Wirrunna

What about an Aussie distributor - http://speakerbug.com.au/index.php?route=product/category&path=25_78, convert http://themoneyconverter.com/AUD/USD.aspx

7db on the squaker and 2db on the tweeter. I have 1990 K-Horns with a Bob Crites CT120 tweeters currently running DIY ALK Universal Crossovers, the AP12-350 (a 350 Hz crossover intended for the Klipschorn) and the 4,500Hz version of the squaker / tweeter crossover whose schematic I found in this thread along with Bob Crites 3136 auto transformers with swamping resistor powered by a NAD C725 BEE in a well damped 20' x 33' room. I recall reading somewhere that 6db was what ALK set his Universals to (please correct me if I'm wrong as I can't find that post now) and used that as a starting point for listening tests, settling on 7db. The tweeter sounded a bit hot so I made a rather crude but effective attenuator (http://www.sengpielaudio.com/calculator-Lpad.htm) starting with 2db and that sounded pretty good. I did some measuring using one of these http://www.parts-express.com/dayton-audio-imm-6-calibrated-measurement-microphone-for-tablets-iphone-ipad-and-android--390-810 and my Nexus 5X with https://sites.google.com/site/bofinit/audiotool To my surprise most of my listening is at sub 80db throughout the room.

jimjimbo, here is a link to testing of caps - http://www.laventure.net/tourist/caps.htm There are also some links, under the heading "Further Reading", to other capacitor tests.

Exactly - N-R used a low pass of 4.2mH and 110uF - http://www.northreadingeng.com/Klipschorn_notch/Notch_Filter.html

For the 54uF I'm using 2x25uF Dayton 1% + 2x2uF Sonicaps, for the caps in series with the tweeter I'm using Jantzen Superior Z caps, 2X1.5uF for the 3uF and 8.2 +1uF for the 9.2uF. The 3uF to ground in the squaker network is a 3uF sonicap. The coils are Litz where specified. Originally I built the network using Sonicaps and Jantzen air coils but changed to Litz coils (and couldn't hear any difference), but when I changed the Sonicaps to Jantzen Superior Zs I thought I could hear some difference with a very slight softening of the mids and highs. I have Superior Zs for the 54uF (2x22 + 10uF) but have not fitted them yet as they are the size of Coke cans and require almost a complete dis-assembly and and re-build of the network. I did play my K-Horns with an AK-3 in one and the Universal in the other but it wasn't until I played the Universal in both that the difference was really apparent. The notch filter calculator is fascinating, thank you for that link, I will have a bit more of a play before I commit to building.

Karlson, a thread on the AK-4 that mentions the improved bass due to the notch filter on the woofer.

Karlson, I have been toying with the idea of building one of the notch filters and using a Jantzen P-Core 8.2mH 17AWG 0.39 Ω inductor, based on looking at the reactance charts and noting that the difference is pretty minor and also I can get the 8.2mH at a good price. But first I want to move the crossover from the woofer chamber and mount it in the top hat. It is far easier to get at up in the top hat than in the woofer chamber. I did replace the AK-3 stock 4mH laminated steel with a Jantzen P-Core 4.7mH 15AWG 0.224 Ω that I unwound to 4mH and sheepishly confess that I couldn't hear any difference. However, I feel better and have told myself that the bass is tighter, has more thump and lots more air and that's before opening the windows! Here are two more threads for late night reading - in this one ALK details his Universal Crossover Network utilizing the AK-3 woofer and in this one shows the schematic for ALK's Universal modified for 4,500Hz After swapping in Bob Crites CT120 tweeters I built an ALK Universal at 4,500Hz utilising the AK-3 woofer network and have to say it sounds better than the AK-3 (re-capped with Sonicaps), better stereo imaging, greater sound stage depth and much less harshness in the mid range. I only play the system at low levels, rarely above 90db in a large well damped room.

Here is the thread - only limited discussion but the AK-4 schematic was posted in the thread and it has a similar notch filter, so how does the AK-4 bass sound compared to AK-3 ?

codewritinfool, after installing CT-120 tweeters from Bob Crites I recently swapped out my AK3 crossovers on my 1990 KHorns in favour of a home built ALK Universal at 4500Hz. I used the AP12 AK3 variant that utilises the AK3 woofer components. I too found the midrange harshness greatly reduced and also believe there is a better defined soundstage making it easier to locate instruments and performers. I only listen at soft levels, rarely do peaks exceed 90db on my sound level meter in a largish damped room.

Atomicthunk, here is a link to Bob Crites - http://www.critesspeakers.com/ This is your starting place for replacement caps and woofers.

I think a bunch of us will be interested in the continuing saga. I have just re-capped the AK-3 crossovers in my 1990 KHorns and then went on to replace the tweeters with Bob Crites CT120s. I have also built new ALK universal crossovers at 4500Hz to better utilise the CT120s. There is a wealth of information buried in this forum, here is an excellent comparison of crossovers -

Long time Squeezebox server user here, and yes, I have several Raspberry Pi players with the R Pi 7" screen running PiCorePlayer feeding a NAD 725BEE Receiver that drives my K-Horns. The DAC is a Chinese version of the Audiophonics I-Sabre ES9023 and sounds good. Back in 2005 I was looking for a way to digitise my CD collection and happened on this post https://hydrogenaud.io/index.php?PHPSESSID=9ojbvrbrk772kfub6qkmmuvs16&topic=38242.msg337788#msg337788 and have used Squeezebox servers ever since.

My googling on crossover evaluation for K-Horns has not come up with much other than - https://community.klipsch.com/index.php?/topic/146678-crossover-network-comparison/ which compares the crossovers in other heritage speakers.

Dean, a question on layout. I notice that you have used what I would call a daisy-chain earth. Back when I was building amplifiers a central earth point was mandatory otherwise there was hum and extra distortion, especially in class A amps and class AB amps that were operated at quiescent currents above 200ma. On my K-Horns the AK-3 crossover has a central earth plate. After updating the capacitors and adding a terminal block I retained the central earth system which certainly increased the wiring required and doesn't look as nice as a daisy chain earth along the terminal block. Is it because crossovers are essentially passive devices that central earthing is not required?

The capacitor being in series was discussed in a thread on the super AA - https://community.klipsch.com/index.php?/topic/65508-question-on-super-aa-crossover/

jimjimbo, the only idea I can offer is that piece of wood is to prevent warping of the top panel over time. As Zim says, remove the screws that hold the top panel on then it is easy to get at the insides. I have left the screws stuck to the K55 magnet for years as the top hat is a damn good hiding place for rarely used valuables (until some audiophile housebreaker recognizes what the 150lb corner furniture is).

jimjimbo, you are going to have to open that woofer hatch one day so I'm clearing the surprises out of the way. Mancave Man, thank you for your reply. What is the hatch seal made from and do you lie the bass bins down on their front when you open the hatch ?

Thank you for the schematic, I look forward to the layout.

Jason, I'm at the tail end of updating the caps on my AK-3 equipped 1990 K-Horns and am gathering the courage to open the woofer hatch. What type of gasket tape do you recommend ? - neoprene sponge, polyethylene foam, PVC foam - there are so many different types and your post is the first reference I have found to any type of gasket on the woofer hatch. Jimjimbo, I got a capacitor upgrade kit from Bob Crites and on his recommendation two gaskets for the K55 Horn and a barrier terminal strip so that the leads to the speakers didn't hang off the crossover components. Bob also recommended I replace the Monster cable leads as they may have deteriorated with age - he was being diplomatic, the cable had gone a clerpy green and the plastic insulation was sticky. And the results so far.... It's like the K-Horns had a thick blanket over them and someone just pulled it off ! Sparkling sound, better imaging - very different sound.

Dean, for completeness, may I suggest that you add a link to the AA schematic in your first post.