This blog post features the Altec 806-8A compression driver mounted to the ES-600 Biradial using a 1" throat. I purchased a pair of these drivers used to see how they would perform. After enjoying the TAD TD-2001's I was curious how these would sound since they both share alnico magnets and the Altec 806-8A is highly regarded by some enthusiasts.
Test Setup
The test setup was done in my living room using a 5ms gate to eliminate the room's reflections down to about 1kHz. All measurements were done at 1 meter mic distance from the horn mouth.
Measurements
Altec 806-8A on ES-600 Biradial
Impedance Curve
The impedance curve data shows a fundamental resonance (FS) at 365Hz however there is a strong resonance at 2kHz. The driver shows strong inductive rise starting at 3kHz.
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Altec 806-8A with ES-600 Biradial Horn |
Frequency Response
The frequency response shows some excess energy around 1.5kHz and then dips -7dB at 2.2kHz. Response linearity is below average from 2kHz-8kHz. There is a sharp falling response starting at 8kHz with very little output above 10kHz.
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Altec 806-8A with ES-600 Biradial Frequency Response |
Step Response
Step response takes about 2.25 milliseconds to settle. This is about 20% longer than the RCF ND-350 and 50% longer than the TAD TD-2001.
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Altec 806-8A with ES-600 Biradial Step Response |
Burst Decay
Burst decay shows strong resonances at 4kHz and 7kHz.
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Altec 806-8A with ES-600 Biradial Burst Decay 35dB Scale, 5ms gate |
Subjective Listening Impressions
I spend a few days listening to a stereo pair of the Altec 804-8A with the ES-600 in my small listening room.
Below is a ranking for my subjective impressions on the sound quality...
Soundstage Depth --- 4/10
Soundstage Width --- 6/10
Smoothness --- 5/10
Coherence between midrange and treble --- 5/10
Coherence between mid-bass and midrange --- N/A
Vocal Clarity Male --- N/A
Vocal Clarity Female --- 6/10
Accurate Musical Instrument timbre --- 7/10 (some older recordings did well on this)
Sense of Dynamic Range: --- 7/10
Conclusion
The Altec 806-8A exhibits some of the smoothness and sound signature of alnico however there are other performance metrics that causes the Altec to fall short. Overall I would not recommend this driver since it does not meet the performance target required for my products. "It takes two to tango"...and so the driver must match the horn in terms of sound quality which the Altec fails to do.