La Scala Woes

[mboxler]

58 minutes ago, geoff. said:

 

I think I remember a post with ALK and BEC talking about how the AK-3 crossover was changed to use two 100uf capacitors paralleled across the woofer to tame it. Waaaay back. In it ALK said something to the effect that the La Scala crossover would benefit from the change as well.

 

It's actually two 50uf capacitors paralleled for a total of 100uf 🙂

[Deang]

Nitpicker. 

[sootshe]

“but that boxy “stuffy nose” bass sound was still there, obnoxious as ever.”

 

I think part of what you’re hearing is purely the sound of horn loaded bass from a LS.

Dont expect LS bass to sound warm or full. They have what I would call a “lean” bass sound. Snappy, forcefull, powerful.....sure, but they will never have the same bass tonality as a bass reflex or sealed box system. Not even the same as a K horn.

Even when you tame the side wall resonance & try anything else you like, you can’t change the basic sound signature of the cabinet design.

 

Just my 2 cents worth after spending time with Klipsch heritage & other famous vintage brands that shall remain nameless on this forum.

 

 

 

[mboxler]

8 minutes ago, Deang said:

Nitpicker. 

😎

[grindstone]

Is everybody talking about this?

 

[avguytx]

2 hours ago, geoff. said:

Has anyone figured out a passive correction for this 6db (?) peak at 148hz?

 

...bet it’s in the latest La Scala crossovers 

 

I think I remember a post with ALK and BEC talking about how the AK-3 crossover was changed to use two 100uf capacitors paralleled across the woofer to tame it. Waaaay back. In it ALK said something to the effect that the La Scala crossover would benefit from the change as well.

 

Here's a schematic for the trap filter I was going to use on my Belle clones....before I traded them off.  This may, or may not, work on the La Scala, as it was designed for the AB-3 crossovers that never made it into the Belle.   Not much money in parts to try, though.  

[mikebse2a3]

3 hours ago, Deang said:

Below is Kerry Geist’s response to the idea of adding the swamper. 

 

Wow is it 2016 again after reading some comments in a couple of current threads….

miketn😄

 

 

[Deang]

The best part of that page is my 11 year old daughter stealing my phone, lol. 

[Deang]

1 hour ago, sootshe said:

& other famous vintage brands that shall remain nameless on this forum.

Well, I’m using ATC these days. No apologies. 

[Deang]

https://electrical-engineering-portal.com/reactive-power-power-factor-correction
 

@captainbeefheart Dude, I didn’t even understand the pictures!

[mboxler]

2 hours ago, geoff. said:

...bet it’s in the latest La Scala crossovers 

 

 

It is interesting that Klipsch decided to not add a notch filter to the woofer circuit of the AL-4 as they did to the AK-4.  

 

 

[Deang]

The LaScala doesn’t have that massive bell curve to pull down. 
 

Newer model LaScalas are built like tanks with MDF - so not much in the way of shaking going on. 

[captainbeefheart]

1 hour ago, tigerwoodKhorns said:

Reactive power and correction. 

 

I remember this from engineering school (in the prior century).  This is going way back and I don't remember the specifics, but don't you fix a reactive load by adding a capacitor?  Something to do with the waves not aligning and it taking a lot of power to overcome this. 

 

 

 

 

Both capacitors and inductors are reactive loads, current and voltage are out of phase (I believe this is what you mean by the waves don't line up)  unlike with a resistive load where voltage and current are in phase and all the power from the source goes into the load. Theoretical perfect caps or inductors voltage and current are 90° out of phase but in the real world there is a loss angle (tangent) which complicates things further, they won't be exactly 90°.

 

Example with capacitors are:

 

loss angle = esr/reactance

 

 

Many have experience with this with electrical motors which are an inductive loads, this is probably what you remember because it is the most widely used example and you are correct you would use  capacitance to correct it. The opposite for a capacitive load where you would use an inductor to correct it. There are pros and cons to placing them in parallel or in series but for the most part you will almost always see a parallel approach, so placing a capacitor in parallel with an electric motor. A series example is with an amplifier and a capacitive load you will add an inductor in series with the output which you see many times in SS amplifiers.

 

For example my well pump is 3/4 HP and would pull 8.4 amps after it came up to speed, after adding a capacitor in parallel it now pulls 5 amps. The extra 3 amps was being wasted and didn't go into the load. I made the system more efficient and easier on the  source by increasing the power correction. The idea is you want your source (amplifier) to not waste power and also have an easier load to drive.

 

I won't even get into reactive loads changing phase margin of the amplifier. That's a whole different issue and topic.

[captainbeefheart]

Oh another great example that relates to audio is if you have ever heard of amplifiers that do not like or have even let the magic smoke out when paired with electrostatic speakers? It's because an ES speaker is for the most part a purely capacitive load and very difficult for many amplifiers to drive. When using ES speakers choose your amplifier wisely, many are not up to the task.

[Full Range]

My La Scala speakers were built by @sootshe 

And I did some modifications based on things I learnt building single driver cabinets for 30 + years 

 

My answer is 

Not all crossovers are created equal

The sum of the parts used is extremely important and great care should be taken in choosing 

Always take a holistic approach 

 

I spent lots of cash and used an existing crossover design but enhanced and encompasses two design principles 

 

To that end I have achieved near perfection 

 

This is the link to the whole process as it developed over time - if you have time to read it,  the schematic is on the last page 

 

 

[Deang]

Because of the low impedance at high frequencies. I mean, Martin Logan has one spec’d at a half ohm at 20kHz. We are not in that world - quite the opposite. 

[mikebse2a3]

On 12/7/2021 at 5:23 PM, Desert Noises said:

 

My woes with the La Scalas are as follows: 1) The upper bass sounds boxy, nasal-y and stuffy. 2) The midrange at higher volume (~90 dB) is just plain harsh and unpleasant. I reduce the 100 Hz tone control a bit and that alleviates the boxy/stuffiness to a degree. Meanwhile, I connect my home-built Cornwalls (Clonewalls) with B2 crossovers, K-55 mid, K-77 tweet, and Kappa 15C, and they sound amazing with no fatigue, even at higher volumes. Plus I get bass! Classical music commands a lifelike presence. I used to love the La Scalas before my recently built Cornwalls. Now that I can compare between the two, I vastly prefer the sound of the Cornwall. Am I missing something, or has anyone else had the same experience? I've been considering dropping the mid down 3 dB and changing the capacitor to 6.8 uF. Is there anything else I can try short of doing anything drastic like cutting wood?

 

When you compare do you swap the locations of the speakers with each other…?

 

On 12/7/2021 at 5:23 PM, Desert Noises said:

Room size is 16'x20' with high vaulted ceiling, floor carpeted, with La Scalas in corners along the 16' wall, toed in approx 20 deg.

 

I have La Scala AL5 and unfortunately a square room that creates a situation that sounds very similar  to what you have described. Moving the loudspeakers and listener location to minimize room mode issues is absolutely critical and just a few inches of adjustments can have dramatic improvements.

 

In acoustically small rooms the Room Modes from ~300Hz down dominate how we hear the loudspeakers. Even if you had a perfectly flat loudspeaker once it is installed in the room the listener can experience frequency SPL deviations of as much as 24db or more and ringing that severely mask detail, clarity and dynamic range perceptions so loudspeaker and listener locations are critical to find to minimize the negative effects of the room. The great thing is it cost nothing to experiment with Loudspeaker and Listener locations.

 

If your using subwoofers with your La Scalas then it is well worth experimenting moving them out from the corners (where all room modes are excited to the maximum) and even just a matter of a few inches of adjustments can make dramatic changes in the 100Hz region. If you can run frequency tones you can locate the locations of the peaks and dips of the worst offending modes and then locate the mouth of the La Scala LF horn in the dips (quietest locations as you listen and this will minimize the coupling for these modes.

 

By the way issues in the region below 100Hz can often lead to perceptions of high frequency issues and irritations which go away when the region around 100Hz and below are properly balanced and brought under control.

 

miketn 

 

 

 

[babadono]

On 12/14/2021 at 11:45 AM, captainbeefheart said:

This is how our hearing has evolved, we obviously naturally hear in nature a single ended, nonlinear distorted wave form and this has always been natural to us.

we hear single ended? what does that mean? can i google that?

[captainbeefheart]

1 hour ago, Deang said:

Because of the low impedance at high frequencies. I mean, Martin Logan has one spec’d at a half ohm at 20kHz. We are not in that world - quite the opposite. 

 

Of course we use inductive voice coils and the big difference being there is a straight resistance due to the DCR of the voice coil so it isn't just a purely reactive load like an ES panel. But in regard to the discussion an ES panel for the most part is a purely reactive load and capacitive by nature which is not how the majority of amplifiers are designed to power.

 

Besides the voice coil inductance and DCR,  the passive filters in the crossovers are still in the circuit and make the load even more difficult for the amplifier.

 

I know it's a tough habit to break but with AC and reactive elements you cannot strictly think in terms of only voltage,current, and resistance like you would with DC. Adding another vector makes things interesting 😜

[captainbeefheart]

More stuff to think about if we haven't enough to think about already.

 

With our Klipsch speakers that are inductive voice coils, the DCR will take over at low frequencies but the series inductance at high frequencies will cause increase of impedance which you would think is easier for the amplifier right? Well I would say less than 5% of the people are running fully open loop amplifiers, probably less than 1% really. With negative feedback (like amps the 99% of us use) as loading becomes easier (higher impedance) open loop gain increases, when open loop gain increases so doesn't the amount of negative feedback which in turn reduces the amplifiers phase margin to the point of instability.

 

I hate blanket statements but the flatter the load on the amplifier (pure resistance) the better the results.