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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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In Reply to: A and B speaker use. posted by DRam on October 27, 2015 at 14:19:12:
Quality vintage receivers built in the 1970s and earlier generally had robust transformers and other parts. They were designed to run comfortably at 4-ohms with higher power output than at 8-ohms. A B speaker switches were wired in parallel, which meant that the receiver was seeing a 4-ohm load when both pair of speakers were running. A basic measure of the quality of a receiver was by how much more the power was with a 4-ohm than with an 8-ohm load. The only caution was with these receivers it was important to select speaker pairs that were not individually 4 ohms or even a shy 8 ohms (such as many EPI of the period which were nominally 8 ohms but in reality closer to 6 ohms). I once watched two pair of EPIs "smoke" a Sansui receiver and an EPI woofer while running both pair at once.
Beginning in the 1980s, receivers got cheaper and the quality of the cheaper parts deteriorated and became less robust, particularly under 4-ohm loads. Many owners' manuals told the owner not to run anything other than 8-ohm speakers. But, customers still wanted to be able to run two pair of speakers, so the manufacturers wired the AB switches in series. When two pair of 8-ohm speakers are running the load seen by the receiver is 16 ohms.
Most modern receivers sound rather awful feeding a 16-ohm load. Power output is less, but there are often other issues related to basic sound quality too.
You need to run an experiment to see if your Denon AB switch is wired in parallel or series. Denon is quality equipment, but I have no idea when it was built.
Connect a single pair of 8-ohm speakers to the A side and set the switch to just A speakers to check and see that everything is connected. Now press both the A and B buttons (or the A+B setting if you have a dial). If the speakers connected to the A side continue to play, your switches are connected in parallel. If there is no longer any sound the wiring is in series.
Series speaker wiring works just like series Christmas tree bulbs!
The series wiring works to run two pairs at once, but I doubt you will be happy with the sound with both pairs running.
David
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Follow Ups
- RE: A and B speaker use. - DavidLD 15:53:58 10/27/15 (0)
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