Peavey 118 Sub Question

Discussion in 'Recording/Live Sound' started by Chase743, Apr 19, 2011.

  1. Chase743

    Chase743 Member

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    I'm a long-time lurker here. I tried searching the forums for this info, but couldn't find exactly what I needed, so I figured I would post a new thread.

    Background:


    I own a PA that I use for a cover band, mostly in small to medium sized venues. We mic up most of the band, including Kick and Bass. Where I am located, most of the medium to large bars have house-sound, so no need for anything too large/powerful.

    Right now I'm using an IPR-1600 as my power-amp. One side is powering two mains. The other side is currently powering one PV118 sub. The sub is 400W program, and according to Peavey's Specs, I'm running 300 Watts at 8ohm from my power-amp, which seems pretty good.

    Here is the spec sheet: http://www.peavey.com/assets/literature/specs/116949_11719.pdf

    I want/need to add a second sub.

    Question:

    Will the two subs be underpowered if I run both off of the same channel. That would be 530W at 4ohms, so figure about 265W per sub.

    The other option is to pick up a second power amp, which I don't mind doing, but I'm not sure if it'll make enough of a difference to justify the cost. I just know that subs suck up a ton of power, and if that last 35W is a lot, I'll get the second amp.

    Even if I stay with one amp, I think that the second sub will make a HUGE difference. Am I right?

    Curious to hear everyone's thoughts?
     
  2. walterw

    walterw Gold Supporting Member

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    a second sub will make a huge difference, even on the one amp. (be sure to get the same sub, you don't ever want to mix low end boxes.)

    also, you'll get the most lows when they're "coupled", that is, set right against or on top of each other. the pair in the middle down on the dance floor will have well more thump than one on each side. (they each reinforce the air pressure created by the other, giving more and louder lows and protecting the speakers a little from excess movement. when they're far apart, some waves from one gets canceled by the other, leaving holes in the low end coverage in the room.)
     
  3. SteveO

    SteveO Member

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    One note here is that in Peavey-speak, "Program" is typically double the continuous power rating. So, the cab is rated for most likely 200 watts continuous power. Being as it's a subwoofer it won't be getting a constant barrage applied to it, so you should be safe in running more than 200 watts into it, but be aware that the power rating on that cab is not conservative.
     
  4. jmoose

    jmoose Member

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    As it is the subs are underpowered... clip the amps and you'll melt the voicecoils. Not a good scenario. Rule of thumb is typically to have twice the power available to maintain headroom... ie speakers rated at 400 RMS, feed 'em 800. At least the same wattage on both side but even that's risky if you get some idiot like me mixing...

    Do the math on all the amps and speakers with ohmages and use continuous ratings, not peak. Keep in mind you can only run a power amp and set of speakers at one ohm setting... if its 4ohms its 4ohms on both channels. Can't run 4 on one side and 8 on the other. If you can work it out and run at 2ohms, do that even if it means running mono.
     
  5. walterw

    walterw Gold Supporting Member

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    huh?

    you can run the two sides of a power amp at different ohm loads all day long.
     
  6. jmoose

    jmoose Member

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    Not quite. I'm not aware and have never seen an power amp that has options... or even a spec sheet for an amp that has different ratings for running different sides at different ohms.

    Most amps give you an option for stereo, parallel stereo or bridge mono.

    Stereo = two sets of controls, two channels of audio.

    Parallel stereo = one set of controls, two channels of audio.

    Most amps will not be too happy if you try to drive one side at 2ohms and the other side at 8ohms or whatever mismatch you want. Most times they'll work yes, you'll hear things yes but in the long term its not healthy nor is it a generally accepted practice.

    Its like some amps will run at 2ohms and be happy about it... some are going to self destruct. Even the ones that aren't rated for that operation will do it, they just won't do it for a long time.
     
    Last edited: Apr 20, 2011
  7. edgewound

    edgewound Gold Supporting Member

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    Not all amps are created equal.

    Some can run with different loads on each channel all day...some can't.

    To be somewhat fail safe, get an amp that can run easily with 6dB headroom( 4 times the speakers' power rating without clipping) for clean sub work.
     
  8. jmoose

    jmoose Member

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    to be fair I almost said "most amps usually can't..." but given the nature of the gear and question thought better of it. We're not talking about stuff that's incredibly robust like Labgruppen or Macrotechs... its a PV system. Not that there's anything wrong with that but it ain't the same... not that Lab even recommends or provides specs on running mismatched sides anywhoo...
     
  9. edgewound

    edgewound Gold Supporting Member

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    You don't have to spend a ton of money on amps for club work.

    A used Crown, Ashly, QSC, Stewart...or a new FACE audio amp will handle the chore just fine, and have plenty of headroom.
     
  10. Chase743

    Chase743 Member

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    Thanks guys.

    Interesting about stacking or putting the subs next to each other. Will definitely try that - thanks for the suggestion.

    SteveO nailed it. The sub is actually 200RMS, not 400. 400 is the program rating. As a rule of thumb, I usually power the speakers somewhere in the middle, which is why 300W seemed appropriate. Also, this is a passive sub, but the powered version is 300W, so that also helped with the decision.

    Also, FWIW, I am running two 8 ohm mains and will be running two 8 ohm subs, so the amp will be sending 4 ohms per side.

    I definitely recognize that Peavey isn't top of the line, but I've had nothing but great experiences with their stuff.

    I'm thinking that I can get away with sending 530W at 4 ohms to two of these subs? Do you guys agree? Or should I think about investing in a second amp to send more juice to them?
     
  11. mixwiz

    mixwiz Member

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    If you have it in the budget, I'd get a second amp.. If one goes down during a gig, you can carry on. As for running mis-matched loads there is no reason you can't do it on any pro audio amp. Wont hurt a thing. As a matter of fact, I use your amp for mon duty in a light rig and run 2 mons on one side and 3 on the other. Doesn't break a sweat and I've got about 40 gigs on it already.

    FYI those IPRs are actually bridgeable (3000 series and below). It's a bit of a hassle as you need to build a special cable but it can be done if you ever upgrade your cabs and need more power. There are a couple engineers from meridian that post on Peavey forum and described the method. I did it once to drive a SRX 728S and it worked well. Those amps are really something for under 300 bucks. If they would only get rid of those stupid blue leds.
     
  12. Johnny V.

    Johnny V. Member

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    The IPR 1600s don't like a 2 ohm load, so I'd pick up another one to run your subs (they're pretty cheap). Within reason, you can't have too much power.
     
  13. modulusman

    modulusman Member

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    You run a sound company and yet you believe in underpowering myth and that you can't run two different loads off an amp. Time to go back to school.
     
  14. Deville2Rocket

    Deville2Rocket Member

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    +1

    Amp channels in stereo mode are completely independent of one another. Might as well be in separate chassis.
     
  15. Schroedinger

    Schroedinger Member

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    Most solid state amps and speakers are relatively robust, and can handle a lot of things that are "off spec" and still work, for a certain period of time.

    Can you under power the speakers? Sure.

    Can you run a rig like this at full capacity for a 4 hour set? Maybe.

    Will it sound great? Probably not.

    The further and further "off-spec" you go, the more likely you are to run into problems. And my opinion is, when it comes to live performance I don't want any problems. I spent 15 years being tech support for my own "improvised" live sound rigs. To me it's not worth the additional stress at a show when things go wrong. At a minimum, you risk the amp cutting out in the 3rd set due to the thermal protection circuit. Not permanent damage, but mighty annoying to you and your audience.

    I'm with moose. Underpowered amps clip and fry drivers; overpowered amps don't, as long as you don't push the speakers into audible distortion. More powerful amps also sound better, even at low levels when they're not working as hard. I don't think impedance is your issue here; I think available power is. I would invest in more amps.

    Incidentally, powered speakers have been a godsend for me. Pricey, but it's nice to have 1Kw on tap in each box, and never need to worry about this kind of stuff.
     
  16. Schroedinger

    Schroedinger Member

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    I don't agree with this. In all but the most expensive amps, the two channels are drawing from the same power supply. It can either put out enough current or it can't; if one channel is stressing the transformer and the filter caps, then it affects the other one too.
     
  17. edgewound

    edgewound Gold Supporting Member

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    The problem with running subwoofers with inadequate power/headroom is gradual damage to the voice coils in instance of clipping.

    It's not a matter of if failure will occur, but when. Burning of voice coils doesn't have to happen all at once on one gig. It can and does happen cumulatively. You can burn a voice coil a little each time you play until enough adhesive is burned away to loosen up the windings.

    If you spend a little more now to get enough power to prevent blown subs, you'll actually spend less in the long run due to greater reliability.
     
  18. Chase743

    Chase743 Member

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    Thanks guys. So, just to confirm, if I'm running these subs, which are 200W continuous, at 265W or even 300W, is that really under-powered?

    The 400W is the program rating. 800W is peak.
     
  19. edgewound

    edgewound Gold Supporting Member

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    Most manufacturers these days recommend driving speakers with powers amps that have 3-6dB headroom over the rated power.

    So, in your case that'd be amps that range from 400-800 watts.

    That said...clipping is the enemy. If you can keep clipping under control you should have minimal power related risks.
     
  20. 335guy

    335guy Member

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    I run all my FOH speakers off one Crown Xs1200. I have (2) BagEnd TA-15's and (2) Harbinger 18" subs. The ohm loads are identical on each side of the amp, 4 ohms. Since my BagEnds are rated at only 200 watts each, I am very careful on how loud I run these. The subs are rated at 400 watts RMS, so I'm sending them a little more power than they are rated for. So far, no issues. I'm not using limiters, though that would be a good idea. I am also coupling my subs in the center to make them more efficient. I also employ the "aux fed sub" mixing technique to keep excess rumble from getting to the subs and that has cleaned up the subs sound considerably. I crossover at 100Hz and run a hpf for the subs at 40Hz. I'm pretty happy with the sound I'm getting with the gear I got. Your subs are a little underpowered if you use that one amp, IMO. If you used the aux fed sub technique and set a hpf at 40 or even 50 Hz, you should be able to run each sub at 300 to 400 watts without difficulty, assuming you do not run them flat out ( full power ). The purpose of having headroom is to not clip the amps and send a distorted signal to the speaker/s. Headroom is for transient peaks in the musical source. A 200 watt RMS speaker can handle short transient peaks, and that's what the extra power is for. It's not to use full power to the speakers all the time. I'd vote for an amp for the subs with a bit more power. Most subs, even the economical ones, seem to like a bit more power than their rated specs. Mine do.
     

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