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KEFKIT 3 or 104ab?

Discussion in 'classic' started by F456gtm, Sep 14, 2019.

  1. F456gtm

    F456gtm pfm Member


    I would like to build a pair of loudspeakers, I am retired and bored to death.

    I have been thinking of using Falcon Acoustics drivers, B139, B110 and T27 with Falcon crossovers. I have a chance to purchase a new KEFKIT 3 - baffles and hardware - for just a few quid but I also can build a pair of 104ab, the drivers are the same. The KK3 uses the B139 vertically and in a ported box whereas the 104ab uses the B139 horizontally and in a sealed box. I am not sure which one would sound more musical.

    Any opinions?


  2. Mike P

    Mike P pfm Member

    If you like deep and effortless bass, how about a transmission line design?
  3. clive7164

    clive7164 pfm Member

    The B139 on the 104ab is a passive unit so not sure if the active ones from
    Falcon would be suitable without some serious reworking
    Clive Smith
  4. ToTo Man

    ToTo Man the band not the dog

    Based on the three different pairs of KEF Concertos I have owned during the years, I think building a pair using the new Falcon units would be a waste of money. The cabinet design and original DN12 crossover do not get the best from these drivers and results in a coloured sound, particularly across the mid-band. Bass extension (35Hz @ -3dB) is very respectable given the smallish 62L cabinet, but the quality and effortlessness of the bass is completely outclassed by a transmission line such as the IMF TLS 80 or even the smaller TLS 50. A better use of the Falcon units may perhaps be to build an LS3/5A with their T27 and B110 units and a separate pair of transmission lines with their B139 units. This would provide much greater flexibility but would of course add complexity to the system in the form of additional crossovers.
  5. ToTo Man

    ToTo Man the band not the dog

    That's correct, the 104 used an active B139 while the 104ab used a motorless B139 as an auxiliary bass radiator, which is presumably where the 'ab' in 140ab originates.
  6. JemHayward

    JemHayward pfm Member

    Unless you have actually heard the 104ab and liked it, I'd not take the risk. It was based on sound theories, but I always felt that no one had actually listened to them before they were launched - I suspect the measured really well. Sort of the wort combination of 1970s speakers, the extension of a sealed box speaker with the flabby bass from a ported enclosure - the 'B139' is a passive radiator and I doubt an active B139 would behave in the same way.

    The Concerto (KK3) was well regarded, but had a very 'dated' sound. Building a pair with new drivers would be an expensive way of getting a speaker you could possibly buy at a car boot for a fiver.

    Building some speakers is a great way to spend your time, but I'd aim for something a bit more modern, and I'd go active with a digital / DSP crossover. I built some LS3/5a sized speakers with Monacor drivers and a miniDSP crossover, and B&O icepower amps for my kitchen, and they are astonishing - way better than I remember my genuine Rogers LS3/5as that I had in the late 70's being.
  7. Martyn Miles

    Martyn Miles pfm Member

    I am retired and not bored to death, as I repair and build speakers.
    Mainly LS3/5as.

    As for your question re. Kefkit 3 or 104, personally I would go for the 104.
  8. 57charles

    57charles pfm Member

    Both the KEF 104 and 104ab use the b139 'motorless' - the 'ab' stands for 'acoustic butterworth' referring to the crossover - nothing to do with 'auxiliary bass radiator'.
    peterm and ToTo Man like this.
  9. ToTo Man

    ToTo Man the band not the dog

    I learn something new every day!
  10. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    FWIW I always found the 104ab a pretty impressive speaker.
  11. Stunsworth

    Stunsworth pfm Member

    The ‘AB’ refers to the crossover - Acoustic Butterworth if I remember correctly - and differentiates them from the original 104.

    Along with the 105 they impressed me a lot, but I haven’t heard a pair in decades.

    Edit: I see 57Charles beat me to it.
  12. Martyn Miles

    Martyn Miles pfm Member

    I owned a pair of 104s for a while and really liked them.
    They went because I could afford a pair of BC1s.
  13. VanDerGraaf

    VanDerGraaf Member

    The 104 particularly in AB form is a beautiful sounding speaker. I have had one pair of each. I wouldn't hesitate to go ahead with your 104 plan.
  14. foxwelljsly

    foxwelljsly Keep Music Vile

    I certainly wouldn't build a pair of concertos/kefkit 3 from scratch - they're cheap secondhand and with a new crossover, tweeter and some cabinet tidying they can be pretty good - especially with period valve power amps. There are probably better ways of spending your time and money, though.
  15. cooky1257

    cooky1257 pfm Member

    Buy the KK3 and find a pair of Concertos for a fiver at a car boot sale(!) and use the drivers to build some active/dsp Isobariks.
  16. Martyn Miles

    Martyn Miles pfm Member

    All very well, but not everyone likes Isobariks...
    narabdela likes this.
  17. ToTo Man

    ToTo Man the band not the dog

    I'd like to know where all these £5 KEF Concertos are so that I can make a living parting them out! Oh, wait... that's what folk have been doing for the last 15 years...

    On a serious note, good luck finding a pair for a fiver. The cheapest I ever managed was £50.

    Perplexingly, some eBay Completed Listings show Concertos have recently sold for as much as £500, - this surely has to be a mistake?!
    cooky1257 likes this.
  18. VanDerGraaf

    VanDerGraaf Member

    I concur- the days of the £50 pair of Concertos or 104s is over. There may be the odd exception to this but as a rule of thumb, the time has gone.
    As with many other hobbies and interests, speculators have sent prices for vintage speakers spiralling. Some old Kef seem to be going for double what they did 18 months ago.

    Some might say, not before time. These things have been inherently undervalued in recent years.

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