Infinity · Floorstander · Late 1970s
The Qb belongs to Infinity's Quantum series of the late 1970s, the line that arrived alongside the first EMIT planar tweeters. Listings date it to 1977, call it a three-way and say it has an EMIT, and that's as far as the evidence we could find goes, so treat everything else in a listing as a claim to check. Some Quantum models of the period were made in Germany, including the Quantum 3 and Q Junior, so don't assume a Qb was built in the US. One listing described its cabinet as walnut-look, which suggests a wood-grain wrap rather than real veneer. If you want a late-70s speaker with an EMIT, it's one of the ways in. Ask for the label, photos of every driver and a video of the pair playing before you commit.
With the grille off
Ask for a photo of every driver with the grilles off, on both speakers. They should match each other and this list.
Sources on the Qb are thin, so the seller's photos matter more than usual. Make sure the EMIT tweeter plays on both speakers, and look closely at the cabinet edges.
New to old speakers? How to check a used pair walks through every driver, the crossover and the cabinet.
We haven’t been through this model’s listings yet. Search eBay and run every listing through the checklist above. Ask for photos of both speakers with the grilles off and the serial labels on the back, and pass on any seller who won’t send them.
Search “Infinity Qb” on eBay ↗eBay searchInfinity · 2-way
BookshelfSpecs and what to check →
Infinity · 3-way
FloorstanderSpecs and what to check →
Infinity · 3-way
FloorstanderSpecs and what to check →
Infinity · 4-way
FloorstanderSpecs and what to check →