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Simple one! Figuring out how many watts I need.

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  • Simple one! Figuring out how many watts I need.

    I've come across posts mentioning that you don't need a significant amount of watts to power speakers or have I understood this incorrectly? Many ideas have been thrown about...

    My future sub is going to be a closed box with the Dayton RSS315HO- 4 12 inch driver in a closed box approx .5 QTC. The driver is rated about 90 sensitivity.

    I got a SVS 300 watt plate amp which I am presuming is not powerful enough?

    Do I need the rated RMS of 700 watts to power these monsters?

    Unfortunately, the cabinet is already made. I know if I went vented I would get more efficiency but for now I want to go with the closed box.

  • #2
    IMHO, you are on the right "track".
    It's a mistake to assume (as many of the car sub guys state) that you have the "use up all the watts".
    That 12 inch RS is a real beauty, and will provide great sub bass for music and most home theater uses.
    You really have to run the simulations - off the top of my head, 300 watts with that driver should give you 108, maybe 110dB out.
    That's pretty fricking loud!
    But you run into immutable physics - doubling the watts will only give you +3dB output.
    If I wanted to really have some awesome bass, I'd rather have 2 RS 12 inch subs with 300 watts each, rather than 1 with 1000 watts.
    It's all about "swept volume".

    I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
    "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

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    • Trdat
      Trdat commented
      Editing a comment
      I do have two RS 12 inch subs. I also have bought a Chinese 900 watt/4ohm amplifier and only came across this idea recently. But its good to know that the SVS plate amp has the possibility of powering the subs, might just keep the Chinese amp as a spare for now.

  • #3
    With 90dB sensitivity you'll get 90dB with 1 watt, 100dB with ten watts, 110dB with one hundred watts. What do you get with 700 watts? Evicted.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #4
      Originally posted by billfitzmaurice View Post
      With 90dB sensitivity you'll get 90dB with 1 watt, 100dB with ten watts, 110dB with one hundred watts. What do you get with 700 watts? Evicted.
      BUT...There seems to be two threads that come up repeatedly (1) you really don't need a lot of watts to get high dbs and (2) you do need a lot of watts (headroom) to play the peaks in many kinds of music.

      So, if you have a big powerful 12" subwoofer that can take 500 watts without exceeding xmax, does it make sense to power it with a 150 watt amp that will produce quite high decibels? (If the answer is "yes" that is great because it would save money, but I just want to know because there seem to be conflicting views.)

      Comment


      • craigk
        craigk commented
        Editing a comment
        I have never listen to a speaker that had a good high powered, even over powered amp, and thought this sounds bad. I have listened to a lot of under powered systems and thought this sounds bad.you can't have to much power.

    • #5
      If you're running on average 30 watts then 300 watts of power gives you plenty of headroom. If you're running on average 100w, and are at 110dB, it will take more power to maintain adequate headroom, but not for all that long, as your subsequent hearing loss will soon put an end to your hobby.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #6
        I have never heard the comment I wish I had less power used in audio. I think most adults have enough sense to take care of their own ears. Dont need the liberal mentality of I know what is better for you than you do.
        craigk

        " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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        • #7
          I run a Lab 12 sub with a mere 200W plate amp. It can handle a lot more, but I'm not short on output at all. If I wanted more headroom, I'd spend the money, but I used what I had.

          So... Use the amp you already have. If you find yourself hitting clipping sometimes, invest in the bigger plate amp. It's really that simple. You're only 3.7dB short on head room running 300 instead of 700 watts.
          Electronics engineer, woofer enthusiast, and musician.
          Wogg Music
          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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          • #8
            My only advice is investigate your SVS amps' true power. I know SVS is well regarded, but does the 300 watt figure stand up to scrutiny, can it compare to other mfrs figures.

            That way if you're not satisfied, you'll know what amount of power you really need.

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            • #9
              One other thing to consider about headroom, transients and power. One you have one transient by itself it is no big deal with 200 watts. When you have 5 in a row in a very short time period, you have an issue. More power, more better.
              craigk

              " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

              Comment


              • #10
                You want all the watts. You want as many as you can afford. I have never EVER thought to myself, "Geeze, I wish I had less power.". I currently (no pun intended) have well over a kilowatt so I can listen at 70-80 dB levels. As has been stated before, it's about the transients and headroom. Get as much power as you can. You will never regret having too much amp (there's no such thing). Hit up Ebay or F'book marketplace if new is too rich for your wallet. Get a big mono bridgeable...something. Especially for a sub. That sub deserves so much more than a plate amp. That sub needs an amp with a big honkin' power supply. If that plate amp doesn't weigh at least 25 pounds get something that does. You will not regret it.

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                • #11
                  Originally posted by craigk View Post
                  I have never heard the comment I wish I had less power used in audio. I think most adults have enough sense to take care of their own ears. Dont need the liberal mentality of I know what is better for you than you do.
                  Yeah but in all fairness, if someone buys an "Over" powered amp, they tend to just live with it, and assume they made a great decision or purchase.

                  I have owned a few "Overly" big amps, but simply would never admit I did not "Need" all the power.

                  But after realizing (by watching accurate power meters) I was only using at most 20-50 watts or so of my 250 Watt amps, (( EVEN WHEN CRANKED) that I convinced my wife I just HAD TO HAVE, what do you say..uhmmmm

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                  • #12
                    Originally posted by CJB67 View Post
                    You want all the watts. You want as many as you can afford. I have never EVER thought to myself, "Geeze, I wish I had less power.". I currently (no pun intended) have well over a kilowatt so I can listen at 70-80 dB levels. As has been stated before, it's about the transients and headroom. Get as much power as you can. You will never regret having too much amp (there's no such thing). Hit up Ebay or F'book marketplace if new is too rich for your wallet. Get a big mono bridgeable...something. Especially for a sub. That sub deserves so much more than a plate amp. That sub needs an amp with a big honkin' power supply. If that plate amp doesn't weigh at least 25 pounds get something that does. You will not regret it.
                    Kinda like having a 600 horsepower muscle car to tool around town going 45 mph.?

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                    • #13
                      Right but you get to 45 really quickly if you have proper output system (trans/axles/tires which equates to speakers in this analogy where the engine is an amp).

                      If you're not getting all the power out of your amps, you probably have an input sensitivity mismatch.

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                      • #14
                        Originally posted by Serpentus View Post
                        Right but you get to 45 really quickly if you have proper output system (trans/axles/tires which equates to speakers in this analogy where the engine is an amp).

                        If you're not getting all the power out of your amps, you probably have an input sensitivity mismatch.
                        Hmm not sure this analogy works...

                        I compared an older HK 20 watt per channel amp to my 250 watt when I still owned it, and as long as the "little" hk was not driven too far over 20 watts, they were for most intents extremely similar in all regards.

                        You lost me on the "If your not getting all the power out of your amps".......what are you saying?
                        My point was that most normal and even "Loud" listening, is done with FAR less power than most big amps are capable of.

                        My 250 watt amp was simply not needed for 99% of my listening. I never saw it go beyond 50 watts and that was loud and with peaks.
                        most normal volumes were a couple of watts.

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                        • #15
                          To the OP: as the discussion shows, it's actually not a simple question.
                          Francis

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