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

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Active Member
Feb 14, 2020
Portsmouth, UK
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, but let’s be generous and agree on this as a significant improvement in sound quality.

Perhaps the new drivers were simply better irrespective of their new impedance, but 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
Likes: jeffrey_t


Well-Known Member
Dec 12, 2013
High impedance drivers were really there to suit tooby amps , OTL ‘s loves them for eg. lower impedance drivers were really better suited for high current driven SS amps, Drivers for the amps of the day for sure ...


Well-Known Member
Aug 25, 2010
I don't think there are any obvious differences between say 4-8 or 16 ohm drivers. There are drivers available with multiple impedance options. If you want to parallel up drivers you would go with 16's. If you wanted to squeeze as much power as you can from an amp for sub-woofer duty 4 would be the best option. Depends on what you are doing.

Rob :)

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