CANT

Same thing realistically... nomenclature gets a bit funny at a point but the K52 motor was used with a threaded snout and with the the K701/K53, K601/K57, K602/K61/K62... it’s late, I forget how it all lines out completely but there are horn part #’s that mate to that motor and assy #’s that utilize the motor in one form or another?

Roy does not, to my current knowledge, endorsed the A55.

I’ve listen to a slew of 55 variants... including the SAHF and what was it... the EV 1823? 18something? They do all sound slightly different but I wouldn’t consider any of them an upgrade to a K52 generically... If you are looking to expose some bias I will gladly give it... I think anyone buying these stupid things as an upgrade is an absolute sucker. I mean if these were cheaper than the Atlas I might change my tune but right now I’m just seeing a lot of people paying good money for very little return, if any?

This is actually where I think we should be most careful... why exactly do Forum members feel like we can do better than the team of engineers Klipsch has on hand and the resources they have available?! Yes, they’re designing to an end point... likely keeping in mind price point among other things... but this plug and play upgrade mentality is completely glossing over a slew of other aspects of design.

That’s because the CII is balanced to the output of a 15” (high output) woofer and the FII is balanced to the output of a 12” woofer... in their respective cabinets?!? Again, there is a whole lot of apples to pineapples going on here?!?

Yeah but the FIII and the FII don’t use the same horn, driver and have dramatically different balancing networks... there is just a lot of assuming happening here... I mean I get the fun aspect. I love tearing sh!t apart and rebuilding it just to see how it works but I worry about what is being billed as equivalent or as an upgrade because those types of ideas seem to be spreading around recently with little vetting? The A55 itself is somehow billed all over the place as a generic upgrade to the driver of your choosing despite the fact that there is NO way that is realistic. There are numerous old threads that compare the K52 and K55 (of which the A55 is basically a clone)... and most, that I can recall, show the 55 down about 2-3dB and not realistically swappable without making adjustments to the network... but look at where we are?

The K604 has never been produced with mumps? It is just a K602 with a threaded driver mount rather than a mounting flange for a K52 driver/motor assy.

The horns you are comparing are not necessarily comparable... the stock Chorus II horn is a K60X (600Hz) series horn and the Forte III is a K70X (700Hz) series... technically the comparable current replacement would be the lager K603M found in the Cornwall IV or the KPT310HF. If I remember correctly the horn you are trying to replace is a K602? Between the A55G and smaller K703M horn all you are effectively doing by swapping out components is EQing the speaker to potentially suite your own taste? Why not just use an EQ? It would be easier?

I do not recall hearing/seeing anyone confirm it but it would make the most sense for it to be 8ohm...

The A55G didn't exist when I owned my KLF20's but I did throw a pair K55's in there just for sh!ts and giggles... it was different but I would not say it sounded or looked better. The thing to me is that the 55 and 52 excel at completely different things and I would not consider them interchangeable. For a Khorn, La Scala, Belle or maybe older Cornwalls I get it. There is a reason the K55 is used and I could understand the argument that an A55 might be better, though I don't buy it. For models that naturally come with the K52 I think the benefits of either 55 are lost on that model due to their inherent differences. And I can completely understand someone saying the A55 sounds better to them but adjusting the bass/treble might also sound better to that same person... so what does better mean?

7kHz is the approximate acoustical crossover point between the original midrange driver and the tweeter... neither came to a dead stop at that frequency? So despite the fact that the A55G doesn't go as high as the K52 there likely isn't a gap in response but there is no way to tell without taking a measurement. The K75/79 is generally spec'd to cross between 5-7kHz with little to no change in the tweeter circuit (i.e. Chorus I vs Chorus II). Also, the K75/79 should be good down to at least 2kHz if you wanted to change the crossover point for some reason? You would need add a low pass to the midrange as well as adjust the high pass for the tweeter though. If it were me I would just put the K52 back in?

I have used both the 904 and 942 networks with a 904HF/315LF setup. I'm terrible at describing this type of thing but to me the 904 sounded rounder/fuller and the 942 sounds faster/less bloated? Both 100% require a resistor pad to knock down the HF with my application since they were intended for the 904/940LF. I currently have a 4.5ohm resister on the positive input of the HF circuit... I personally found 5ohm was too much and 3.3ohm was not quite enough... I have thought of going down to 3.9/4ohm but I don't have that value on hand right now. I would think 1-2ohm would be all that is needed to take the edge off of a setup using the 904/940LF? I have also started playing around with an LCR placed between the HF circuit and the HF driver that is centered at about 1600-1700Hz... There was something going on there that appears to correspond with a small impedance spike found in the 904HF (DE 75-8P). My current values are 3mH - 2.7uF - 10ohm I think both networks have their positives/negatives but I have ultimately kept the 942 networks in place... for now?

Why not just use the actual 904 crossover design? or if you wanted you could use the KPT942... which replaces the 50uF with 75uF and the 4.7uF with 6uF (inductor values don't change). I don't have a pic of the schematic for the 942 but I do happen to have the physical network. The 942 was obviously intended to be used with a 402 and not a 510 but it crosses high enough (500-600Hz-ish) to potentially be used with the 510? Stock 904 crosses at 800Hz according to the spec sheet I have, always looked more like 900Hz-ish whenever I played around with it?

Do they have the little circular date stamp/mold on the top/bottom by the flange?

Sounds like they are the same as the 510? Could they be NOS leftover from a previous supplier kind of like the KL series horn tweeters that are on Parts Express???

If I remember correctly, the threaded insert in that assembly fits just about as perfect as can be in the hole left by the stock setup... I don't remember having to drill or modify anything.

I sold the pair ages ago but I replaced the feet on mine with... https://www.parts-express.com/dayton-audio-drfs1-1-3-8-x-1-heavy-duty-rubber-feet-4-pcs--240-712

My first guess would be the inductor value in the LF circuit

The KPT-904-M-B looks correct for the schematic I’ve seen... the KPT-904-M is some what confusing due to its use of the T10A autoformer? That’ll knock the HF down -9dB which seem crazy overkill for std 904 setup. I’ve also never seen a 904 use an autoformer???

Ok, so over time I have ended up with schematics for the 310, 942 & 904. I would still like info on the KPT325 if any one has one? I'm pretty sure it is identical to the 904 but has an additional resistor to pad the HF output a bit (2 or 3 ohms).

I saw your thread about that! I've been wanting to design an adapter that could be 3D printed to more-or-less to the same thing! I have had ZERO time to try and tackle that idea though...

Have you tried contacting Klipsch directly? An off the shelf comparable woofer would likely be cheaper but Klipsch does sell replacement parts for their speakers and the K48EP (121534) is used in current KPT models. And the K34 (a dressed up version of the K33 used in the CWII) would work in a pinch though if i remember correctly it is like 2dB less sensitive. The K48(4ohm)/K45(8ohm) are basically pro versions of the original K33(4ohm)... fundamentally I would consider them very similar, though being designed for pro lines, they are more sensitive and built to handle more power. Their wattage handling is not a function of their bass output however? In fact the K33, by design, actually has better low end response but that ability is of no use in the pro market where the 301 would likely never see signal below like 50Hz? I've attached an old scan of the spec sheet for the K1545/K1548 which might be of some help if you want to source a replacement from an aftermarket supplier? They early versions of the 45 & 48. Klipsch K-1545_K-1548.pdf

Not in person? In some photos of the older molds you can actually see where they filled in the notch/cutout for the woofer... P.Audio also makes the horn lense for the K107Ti/K100Ti/K771 They also supply several drivers such as the K68A/K701G/K71G used in the Reference & KP/KPT lines, the K70G used in the FIII & various KI/KPT models and the K69A used in various KPT models...

My guess is it is not. The K70G used in the Forte III is 8ohms. If they didn’t bother messing with the FIII I’m not sure why they would mess with the CWIV?

The thread insert is molded into both but the insert itself is slightly different... you have to remember these were likely made years apart, with the K704 being older, things change over time. I’ve personally seen 3 variants of the K703 ranging from the KLF/CF days to the more current applications. The mounting screw holes on the 2510 are slightly larger and tapered but I do not consider that much of a difference?