LS-50 Speakers (Passive)

I have a pair of UB5s, as well as a pair of ~1978 Chartwell LS3/5As. I should compare them some time.

40 year old caps are probably suspect

crossover to my sub naturally at the point where the mains can't no longer output, and keep the use of the sub to a minimum.

crossing over an octave above the main 'lower' frequency @ 6db / octave with a passive XOver and setting sub[s] to 18db / octave and 180° with the sub[s] in the main plane yields better results than trying to get bottom out of a small driver / box. The phase is correct, the mains are not stressed and less power is required for the mains. Main and sub should be same type, i.e. sealed or vented.

C = 1 / ( 2 * π * f * R ) where f is desired frequency, R is amplifier input in Ω.
C is in farads, so multiply by 10^12 FOR pF

I have a pair of UB5s, as well as a pair of ~1978 Chartwell LS3/5As. I should compare them some time.

40 year old caps are probably suspect

Original LS3/5As can be worth $1,500 to $2,500 a pair. Modified ones ain’t worth sh*t :-)

The LS50s (recently manufactured examples) can compete with many ~$5K speakers IME. However, getting them to do that requires a high quality amp and source. If you pair them with a budget amp, say something in the <$1k range, as one likely would with $1500 speakers, you won’t realize their full potential, especially concerning their bass. This is why some find budget speakers like the Elacs to be nearly as good. It’s because they have system bottlenecks elsewhere.

It’s better to think of the passive LS50s as a $3500 speakers, because they simply require high quality gear. I run a pair with a budget amp in a third system. They sound ok for that application, but having had them paired with $2.5K amps in my other rooms, I know they’re capable of far greater performance. I wouldn’t read too much into comparisons with lower KEF models. Stereophile recently rated the Q350s as "class C" speakers while the LS50s remain "class A." I’ve owned and auditioned a fair number of their class C rated soeakers. The LS50s are in a whole different ballpark when properly powered. The wireless version is a better value proposition unless you already own a high performance amp.

Completely agree with Helomech above. I run my LS50’s with $3700 SimAudio amp and pre plus $2k DAC. BASS is clean, taught and well controlled. Room is 10’ x 14’ x 8.5’. Go for it!

As a Kef dealer agree with Helomech and Tom6897, we are also an Elac dealer, The Unifi do not have the resoloution of the KEFs, and are voiced to be a bit on the warm side. 

The Kef LS 50 are cleaner, with much  more sound stage focus. 

We just took on the Quad Line the S2 monitor at $1,000.00 a pair are scary good, and in some ways out performs the LS 50 while having much better low bass, and even greater treble clarity and a very wide soundstage. 

Please PM us if we can be of further assistance.

Dave and Troy
Audio Doctor NJ