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Old 8th January 2011, 05:08 AM   #1
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Default Tweeter draw lesser current than mid-woofer?

Example, if the tweeter impedance around 10-20ohm in certain frequency.
Higher output voltage will benefit from this frequency range,right?
How if mid-woofer impedance around 4ohm and the amplifier couldnt supply enough current since the voltage is too high. the sound will just clipped away?

Usually people pair the speakers with, amp's output power within speakers recommended power rating or higher than maximum power rating of speakers?
or higher than minimum power rating will do? as I know double the wattage will get 3dB louder only.

Last edited by cent88; 8th January 2011 at 05:11 AM.
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Old 8th January 2011, 06:44 AM   #2
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Electrons are istantaneuosly adaptative and they flow where less resistance is .
Higher coils impedance makes them generally more efficient (the speakers) ,but the peak is where resonance is placed ,and that is defined by the electro-mechanical parameters (cone mass ,suspension ,coil ...magnets): usually the task of the crossover network is to make see a flat impedance to the amplifier , and to have the speakers working in their flat impedance region .This can be done with midrange and tweeters ,but you'll have to cope with the huge peak
at resonance frequency of the woofer . Some 'flattening' comes from the box ,or from the room if it's a 'dipole' ,but a lot of work has to be done by the amplifier :at high power it may not be easy to maintain a perfect and constant tracking of the waveform when the load is not purely resistive ,but has mixed inductive and capacitative ...behaviors
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Old 8th January 2011, 09:12 AM   #3
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In my confusing rambling on electroacustics Since tweeter's cone mass may be considered negligible ,it is not in a woofer . And the box may be considered as a 'spring' when it is closed (pneumatic suspension) at it is a simpler approach to the issue of back radiance of the membrane ,which may lead to alterations of the impedance curve (aberrations....)that are the result of a not well implemented control of the internal reflections of the box ,in particular the stationary waves that frequently occur when the cabinet is tall .

Regarding Cent88 ,about power and clipping ,there's also distortion or THD
which is not Thermonuclear Hydrogen Distortion ...but similar : when everything is well balanced ,the setup is OK ,you'll hear clearly the distortion
originating from bad clipping of the amps or excess heating from the speaker's coils .
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Old 8th January 2011, 10:31 AM   #4
AndrewT is offline AndrewT  Scotland
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Am I allowed to simply the question by considering a 2way speaker with it's own passive crossover, so that a Xvoltage within the passband frequency will result in Y SPL from the speaker? This is equivalent to saying that the speaker has a flat frequency response within it's passband.

Now let's also assume that two equal impedance drivers are used in the 2way speaker.

The impedance of the crossed over speaker will vary over the passband frequencies.

Pick two frequencies, one in the midband and one in the treble band where the phase and impedance are the same.

Apply X volts and you will get Z amps at both frequencies.
find two frequencies where the phase is the same but the impedance is exactly doubled.
Now for X input volts you will have Z amperes at one frequency and 0.5*Z
amperes at the other frequency.

Now let's move away from a 2way and select a mid driver and a treble driver with the same impedance and the same sensitivity.
Here again X volts will give rise to Z' amperes at both frequencies if the phase and impedance are the same at both frequencies.

From the above you can arrive at X & Z' for any driver impedance and any driver sensitivity.

The biggest difference between the signals/voltages/currents fed to the different passbands of the drivers is the duration of the signal. The signals are very short duration into the treble, medium duration to the mid driver and long to the bass driver.

Finally, let's look at how often the peak values of these different frequencies are fed to the respective drivers.
The bass see regular and fairly frequent signals of long duration creating the potential for a lot of energy transfer to the voice coil.
The mid see very frequent signals of medium duration, again creating the potential for a lot of energy transfer to the voice coil.
The treble see infrequent signal of short duration, leading to very low energy transfer to the treble voice coil. The treble driver can be relatively fragile in comparison the the other drivers and still survive high peak transient signals, both in terms of voltage and of current and survive because the treble does not get hot.
Provided the peak treble signals remain infrequent and short duration. Clipping of the music signal destroys treble drivers because it breaks this fundamental requirement for infrequent and short duration.
regards Andrew T.
Sent from my desktop computer using a keyboard

Last edited by AndrewT; 8th January 2011 at 10:44 AM.
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Old 8th January 2011, 05:36 PM   #5
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I hope I got it right. haha.
the crossover is also matched to give flat response of speaker?
For a speaker with SPL vs Frequency +/- 3dB, which mean I will get a flat SPL as long as I supply the speaker with recomended power and correct voltage?

I forgot to sum up the crossover impedance vs frequency previously, when I 1st saw the impedance vs frequency graph(I thought that is the impedance of speaker drivers alone).

and for clipping, is it adviced not to maximize the volume pot when there is a high input signal? as too much gain will force the amp to supply more power than it can supply.

for high-pass crossover, usually capacitor is in series with tweeter? does it protect the tweeter from clipping(block DC?).
and there is no capacitor in series with sub, so this is why people blown their sub when clipping occur?

Last edited by cent88; 8th January 2011 at 05:41 PM.
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