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Old 20th March 2009, 05:28 PM   #1
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Default newbie, needing help with vintage capacitors?

Hello All,
Here's my story:
Hey There,
I recently purchased some speakers to repair as a hobby....... ESS AMT 3 Rock Monitors.... these have 2 woofers, 1 midrange, and the heil tweeter. I refoamed them using the Simply Speakers surrounds but leaving the stuffings in.
So after refoaming the speakers..... I discover that one of the midranges did not work..... Mind you that I have no idea what I am doing, but after removing the stuffing from both speakers I discovered that someone had messed with the crossovers!
I have the original schematics and found which cabinet had the original parts......
I have read on the web about speakers and crossovers, but I am not an electrician, nor am I electrically inclined. I am very good with my hands and have built many models over the years and have even resoldered some stuff (I know....big deal.. hahhaha). So, in the end, I need some help....
the crossovers seem to be as such:
ORIGINAL
El CAP
13 MFD 75 NVP
85C 7401
"axial"
ALTERED
orange coated radial x 4
277P
3.5 + 10% - 100 DC
IDF - M 3.5

ORIGINAL
EL CAP
55 MFD 75 VNP
85C 7348

ALTERED
EMC 15x15
55MFD 75VNP
85C 7349

I guess that my questions are as follows.....
1. How important is it to keep the voltage the same as the original? Or does it not matter as long as it is greater than the original?
2. What would be acceptable to replace the original 13 MFD capicitor? 10+3? or like the altered one 3.5 x4 (14MFD total) or would 3.3 x 4 (13.2 MFD) be better?
3. I realise that this is a highly debated issue, but what should one replace the older electrolytics with? Or will changing from electrolytics to the newer substances (polymers) change the sound too much from the original design?

In the end, I just want to get these speakers up and running and sounding good again...
Thank you
Joshua
P.S. I can send pictures if necessary
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Old 20th March 2009, 08:47 PM   #2
mjf is offline mjf  Austria
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Location: Austria
hello.
you can use the equal voltage rating or a higher (e.g. 100v for 75v) for your caps;
the value of the substituted parts should be close to the original...so 10uf+3,3uf or 3,3ufx4 are a good choice;
change elcaps with elcaps if you want to come close to the original sounds........changing to foil/film/polymer caps can alter the sound significantly..........but if it is better or not you have to decide for yourself (by a listening test),because some like it ,others do not...................
greetings...........
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Old 20th March 2009, 11:15 PM   #3
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Quote:
Originally posted by mjf
hello.
you can use the equal voltage rating or a higher (e.g. 100v for 75v) for your caps;
the value of the substituted parts should be close to the original...so 10uf+3,3uf or 3,3ufx4 are a good choice;
change elcaps with elcaps if you want to come close to the original sounds........changing to foil/film/polymer caps can alter the sound significantly..........but if it is better or not you have to decide for yourself (by a listening test),because some like it ,others do not...................
greetings...........
Thank you for the info!!! Does radial versus axial make a difference?
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Old 21st March 2009, 06:56 AM   #4
mjf is offline mjf  Austria
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usually there is no difference between radial and axial.........
sometimes only the price (radial is cheaper).
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Old 23rd March 2009, 04:59 PM   #5
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usually there is no difference between radial and axial.........
sometimes only the price (radial is cheaper).

Thank you again. One last question, I guess that I asked indirectly before. What is the advantage to a larger sized capacitor.. ie 55 MFD versus 25+25+5? Is there something different about the electrical or sound properties coming from a large value versus multiple small values? Would the mid bass and treble be more responsive with multiple small values rather than a larger maybe sluggish one? Or does it not work like that?
Joshua
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Old 23rd March 2009, 07:01 PM   #6
mjf is offline mjf  Austria
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hello.
if you paralell smaller elcaps to get a bigger value the treble should perform better (this is often done,it should lower the inductivity...........)
but you can add a foil/filmcap to the elcaps that gives you the greater sound effect,in your example this could be 2x25uf elcap and a 5uf (or 4,7uf) "plastic cap" (mkt,mkp,kp.....).this application can alter the sound of your boxes significantly,listen to it!
greetings........
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Old 24th March 2009, 03:16 PM   #7
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Thank you again. I will post the results and the picks of the final project.
Joshua
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Old 10th April 2009, 04:46 PM   #8
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Ok, so I finally replaced everything, learned all about soldering and different solders and fluxes and everything.... have back pain from doing everything inside the cabinet because the crossover could not be removed.....
And in typical newbie fashion............ the darn mid-range did not work.....
I learned all about using a mulitmeter and went through all of my wires with continuity tsting, checked each resistor..... and still could not figure it out......
IT WAS THE FUSE TO THE MIDRANGE!!!!!!!!
So, glad to be a newbie and I hope tht this story entertained... I will still post some before and after picks....
Joshua
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Old 10th April 2009, 06:32 PM   #9
mjf is offline mjf  Austria
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Join Date: Jan 2009
Location: Austria
yes.............the back pain.............
learning by doing is learning for life........
soldering without burnt fingers and parts,.....how to use a multimeter and finding a stupid flaw........never giving up..............
greetings................
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