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Got stuck into these today,ive replaced all internal wiring,new posts and replaced all the caps,all in all its been well worth it.
add this to the Nakamichi ca5 i bought and its 2 steps forward,im just wondering when the 3 steps backwards will happen! :)
cross over before,
http://i1267.photobucket.com/albums/...ps8ijajtqm.jpg
and after,
http://i1267.photobucket.com/albums/...psiel3nhel.jpg
Nice tidy job Jamie. Sound any different?
thanks grant,yes there is an improvement in the top end.
Well done Jamie.
thanks paul,it was a good project for me,whats your veiws on the so called "burn in period"?
also a point of interest is that they really used any old combination of caps to get the final value,both cross overs had differences,for example for the mid,one board had a total value of 30mfd made up of one 24mfd cap and one 6mfd cap,the other board had a 24mfd cap and an 8mfd cap. the specs say total of 30mfd so i stuck to that.
i might do the other pair of ditton 44's next,these will be easier as they use the newer circuit board type board.
Hi JamieQuote:
Originally Posted by jamie123
there are various reasons why each side might have been different. Some manufacturers (KEF for example) matched crossovers to drivers to meet a reference response curve. Left and right crossovers may have been slightly different for that reason plus making up larger values from smaller ones is actually a good way of tightening up overall tolerances (eg 30uF at 10% could be 27uF or 33uF whereas you are more likely to get it closer to 30uF using a mix of lower value 10% caps). However, Ditton 44's were not made to individual references AFAIK, so it could simply be that they used whatever they had in the factory to get them close. That was very common for many manufacturers in the 60's, 70's and 80's.
RE settling in (I don't use burn-in terminology as its inaccurate), at the voltages concerned, it usually takes 250V polys for example a few hours to fully stabilise, sometimes more, sometimes less. I've certainly found no measurable difference in any cap for crossovers after say 10 or 12 hours. Resistors resist, that's it! Inductors are just pieces of wire with no dielectric of any consequence to stabilise so are what they are although some cored inductors, depending on rating, will exhibit some degree of hysteresis.
It's not crossover matching that matters really, its the effect of the filter transfer function on the acoustic response. The aim is for equal acoustic response. With modern drivers though which are usually a 1% or less match from the factory, it is true that most modern x-overs are equally matched.
another jiffy bag of caps arrived today so i set about changing the caps on the later dittons 44's with the pcb crossover.
i decided not to change the mid and hf caps as these are not electrolytic's,the other reason is that on the earlier 44 i changed the lot and although i was happy with the sound the bass seemed to be slightly down,i think this was the new polys for the mid and hf,i may be wrong of coarse.
any way the cap change was a doddle unlike the older hard wired board! first impressions are the bass is back in line with the mid and hf,the speakers sound in balance if you know what i mean and very smooth!
http://i1267.photobucket.com/albums/...pskjx2mart.jpg
i plan to do the internal wiring and posts later.
Been busy again today,ive sold the early pair of 44's ,they sounded lovely with all caps changed and re wire so it was time to do the later pair with the pcb crossover.
whislt i was at it i thought id try them with fresh caps to the hf and mid,the rest had already been done previously.
After reading through the ditton 66 thread i wanted to try kens electrolytic/pp mix for the mids,the stock cap was 24uf,ken recommended a mix of 23uf electrolytic and 1uf pp for a bit of sparkle to the mid,this was done along with fresh ansar super sounds for the hf.
http://i1267.photobucket.com/albums/...psbeslthlm.jpg
I also wanted to get rid of the celestion block connector and solder the wires directly to the board.
http://i1267.photobucket.com/albums/...psd6qoqmgv.jpg
mounted back in the cabinet with new speaker posts fitted and all wiring replaced. a noticeable improvement and well worth doing!!
http://i1267.photobucket.com/albums/...psx4lzv23z.jpg
Well as you've got a few quid in your pocket now Jamie. Just grab these:
http://theartofsound.net/forum/showt...onitor-SGM-12X
You'll never look back!
(you know we'll convert you one day :D )
lol you never know! although any spare cash is going in the holiday fund at the moment :)