fedeleluigi Posted January 14, 2017 Report Share Posted January 14, 2017 On 13 gennaio 2017 at 1:10 PM, sc-em said: It seems that the original 22 watts 1 ohm resistor in series to the midrange has been replaced by a 10 watt resistor branded RS. This resistor should be 20 watts and preferably not inductive (audio grade) and should be identical for both speakers. Luigi Link to comment Share on other sites More sharing options...
sc-em Posted January 14, 2017 Author Report Share Posted January 14, 2017 They live again! I managed to get some solder onto the joint. Of course it would have been easier before I fixed the board down. Of well live and learn. Probably not the finest bit of soldering ever done, but it held after a gentle tug. All back together and wired and fired up. Nice!!!! Fill the room with sound to say the least. Luigi. Your comment. What impact will the change make you suggested has been done? Thanks for all the help so far............. Link to comment Share on other sites More sharing options...
JKent Posted January 14, 2017 Report Share Posted January 14, 2017 59 minutes ago, sc-em said: What impact will the change make you suggested has been done? I'm not an electrical engineer but I doubt the crossover really needs a 22 watt resistor. The 10w is probably OK. There will be no difference in the sound, it's just the power handling ability. BUT if you decide to do a re-cap you could replace the 10w with a 20 or 25w. PROBLEM IS... neither Madisound nor PE have 1 ohm 20w resistors. Correction--Madisound does have Mundorf Supreme 1 ohm 20w but they're $17 each! Crazy. Here are some from Mouser http://www.mouser.com/ProductDetail/Vishay-Dale/CP00201R000JB14/?qs=sGAEpiMZZMtbXrIkmrvidMRsVRKTjrY3jh39yynJoXs%3d I can see why someone put a Rat Shack resistor in there! I think (please someone more knowledgable check me on this) you could use two 2 ohm 10w resistors in parallel http://www.parts-express.com/2-ohm-10w-resistor-wire-wound-5-tolerance--016-2 The formula for resistance of parallel equal value resistors is R/N (value of one resistor over number of resistors) so 2/2=1 ohm. The power rating is the combination of the two so 10w + 10w = 20w. Anyway, Sheldon Cooper says "psychology is the doofus of the sciences", so don't accept any of my tech advice as scientific fact -Kent Link to comment Share on other sites More sharing options...
ar_pro Posted January 14, 2017 Report Share Posted January 14, 2017 36 minutes ago, JKent said: I'm not an electrical engineer but I doubt the crossover really needs a 22 watt resistor. The 10w is probably OK. There will be no difference in the sound, it's just the power handling ability. BUT if you decide to do a re-cap you could replace the 10w with a 20 or 25w. PROBLEM IS... neither Madisound nor PE have 1 ohm 20w resistors. Correction--Madisound does have Mundorf Supreme 1 ohm 20w but they're $17 each! Crazy. Here are some from Mouser http://www.mouser.com/ProductDetail/Vishay-Dale/CP00201R000JB14/?qs=sGAEpiMZZMtbXrIkmrvidMRsVRKTjrY3jh39yynJoXs%3d I can see why someone put a Rat Shack resistor in there! I think (please someone more knowledgable check me on this) you could use two 2 ohm 10w resistors in parallel http://www.parts-express.com/2-ohm-10w-resistor-wire-wound-5-tolerance--016-2 The formula for resistance of parallel equal value resistors is R/N (value of one resistor over number of resistors) so 2/2=1 ohm. The power rating is the combination of the two so 10w + 10w = 20w. Anyway, Sheldon Cooper says "psychology is the doofus of the sciences", so don't accept any of my tech advice as scientific fact -Kent Kent, Erse sells the 1 Ohm, 25 watt, 5% for sixty cents. http://www.erseaudio.com/Products/WireWoundResistors25w/EWR25-05-1-0-PB Link to comment Share on other sites More sharing options...
JKent Posted January 14, 2017 Report Share Posted January 14, 2017 48 minutes ago, ar_pro said: Kent, Erse sells the 1 Ohm, 25 watt, 5% for sixty cents. http://www.erseaudio.com/Products/WireWoundResistors25w/EWR25-05-1-0-PB Well there ya go. Didn't need those fancy calculations after all. Link to comment Share on other sites More sharing options...
michiganpat Posted January 15, 2017 Report Share Posted January 15, 2017 Jkent, you are right though....2 10W 2 ohm resistors in parallel would make a 1 ohm, 20watt capacity resistor...of course, if they're 5% tolerance, your tolerance zone would double to 10% as well, IIRC... Link to comment Share on other sites More sharing options...
GlennW Posted January 15, 2017 Report Share Posted January 15, 2017 Tolerance improves with multiples, don't remember the formula... Link to comment Share on other sites More sharing options...
fedeleluigi Posted January 15, 2017 Report Share Posted January 15, 2017 On 14 gennaio 2017 at 5:43 PM, sc-em said: Luigi. Your comment. What impact will the change make you suggested has been done? Hi sc-em, In my experience, I had some problem in sound quality using normal ("inductive") ceramic wire wound resistors especially when they were in series to tweeters (but midranges too). I don't really know if the RS resistor is very inductive although it is only 1 Ohm. To learn more about wire wound resistors and their high frequency effects read here.If you use ceramic wire wound resistors for audio application (not necessarily expensive!) you won't have problems. As other members have stated, if you can't find a 20 watt resistor you can put them in parallel to get the rigth values of both resistance and power dissipation (moreover, putting resistor in parallel reduces the overall inductance).They say that in crossover network, carbon resistors generally sound better, but you'd have to put in parallel a lot of them to get the right power dissipation (a parallel of 10 x 10-Ohm 2-watt resistor or 20 x 20-Ohm 1-watt resistor produces a 1-Ohm 20-watt resistor) and check the resistance measure. Otherwise, as I said before, you can simply use ceramic wirewound resistors for audio application.When you play speakers loudly, the midrange resistor power dissipation is very important to avoid an excessive resistor temperature increase that causes the resistance value to increase (with midrange output reduction) and in order not to burn out the resistor itself.It's important to do good solderings so, before soldering, check some good guide and explanation about this topic. Remember dirt is the enemy of a good quality soldered joint!Hence, it is an absolute necessity to ensure that electrical terminals are completely free from grease, oxidation and other contamination. It is also very important not to overheat electronic parts in order not to demage them. Here is a short guide. PS in a vintage speaker it's very important to check capacitors. They are often considerably out of specs and it could be dangerous to tweeters and midranges. Luigi Link to comment Share on other sites More sharing options...
michiganpat Posted January 16, 2017 Report Share Posted January 16, 2017 8 hours ago, GlennW said: Tolerance improves with multiples, don't remember the formula... in my defense, I'm a mechanical engineer, not an electrical one (: and it's sunday.....I didn't want to think tooo hard Link to comment Share on other sites More sharing options...
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