FREQU RESPONSE @0dB 20 SEC [s]
| 20Hz | -18.00 | 0.00 | |
| 31Hz | -14.75 | 0.00 | |
| 40Hz | -9.62 | 0.00 | |
| 50Hz | -11.25 | 0.00 | |
| 100Hz | -2.62 | 0.00 | |
| 315Hz | -1.00 | 0.00 | |
| 1k0 | 0.00 | 0.00 | |
| 6k3 | +0.88 | 0.00 | |
| 10k0 | +1.50 | 0.00 | |
| 12k5 | +0.50 | 0.00 | |
| 14k0 | -2.87 | 0.00 | |
| 16k0 | -7.37 | 0.00 | |
| 20k0 | -15.00 | 0.00 | |
| 25k0 | -18.00 | 0.00 | |
This little speaker drive unit demonstrates the advantages of High-BL (it has a very big magnet for its size). This makes compensation down to 30Hz feasible at low levels.
As well as giving high sensitivity (88dB for 1 watt specified) this gives 'tight-coupling' resulting from back-emf feedback. This damps any bass resonance and also holds up the bottom end giving a roll-off closer to 12dB/octave than the 18db/octave otherwise expected. See the Visaton FR8 for comparison (both cost around £5 from CPC).
The roll-off above 15kHz and the large peak and dip around 2kHz make this unit more of a bass driver than a full-range device. The 2kHz anomoly is believed to demonstrate a common weakness of rubber roll surrounds - they allow long throw for bass use, but cause reflection of the compression wave travelling through the cone. Foam or paper surrounds can be designed to provide a matched impedance which absorbs energy at the edge of the cone, minimising the effect. |
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