Are ALK x-overs that good?

[SOUNDJUNKIE]

I'll have to give 'em a look-see when they arrive. Are there schematics posted somewhere on this site of the Chorus II networks? I'd much rather see the darn thing on some vellum before doing the 10m swan, yunno...just to make sure the pool's full!

[Klipschguy]

Can anyone give a description to the sound improvement in the Cornwall using the ALK's? Any descriptive terms would be highly appreciated.

Al,

As a tinkering kind of guy, I'm seriously considering building a pair of your ALK crossovers for my Cornwalls. If, at my own risk, I wanted to use a 600Hz crossover point (in lieu of 750Hz) between the woofer and squawker, would I just simply need to change the two 39uF caps and two 1.3mH inductors to 47uF and 1.5mH, respectively?

Thanks,

Andy

[Klipschguy]

Al,

Sorry, one more question. Are super low resistance iron core inductors good in the woofer/mid crossover point? Those "Super Q" iron core iductors from Parts Express only have a .124 Ohm resistance for a 1.5mH inductor - much lower than any of the air cores. (Note: I intend to use Hepta-Litz where indicated in the other parts of the crossovers.)

Thanks again,

Andy

[SOUNDJUNKIE]

I guess the big question would be does the middriver/horn support that crossover point? Who is the resident expert on where the Cornwall I middriver/horn starts to roll off? Moderators?

[GaryA]

Thanks for all the replys folks. My LaScala's have the AA crossovers. The nice fellow I purchased them from yesterday said he bought them new in 1986. Serial# 25U552&25U553, I've been trying the link to check mfg date without any luck. Does nyone know when these were made?

Also, I'm interested in making my own x-overs like Al's but not sure if I'm adept enough to do it. How hard is this and where would you get parts to do it? Al, approx what's the investment on a pair of your x-overs for the Scala? Thanks again for the feedback, Gary.

[SOUNDJUNKIE]

Am I reading this right guys?...25th week of 1980? Has my decoder ring lost it's lustre?

[Klipschguy]

Soundjunkie,

The stock crossover points in the Klipsch Cornwalls are 600Hz and 6000Hz for the squawkers and tweeters, respectively. BTW, the horn lense for the Cornwall mid is called a "K600" (Belle uses a K500, Khorn + La Scala use a K400, Heresy uses a K700). Obviously, the numerical portion refers to the low frequency cut off point of the horn. Also, my in room response testing shows no hole in the woofer/mid transition at 600Hz with the stock networks.

My question to Al is more about the dynamic nature of the crossover itself (also want to know about those Super Q inductors).

Warmest regards to all,

Andy

[GaryA]

Klipschguy, that would probably be right as I was thinking that AA x-overs were not used in Scalas much later than around 1980 according to other posts I've read. Thanks Gary.

This message has been edited by GaryA on 03-11-2002 at 08:26 PM

[SOUNDJUNKIE]

Klipschguy, Thanks very much for that info. I am just getting into this, head first of course, and hadn't seen those designations before, even on the BB's. I've been strictly working off of the cutsheets up until this point. This is the point that is a bit confusing to me, the "cutoff freq" for the K-600 horn used on the Cornwall(I?) is 600Hz & the cutsheet says the "crossover freq" is 600Hz...I assumed from this that the network cutoff to the MF was set at 600Hz to match the natural cutoff for the horn at 600Hz thus using as much of the middriver range as possible, making the midband as seamless as possible. What confused me was the post earlier where you wanted to move the crossover(network) point from 750 to 600? What are the horn designations used on the Cornwall, Chorus & Forte II's?

This message has been edited by SOUNDJUNKIE on 03-11-2002 at 09:49 PM

[Klipschguy]

Soundjunkie,

Al Klappenberger chose to use a 750Hz crossover point in lieu of the stock 600Hz point in his custom crossover designs - which is what I was referring to in my earlier post. I assume his design uses a higher crossover point to make sure the mid horn is operating well within its range.

Regards,

Andy

[SOUNDJUNKIE]

Andy, now it is perfectly clear. I was starting to question even my limited knowledge of the Klipsch product AND my EE skills. Mike

This message has been edited by SOUNDJUNKIE on 03-11-2002 at 10:50 PM

[Al Klappenberger]

Hi guys,

I see this is turning into a hot topic!

The values you mentioned for a 600 Hz crossover are pretty close. Just

multiply each part value by the ratio of 750 / 600 = 1.25. That gives 58 uFd

and 1.62 mHy. Get as close to these values as you can. In the case of the

little inductor connected across the transformer, round it up in value not

down. The inductance of the transformer actually reduces its effective value

slightly. The two are connected in parallel.

The 750 Hz crossover gives you better power handeling capabiltiy and better

dispersion. A 15 inch woofer will go up in frequency a lot easier then a

little horn will go down. There's isn't much of a difference between 600 and

750 Hz though and I am NOT going to say PWK was wrong by making it 600 Hz!

About iron core inductors, yes they have lower DC resistance because the

core makes more inductance with less wire. The problem with iron core

inductors is that they actually change their value with the level of voltage

that is applied to them! Air core inductors simply sound better. Even the

autotransformer used to cut the squawker and tweeter level down suffers from

this effect. In this case though, it's value is so high that it doesn't

matter. It's value is not part of the action. It's also swamped with a nice

stable air core 1.3 mHy inductor to keep it stable in the Cornwall design.

Al K.

This message has been edited by Al Klappenberger on 03-12-2002 at 05:41 PM

[JohnA]

Let's confuse things further! The horn cut-off for the K-400 is actually 263 Hz according the an AES paper published by Mr. Pual. I'll bet the others perform in a similar way.

John

[SOUNDJUNKIE]

Yes, that does stir the poo-poo a bit. That's a good thing, right? John, is that pub on-line and do you have a URL for it? Mike

This message has been edited by SOUNDJUNKIE on 03-12-2002 at 05:11 PM

[Klipschguy]

Al,

Thank you for the prompt, clear reply. I'll steer clear of the iron cores. Also, I used your ratio calculation and came up with 1.6mH and 48.8uF for 600Hz crossover point. (I realize that's what you meant).

Great reviews on your ALKENG designs from this rather discriminating bunch. I'm pretty eager to get started.

For me, wiring up a crossover in my shop on a lazy Sunday afternoon is SERIOUS relaxation (man, you should see me when I get out the ole Knight tube tester - like an "out of body" experience).

John,

Did Paul ever say how low the K600 would go????????

Warmest Klipsch regards to all,

Andy