What's with 4 ohm speakers?

"The statement is ambiguous. We know that doubling power is 3db, and that there is or should be a direct correlation with driver output. Since this is so then driver output is also proportional to power."

Wouldn't you have to take other factors into consideration like how the room interacts with the speaker, or possibly, the distance from the speaker to where the measurement is taken? Or is there some type of industry standard and everyone measures these type of things the same way?

Atmasphere writes
> I wrote:
> Those of us with a little technical knowledge accept and expect it because at lower frequencies dynamic loudspeaker driver output is proportional to voltage.

>The statement is ambiguous. We know that doubling power is 3db, and that there is or should be a direct correlation with driver output. Since this is so then driver output is also proportional to power.

Nope. You're confusing voltage and power where power is voltage squared divided by impedance.

Reactive impedance varies with frequency. Inductive impedance magnitude is 2 pi f L with f ferquency in Hz and L inductance in Henries. Capacitive impedance magnitude is 1 / 2 pi f C with capacitance in Farads.

Driver + enclosure combinations are reactive loads with their mechanical parameters reflected in the electrical characteristics at the driver terminals. The driver's in-enclosure compliance Cms shows up as an inductive reactance Lces. The moving mass Mms works as a capacitive inductance Cmes.

Driver voice coils are inductive which also causes impedance to increase with frequency.

You can have a 40 Ohm maximum impedance at driver + enclosure resonance with impedance around a driver's 6 Ohm voice coil resistance as you move through its pass-band before its voice coil inductance becomes significant and increases to 20 Ohms before leaving the audible spectrum.

Over the same range the same voltage can yield the same output. 2.83V might be 90dB SPL although that varies somewhere between 1/5W and 1 1/3W electrical.

As noted complete speakers complicate things more. You get increased output as the speaker transitions from full to half space radiation (baffle step) and can have rising response as driver directivity increases with frequency. When cross-over designers compensate for that with a series load power impedance increases at those frequencies and power dissipated decreases.

Amplifiers which don't accommodate these physical realities with terminal voltage that's a fixed multiple of input voltage regardless of load impedance aren't universally useful in high-fidelity applications for speakers having impedances that are otherwise compatible causing neither instability nor power dissipation issues.

I should probably proof-read better before posting
>The moving mass Mms works as a capacitive inductance Cmes.

capacitive impedance

>When cross-over designers compensate for that with a series load power impedance increases at those frequencies and power dissipated decreases.

series load impedance increases at those frequencies and power dissipated decreases.

Or is there some type of industry standard and everyone measures these type of things the same way?

They are supposed to, anyway. Of course the room is important, about 1/2 of the total system sound, IME.

>The statement is ambiguous. We know that doubling power is 3db, and that there is or should be a direct correlation with driver output. Since this is so then driver output is also proportional to power.

Nope. You're confusing voltage and power where power is voltage squared divided by impedance.

Sorry - not confused. I am quite literal though. If you are saying there is not a proportion then you are contradicting yourself. But I suspect we are arguing semantics. To clarify I was simply stating that +3 db more watts is twice as many watts.

Amplifiers which don't accommodate these physical realities with terminal voltage that's a fixed multiple of input voltage regardless of load impedance aren't universally useful in high-fidelity applications for speakers having impedances that are otherwise compatible causing neither instability nor power dissipation issues.

Certainly this is true. However not all speakers have this requirement of an amplifier- such speakers can be incompatible with amps that are capable of Constant Voltage behavior. Rather than repeat myself ad naseum I invite you to go back to an earlier point in this thread an look for a link I dropped to an article on the Voltage and Power paradigms, so you can catch up on the conversation.

Whats' with 4 ohm speaker's? Its the damn drivers. Many of the tweeter's on the market from RAAL, ScanSpeak and other's have a 4 ohm impedance.