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Oscilloscope, overhyped and underexplained
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<blockquote data-quote="TDot" data-source="post: 8250494" data-attributes="member: 645311"><p>My subs never sounded as loud as they should have been. My home system with less amps were louder. Following directions here I used an oscilloscope alone. Not liking the results I overcompensated in the wrong ways I burnt up two subs...until today.</p><p></p><p>All over this forum, and YouTube I see people constantly saying the same thing. "Use an oscilloscope to set your gains." And I fell in the trap...even though I knew better. Here's the problem, doing that alone leaves A LOT of Dbs on the table not giving you the maximum output. For most of the people here that may not be a problem because you are running monster amps and multiple subs trying to crack the concrete and give neighbors migraines. But people like me running 500wrms, every volt counts.</p><p></p><p>Here's the problem, when a 40hz...or whatever...test tone is used, its a constant tone, constant rms at a set db. No song has a 0db between 0 and 70/80 hz. So why am I setting my amp sub to that. For the purpose checking if our amp/head unit is putting out a clean signal at what they are rated is a good idea to use a oscilloscope, but not to set at the maximum point.</p><p></p><p>After setting with an oscilloscope, if you have a computer/spectrum analyzer tuned you can see between any song you'll have between 5 and 20 db of headroom at 0-70hz (average seems to be 8db headroom at 40hz, at least with my music). That's A LOT of volume to not take advantage of. Remember, 10db = double perceived volume, so 5db is a nice bump. Of course the further up you go in the frequency the more db will be there after using an oscilloscope, which makes using it a safe route. Ex. a song with 40hz hitting at -5 may have 500hz hitting at +0 and thus clipping, so that does need to be taken into consideration when doing this without an oscilloscope. But most people cut their subs off below 200hz so it shouldn't be a problem.</p><p></p><p>Some will say you should be able to listen for clipping. Here's the problem, its not easy listening for clipping in a sub when you have the high end cut out, and suffering from ear fatigue. On top of that A LOT of songs are simply horribly recorded since the early 90s. It can be hard to discern distortion mastered into the recording and clipping unless the speaker is actually physically being affected by "baffling"(I think that's the term) a bit. And then if you do find a song that is perfectly engineered and mastered, they are generally not mastered as loud as the rest of the songs are, so it will end up being a waste of time.</p><p></p><p>So, my suggestion to people just starting this, don't run with the hype of "just set your gains with an oscilloscope." You will be thoroughly disappointed unless you are running a monster. Using an oscilloscope alone could work at the midrange point, 1khz, because songs are usually zeroed in that area, but not the sub.</p><p></p><p>1/ use an oscilloscope to CHECK YOUR SIGNAL</p><p></p><p>2/ use a spectrum analyzer to set your gains according to the average of your music</p><p></p><p>3/ use your ears</p><p></p><p>Now my sub is perfect, loud, clean, and balanced.</p><p></p><p>Just my opinion and experience...not preaching.</p></blockquote><p></p>
[QUOTE="TDot, post: 8250494, member: 645311"] My subs never sounded as loud as they should have been. My home system with less amps were louder. Following directions here I used an oscilloscope alone. Not liking the results I overcompensated in the wrong ways I burnt up two subs...until today. All over this forum, and YouTube I see people constantly saying the same thing. "Use an oscilloscope to set your gains." And I fell in the trap...even though I knew better. Here's the problem, doing that alone leaves A LOT of Dbs on the table not giving you the maximum output. For most of the people here that may not be a problem because you are running monster amps and multiple subs trying to crack the concrete and give neighbors migraines. But people like me running 500wrms, every volt counts. Here's the problem, when a 40hz...or whatever...test tone is used, its a constant tone, constant rms at a set db. No song has a 0db between 0 and 70/80 hz. So why am I setting my amp sub to that. For the purpose checking if our amp/head unit is putting out a clean signal at what they are rated is a good idea to use a oscilloscope, but not to set at the maximum point. After setting with an oscilloscope, if you have a computer/spectrum analyzer tuned you can see between any song you'll have between 5 and 20 db of headroom at 0-70hz (average seems to be 8db headroom at 40hz, at least with my music). That's A LOT of volume to not take advantage of. Remember, 10db = double perceived volume, so 5db is a nice bump. Of course the further up you go in the frequency the more db will be there after using an oscilloscope, which makes using it a safe route. Ex. a song with 40hz hitting at -5 may have 500hz hitting at +0 and thus clipping, so that does need to be taken into consideration when doing this without an oscilloscope. But most people cut their subs off below 200hz so it shouldn't be a problem. Some will say you should be able to listen for clipping. Here's the problem, its not easy listening for clipping in a sub when you have the high end cut out, and suffering from ear fatigue. On top of that A LOT of songs are simply horribly recorded since the early 90s. It can be hard to discern distortion mastered into the recording and clipping unless the speaker is actually physically being affected by "baffling"(I think that's the term) a bit. And then if you do find a song that is perfectly engineered and mastered, they are generally not mastered as loud as the rest of the songs are, so it will end up being a waste of time. So, my suggestion to people just starting this, don't run with the hype of "just set your gains with an oscilloscope." You will be thoroughly disappointed unless you are running a monster. Using an oscilloscope alone could work at the midrange point, 1khz, because songs are usually zeroed in that area, but not the sub. 1/ use an oscilloscope to CHECK YOUR SIGNAL 2/ use a spectrum analyzer to set your gains according to the average of your music 3/ use your ears Now my sub is perfect, loud, clean, and balanced. Just my opinion and experience...not preaching. [/QUOTE]
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