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Simple one! Figuring out how many watts I need.

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  • #16
    Originally posted by kevintomb View Post

    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.
    You said with it cranked. It should /sometimes/ peg 250 at full input with music. Not always, but for transients. It's likely your preamp wasn't putting out enough voltage to drive your amp completely. Not that there's anything wrong with that. You'll never clip the amp like that.

    I also have a big amp, a Soundcraftsmen PM 860. I run fairly small speakers off it, but I do have preamp that's capable of the 1V input it needs to get to full power.

    It's much better than my small Dayton and Lepais at any SPL, especially in the bass.

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    • #17
      Originally posted by kevintomb View Post

      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.
      Source voltage.
      craigk

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

      Comment


      • #18
        Originally posted by Serpentus View Post

        You said with it cranked. It should /sometimes/ peg 250 at full input with music. Not always, but for transients. It's likely your preamp wasn't putting out enough voltage to drive your amp completely. Not that there's anything wrong with that. You'll never clip the amp like that.

        I also have a big amp, a Soundcraftsmen PM 860. I run fairly small speakers off it, but I do have preamp that's capable of the 1V input it needs to get to full power.

        It's much better than my small Dayton and Lepais at any SPL, especially in the bass.
        Ooh you misunderstood what I meant, or maybe I said it in an odd way!

        Cranked, to me meant "Playing music VERY loudly" was all. NO way I able to turn the volume up the entire way. like 1;00 O'clock or so was it..!

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        • #19
          Originally posted by kevintomb View Post

          Ooh you misunderstood what I meant, or maybe I said it in an odd way!

          Cranked, to me meant "Playing music VERY loudly" was all. NO way I able to turn the volume up the entire way. like 1;00 O'clock or so was it..!
          Gotcha. Now I have an urge to listen to Communication Breakdown by Zep on my Dragon Lords Build.

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          • #20
            There's one simple indicator of amp quality which no one has mentioned:

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            Francis

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            • #21
              Derision aside, I stand by my comment. Especially for a subwoofer. That thing is rated at 700 watts. Give it 700 watts. Give it 1,000 watts. Many, many more speakers have been blown from too little power than too much power. Also, as power output increases so does distortion. And thirdly, when you're not running on the ragged edge your amps run cooler. They'll last longer. Heat is the enemy. As far as having too much amplifier for my speakers...no. My woofers are rated at 220 watts each. I have 2 per side and an amp rated at 425 per channel at the corresponding impedance. The rest of my amps fall in line with the power handling of my mid basses, upper mids and tweeters.

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              • #22
                There's a power calculator here that takes most everything into account:

                https://www.crownaudio.com/en/tools/calculators
                Francis

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                • #23
                  Originally posted by CJB67 View Post
                  Many, many more speakers have been blown from too little power than too much power.
                  That's the Myth of Underpowering. It simply isn't true. You're not doing the OP or anyone else any good by repeating it.

                  www.billfitzmaurice.com
                  www.billfitzmaurice.info/forum

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                  • #24
                    Originally posted by billfitzmaurice View Post
                    That's the Myth of Underpowering. It simply isn't true. You're not doing the OP or anyone else any good by repeating it.
                    All 3 times I have blown speakers, it was from simply playing music too loudly with a high powered amp.

                    I have seen the Myth repeated on a few forums also.
                    They try to convince people that MORE POWER is the key to not blowing speakers AND/OR the only way to get what the speakers are capable of......

                    I have seen several Myths on a few forums, and some even believe that if the woofers are hitting their excursion limits with a low powered amp, you need more power....LMAO

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                    • #25
                      The part of the under-powering myth that is true: Clipping is dangerous to tweeters.

                      As clipping kicks in, odd order harmonics spike up greatly increasing high frequency power and raising the risk of burning out the tweeter in a passive system. Clipping killing a woofer though... myth. The raw RMS power does increase as you approach a square wave, but you'll hear the distortion way before that power increase is significant. Mathematically, a square wave is double the power of a straight sine at the same peak voltage.
                      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

                      Comment


                      • #26
                        Clipping raises the level of all harmonics, and that can cause tweeters to receive far more power than they can handle, so they can die, from overpowering. It will also cause them to sound really bad, so if you haven't the good sense to turn it down you deserve to get your tweeters toasted.

                        This is short, sweet, and definitive. Note who the author is. Anyone who thinks they're more knowledgeable on the subject need only look at his linkedin page, or google his name.

                        There's no such thing as "underpowering" a loudspeaker.
                        • The loudspeakers really don't care about the shape of the waveform. A square wave is not by itself a killer of tweeters, woofers, etc.
                        • Well over 90% of the power put into a loudspeaker driver turns into heat, whether the waveform is square or not.
                        • Overpowering (thermal damage from too much power) and overexcursion (excessive cone travel, typically from low frequency energy) are what damage loudspeakers.
                        • When an amp clips, it puts out power in excess of its published ratings. Depending on the amp and the loudspeaker, that excessive amount of power may make a seemingly "safe" amp actually quite damaging.
                        Bob Lee Applications Engineer, Tech Services Group QSC Audio
                        Secretary, Audio Engineering Society
                        www.linkedin.com/in/qscbob










                        www.billfitzmaurice.com
                        www.billfitzmaurice.info/forum

                        Comment


                        • #27
                          100% agreed Bill!
                          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

                          Comment


                          • #28
                            Originally posted by billfitzmaurice View Post
                            That's the Myth of Underpowering. It simply isn't true. You're not doing the OP or anyone else any good by repeating it.
                            It's not a myth. Fortunately for you, you haven't spent time with the people I have. They don't want to spend the money on the amps; they drive them to distortion and clipping; blow the speakers and I'm the bad guy. Unfortunately the real world is slightly different than white paper dreams. Drive an amp hard, it gets hot. Power output goes down; distortion goes up and clipping sets in sooner. Boom. Blown speaker. I've reviewed my earlier posts in this thread and I don't see where I recommended pushing drivers past x-max at any given power rating. As anecdotal as it may be, I've seen way more blown speakers from tightwads with too little power (who try to crank it) than I ever have from too much (or adequate) power. It's much safer to have an abundance of power than too little. 35 years don't lie. I appreciate your input but it's slightly skewed (or just a narrartive). More power. Lower temps. Lower distortion. Everybody wins. That sub is 84.5dB. it needs power. and lots of it.

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                            • #29
                              Originally posted by CJB67 View Post

                              It's not a myth. Fortunately for you, you haven't spent time with the people I have. They don't want to spend the money on the amps; they drive them to distortion and clipping; blow the speakers and I'm the bad guy. Unfortunately the real world is slightly different than white paper dreams. Drive an amp hard, it gets hot. Power output goes down; distortion goes up and clipping sets in sooner. Boom. Blown speaker. I've reviewed my earlier posts in this thread and I don't see where I recommended pushing drivers past x-max at any given power rating. As anecdotal as it may be, I've seen way more blown speakers from tightwads with too little power (who try to crank it) than I ever have from too much (or adequate) power. It's much safer to have an abundance of power than too little. 35 years don't lie. I appreciate your input but it's slightly skewed (or just a narrartive). More power. Lower temps. Lower distortion. Everybody wins. That sub is 84.5dB. it needs power. and lots of it.
                              I think you may be missing what or how he is saying it.

                              Low power in itself will not kill a speaker. High power easily can though.
                              And yes I get the Clipping thing, but when ANY amp clips the same thing happens. (Mostly)

                              The likely hood of that happening is easier with a lot of power actually.

                              A 2 watt amp clipping will maybe generate say 5 watts at full clipping, but a 100 watt amp even without clipping, just playing LOUDLY can generate 100 watts,. enough to easily fry some speakers with certain music, let alone clipping.


                              Driving a speaker loudly either with a lot of power, or with decent power clipping a lot, will BOTH destroy some speakers.

                              The Myth is that high power will not....

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                              • CJB67
                                CJB67 commented
                                Editing a comment
                                Never said too much power won't. Anyways, back to the OP's question. He's got a high power handling 84dB (in)efficient sub with a big Xmax. It's going to need the right sized vented or sealed box and a high current power source with a lot of watts. That was my suggestion. Get as much as his wallet can stand. It's always better to have a little left in the tank than not. I seriously don't understand how anyone on this site can't understand and or endorse that. Having said that, kevintomb, I appreciate your sensible and polite reply.
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