Query: Crossover caps in 20+ year old UREI/JBL speakers.

[doodlebug]

I've gotten the wild hair to replace some of the older caps in my current lineup of speakers, UREI 809 (original series) and JBL 4425s. They're all original but I note that there are some electrolytic caps on the UREIs that most likely could stand to be replaced since they were in pretty constant use through the 80s and 90s from what I know about their history at Fantasy Records.

So, the query is: What experiences others have had in replacing (not modifying) the original components in their older speakers? Good/bad/indifferent?

Many thanks for your considerations and comments.

Cheers,

David

[speakerdave]

This subject has been discussed a great deal. Let me refer you to the search function. Crossover, capacitor, bypass, charge couple. Put on some music, make a large mug of something hot and good. Sit comfy. You have some reading ahead.

David

[doodlebug]

but didn't get back much. Thx, I'll try again.....music's already running, too.

Cheers,

David

[Ian Mackenzie]

David,

There are some specialist sites on the www that go into great detail about the Urei crossovers. I don't own either so I can't comment further.

Ian

[jpb_dk]

hi David

Please dont get the message wrong. But Mackenzie is one of the "old" guys and have see that question so many times that he.......... (right Mackenzie ? )

The thing is YES there are really something to go for and something to win by changing caps, resistors, cables ect.and in crossover of a good speaker..
(how maby times pr 20 year do you change oilfilter on the car to keep it update???? ) just to make a little fun of it. Yep the caps go down like a oilfilter.

If you are new to the forum i will agree with you that the search function does not give much value, (unless you use "advanced").. Its like google. You'll get the answer you ask for - sometimes.

Many like to help, but we need to know more. Give us what You've got
Thanks, Jens

[Ian Mackenzie]

Actually what I was saying is there is more specific information (read that better) external to the Lansing forums on sites where Urei enthusiasts have rebuilt these crossovers.

I am not aware of any specific data on the forums relating to your enquiry. There has however been plenty of discussion regards the history of the Urei drivers and the variations.

If its a non polarised electro capacitor replace it with a new equivalent specification type and see what happens. I would imagine the driver has been voiced for the original parts, thus altering the type would potentially change tonal character.

As I said above, I have seen a whole www page dedicated to the time aligned Urei crossovers. You are best to enquire further a field. I imagine the people at the official Altec Lansing page may also be able to offer the benefit of their experience as the Urei drivers were developed from the Altec 604.


Edit: Sorry David I was thinking of is here however it relates to Altec time aligned crossovers, :http://home.earthlink.net/~jmarkwart/

Non polarised elctro capacitors are not the ideal choice for crossovers and as Robert said you might bypass them.

Ian

[Robh3606]

Looking at the schematic I would add .001UF caps in parralel on the larger value electrolytics and possibly change out the series caps to the horn or try adding the .001 there as well to see if it makes a worthwhile change. The delay caps are large value and would be expensive to swap out with the ultra high quality film and foil caps. I built up an 811C crossover from scrath and used Parralel/bypassed/trans caps. Have nothing to compare it too but it sounded good.

http://www.jblproservice.com/pdf/URE...s/809A-L,R.pdf
Rob

[rek50]

db, Cap replacement can be a hard to tame "Wild Hair", considering all the choices/theories etc. Electrolytic caps are usually smaller than their uF equivalent in a Metallized Polypropylene, or a Film and Foil Polypropylene, or Mylar caps... Consider the space on the boards if you decide to go with these larger caps. New Electrolytic caps are an option, as they should be "Fresher" in value/function compared to the old ones. Soldering in new caps opens yet another "Door". Which solder? 2%, 4%, or 6% "Racing" Silver bearing Solder, or my favorite, Kester Hi-Tech Electronic Rosin core. Then, consider hook-up wires. Same AWG, or larger? PVC jacket, or Teflon? Straight OFC or Silver Plated/Coated? If you do one board at a time (For A/B testing), the old cap board "Harmonics" won't exactly "Mesh" with the new cap board. Do them both at once, and see if you remember the "Old Sound" compared to the "New". Did the new ones "Burn In" yet? . If you carefully remove the old components, you can always go back. IMO, there's more "Sport" in trying to "Improve", and the "Hunt" is worth it, especially if it is an actual improvement...

[grumpy]

FWIW:

might want to contact this guy (no relation... just recalled seeing the ad), in addition to googling for Urei crossover mods/updates web pages.

http://cgi.ebay.com/UREI-813b-Subwoo...QQcmdZViewItem

-grumpy

[doodlebug]

I appreciate all the support. Actually, Ian, I did just as you said and discovered that I'd not used the right keywords in the search - result of too much cognac before the use of the search facility.

So, after looking at the crossover drawings for the 809A - I have the version prior the 809 - there are differences in component values but they look pretty similar in circuit topology. This is interesting since the documentation at JBLpro.com seems to indicate the use of the same crossover module for the 809 and 809A.

Anyway, based on the discussions here over the past few years and the permutations available, I've decided to stay close to the original schematic/topology with these priorities:

1) Bypass the film caps that are in there now with .001s

2) Replace the electrolytics even though they're non-polarized.

3) Replace the HF in-line coupling cap

This appears to be the most cost-efficient approach, too. I'm sure there's a law of diminishing return playing out here in terms of results and investment. As I've done with other rebuilds, I'll listen and take notes on changes at each step. The nice thing about the UREIs is that the crossovers are really easy to get to without tooling down the entire speaker setup.

Oh and, Grumpy, I saw that guy with the 813 subs and his comments as well. This is actually what got me thinking about this. Heck, why would I want him to do the work for me when that's where the fun is?

Thanks again to everyone for all the help. If this works out well with the UREIs then I may tackle the 4425s, mainly with bypass caps as I do not see them in there now.

Cheers,

David

[gerard]

I change all my caps in my 434x clone crossover adding by pass .

Result was much more soundstage in the midrange and what I still do not understand when I change the bass caps the result was much cleaner and tight bass using the same range of capacitor but going to solen 400vdc !!!
At the end I had a new system ! .

Regards

Gerard