Something funny with these XO's

[Cal Weldon]

Rant hat on.

Opened up one of the 1233 boxes as there was a bit of trouble with one of the tweeters and lookie what I found. It appears someone in their infinite wisdom wanted to "fix" it. Perhaps there was a problem with the exisiting 6 mfd series cap. There are four extra Sprague caps in there . They are .033, .047, .047 and .068 mfd. for a grand total of .195 (all parallel) in series with the other 6 mfd cap after the the shunt coil.

I may not be the sharpest tool in the shed but for the life of me...

Any idea what might have been going on in their mind? There's near zero output from the 808 tweeter as you might expect.

WTF? Who does this and what were they thinking?

Rant hat off.

[Panomaniac]

I'll look again tomorrow after some rest. If someone else doesn't get it first.

[Cal Weldon]

Got some sleep friend, you've had a busy weekend.

Also, hope you can swing a deal with Tom re: the Altec gear. Are you planning to take the lot?

Cheers.

[Panomaniac]

Hey Cal, I looked again and can't tell what's going on.
You say the additional caps are in series (as a group). So are they in the shunt leg of the low pass filter? You say they are in series with the 6uF cap "after" the coil. That makes me think they are in the low pass circuit.

If they are indeed in the LP circuit, they won't effect the tweeter.

Can you draw up a quick sketch of the filter?

Sent Tom an email, waiting to hear. I'm interested in some horns. Should buy the whole lot, but probably will not.

[Cal Weldon]

Yes I can draw you something up. I think you will laugh.

I just went and pulled the other XO to find it has been attacked too. Again with incorrect parts, this time trying to make it a 3rd order. I think I will put it back to original with new goodies (sans coils) and take it from there.

Strange XO though. 2nd order with an 18 mfd cap on the woofer shunt and the cut off cap for the HF is 6 mfd. I might have thought those a little closer. Both coils are identical, just a big gap in the caps. Perhaps that was Altec's way of introducing a notch? hehe.

[bowtie427ss]

Perhaps that was Altec's way of introducing a notch? hehe.

I think this may well create a slightly rising HF response and was done to try to compensate for the rolled off response of the symbiotic drivers.

Here's a 1234 network which is even a little whackier:

[Cal Weldon]

Hi bowtie,

Is this what I am seeing? I guess they took a different approach with the 1233's

12 dB both halves, you seem to have 18 on the top.

[bfish]

Here's a 1234 network which is even a little whackier...

Yeah, I scratched my head raw on that one (not much effort required for that).

I finally shrugged and rationalized the intended app (stage monitor) and went with it. In all fairness, it's a great stage monitor.

[Panomaniac]

Thanks Cal. Thats 2nd order on the woofer, 3rd order on the tweeter. But weren't there resistors on that x-over? Your photo of the beast is gone, now.

What you have above looks normal, except for the lack of attenuating resistors. Oh, I see. That's a sketch of bowtie's circuit.