Yamaha NS-344 Speakers The Definitive Thread (Maybe)

[SonicTemple]

After benefiting from the work of others for years, I've finally decided to give back to the community. I recently purchased a set of vintage Yamaha NS-344 speakers off eBay. They're in really good condition but I noticed when listening that the right midrange speaker wasn't producing much sound. I swapped the right for the left and there still wasn't much sound coming from it and the right speaker in the left cabinet sounded fine (so its not the speaker). I also swapped the mid level pads and still not much sound coming out of the right midrange speaker (so not the level pad). Really the only thing left is the crossover and so down the rabbit hole I went.....

I'm a 'do it myself' kinda guy with limited electrical experience but I can normally figure things out eventually. I started by removing the woofer and inspecting the crossover on the back of the cabinet. Everything looked normal. No loose wires. No leaking/bulging capacitors. I was really hoping there was something obvious but there wasn't. I looked online for a schematic for the crossover so I could figure out which capacitor(s) were inline with the midrange but couldn't find anything. So I drew one up along with a crossover layout. I put them into TinyCad and attached them here for future reference to all. I couldn't find any info on the inductors (maybe its stamped on the bottom). If anyone knows or sees an error in my drawings or has a recommendation for something to add, let me know.

This'll be my first post, I'll add others as I work my way through removing the crossover and replacing the capacitors.

 

[SonicTemple]

Ok, I got the crossover out. Not sure how anyone could work on it while its mounted in the cabinet. As noted in other threads, the board was screwed and glued to the back of the cabinet. I removed the screws and used a hairdryer to heat up the board and loosen the glue on the back. Then I used a butter knife to slide under the board and slowly pry it off. It worked. I probably could have done a better job with a little more patience. See photos.

 

[SonicTemple]

The capacitors in question are the two upright ones in the previous post photo. The ones I labeled C-2 (18 uF) and C-3 (3.3 uF) in the layout diagram. They're both 50v but my understanding is that the voltage doesn't matter that much and it more important to match the impedance. I found matches for both at Parts Express.

C-2 Dayton Audio DMPC-18 18uF 250V Polypropylene Capacitor $6.59 each

C-3 Dayton Audio DMPC-3.3 3.3uF 250V Polypropylene Capacitor $1.82 each

I also found matches for the other capacitors:

C-1 Dayton Audio DMPC-2.7 2.7uF 250V Polypropylene Capacitor $2.12 each

C-4 Dayton Audio DMPC-18 18uF 250V Polypropylene Capacitor $13.48 each

These are all much better than the originals in terms of tolerance (5% vs 20%). My dilemma now is do I go ahead and just replace all of them in both speakers? Or am I going to far? Total cost would be around $50. If I was going to go this route I'd also upgrade the binding posts to these (I really don't like spring clips):

Parts Express Gold Binding Post Banana Jack 5-Way Speaker Terminal

I'm guessing there wouldn't be a significant sound difference in re-capping all (other than presumably fixing the midrange issue I'm having). But there's also the fun factor to consider........

 

[SonicTemple]

......I ordered all the capacitors from Parts Express......and a Weller WE1010NA Digital Soldering Station from Amazon....I think I'm in too deep to turn back

 

[Ed in SoDak]

Interesting thread. You'll be all set for all sorts of mischief with that Weller.

I have a pair of the NS-500. They needed refoamed and one tweeter was blown. I managed to dissect it and make the repair. No such luck on swapping in new capacitors, the crossover on these are potted!

 

[Ed in SoDak]

I'll be watching for when you have time to show the rear view of the drivers. I didn't see any nudies in a quick image search on Duckduckgo.

The NS-500 is only a two-way ducted port bass reflex and they sound superb to me. They do have the beryllium tweeters. I'm the second owner since scoring them in 1985.

 

[SonicTemple]

I'll be watching for when you have time to show the rear view of the drivers. I didn't see any nudies in a quick image search on Duckduckgo.

The NS-500 is only a two-way ducted port bass reflex and they sound superb to me. They do have the beryllium tweeters. I'm the second owner since scoring them in 1985.

I’ve been looking at the 500s, they look nice and I’m sure sound excellent. I’ll be posting a lot of photos once I get into it. Couldn’t find a lot of info on the 344s so I want to put as much info into this thread as I can to help future restorers.

 

[SonicTemple]

Interesting thread. You'll be all set for all sorts of mischief with that Weller.

I have a pair of the NS-500. They needed refoamed and one tweeter was blown. I managed to dissect it and make the repair. No such luck on swapping in new capacitors, the crossover on these are potted!
View attachment 2085943

Yeah there’s no getting to those.