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Ren. 90's midrange dies- is it the EMIM?

H

HDJR808

Active Member
Had the stereo on last night and a sudden drop in the left channel occurred. Ear up to the drivers, I find no output from the high energy EMIM midrange. Crap.:yikes:

I have a spare driver, so today I pull out the old one and install the new one. Still nothing from the midrange. :scratch2:

The replacement EMIM is one I picked up a few years ago as insurance against just this kind of thing. It read 3.5ohms which seems correct, so no dead short or open circuit. The driver that came out reads the same.

So I am looking for some insight into where the fault might lie here. It seems like what I've read about the Infinity planar drivers is that the typical failure is that they go open. Is it possible for the EMIM to be faulty and still read a nominal 3.5ohms?

I have yet to look at the schematic I have for the crossover to see if there is any obvious component feeding the mid that would fail suddenly. I did pull the woofer and the bottom panel to see what I will be getting into if there is a crossover repair in my future, and I can see that things will be a challenge. There will be a lot of de-soldering of the driver leads to get access to the boards.

If anyone has any first-hand experience with a similar failure, or any suggestions at all, I would appreciate it.

Thanks- Herb
 
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Shouldn't be any fuse on the EMIM, just the EMIT. Not a lot to go wrong in the crossover, just some inductors and four caps. Just a guess, but it must be one of the four caps, as the EMIM sounds like it's OK. Check those and see if any are gone.

David
 
I'd say:

1. If there is a pot, clean and inspect it.

2. If there is a fuse, replace it. If there is a reset button, check it for correct functioning, and reset it.

3. Check all capacitors, and when in doubt --or if they are aged originals-- pull 'em out and replace them with known good, new ones. Might be a good time/excuse to upgrade to superior "audiophile" caps.

4. Re-flow all solder connections.

5. Check the wires and connections between the crossover and the speakers (EMIMs) for continuity, and make sure the connections are good at both ends.

6. If the above steps fail (or perhaps before trying them), try swapping the apparantly dead EMIM with the still-functioning EMIM in your other speaker. This will confirm whether it is the EMIM itself or something else that is causing the problem. If it is not the EMIM, I think one of the above steps should cure the problem.

GOOD LUCK! :thmbsp: As I'm sure you realize, your speakers are worth pretty much whatever it takes to keep them singing! :music: :yes:
 
if the emim reads 3.5 ohm you can be pretty sure its fine. If you have any old drivers laying around, you could connect a 3-6 (maybe 8) ohm mid or tweeter. if nothing happens on the conventional speaker it must be the crossover. If the emim are easy to remove i would place then old emit in the working speaker. but again, if it reads 3.5 ohm im pretty sure the crossover or internal wiring is dead.
 
Agreed, sounds like the EMIM is fine. Mine measure right around 4 ohms (fellow Renaissance 90 owner here). Just to make 100% sure, you could swap the EMIM in question into the other speaker to check functionality.

The outcome of that should tell you where to look next. My guess is something in the crossover; remember that these speakers are almost 20 years old, and nothing lasts forever. Fortunately there are no tone controls to check, fuses to reset, etc.
 
Thanks for all of the responses- just getting back to looking at things.

As some have said, I am considering the 3.5ohm reading on the Emim to be a good indicator that the driver itself is sound.

And yes, there are no pots or fuses (except for the tweeter) to be problematic.

I did find today, when I hooked them up again to make sure that the mid was truly not working before I tried to drag my Sigma's downstairs as a temporary replacement, that the Emim would intermittently work as I changed the volume level. No discernible distortion, just cutting in and out.

Would this be typical for a dodgey cap or inductor? Maybe a cold solder joint?

Anyway, I guess they will stand in the corner for a while until I can get some time to figure out the problem, and most likely do some crossover rebuilding.

Thanks-

Herb
 
Sounds like a dry joint on the crossover board. I have some pictures of the crossover in these things. They are not the most convenient design to work on. Looks like the upper frequency section maybe awkward to get at.

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The bass section.

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As I start looking at what I might need to repair/refurbish this speaker, I have come to find that the non-polar electrolytic caps used in the crossover look to be a potential problem to replace.

They are all 100v caps, and not only is there the impossibly large 882uf cap, but even with the smaller caps, the values of many of them are not a standard item that I can locate.

Even from what I can find in the Tecate Group literature, their line of T.I. (same as original) caps doesn't offer the 72uf, 140uf, 265uf and 280uf sizes, even in the lower quality 10% DF range.

http://www.tecategroup.com/capacitors/datasheets/aluminum/RNTN.pdf

I've spent hours searching the usual suspects of parts sources, not only Mouser and Digi-key who have nothing to offer as crossover caps, but the speaker builder sites like Parts Express, Madisound, E-Speakers, Speaker City, and also the more exotic suppliers like Michael Percy and Sonic Craft, and there seems to be a very small selection of 100v npe caps out there.

Erse seems to have some selection, and I suspect that they are the supplier for Parts Express, but the values available would require some interesting paralleling of caps to get even close to the correct values. My understanding is that paralleling is not a bad thing for ESR, but if I have to combine caps for several of the necessary values, space is really going to be a problem.

Am I missing something? Are there more sources out there that I just haven't found?

And I have just started to get into what the options might be for replacing the film caps, and that is even more mind-boggling in terms of choices and opinions. I know that the film caps are not going to have an age issue like npe's but the original Solen's are considered only a moderate quality cap at best so I do want to investigate higher quality replacements since I'm going to be in there. Any suggestions?

Infinity certainly didn't make it easy for us to deal with these things 15-20 years down the road...

Thanks- Herb
 
for NPE's, just go with the plain ones from PE or the Bennics from Madi. you can get very close to the correct values if you are willing to parallel caps together, and for the little extra amounts you can use a film cap to get the exact amount (i'd probably use a little bypass cap too). now, if the NPE you're having trouble with is in the midrange circuit, especially in the direct signal path, then it pays to use electrolytics as little as possible. for example, you can go 50/50 NPE/film to save money. in the bass range, the difference between using films and NPEs is much less noticeable, and for large values especially i wouldn't hesitate to go NPE.
 
HDJR808 said:
As I start looking at what I might need to repair/refurbish this speaker, I have come to find that the non-polar electrolytic caps used in the crossover look to be a potential problem to replace.
Click to expand...

Yes but what is the original fault ??

I wouldn't waste time and money replacing all of those caps especially the NPE's because that is not where the fault is.

you should unscrew the mid-high crossover pcb and check to see if there are any broken wires, dry joints or cracks in the copper tracks. Given that there are high pressures in the enclosure this may very well be what has happened over a period of time.

regards
 
Yes but what is the original fault ??

I wouldn't waste time and money replacing all of those caps especially the NPE's because that is not where the fault is.
Click to expand...

Well, the original fault is still a mystery. I did get the speaker up on the bench today and started pulling the drivers so I could free up the internal wiring so that the crossovers could be removed. At this point, the crossovers and drivers are out and the cabinet is empty, but I will need to wait till another day to do some troubleshooting.

I'm not assuming that any specific npe is the fault in the intermittent EMIM. It is probably a bad solder joint or another mechanical fault as was suggested, especially since I have already found a couple of dicey connections in the woofer crossover. The first was while I was desoldering/removing one of the leads from the woofer and as I moved it back and forth to work the connector off the spade lug, the connector broke in half, with the female part remaining on the spade lug and the crimp body coming off with the wire. Not any overt use of force, just a little wiggle to get it off while the solder was melted (definitely scary to have to de-solder all of those tab connections) so that spade connector was obviously just shy of falling off by itself.

The other interesting mechanical issue was on the woofer crossover board, where the common connection of the negative input, negative output for both coils, and the leads from the 100uf 280uf caps and .5ohm resistor are joined. The cable leads are soldered around a short section of wire which is run between holes in two tabs screwed to the board, and the leads from the caps and resistors are soldered to the tabs. I found that the section of wire was completely free from it's solder joint and rotates in the holes in the tab. Not exactly a solid connection.

But my concern about the npe caps is based on the logic of trading out electrolytics that are at least 15 years old, and therefore at the end of their lifespan, if not already past it. This crossover assembly is a pain to get out, so it would be foolish not to do some necessary maintenance while it is accessible.

As far as wondering about film caps, this is much more of an arbitrary opportunity to potentially upgrade the components that were originally chosen based upon either economics or the quality available at the time. I doubt that today's variety and quality of film caps designed for audio use were available nearly 20 years when these things were being designed and manufactured.

So, the NPE's definitely need to go. I am just concerned about the lack of choice of candidates to replace them. The film caps may stay; I just have to figure out if there is potentially any real benefit in replacing them, and what caps would be best to use if I do.

Thanks- Herb
 
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