La Scala resonance problem

[muel]

I screwed mine from inside the bin.  Take off the bottom for access and you can tighten the screws on the woofer while you are there as well.  

[OO1]

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[Islander]

La Scalas do have a peak at 148 Hz.  The La Scala II, with its thicker and much stiffer MDF sidewalls, has the exact same peak as the original La Scala, which shows that the peak is not due to any resonance, it's due to the shape of the bass horn.  A longer and/or wider horn might be able to get rid of the peak, but then the speaker would no longer be its "portable" size, which means it would be less popular for PA use, and probably for home use, too.

 

As for resonances, they must occur at very high volume levels, since I've never heard them, with either my first-gen 1974 La Scalas, or my 2007 La Scala IIs.  The 148-Hz. peak can be addressed with EQ, either from a graphic or parametric equalizer, or from an active electronic crossover, like the E/V Dx38 or similar, as used with Jubilees, JubScalas, or JuBelles.

 

Bracing the sidewalls of an original La Scala may eliminate any resonances, but it will not have any effect on that pesky 148 Hz. peak, since they're not the cause of the peak.  In the design of the La Scala, it appears that gains made in other areas made the drawback of an upper bass/lower midrange peak worthwhile.  As engineers like to say, "There's absolutely no such thing as a free lunch."  Every gain in one area is accompanied by a loss in another area.  If the net result is an overall improvement, it's a compromise worth making.

[Dave A]

On 12/5/2018 at 11:49 PM, Islander said:

A longer and/or wider horn might be able to get rid of the peak, but then the speaker would no longer be its "portable" size, which means it would be less popular for PA use, and probably for home use, too.

Does Klipsch make an LSI version of the II? I have two old beater LSI sets from the late 70's here that toured with the Oak Ridge Boys and let me tell you that MDF probably would not have lasted a week. The days of the  La Scala for anything but living rooms is over unless they offer a pro real wood version.

 

  The birch plywood La Scalas did resonate and you could easily prove it by taking a set of pipe clamps and a couple of rags on the clamp feet to protect the wood and put pressure on the sides and the tone would clearly change for the better.

[ClaudeJ1]

On 12/6/2018 at 12:49 AM, Islander said:

La Scalas do have a peak at 148 Hz.  The La Scala II, with its thicker and much stiffer MDF sidewalls, has the exact same peak as the original La Scala, which shows that the peak is not due to any resonance, it's due to the shape of the bass horn.  A longer and/or wider horn might be able to get rid of the peak, but then the speaker would no longer be its "portable" size, which means it would be less popular for PA use, and probably for home use, too.

 

As for resonances, they must occur at very high volume levels, since I've never heard them, with either my first-gen 1974 La Scalas, or my 2007 La Scala IIs.  The 148-Hz. peak can be addressed with EQ, either from a graphic or parametric equalizer, or from an active electronic crossover, like the E-V Dx38 or similar, as used with Jubilees, JubScalas, or JuBelles.

 

Bracing the sidewalls of an original La Scala may eliminate any resonances, but it will not have any effect on that pesky 148 Hz. peak, since they're not the cause of the peak.  In the design of the La Scala, it appears that gains made in other areas made the drawback of an upper bass/lower midrange peak worthwhile.  As engineers like to say "There's absolutely no such thing as a free lunch."  Every gain in one area is accompanied by a loss in another area.  If the net result is an overall improvement, it's a compromise worth making.

a -7 db PEQ is all it takes to tame that nasty peak, which, of course, all folded bass horns have, more or less. My Quarter Pie Bass horn is not a bifurcated, folded, horn and is much smoother. This is why the most Parametric Equalization (PEQ) is required for the bass vs. the midrange or treble sections, which are straight axis.

[Islander]

On 12/9/2018 at 10:13 AM, Dave A said:

Does Klipsch make an LSI version of the II? I have two old beater LSI sets from the late 70's here that toured with the Oak Ridge Boys and let me tell you that MDF probably would not have lasted a week. The days of the  La Scala for anything but living rooms is over unless they offer a pro real wood version.

 

  The birch plywood La Scalas did resonate and you could easily prove it by taking a set of pipe clamps and a couple of rags on the clamp feet to protect the wood and put pressure on the sides and the tone would clearly change for the better.

 

It appears to me that the modern Klipsch Pro line is primarily aimed at cinema installations, rather than touring SR applications, so an Industrial LSI II may not be in the lineup for that reason.