Woofers done by Watkins Eng.
Gave a call today and talked to Bill Watkins, great guy. Anyway long story short one/two of the woofers are vibrating nasty at some low frequencies and went on to explain all the stuff I did including replacing the woofers etc, crossover checks and so on. I'm sending them back to him for a checkup to see what's up. So I possed the question about power for these things. Opened up a whole new conversation here. He sent me this response that they have just come up with. And this is the original mail from him, today. So take it for what it's worth.
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Hi John:
I have many people asking me about the Watkins dual-drive woofer, power requirements, etc. In explanation:
In a conventional woofer, an impedance of 8 ohms above resonance (around 45 Hz) rises to 25 ohms or more in the low bass around resonance. As the impedance rises, the power intake is reduced and the bass output drops off. At resonance your 100 watt amp delivers next to no power in the low bass, as the impedance is so great, so no power into the woofer - no low bass. The Watkins dual-drive woofer has two 2 voice coils, one a regular coil to operate above resonance and a second coil to operate at resonance. The second coil is configured such that it’s impedance at resonance is the needed value of 8 ohms. Thus the amplifier can deliver its full power of 100 watts in the low bass, same as in the upper range. Now note this does NOT require EXTRA power, it simply requires the amplifier to deliver the same power in the low bass as in the rest of the musical range. A problem occurs only with a cheap light-weight amplifier that itself cannot deliver its rated power in the low frequency range.
Hope this clears up the myth about vast amounts of power needed for the Watkins dual-drive woofer. So – don’t buy a cheap low current amplifier.
Note if working with 4 ohm speakers, substitute 4 for 8 in the above.
w h watkins
Gave a call today and talked to Bill Watkins, great guy. Anyway long story short one/two of the woofers are vibrating nasty at some low frequencies and went on to explain all the stuff I did including replacing the woofers etc, crossover checks and so on. I'm sending them back to him for a checkup to see what's up. So I possed the question about power for these things. Opened up a whole new conversation here. He sent me this response that they have just come up with. And this is the original mail from him, today. So take it for what it's worth.
______________________________________________________________
Hi John:
I have many people asking me about the Watkins dual-drive woofer, power requirements, etc. In explanation:
In a conventional woofer, an impedance of 8 ohms above resonance (around 45 Hz) rises to 25 ohms or more in the low bass around resonance. As the impedance rises, the power intake is reduced and the bass output drops off. At resonance your 100 watt amp delivers next to no power in the low bass, as the impedance is so great, so no power into the woofer - no low bass. The Watkins dual-drive woofer has two 2 voice coils, one a regular coil to operate above resonance and a second coil to operate at resonance. The second coil is configured such that it’s impedance at resonance is the needed value of 8 ohms. Thus the amplifier can deliver its full power of 100 watts in the low bass, same as in the upper range. Now note this does NOT require EXTRA power, it simply requires the amplifier to deliver the same power in the low bass as in the rest of the musical range. A problem occurs only with a cheap light-weight amplifier that itself cannot deliver its rated power in the low frequency range.
Hope this clears up the myth about vast amounts of power needed for the Watkins dual-drive woofer. So – don’t buy a cheap low current amplifier.
Note if working with 4 ohm speakers, substitute 4 for 8 in the above.
w h watkins
