Mods, please remove if discussion about capacitors is not allowed.
I have built some three way speakers with a DSP crossover (Nanodigi) and got them to a point where I like the sound and have decent nulls (good phase alignment). So the next step is to try my hand at a passive crossover.
I have used my measurements and Vituixcad to design a passive crossover which gives a similar response to the DSP crossover I like. However, I do not have a stock of parts so will be buying from scratch. For capacitors, and to mock up a first try, is it acceptable to use MKT (Jantzen Compact MKT Metalized 5% Polyester Film Capacitors) for the woofer low pass and mid low/high pass and MKP (Jantzen Standard) for the Tweeter High pass filters. This would half the price of the parts as a first mock up (compared to using Jantzen MKP Cross Caps).
Thanks in advance for responses.
I have built some three way speakers with a DSP crossover (Nanodigi) and got them to a point where I like the sound and have decent nulls (good phase alignment). So the next step is to try my hand at a passive crossover.
I have used my measurements and Vituixcad to design a passive crossover which gives a similar response to the DSP crossover I like. However, I do not have a stock of parts so will be buying from scratch. For capacitors, and to mock up a first try, is it acceptable to use MKT (Jantzen Compact MKT Metalized 5% Polyester Film Capacitors) for the woofer low pass and mid low/high pass and MKP (Jantzen Standard) for the Tweeter High pass filters. This would half the price of the parts as a first mock up (compared to using Jantzen MKP Cross Caps).
Thanks in advance for responses.
My understanding is that the voltage rating is most important in passive crossover parts. Nothing under a 50 volt AC rating. Having said that, you will routinely see 250v and higher ratings for these parts.
I'm not sure that it makes any difference as far as the circuit itself is concerned what caps are being used in the low pass as opposed to what is being used in the high pass portion of the circuit.
I'm not sure that it makes any difference as far as the circuit itself is concerned what caps are being used in the low pass as opposed to what is being used in the high pass portion of the circuit.
Mock-ups traditionally use whatever is in your junk box. It's fine.
Keep the leads reasonably long, so the parts can be reused over and over.
Only when the design has been very refined should you spend real money on parts.
Keep the leads reasonably long, so the parts can be reused over and over.
Only when the design has been very refined should you spend real money on parts.
As long as you plan to build more speakers in the future, having excess crossover parts on hand is a good thing. I use the std. Daytons mostly. I still have some that were purchased 30 years ago. Someday, I might can sell what's leftover for a few cents on the dollar. Right now, I probably have over $500 in parts, but $200 would be a good starting point to get started. Obviously order what you think you need, but don't expect the sim to match reality. I used to use x-over parts to get the order minimum high enough for free shipping.
Do you have data that you can share on this? I'm curious. I would be even more curious for an explanation of why one would distort more than the other if they're using the same dielectric.
As far as I understand it, the primary difference between metalized film (MKT) and metal film (MKP) is that the MKP has more metal, thus, lower ESR. That could be important in some applications, speakers not being one of them. I also seem to recall that there could be differences in how the capacitor respond to overload, i.e., whether the capacitor self-heals after a dielectric breakdown or not.
Tom
As far as I know, MKP means polypropylene dielectric and MKT polyethylene-terephtalate dielectric. See the famous Wireless World/Electronics World articles of Cyril Bateman for distortion measurements.
They are available here, but I don't know how long they will remain available:
https://linearaudio.net/cyril-batemans-capacitor-sound-articles
By the way, Bateman did also measure distortion differences between metallized and film-and-foil capacitors with the same dielectric. The metallized ones had more spread of the distortion, if I remember well. I think Bateman put the blame on not very good contacts inside the metallized capacitors that distorted more than the others.
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If you want to save money, look for other sources of MKP caps besides Jantzen. I found some 520 vdc 10 uf kemet MKP at newark for < the cost of jantzen. $1.95 vs $8 jantzen at P-E today. I picked up some 20 uf 400 vdc ASC MKP caps at the closeout of allelectronics for $1.50. Today jantzen at P-E $12.18. To compare dc ratings versus ac, divide dc by 1.4.
In terms of the performance of MKT, I replaced paper dielectric wax cased caps (now unavailable) with MKT in a dynaco PAS2 preamp. A channel imbalance had developed. It wasn't until I replaced the last cap of 22 that I found the kit builder had burned through the wax case of that one. He hid the damage at the bottom, which did not stop oxygen from getting in. I really did not like the sound of the preamp after. I quit using it, going to a Herald RA-88a op amp disco mixer. No going back, the PAS2 has been stolen.
In terms of the performance of MKT, I replaced paper dielectric wax cased caps (now unavailable) with MKT in a dynaco PAS2 preamp. A channel imbalance had developed. It wasn't until I replaced the last cap of 22 that I found the kit builder had burned through the wax case of that one. He hid the damage at the bottom, which did not stop oxygen from getting in. I really did not like the sound of the preamp after. I quit using it, going to a Herald RA-88a op amp disco mixer. No going back, the PAS2 has been stolen.
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Ah. No doubt that different dielectrics will make a difference.
Turns out I choked on the alphabet soup and got MKT/MKP vs FKP/MKP mixed up.
From WIMA:
FKP = polypropylene dielectric, metal foil
MKP = polypropylene dielectric, metalized film
Foil caps have more metal in them so they will have lower ESR.
MKT is a bit of a mixed bag. Some manufacturers (Vishay) use polyester dielectric in their MKT caps. Others (TDK) use polyethylene terephthalate (PET) dielectric in their MKT caps.
As always: Read the data sheet. Personally, if I bother with the expense and bulk of a film cap I will always use polypropylene dielectric. That's the lowest distortion film that I'm aware of. To go lower, you need C0G/NP0 ceramic (see Bruce Hofer's AES presentation from around 2013 for details).
Tom