thomasdf

Urei 809 speaker filter refurbishing : old caps value
« on: April 04, 2021, 12:04:51 PM »
Hello

I am lucky guy : I was given a pair of Urei 809 speakers. The drivers are working, but need refoam. I decided to recone them in order to take a fresh start.
I was also planning to change the electrolytics in the filters but they have old values that are hard to find today :
75uF 100V x2
20uF 100V
4uF 100V

My question is : where can I source these ? Sprague Atoms have these values but I can't find the 75uF 100V (Sprague Atoms is 75uF 16V).
Can I use non polarized capacitors or lower the max voltage (I'd prefer not) ? I am total noob when it comes to filters..

I am posting the schematics here for those of you interested.

Thanks in advance

Thomas
« Last Edit: April 04, 2021, 12:19:51 PM by thomasdf »


jensenmann

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #1 on: April 04, 2021, 12:23:01 PM »
You could replace electrolytics with polypropylene caps. These are available in a huge variety of values since they are used for electric motors. Not cheap, though. Some may think it´s overkill ;-) Check the bigger parts suppliers like RS or Mouser, e.g. https://de.rs-online.com/web/c/passive-bauelemente/kondensatoren/polypropylen-folienkondensator/?applied-dimensions=4291708970

Visaton offers (besides polypropylene) a variety of bipolar electrolytics for crossovers: https://www.visaton.de/en/products/accessories/crossover-parts/electrolytic-capacitors

Since speakers have huge tolerances, even more if aged, I´d not overthink a certain amount of tolerance in your new parts. Buy what gets you closest. Many manufacturers use paralleled caps to get the values needed, btw.
Jens
Quote from: PRR
The tubes of course don't care what frequency they distort

EmRR

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #2 on: April 04, 2021, 12:39:12 PM »
What ^ said.  Going to film caps will be an improvement. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

thomasdf

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #3 on: April 04, 2021, 01:18:22 PM »
Hello, thanks for your answers. Polypropylene seems a bit overkill for my budget indeed, at least for the moment.

I'll check out film caps as well as visaton's bipolar caps.

EmRR

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #4 on: April 04, 2021, 01:48:51 PM »
Hello, thanks for your answers. Polypropylene seems a bit overkill for my budget indeed, at least for the moment.

I'll check out film caps as well as visaton's bipolar caps.

Here in the US Dayton Audio has very affordable film caps for speakers.  Must be something over there. 

https://www.daytonaudio.com/category/36/capacitors
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

thomasdf

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #5 on: April 04, 2021, 02:40:55 PM »
Thanks Doug, I'll check this out :)

Here in Europe I have found F+T Bipolar Capacitors. They are electrolytics, but super cheap (most expensive I need is 1,74 euro at Banzai) and said to be good quality. If I go that route I'll use 4.7uF instead of 4, 22uF instead of 20, and 68uF+6.8uF in parallel giving me 74.8uF for 75uF.
Since the speaker used electrolytics originally I guess it's not THAT bad, so I have this safe and cheap option.
I can easily source Mundorf too, electrolytics bipolar and film also (tho they get quite expensive!!)

-----

After some research, I think I'll go with Jantzen Audio film caps (3.9uF and 20uF) and Mundorf electrolytic bipolar parallel 68uF / 6.8uF. That's the most cost effective solution I have found.

I'll let you know what it sounds like !


radardoug

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #6 on: April 04, 2021, 04:36:54 PM »
So you got the speakers for free, and now you are quibbling about spending money on good caps for the crossovers???

EmRR

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #7 on: April 04, 2021, 07:15:16 PM »

After some research, I think I'll go with Jantzen Audio film caps (3.9uF and 20uF) and Mundorf electrolytic bipolar parallel 68uF / 6.8uF. That's the most cost effective solution I have found.

I'll let you know what it sounds like !

Make that 6.8 a film!
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

Khron

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #8 on: April 04, 2021, 07:26:47 PM »
Motor run caps should be polypropylene most of the times, and available for a handful of bucks a piece (?)...
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

jensenmann

Jens
Quote from: PRR
The tubes of course don't care what frequency they distort


abbey road d enfer

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #10 on: April 05, 2021, 05:05:08 AM »
Motor run caps should be polypropylene most of the times, and available for a handful of bucks a piece (?)...
They look tempting. However I would consider the implications of their warnings:
"Rated Voltage:See Rating Tables.  Rating is the 50/60Hz RMS voltage for a sinusoidal waveform.
maximumFrequency:50/60 Hz. For higher frequencies use General Purpose AC Capacitor Series."
(from the RS datasheets)
So far I haven't seen an explanation of these warnings.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Khron

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #11 on: April 05, 2021, 06:06:41 AM »
They're usually rated for mains voltages (250-400V AC). Sure, that might need derating for higher frequencies (like oscilloscope probes), but if you're expecting over 100V AC (!!!) in your passive (!!!) crossover, maybe that's a good reason to consider going active?
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

thomasdf

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #12 on: April 05, 2021, 06:33:34 AM »
So you got the speakers for free, and now you are quibbling about spending money on good caps for the crossovers???
What I've seen is more between 30 to 80 euros for ONE capacitor.
And it's not because I've been given a pair of speaker that I am rich, and that I have that much money to spend on capacitors.


thomasdf

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #13 on: April 05, 2021, 06:35:43 AM »
Make that 6.8 a film!

Will do ! I was wondering if its ok to mix caps type. Thanks !

Khron

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #14 on: April 05, 2021, 08:36:49 AM »
Yeah, no idea where you've been looking, but...

https://www.tme.eu/fi/en/katalog/motor-capacitors_100263/?s_field=1000014&s_order=asc&limit=20&currency=EUR&page=1

What I've seen is more between 30 to 80 euros for ONE capacitor.
And it's not because I've been given a pair of speaker that I am rich, and that I have that much money to spend on capacitors.


Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

thomasdf

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #15 on: April 05, 2021, 10:04:53 AM »
I'm looking at audio caps, mainly.
Motor caps at RS and Farnell are crazy expensive too... at least in France ?

On the Urei 809 the crossover slide out of the speaker and have some room for the caps, but I'm not sure motor caps would fit, they are quite big.

I just ordered Jantzen Audio film caps, except for the 68uF value I went with Mundorf bipolar. 50 euros worth for both speaker. It's a good start to see how they sound.

Thanks everyone for your help

Khron

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #16 on: April 05, 2021, 10:07:29 AM »
TME deliver all over Europe / the world too, but if "audio caps" make you feel better... ::)
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

mg73

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #17 on: April 05, 2021, 02:29:51 PM »
Please let us know how this  sounds.
I have a pair of 809 I would like to upgrade.

thomasdf

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #18 on: April 05, 2021, 02:54:18 PM »
Please let us know how this  sounds.
I have a pair of 809 I would like to upgrade.

I will :)

abbey road d enfer

Re: Urei 809 speaker filter refurbishing : old caps value
« Reply #19 on: April 08, 2021, 12:56:44 AM »
They're usually rated for mains voltages (250-400V AC). Sure, that might need derating for higher frequencies (like oscilloscope probes),
I'm not concerned with voltage. I'm concerned with the fact they don't recommand these caps for passing higher frequencies, which is something that's bound to happen in a passive x-over. They don't give any hint on what could happen if...
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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