The Significance of Speaker Impedance – Avantgarde’s Change from 8 to 18 Ohms

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When I first started dabbling with loudspeaker design and my own DIY efforts, virtually all hi-fi speakers were rated at 15 ohms.

Then rather rapidly the industry moved to 8 ohm speakers.

Why? Was it the transition from tube to solid state amplification that prompted this wholesale change in speaker design?

And why have a few brands more recently gone the other way?

Example - Avantgarde horn speakers. Avantgarde didn’t exist in the old 15-ohm days, but their Unos, Duos and Trios were all introduced in the late 1990s at the then standard 8 ohm nominal impedance. Then in about 2006, their new Omega range saw the drivers changed to nominal 18 ohms.


So much was claimed of these new drivers that many Duo owners parted with significant sums of hard-earned cash to change the drivers in their speakers to Omega ones - and everyone crowed over how huge the improvement was - perhaps they had to say that after spending so much. Let’s be generous and agree on this as a genuine and significant improvement in sound quality, but perhaps the new drivers were simply better irrespective of their new impedance. Avantgarde speakers remain at this 18 ohm impedance to this day.



Why is this? Will other brands change to use higher impedance speakers or will Avantgarde remain the odd man out? Is it because these high sensitivity horn speakers are so often powered by low powered SET tube amps? This seems a plausible explanation until you consider that Avantgarde’s own amps are all solid state.

I’d be very interested to learn more about the significance of speaker impedance, especially as I’m about to change my old 8 ohm Duos for new 18 ohm ones. Thanks. Peter

 

[Elztalbiker]

18 ohms are easier to handle for the power amp stage. The result should be a better over all performance


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[mep]

When I first started dabbling with loudspeaker design and my own DIY efforts, virtually all hi-fi speakers were rated at 15 ohms.

Then rather rapidly the industry moved to 8 ohm speakers.

Why? Was it the transition from tube to solid state amplification that prompted this wholesale change in speaker design?

And why have a few brands more recently gone the other way?

Example - Avantgarde horn speakers. Avantgarde didn’t exist in the old 15-ohm days, but their Unos, Duos and Trios were all introduced in the late 1990s at the then standard 8 ohm nominal impedance. Then in about 2006, their new Omega range saw the drivers changed to nominal 18 ohms.


So much was claimed of these new drivers that many Duo owners parted with significant sums of hard-earned cash to change the drivers in their speakers to Omega ones - and everyone crowed over how huge the improvement was - perhaps they had to say that after spending so much. Let’s be generous and agree on this as a genuine and significant improvement in sound quality, but perhaps the new drivers were simply better irrespective of their new impedance. Avantgarde speakers remain at this 18 ohm impedance to this day.



Why is this? Will other brands change to use higher impedance speakers or will Avantgarde remain the odd man out? Is it because these high sensitivity horn speakers are so often powered by low powered SET tube amps? This seems a plausible explanation until you consider that Avantgarde’s own amps are all solid state.

I’d be very interested to learn more about the significance of speaker impedance, especially as I’m about to change my old 8 ohm Duos for new 18 ohm ones. Thanks. Peter

This a portion of something I wrote on AN:

Sometimes when I'm listening to great jazz music recorded in the early years of stereo (and I'm primarily talking about 1957-1959) and I'm marveling over the recording quality that was laid down using vacuum tube microphones, tape decks, and mixing consoles, I can't help but think a big portion of the magic was lost along the way on the road to audio "progress". In the old days of stereo gear, speakers tended to be large, high impedance, and high sensitivity. That's why older tube amps always had 16 ohm taps

When transistor amps elbowed their way to the audio table, they changed the way speakers were designed. We went from large, high sensitivity, high impedance speakers that were an easy load to drive.with low powered tube amps to something quite different. Think about the birth of acoustic suspension speakers from AR. Speakers suddenly were much smaller, with both lower impedance and sensitivity. They became much more wife friendly too because they were so much smaller than the giant ported box speakers.