Rebuilding Infinity Infinitesimal Reference Standard 0.1

[cowanrg]

This past weekend I picked up a pretty rough pair of Infinity Infinitesimals for $100. I figured it was worth it just for the cabinets and tweeters alone. It was assumed they would be a project (he said they didn't work), but I didn't expect all the crap that was wrong with them.

First, the leads on the 700uf caps broke off. Someone attempted to solder them back together, but the aluminum body doesn't solder well :-) The caps measure OK, but I can't get leads soldered back on them, so there's that.

Next, someone tried to repair the woofers. The signal wires inside the cone got disconnected and he tried soldering them to the cone. So, there are big globs of solder on the cone, and he used 14AWG wire it looks like. It's bad. I'm not sure of the woofers can be salvaged as the cone might be compromised. Also, the dust caps are gone and the edge of the voice coil looks a beat chewed up.

The good news is that the cabinets are in OK shape (wood might need to be replaced, but the rest of it is fine and the rest of the crossover looks good) and the EMITs seem fine as well.

So, I either want to fix these up and sell them, or just keep them as a secondary speaker. I'm not THAT familiar with speaker-building, but the crossover looks VERY odd to me. Here it is;

http://www.bobbyshred.com/images/Inf...1TechSheet.pdf

Also, can the woofers even be replaced? I can't seem to find them anywhere (of course, they're old) and I wouldn't know what to use. But seriously, what's up with that crossover? I've never seen such high values in a crossover.

These are cool little speakers and I'll post some pics later tonight once I get home from work.

[woody]

I believe that woffer will have 2 windings. One will handel the all the bass frequencies
then the other will be crossed in a lot lower probably around 100 hz or so. At least
that is my quess. Way back then Focal also sold some woffers that had duel voice
coils that were used that way.

[cowanrg]

Originally Posted by woody

I believe that woffer will have 2 windings. One will handel the all the bass frequencies
then the other will be crossed in a lot lower probably around 100 hz or so. At least
that is my quess. Way back then Focal also sold some woffers that had duel voice
coils that were used that way.

yeah it does have dual VCs, one is at 4 ohm and the other is at 2 ohm. But the caps are 700uf and 1200uf. Are these just non-polarized electrolytics?

[cowanrg]

OK, so I know you guys like pictures, so here are some pictures of the speakers. They are completely torn down right now and look a LOT worse like this. But whatever, I will end up probably completely rebuilding them. The woofers are probably completely shot now that I look at them again.

the speakers themselves (minus grills and wood end caps)


trashed woofers:


these have a really cool cabinet design. it's an extruded piece of aluminum with mounting rails for the crossover and a place for the metal baffle.


the capacitors snapped off from the board. sigh.


the actual caps. any advice on how to solder leads back on them? they measure fine.




I'd really appreciate if anyone could explain what's going on with the crossover though. I get what's going on with the tweeter, but what's happening with the woofer? A 700uf and a 1200uf cap? I get that there's two voice coils, but 700uf seems ridiculously high. What frequency is that crossing over at? I've looked at tons of calculators online and can't seem to figure it out.

[adason]

yes, the caps in woofer crossover are there to extend low fr response, its a "deep-bass-small-cabinet" concept, if you need more info read Tony Gee's site on Black Box design
plus it offers DC protection as well

[cowanrg]

Originally Posted by adason

yes, the caps in woofer crossover are there to extend low fr response, its a "deep-bass-small-cabinet" concept, if you need more info read Tony Gee's site on Black Box design
plus it offers DC protection as well

ah ok. I'll check it out. thanks.

[cowanrg]

ah ok. It works like a subsonic filter. neat. and since there's a 2 ohm and 4 ohm voice coil on the same woofer, you need the two different values.

on a separate note, does anyone think the woofers are salvageable? with holes in them, I'd think not, but I don't know much about driver repair.

[picowallspeaker]

Originally Posted by cowanrg

ah ok. It works like a subsonic filter. neat. and since there's a 2 ohm and 4 ohm voice coil on the same woofer, you need the two different values.

on a separate note, does anyone think the woofers are salvageable? with holes in them, I'd think not, but I don't know much about driver repair.

If you lend them to some skillfull technician or just amateur , it should be no tricky job ...just glue and patches

Regarding the electrolytics , they act quite the opposite as you may think :
to limit the excessive peak in closed box , you can stuff the box very heavily ( not this case ) or add a capacitor in series with the woofer ; so it cuts the peaks ( damping )caused by a too high Qtc and you'll hear a less 'punchy' bass , thou more extended

[cowanrg]

Originally Posted by picowallspeaker

If you lend them to some skillfull technician or just amateur , it should be no tricky job ...just glue and patches

Regarding the electrolytics , they act quite the opposite as you may think :
to limit the excessive peak in closed box , you can stuff the box very heavily ( not this case ) or add a capacitor in series with the woofer ; so it cuts the peaks ( damping )caused by a too high Qtc and you'll hear a less 'punchy' bass , thou more extended

ah. there's a speaker repair guy here in town that's supposed to be good. I might get a quote on them. the edges of the voice coil are kinda bent too. I guess he'll just just to look at them to see. I didn't realize so much could be salvaged on a driver...

[picowallspeaker]

If the coil's still intact , why not ?
Still about the electrolytics .... In a closed box there's only one peak of impedance : above that peak the argument is mostly inductive , but before the peak it's capacitative , so the amplifier can deliver more current , thou a beefier bass