Replacing crossover

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pewternhrata

Audioholic Chief
For Boston A120s, best place to buy replacement parts. 1 of each per speaker, non polar 4.7mfd 50wv, 10mfd 50wv, 16mfd 50wv, 2.5 ohm 10%.
Figured it would be a good project to do. Any specific brands to look for, Also clueless as of to what the numbers mean.
 
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everettT

everettT

Audioholic Spartan
Is there an issue with the parts?


Edit: madisound and Parts express are where I purchase most crossover parts.
 
P

pewternhrata

Audioholic Chief
Not sure if there is an issue, figured they are about 30yrs old so it couldn't hurt to replace them. Don't see to much info on 'vintage' gear around here.
 
TLS Guy

TLS Guy

Seriously, I have no life.
Not sure if there is an issue, figured they are about 30yrs old so it couldn't hurt to replace them. Don't see to much info on 'vintage' gear around here.
I have posted boat loads on vintage audio over the years on these forums.

I have some advice for you. If you are not sure you have an issue and are "clueless" about all this, leave it alone. Otherwise we will have a multitude of posts bailing you out when you are certain you have an issue.
 
P

pewternhrata

Audioholic Chief
I have posted boat loads on vintage audio over the years on these forums.

I have some advice for you. If you are not sure you have an issue and are "clueless" about all this, leave it alone. Otherwise we will have a multitude of posts bailing you out when you are certain you have an issue.
So your saying it's pointless to be taught and learn more about the hobby. Thanks for the "advise"

I looked up and found the parts I need to replicate the original xovers, I'll wish myself my own luck.
 
Verdinut

Verdinut

Audioholic Spartan
Not sure if there is an issue, figured they are about 30yrs old so it couldn't hurt to replace them. Don't see to much info on 'vintage' gear around here.
If the capacitors are of the electrolytics type, it would definitely be worthwhile to replace them with appropriate polypropylene ones. Solen is probably as good if not better than anything else. Parts Express and, I believe, Madisound sell them. You can also purchase directly from Solen.ca -You would definitely get quite an improvement by doing so.

On the other hand, if the caps are of the polypropylene category, you don't have to replace them as their value does not change over time as is the situation with the electrolytic type.
 
P

pewternhrata

Audioholic Chief
If the capacitors are of the electrolytics type, it would definitely be worthwhile to replace them with appropriate polypropylene ones. Solen is probably as good if not better than anything else. Parts Express and, I believe, Madisound sell them. You can also purchase directly from Solen.ca -You would definitely get quite an improvement by doing so.

On the other hand, if the caps are of the polypropylene category, you don't have to replace them as their value does not change over time as is the situation with the electrolytic type.
How do I tell what type, guessing a quick Google could answer. what about the 2.5 ohm resistor, I do know that one is ceramic.
 
Verdinut

Verdinut

Audioholic Spartan
I'm not absolutely sure but I think that most electrolytic capacitors have a metallic color finish or are covered by a kind of plastic like envelope. Just google electrolytic capacitor and look for images and/or search on the Parts-Express website . You should obtain your answer.

I know for a fact that several well established loudspeaker manufacturers, KEF is one of them, used electrolytic caps in expensive enclosures which they were marketing. As a matter of fact, I did replace some for a friend. He had used it for many years, but what difference when we listened to the speakers after the replacement. You would have believed they were completely different speakers with an opened and detailed sound as never before.

The capacitor values which you listed have a low 50 volt rating or so. On the other hand, polypropylene caps have a higher voltage rating, notably 250 volts or more, but they are a lot bigger than their electrolytic counterparts. Of course, that can create a few problems when trying to install these bigger ones which do not fit in the tiny spaces allocated for the original ones. The final look might not be as esthetic but those filter boards are hidden in the cabinets anyway. As you know, it's the sound performance that counts.
 
P

pewternhrata

Audioholic Chief
From what I understand uf is essentially the same as mfd, and that value I want to match. The 50wv is the max voltage that it can hold so I would see no ill effect from going with 100v (if the original capacitor was undersized, then I would see an improvement)
Big thanks for the input, I'm not expecting a night and day difference, but I would expect some improvement. I plan on just rewiring all of them, new xover components, and new polyfil (I heard that can deteriorate over time) Mostly for peace of mind, my father purchased these from a dealer so I grew up listening to them. He's shocked that I still have and use them lol. Should be a week or so before I order everything, I'll let ya know how it turns out.
I'll learn what I can and use it as a stepping stone to someday build a pair of bookshelves.
 
TLS Guy

TLS Guy

Seriously, I have no life.
If you want to pursue this, the you might want to purchase this.

Then you can measure the caps and see if the need replacing. If you do replace them then I would use Solen polypropylene ones.

For resistors I like to use ones rated to at least 10 watts.
 
Swerd

Swerd

Audioholic Warlord
For Boston A120s, best place to buy replacement parts. 1 of each per speaker, non polar 4.7mfd 50wv, 10mfd 50wv, 16mfd 50wv, 2.5 ohm 10%.
Figured it would be a good project to do. Any specific brands to look for, Also clueless as of to what the numbers mean.
Not sure if there is an issue, figured they are about 30yrs old so it couldn't hurt to replace them. Don't see to much info on 'vintage' gear around here.
pewternhrata

Many owners of speakers about 30 years old, believe that rebuilding the crossovers of their old speakers is a good project to do. The internet is full of easy-sounding advice on this subject. However, it also can be like opening a "can of worms".

The first advice I'd offer is, If it ain't broke, don't fix it. I am not being facetious about this. What evidence do you have that your speakers aren't working right? What evidence do you have that the crossovers are failing or have failed?

You've already gotten good answers from Verdinut and TLS Guy for your simpler questions. Some (but not all) older non-polar electrolytic (NPE) capacitors can drift out of spec due to drying of their electrolytic solvent. It's usually a gradual process, but sometimes there is total failure due to greater leakage or a burst capacitor.

NPE caps were made, and can be still made very cheaply. Often they're made to somewhat sloppy specs. Imagine that you need two 8 µF caps, and you buy cheap NPE caps, labeled 8 µF ±10% (meaning they will be anywhere from 7.2 to 8.8 µF). You might have to buy 10 or 20 of them before you can be sure you have two caps that are actually 8 ± 10% µF.

In new crossovers for DIY projects, most builders favor using new metallized polypropylene (MPP) capacitors. These are made by rolling up a thin film of plastic coated with a very thin layer (sputtered on) metal conductor. They should never drift or fail. In the past they were less available and much more expensive than NPE caps. Now they cost a bit more than NPE caps, but they almost always measure exactly the capacitance value printed on them. Solens (mentioned above by TLS Guy and Verdinut) are good, but so are others that can be less expensive. See the Dayton 5% MPP caps sold by Parts Express, or the Bennic MPP caps sold by Madisound. Both "house brands" are made in Taiwan, perhaps by the same manufacturer.

Now on to the real question you should be asking – will my 30-year-old speakers sound better if I rebuild the crossovers while replacing crossover components? Yes, but only if the old capacitors have drifted out or spec or have failed. Despite the common internet wisdom, there is no guarantee this is the case for your speakers. The resistors and inductors coils are unlikely to have failed. Sometimes resistors burn out, but that should be easy to see.

This also raises another bigger question. Is the 30-year-old crossover design on my speakers a good design? Or, will a new design (done by someone competent with modern design tools) actually work better? If you're going to the effort of replacing old caps, that may or may not have drifted out of spec, why not examine the old crossover design to see if your speakers would sound better with a new and different design? Why stop with crossovers? What about replacing old drivers with newer designs? This is that "can of worms" I mentioned above, getting opened. If you have to ask a simple question, such as what does mfd mean, I don't think you are ready to design a new crossover for your 30-year-old speakers.

That's why I and others are reluctant to offer simple advice to newbies about 'recapping' the crossovers on older speakers.
 
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Verdinut

Verdinut

Audioholic Spartan
pewternhrata

Many owners of speakers about 30 years old, believe that rebuilding the crossovers of their old speakers is a good project to do. The internet is full of easy-sounding advice on this subject. However, it also can be like opening a "can of worms".

The first advice I'd offer is, If it ain't broke, don't fix it. I am not being facetious about this. What evidence do you have that your speakers aren't working right? What evidence do you have that the crossovers are failing or have failed?

You've already gotten good answers from Verdinut and TLS Guy for your simpler questions. Some (but not all) older non-polar electrolytic (NPE) capacitors can drift out of spec due to drying of their electrolytic solvent. It's usually a gradual process, but sometimes there is total failure due to greater leakage or a burst capacitor.

NPE caps were made, and can be still made very cheaply. Often they're made to somewhat sloppy specs. Imagine that you need two 8 µF caps, and you buy cheap NPE caps, labeled 8 µF ±10% (meaning they will be anywhere from 7.2 to 8.8 µF). You might have to buy 10 or 20 of them before you can be sure you have two caps that are actually 8 ± 10% µF.

In new crossovers for DIY projects, most builders favor using new metallized polypropylene (MPP) capacitors. These are made by rolling up a thin film of plastic coated with a very thin layer (sputtered on) metal conductor. They should never drift or fail. In the past they were less available and much more expensive than NPE caps. Now they cost a bit more than NPE caps, but they almost always measure exactly the capacitance value printed on them. Solens (mentioned above by TLS Guy and Verdinut) are good, but so are others that can be less expensive. See the Dayton 5% MPP caps sold by Parts Express, or the Bennic MPP caps sold by Madisound. Both "house brands" are made in Taiwan, perhaps by the same manufacturer.

Now on to the real question you should be asking – will my 30-year-old speakers sound better if I rebuild the crossovers while replacing crossover components? Yes, but only if the old capacitors have drifted out or spec or have failed. Despite the common internet wisdom, there is no guarantee this is the case for your speakers. The resistors and inductors coils are unlikely to have failed. Sometimes resistors burn out, but that should be easy to see.

This also raises another bigger question. Is the 30-year-old crossover design on my speakers a good design? Or, will a new design (done by someone competent with modern design tools) actually work better? If you're going to the effort of replacing old caps, that may or may not have drifted out of spec, why not examine the old crossover design to see if your speakers would sound better with a new and different design? Why stop with crossovers? What about replacing old drivers with newer designs? This is that "can of worms" I mentioned above, getting opened. If you have to ask a simple question, such as what does mfd mean, I don't think you are ready to design a new crossover for your 30-year-old speakers.

That's why I and others are reluctant to offer simple advice to newbies about 'recapping' the crossovers on older speakers.
The Parts-Express and Madisound brands of polypropylene capacitors may be made in Taiwan, but the Solen Fast Metalized Polypropylene caps are made in France.
 
P

pewternhrata

Audioholic Chief
If you want to pursue this, the you might want to purchase this.

Then you can measure the caps and see if the need replacing. If you do replace them then I would use Solen polypropylene ones.

For resistors I like to use ones rated to at least 10 watts.
The resistor in now is 3w, I haven't been able to find any info if I were to replace it with, let's say 15w. Only 2.5 ohm I found on madisound was 15w.
Bennic has capacitors that match, brand that is currently used.
Looking at around $30 for both, we'll within my 'piece of mind' budget.

Depending on how this project goes, and if I start buying more vintage gear again, I'll definitely look into that tester. So far I'm learning more than i thought, it's not as difficult to start understanding the values with a real life project in front of me (even if it's as simple as just swapping out components) I'm able to see where they are in the circuit and what role they play first hand.
 
Swerd

Swerd

Audioholic Warlord
The resistor in now is 3w, I haven't been able to find any info if I were to replace it with, let's say 15w. Only 2.5 ohm I found on madisound was 15w.
If your old crossover has a 2.5 ohm 3 watt resistor, you can replace it with another 2.5 ohm resistor rated for 15 watts. It will handle greater power. But why are you replacing that resistor? Is it blackened or cracked? Or will removing it from the old board leave the leads too short?

Do you have a schematic diagram for the Boston crossover? If there are several NPE caps on the old board, there may not be enough room for the new larger MPP caps. If you have the schematic, it would be easier to layout the components on a new board.
 
Swerd

Swerd

Audioholic Warlord
If you can't find a suitable 2.5 ohm resistor, buy two 5 ohm resistors and wire them in parallel to each other.

1/Rtotal = 1/R1 + 1/R2 + … 1/Rn

If R1 and R2 are both 5 ohm,
1/Rtotal = 2(1/5) = 0.4
Rtotal = 1/0.4 = 2.5 ohm
 

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