L-pad for tweeter level control?

[CECAA850]

3 minutes ago, pzannucci said:

Higher frequency is less of an issue with current.  The autoformer will allow for the impedance to not affect the flow / impedance variation at the driver.  Think about a voltage divider when you change the resistance up or down.  That shifts the voltage thus would have to shift the response using pure resistance.  Not to count the fact that the resistor dissipates power.  The autoformer keeps the impedance variation reasonably constant though multiplied or divided (depending how you look at it)

Mine are going on a squawker.  Where would the autoformer go?

[pzannucci]

3 minutes ago, CECAA850 said:

So if I understand correctly, I can use my L-pad to get the desired sound out of my speakers, remove them then measure one side, then the other and replace the L-pad with resistors of the measured values?

Theoretically though may not be 100% correct but maybe close enough.  Keep in mind your crossover needs to be designed to handle the end resultant impedance at crossover frequency.

[pzannucci]

An autoformer would go between the driver and the crossover.  Depending how you do it, as with Klipsch, they use the a cap before the autoformer and inductor after it, between the driver and autoformer.  This allows the cap to be much smaller and cheaper.  The inductor remains the same.

[pzannucci]

16 minutes ago, CECAA850 said:

Mine are going on a squawker.  Where would the autoformer go?

An autoformer would not be able to be inserted in line as it will multiply the impedance of the driver unless you used a swamping resister with it to get back to the original impedance.

[CECAA850]

7 minutes ago, pzannucci said:

An autoformer would not be able to be inserted in line as it will multiply the impedance of the driver unless you used a swamping resister with it to get back to the original impedance.

2 resistors it is then if and when I think it's necessary to replace the L-Pads.

[pzannucci]

7 minutes ago, CECAA850 said:

2 resistors it is then if and when I think it's necessary to replace the L-Pads.

Yes and get a Mills for the input resistor vs. a cheap sand cast.

[CECAA850]

I was planning on a mills but honestly, unless it sounds horrible, I'll probably stick with the pads.

[Deang]

"Friends don't let friends use resistors."  - Bob Crites

[Deang]

PK, who would typically try to find the least expensive way possible to accomplish an engineering solution - chose the most expensive solution possible for attenuation.

 

With that said ... 

 

... relatively inexpensive loudspeakers with simple networks should use simple solutions, if one wants some improvement. I'd rather see someone take a compromised short cut, and start saving for better loudspeakers.

 

Honest, just replacing the penny junk resistors and throw away capacitors will usually quiet things down considerably. Just file that in the strange but true department.

 

Resistors are not benign. Any series resistance will change the T/S parameters of the driver, and will also divorce damping between the amplifier and the driver.

 

The Trouble With Attenuators by PWK.pdf

[rjp]

3 hours ago, CECAA850 said:

So if I understand correctly, I can use my L-pad to get the desired sound out of my speakers, remove them then measure one side, then the other and replace the L-pad with resistors of the measured values?

Yes.

 

Interestingly, even this resulting network of two fixed resistors is still called an L-pad sometimes, which can be confusing.

[Deang]

Well, one is "fixed", and the other is variable, or a "rheostat". It's all so confusing!

[pzannucci]

Makes an L - what's so confusing 

[rjp]

1 hour ago, Deang said:

 

Resistors are not benign. Any series resistance will change the T/S parameters of the driver, and will also divorce damping between the amplifier and the driver.

 

The Trouble With Attenuators by PWK.pdf

 

Great read! 

[Guest wdecho]

1 hour ago, Deang said:

Resistors are not benign. Any series resistance will change the T/S parameters of the driver, and will also divorce damping between the amplifier and the driver.

 

 

I challenge anyone here to say what electronic component is less offensive than a resistor. It is just your basic first class electronic course info. The only thing less offensive is a straight piece of wire and if one is using a lab ohm meter you might find some resistance in a straight piece of wire. PWK preferred an autotransformer but it has far more offensive elements than a small amount of resistance but an autotransformer is more efficient with less power loss which did matter years ago when a lot of power from an amp was 5 watts. 

[pzannucci]

1 minute ago, rjp said:

 

Great read! 

The autoformer passes everything through (kind of) and in theory not impact the response due to the voltage divider function.

[Deang]

2 minutes ago, wdecho said:

I challenge anyone here to say what electronic component is less offensive than a resistor. It is just your basic first class electronic course info. The only thing less offensive is a straight piece of wire and if one is using a lab ohm meter you might find some resistance in a straight piece of wire. PWK preferred an autotransformer but it has far more offensive elements than a small amount of resistance but an autotransformer is more efficient with less power loss which did matter years ago when a lot of power from an amp was 5 watts. 

 

Says the guy who uses a five watt amp. :-)

[Guest wdecho]

1 minute ago, pzannucci said:

The autoformer passes everything through (kind of) and in theory not impact the response due to the voltage divider function.

You said that correctly, in theory but an autotransformer has inductance one has to deal with shifting the phase of the signal which is far more offensive to my ears. I have 2 pairs of autotransformer setting in a box some where. 

[Deang]

Challenge accepted ...

 

Resistors turn energy into heat (waste).

 

Autotransformers turn nothing into something.

[Guest wdecho]

1 minute ago, Deang said:

 

Says the guy who uses a five watt amp. :-)

I also have 300 watt per channel amps as well along with 2 or 3 100 watt A/B amps.  Statement still stands. 

[Guest wdecho]

6 minutes ago, Deang said:

Challenge accepted ...

 

Resistors turn energy into heat (waste).

 

Autotransformers turn nothing into something.

So you think an autotransformer is less offensive than some resistance. Nothing more needs to be said about that statement. Defy's the basic principles of electronics but you get that kind of statement on social media forums but never on technical forums. Two things come to mind that are serious side effects of an autotransformer, the inductance of the windings and the phase shift of the signal. A simple resistor has neither. Klipsch ditched the autotransformer years ago and as far as I am aware was the only speaker manufacturer that ever used them, many years ago. All modern Klipsch crossovers use resistors for attenuation but for some reason people here want to think they know more than electronic technicians making a living designing electronic circuits.