On the Bench

1000i

The microphone was placed 12" from the middle of the panel for the distortion tests, and 1 meter for the room response test. I used a standard SPL value of 90 dB instead of 100 dB since half the sound was going out the rear, away from the microphone. THD+N measurements were within a 10 Hz to 22 kHz bandwidth.

At 100 Hz, THD+N was less than 4%. This is somewhat more than you might find with a conventional woofer driver, and as I mentioned, ESLs have a tough time with low bass.

At 1 kHz, 0.5% THD+N.

And, at 10 kHz, THD+N was 0.8%. This is less than many other conventional tweeters.

IMD using a SMPTE/DIN standard test, was 0.8%. I could test this (IMD) here because the 1000i panel reproduces both sine waves, rather than a tweeter reproducing one and a woofer reproducing the other.

The room response was reasonably flat down to about 60 Hz. The deep valleys are room issues. It rolled off a bit above 16 kHz.

The impedance stays at least 8 ohms up to about 1 kHz, then goes down to a low of slightly less than 2 ohms at 12 kHz. The large peak is due to the transformer. It stays below 4 ohms between 4.5 kHz and 20 kHz, so you should use a good amplifier that is rated into 2 ohms. As the sensitivity is only 86 dB, I would suggest at least 200 watts per channel.

The second graph shows the same impedance curve in an expanded scale.

The electrical phase stays within ± 60⁰.

Go to Part V.