Turning Infinitesimal 0.3's into 0.2's

[Coastsider]

I have three pair of Infinitesimals, 0.1's, 0.2's and 0.3's (sometimes referred to as III's) and a spare pair of 5" Watkins woofers with black poly cones that I stumbled upon some years back in a mis-identified eBay listing. I am contemplating installing the spare Watkins into the 0.3's to create a new variant - maybe a 0.2.5 - but am not sure how to proceed with the modification of the crossover. Since the 0.2 crossover is closest to the one in the 0.3 with the two slide switches present, I figured that would be the best model to use but would like to solicit opinions as to specifics in adding the Watkins woofer's secondary VC to the mix. I know it would just be easier to find some loose 0.2 crossovers but what do you figure the odds are of that ever happening?

Here are the crossover schematics for both:

http://www.infinity-classics.de/technik/manuals/Infinitesimal_0.2_technical_sheet.pdf

http://www.infinity-classics.de/technik/manuals/Infinitesimal_0.3_technical_sheet.pdf

Ignoring the spec sheet for the 0.3 which say it has a DVC woofer which of course it doesn't, the schematic shows a conventional woofer and so should otherwise be correct. I am going to pull the woofer on one of my 0.3's this afternoon to check the crossover against the schematic.

Any and all suggestions and opinions on this potential project would be appreciated.

 

[elnaldo]

The tweeter crossover slopes are different.

I think the easiest way is to copy the 0.2 crossover... Unwinding the 20mH coil should give you enough material to make the 9.5 and 2.5 coils for the 0.2 clone. Or , get new coils and keep the original for future use. You'll need a 1200uF cap.

Replacing the tweeter cap is not difficult. As for the tweeter 0.2mH, I think you could use the 0.15mH from the 0.3

 

[Coastsider]

Thanks for the great info.

I pulled a woofer to check out the crossover and discovered that unlike every other Infinity speaker I've ever recapped except for my RS 2.5's, the crossovers are not glued and stapled to the back of the cabinet but are instead on a circuit board that is very large and held in place by six machine screws that fit into threaded holes in the aluminum cabinet. I have to go a little further with the dis-assembly by pulling off the kind of glued on front in order to get the crossover out but once out, modifying it will be a cinch. Lots of space on the board and I'll have it right in front of me.

I have to sort out what I need to order before getting started of course. I think I'll just order new chokes and caps rather than trying to come up with what I need from what is there. I figure as long as I'm doing it I may as well do it right and I'm not really in a hurry.

 

[Coastsider]

A couple of photos

I thought I'd add a couple of photos of the surprisingly nice crossover in the Infinitesimal 0.3. Components neatly arranged and for the most part, easy to identify.

I've got a spending moratorium in place at the moment which will probably push this project back a month or two - the first half of California Property Taxes are due on November 1 - but it will give me something to look forward to in the new year.

 

[StimpyWan]

Once you restart this project, I'd love to see a list of which parts you use! I have Infinitesimal 0.3 too, and I'm definitely curious about how this experiment turns out. I hope it turns out well, which it should, since you have the necessary Watkins dual-coil woofers. That's the biggest issue, since those woofers are so rare! :tears:

I 'wonder' if you could build a 'clone' 0.2, using two woofers, instead of the dual-coil woofer? While I know it wouldn't really work, I just wonder what, if anything beneficial it might accomplish? :scratch2:

 

[Coastsider]

Once you restart this project, I'd love to see a list of which parts you use!

I 'wonder' if you could build a 'clone' 0.2, using two woofers, instead of the dual-coil woofer? While I know it wouldn't really work, I just wonder what, if anything beneficial it might accomplish? :scratch2:

I always keep the parts order sheets along with crossover schematics together whenever I do a recap and I will do the same with this project along with photographs, and I'll report back when it is complete.

I don't think using a second 5" woofer with the 0.2 crossover instead of the secondary windings of the Watkins DVC driver would work given the unique design and functionality of the Watkins. I believe the two voice coils operate in an interdependent fashion.

 

[bshorey]

Thanks for the great info.

I pulled a woofer to check out the crossover and discovered that unlike every other Infinity speaker I've ever recapped except for my RS 2.5's, the crossovers are not glued and stapled to the back of the cabinet but are instead on a circuit board that is very large and held in place by six machine screws that fit into threaded holes in the aluminum cabinet. I have to go a little further with the dis-assembly by pulling off the kind of glued on front in order to get the crossover out but once out, modifying it will be a cinch. Lots of space on the board and I'll have it right in front of me.

I have to sort out what I need to order before getting started of course. I think I'll just order new chokes and caps rather than trying to come up with what I need from what is there. I figure as long as I'm doing it I may as well do it right and I'm not really in a hurry.

Building a new crossover also gives you a chance to reverse the mods later should you choose. If you can't reuse the existing boards, consider making new ones. It's not difficult to etch a circuit board from that era, and you have a pair of earlier ones to use as a model.

One quick comment - pay attention to which leads to where on the woofers. Obviously you need to ensure phasing is correct, but my understanding is that the voice coils in the Watkins woofers have different values, and it matters which leads on the crossover go to which voice coil on the woofer.

Take lots of pictures!

bs

 

[Coastsider]

Building a new crossover also gives you a chance to reverse the mods later should you choose. If you can't reuse the existing boards, consider making new ones. It's not difficult to etch a circuit board from that era, and you have a pair of earlier ones to use as a model.

One quick comment - pay attention to which leads to where on the woofers. Obviously you need to ensure phasing is correct, but my understanding is that the voice coils in the Watkins woofers have different values, and it matters which leads on the crossover go to which voice coil on the woofer.

Take lots of pictures!

bs

Creating new circuit boards for the crossovers might be a bridge too far for me but I'm not troubled by removing and changing out components on the existing boards although I will do so in a manner that would allow reversing the modifications later if desired and I will keep the old components. I also know enough to do one complete crossover at a time to avoid any embarrassing "hmmm . . . where does that go" or "where did that come from" moments. And of course I'll have the photographs.

As far as reconnecting the Watkins woofers; I've had some experience with the Infinitesimals and with my RS 2.5's and know to label everything very carefully when pulling the woofers. Bill Watkins shop refoamed the one's in my 2.5's and also did some work on my Infinitesimal 0.1 woofers and they always return them with the connections clearly labeled.

 

[audiomagnate]

The crossovers on the 2.5s are beautiful, probably because they're not hidden inside the cabinet. No hot glue here!

 

[Coastsider]

The crossovers on the 2.5s are beautiful, probably because they're not hidden inside the cabinet. No hot glue here!

Recapping them was great. Just sitting on a chair or stool with them right in front of you. These will be just as easy to work on since I can pull them out and put them on a workbench. WTLC's were the hardest I've done, through the bottom 8" woofer hole.

 

[buzshaws]

As an Infinitesimal .2 owner (also have .1 x-overs too), came across this thread. Hoping to hear more about the rest of the project and outcome.

 

[Coastsider]

As an Infinitesimal .2 owner (also have .1 x-overs too), came across this thread. Hoping to hear more about the rest of the project and outcome.

I never followed through with the project. The Infinitesimal III's (0.3's) are currently shared by a Grace Digital Primo Internet Radio source powered by a Sony TA-F4A Integrated amp, and a Denon Personal Component System consisting of a DRA-F100 Receiver and DCD-F100 CD Player. System selection is done through a Russound AB-2.2 switch. The reason for using the Grace Primo in lieu of the Denon DRA-F100 as a radio source is that I live in an area with no through air reception of any kind.