C-Core Auto-Transformers

[SET12]

Seems a few of us have bought these German C-Core Auto-Transformers from Werner in Germany paying around $260/pair which includes shipping.

Thought I would go over these a little with hook up and some measurements.

As you can see is substantially larger then the stock Forte T10A I was using and a bit larger then the Crites as well. I don't have a side by side photo of the Crites and C-Core but if you contrast the Crites to the stock I think you can see that the C-Cores are substantially larger yet over the Crites.

Since sony6060 is building a pair of Forte networks with these and North Creek Inductors I thought some measurement information might be useful.

So here is what I did. The photo on the right of the photo below is the hook up instructions from Werner

My C-Cores have 14 -1db taps otherwise they are shipped with -1.5db taps.

I used my Variac connected between #0 and #15 on the C-Core.

The meters are basically identical models and are very close to one another in measurements being no more than .02 volts difference.

In the photo I was connected to the -8db tap or #8 as labeled and of course #0 for ground (found it to be closer to -9db) and as you can see incoming voltage is 6.33VAC with the step-down being 2.16VAC.

The step down in db for the math is 6.33/2.163 = 2.93

Take the log of 2.93 =.466 x 20 = 9.33db down

I checked the other taps on both transformers and found them the same.

#7 8.0 db

#8 9.3db

#9 10.3db

So I'm using the #8 as this is the closest and would work best for the desired crossover frequency of the Fortes network as designed.

SET12

 

[jessearias]

keep us posted

This is a great post!:yes:

A bit expensive for my budget but, very interesting. It most certainly looks like a top shelf product. Keep us posted on your results. I would like to see how this turns out.

I am curious how you set up the taps on the auto transformer to get the frequencies you need. :scratch2: They were always a little mysterious to me on how they worked.

 

[sony6060]

Finished wiring new crossovers a few minutes ago. Thanks again. You agree with 1.5dB taps, #6 tap is best. Note the better silver/oil Mundorf at midrange & higher-end Obbligato for woofer. Mundorf Supreme capacitors are used in the tweeter circuit with Kiwame termination resistor.

 

[SET12]

Very good :thmbsp:

Its possible that the #5 tap might be right on as my #9 tap is 1.3db more then its suppose to be. You'd have to measure this to be sure.

 

[Frank Sol]

Finished wiring new crossovers a few minutes ago. Thanks again. You agree with 1.5dB taps, #6 tap is best. Note the better silver/oil Mundorf at midrange & higher-end Obbligato for woofer. Mundorf Supreme capacitors are used in the tweeter circuit with Kiwame termination resistor.

Looks GREAT !

How do they sound ?

 

[SET12]

This is a great post!:yes:

A bit expensive for my budget but, very interesting. It most certainly looks like a top shelf product. Keep us posted on your results. I would like to see how this turns out.

I am curious how you set up the taps on the auto transformer to get the frequencies you need. :scratch2: They were always a little mysterious to me on how they worked.

Thanks for your comments,

I to had wondered yrs ago how it worked, but it was ALK's explanation of Klipsch's networks short comings in his eye's of what was going on that triggered my understanding of it.

But really the Auto-Transformer works like any other transformer only the Autotransformer is just a single winding with taps.

I'll be back to explain.

SET12

 

[sony6060]

Looks GREAT !

How do they sound ?

See my new post 'are you kidding me'..........

 

[jessearias]

need pictures

Curious people like me need to see pictures!:yes: I hope you post some pictures of your completed crossover and maybe a wiring diagram with specifications. :yes:

Am I asking for to much? :nono:

From what I can see so far, they look beautiful. Nice workmanship. :thmbsp:

 

[SET12]

See my new post 'are you kidding me'..........

It was great! It put quite a grin on my face

SET12

 

[SET12]

Curious people like me need to see pictures!:yes: I hope you post some pictures of your completed crossover and maybe a wiring diagram with specifications. :yes:

Am I asking for to much? :nono:

From what I can see so far, they look beautiful. Nice workmanship. :thmbsp:

Thank you!

Here is a link to my Forte 1 crossover thread with all my mods that I did to them. http://www.audiokarma.org/forums/showthread.php?t=159340

Page 12 has a lot of photo's of my current crossovers.

Page 23 I added caulk rope to the horns

Page 33 where you can see more photo's of the C-Cores

Page 30 and 31 is some serious testimonials to the sound quality, take a good look at the stock B&W crossover vs the North Creek out board crossover on page 31 that many recording studios are buying from him as well as many consumers. Here is a link to the B&W mod at North Creek http://www.northcreekmusic.com/801web.html

The same similar characteristics of improvement are had from the mods I have done to my Fortes.



Here's a photo of my networks

Here is the schematic

All parts are original values, the inductor DCR's will be different but they really are not an issue with this network.

You can see the contrast of the stock network here

 

[UH1DG337]

want some too

Where does one go to buy these autotransformers?

 

[sony6060]

Where does one go to buy these autotransformers?

Go to eBay Germany. Perform a search for auto transformers and these beauties comes up. About $45 shipping & two weeks delivery to at least NYC.

 

[UH1DG337]

Thank you for the info. I couldn't wait to get them ordered.

 

[sony6060]

Cannot find them on ebay.de
Anyone have the link or Werner's ebay user/store name?

Use ebay advance search. Then scroll down to 'Location' and click on second dot that stated 'Located in'. Then select Germany from the list.

Next, in keywords at top of page use the words 'auto transformer'. The parts comes up & I believe about the third item down on listings.

 

[SET12]

Use ebay advance search. Then scroll down to 'Location' and click on second dot that stated 'Located in'. Then select Germany from the list.

Next, in keywords at top of page use the words 'auto transformer'. The parts comes up & I believe about the third item down on listings.

Thanks sony6060, I was out of town for the weekend.

 

[sony6060]

Thanks sony6060, I was out of town for the weekend.

It appears more are coming over to your side (x-overs).

 

[UH1DG337]

double check wiring!

I have had these auto-transformers for about a month now and they are a must have imo.
However after I added the ti mid's the speakers were a little brite.
I didn't specify the taps when I ordered, so I assumed they were 1.5 dB. so I hooked up tap#6 and listened away.

This weekend I decided to measure the output the way SET12 outlined.
with no access to a variac I used a wall transformer from a video game.
the 9 volt, 1.3 amp ac out transformer actually measures about 9.7-9.9 volts. when I checked tap #6 I found it was only 7dB reduction not 9.
tap# 7 = 8 dB
tap# 8 = 9.3 dB
this mirrors SET12's measurements earlier in this thread.
so I got 1 dB taps without specifying.

just a side note: I found the stock transformer T2A tap #2= 9.5 dB reduction.

 

[SET12]

That's great information, and as you must of saw pretty easy to do.

Its also easy to get mixed up referencing ground which would present different measurements.

Very good work :thmbsp:

SET12