Some Quick Sub Measurements

[Spkrboy]

While I was setting up my test software/hardware to get after the measurements of Komoman's new speakers, I did some quick measurements of three subs. A JL Audio 8W3v3 (8 ohms, red trace), ED 9kvD2 (4 ohms, green trace) and Vifa M22WR09-06 (6 ohms, pink trace) were all measured using identical drive levels for nearfield response. Notice how much better the Vifa is and how it can even be used as a midbass up to around 500 Hz. The ED should have had a substantial advantage in SPL because it had the lowest configured impedance, but it did really no better than The 8-ohm JL. Measurements are valid down to 30 Hz here. And here are the JL and ED drivers in a 0.3 ft^3 box. There's still no advantage to the lower impedance.

[robvuk]

When you say identical drive level, do you mean identical voltage? Or power, based on the claimed impedance? Did you run an impedance plot? I see approximately 3db of difference below 80hz which would account for the impedance if they based the impedance claim in that bandwidth.

[Spkrboy]

Originally Posted by robvuk

When you say identical drive level, do you mean identical voltage? Or power, based on the claimed impedance? Did you run an impedance plot? I see approximately 3db of difference below 80hz which would account for the impedance if they based the impedance claim in that bandwidth.

Identical voltages. That's why there's no advantage to the lower-Z driver as it's getting twice the current. I did this as a quick example of why there's no need for people to be concerned with 4- vs 8-ohm speakers as some often worry about. Impedance plots were run way back when I did the first round of tests for these drivers.

The opportunity came up now for this comparison because I was setting up my test hardware and needed some known samples to verify all was in working order.

[robvuk]

Originally Posted by Spkrboy

Identical voltages. That's why there's no advantage to the lower-Z driver as it's getting twice the current. I did this as a quick example of why there's no need for people to be concerned with 4- vs 8-ohm speakers as some often worry about. Impedance plots were run way back when I did the first round of tests for these drivers.

The opportunity came up now for this comparison because I was setting up my test hardware and needed some known samples to verify all was in working order.

There's no difference in efficiency whether it's 4 or 8 if the motor assembly is the same. It's only a matter of convenience/preference for any particular install or optimizing amplifier power.