L-pad for tweeter level control?

[Deang]

So, you get a thing for free.

[Guest wdecho]

Heat pumps take heat out of the room in summer and take heat out of the outside air in winter. 

 

Dean we were just discussing not arguing. I knew an old man once,when I was young, that said he and his wife had never had an argument. But they have been known to wake up neighbors discussing some issue. 

[Deang]

34 minutes ago, wdecho said:

I still love him for his participation and advice for many years. He has been and still is an asset to the community. 

 

Thank you William, I appreciate that!

[rjp]

4 hours ago, Deang said:

Challenge accepted ...

 

Resistors turn energy into heat (waste).

 

Autotransformers turn nothing into something.

That's the good part about resistors. Any undesired signal  is turned into heat rather than coming out of the speakers. It is perfectly discarded forever.

 

Where does the extra treble energy go when the tweeter level is reduced by a transformer   
 

Back into the rest of the circuit.

[Marvel]

Back when I used to save darn near everything on here... ALK used to post a lot.

 

Here is a snippet that I would find relevant:

 

"A  resistor pad attenuator could  be  used,   but an autotransformer will allow  the  needed  attenuation without divorcing the amplifiers damping factor  from the speaker driver. This yields better frequency and transient response."

[rjp]

3 hours ago, wdecho said:

The only reason PWK favored an autotransformer in his networks because of the power savings.

 

I don't know how PWK felt about resistors in general, but in this particular article he shows that the resistor network (L-pad) attenuated the peaks less than the troughs in a frequency domain plot of the mid range horn he was using. He attributed this to higher order harmonics. The autotransformer attenuated them equally. This was why he chose the transformer over the resistor as I read it.

 

[pzannucci]

16 minutes ago, rjp said:

That's the good part about resistors. Any undesired signal  is turned into heat rather than coming out of the speakers. It is perfectly discarded forever.

 

Where does the extra treble energy go when the tweeter level is reduced by a transformer   
 

Back into the rest of the circuit.

Nope, there is a transformation going on 

Raise the impedance, lower the power.

[rjp]

3 minutes ago, Marvel said:

Back when I used to save darn near everything on here... ALK used to post a lot.

 

Here is a snippet that I would find relevant:

 

"A  resistor pad attenuator could  be  used,   but an autotransformer will allow  the  needed  attenuation without divorcing the amplifiers damping factor  from the speaker driver. This yields better frequency and transient response."

Yes, that is exactly correct. Any resistance in the output path interferes with the amp's ability to "hold" the speak exactly where it wants to (Damping factor).

 

If the amplifier itself has a very low output impedance (high damping factor) as in modern SS designs this will probably be more noticeable than an older tube amp I think.

[pzannucci]

7 minutes ago, rjp said:

 

I don't know how PWK felt about resistors in general, but in this particular article he shows that the resistor network (L-pad) attenuated the peaks less than the troughs in a frequency domain plot of the mid range horn he was using. He attributed this to higher order harmonics. The autotransformer attenuated them equally. This was why he chose the transformer over the resistor as I read it.

 

As I stated earlier, read up on voltage divider. They will change the response of the drivers in correlation to the impedance at those particular frequencies. 

[rjp]

???

Pzannucci, Did you read the PWK article Deang posted back on Page 5?

 

 

[pzannucci]

Probably a long time ago but it just makes sense if there is an impedance rise or fall on the driver will have some corresponding rise or fall in response due to voltage shifts in reference to the resistance of the resistor which is constant (supposed to be at least).

The autoformer will keep the impedance constant though at a multiple of the original.  If you look at https://critesspeakers.com/3636atz.pdf you will see the turns ratio to db.  Using an autoformer keeps the resultant waveform of the driver and impedance consistent, just modifying the value seen by the crossover.

[Deang]

 

6 hours ago, pzannucci said:

Nope, there is a transformation going on. 

 

Raise the impedance, lower the power.

 

There is no significant cost in electrical terms when you use an autoformer. You get to attenuate without increasing the power requirements from the amplifier (less insertion loss). Also, along with delivering less current, the amplifier is probably delivering less distortion.

 

You can also run them backwards.

 

Which brings us back to the heat pump. The outside air is cold, yet it generates heat. Some work down to 5 degrees. It does this without burning gas or oil, but by thermal transfer. It creates three times more heat energy than the electrical energy it consumes. It's the most efficient way of doing the work. 

 

A resistor works by using up power and wasting it in the form of heat. An autoformer performs the same function without doing either. It's the most efficient way of doing the work. 

 

It's not a good analogy, but I saw a parallel there. 

[Guest wdecho]

5 hours ago, Deang said:

A resistor works by using up power and wasting it in the form of heat. An autoformer performs the same function without doing either. It's the most efficient way of doing the work. 

 

 

We can agree on that statement Dean.  

 

That is the sole reason PWK chose the autotransformer over a L-pad arrangement for attenuation and it was an important point in the old days. Any other "discussion" about the advantages or disadvantages of L-pad "resistors" vs an autotransformer is just mostly a thorough waste of time. The majority of listeners will never be able to hear the difference between the two. 

 

The same can be said about a discrete resistor L-pad vs a the simple pot L-pad. Most will never hear a difference between the two. 

 

Any other discussion about either of these subjects will be more of a waste of time than anything else. I went to the trouble of spending the time building and testing the many different variations of circuits published using an autotransformer along with circuits just using resistors for attenuation. I can hear a difference between the two where others may not and I preferred a simple first order crossover vs one using an autotransformer. Klipsch now agrees ditching the autotransformer in all their speaker line. Along with all other speaker manufacturers. I am sure with the many extravagant prices some of the exotic speaker are selling for that if there were an advantage of an autotransformer over  just resistors for attenuation at least one would use an autotransformer. I do not know of one single builder of speakers that use an autotransformer.  

 

As far as discrete resistor L-pad vs pot L-pad there are technical differences between the two with the discrete resistor L-pad as being better but it would be a waste of time for most to go to the trouble of calculating a resistor L-pad when one can just buy two rotary L-pads and I doubt seriously 99.5% will never hear any difference between the two. I built the discrete one myself because I am an electronic hobbyist with plenty of retirement time to play. Most do not care about the technical differences and subtle differences in sound but only want to lower that irritating bright sound to be able to enjoy their music quickly and  cheaply and get on with their life. 

[Guest wdecho]

12 hours ago, Marvel said:

Back when I used to save darn near everything on here... ALK used to post a lot.

 

Here is a snippet that I would find relevant:

 

"A  resistor pad attenuator could  be  used,   but an autotransformer will allow  the  needed  attenuation without divorcing the amplifiers damping factor  from the speaker driver. This yields better frequency and transient response."

ALK is a seller of crossovers relying on the public that own the older line of Klipsch speakers that have an autotransformer in the crossover for his market. He goes into very lengthy articles describing his background and his theories and if you believe everything he writes everyone that has any other crossover but his is just ignorant. When I was building the many variations of crossovers that use an autotransformer I did prefer one of Al's "ALK" with the swamping resistor enabling the changing of attenuation. More versatile for tailoring the sound for your room. 

 

The great mathematician and grandmaster of chess Emanuel Lasker once stated he preferred chess over math formulas. If you have create a math formula solving a problem there is always someone else that will calculate another one claiming theirs is better. He said over the chess board he just checkmates them.   

[Marvel]

You're starting to sound like Al. 

 

You can do whatever you want, if it works for you,  great.

 

I'm out of this one.

 

[Guest wdecho]

26 minutes ago, Marvel said:

You're starting to sound like Al. 

 

Is this just personal or do you understand anything you just said. I have nothing to sell or gain from my post as Al does. Personal is the only reason for your post but that is OK, I'm a big boy. 

[Deang]

“ALK is a seller of crossovers relying on the public that own the older line of Klipsch speakers that have an autotransformer in the crossover for his market.”

 

That doesn’t mean he’s wrong regarding the effect on damping and transient response. I mean, both of those issues are pretty well known in loudspeaker design circles. 

 

Like I said earlier, he had initially planned on ditching the autoformer, but after testing, decided to incorporate it. It had nothing to do with marketing, but with test results. 

[Guest wdecho]

Total BS. A resistor does not change it's characteristics  whether it is on the input or output of the signal. If the damping factor and transient response is reduced by a few ohms on the outputs then all the speakers that Klipsch has sold since say 95 and all the other speakers that are being sold by anyone are also suffering and Al is right. There is anywhere between 20K and 300K of resistance on the audio signal before it ever gets to the crossover with no ill effects. Just because there is 1 to 4 ohms of attenuation at the output of the crossover has no audio effect on the signal. All it does is what every technician of every speaker manufacturer wants it to do. Reduce the signal ever so slightly. Everyone should use some common sense. I am not pushing to be correct but just trying to explain some simple electronic logic that is often ignored by sellers of any product. Dean I understand you use to build crossovers for Al and did a fantastic job and if someone is happy with a crossover using an autotransformer then I am surely not disputing that your crossover does not sound fantastic. But let's not get into fallacies. 

[pzannucci]

2 hours ago, wdecho said:

Total BS. A resistor does not change it's characteristics  whether it is on the input or output of the signal. If the damping factor and transient response is reduced by a few ohms on the outputs then all the speakers that Klipsch has sold since say 95 and all the other speakers that are being sold by anyone are also suffering and Al is right. There is anywhere between 20K and 300K of resistance on the audio signal before it ever gets to the crossover with no ill effects. Just because there is 1 to 4 ohms of attenuation at the output of the crossover has no audio effect on the signal. All it does is what every technician of every speaker manufacturer wants it to do. Reduce the signal ever so slightly. Everyone should use some common sense. I am not pushing to be correct but just trying to explain some simple electronic logic that is often ignored by sellers of any product. Dean I understand you use to build crossovers for Al and did a fantastic job and if someone is happy with a crossover using an autotransformer then I am surely not disputing that your crossover does not sound fantastic. But let's not get into fallacies. 

????  

[richieb]

 

--- although I have zero interest or knowledge of this topic I do glance at most of what happens around here. I propose the mods treat all future L-pad topics as they do with politics. Lock ''em down! I mean Jeez, 7+ pages on L-pads and half of those are arguments. Even the political threads are less toxic than this --- .