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Thread: Renovation of Celestion 66 Studio Monitors

  1. #21
    Join Date: Jan 2009

    Location: Sheffield - UK

    Posts: 5,461
    I'm Mark.

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    When I looked at coil interaction I found that it was quite easy to alter the mH rating by altering the distance and relationship between coils. If you have a spare coil and an LCR meter it is easy to see the changes happening in real time.

    I would also add that reducing the DCR of coils will have as much, if not more, impact on the crossover than the ESR of newer caps - I would urge caution in this area.

    100% Analogue

  2. #22
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,166
    I'm Ken.

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    YNWaN - Its because the coils have too high a dcR that lower values are sought. After looking at response curves this is what was thought to be part of the soloution. There is a lot of work going on at diyaudio for 66's, they are even modifying the circuit to allow for ageing drivers and inbalance in drivers between stereo pairs.

    In terms of altering coil values by proximity (interaction), again it was muted that if normally "better" positions were used this may alter the interaction which surely must be taking place. This may have been allowed for in the circuit design. Its all quess work unless you do some experimenting with the actual coils to see if less interaction results in better or worse sound with the other component values unchanged.

    66's are rated quite highly by many people so the circuit must be pretty good as is.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + Denon DL-301 mkII / Pro-Ject Phono box & Pre Box RS / KMTech Active X-Over / Nakamichi AVP1 Power / Yamaha NS1000M / Stello CDT100 Transport / DAC Magic.

  3. #23
    Join Date: Jan 2009

    Location: Sheffield - UK

    Posts: 5,461
    I'm Mark.

    Default Renovation of Celestion 66 Studio Monitors

    Hmm... So whilst Celestion may have had a cunning new interpretation of inductor interaction but they had significantly less understanding of inductor resistance - I suppose it's possible but seems unlikely to me. After all, you only have to increase the gauge of the wire used to lower the resistance of a coil (hardly a new concept) and I've never heard of a speaker manufacturer relying on coil interaction to alter values when it is easy enough to specify the actual value wanted. Anyway, irrespective, I'm sure you will have fun and make a nice job of your project.
    Last edited by YNWaN; 23-04-2014 at 17:00.

    100% Analogue

  4. #24
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,166
    I'm Ken.

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    "So whilst Celestion may have had a cunning new interpretation of inductor interaction but they had significantly less understanding of inductor resistance"

    It's only a theory put forward, remember, most designs are not based on what is best or should be done but by what is affordable and we are allowed to do. The argument was that the size of the board and type of inductors may have been dictated by cost so the engineers may have had to work with the unwanted interaction best they could, low dcR air core inductors usually cost more, a lot more.

    Like I say just a theory put out there, it could be total rubbish and moving the coils appart and reorienting them might have significant benefits. In theory it should, so long as there were no tweeks elsewhere to compensate for their close proximity and that really was the point being made.

    With every change you make it's a gamble till you have the results, most of us can't afford to have too many go the wrong way so err on the cautious side.

    I'm still gathering info and am firmly on the fence with some of this stuff so intrested in all points of view.

    The first running of my speakers will have the std x-overs that came with them, I will be gentle with them and not turn the volume to eleven till I can create a new pair of x-over with fresh parts.

    My replacement Tweeters are on route from the States, all my projects are on hold waiting for bits at the moment.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + Denon DL-301 mkII / Pro-Ject Phono box & Pre Box RS / KMTech Active X-Over / Nakamichi AVP1 Power / Yamaha NS1000M / Stello CDT100 Transport / DAC Magic.

  5. #25
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,166
    I'm Ken.

    Default Update

    Marco - When you come to replace the two 72uf electrolytic caps in the bass section of the x-over you will find that it is a difficult value to find.

    In my photo these are the two caps on the right, one above each of the big coils.

    No one seems to make a 72uf Polyprop film cap and if they did it would be huge/pricey.

    If you try and make it from x2 at 36uf again this is not a standard value, the only options seem to be Solen PB or Axon True Cap. Both are made by SCR in the same factory in France and are at the budget end of the Polyprop caps, but would still be a big improvement on the Lytics.

    They are about $7 each for the Axon and $20 for the Solen (USD) you will need eight in total for the two boards. Humblehomemadehifi in the cap tests rated the Axon very marginally better, "more clarity". They are both +/- 5% but at humble he recond that Axon are closer to the nominal value - May have been batch variation on the samples he had.

    These caps are a lot bigger than the originals and you need two to make up the value, they will not fitt the space on the board, another reason to make a new one.

    I wouldn't recomend using caps of unequal value to make up the 72uf, there was a technical explanation for this on diyaudio, something about different foil lengths giving different times for the signal to pass through, combined = smeared sound, which kind of has some logic to it from my none expert viewpoint. The problem I find with the technical arguments is you can never get two techy people to agree on anything. One option proposed was to use single caps and make the one nearest the input 75uf and the other to 68uf (more easily available). people who had done this had reported good results and the tolerance on a 72 total (if 10%) was raised as an argument. I personally will be using two identical 36uf caps, measuring them and pairing from the total of eight needed to get the closest combined values.

    I will also be replacing the thin interconnect wire used internally. Thought about this and considered 12awg/Teflon, then I came accross the Black Rhodium "Twist" speaker cable with Silicone prime insulation and no jacket. Its 3.50/m at mainscables R us and they have some with smeared lettering with 25% discount. The Silicon will help dampen vibration when used in the cabinet so seems made for the job.
    It was reasonably well recieved as a main speaker cable and I know REXTON had very good things to say about it when he tried it as a main cable from the amp. So that seems to have sorted that one.

    Pondering what make of caps to use for the other values re Price/performance. Sonicap GenI have been one of my long time favourites and seem to be used a lot in the 66 recaps. They didn't work well on my Tannoy Cheviots though and to my ears ClarityCap ESA were a much better match for that combination of driver/circuit and at a reasonable price.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + Denon DL-301 mkII / Pro-Ject Phono box & Pre Box RS / KMTech Active X-Over / Nakamichi AVP1 Power / Yamaha NS1000M / Stello CDT100 Transport / DAC Magic.

  6. #26
    Join Date: Dec 2011

    Location: South downs

    Posts: 3,482
    I'm James.

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    Go the whole hog and take them active

  7. #27
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,166
    I'm Ken.

    Default Update

    istari knight - Don't tempt me.





    The replacement Bass drivers have been completed and are ready to fit.
    I cleaned the alloy with some "T-Cut" colour restorer on a plastic scouring pad, the green bit, I pulled it off the yellow foam part, it was polished off with a soft cloth.

    I prefer the Black drivers to the natural, the colour is in the coating that was sprayed or brushed on by Celestion, its quite thick and rubbery, a bit like evo-stick contact cement when it has fully set. I didn't want to add any material and weight as the Bass unit contributes to the lower Mid Range and any additional coating would very probably ruin the output, so paint of any kind was out of the question. I decided to Dye the existing coating and did a test on the old driver to check for compatibility. I did this using two giant felt tip markers, the old permanent type of xylene marker that is Jet Black, none of this eco friendly Blue Black stuff that looks pants when you catch it in the light. I used the big 12mm chisel tip and quickly covered the cone. When the marker had dried, which only took a minute, I went over it with a lint free cloth moistened with some Isopropanol, this blends in any lines in the colour and gives a uniform finish. When the Iso had evaporated off I then applied a little Black Trim Wax to the cone and the rubber surround which was buffed off with a clean cloth. This gives a slight sheen to the finish and a little UV protection to the Marker colour. Again this adds nothing which will affect the acoustics. I did them one at a time and compared the sound of the cone between the one that was completed and the untouched one. When I scraped or tapped the cones they sounded the same so mission accomplished. The old driver in the background has had some after market treatment applied which is about 0.5mm thick and has made the dust cap solid, this will have added a lot of weight and I think the sound would have suffered. It was fashionable at one time to paint these products on to paper cones, luckily the samples I found were original and only had Celestions treatment applied.
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + Denon DL-301 mkII / Pro-Ject Phono box & Pre Box RS / KMTech Active X-Over / Nakamichi AVP1 Power / Yamaha NS1000M / Stello CDT100 Transport / DAC Magic.

  8. #28
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,166
    I'm Ken.

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    Apologies for the loss of pictures on all my postings.

    My web hosting site is changing servers and I am having teething problems.

    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + Denon DL-301 mkII / Pro-Ject Phono box & Pre Box RS / KMTech Active X-Over / Nakamichi AVP1 Power / Yamaha NS1000M / Stello CDT100 Transport / DAC Magic.

  9. #29
    Join Date: Nov 2013

    Location: Yorkshire

    Posts: 4,271
    I'm Andr'e.

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    Quote Originally Posted by Qwin View Post
    Marco - When you come to replace the two 72uf electrolytic caps in the bass section of the x-over you will find that it is a difficult value to find.
    Ansar do 75uF These are 5% which will do.

  10. #30
    Join Date: Jan 2013

    Location: Durham - UK

    Posts: 1,166
    I'm Ken.

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    Yep, 75uf and 68uf are more like standard values and quite a few are available.

    To me 75 + 5% = 78.75uf in worst case and is getting a bit far from the 72uf target, in reality they would probably never be that far out.

    Not a name I've come accross but Ansar "Supersound" range is stocked at Crincklewood Electronics in the UK 75uf are about 35 a go plus postage.
    Size = dia 55mm x L 83mm
    Ken

    http://www.jkwynn.co.uk/
    DIY Technics/ProJect based Turntable + Terminator linear tracker + Denon DL-301 mkII / Pro-Ject Phono box & Pre Box RS / KMTech Active X-Over / Nakamichi AVP1 Power / Yamaha NS1000M / Stello CDT100 Transport / DAC Magic.

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