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KEF transmission line project


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  • 3 weeks later...

One Radford xo is ready & once I'm happy with it I will fix all components to the board. I have given a side by side test against a recapped KEF DN12 and it sounds much clearer but may have to adjust the midrange attenuator. More listening is needed tomorrow.

 

 

 

 

IMAG0377.jpg

Edited by Sansui77
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Update.

Who ever made these back in 1975 they had stuffed the internal cavity with so much insulation that it became like a seal box :emot-bang:

I have taken all that crap out and re-aligned it correctly. We now have bass :lol:

 

Crossovers;

After building 5 different version of crossovers, I have decided which version I will be making for my father's transmission line speakers. The Radford FN10 xo was tested with and without the notch filter for the B110 but there was no difference. I found the Radford xo's mid - top end too laid back and the T27 lacking detail. I also tried to adjust the series attenuators to bring the sound more forward but with no luck. Comparing the Radford FN10 & the KEF DN12, the Radford sounded much cleaner even at high volume. The KEF DN12 at high volume just became harsh and unlistenable, really bad. 

 

My new design has improved the mid - top end detail which I've added a Coles 4001 super tweeter for a more airy top end. The below XO design may change over in coming weeks.

 

 

 

 

 

Improved XO with Coles super tweeter1.jpg

Edited by Sansui77
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After a few xo changes, I have finally decided which version I like the best. I have installed them with new wiring and new rear terminal posts. When I completed the first box, I compared it with the original Kef DN12. The difference is huge. The DN12 sounded dull. The top end was really bad, cymbals sounded dull and missing detail that you know because you have studied that particular song before. No definition or detail coming through the T27. I'm a little shocked at how they sound now with the upgraded xo. There were a heaps of smiles listening to them yesterday as I could not believe how nice they sounded. The upper mid - top end has that Spendor BC1 feel to it, very accurate detail but with heaps more power (sorry neighbors) and the sound stage is just huge. The xo was very easy to drive. Not power hungry at all. I was running a Sansui AU-517 with a DAC between 9 - 10 o'clock on Vol and the sui was just warm.

 

I've used np electrolytics for the first feed though, 60uF (B139) and 30uF for the B110 and the rest using good polypropylene caps for the B110, T27 & Coles sections. LP inductor I used is a super q steel laminated type and the rest are all 16gauge aircore. Amazing difference in sound quality when you use nice components.

 

Next is to add the Coles 4001g 16ohm super tweeter, restore the cabinet veneer and replace the green with gold speck speaker cloth with something a little better colour than lime green. These will be heading back to their original home soon.

 

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  • 4 weeks later...


45 minutes ago, Sansui77 said:

No. Brought these locally cheap. They sounded very average but now after my mods, do they sing and shake the floor.

 

When are you going to sell me a pair? :D.

 

How does the modded pair above compare to a pair of say, TL80's.

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15 hours ago, kelossus said:

 

When are you going to sell me a pair? :D.

 

How does the modded pair above compare to a pair of say, TL80's.

Hard to say @kelossus but mine sound bloody good for what I got them for and what investment I have in them which is not much. The 80's will go down a little bit lower than the Baily's because it has a newer more efficient designed TL. If you want to go down the TLS80 path, get the mk II's as this had the newer driver and they came with stands. if you have a smaller room than 6 x 4M, look at the TLS50's.

Edited by Sansui77
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  • 10 months later...


On ‎29‎/‎11‎/‎2017 at 9:34 AM, Sansui77 said:

Comparing the Radford FN10 & the KEF DN12, the Radford sounded much cleaner even at high volume. The KEF DN12 at high volume just became harsh and unlistenable, really bad. 

IMHO there are two three things wrong with the original KEF DN12 crossover.  

  • First the use of electrolytic capacitors.  Whilst a bipolar is probably an acceptable trade off of capacitance vs space vs cost for the LF path, the use of metalized polys in the MF and HF circuits is pretty well a must IME.
     
  • Secondly, the T27 tweeters were prone to an early trip to heaven if the units were driven hard.  The HF path benefits from a much sharper high pass filter of say 18 or 24dB/octave.  A suitable poly switch works too as long as it is installed in the input to the high pass filter.
     
  • And last but certainly not the least important is replacing those crappy ferrite cored inductors with air-cored types.  One of the causes of distortion was the ferrite cored inductors would saturate at high power levels. 

Anyhow, it's good to see these KEF drivers put to good use in these TL designs.  :)

 

Cheers,

Alan R.

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On 25/11/2018 at 1:09 AM, koozoop said:

It's been a long time but I managed to finish the boxes just last week. Some minor touches missing and then I will install the drivers.

 

 

IMG_20181121_205814.jpg

IMG_20181121_212031.jpg

Very interesting. You making a set of Ls3/5a to go with the Bailey's?

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No, it's a pure 3-way to work with the FN-10 cross. I had these sitting around from a CS1 pair so i decided to use as a separated mid-high enclosure. I plan to place them besides the TL boxes at tweeter ear height. Of course I will make some room and other tests to find the best position. There will be cross modifications as well.

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  • 5 years later...
On 06/01/2018 at 1:17 PM, Sansui77 said:

Another project finished.

I have added the Coles super tweeters and redone the grill cloth. Tested them and they sound fantastic.



f4eafc14fbdc278e0a1d6bf145d66cfa.jpg21351097dcd2c6f72eaaf0af7c4bc7ff.jpg

 

And they still sound great 🙂

 

regards Bruce

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13 hours ago, sloper said:

Yes and l will not part with them.

 

regards Bruce

I must have done a good job on the upgrades. Enjoy.

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