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Stacked Quads wiring question

I am about to finally have a set of stacked Quad speakers. The gentleman I am buying them from says they are wired in series. I'm confused about this, as I *assumed* that they had to be wired in parallel. After some research on the Internet I discovered that there are three ways to wire stacked Quad 57 speakers. Series, Parallel, and one amplifier per speaker (ie: four mono blocks or two stereo amps). Putting the last option aside for now, can someone explain how you can wire a set of speakers in series? I know a little about electricity, and know enough about Ohms law to know the effect on resistance when wiring two resistors in series (add the resistance up) vs: wiring two resistors in parallel (final resistance is half the value of one of the resistors assuming both the same value). I realize speakers deal with variable resistance, or impedance as the resistive load to the amplifier changes with frequency. I also have heard that electrostatic speakers have a more capacitive load then traditional speakers. That being said, I still don't see how you can wire two Quads in series. Aren't you going through the crossover network on the first speaker which would adversely effect the second speaker wired in series? I'm really confused about this issue and was hoping someone could explain this to me.

I do know that in parallel, you will have a much lower impedance presented to the amplifier, thus driving it harder then if it's wired in series in which case it presents a higher impedance to said amplifier. This alone might make it more desirable to wire stacked speakers in series, but the crossover thing has me wonky!!

Mark
markcooperstein
bdp24's avatar
bdp24
9,788 posts
 

Your confusion appears to be arising from the thought that, should the second set of Quads receive their signal off the speaker terminals of the first pair (as is the case in series wiring), they will see a signal filtered from the x/o in that first pair; they won't. The signal is just passed along from the first pair to the second, unfiltered. It's just that simple!

However, whereas a pair wired in parallel will have their combined impedance cut in half, in series that impedance will be doubled. Neither is optimum, with a trade-off in each case (minimum vs. maximum impedance). The best way to run stacked Quads is with a separate amp channel for each speaker---either two stereo amps, or four mono. A pair of Music Reference RM-10 Mk.2, Atma-Sphere S-30, or Pass X25 would be great.

tomic601's avatar
tomic601
12,911 posts
 
i ran mine...long, long ago with 2 x Conrad Johnson MV-45a
easy and neat....
markcooperstein OP
12 posts
 
Thanks for the explanation. Ok, I hadn't considered powering them separately, but I could do this if there would be any advantage. Here's what I originally thought I'd do: power them with a pair of 125 watt tube amplifiers. I built two Bob Latino VTA M-125 amplifiers. But, I also have two Quad 303 stereo amplifiers that I could use as well. My question is, how do you split the signal coming from the preamplifier to feed two stereo amplifiers? Surely you don't just use a "Y" cable connector, isn't there a different way to do this? 

Mark
roberjerman
4,319 posts
 
I have two pairs of the 57's. Not yet setup for stacked. Will go for parallel with a single SS stereo amp (BEL 1001). This will halve the impedance around 50hz (30ohms) and allow more power for bass. SS power drops into higher impedances.
roberjerman
4,319 posts
 
Use a Y connector from your preamp (if it doesn't have two pairs of output jacks). No sonic harm for your two 303's! That's a good combination for use with two pairs of 57's!
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