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Running 4 speakers from a 2-channel amp

I love the sound of 4 speakers playing at once around me. I've got a simple old SS amp, Luxman L507 (mid-1970's) that runs 4 speakers at once. I'm running a pair of Yamaha NS-1000x (6 Ohm) as mains, and a tweaked set of B&W 805Ns (8 Ohm) as B's.

I'm talking here about 2-channel sound, 4 speakers, not 4-channel surround sound.

I've been looking for a higher-end amp, but find almost all are two-channels only, with ports for only two speakers.

Some great old Luxman tube amps offer 4 channels, but only one pair at a time is available on the selector ("A or B," not "A and B"). One shop told me they could have one modified for me to be able to play 4 speakers, at only a small cost.

Another shop told me that playing 4 speakers at once, even on my current old Luxman, which has the "A and B" option, overburdens the amp and shortens it's life.

I wonder - can't we wire-up 4 speakers, say two on each side in parallel, like in so many car stereo setups?

Am I really limited to only 2 speakers with a 2-channel amp?
jimthewebguy

Showing 5 responses by hifitime

hifitime
715 posts
 
With those two speakers running paralleled,the combined resistance is about 3.4 ohms.That is hard for an amp to drive. 8+8 ohms =4ohms.4+4 = 2 ohms.8+6= 3.4286 ohms.
hifitime
715 posts
 
I found this on the net.One last thing,0 ohms is a direct short.LINK>>[http://www.1728.com/resistrs.htm]
hifitime
715 posts
 
Heat does shorten transistors life.Running two 8 ohm speakers is about the limits of most amps(4 ohms total).All the amps I've owned do parallel the speakers through the speaker switches.Some budget receivers run them in series,but that ruins the sound because both speakers would be using the others crossover along with its own.The 8+6 ohm speaker combo is over doing it in my opinion.The other peoples ideas sound better if you like the amp and want it keep on going.
hifitime
715 posts
 
Besides what Almarg mentioned about running speakers in series,the highs and mids will suffer too.The highs and mids will all be traveling through the other speakers low frequency choke and other parts of the crossover that otherwise would never,and was never meant to by the speakers designers.
hifitime
715 posts
 
Re;Series Hi Al,
In the 70' or 80's,a friend called me over upset about his stereo and asked me to come over,and I did.When I got there he showed me the new second pair of Infinity's(I believe)that he bought.He said he hooked them up together and must of blown something out.I told him I thought they were 4Ω ohm and his receiver couldn't drive two pairs most likely.The dealer told him it will work,and he had it playing at low volume when I arrived.He said the tweeters must have blown.I told him to turn the volume down and switch to one pair.When he did and turned it back up his eyes lit up.The highs were back.When switching both on you could here the volume drop.Right then I told him his receiver must be running them in series,and it sure enough was.On these crossover diagrams,figure 5 or 6 the highs that get though the choke coil are getting shorted out by C2 and C3 in these diagrams at least to my eyes.
Regards LINK>[http://www.termpro.com/articles/xover2.html]
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