Passive speaker/power amp question

Discussion in 'Recording/Live Sound' started by MLG Audio, May 11, 2015.

  1. MLG Audio

    MLG Audio Member

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    Okay so I started out my life as a soundguy using all powered gear. I'm putting together a passive monitor system for some larger outdoor type events and I'm looking at amps to match with my yamaha sm15v's. I understand enough about amps and speakers to know that you do want a little headroom without pushing too hard, while also not using an underpowered amp and crushing it to get enough volume.

    I've heard people say get an amp that will put out about 1.5 times the program rating of a speaker. I'm hoping to get some of the crown xls amps to keep weight down, and I know they sound great (and the prices of them all just dropped a bout $100 bucks each).

    Would the xls1000 be my best bet at 700 watts bridged mono 8 ohms? Or would the added headroom of the xls1500 (1050 watts bridged) be a better choice?

    Thanks for any advice!
     
  2. amphog

    amphog Silver Supporting Member

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    You are bridging them for monitor duty?
     
  3. MLG Audio

    MLG Audio Member

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    If I was going to use a one amp to one speaker configuration then yeah I would. If I get an amp with enough power per channel in stereo I'll go that route.
     
  4. amphog

    amphog Silver Supporting Member

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    When you bridge them, they start to get cranky at 4 ohms. I would buy amps that could do one ot two wedges per channel, amps are pretty cheap these days. Also if you are light on monitor mixes, you get a little control by having the volume control on the amp for each speaker.
     
  5. MLG Audio

    MLG Audio Member

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    I run individual monitor mixes so two speakers on a channel is a no go for me. Also if I'm bridging them they still stay at 8 ohms if I'm only running to one speaker. A venue I occasionally work at has used the xls1000 bridged mono on their monitors with no "crankyness" at all for a few years now.
     
  6. MLG Audio

    MLG Audio Member

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    However if I do find an amp that puts out enough per side and is still lightweight I will go that route. I'm not really set on either way, just looking for opinion on the difference in wattage rating
     
  7. Uncle Pat

    Uncle Pat Member

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    I power my SM115V's (5) with two QSC GX3's (300w/ch), for four mixes across the front, and a GX5 (500w/ch) for the drum wedge. I have never been starved for power, even at loud outdoor shows. Bought them all used pretty cheap too....even better!
    I should add that I also furnish backline amps, and they are lower wattage...Dr Z 18 watts, Hayseed 30, Peavey Delta Blues 40 watts....no Marshall stacks. :)
     
  8. MLG Audio

    MLG Audio Member

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    Seems like the recent release of all the 1000 watt and up powered speakers are more of a marketing thing. It makes me nervous to only run 3-500 watts to a speaker lol.

    But I guess it would make sense since the posted ratings of the powered speakers are usually peak ratings.
     
  9. 335guy

    335guy Member

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    You need one amp channel per monitor send. So if you use two monitor sends, you'll need a stereo power amp. You could drive two 8 ohm monitors off of each side of the stereo amp ( 4 ohms ). And while Yamaha says the SM15 V's handle 500 watts program, the amps are rated for continuous/rms power output. The SM 15 V's are rated at 250 watts continuous, as program and continuous/average/rms are different ratings.
    If you want approx. 1.5 times the power handling of 250 watts per speaker, then the Crown XLS2500 would be the better choice if you want the XLS series. You would feed each speaker 387 watts continuous.

    That said, IMO, you rarely are able to turn stage monitors up that loud before feedback, so a less powerful amp, the XLS 1500, may be fine. And btw, the XLS 1000, 1500 series cannot be bridged in a 4 ohm load. The 2000 and up models can. The XLS 1500 could run (2) 8 ohm SM15 speakers off of each channel with each speaker getting 262 watts continuous. That would probably adequate for stage monitors on most stages.
     
  10. MLG Audio

    MLG Audio Member

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    Thanks for the info 335. I definitely want 4 individual mixes so I'll probably go with two of the XLS amps running in stereo. It's gonna be outdoors so I'll probably spend a little more and get the 2000 or the 2500.
     
  11. 335guy

    335guy Member

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    Well, some powered speakers ( the QSC K series ) do use (2) 500 watt continuous rated power amps for 1000 watts. That said, most all modern powered/active speakers use DSP to limit the amount of power the speaker sees. No way could an average high freq. driver handle 500 watts continuous, so the DSP seriously limits the power going to the drivers.

    But it is a marketing ploy for the most part. What matters in a powered speaker is the db output, and even those are questionable.

    FYI, 300 watts continuous into an efficient passive speaker would get pretty loud. Maybe not quite enough for mains, but for stage monitors on an average stage, it would generally be quite adequate.

    For comparison, consider the EV ZLX12P and the EV ZLX12 passive. The powered version is rated at 1000 watts, yet the passive version using the same drivers but with no DSP is rated for 250 watts continuous.
     
  12. MLG Audio

    MLG Audio Member

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    Really good points! Thanks!
     
  13. griggsterr

    griggsterr Member

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    The QSC that is using 2x 500 watts may truly be using the whole 500 watts for the low end. It is likely not even using 60 watts for the top. Depending on the efficiency of the driver. Also, let me tell you a Dr Z maz 18 will get just as loud as most 50-100 watt amps. They are the bain of many sound guys. I used to own one myself.
     
  14. griggsterr

    griggsterr Member

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    Why not just get a 4 channel amp? save some rack space, some patching. Plus the QSC that I have been looking at has remotely controllable EQ (great for eq ing monitors)
     
  15. loudboy

    loudboy Member

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    I've got an XLS2000 and it sounds OK, but not as good as the PLX Series I used to own.

    Love the weight, tho. The case will weigh more than the amp. <g>

    Same power, but it just sounds more choked or something.
     
  16. MLG Audio

    MLG Audio Member

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    A 4 channel amp isn't out of the question. I don't think I'll ever need to have the speakers in different locations at the same time. I am definitely looking for a low-ish budget since shows don't pay terribly well around here. For that reason I'm not excluding behringer inukes. Rack space and patching isn't an issue. I have a 10 space rack that will only be housing the amps and a power conditioner. And I made a patch panel for the back with 4 xlr and 4 nl4 jacks to keep everything hard wired and easily accessible.


    Sent from my iPhone using Tapatalk
     
  17. GuitarGuy66

    GuitarGuy66 Member

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    From QSC's site. GX7, one speaker per channel.
     
  18. mixwiz

    mixwiz Member

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    I bought a 2500 drive core when they first came out and it's been flawless. Used it to power a monitor rig and also have used it bridged into a pair of SRX 718s. As others have said 300 watts into a yami club 15 will be more than enough power.
     

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