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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
rodman99999
6,170 posts
 
re: Series connection- Anytime components are added to a signal path, the signal is degraded. Introducing the reactance(and Back EMF) of the drivers of the systems to the signal path WILL CERTAINLY cause distortions. Whether they bother the listener or not will depend on how discerning they are. Further- raising the impedance that the output of a typical solid state amp sees, above 8 Ohms, can cut it's power significantly.
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]
rodman99999
6,170 posts
 
Hello Mr H- The highs that pass through the inductor of a second, third or higher order filter, will be selectively shunted to ground via a cap, to increase the roll off to the woofer(and midrange, if applicable). The highs will be passed through the tweeter section of the crossover however, and still continue to the next system in the series. Of course, much of the energy in that frequency range will have been expended, in reproducing the highs/creating heat in that first system. Depending on the complexity, efficiency and reactance of the first system in a series circuit, there exists a large possibility/likelihood for seriously degraded sound, as your friend learned.
almarg's avatar
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almarg
9,670 posts
 
Hmm, actually HifiTime's statement about highs passing through the woofer crossover is more correct than I initially thought.

If speaker A is series connected to speaker B, the high frequency energy that manages to get through the inductor that is in series with the woofer of speaker A will not be shunted to ground via a cap, it will be shunted to speaker B through the cap. Where some fraction of that shunted signal will be reproduced in its full glory by the mid or high frequency driver of speaker B, complete with whatever distortions, phase effects, etc., were imposed on it by that inductor and capacitor in the woofer section of speaker A.

Figure 5 of the article HifiTime linked to in his previous post is helpful in visualizing this.

In any event, all three of us are in agreement on the bottom line -- for any of several reasons series connection is not a recipe for quality sound.

Regards,
-- Al
jimthewebguy OP
44 posts
 
Thanks all you ppl for this insightful thread. I had initially thought it a simpler question...
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