If you have read this previous article, probably you got my point when reading this one. Now, I’m doing the modification for the speaker. After several serious examination (well, you know me, I can’t be more serious than this time), it seems that there is no hope for the tweeter. So let’s find a good replacement. After googling around for several hours, I stick to the Vifa XT25SC90 tweeter. I use the ‘older’ brother XT25TG30 on my other DIY speaker and quite convinced with its sonic quality (despite its poor off axis performance). Price wise, you can get a pair less than $50. What a bargain?
Hmm… the small size also make it easier to be mounted. But surely I will not mount just like that, huh?
Okay, let’s do some drilling job and put the XT25 on the original face plate. Not the neatest job in the world, but it can get the job done perfectly (I mean without affecting too much sound itself).
Once I finish mounting the tweeter, I just realize that the woofer also occasionally not working 🙁
Oow… This can’t be good! After digging around and contacting some colleagues, I find a similar woofer. It should be local made, but with custom specification. With 10 Ohm specification (8 Ohm original from the Mission), I think I’m gonna need some crossover correction. From short listening session, it seems the woofer is working fine with the old enclosure. So I could be more than happy to work out the crossover (if the woofer got too different Qts, probably I’m gonna throw this away immediately).
Now time to do some surgery on the crossover. First, I remove the original bipolar capacitor. Due to its age, I don’t think I have good reason to keep it there. So I throw it to the garbage bin without any doubt. I put Bennic XPP on it. As the XT25 is 4 Ohm, while the original tweeter should be 6 Ohm, then I adjust the original capacitor value from 5.6 uF to 6.8 uF. Sound wise, it’s not bad. But it seems the tweeter and woofer still have some gaps.
I put another 0.22 uF of K40Y to force the tweeter playing even lower. Still it doesn’t give me satisfactory result. Without measuring device, doing this is just like walking in the dark. But I do enjoy this kind of trivia games 🙂
If lowering the tweeter doesn’t get the job done, then we have to work on the woofer. As I have mentioned before that the woofer is 10 Ohm replacing the original 8 Ohm, so frankly speaking, the first order low pass must be altered in order to maintain the similar cut-off frequency. I dig my parts bin and find 2 big roll of copper wire. One of them has the size that I need, around 1 mm diameter. Well, lucky me!
I solder the copper wire to extend from the original inductor. As easy as abc!
Then do some winding work. I approximate around 25% additional from the original winding, which translates to around 25-30 turns (don’t ask me how do I get the number, they are just flying over my head). Winding is done, then time to try the result.
Well, it seems still not enough to satisfy my poor ears. Another 10 turns please…
Now the sound is well acceptable for the woofer. I got enough punch for the low, good male vocal, and quite a good blend from the tweeter. Though I think I’m still missing something here…
Aha, time to change the resistor also? I still have Eagle from Madisound which costs me around $1 each. Not bad, huh? All parts taken from my parts bin. So practically speaking, no additional cost involved.
The Bennic seems slightly to high in terms of the value. So after another digging session, I find my old Siemens capacitor in parallel configuration resulting of around 5 uF something. This Siemens capacitor, although considered as oil-type, but has a slightly sharp and forward sound. Exactly what I need to be paired with XT25.
Putting all them together. The result? This is the final crossover tweak which resulting the sonic that I need.
Heat gun used to seal the XT to the original face place. This can prevent some air to leak around.
The woofer also got some additional seal tape around the corner.
Then the heat gun do the rest to seal the woofer from leakage possibility.
Some painting job, anybody?
La la la… Painter Song from Norah Jones is played during this session…
Also, I need to work out a speaker cable. The original NYAF cable. Dirty? Yeah.
Clean them up with small knife (ignore the rust on my old knife, please!).
Shiny copper? For sure!
Put enough tin and solder them to prevent the rust invading the cable.
Perfect termination! Anti-rust and trouble free speaker cable.
So up to this point, the result of the speaker is on my satisfactory level. It doesn’t sound like high-end speaker, but it gives enough clarity, enough low frequency, and good tonal balance. I’m not saying this can give ultra resolution or whatsoever. But if you trust my ears, then all I can say is the speaker is now quite enjoyable. I spend several hours listening and can enjoy them. But my wife says now the speaker sounds good, but I think your DIY speaker is better than this one (yeah honey, if only you know how much do I spend on that one ha~~~).