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Amps

Discussion in 'Sound, Music, and Intercom' started by kovacika, Jan 15, 2007.

  1. kovacika

    kovacika Active Member

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    I know this could turn into a massive turf war between crown and behirnger but, here is my delima.

    I have 2 1000rms watt subs, 2 250rms mains. I currently have 2 Crown XLS 402 amps. I can use one for each sub, works awesome. But a i also need to power the mains.

    Now the question is, keeping in mind these need to play as loud as the speakers allow, with medium to high quality, the Behringer ep2500 or another crown xls 402. (I have a $300 dollar budget if anyone has any other suggestions.) The Behringer looks great on paper, but im suspicious.

    If any one has had a behringer amp issue, not just a bone to pick with behringer, but an actuall failure or issue i would love to know.

    Thanks
    Aaron
     
  2. SHARYNF

    SHARYNF Well-Known Member

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    HI I would look at the qsc line of amps, might push you budget a bit but they are solid with good reputation8

    How are you setting up the 402 for the sub? it is a single 18 at 8 ohms or dual 18's you need to be careful with the 402 and only run it in bridged mono at 8 ohms
    the other option is just get another 402 they are under 400 dollars on ebay

    Sharyn
     
    Last edited: Jan 15, 2007
  3. mbandgeek

    mbandgeek Active Member

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    what exactally is the intended use of the system?

    Drama, Rock band, Chorus, public speaking?

    I second the looking at QSC's line. I've heard that they have great products and they have great customer service.
     
  4. soundlight

    soundlight Well-Known Member

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    And you now have a third for QSC. They're great amps. Very reliable.
     
  5. kovacika

    kovacika Active Member

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    System is for a rock cover group. Largest venue would be about 1000 people. Im buying another pair of mains to add to what i have but just run them in paralell.(I know this will still be underpowered for 1000 people, but one step at a time) Im also biamping, but i have the amp for the highs already. I used to use the xls 402 for the lows which was awesome, but a little underpowered when used in stereo mode. Now I bridge it and another one i picked up for nothing and use them on the subs (each amp pushes a sub rated 1000watts, 4ohms).

    I looked at the QSC's, but they are more expensive than the Crown, and from what i hear both are rock solid companies.
     
    Last edited: Jan 15, 2007
  6. SHARYNF

    SHARYNF Well-Known Member

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    you are way way under what you need for that large an audience
    Here are some comments:
    As I guessed your subs are 4 ohms, you should NOT run your crowns on them you are going to destroy them they are only rated in bridged mode for 8 ohms when you bridge mono you are effectively taking the load and splitting it on the two amps so you are trying to run the crowns at 2 ohms a very bad idea

    On subs so that you don't blow out the voice coils you need to have an amp that is approx twice the rated power of the speaker, so you would need a QSC RMX2450 for each sub, and depending on how efficient your subs are you are going to need 4 to six of them . Despite what you might think stacking them all on top of one another or side be side in one place will improve the effectiveness. Problem with 1000 people is it is a large area and you need not only to be able to hear the sound at 30 feet but also at 150 feet.

    A lot depends on the tops you have, and again how efficient they are etc

    I would say that you are probably looking at something with horns and 12-15 inch dual speakers, here youare probably going to need to have about 200 watts or so for each horn and probably 1000 watts for each pair of 12/15's

    For that large a group you would need i would guess four stacks per side so you would have four horns, and 8 12-15's so you would probably use 3 qsc rmx's per side with one feeding for simplicity you would probably need a rmx2450 for each of the cabinets or 8 of them

    A thousand person venue definitely gets up up there in pa level to say the least.

    So if you were to come back to a more realistic level of say 200 people you
    would have 2 dual 18 cab each with a rmx 2450, and then have two crowns or two rms2450's for the mid/highs . you would want to triamp the system, 18's should be crossed over at 80-100, no higher than 120, your mids up to about 1500 or so depending on your horns.

    If you are buying cabinets for the mids/high make sure they are can be placed side by side so if you have horns make sure they are no more than 60x40 and not the usual 90x40's
    If you look on ebay there is a guy selling a decent system 270076133314 he is using crest amps which are also good
    his system would be a middle system say 400-600

    notice how you can stack or hang them, Personally I'd but all the subs on one side, but it does look better balanced the typical two on a side


    Sharyn
     
    Last edited: Jan 15, 2007
  7. kovacika

    kovacika Active Member

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    For mains Ive got a pair of custom built 15s modeled after EAW FR159z. Subs are single horn loaded 18s (again custom built- look at http://www.speakerplans.com/index.php?id=186horn ). I bought the stuff used for almost nothing from a freind leaving the industry. I know I need more gear, but right now I can borrow the stuff I need for the one big venue. I dont have money for all of the stuff right now. I know what high quality gear is, I just dont have the cash to buy it. I'm looking for mid-level gear.

    As for the Crown amps, the literature states they are rated for 4ohm bridged operation. The chart on the website only shows the 8 ohm rating but also states later "Load Impedance: Rated for 2 to 8 ohms per channel in Stereo, 4 to 8 ohms in Bridge Mono". The manual specs 1140 watts at 4ohm bridged mono.

    As for the subs, i mistakenly said 1000watts rms, they are really 500watts rms, 1000 max. I learned about toasting voice coils 4 years ago the hard way :)- worst part was it wasnt even my gear.

    How common is it to have single 18s at 4ohms? I cant seem to find any online.

    Also, not to question your knowledge, but im a little skeptical of the numbers you gave for a 1000 person venue. I worked this past summer at an outdoor concert venue that had 2 eaw MK5326 per side on top of a JBL w bass bin per side. All of this was powered by a rack of macro techs. The venue could hold 1500 people. It wasnt the loudest system ever, but the bass pumped and you could hear everything with ease, even at the back of the crowd. Was it that it was an outdoor venue? Or is it just that those EAWs are ridiculously loud?

    I also know that the amount of gear needed will be different for me if I use medium quality gear, but again, I need something to work with now, and medium quality gear s what I can afford right now.
    Thanks
    Aaron
     
    Last edited: Jan 15, 2007
  8. BNBSound

    BNBSound Active Member

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    Just another voice in the crowd cheering for QSC. I've never yet heard of a problem with one, and ALL the rental houses in my neck of the woods have them.
    Having shipped my Mackie amps back and forth to Texas numerous times, and hearing and reading about trouble with Behringer amps, spend a little extra on a QSC PLX2 series, get more wattage and less weight, and only pay for shipping one way... if you get my drift.
     
  9. BillESC

    BillESC Well-Known Member Premium Member

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    I too will suggest QSC. It is very hard to do better than the six year warranty.
     
  10. silvrwolf

    silvrwolf Member

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    I would definitly recomend the Qsc RMX-850. They are totally reliable and they cost $299, its worth looking into but it will easily beat other amplifers in its price range.
     
  11. SHARYNF

    SHARYNF Well-Known Member

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    Usually I go by the spec sheet, and the spec sheet does not show any 2 ohm usage or bridged in under 8 ohms, plus some personal experience has shown me that there are only a few amps that can reliably run 4 ohms bridged for an extended length of time on subs.

    When you said 1000 watts on the subs I assumed dual 18s in parallel. You are correct it is very rare to have 4 ohm individual 18's speakers. Most of the designs for cabs for high power large venue are dual 18's at 4 ohms, 4 ohms in standard dual channel mode is typically the sweet spot for amp power.

    W Boxes were the rage years ago, they are very efficient, don't have a great very low end but put out a lot of bass and project it pretty far. Don't know if the ones used were dual 15 or dual 18's but you are talking about a performance that is way beyond what you have in your cabinets. Your design probably will go lower but will be no where near at loud. Remember that a lot depends on the horn design and the driver in it and that every 3db increase is doubling the apparent sound level

    Your eaw imitations again it is hard to tell how efficient they are typically the imitations look like the real thing but don't match up to the full performance, the rating for the real ones is 100 db at 1 watt probably rated in the high end since it does not say, the eaw at the concert you were at are rated at 107 in the high end so you again are looking at way way more output, and there were two of then per side.

    Your cabinets have a 1 inch driver on the horns, the other eaws have a 3 inch driver.

    at the end of the day it is a combination of how much air you can move, and how efficient your design is to turn that air movement into useful sound.

    Outside in a decent location you can get away with a different speaker set up you don't have side and ceiling reflections, so the sound can sound cleaner and project further since you have eliminated a lot of the interfering reflections and canceling and "sound alley's"

    In a pro setup you also tend to spec a system so you are not attempting to run flat out since you run the risk of failures, so could you get away with less gear, possibly but the old expression you can either bring it to use or bring it to replace can apply

    It also depends on the type of music you are playing, and is it live or recorded/

    A system for dj will tend to get more out of the install but will need a lot more bass, since the dj;s like that pounding heart rate controlling base

    A live band for jazz can get away with a very different system than a rock band

    In addition once you get to larger groups over 500 you typically want to put more and more of the backline sound thru the pa so you are not just looking at vocals, and you want to keep the spl level down on stage but up out in the audience, so you need quite a bit of power



    anyway good questions,

    Sharyn
     
    Last edited: Jan 16, 2007

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