Build a knockout retro Hifi for under £1k (Pt.2)!


We were pretty bowled over by the response to the original article, so thanks to everyone for checking it out and getting involved! There is clearly and quite rightly a lot of love for vintage Hifi.


If you missed it the first time round, you can find the blog here:

Where to next?

You may recall in the last article we had a look at the humble KEF 104aB:

KEF 104 5

Well in this piece I wanted to show you how you can bring this design bang up to date, and sounding better than ever!

KEF Museum

If you want to find out a bit more about this speaker, KEF have a fantastic ‘museum’ website, that has plenty of info on the KEF 104’s (and other KEF designs):


Where to buy

You can pick a mint pair up on Ebay for under £300, but if you don’t mind a fixer-upper, you can get a pair for far less. We picked up the pair in the title image, with stands and original paperwork for £175!

KEF 104 AB

What’s the difference between the standard and aB model?

The original KEF 104’s design was released in 1973 with production running to 1976. The 104aB (acoustic Butterworth) model ran from 1976 to 1980. The difference relates to the tweeter crossover and is explained in the article below:

Click to access Model_104aB_A_Story_of_Improvement.pdf

What if the drivers don’t work?

Fear not, ‘Retro Tech Audio’ stock used but working drive units:


The tweeter is a T27 (SP1032), the mid / bass driver a B200 (SP1039) and the Auxiliary Bass Radiator (ABR) a BD139 (SP1042).

Can I upgrade the drivers?

You definitely can*. The original B200 (SP1039) woofer can be replaced by a Monacor SPH-210, which you can pick up new for under £50 each.

*Credit goes to the very friendly and helpful Neil at Wilmslow Audio who, uses these units in their refurb service. More on this later.


This driver sims very well in the KEF 104 cabinet with the ABR:

KEF 104 REP1

The tweeter can be replaced by a Vifa D27TG (or Tymphany D27TG33-06), which costs about £25 each new. Reviews of this driver are excellent on Parts Express:–264-1022

Vifa D27TG

If you can stretch a little further, you could go for the fantastic Scan Speak D2905/950000.

Click to access d2905-950000.pdf


This unit is about £105 each here in the UK, but just look at the beautiful plot below:


In fact, we use this exact tweeter on our well reviewed SYSTEM-1 (below), which retails at £6.5k.



Capacitor performance can significantly degrade over time, so if you’ve got an original speaker from the 70’s, replacing the capacitors will likely significantly increase the sonic performance.

104 parts out

If you’re handy with a soldering iron, Falcon Acoustics will see you a kit for £30:

After the work, the crossovers will look like this:


But I just want someone to do the work for me?

No problem, just contact Neil at Wilmslow Audio and they’ll happily service and upgrade your KEF’s for a reasonable price:

I need some new grills?

The originals literally disintegrate, so it’s likely you’ll need a new pair. Again, Wilmslow Audio can provide a pair for £70:

One super duper crazy tweaked KEF104?!

This would require an adaptor plate and crossover mod, but the super high quality Scan Speak 18WU-8747T00 drive unit (shown below), sims perfectly in this cab, in combination with the original passive radiator.


Here is the plot:

KEF Plot

Then if you’re going to go this far, you may as well go full DSP active using one of our control boxes and some Hypex amplifier modules:


If this is something you might be interested in, send us an email for a quote.

Who we are

If you’ve not come across us before, we’re a small company called CODE Acoustics, making high end Hifi speakers in Woking, England.

My name is Ceri Thomas, and I’m the founder and Chief Designer:

me small


Hopefully this blog has given you a taste for taking an old classic, and breathing fresh life into it. Giving you that classic vintage look, with knockout sound quality!

Thanks for reading and if you’ve got any comments or suggestions, please just send me an email:

Ceri Thomas
Founder and Chief Designer
CODE Acoustics

One Reply to “Build a knockout retro Hifi for under £1k (Pt.2)!”

  1. Amazing and thank you. I just purchased some on ebay for £235 and one of the drivers is a bit on the crunchy side. On researching came across your info and am certainly tempted to go the full hog.
    Love these speakers!
    Thanks Ceri!


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