Running 4 speakers from a 2-channel amp

Thank you Renjy651 for that last comment. I can't agree more.

I was very happy to learn that the L 505u can play A+B. People in a shop here said it couldn't. After reading your post I found it can from the Luxman site, and now I have a new possible amp goal in mind. I hope to find some way to listen to it at home.

Tonight I'll go and listen to a used pair of Sonus Faber Concertos (original type, not Homes) at a local shop. I'll be bringing my Luxman 507 and my own CD player (Ah! Njoe Tjoeb 96/24 w/Siemens 7308 gold pin tubes).

The intention is to have nice sounds in my computer room. I almost bought Adam 7 powered speakers, but was talked out of it. I have no idea yet whether the Sonus Fabers might match nicely with my Yamahas (totally opposite approches to sound reproduction, but sometimes such differences synergize), but if I buy these SFs I'll certainly experiment with that.

I love the sound of SF speakers, and I'm thinking it would be nice to have three very different-sounding pairs at home: My Yamaha NS100x's, modified B&W 805Ns, and Sonus fabers. This should cover the spectrum of my own tastes with differing types of music and recording quality.

Just an update in case anyone is interested
I listened to the Concertos and didn't like them much at all. The bass was weak and muffled, they didn't image well, lacked detail, and were very much "in the box." The had a lot of cosmetic damage as well. I compared them to some Quad 12L's, which were in mint condition and at half the price of the Concertos. Originally, i just wanted to use the Quads as a comparator, but I wound-up buying them as a temporary fix until I find something better. Since then I've come to like the Quads more and more, though best within a certain range of genres. I still think of them as temporaries, and I'm looking for some SF Minimas to try next.

In the meantime I bought the very first Japanese version (different mains power) iDecco in Japan, directly from the distributor before they reached the market here. This is an amazingly good unit. I'm using this mainly to listen to flac files streamed from my iMac to my Quads, and it sounds warm and extremely detailed.

I also picked-up a second set of NS-1000x's, a rare walnut set in the best condition I've ever seen these speakers in. I'm thinking of keeping this set for replacement parts, so that I'll always have NS-1000x's in good shape around. The full set here in Japan costs about as much as two used so-so conditioned beryllium tweeters do overseas.

AL - I would never connect speakers in series but I believe DF doesn't suffer - at least with woofers in series within the same box. It appears that each woofer sees impedance of the other woofer in series (JBL wrote paper on that - that is incorrect) but in reality EMFs are in opposite phase and cancel. If amp's output impedance is zero - it looks like two woofers are connected in parallel in opposite polarities (EMFs cancel). Connecting woofers in series makes sense only when they are identical (for cancellation). Connecting speakers boxes in series will be a mess.

More info here: http://www.cartchunk.org/audiotopics/SeriesSpeaker.pdf

or here: http://www.monstercable.com/mpc/stable/tech/A2538_Wiring_Woofers.pdf

Jim -- Thanks for the update. Enjoy!

Kijanki -- That's an interesting thought, which I hadn't previously seen stated.

A series connection, whether of two woofers within an enclosure, or of two series connected speakers, would have to be done such that the plus (or red) terminal of one woofer or speaker is connected to the minus (or black) terminal of the other woofer (or speaker). Otherwise the two drivers would operate out of phase and cancel acoustically.

Given that arrangement, the voltages corresponding to the back-emf of each driver would add together, resulting in double the voltage assuming the drivers are identical. And the papers you referenced appear to say that the doubled voltage compensates for the doubled total impedance, resulting in the same current and hence the same dissipation of energy from each woofer (or speaker) that would occur with a single woofer (or speaker) connected to the same amplifier.

That seems to make sense. Thanks!

In any event, we (you, me, Rodman, HifiTime) are all in agreement that for other reasons series connection of speakers, especially if they are not identical, is a no-no.

Best regards,
-- Al

Thanks Kijanki . . . A good explanitation of why it can be appropriate to wire speakers in series under certain circumstances. It should be noted the main assumptions/limitations . .

First, it makes the loudspeaker performance more variable with manufacturing tolerances, so in i.e. the D'Appolito array mentioned the effective tolerance for the drivers themselves must be better than for the parallel connection to get the same average results. And for a professional sound reinforcement application, there's one-quarter the statistical redundancy in the event of driver damage.

Second, it assumes that the driving source (amplifier) have essentially a zero output impedance. Although one wouldn't expect to see an SET or OTL amp for this kind of application, series volume controls should definitely be avoided, especially because they introduce enough frequency-response variations of their own.

So for something like putting four pairs of identical outdoor speakers on a single receiver ... The series/parallel scheme works great, provided they're hooked directly to the (typical solid-state) amplifier.