Hi folks, this is my first post here. I've toyed with building speakers in the past, but never got around to it. While this isn't it either, I do think I'm a bit out of my depth and kindly ask for some help or guidance.
I got ahold of a beautiful dali helicon center speaker, but with one mid/bass driver dead. I took it out and measured the impedance with my multimeter and sure enough it's in the KOhms range.
Part 1: Figuring out if the rest is good
Apparently the other drivers should work fine, but I'm not exactly sure how to figure that out. I've disconnected and measured them and they seem to be ok:
Is this enough data to confidently say they should be fine?
Part 2: Finding replacements
From what I've managed to gather the Helicon drivers should be very similar to Vifa M18WO (not sure exactly which model, does the measured impedance imply it's the 6-Ohm version?). The issue is, those Vifas are decades old as well, so finding them doesn't look like it'll be an easy task.
How should I go about finding a newer, in-stock model that might be a close match? I'm not looking to get it 100% identical to the original, but definitely hoping to get close, at least on a quality level. Would like to match performance as much as possible as I'm using the Helicon 400 towers as my mains.
What numbers should generally tell me if the driver "fits"? Physically, sure, I can figure that one out (I hope). But electronically, sonically? That's where I'm lost.
Also, is it okay to replace just one of the mid/bass drivers or should I go ahead and replace both?
Part 3: Tweaks
Ideally the replacements work fine and that's that. But if there is work that needs to be done on the crossover, I guess I could try. I know my way around a soldering iron, at least for basic operation. I have a vague understanding on what the crossover's elements do, but not enough to comfortably tackle this on my own. Is it bound to come to that and if so, how should I go about it? The crossover is definitely hard to reach, so it's the part I'm least excited about. 🙂
Edit: I didn't even notice it before, but there is a big black spot on that crossover. Is it safe to assume that something burned? How can I go about solving that puzzle?
I took some pics in case they might come in handy:
I got ahold of a beautiful dali helicon center speaker, but with one mid/bass driver dead. I took it out and measured the impedance with my multimeter and sure enough it's in the KOhms range.
Part 1: Figuring out if the rest is good
Apparently the other drivers should work fine, but I'm not exactly sure how to figure that out. I've disconnected and measured them and they seem to be ok:
- Ribbon: 8.5 Ohm
- Dome: 5.8 Ohm
- Mid/Bass #2: 6.4 Ohm
Is this enough data to confidently say they should be fine?
Part 2: Finding replacements
From what I've managed to gather the Helicon drivers should be very similar to Vifa M18WO (not sure exactly which model, does the measured impedance imply it's the 6-Ohm version?). The issue is, those Vifas are decades old as well, so finding them doesn't look like it'll be an easy task.
How should I go about finding a newer, in-stock model that might be a close match? I'm not looking to get it 100% identical to the original, but definitely hoping to get close, at least on a quality level. Would like to match performance as much as possible as I'm using the Helicon 400 towers as my mains.
What numbers should generally tell me if the driver "fits"? Physically, sure, I can figure that one out (I hope). But electronically, sonically? That's where I'm lost.
Also, is it okay to replace just one of the mid/bass drivers or should I go ahead and replace both?
Part 3: Tweaks
Ideally the replacements work fine and that's that. But if there is work that needs to be done on the crossover, I guess I could try. I know my way around a soldering iron, at least for basic operation. I have a vague understanding on what the crossover's elements do, but not enough to comfortably tackle this on my own. Is it bound to come to that and if so, how should I go about it? The crossover is definitely hard to reach, so it's the part I'm least excited about. 🙂
Edit: I didn't even notice it before, but there is a big black spot on that crossover. Is it safe to assume that something burned? How can I go about solving that puzzle?
I took some pics in case they might come in handy:
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I would try checking the impedance where the braided wires enter the cone. I forget the name of that type of wire (litz?) but it does wear out. Next step is to cut off the dust cap and see if there is a good connection to the voice coil under there. If so you can just replace the litz and epoxy the cap back on.
Do not cut of the dust cap! With most speakers I know, it is fixed with a temperature sensitive glue.
As long as you don't overheat, you can take it off without hurting it.
I use a hot air gun with a nozzle to concentrate the air on the center.
As long as you don't overheat, you can take it off without hurting it.
I use a hot air gun with a nozzle to concentrate the air on the center.
Replace the defective driver with nothing but the exact original replacement driver.
https://www.dali-speakers.com/en/about-dali/contact-us/
https://www.dali-speakers.com/en/about-dali/contact-us/
If Dali still has such a chassis, this would be the best solution. Please accept that these drivers have not been cheap for the end user when available.
If not from Dali, I don't think you have any chance to get the exact type. The OEM versions had different data in many cases. It looks like the 4 strut Viva version, that was replaced by the 5 strut basket. The only way to get a near to similar driver is to measure it. The impedance curve and TSP parameter are a first, if you are serious about it, taking the defective driver apart and measuring coil height and magnet gap helps even more.
Then you may compare to still existing drivers from Vifa-Peerless-Tymphamy or the Scanspeak discovery line, which have continiued some of them.
Even if it may be a beginners first thought, measuring the frequency response doesn't help when searching for a spare part. The replacement has to work with the existing crossover and this is an electrical and TSP thing.
If not from Dali, I don't think you have any chance to get the exact type. The OEM versions had different data in many cases. It looks like the 4 strut Viva version, that was replaced by the 5 strut basket. The only way to get a near to similar driver is to measure it. The impedance curve and TSP parameter are a first, if you are serious about it, taking the defective driver apart and measuring coil height and magnet gap helps even more.
Then you may compare to still existing drivers from Vifa-Peerless-Tymphamy or the Scanspeak discovery line, which have continiued some of them.
Even if it may be a beginners first thought, measuring the frequency response doesn't help when searching for a spare part. The replacement has to work with the existing crossover and this is an electrical and TSP thing.
Thanks everyone! I'll measure it at the cone when I get home, though I have low hopes as the braided wires look relatively intact. I also went ahead and sent an email to our official distributor to see if an original replacement is still available.
What freaks me out now is the burnt part on the crossover, looking at it more, this has to be a sign of a major issue, right?
Is there a way for me to measure if the crossover elements work properly?
What freaks me out now is the burnt part on the crossover, looking at it more, this has to be a sign of a major issue, right?
Is there a way for me to measure if the crossover elements work properly?
The copper coil will not heat up that much, the white resistor is the cause for the burn mark. Without knowing the schematic of the crossover any guess is just that. Looks like extreme overload. Maybe the center was driven full range, without high pass by some idiot that "liked the sound better that way". Must have been quite a long time of abuse, typical for a drunken party defect.
Look what value is written on it and get a new one, it is brocken. Maybe 2$.
Look what value is written on it and get a new one, it is brocken. Maybe 2$.
Thanks, I got in touch with Dali, the driver is still available, just waiting to hear back from the dealer regarding pricing. I also asked for the crossover schematics which they couldn't give, but told me the specs for the exploded resistor. Then I guess we'll see if that's all that is broken. 🙂
So after a month and a half of waiting I finally received the replacement driver. Almost cannot believe they still stock these, as the line hasn't been in production for over 15 years at this point.
Thinking about it now, I want to do this the right way and just replace most, if not all crossover elements (I imagine the coils should be fine, but the capacitors and resistors could do with an upgrade). Does anyone have recommendations on where to get some good quality parts? Preferably within the EU, if possible.
Thinking about it now, I want to do this the right way and just replace most, if not all crossover elements (I imagine the coils should be fine, but the capacitors and resistors could do with an upgrade). Does anyone have recommendations on where to get some good quality parts? Preferably within the EU, if possible.