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crossover mods

post #1 of 6
Thread Starter 

hey guys, im thinking of upgrading the crossover on a set of vintage yamaha ns-1000m speakers. assuming i would upgrade with the same value as original,  i have 3 questions that i hope some mod gurus can enlighten me on.

 

1.would upgrading electrolytics to polypropylene present substantial benefits or should i stick to a modern well made electrolytic (eg Mundorf E-caps)

 

2.the crossover design on the yamaha ns-1000s is fairly complex comparatively as they use 6x 3.5uf in series for a total of 21uf with a 3.5uf in parallel. is there any benefits to the 6x3.5uf in series or can i use one 21uf instead?

 

3.if upgrading from original to polypro caps, what particular make should i use? im really liking these speaker so i wouldnt mind spending larger bucks if the sonic benefits are there.

 

thxs in advance

post #2 of 6

1: Depending on the values of the parts it may be difficult to find anything in a reasonable size. 

 

2: The values of caps in series combine like the values of resistors in parallel. 

Caps in parallel combine like resistors in series.

MFR's commonly use several parts together to get "non-standard" values for crossovers. Changing part values by a few percent can do very weird things to a crossover.  

You don't need a 21uF cap, but it is insanely hard to find 21uF caps if you did. 22uF is the nearest standard value, but rounding values is *NOT* acceptable when replacing crossover parts unless you are in the mood to get your hands realllly dirty and actually redesign the whole thing. 

 

3: Does not matter as much as getting the value correct. No, seriously, I would take an average quality 20uF cap to replace the 20uF cap that is in the crossover over the best 22uF cap ever made by anyone. 

 

If you really like the speaker I would not mess with it. 

post #3 of 6
Thread Starter 

yaa i really really like this vintage Yamaha NS1000M so i'd like to keep it for as long as i can. ive owned this set for a few mths now & ive noticed the speaker going thru some weird (to me) break in changes that another headfier has pointed to the old crossover caps "reconditioning" itself either due to age or lack of usage.

 

because the crossover had a mix of films & electrolytics, im thinking of just swapping out the electrolytics for similar value films/polyprops as the simplest way for an upgrade. there's also a guy who has redesigned a complete new crossover but besides the not insignificant cost, im not sure i wanna screw with the factory sound (which im seriously diggin). 

 

here's his site with schematics of the OEM crossover. any tips and ideas on how to do full recap while keep factory values would be greatly appreciated. 

post #4 of 6

These Yamahas are "worth their weight in gold" .In the UK they are much sought after and command high prices. Even at high levels they have very low distortion compared to other speakers. When they came out in the UK they were priced at £600 which would be around $900. That was a lot of money  in the 80s Inflation now price would be probably $2000. You get a buyer in the UK for that.Do NOT  change the values of the crossover by all means change the electrolytics and if you want the smaller values but remember to buy ones with the same working voltage  and the electrolytics will be bi-polar [two way working] I have a lot of reference information if you need it For MC speakers they have a pretty level FR but are a "difficult load"  as the impedance drops to 4 OHM at 80 HZ  so use a powerful clean amp. Some "lumpiness at mid-treble but apart from that Great!

post #5 of 6
Thread Starter 

yaa i plan to keep them if for nothing else, as a reference to transparency & dynamic transient response (one could call it quickness i guess :D). so far even in my limited room, it sounds fab with most genres but i did turn the mids control down a db or so. these NS1k are keepers for sure & im willing to invest in some time & effort to get the best out of them. 

 

cabinets can do with a refinish (or an exotic veneering) & of the crossovers. after doing more research on old caps in xovers, there is a phenomenon known as capacitor reforming but its usually done with delibrate applied current/voltage from an outside source transformer of some kind. could this be what im hearing with changes in spl levels after a few days & the bass "coming out" after a few mths?? or im thinking it could be that the previous owner recapped them & im hearing the breaking process?

post #6 of 6

Yes they are great speakers .Check to see if the caps in the crossover have been replaced although I doubt it. More likely electrolytic s have changed value due to "drying up". Same type of thing happened to all the old tube radios I have repaired. Yes reforming -I built 2 reformers to a design in a now extinct electronics mag . The electrolytic reformer  is connected directly to the mains via diodes etc. I housed it in a small  plastic box to isolate it . It has 2 settings one for 500V working caps and a switch for 250V workings ones that I added to  the design.It ha\s an neon light that glows and when it goes out the caps is reformed . It includes another switch to lighten the current load as if you apply full load when first used  - BANG!!!  As your mains is approx 120V there would have to be step up if you were reforming 500V types . But usually the ones in cross-overs are a much lower voltage so 120V would do. But they are dangerous and it would be better to replace the electroyltics with more modern ones -DONT buy cheap. Buy top quality audio types for the electrolytics  I use Polypropylene for smaller values and if the low value ones are say around- 001UF/1000PF/1NF then buy Polystyrene they might be dear as many companies have ceased to make them but in terms of -can I say it?-subjective reproduction they sound great.As backed up by JLH and Cyril Bateman- Capacitor design engineer.

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