Type AA plus K-55M/K-77M = Sibilance?

[Klipschguy]

1981 Klipschorns came bone stock with the K33E, K55V (dual phase plug), K77M, and AA crossovers. Mine sound very smooth and well balanced without even a scintilla of sibilance.   In fact, if anything the tweeter sounds very slightly recessed in the mix (big room, hardwood floors, high ceilings). My Cornwalls (in a different room) sound a tad brighter yet they have the K77 alnico tweeters with the B network.
 

As you know, room differences can make a big difference in frequency response.  I have a grand piano in a smaller room that did not sound its best, so I used a number of room treatments including drapes, an acoustic panel, and a rug; it took a little experimenting but the room went from pretty bad to great. My piano tech liked the results very much and commented “it is better to treat the room rather than the piano.”

 

Respectfully,

 

Andy

[mboxler]

1 hour ago, Klipschguy said:

1981 Klipschorns came bone stock with the K33E, K55V (dual phase plug), K77M, and AA crossovers. Mine sound very smooth and well balanced without even a scintilla of sibilance.   In fact, if anything the tweeter sounds very slightly recessed in the mix (big room, hardwood floors, high ceilings). My Cornwalls (in a different room) sound a tad brighter yet they have the K77 alnico tweeters with the B network.
 

As you know, room differences can make a big difference in frequency response.  I have a grand piano in a smaller room that did not sound its best, so I used a number of room treatments including drapes, an acoustic panel, and a rug; it took a little experimenting but the room went from pretty bad to great. My piano tech liked the results very much and commented “it is better to treat the room rather than the piano.”

 

Respectfully,

 

Andy

 

Thanks, Andy

 

That kinda blows my theory out the window.  I'm very tempted to buy a pair of alnico K77's just to see what's going on. 

[Klipschguy]

Keep us posted. I am always interested to hear the results of these quests. 

[geoff.]

@mboxler, what tweeters are you used to listening to in your La Scalas(?)?

 

Within the past couple of months I built a pair of polyester capped AAs as a reference to compare other crossover builds to.

 

I am trying to assemble a second set of La Scalas to loan out to friends and family so they can see what the fuss is all about. Trying to keep it as close to original as possible, but after listening to aftermarket tweeters for years now I couldn’t get the K-77Ms to sound right either.

 

 

[mboxler]

4 minutes ago, geoff. said:

@mboxler, what tweeters are you used to listening to in your La Scalas(?)?

 

Within the past couple of months I built a pair of polyester capped AAs as a reference to compare other crossover builds to.

 

I am trying to assemble a second set of La Scalas to loan out to friends and family so they can see what the fuss is all about. Trying to keep it as close to original as possible, but after listening to aftermarket tweeters for years now I couldn’t get the K-77Ms to sound right either.

 

 

 

They are Khorns 🙂, but I've been listening to CT-125's.  They are at least 6db quieter than the K77M.

[mark1101]

There are lots of K77V tweeters out there.  But I'd be careful.  As I stated I tried to restore my lascalas to original and wound up with several mismatched and poor performing alnico tweeters.  Especially, poor extension !!   So I eventually bought K77X, a new known good matched pair.

 

I agree though that the OP has a good point about the AA and K77M........not a good match.

[Marvel]

On 2/5/2023 at 6:55 PM, mboxler said:

They are Khorns 🙂, but I've been listening to CT-125's.  They are at least 6db quieter than the K77M

My ears liked the sound of the CT-125s better than the K-77s on my first pair of LS. My second pair only came with the cabinets, so I continued to use them. DJK said (opinion of course and I don't know which version) the k-77 was more tizz than music up top.

[winglet]

3 hours ago, mark1101 said:

I agree though that the OP has a good point about the AA and K77M........not a good match.

Did Klipsch install different versions of the AA network?  I've seen a schematic on here somewhere that shows the AA with a .35mh inductor between the autoformer and the squawker that starts to roll off the mid around 5khz..

Edited February 6, 2023 by winglet

[Deang]

The .35mH in series with the K-55 is a modification. 
 

Anyway …

 

https://community.klipsch.com/index.php?/topic/22418-k-77-vrs-k77m-qs/&_fromLogin=1

 

[Invidiosulus]

On 2/1/2023 at 12:41 PM, mboxler said:

 

Thanks for the kind words.  Your post is a great seqway to another measurement I took this morning (sorry Dean 😎).

 

Without a zobel across the K33E, there's really no way to achieve a classic first order 6db per octave low pass.  The inductance of the voice coil continuously raises the impedance of the woofer as frequency increases.  With a series 2.5mh inductor, the result electrically is a much flatter transfer function (blue plot).  Then there's the SPL itself.  Even without an inductor, the SPL drops dramatically after 180hz.  In my room, with a 2.5mh series inductor, the SPL is down around 12db at 400hz (green plot).  I believe this creates my dip in frequency response between 160 and 410hz???

 

Mike

 

 

Isn’t the mass rolloff frequency on a K33 typically around 180Hz?

[mboxler]

2 hours ago, Invidiosulus said:

Isn’t the mass roll off frequency on a K33 typically around 180Hz?

 

Looks like it.  I'm playing with a severely underdamped filter consisting of a series 1.2mh inductor and 245uh worth of capacitance across the K33E.  Seems to create a much flatter response up to 400hz compared to no filter at all.