Blog Forums Consumer Electronics KEF Q60, vintage yeah !!

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    • #14566
      jay974
      Participant

      So, i stripped one of my old Q60s and i think it was worth it !

      1st some details about the Q60 :

      It’s coaxial design, bookshelf stand mounted size bass reflex 18 Liter.

      200mm LF driver, the KEF SP1280 MB200

      25mm HF driver KEF SP1276 NT25, both 4 Ohm but the unit is 8 Ohm.

      The Xover is a 3rd order for both sections with -6DB @ 45Hz

      I have to say the sound is very impressive for their size, it’s clear the stage is well set but it bothers me a little and I have to find out why………..

       

      I pulled out the drivers and stripped them, they were very clever to make them serviceable…..

       

      The tweeter is covered in dust, even with the grille on and needs some cleaning.

      I’ve read the ferrofluid can breakdown after a period of time but i dont have any availible on the island….

       

       

      The woofer has some rubbing marks on the coil’s inner part…..need some cleaning inside the magnet’s air gap i guess…

      After doing ll that i’ll run some measures with REW

       

    • #14567
      jay974
      Participant

      So here are the 1st mesures, did 3 of each for 1Mo and used their average.

      Big spikes à 1.7k and 12k, should be able to drop them with a notch filter iguess.

      Now i need to see the woofer !!

    • #14568
      jay974
      Participant

      Cleaning the air gap is a PITA , but it’s worth it spending on how much stuff you get out of there..

      And here it is all buffed and clean

      Centering the coil

      Center seems ok and i fitted the tweeter without the mesh.

       


       

      Now the curves, the impedence has 2 little bumps, the neighbour’s dog barking as i could hear it, but it does match the bumps on the sweep…….


       

      Next is to do a sweep of the other Q60 before i strip it to campare with this one after i put it back together.

      And then i’ll try to redesign it Xover included

       

    • #14569
      jay974
      Participant

       

      And this is the filter fitted in those speaker cabinets.

      I’ll have to redo the FRDs with a proper 2.828Vrms btw

    • #14572
      jay974
      Participant

      Stupid ass me connected either the tweeter or the woofer in reverse………..

      Instead of adding they substract at the Xover point.

      But ths is proper 1W @ 1M

       

      There is a huge 30db dip @ 176Hz, I guess this is what is bothering me and now my quest is to compensate for it by modding the filter as it does not show on the graph without the xover.

       

      This is with the correct polarity and has all the curves…..

       

    • #14573
      123toid
      Keymaster

      @jay974 

      First awesome job so far!  Don’t worry we have all connected the wires out of phase.  At least all of us that will actually admit it 😉 .  As far as the dip at 176hz.  There is something going on there.  If that is connected to the crossover, it appears it didn’t get connected correctly. There is no way to fix that with a crossover. It’s hard to say for sure what is going on, but something is definitely going on. Usually this is when something is grounded incorrectly. Of course, if you are reworking the crossover, it doesn’t really matter.  You will be taking measurements without the crossover in place anyway. 


    • #14576
      jay974
      Participant
      Posted by: @123toid

      @jay974 

      First awesome job so far!  Don’t worry we have all connected the wires out of phase.  At least all of us that will actually admit it 😉 .  As far as the dip at 176hz.  There is something going on there.  If that is connected to the crossover, it appears it didn’t get connected correctly. There is no way to fix that with a crossover. It’s hard to say for sure what is going on, but something is definitely going on. Usually this is when something is grounded incorrectly. Of course, if you are reworking the crossover, it doesn’t really matter.  You will be taking measurements without the crossover in place anyway. 

      Hi, upper in the thread i did some measurements w/o the xover and the dip is no where near what’s here. And i xchecked with the 2nd speaker and the dip is present as well.

    • #14577
      123toid
      Keymaster

      @jay974 

      Exactly. That is what I am saying.  It must be an issue with the crossover.  I would suspect a capacitor going to ground has gone bad.  You can check it pretty easy with Dats. Just hook up DATS to either side of the capacitor and run the capacitor check.  It’ll give you the value.  Just make sure your speaker isn’t connected to an amplifier.  Otherwise, you will damage your computer. 


    • #14578
      jay974
      Participant
      Posted by: @123toid

      @jay974 

      Exactly. That is what I am saying.  It must be an issue with the crossover.  I would suspect a capacitor going to ground has gone bad.  You can check it pretty easy with Dats. Just hook up DATS to either side of the capacitor and run the capacitor check.  It’ll give you the value.  Just make sure your speaker isn’t connected to an amplifier.  Otherwise, you will damage your computer. 

      I dont have a DATS, I use REW with some DIY setup and a UMC22 Behringer external studio soundcard. But I have a very precise and calibrated DVM and, somewhere in a carton box, an oscilloscope from the 90’s I salvaged from work (it was worth 25KUSD new).

      It’s creating a notch filter at around 175Hz and it’s the same failure on both speaker cabinets.

      Time to get the tools out and start digging I guess

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