Lascala cabinet resonance

[Invidiosulus]

Yes, they resonate.

Bracing will help a lot but it won’t tame some of the irregularities in frequency response that are inherent to the LS due to compromises in the horn expansion.

 

if you have an active DSP setup that is capable of some parametric EQ adjustments, you can try the following settings that are known to ameliorate the response of the stock LS bass bin.

 

87hz, Q:3.5, +5dB
148Hz, Q:8, -7dB
380Hz, Q:5.5, +2dB

[Invidiosulus]

[Flevoman]

11 hours ago, mikebse2a3 said:

IMHO based on experiences having owned both the original La Scala model as well a the La Scala AL5 is that it is very important to pay attention to how we position the speaker relative to (SBIR) Speaker Boundary Interference Response and Room Modes.

Thank you Mike. As often, your assistance is thorough but also very technical 😉. Unfortunately, I still lack the technical insight to fully understand everything. However, I understand your explanation that the resonance I hear may not be from the speaker but due to its placement.

I've already tried moving the speakers around, and it hasn't had much impact on the resonance I hear. But next week, during my three-week vacation, I will experiment by placing the speakers lengthwise to see what effect it will have.

Thank you for pointing this out. 

 

6 hours ago, Chief bonehead said:

Known for its resonance?  Really?

Sorry, I can't tell if this is a dig or a well-intentioned wink. With my comment about the La Scala 1 being known for its resonance, I meant nothing negative, in any case.

[Flevoman]

2 hours ago, Invidiosulus said:

Yes, they resonate.

Bracing will help a lot but it won’t tame some of the irregularities in frequency response that are inherent to the LS due to compromises in the horn expansion.

 

if you have an active DSP setup that is capable of some parametric EQ adjustments, you can try the following settings that are known to ameliorate the response of the stock LS bass bin.

 

87hz, Q:3.5, +5dB
148Hz, Q:8, -7dB
380Hz, Q:5.5, +2dB

Maybe I didn't express myself clearly. I understand that every speaker resonates. I was just wondering if the resonance in the La Scala II / AL-5 is still significant enough to be a audible issue at certain frequencies, or if it should have truly disappeared by now. This was a common concern with the La Scala I, often addressed by using a wedge in the bass cabinet, if I recall correctly.

[Shakeydeal]

I see you didn’t answer my question to you regarding different amplifiers.

[Flevoman]

@Shakeydeal ahhh.. sorry, missed that one.

Yes, I have tried different amps (all tubes) and this gave some improvement. But the resonance can still be there with some songs. 

[Flevoman]

17 hours ago, Tom05 said:

If you  think resonance is a  problem , try clamping on a stiffener to the suspected area , like the outside horn edge for example ,  then  compare results , test tones will be helpful . This way you can see for yourself any positive change ,Good luck 🤓

I was thinking of using a wedge in the bass cabinet. But you're right, I could also secure a thick plank to the side of the bass cabinet with clamps. Logically, this should reduce the resonance (if indeed it's the bass cabinet I'm hearing) from the side walls.

[Invidiosulus]

6 hours ago, Flevoman said:

Thank you Mike. As often, your assistance is thorough but also very technical 😉. Unfortunately, I still lack the technical insight to fully understand everything. However, I understand your explanation that the resonance I hear may not be from the speaker but due to its placement.

I've already tried moving the speakers around, and it hasn't had much impact on the resonance I hear. But next week, during my three-week vacation, I will experiment by placing the speakers lengthwise to see what effect it will have.

Thank you for pointing this out. 

 

Sorry, I can't tell if this is a dig or a well-intentioned wink. With my comment about the La Scala 1 being known for its resonance, I meant nothing negative, in any case.

I might have said “known to resonate” instead of “known for its resonance”.

 

Can you feel the sidewall moving when you are hearing the issue?

On my LS 1 it would become very apparent on some songs and I could feel it with my hand quite easily.

As others have said, clamping some additional bracing in the outside of the cab is a cheap and reversible fix that you can easily test and back out of if you don’t think it helps.

 

the EQ setting I posted were specified by @Chief bonehead for folks using DSP when mounting the K510(I think) on top of the LS bass bin.

The sharp notch at 148Hz made a world of difference on my LS 1.

If you aren’t going active EQ then just concentrate on the rest of the equation regarding placement and room modes.

 

 

[Shakeydeal]

Just my opinion. The AL5 is the most improved LaScala, as it should be. I haven’t seen any mention of cabinet resonance in this version. I would say if this is something that bothers you, maybe it’s time to move on. It’s one thing to modify a 40 yr old speaker to suit your needs, but a brand new speaker will quickly lose any reasonable resale value after mods. If you can do something that is reversible and doesn’t show afterwards, maybe.

 

Again, just my opinion.

[KT88]

I find the whole article in the stereophile by Alex Halberstadt very worth reading.

https://www.stereophile.com/content/klipsch-la-scala-al5-loudspeaker

 

He has captured the essence of the LaScala and presented it very well. Incidentally, a very versatile author, even for non-audio topics, who was born in Russia and has a very German name.
https://muckrack.com/alex-halberstadt

I would summarise his article in stereophile together with my own listening impressions like this: Every speaker is a compromise. La scala is unconditionally designed to impress in order to create the highest level of lively music. Other aspects may not be as important, e.g. a neutral linear reproduction like a studio monitor, but the latter can also sound boring.
To come to the core topic of the thread. I'll start with my own experience. Firstly, I am referring to the vintage La Scala. In fact I have never heard the new models, AL5 and its predecessor as a two-piece construction.
In 1999 I had bought a La Scala from 1977, I have often written here about my endeavours to get La Scala to sound like I bought it in 1999. I don't want to repeat these steps here, you can find everything with the search function or via my profile.
Well, when the La Scala played for the first time in 1999 (in a different flat than today) I was completely delighted...and not only by the dynamics and liveliness, because I already knew that from another La Scala from 1996 at a friend's house. Rather, I was extremely impressed by the natural sound of my 1977 La Scala. It really was as if it had been cast from a single mould...something I had never experienced with a loudspeaker before in that trueness. I had only made two subtle changes that I had intuitively realised by trial and error...at that time I was not yet exchanging ideas in forums. Firstly, I had removed the magnetic screw from the coil of the tweeter. Secondly, I had deactivated the protective diodes. That was it...I loved the sound so much! Also at that time I had already tried various amps from my collection at the time, an Audion Silver Night 300B 7 Watt SET, a Leak Stereo 20 and Quad II tube monos with 15 Watt KT66 class A push pull. The Quad II produced the most stable and rounded sound, although only 15 watts but with a current delivery capacity equivalent to the torque of a V8 engine which I believe a La Scala deserves regardless its high sensitivity. I was happy to sacrifice the last subtleties of the resolution of the 300 B or the even livelier sound of the Leak stereo 20 without regret.

I still remember very clearly how my first music on the La Scala was a piece by George Benson, I was so shocked at how it was "a guitar", the homogeneity of the sound etc. I was reminded of how my own Gibson L5 Wes Montgomery sounds on my guitar amp. I wouldn't have thought it possible. By the way, distracting resonances were never an issue, I never felt disturbed, everything was coherent, with a wonderful bass that didn't lack any depth psychoacoustically. 

Now comes the less pleasant part. These La Scala had never been altered and were absolutely original until 1999. Unfortunately, the previous owner had tried to paint this birch plywood with a raw finish to match his wall unit.

 

I wanted my La Scala to look nice again and I took the cabinet without the driver to a professional carpenter to remove the paint, he promised me that he could remove the paint with a lye. I have already written about this here. But now it's relevant again in this thread.
At the end of the day, this carpenter couldn't get the paint off and without asking me! he sanded 0.6 mm off the side panels and the lid. I was very angry. Since then, I've been hearing resonances that weren't audible before. Because I had stored the La Scala for a very long time because I only listened to my UJ for so many years, now that I reactivated the La Scala three years ago, I will fight the resonances that were actually caused by the sanded side walls. Stage one, with the help of braces on the side panels, stage two, with a reinforcement of the side panels with a few layers of birch plywood.

 

@Flevoman, I don't think @mikebse2a3said that it was "only" due to the room set-up. He was reproducing what John Atkinson measured with his plastic tape, which is specially made for detecting structure-borne resonances. Yes, there are a few very low resonances with the MDF AL5 version.

If I understood Mike correctly, the La Scala can also excite room modes, especially because it is built deeper towards the rear than any other speaker. This means that the funnel opening of the La Scala can be located pretty much exactly in the room where the room modes are if you place the speakers fairly close to the front wall. That's why he suggests moving the speakers back and forth a bit to avoid the room modes.
Another point that I personally think is relevant. Many normal radiator speakers have resonances that usually have a small "Q" in the bass...i.e. a relatively soft rise in the frequency band. And...that they build up quite slowly and disappear slowly again. This means that resonances are present but not necessarily so disturbing even if loudly.
The resonances that you found somewhat annoying in the La Scalas very probably have a large "Q", not necessarily very loud, but they build up very quickly and disappear again very quickly. And with a very narrow-band freq range, if they are „horn born“. I believe that this falls into the area of different subjective perceptions, it bothers one person more than another. I would say that as far as I'm concerned, I didn't experience anything unpleasant like this with my 1977. I would rather say that it is part of the character of the speaker.  In contrast, the resonance of my side panels, which are too thin, is more of a broad, frequent nasty drone. 

 

The resonances you describe, Flevoman, are a point of subjective perception that I take very seriously. Either you get used to it, or you can fix it, or it could be that it bothers you more and more from week to week. Then all the positive attributes of the La Scala that are decisive for me personally won't help: being the smallest large speaker in the world. 

I bet your dilemma is that you would be very sad if La Scala were gone. I can only say that I personally believe that this whole low watts set fashion can amplify unpleasant peaks in connection with a bass weakness.

 

[Schu]

OP... what you should be asking is, does the doghouse shape act as a kind of Phase Plug for the low frequencies...

[OO1]

11 hours ago, Invidiosulus said:

 the picture above was taken when PWK was experimenting with the 200 wpc LSI speakers , the problem was that the LSI series used regular LS home cabinets   , while the LS cabinet was not originally designed to handle 2x the power rating in a commercial setting  .

 

-the picture also has nothing to do with the 100 wpc  LS for home use which did not resonate at the 50% lower power rating ,   while experimenting with braces PWK found out that add-on braces caused unwanted reflections in the LS1 bass bin , for that reason , PWK never approved the use of braces in an LS1 or LSI  bass bin 

 

- instead  , effective early 80's , a new LSI cabinet was released with beefed up panels to increase the performance of the LSI bass bin ,  these advances eventually trickled over to the new LS II series with 1 inch MDF .

 

here is an early 80's LSI cabinet with thicker plywood featuring rounded corners and rounded openings for the mids and tweeter horns 

 

 

 

 

 

 

 

Edited December 17, 2023 by OO1

[KT88]

34 minutes ago, OO1 said:

…while experimenting with braces PWK found out that add-on braces caused unwanted reflections in the LS1 bass bin , for that reason , PWK never approved the use of braces in an LS1 or LSI  bass bin 

Do you think that this type of braces could cause unwanted reflexions? May be with some reason at the upstream part in the back where the opening is still small, which could make sense.

 

Or is it more not to have used them about the issue that not all LS are identically built and there a one brace fits all has not worked? I will give such kind of braces a try in my sanded LS.

 

 

[Invidiosulus]

59 minutes ago, OO1 said:

 the picture above was taken when PWK was experimenting with the 200 wpc LSI speakers , the problem was that the LSI series used regular LS home cabinets   , while the LS cabinet was not originally designed to handle 2x the power rating in a commercial setting  .

 

-the picture also has nothing to do with the 100 wpc  LS for home use which did not resonate at the 50% lower power rating ,   while experimenting with braces PWK found out that add-on braces caused unwanted reflections in the LS1 bass bin , for that reason , PWK never approved the use of braces in an LS1 or LSI  bass bin 

 

- instead  , effective early 80's , a new LSI cabinet was released with beefed up panels to increase the performance of the LSI bass bin ,  these advances eventually trickled over to the new LS II series with 1 inch MDF .

 

here is an early 80's LSI cabinet with thicker plywood featuring rounded corners and rounded openings for the mids and tweeter horns 

 

 

 

 

 

 

 

I mean, the non expanding section of the horn in the LS design causes unwanted results in frequency response, yet here we are decades later still using that design.

 

It takes far less than 100 watts to excite the side walls in the original LS.

 

Of course the industrial models and the AL5 are going to resonate less, that’s just the way physics works.

 

The 1/2” back panel in the H1 is the same way. Bracing it or replacing it with a thicker panel improves the sound.

the newer models don’t have the same issue.

 

The original models were good but engineering and cost decisions were made that leave things less than perfect.

 

[billybob]

Guess that the resonance in the AL-5 is not in the realm of notice enough to have presented topics here to have had a following.

A bit of resonance to me was refreshing to me. Just my take and taste in the music listened to on my 84 LS.

[OO1]

2 hours ago, Invidiosulus said:

  engineering and cost decisions were made that leave things less than perfect.

 

  klipsch engineering had nothing to do with it  ,  the realities during the 70's and 80's warranted  cost cutting measures  across the entire industry as interest rates were over 20% .   yet ,  PWK still used fir plywood , BB ,   marine plywood  , copper plate badges ,  expensive grille fabric and veneer while the competition  used chip board , vinyl  ,  plastic grilles and badges  and cheap speaker fabric to cut their production costs  . if you ask me ,  klipsch engineering did pretty good 

 

 

[OO1]

4 hours ago, KT88 said:

Do you think that this type of braces could cause unwanted reflexions? 

  in an LS bass bin  ,   thicker panels must be all around including the panels of the dog house  in order to tame the resonance from the top+ bottom + the sides +the dog house , 2 horizontal braces cant replace all these panels  without causing unwanted reflections . 

[Invidiosulus]

1 minute ago, OO1 said:

  in an LS bass bin  ,   thicker panels must be all around including the panels of the dog house  in order to tame the resonance from the top-bottom + the sides +the dog house , 2 horizontal braces cant replace all these panels  without causing unwanted reflections . 

Do you have formation on the reflections and specifically what they caused?

[KT88]

11 minutes ago, OO1 said:

  in an LS bass bin  ,   thicker panels must be all around including the panels of the dog house  in order to tame the resonance from the top+ bottom + the sides +the dog house , 2 horizontal braces cant replace all these panels  without causing unwanted reflections . 

I was very happy with the sound of my vintage LS before they were sanded down on the outer side walls. So i see no reason why the panels of the doghouse and the bottom and top need to be reinforced. i'm only concerned with the sidewalls. if the braces don't do any good i'll reinforce the sidewalls with additional thin multiplex panels.

[Invidiosulus]

3 hours ago, KT88 said:

I was very happy with the sound of my vintage LS before they were sanded down on the outer side walls. So i see no reason why the panels of the doghouse and the bottom and top need to be reinforced. i'm only concerned with the sidewalls. if the braces don't do any good i'll reinforce the sidewalls with additional thin multiplex panels.

Randy is full of misinformation.

 

The top and bottom of the LS 

bass bin are adequately braced.

It is only the large side panels that are an issue on the LS 1.

Just like the 1/2” thick back panel on a Heresy 1, the side panels on an LS 1 will muddy the upper bass from its vibration if played at a louder volume.

my LS cabs were stock thickness 3/4” and the braces provided a noticeable difference in clarity.

Would I have gotten similar results from increasing the thickness of the sidewall?

Perhaps, but the braces were a cheap and easy install compared to increasing the sidewall thickness.