La Scala Woes

[Invidiosulus]

1 hour ago, jason str said:

I had a little propane soldering kit I used for years, just ran across it looking for something else. Sometimes electricity is not available and it's needed for sensitive work.

 

It's Butane, my apologies. Haven't used it in years.😀

Those are handy when you are working on a car out in the driveway.

[geoff.]

On 12/17/2021 at 8:37 PM, Desert Noises said:

I also installed an 80uF capacitor across the woofer terminals (parallel), and that seems to help cut some of it out. 

 

@Desert Noises, I was thinking of trying this on an, as yet unbuilt, pair of A/4500s.

 

From what little I think I know about crossovers each component causes a phase shift?

 

Did you need to, or should I, change any of the polarities to the drivers as a result of this? 

[RRR]

8 minutes ago, Invidiosulus said:

Those are handy when you are working on a car out in the driveway.

Soldering tools made airbags go off under certain circumstances I recall and yes electricity is not available everywhere.

[MookieStl]

3 hours ago, richieb said:

My LS sound nothing related to “boxy, nasal”,etc. etc. Might it have to do with excessive volume where the room is overloaded or under damped?
My Jubes and LS are positioned about 18 feet apart on centers, in a room about 26 feet back to front, I sit roughly in the middle of the room. Jubes are angled to cross at the back of the room and when the LS are brought in they are set directly in front of the Jubes, exact same crossing angle. Imaging is beyond reproach, no one would be able to say there is not a third speaker in the center (ghost speaker). Maybe I’m lucky with my setup or my hearing not as critical as others but the LS are every bit as enjoyable as Jubilees. The same presentation no, as enjoyable, yes.

My LS sound wonderful too. Not sure who is doing what wrong and/or  what I am accidentally doing right, but they sound great. Both sets and both sets of Belles. Enjoyable is the right word Riche!!!

[captainbeefheart]

3 hours ago, geoff. said:

From what little I think I know about crossovers each component causes a phase shift?

 

Capacitors and inductors have their voltage and current's 90° out of phase from each other. With a capacitor the current leads voltage and the opposite for an inductor.

 

Now the amount of phase shift will vary depending on reactance and frequency.

 

Take for example the 13uF capacitor on an AA network, the lower in frequency you go the more phase shift you will have. The higher in frequency you go phase shift will reach a point where it will be 0°. Reactance is also known as impedance, so the lower the impedance of the reactive element you get less signal is across the two terminals, where you get to the point the impedance is so low and for modeling AC terms behaves just like a wire you get the same potential across it between it's two leads, this is where 0° phase shift occurs.

 

The best way to view this would be at each driver output from the network and plot phase shift vs frequency. You will see the woofer will have greater phase shift as frequency increases and the tweeter network will have the most phase shift as frequency decreases. Mid-horn will have phase shift at both high and low frequencies and the least at middle frequencies.

[CECAA850]

6 hours ago, Crankysoldermeister said:

I should start doing everything with a propane torch.

8 ga wire baby.  Thats where its at.

[Deang]

That was some crazy stuff. I wonder where he went off to. 

[Desert Noises]

19 hours ago, geoff. said:

 

@Desert Noises, I was thinking of trying this on an, as yet unbuilt, pair of A/4500s.

 

From what little I think I know about crossovers each component causes a phase shift?

 

Did you need to, or should I, change any of the polarities to the drivers as a result of this? 

I'm not the right person to ask since I don't really know. Dean would be the one to ask. However, when I look at later crossover schematics, such as the AL models, which have the parallel capacitors across the woofer terminals, the polarities of all the drivers look the same as they do on the A and AA networks. As I understand it, the woofer is still a first order with the added capacitors. Again, Dean would be the guy to ask about this.

[mboxler]

41 minutes ago, Desert Noises said:

I'm not the right person to ask since I don't really know. Dean would be the one to ask. However, when I look at later crossover schematics, such as the AL models, which have the parallel capacitors across the woofer terminals, the polarities of all the drivers look the same as they do on the A and AA networks. As I understand it, the woofer is still a first order with the added capacitors. Again, Dean would be the guy to ask about this.

 

Not in Dean's league, but...

 

The parallel capacitor will always create a 2nd order electrical filter.  The size of the capacitor, however, dictates the frequency at which the slope starts to drop 12db per octave.

 

For a visual, I've attached the two different capacitors across the K33, simulated by a 6 ohm resistor.  Again, this is with the 2.5mh series inductor.  The top green plot is an 80uf capacitor, the middle a 40uf capacitor, and the bottom no capacitor.  As you can see, an 80uf capacitor creates an underdamped filter...the voltage across the K33 actually rises around 1.6db before falling.  Acoustically things will be different, but I thought this might help clarify how parallel capacitors affect a filter.

 

Mike

 

 

[Deang]

Lol. Well, I can’t do math and you can, so …

 

With every additional filter element you have to rotate your head 90 degrees. 

[Desert Noises]

2 hours ago, mboxler said:

 

Not in Dean's league, but...

 

The parallel capacitor will always create a 2nd order electrical filter.  The size of the capacitor, however, dictates the frequency at which the slope starts to drop 12db per octave.

 

For a visual, I've attached the two different capacitors across the K33, simulated by a 6 ohm resistor.  Again, this is with the 2.5mh series inductor.  The top green plot is an 80uf capacitor, the middle a 40uf capacitor, and the bottom no capacitor.  As you can see, an 80uf capacitor creates an underdamped filter...the voltage across the K33 actually rises around 1.6db before falling.  Acoustically things will be different, but I thought this might help clarify how parallel capacitors affect a filter.

 

Mike

 

 

Thanks for the explanation. That plot helps me visualize what effects the different capacitors have on the LF filter circuit. I have a lot to learn about crossovers, so I'm trying to expand my understanding. I notice on the AL-3 schematic that there are two 68uF capacitors in parallel across the woofer terminals, which would equal 136uF. Would you say that this instead of an 80uF would be adequately damped? What did Klipsch accomplish by adding these capacitors and increasing the inductor to 4mH?

[Tom05]

Lascala’s are fantastic speakers , but when you change drivers and crossovers and horns and whatever ,it starts getting  pretty hard to know what you may end up with. When you play a set of Lascala’s or Klipschorns you should immediately recognize that something special is going on .If not your room setup is probably wrong , they do require a decent size room, with   good acoustics, and they aren’t really for near field listening . That’s the way I see it anyway.🤓

[Curious_George]

3 hours ago, Desert Noises said:

Thanks for the explanation. That plot helps me visualize what effects the different capacitors have on the LF filter circuit. I have a lot to learn about crossovers, so I'm trying to expand my understanding. I notice on the AL-3 schematic that there are two 68uF capacitors in parallel across the woofer terminals, which would equal 136uF. Would you say that this instead of an 80uF would be adequately damped? What did Klipsch accomplish by adding these capacitors and increasing the inductor to 4mH?

 

The capacitor & inductor values will be different for various crossover alignments (Butterworth, Linkwitz-Riley, Bessel, Chebeshev, etc). The most common is Butterworth, but Linkwitz-Riley has been popular for awhile now. Choice of alignment has many variables. Some orders only offer one alignment, for example a 1st order can only be Butterworth. 

[mikebse2a3]

2 hours ago, Tom05 said:

Lascala’s are fantastic speakers , but when you change drivers and crossovers and horns and whatever ,it starts getting  pretty hard to know what you may end up with. When you play a set of Lascala’s or Klipschorns you should immediately recognize that something special is going on .If not your room setup is probably wrong , they do require a decent size room, with   good acoustics, and they aren’t really for near field listening . That’s the way I see it anyway.🤓

I like your thinking 👍🙂

 

miketn

[mboxler]

3 hours ago, Desert Noises said:

I have a lot to learn about crossovers, so I'm trying to expand my understanding.

 

You and me both.  Throw in an autoformer and things get really interesting!

 

It's all about resistors, capacitors, and inductors.  Once you understand each component's impedance and phase at a given frequency, then it's all about complex math and ohm's law.

 

 I'd go into much more detail, but I'm afraid I'd be going way off the rails.

 

Perhaps one should start a thread on the basics of passive filters? 

 

For example.  2.5mh inductor and a 6 ohm driver. 382hz 2.83 volt signal.  How can the voltage drop across both components be 2 volts?   There may be others that find the answer interesting.  Then again, maybe not.

 

Mike

[babadono]

11 minutes ago, mboxler said:

For example.  2.5mh inductor and a 6 ohm driver. 382hz 2.83 volt signal.  How can the voltage drop across both components be 2 volts? 

Its imaginary

Had a Prof in tech school that said if you think its imaginary grab unto this wire off this inductor.

[Deang]

https://www.northreadingeng.com/Klipschorn_model/basshorn_model.htm

 

http://northreadingengcom.ipage.com/Klipschorn_model_2/basshorn_model_partII.htm

[CECAA850]

On 12/19/2021 at 5:44 PM, Crankysoldermeister said:

That was some crazy stuff. I wonder where he went off to. 

Like the song goes, "you don't have to go home but you can't stay here ".

[captainbeefheart]

On 12/20/2021 at 6:00 PM, mboxler said:

For example.  2.5mh inductor and a 6 ohm driver. 382hz 2.83 volt signal.  How can the voltage drop across both components be 2 volts?   There may be others that find the answer interesting.  Then again, maybe not.

 

Because the 2.5mH and the 80uF LC tank circuit has a resonant frequency at 355Hz.

 

With the 40uF the resonant frequency is just past 500Hz which is why it doesn't show up on the plot, it's past the corner frequency.

 

Both inductor and capacitor are reactive, without getting into math and full explanations of each component at the resonant frequency if under damped (in this case) you will have the two store and release energy between each other. It's not imaginary either, ever unplug a fan while it's on? You usually see a large arc, this is from the inductive load trying to maintain the energy and as current drastically falls off from unplugging it the inductance releases energy in the form a very large voltage spike (far higher than the 120v input voltage) to maintain the same energy. Watts = volts*amps and so if amperage falls voltage will rise for the same given energy (watts). That's as simple as it can get for a definition without getting very in depth. This huge voltage spike has enough potential (probably over 1kV depending) which is why it can arc between the air gap when unplugging.

[Tom05]

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

I have a 1988 pair of La Scalas with two problems I'm trying to solve:boxy/stuffy bass and harsh midrange. Here's how they are configured:

 

Type A/4500 crossovers from Crites

CT120 Tweeters from Crites

Stock K-401 mid horn with the A-55-G drivers

Stock K-33-E woofers (also tried the Eminence Kappa 15C)

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.

SVS SB2000 sub crossed at 80 Hz near the right speaker

Amplification is from a fully restored/recapped Pioneer SX-1250

DAC for digital music is a Schiit Modi Uber

Turntable is Kenwood KD-750 with Audio-Technica VM540ML cartridge

 

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?

 

 

(Boxy/ stuffy). Lascala’s shouldn’t sound that way at all . I would turn off your subwoofer run your LS full range and see if it disappears . When running a subwoofer close to your mains you will get a coupling effect around the crossover frequency. If this is your problem move the subwoofer to the rear corner.