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Power amp RMS vs. Speaker RMS for subs

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  • #31
    Very true. But if the VC s on the woofers are already bumping against their limits, I'm pretty sure more power is only a solution to getting new subs cuz the current ones will be dead.


    Oh you got that right. The last thing he needs is more power. I was just warning against the added power draw.

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    • #32
      Also, running them on a aux is great for bands so that you can selectively send signal from specific tracks to the subs (ex. kick, floor tom, bass, a little keyboards) which cuts out on woofy sound from vocals and guitars hitting the top of your subs crossover point
      I'd think that proper eq and matching the level of the sub and tops would take care of all that? I suppose if you run the subs "hot" like many DJs this would be a good idea but I like to start out with a reasonably flat system and eq the channels "to taste" .

      I've thought it might be interesting to try a different crossover freq for different channels - vocals and most other stuff going to the tops only crossed at 75hz (or just depending on the 75hz HPFs in the channel strips?) and kick, bass, keys, and CD player going to a sub bus that feeds a 125 hz crossover, highs mixed back in to main (to tops) and the lows to the subs. This would keep the vocals completely in the tops for clarity and fullness. Both guitars and male vocals bottom out at 80 hz anyways.

      "We Have Met the Enemy and He is Us" - Walt Kelly​

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      • #33
        I disagree. Many engineers and I agree that under powering speakers may cause more damage. But I don't wish to argue the point.


        Bullsh*t. Period.

        As a REAL engineer, and one who designs both amplifier AND speaker products for a living, I can say with complete confidense that underpowering a sub will not cause damage compared with overpowering the same speaker. Overpowering subwoofer drivers is by far and away the number one cause of driver damage.

        You have taken a partially valid point for a FULL RANGE signal into a multiway cabinet, and if the signal is clipped (by the power amp) due to it being too small for the job, the harmonics generated may damage the HF driver because the power sent to the HF driver contains a lot of added harmonics which increases the thermal energy of the resulting signal.

        For the OP. the amp he is using into 8 ohms per channel is a plenty good match for thoese LF drivers, and bridging would result it WAY too much power if he were to drive the system hard. The popping sound he is hearing isn't likely to be clipping of the amp, nor is it VI limiting due to the 8 ohm load, so it's most likely the bobbin hitting the back plate pummeling itself to an early death due to too much power for the driver/cabinet combination.

        IF his drivers were (really) rated for higher power (real watts not marketing watts) and the additional power used for headroom, not to push additional snot out ofthe speakers, then bridged mono may be a viable option.

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        • #34

          I've thought it might be interesting to try a different crossover freq for different channels - vocals and most other stuff going to the tops only crossed at 75hz (or just depending on the 75hz HPFs in the channel strips?) and kick, bass, keys, and CD player going to a sub bus that feeds a 125 hz crossover, highs mixed back in to main (to tops) and the lows to the subs. This would keep the vocals completely in the tops for clarity and fullness. Both guitars and male vocals bottom out at 80 hz anyways.


          In general, not a good idea because you would have different filter phase responses and the tops, and there would be a pretty large bump in the acoustic response where the filters overlap.

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          • #35
            I'm a firm believer in running subs on an aux. As you guys have pointed out many of the benefits. I run an L-Acoustic VDOSC setup with Lab Groupen amps with an M7CL for FOH and we have switched from stereo subs to subs on a aux for different shows and the difference is audibly noticeable. Same as for out drum monitor setup, drum sub on a separate aux so we can send only kick, floor tom, bass to the sub and the drummer doesn't get any weird vibrations from stray low end.

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            • #36
              In general, not a good idea because you would have different filter phase responses and the tops, and there would be a pretty large bump in the acoustic response where the filters overlap.
              I think you misread what I proposed. Those channels that had their HPFs engaged would only go to the tops via the main bus. The other (bass,kick,keys) channels would NOT be assigned to main but would go though a sub bus to a 125hz crossover that would have its HPF returned to main via an aux return and its LPF as the only input to the sub amp. No "overlap" involved .

              "We Have Met the Enemy and He is Us" - Walt Kelly​

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              • #37
                ... drum monitor setup, drum sub on a separate aux so we can send only kick, floor tom, bass to the sub and the drummer doesn't get any weird vibrations from stray low end.
                [/rant on]Is this the present fad to always have kick in the monitors, even in the drummer's? Seems to me the more kick you have in the drummer's monitor the softer the lazy SOB kicks it - kinda defeating the purpose. And if it is for tone maybe somebody ought to teach the SOB how to tune drums? As for the drummer hearing the bass why not put the bass cab next to the drummer like a real R&R band?[/rant off]

                "We Have Met the Enemy and He is Us" - Walt Kelly​

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                • #38
                  Iwe can send only kick, floor tom, bass to the sub and the drummer doesn't get any weird vibrations from stray low end.
                  Where would any "stray low end" come from if not from kick, FT, bass and maybe keys? Any reason not to use your channel strips's HPFs on everything else?

                  "We Have Met the Enemy and He is Us" - Walt Kelly​

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                  • #39
                    I've had some odd setups where we can't rolloff the low end because we need it in the downstage wedges but the drummer just wants high end to cut through. Typically you could eq the wedge but I find it a lot easier just to have them separate. Saves time when you have 5 bands playing and someone with a leslie or acoustic that wants some extra low end. Give the drummer a cleaner more consistent signal in the drum sub without sacrificing the eq for everyone else's wedges. Hope that makes since, ha typed it kinda fast.

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                    • #40


                      I def agree, haha. I'm a drummer, and typically a little bass and guitar is all I need. I've actually found that they start kickin it harder with it in the monitors though, usually have to end up compressing and pulling back the signal. I agree with moving the bass cab, but typically we try and keep a low stage volume and with the drums on a riser towards the back of the stage, the bassist wants his rig up closer to show off his stack or whatever

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                      • #41
                        I've had some odd setups where we can't rolloff the low end because we need it in the downstage wedges but the drummer just wants high end to cut through. Typically you could eq the wedge but I find it a lot easier just to have them separate. Saves time when you have 5 bands playing and someone with a leslie or acoustic that wants some extra low end. Give the drummer a cleaner more consistent signal in the drum sub without sacrificing the eq for everyone else's wedges. Hope that makes since, ha typed it kinda fast.


                        monitor board. problem solved.
                        <div class="signaturecontainer">band status - &quot;its complicated&quot;</div>

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                        • #42
                          monitor board. problem solved.


                          This is on a separate M7 for monitors ha. It seems that a lot of you guys disagree with what I am saying. I understand everyone has different opinions on setups, but I've never received this many complaints on stage, most engineers like the setup quite well. O well

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                          • #43
                            the bassist wants his rig up closer to show off his stack or whatever
                            :facepalm: As a former bassist I can't imagine not having a strong drummer/bassist thing going. I used to run a 4 ohm 4/10 cab on my side of the drummer and a 15/1 8 ohm cab on the other side. In fact, I suggested it to the band I'm working with now and they love it !

                            "We Have Met the Enemy and He is Us" - Walt Kelly​

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                            • #44
                              :facepalm: As a former bassist I can't imagine not having a strong drummer/bassist thing going. I used to run a 4 ohm 4/10 cab on my side of the drummer and a 15/1 8 ohm cab on the other side. In fact, I suggested it to the band I'm working with now and they love it !

                              I wouldn't want a bass cab on my side of the stage as a guitarist. That would mean having to play louder than I want to.
                              <div class="signaturecontainer"><a href="mailto:tlbonehead@yahoo.com">tlbonehead@yaho o.com</a><br />
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                              • #45
                                For that matter I've never understood how you'd do crossover with the subs on a (post fader ?)aux or sub. I see folks post about it once in while but haven't seen a detailed description of how it's "done". I normally run subs off the mono sub output of my Behringer xover but running them stereo with the pan pots centered is the same thing, no?


                                Nope ...

                                http://www.peavey.com/support/technotes/concepts/AUX_SUBs.pdf
                                Don Boomer

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