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Thread: Underpowering JBL 250TIs....??

  1. #46
    Senior Member kingjames's Avatar
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    I prefer to rattle windows and not break them. My old ass Pioneer SX1250 pushes these speakers just fine. I only go up to 12 O'Clock on the dial and it's so loud my office windows rattle. What more is needed here? I don't turn it all the way up because this power is not necessary.Where does this clipping come in? When you're amp is maxed!

    Everone assumes that they are gonna max the volume on their amp my question would be why would you want to do that because true 50 watts of power is quite loud. I don't mind the neighbor's across the street listening to my system but people down the block got nothing coming.

    If you're intent is to max the volume on you're amp all the time then it is wise to get a more powerful amp but if you are gonna run it say around 12 o'clock like I do then what you have is quite sufficent.

    After all who listen's to their stuff at full throttle?

  2. #47
    Senior Member louped garouv's Avatar
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    I have my amps set to wide open, but the preamp normally only gets up to 3 or 4....

    every once in awhile, i'll push it up to 6/7...

    nice to be able to do so if the need arises....

  3. #48
    Senior Member louped garouv's Avatar
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    Quote Originally Posted by grumpy View Post
    Marty DiBergi: Why don't you just make ten louder and make ten be the top number and make that a little louder?
    Nigel Tufnel: [pause] These go to eleven.
    http://www.philasound.com/Steve_Dash.htm





  4. #49
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    Storm,

    One of your "concerns" was blowing the precious 044Ti tweeters.

    Just remember that as the 250's are a four way, they have a relatively high crossover point to the tweeter (5.2kHz). That helps to limit the amount of power fed into the unit at the lower frequencies and that really helps with the power handling of the driver. I understand that the crossiver does use a 6dB slope though which reduces some of the advantages of the high x-over point but you can see what I mean.

    Having said that, an amp clipping heavily would still kill them fast enough.

  5. #50
    Moderator hjames's Avatar
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    You don't get it - the amp goes into clipping when it is called to reproduce a signal outside its limits. For the obvious example - lets say you play the 1812 overture. Sound is nice, not too loud but full and robust - suddenly - BOOM BOOM BOOM - the Cannons fire. Those cannons are a huge leap of volume above what your normal listening levels are. You may have been running your 50 watt amp at 1/2 level, but that cannon wants 10 times the power to play those sudden sharp reports accurately. Your amp doesn't HAVE 500 watts, so the waveform flattens out - it no longer is the same as the input signal, it has distorted, or clipped the signal. That my friend, is the distortion and clipping they speak about.
    Its not average levels that this happens, its the sudden peaks.

    Now, if all you listen to is the smooth "jazz" stylings of say, Kenny G, there may be no dramatic peaks in your music, this may never happen. But most folks into classic rock or the classics do get sudden peaks.

    Zat help?

    Quote Originally Posted by kingjames View Post
    I prefer to rattle windows and not break them. My old ass Pioneer SX1250 pushes these speakers just fine. I only go up to 12 O'Clock on the dial and it's so loud my office windows rattle. What more is needed here? I don't turn it all the way up because this power is not necessary.Where does this clipping come in? When you're amp is maxed!

    Everone assumes that they are gonna max the volume on their amp my question would be why would you want to do that because true 50 watts of power is quite loud. I don't mind the neighbor's across the street listening to my system but people down the block got nothing coming.

    If you're intent is to max the volume on you're amp all the time then it is wise to get a more powerful amp but if you are gonna run it say around 12 o'clock like I do then what you have is quite sufficent.

    After all who listen's to their stuff at full throttle?
    2ch: WiiM Pro; Topping E30 II DAC; Oppo, Acurus RL-11, Acurus A200, JBL Dynamics Project - Offline: L212-TwinStack, VonSchweikert VR-4
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  6. #51
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    That is an extreme and obvious example in which they warn on the label.

    For a thorough and correct explanation refer to John Eargle's publication.

    http://www.amazon.co.uk/Handbook-Rec...5883986&sr=1-3

    It has more to do with the relative sensitivity of the loudspeaker, the listening distance and the maximum undistorted SPL required at that distance. In the above manual 6 db is suggested as the minimum headroom and while peak to average power can vary considerably depending on the recording the case of a 50 watt amp with would mean a 200 watt amp.

    As a practical matter a significantly more powerful amplifier as in a 400 watt / channel model does have audibly more dynamic range. This is noticably typically on a piano or trumpet sole and not Telarc demonstration disks.. The transients which the JBL is noted for are otherwise flattened and the scale of dynamic contrast will be diminished.

    Although a now out dated design I previously used a Phase Linear 700 Series 11 Clair Bros model. Subjectively that amplifier was vastly superior to a 100 watt amp in terms of dynamic capability at any volume level. The threshold of clipping was 450 watts a side. I only ever used it once in a pro application and that driving a pair of 2 way J bins for a band where the 2226 drivers were pushed to extraordinary levels (over 1 inch p-peak) but with incredible control and they survived to play anoher day.

    Of course this is only useful if the loudspeaker can handle the transients which is the case with the L250.

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  8. #53
    Senior Member BMWCCA's Avatar
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    Gain structure

    Quote Originally Posted by louped garouv View Post
    I have my amps set to wide open, but the preamp normally only gets up to 3 or 4....

    every once in awhile, i'll push it up to 6/7...

    nice to be able to do so if the need arises....
    Not really the best way to run the amp with respect to pre-amp output and its effect on S/N ratio and pre-amp output voltage. I've probably posted this before, since it was in response to my question on power-amp input-attenuator controls (which is what some incorrectly call "volume controls"), but here again is the reply---snipped for brevity---from Crown on their forum:
    When setting the Gain Structure of a system up properly you should set the mixer and preceding gear to be hitting 0VU at the maximum you would be running the system. Then turn the amp up for as loud as you need it. This way you know that when the mixer levels are hitting 0VU the system will be driving the amp with enough to go full volume (if the input attenuators were turned all the way up). If you don’t need the system this loud turn down the amps and you will still have the best System Signal to Noise.

    If you turn the amp up all the way or always to a higher setting than most of the time you will be running the mixer in the area were the mixers output is very low with very little meters. When running a mixer at these lower levels the audio signal is closer to the mixers noise floor and all the system gain will be at the amp. However, with the system gain at the amp the audio signal and the mixers noise floor are so close that now the noise floor (of the mixer) gets amplified as well causing a hissy output at the speakers.

    This is why amplifiers have volume controls and why it is best to set the mixer and preceding gear to be hitting 0VU at the maximum you would be running the system. Then turn the amp up for as loud as you need it for the room.

    When working with a non-metered Preamp 3/4 of the way up, on the preamp output, is a good place to start as this is usually about the nominal output.
    If you're interested in reading the entire reply and give-and-take around it, here's the thread link.

  9. #54
    Senior Member sourceoneaudio's Avatar
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    Quote Originally Posted by hjames View Post
    You don't get it - the amp goes into clipping when it is called to reproduce a signal outside its limits.
    Heather,
    He never gets it.........

    Quote Originally Posted by Andyoz View Post
    Storm,

    One of your "concerns" was blowing the precious 044Ti tweeters.

    Just remember that as the 250's are a four way, they have a relatively high crossover point to the tweeter (5.2kHz). That helps to limit the amount of power fed into the unit at the lower frequencies and that really helps with the power handling of the driver. I understand that the crossover does use a 6dB slope though which reduces some of the advantages of the high x-over point but you can see what I mean.
    Hey Andy,
    The tweet uses a 12db slope from what I'm looking at.
    Jeff-S1A

  10. #55
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    Quote Originally Posted by sourceoneaudio View Post
    The tweet uses a 12db slope from what I'm looking at.
    Cool, even better. That's nearly an octave higher than used on the 18Ti (for example)

  11. #56
    Senior Member louped garouv's Avatar
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    Quote Originally Posted by BMWCCA View Post
    Not really the best way to run the amp with respect to pre-amp output and its effect on S/N ratio and pre-amp output voltage. I've probably posted this before, since it was in response to my question on power-amp input-attenuator controls (which is what some incorrectly call "volume controls"), but here again is the reply---snipped for brevity---from Crown on their forum:If you're interested in reading the entire reply and give-and-take around it, here's the thread link.

    thanks for the tip, I read that before somewhere, but it must have slipped my mind....

    i'll try it the other way too....





    when i bring the system outside, i am much more likely to run the preamp closer to unity....

    it's just to damn loud and unsafe to do so in a home....

  12. #57
    Senior Member Storm's Avatar
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    Source,

    I do get it, but when another 250TI owner PM's me and tells me that he runs just fine with under 200 watts, then I am feeling more comfortable with my NAK. But thank you for the bashing, anyway's.

    I don't have extra money laying around to buy another amp.

    I have played the 1812 overture and at loud volumes, and no clipping occurred.

    -Storm



    Quote Originally Posted by sourceoneaudio View Post
    Heather,
    He never gets it.........



    Hey Andy,
    The tweet uses a 12db slope from what I'm looking at.

  13. #58
    Senior Member kingjames's Avatar
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    Quote Originally Posted by hjames View Post
    You don't get it - the amp goes into clipping when it is called to reproduce a signal outside its limits. For the obvious example - lets say you play the 1812 overture. Sound is nice, not too loud but full and robust - suddenly - BOOM BOOM BOOM - the Cannons fire. Those cannons are a huge leap of volume above what your normal listening levels are. You may have been running your 50 watt amp at 1/2 level, but that cannon wants 10 times the power to play those sudden sharp reports accurately. Your amp doesn't HAVE 500 watts, so the waveform flattens out - it no longer is the same as the input signal, it has distorted, or clipped the signal. That my friend, is the distortion and clipping they speak about.
    Its not average levels that this happens, its the sudden peaks.

    Now, if all you listen to is the smooth "jazz" stylings of say, Kenny G, there may be no dramatic peaks in your music, this may never happen. But most folks into classic rock or the classics do get sudden peaks.

    Zat help?
    What causes an amp to reproduce a signal outside it's limit? Is the volume control the culprit or the signal.I can run my 250ti's at say 50 watts and they sound beautiful and my receiver can handle the extra load.I am in my 50's as you all know and I am trying to understand the logic here.

    I bought a 160 watt per channel receiver because I figured the extra power though not needed for my listening pleasures was better to have it as the receiver wouldn't strain under high volume.

    I am not sure of all the electronics being spoken here but I get great enjoyment out of my setup and at times on a particular song I will crank it up a little and my speakers love it however even I can only take so much volume.

    In the end I run my receiver at 12 o'clock on the dial at most times and is quite loud in fact loud enough where I can hear it all the way out of my front door. I figure this is the loudest that I can handle before the music is annoying to me.Understand though that half way up on this receiver is very loud and will reproduce any sound from any source the way it should be heard.I guess I just don't get it. I just don't get why I should buy a 400 watt amp when my 70's receiver that I only paid $500.00 for can do the job and then some.

  14. #59
    Senior Member Storm's Avatar
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    Quote Originally Posted by grumpy View Post
    Did someone suggest you should? Sounds like you're fine to me.

    -grumpy
    I think he is stating that because the overall concensous is for me to get a better amp. However, some agree that my amp is good enough.

    My pre-amp volume level is at about 10 O Clock -- and that is plenty loud for me.



    -Storm.

  15. #60
    Senior Member kingjames's Avatar
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    Quote Originally Posted by grumpy View Post
    when the input signal, multiplied by the amplifier gain exceeds the power supply limit
    (or triggers protection circuits).

    Your volume knob is there to attenuate the input signal
    before it gets to the amplifier (which has fixed gain ... probably in the neighborhood of
    20dB... unless there's some pre-amp gain too...maybe 6-10dB)

    WIth your equipment (CD, tuner, whatever) the 12 o'clock position just happens to be
    where you've found a reasonable limit. Home audio equipment tends to have a maximum
    output of 1-2volts. Turning your amp all the way up would probably result in clipping.
    If you had a component that had a weaker (comparatively) output, you could turn up the
    volume more than 12 o'clock to get the same apparent loudness. In other words, the
    volume knob does not -set- how many watts come out of the amplifier... it just reduces
    the input signal before it gets the the power amplifer section.

    Did someone suggest you should? Sounds like you're fine to me.

    -grumpy
    I noticed on my receiver that most of the volume comes in after 12 0'clock.I don't believe I am getting half the volume at 12 0'clock as after 12 0'clock the volume shoots up dramatically.However you're explanation makes sense.I am fine with my setup and I was trying to find out why my system would blow my 044ti's when I find that everything I have is matched for my listening pleasure.

    I guess I can be thankful that I am in my 50's because there was a day I would have blown any speaker and have blown quite a few of them because it seemed I was never satisfied with the volume.Alway's had to max them out.Was costly in the end.Now I enjoy music at a moderate level.

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