was a 1uF cap used in a Type AA "AB" style tweeter section?

[karlson3]

seems like it was 1uF ? - might have been a bit less - think it went as follows (?)

 

[Deang]

No 1uF in that network unless they were paralleling it with another 1uF to make a 2uF. There are three 2uF capacitors in the tweeter section of that network. 

[karlson3]

DJK mentioned that a long time ago - tried it once but did not take measurements

 

I added the 1uF to that drawing -  should have titled this  - - "AB Style Tweeter Section Mod" - can't remember if the value recommended was 1uF - or perhaps ~0.68uF ?

 

[JohnA]

A 1uF was not used in the original Type AA or AB networks. 

[karlson3]

thanks - its was DJK's acoustic Butterworth mod for the AA network tweeter section (with stock 2uF cap values) - I think the bridge cap was 1uf but not sure

 

[karlson3]

I think "this" is the general effect of using the bridging 1uF cap - possibly flatten

the passband and to create a notch around 3K5 .  A good measurement could be put

into Xsim to get more of the story.

 

In a Diyaudio thread, there's a comment saying the aB type behaves more like a 1st order highpass with a notch than 3rd order.  With an AA, it would be easy to try and switch be wired to jumper the cap when desired for comparison.  Apparently, KEF used theirs tuned to the resonance frequency of the tweeter.

 

[JohnA]

Two things: the K-77-M has a response hump in the 6 to 9k range and runs about 105 dB there.  The Type AA eq's the hump out and drops the output to match the rest of the speaker.  That hump is the ONLY thing I didn't like about Al K's Universal xovers.  The tweeter was just too hot. Mr. Paul was right.

[karlson3]

Thanks for the perspective ( - can't remember why DJK suggested the aB mod -?)

otherwise, did you like ALK's Universal better than an AA?  Where there two schemes? (I bought parts for one but might misplaced them )   I think my graph below is with Type A and mic height at K400's center

 

 

less smoothing

[Deang]

5 hours ago, JohnA said:

Two things: the K-77-M has a response hump in the 6 to 9k range and runs about 105 dB there.  The Type AA eq's the hump out and drops the output to match the rest of the speaker.  That hump is the ONLY thing I didn't like about Al K's Universal xovers.  The tweeter was just too hot. Mr. Paul was right.

 

All of the replacement tweeters that people are using also run on the high side through that area - so the AA works well for those too. 

[JohnA]

6 hours ago, karlson3 said:

Thanks for the perspective ( - can't remember why DJK suggested the aB mod -?)

otherwise, did you like ALK's Universal better than an AA?  Where there two schemes? (I bought parts for one but might misplaced them )   I think my graph below is with Type A and mic height at K400's center

 

 

 

 

I liked the ALKs a little better, but the tweeter was too much, plus Type AA Klipschorns were the ones I first heard and it is the sound I expect from Klipsch. 

 

BTW, that's a fine looking in room response curve!

[karlson3]

I wish my Khorns sounded as good as the graph - the walls are flexy and "boooommmm" - just when tapped with one's hand.   Maybe false corners are the only salvation for that room.