Jump to content

t2-a autoformer power handling and bandwidth


Guest " "
 Share

Recommended Posts

Anyone know the max power handling and bandwidth of the T2A autoformer?

I did a search on the forum, but did not come up with anything.

Would settle for info on one of the after market ones.

post-22082-13819318046236_thumb.jpg

Link to comment
Share on other sites

I never look at the low end of the autotransformers below about 400 hz, but I see the top end on every crossovoer I build or rebuld.  They are all flat as a pancake out to beyond 25 khz.  That goes for the T2A, 3636 and 3619.  I think they go down to about 20 hz flat also, but never checked there since in the Klipsch crossovers we never use them below 400 hz.


Don't know a power rating except that they must be capable of more than 40 watts.

Bob Crites

Link to comment
Share on other sites

" I think they go down to about 20 hz flat "

Based on my measurements they are 3dB down at about 75hz at the 30W level. Not a problem for the intended use.

Thats helpful info.

Link to comment
Share on other sites

  • 12 years later...
On 12/18/2006 at 10:10 AM, BEC said:

I never look at the low end of the autotransformers below about 400 hz, but I see the top end on every crossovoer I build or rebuld.  They are all flat as a pancake out to beyond 25 khz.  That goes for the T2A, 3636 and 3619.  I think they go down to about 20 hz flat also, but never checked there since in the Klipsch crossovers we never use them below 400 hz.

 
Don't know a power rating except that they must be capable of more than 40 watts.
 
Bob Crites
 

 

Bumping this 13 year old thread.

 

I'm testing an adjustable Type-A crossover. The attached schematic shows the basic circuit. The T2A will be replaced with a Bob Crites 3636.  More importantly, the input wire to the autoformer will be terminated with a female quick connect, and can be connected to taps X, Y, or 5.  The autoformer end of the wire to the 26uf cap will also be terminated with a female quick connect, and can be connected to taps 1, 2, 3, or 4.  This will allow midrange attenuation of -1 to -12 in 1 db increments, without any change to the crossover frequency (419 hz using a 14.6 ohm resistor in place of the K-55).

 

I built a prototype of the midrange portion of the crossover, and it appeared to work flawlessly. 

 

I also tested a 20 hz 6.75 volt signal across 0-5.  The voltage across 0-4 measured 4.8 volts...pretty close to the 4.75 volts I expected.

 

It's been said that this circuit will not work well due to the high voltage of lower frequencies.  However, the current through the autoformer is identical to the stock Type-A circuit at all frequencies.  Is autoformer saturation a product of high voltages, high current, both???

 

Thanks, Mike  

 

 

Type A.jpg

Link to comment
Share on other sites

I breadboard a similar circuit often when doing testing to enable easy changes in attenuation.  However, when I decide on the attenuation, I revert that circuit back to having the cap before the autotransformer.  I just would not feel safe leaving that large low resistance coil in there for the long term as a direct low resistance path to ground.  Thinking of course here of the chance that the amp could fail and put a high current DC supply across that autotransformer coil.  Now that can and does happen with the woofer circuit.  But in that case, generally the relatively small woofer voice coil opens petty quickly taking the path for current away.  The autotransformer with much larger wire will just continue to cook until something in the amp gives up.  Like I said, just can't get comfortable leaving that in the circuit long term and without me right there monitoring it.

 

Bob Crites

 

  • Like 1
Link to comment
Share on other sites

@BEC I once had an amplifier that sent DC to my loudspeakers, which caught on fire in my livingroom (yes, it was very exciting). So, it would seem that even if the capacitor is in its normal position, unless it has a voltage rating high enough to block the DC voltage from the amp - you are going to lose the loudspeaker anyways. Yes?

Link to comment
Share on other sites

Happens pretty often to the woofer circuit since that one has no cap in series.  Normally not for the other two drivers since they both normally are protected by the DC blocking ability of a cap.  And usually the woofer voice coil opens before the fire can get going really good.  But if you leave the cap out of the autotransformer circuit you have no such "fuse" like a woofer voice coil to save you.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...