La Scala crossover upgrade options

[Axz Hout]

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[CECAA850]

I have Fastrac horns

If you have the" Eliptrac 400" and K55 driver what was stock?

I'm assuming a 90 x 40 exponential horn. This is new to me as are the speakers.

[CECAA850]

My other assumption was that the stock horns were not 400Hz horns.

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[CECAA850]

So you tried the tap 3 and 6.8uf cap and need more attenuation? The driver type and horn model need to be known if not a 400hz crossover and K55 driver.

I moved everything as Dean suggested in that thread. I also installed the 6.8uf cap. It IS a K55 on one of Daves 400Hz Fastrac horns.

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[CECAA850]

Thanks Chris.

Sorry as well for the thread intrusion.

[Guest David H]

I have Fastrac horns so the crossover point would be changed vs stock I'm assuming?

No need to change crossver settings with the Fastrac Lascala horn. As long as the K-55 is being used.

The Lascala horn has slightly less output than the K-400, around -1db therefore is a drop in replacement.

For use with the ALK Universal crossover I recommend taps 0-4 on the squawker.

Dave

Edited February 17, 2014 by GotHover

[CECAA850]

I have Fastrac horns so the crossover point would be changed vs stock I'm assuming?

No need to change crossver settings with the Fastrac Lascala horn. As long as the K-55 is being used.

The Lascala horn has slightly less output than the K-400, around -1db therefore is a drop in replacement.

For use with the ALK Universal crossover I recommend taps 0-4 on the squawker.

Dave

Would changing the crossover point as I've done increase the mids?

I'm using AA networks with Crites tweeters.

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[Tony L]

Sorry Tony L for jumping on your thread, welcome and just ask more questions. chris

It's all interesting stuff, many thanks.

So, to recap: if I went the Type A or Type A/4500 route I could drop the mid-horn output by changing the autoformer tap or something? If so that's very useful to know. I assume the 4500 crossover helps here as IIRC most of what the K55M adds in output over the V is at it's higher range?

Whilst I can't really read / understand circuit schematics comparing the Type A to the AL-3 it's clear there is a lot of different in both the bass and the tweeter sections, i.e. this is more than just a change relating to the then new K55M driver - it's clearly doing more than just altering the mid driver behaviour. Can anyone perhaps articulate what these changes are and how they alter the sound? Is the behaviour of the bass-horn obviously different between A and AL-3? What about the tweeter? Is that any cleaner sounding minus the protection stuff? Anyone got any subjective pointers e.g. which is more open sounding? Smoother? Which more weighty and clean in the bass etc?

[CECAA850]

So far you have not changed the crossover point, just the amount of attenuation.

I thought that's what the cap swap did. That's what I get for thinking.

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[Islander]

Tony L wrote:

They are at this point entirely stock and have K55M mids, K401 plastic mid-horns and AL-3 crossovers. I'm currently driving them with a Quad 303 power amp and a passive pre. I've also got a pair of BK XLS400DF 12” infinite baffle subs hooked up, I've got them crossing-over very low so they really only fill below about 60Hz or so.

The reason for this post is I'm looking to either refresh or replace the crossovers and I'm somewhat baffled by the options available and as to which are considered good with the various versions of the La Scala.

So far I'm enjoying the Klipsch as-is, my only real criticism is a bit of a ring / prominence in the upper-bass / lower-mid that seems to be coming from the bass-bin. I'm curious to establish if this is the crossover or the cab walls singing along. Swapping in the ALK Universals will probably tell me a lot here.

I've searched the archive but found little in the way of folk actually describing the subjective characteristics of these crossover options, how they compare and in which contexts they are applicable.

Many thanks,

Tony.

And I replied:

Tony, welcome to the forum!

The bass prominence you've noticed is a peak centred at 148 Hz. It's a consequence of the dimensions of the bass horn of the La Scala and La Scala II and is difficult to eliminate with a passive crossover. With the JubScala conversion, using the EV Dx38 electronic crossover, there's a narrow 7 dB cut in the crossover settings, which eliminates that bass peak.

On a related note, you might want to cross over your subs much higher. La Scalas' bass roll-off starts as high as 100 Hz. When you combine that with the top-end roll-off of the subs, you may get the smoothest bass response with the subs' hi-cut set as high as 120 or even 150 Hz. After extensive testing, I settled on the 150 Hz sub hi-cut because it gave the most even frequency response.

Filling in the mid-bass dip like that might also make the 148 Hz bass peak less noticeable.

Are La Scalas and other Heritage Series speakers easy to find in the UK? I had the impression that they were much more rare than they are on this side of the Atlantic.

Edited March 26, 2014 by Islander

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[Islander]

The fact that the bass peak is exactly the same with the La Scala II, with its much stiffer sidewalls, tells you it is not a vibration or stiffness issue.

If you're hearing some kind of resonance, stiffening the sidewalls may eliminate that, but it will not eliminate the narrow bass peak that's caused by the shape of the bass horn.

[Tony L]

The older crossovers came with a multi tap autoformer. The T2A, so yes one can use it to attenuate mids and tweeter output, a capacitor change is needed with each mid range step. Your AL-3 has a T4A fixed at -4dB, so no tinkering here. The T2A alows 3dB changes, autoformers with 1.5 dB or 1.0 dB steps are available as DIY.

The early crossovers A-AA etc have one inductor 2.5 mH for an easy 6dB slope, your AK-3 is a steeper 12dB design. Less overlap of bass and squaker output. The early speakers have different K33E woofers than yours,, square to round magnet with differerent design parameters.

The early tweeters were alnico T35/K77, yours are a different magnet on the same lense. To some a different sound and output level? Your ear to deside, Klipsch was keeping up with supply, alnico to ferrite. The protection is also different, but shouldn't change the sound just save voice coils. The A/4500 would need the recommended tweeter change. (different sounding)

I have a 1975 LaScala with the AA crossover, Klipsch offered (at my expense) updates to keep up with the latest production. I chose to leave it as is, only recently changing the capacitors.

The more I read here the more I'm starting to think maybe just refreshing the existing AL-3s might be the most sensible starting point, i.e. just buy one of Bob's kits for $110. That would give a fair indication as to what these speakers should sound like and let me know if anything is off spec (I'm sure the drivers are all fine). I'll get some of the mid-horn grommet things too.

The bass prominence you've noticed is a peak centred at 148 Hz. It's a consequence of the dimensions of the bass horn of the La Scala and La Scala II and is difficult to eliminate with a passive crossover. With the JubScala conversion, using the EV Dx38 electronic crossover, there's a narrow 7 dB cut in the crossover settings, which eliminates that bass peak.

On a related note, you might want to cross over your subs much higher. La Scalas' bass roll-off starts as high as 100 Hz. When you combine that with the top-end roll-off of the subs, you may get the smoothest bass response with the subs' hi-cut set as high as 120 or even 150 Hz. After extensive testing, I settled on the 150 Hz sub hi-cut because it gave the most even frequency response.

Filling in the mid-bass dip like that might also make the 148 Hz bass peak less noticeable.

Are La Scalas and other Heritage Series speakers easy to find in the UK? I had the impression that they were much more rare than they are on this side of the Atlantic.

That's interesting, I've just run some test-tones through quite quietly (it's late here) and it's rather different to what I though I was hearing, and yes, more a peak than a resonance. I've not had any luck crossing the subs over higher yet, I've just not managed to get them to blend right beyond the low range where they are nice and seamless. At present I only notice they are there on electronica and film soundtracks etc, hardly heard them at all on jazz etc.

Klipsch Heritage kit is very rare in the UK, very few about, even Heresys. I guess as speakers are big and cost a lot to ship they tend to stay close to where they were made. I get the impression a fair amount of Klipsch kit ended up in Germany in the 60s and 70s due to US military bases etc, but very little in the UK. So little it's actually really hard to establish a second hand value.

My LaScala did the same thing. As I posted above I added 2x3/4 in plywood to the bass bin. It does not ring/buzz anymore. I also add 1 pc 3/4 to the top, as it also vibrated more than I liked. No crossover changes, just one solid bass bin.

Nice job, though a bit adventurous for me. I'm also very reluctant to do anything non-reversable to these as I may well want to shift them on later - I've also got a pair of vintage 15" Tannoy Monitor Golds that I'm rather fond of, and I suspect a time will come when I have to make a decision (no issue at present, they are in different systems and rooms).

Another mechanical fix to the LaScala bass bin buzz is to place triangular wedges in the doghouse. These are sold (I think) on some internet site or DIY.

This was actually the factory suggestion. Many Pro bass bins use this fix.

I've seen that mod and it is tempting. Anyone got a link to whoever makes the parts? My woodworking skills is of the splinters, blood and swearing level.

Edited February 18, 2014 by Tony L

[Islander]

There are no ready-made bass horn wedges, because the size needed varies, due to small production variances in the size of the bass horn, so it's a measure-and-cut DIY procedure. Quite often, the left piece will be slightly different from the right piece in the same speaker.

EDIT: it seems that you can find ready-made wedges and templates, so I stand corrected. They do need to be individually fitted, though.

Edited March 26, 2014 by Islander

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