier(s) and speakers by doing so.. daisy chaining the speakers in series/parallel is another thing.

    Am I on the scope of this? Any other ideas? Please advise.
    You certainly are but consider the amp to speaker ratio (I assume they're bridgeable 2ch amps) and how to adjust the individual speaker volume if you choose to or find yourself doing zones (ie. run part of the system as main and some as fills)

    EDIT : running the amps in stereo allows you to adjust volumes (unless you bridge them in pairs, ie. turning 1 knob adjusts 2 cabs), the problem comes when you need to spread the system which unfortunately calls for time-aligning, ie. you'd use SMAART or similar analysis program to find out the impulse response (then you'd input the value into a processor that has time delay, Xilica comes into mind but it costs a fortune).. then there's the weight factor, 6x2RU amps plus a >12RU rack could be 100kg or upwards assuming an amplifier weighs ~15kg (you could look into 4ch class D amplifiers though as they've evolved since, many sound guys prefer the heavier class ABs because they're considered better sounding, this depends on whether it's an install or mobile rig)

  3. #3
    New Member
    Join Date
    Apr 2020
    Location
    Pnw
    Posts
    16
    Does anyone have a better solution?
    Last edited by Darman; 08-24-2020 at 02:48 PM.

  4. #4
    Member
    Join Date
    Jan 2014
    Location
    Ottawa Ontario, Canada
    Posts
    1,913
    Quote Originally Posted by Darman View Post
    Since there are not any horns in this system
    Say what? The EL36B is a horn loaded subwoofer, and all those JBL boxes have horn loaded compression drivers in them.

    Quote Originally Posted by Darman View Post
    When it was demo'd to me it sounded just OK, but I could tell something was not quite right.
    Yeah a basic analog crossover doesn't cut the mustard here you need a DSP processor like the DCX2496. With those subs the tops need to be delayed to align properly, the subs need a steep high pass to protect the drivers and some tone shaping, and those JBL boxes will need some EQ to flatten response and extend the highend, and limiters to protect their notoriously fragile compression drivers.

    I don't quite see the need for 8 tops with only 4 subs though, the JRX100's on the Vega subs(2 per side) should do the job.
    Last edited by conanski; 08-24-2020 at 03:37 PM.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

  5. #5
    Quote Originally Posted by conanski View Post
    all those JBL boxes have horn loaded compression drivers in them.
    Many advice to use parametric EQ with CD horns but this in turn requires bi-amping (which means extra components like the PEQ and an additional amplifier) to get the most out of it.. it's mainly to deal with comb filtering in the midrange (the horn flare exaggerates certain frequencies), some manufacturers were seemingly nice having put it in their processors.

    With those subs the tops need to be delayed to align properly
    I think they'd be delayed by the folded horn length plus/minus distance (in ms), depending on how they're placed, then delay the fills, say from the back of the room so the soundwaves meet either at the middle or front of the stage, whether it's a live show or a disco (before SMAART and whatnot this was either science or guesswork, depending on the engineer I think)

    the subs need a steep high pass to protect the drivers and some tone shaping
    I think high-passing a sub could possibly damage it but someone could confirm this.. it has something to do with resonant peaks near the cutoff frequency. However, many audio devices have a frequency response of 30Hz-20kHz although I've been lately paying more attention to this with HPF sweeps as the resonance enhances the low freq, possibly harming speakers (I try to keep it at 2-3 max these days, at 7-9 the highs sound sweet but on "idle" it dramatically increases the low frequencies).. another thing they do is change the phase depending on the filter order.

    If anything I'd low pass the subs at 120-180Hz or so (I think 100-120Hz is normal in pro audio) which is what the crossover does but the dbx has subharmonics (gimmicky, I know, but I found it pleasing to my ears at certain levels plus I think subs in general like sine waves.. think of it as an "extra" punch, not like filter resonance)

    and those JBL boxes will need some EQ to flatten response and extend the highend, and limiters to protect their notoriously fragile compression drivers.
    Limiters do help with unwanted peaks but running them on red isn't going to help as you're practically feeding them a square wave.

    Mainly I think the system would run nicely 2-way with low-passed subs and fullrange tops (or HPF at ~100-120Hz so as to extend their lifespan), then notch/param EQ some room if there's a microphone to avoid feedback (and use a low cut/EQ in the mic channel to deal with rumble, and easy on the reverb if there's one)

  6. #6
    Member
    Join Date
    Jan 2014
    Location
    Ottawa Ontario, Canada
    Posts
    1,913
    Efinque... nearly everything you stated there was wrong, the only thing I sorta agree with is a basic 2-way active setup.. subs crossed to tops at 80hz.

    CD horns equalization does not require bi-amping and it does not deal with comb filtering.
    Time alignment creates driver coherence at all distances.
    Hi pass filters on subs is what protects the drivers from over excursion below box tuning/horn loading. Not having this filter is how most CV horn sub drivers are blown.
    Limiting in the digital domain works very differently than with an analog limiter, there are no square waves, no distortion of any kind even when the limiter is hammered
    Last edited by conanski; 08-24-2020 at 06:06 PM.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

  7. #7
    Quote Originally Posted by Darman View Post
    Mids went out to 2 of the 2450's, then to 4 of the JBL's (2 left 2 right). Highs went out to 2 of the 2450's, then to 4 of the JBL's (2left 2 right).
    That makes no sense. Since the JBL are two ways with internal passive crossovers the electronic crossover should have been run as two-way, the lows going to the subs amps, the mids/highs to the tops amps. BTW, in most cases subs should not be split left/right. This explains why: https://www.fulcrum-acoustic.com/wp-...er-Alley-1.pdf
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

  8. #8
    New Member
    Join Date
    Apr 2020
    Location
    Pnw
    Posts
    16
    Jeesh, all this tech jargon. How about just using the CX3400 for the sub signal (mono), then run the left and right straight to the amps.(by-passing the CX3400).

  9. #9
    Quote Originally Posted by Darman View Post
    Jeesh, all this tech jargon. How about just using the CX3400 for the sub signal (mono), then run the left and right straight to the amps.(by-passing the CX3400).
    Yes, mono the low end if possible.. but I'd run the tops from the high out (leave the mid out alone if you don't have dedicated mid cabs) with a splitter/Y-cable in case you want the tops high-passed/processed (or time-aligned if your xover/DSP allows it) or if you use bits of the system as zone/monitors bypass the xover and run them full range.

  10. #10
    Quote Originally Posted by Darman View Post
    Jeesh, all this tech jargon. How about just using the CX3400 for the sub signal (mono), then run the left and right straight to the amps.(by-passing the CX3400).
    If you do that the mains won't have the lows filtered out. That will cut their effective power handling by 75% and cause all sorts of response issues. If you don't understand the 'tech jargon' learn it. Knowing how gear works is what separates the pros from the amateurs, and that's what separates the guys who get the high paying gigs from those who don't.
    Bill Fitzmaurice
    Bill Fitzmaurice Loudspeaker Design
    www.billfitzmaurice.info/forum

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
a