According to Power Dynamics their 8" Ceiling speaker (PD CSPB8) bottoms out @ 100hz. Is there any point in using a high-pass filter to provide resistance to frequencies they don't respond to?
I ask because I'm considering using of a passive sub. The sub is 6ohms. The ceiling speakers are 8ohms.
I ask because I'm considering using of a passive sub. The sub is 6ohms. The ceiling speakers are 8ohms.
A HP filter could keep low frequencies from distorting the ceiling speaker, and the amp won't waste as much power heating it's voice coil.
I'll add a third and probably the most important reason.
Your ceiling speaker will DIE if you don't limit the frequencies below 100Hz.
Your ceiling speaker will DIE if you don't limit the frequencies below 100Hz.
Sorry guys, I still don't understand the depths of driver frequency response. I had two 6.5" woofers. One Sony, One Skytec. Feed a 40Hz sine wave in free air, the Sony would go nuts, threatening to hit Xmax. The Skytec largely ignored the single. emitting a very faint hum, with little or no cone movement.
Impedancewise, How does an amplifier see a driver that doesn't respond to its signal?
Impedancewise, How does an amplifier see a driver that doesn't respond to its signal?
The impedance the amplifier sees may look something like this:
This "8 ohm" ceiling speaker's impedance peak (Fs) is near 100 ohms, below the impedance peak frequency it drops under 8 ohms.
At 40Hz, the response is -20dB, ("a very faint hum") but the voice coil is drawing (wasting..) almost the same power as the parallel 6 ohm woofer.
The stiff suspension and short voice coil allow very little cone movement (hence very little SPL), but the voice coil may still be driven partially out of the magnetic gap, causing amplitude modulation (AM) distortion of the high frequencies when too much bass is applied.
This distortion makes voices sound like they are "gargling".
The ceiling speaker is probably far more sensitive than the woofer, so "too much bass" will be applied to sound balanced.
A 150-200 microfarad non-polarized capacitor in series would raise the impedance the amp sees, and reduce AM distortion.
A series resistor would reduce the ceiling speaker SPL and reduce the value of the capacitor required for a given crossover frequency.
This "8 ohm" ceiling speaker's impedance peak (Fs) is near 100 ohms, below the impedance peak frequency it drops under 8 ohms.
At 40Hz, the response is -20dB, ("a very faint hum") but the voice coil is drawing (wasting..) almost the same power as the parallel 6 ohm woofer.
The stiff suspension and short voice coil allow very little cone movement (hence very little SPL), but the voice coil may still be driven partially out of the magnetic gap, causing amplitude modulation (AM) distortion of the high frequencies when too much bass is applied.
This distortion makes voices sound like they are "gargling".
The ceiling speaker is probably far more sensitive than the woofer, so "too much bass" will be applied to sound balanced.
A 150-200 microfarad non-polarized capacitor in series would raise the impedance the amp sees, and reduce AM distortion.
A series resistor would reduce the ceiling speaker SPL and reduce the value of the capacitor required for a given crossover frequency.
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