Bookshelf speakers-double up,kef ls 50

I would like to ask,could I get increased performance,if I put one pair of book shelf speakers on top of another pair.My amp is powerful enough.Im using kef ls 50,and would consider getting another pair if things will shine.Thankyou
Well, they may play louder but, otherwise, it would be a mistake. Using two per channel will corrupt the excellent imaging of these speakers as the stacked pair will be very sensitive to vertical angle and vertical head position.

If you want louder and/or deeper, add a decent subwoofer.
Post removed 
Place them back to back and you'll get a bipole dispersion pattern. If you place them correctly you can achieve a very deep soundstage. A point source speaker like the KEF would be perfect for this type of experimentation.
Most amps will triple in power even! You could end up damaging your speakers or just playing way to much power thru them. 2 speakers connected to 1 AMP tap will make the amp see as much as 1-2 ohms! Most amps dont like this high resistance and will struggle or even shut down after a while.
speakers in parallel will only load an amp. as long as amp has capabilities to drive them both per channel, one can easily experiment.
when CORRECT math is done, either 2 speakers connected to 1 amp or 1 will have same current going through them if amp doubles the power to the halved load or less current if the case is different.
Post removed 
I'm running an old Aragon 2004 amp and running two pair of Silverline Minuets in parallel hasn't presented a problem for the amp.

From the perspective of sound quality, I can only say that it doesn't sound as good as using just a single pair of speakers. It's hard to articulate. The sound stage was still there, but it got less focused. Blurry, if that makes sense. I ran them with the top pair inverted.

I also ran them using only the mid bass driver on the top pair. I got a good bit of the focus back doing this, but still feel that a single pair sounded better.

I only tried it because I happened to have the speakers. I really don't think that buying another pair of speakers for this purpose would be a smart move.

As a practical matter, stacking two pairs of speakers essentially doubles the size of your speakers. If you have the room, perhaps just getting a larger pair of speakers would be the way to go.
I third Kal's comment.

As far as amplifier loading is concerned, here is the impedance curve for the LS50. It reaches a minimum of 4 ohms at 200 Hz, although at an undemanding phase angle, and also reaches 5.3 ohms at 135 Hz in combination with a current hungry phase angle of -41 degrees. Both of those frequencies, of course, are in areas that for a lot of music require lots of energy.

If the speakers are paralleled, the amplifier will therefore have to drive 2 ohms at 200 Hz, and 2.65 ohms at a severe phase angle at 135 Hz. Few amplifiers in the price range that is likely to be used with these speakers, or anywhere close to it, will sound their best working into loads like that. And as Matt indicated, some will even shut down after a while.

If the speakers are connected in series, the amplifier will see twice the impedance of a single speaker, which will avoid those loading problems. However the TOTAL amount of power the amplifier will be able to deliver to both speakers will be cut approximately in half, relative to what it could deliver into a single speaker. And each speaker will receive only 1/4 as much power as it would if it were the only speaker connected on that channel.

In either case, Matt is correct that the speakers could end up being damaged. Depending on volume level, either of those scenarios could result in the amplifier being driven into clipping, especially given the relatively low sensitivity of the speakers. Severely clipped waveforms tend to destroy tweeters, because the abrupt transitions of their waveforms between musical content and flat tops and bottoms correspond to much greater high frequency content than the original musical waveform may have contained.

Tony's observations make perfect sense. Unless the listening position is perfectly optimized vertically, AND unless the speakers are inverted relative to each other (as he was clever enough to do), a given note will have at least two equally loud arrival times at the listener's ears. That will result in comb filtering, which will tend to be perceived as a general loss of clarity. Exactly as Tony described.

As far as aiming the second speaker backwards is concerned, it might make for some interesting experiments but I suspect that there are likely to be more productive ways of investing the $ that the second set of speakers would cost.

-- Al
Brilliant,I'll go for the subwoofer option,then see how things go.Thankyou guys.
In a world where people claim major improvements from fuses, power cords, crystals and vibrating spheres the productivity of how one spends their audiophile dollars is highly subjective. As far as interesting experiments go, the Mirage M-series loudspeakers were a well received bipole design. Current bipole manufacturers include Audience and Definitive Tech.
Post removed 
Thanks,I should ask,Iam quite happy with these monitors,in a smallish room.Can you recommend a killer sub,I was thinking of the kef r400b.I plan on moving into a larger room very soon, to complete my system.
Post removed 
Hi Bob,Im running class A gear.Iam a novice to subwoofers.Ideally I would like more of the good stuff for a 2 channel set up.Can you recommend me something,thanks.Do you think I may need 2 to fill the room up with sound
Since you're moving to a larger room I'd consider dual subwoofers, maybe something like the SVS SB13 that is excellent and you can get a great deal if you buy two. Integrated properly I think that combination with your KEFs could potentially leave many a jaw dropping to the ground in disbelief. The key will be integrating the subs, which can be tricky and potentially expensive depending on how far you go with it. Best of luck and let us know how it goes. I'm thinking of doing something like this myself.
Oops. Sorry, I meant SVS SB12s that go for $1149 per pair. The SB13s are over twice the price. My bad.
Post removed 
Good Good,Yes I have 2 pre outs on my Ar ref 5 linestage,I prefer balanced.There seems to be some well reviewed subs around,but Ive never owned one with small speakers.Thankyou for your good suggestions.I'll get in there,and see how these ls50 sound, and go from there.My other speakers, Im yet to sell,take 2 people each to lift,so im down sizing you could say.
Hi there,I have just connected up another pair of book shelves.A pair of tannoy mx1,to the kefs, just to know.Im getting alot more weight,a fuller sound.Its good too,the amp is taking it,in its stride.This just mite do the trick,for now anyway.Thankyou for all suggestions.
The fewer the point source, the better the sound, that's the whole point of the LS50...

Go for a Rythmik F15HP subwoofer, you will be amazed how deep it goes.
Holographic imaging is fun, but it's only one aspect of sound reproduction, and it also limits your listening position to the sweet spot to get it.

Bipolar will take some of that sharpness away, but you gain benefits in power response and often in soundstage--bigger and deeper. You also get a stable stereo image throughout much of the room.

You also get more dynamic range and at least 3dB more in headroom, perhaps more because it increases room reinforcement. If a bipolar array interacts with the room well, IME it enhances the illusion of musicians in the room because the radiating pattern is a closer match to live music.

I think there are a lot more important performance parameters than pinpoint holographic imaging. Close your eyes at a live concert and you'll find that the imaging of live music is seldom that precise.
Hi ,I agree with all points of view.Just to throw something different around,Im back to 2 speakers.I swapped out my power cord on the cd player,Im getting some less transparency,but more warmth.More fullness,better bass and less brightness.So it looks like Im heading back to the subwoofer option to complete things.Im still learning after all these years,there is a good side,more of my cds I can listen to now.Im nearly there I like to think.I'll try another powercable,just to know and interconnect from the cd player.The kef is a good little speaker for the money.

You wrote, "The LS50 is a small speaker and should be high passed for it to shine."

I've been using a pair of KEF 102/2s with a Velodyne HGS-10 for years crossed at 80 Hz. I'm going to try a pair of KEF Reference 102s in place of the 102/2s. The 102s are rated at 65-20kHz +/- 2 dB, - 6 dB at 40 Hz. An Oppo 95 is connected directly via XLR to a Proceed Amp 2 that drives the KEFs. Does 80 Hz seem about right, or should I move the crossover up?

Hi there,someone else will have to help you on that one mate.Iam new to subwoofers.I didnt write that,cheers.