Jump to content
The Klipsch Audio Community
Sign in to follow this  
John Warren

New hardware

Recommended Posts

However, the impedance of the low pass is not static, but dynamic - it's reactive and going all over the place. Then we have the effects of power and thermal compression -- any numbers derived during test conditions go out the window under a real load over any extended period of time.

 

I don't know what book he found this information in since he had no equipment, other then a soldering iron and an LCR meter, when he was picking my brain.  Anyhow, here is how you might measure it and IT is what casues the woofer filter to be rough, NOT the filter itself.

 

The woofer under test is a REAL Klipsch K33 driver from the 1970s era. It's one like in my Belle Klipsch. It's mounted in a particle board box having roughly the volume of a Klipschorn back chamber. The slot and the blocks were adjusted to nearly match the complex impedance measured on one of my Belles earlier.  The microphone is a Bruel & Kjaer 4134 pressure microphone designated for 90 degree incidence. It's mounted under the box near the slot for measuring the actual performance of a crossover network by a mathematical subtraction method I'll explain later.

 

Somebody here likes polar plots, so I will use the HP 3563 analyser Nyquist plot in addition to the rectangular R +-jX plots I usually use to display the K33 impedance. The Smith chart is not so good for showing the impedance of a stand alone entity as it relates its impedance to a system impedance, that is, the impedance of a filter designed for that system impedance.

 

The plots were downloaded from the analyser [PLOT] function using my own software over the HPIB bus to a DOS computer. It was plotted with an HP 7470A plotter emulator to get it into graphic form.

All the plots from the analyser need to be multiplied by 10 as my impedance bridge uses a 10 Ohm internal standard resistor.

 

The results show how bad a load a real woofer driver is to a filter. It's impedance is all over the place! In order to correctly model this weird load, the PCFILT analysis section was expanded to read impedance data form a file and use it as a parallel element at the termination. More about that later.

post-835-0-14100000-1445693188_thumb.jpg

Share this post


Link to post
Share on other sites

Now I can get to the point.  

The microphone mounted under the K33 woofer box is used to measure the actual performance of a network woofer filter by subtracting the response of the woofer itself from the response with the network filter in the signal path. I have found an easier way to measure the performance of the lowpass directly without the microphone though. I do that with every network I build. This audio difference method proves the other simpler method is valid.

Raw data from the analyzer can be downloaded through the HPIB buss just as its plots. It simply requires different software. The plots are in HP graphics language (HPGL). The raw response data is in real and imaginary pairs for each for 800 frequency points. Using this raw data allowed me to write software that allows me to calculate anything I want from the data and convert it to HPGL format.

The plots attached show the response plots for the woofer box with and withOUT the ES300 lowpass in the signal path. The ES300 is simply the latest network I built. It's a one-off I don't expect to ever build again. It was available to illustrate the process.

The bottom plot is the difference between the two plots from the microphone. It is the response of the lowpass filter using a real K33 as a load.

The top plot of the attachment is the PCFILT simulation of the ES300 lowpass using impedance data downloaded from the K33 box via the HPIB buss. It's close enough!

I might add here that I have done a lot of experimenting trying to find a way to smooth out this rough response. I can't, not even with the classic R-C Zobel network! It's only +-3 dB or so which is why it is really not significant. Every network lowpass I have analysed, both mine and those by Klipsch, have the very same problem. We are STUCK WITH IT!


 

post-835-0-68700000-1445697790_thumb.jpg

Edited by Al Klappenberger

Share this post


Link to post
Share on other sites

Just for kicks, here's the ES300 lowpass as measured using the other simpler method. It's real easy to do, you just ......

On second thought, I better let a certain Piled High and Deep engineer reverse-engineer the procedure!

 


Al K.

post-835-0-33020000-1445700041_thumb.jpg

Share this post


Link to post
Share on other sites

one question... DOES IT SOUND GOOD?

 

pretty simple.

Share this post


Link to post
Share on other sites

This has gotten BORING!! You guys that sell these "networks" need to just list your website and go there. GEESH!

 

This.

Share this post


Link to post
Share on other sites

This has gotten BORING!! You guys that sell these "networks" need to just list your website and go there. GEESH!

 

While I think like in any online debate some posts are more interesting and useful than others, some posts are largely being made to score points.  On the other hand, I do enjoy the passion that envelopes the whole debate and is one of the things that attract me to this forum and the personalities represented here. I assume most of us here have a passion for music-though that sometimes gets lost in the details. Just my thoughts, others mileage will vary.

Share this post


Link to post
Share on other sites

I think "all" these guys do really good work and the forum benefits from their knowledge.

Now there seems to be some resentment  and anger from some.

Life's too short to carry on a feud.

People that want after market parts and services will seek out these guys and get a good product

regardless of who is mad at who. 

Isn't it time to quit picking at each other---pick pick pick--You're gonna get a scab.

Share this post


Link to post
Share on other sites

I agree, I think Lee and I have accomplished what we intended to do, debunk some snake-oil.  Once this thread has run out of gass I plan to retire back to oblivion where I came from.  It's entirely up to how much more techno double-talk gets put up.  There is simply nobody else around here to do it. 

 

BTW: I sure wish I knew how to spell!  :sad:

 

Al K.

Share this post


Link to post
Share on other sites

Neither one of you are capable of carrying on any kind of discussion. One just wants to hurl insults and the other just wants to pontificate.

  • Like 2

Share this post


Link to post
Share on other sites

I'm glad I was able to make peace--Today

Share this post


Link to post
Share on other sites

I agree, I think Lee and I have accomplished what we intended to do, debunk some snake-oil.  Once this thread has run out of gass I plan to retire back to oblivion where I came from.  It's entirely up to how much more techno double-talk gets put up.  There is simply nobody else around here to do it. 

 

BTW: I sure wish I knew how to spell!  :sad:

 

Al K.

 

Here's a plot you missed...

post-864-0-12420000-1445719309_thumb.png

  • Like 4

Share this post


Link to post
Share on other sites

I'd say that is some obvious first order harmonic distortion!

Edited by jwc
  • Like 1

Share this post


Link to post
Share on other sites

n before da lock

Share this post


Link to post
Share on other sites

If you Google "analog tone controls", and click on "images", you are going to get a page full of filters, incorporating the use of passive components used to make contour circuits. A tone control works by lowering or raising the amplitude of certain frequencies to make them sound softer or louder.

Obviously, a tone control doesn't do any signal splitting like a crossover does, but it does use a a series of filters to raise and lower the output.

A crossover is a filter that splits a full range signal and routes the appropriate portion to a specific driver. That's easy enough I suppose. But what happens if we ask the question, "If that's all a crossover is doing, then why do the crossovers built for the same loudspeaker sound so different?" With the exception of the new stock Klipsch networks, all of the aftermarket crossovers use the same transition points used for 60 years; 400Hz and 6000Hz.

When we talk about crossovers, we talk about different types. We also talk about something else; we talk about "rolloff", or the slope used for each section. The "slope" is the rate at which the level of the given range of frequencies increases or decreases - per octave. So we have 6dB/octave (first order), 12dB/octave (second order), 18dB/octave (third order), and so on. We all know that "dB" relates to loudness, and so maybe now might be a good time to start thinking about what's really happening when we choose a specific "slope", or rate of increase or decrease of the audio level for a driver.

post-1106-0-52340000-1445717207_thumb.gi

A crossover filter not only routes selected frequencies to the various drivers, but because of the selected slope, also determines how much power is given to the selected range of frequencies.

Using a 100 watt amplifier, a tweeter with an 18dB/octave slope, crossed over at 5000Hz, will receive 1.6 watts from the amplifier. That same tweeter, crossed over at the same 5000Hz with a first order or 6dB/octave filter, will get hit with 25 watts.

post-1106-0-50340000-1445717239_thumb.gi

The slopes you choose play a significant role in the voicing of the loudspeaker.

I think it's pretty obvious that filters of all types are engaged in the manipulation of power, which ultimately determines not just what we hear, but how much or how little of it. This is why I see a strong affinity with tone controls.

On the other point, I'd like to thank Al for the supporting evidence which underscores what I said about the true behavior of the woofer -- motor behavior is an impediment to using microwave filter design in loudspeakers.

  • Like 1

Share this post


Link to post
Share on other sites

I've re-thought it.  Some good stuff here.  No lock if you can avoid the teen age insults.  I am hiding them.

 

Dave

Edited by Mallette

Share this post


Link to post
Share on other sites

John has endured page after page of insults, and when he's finally had enough, it's time to lock the thread?

This was John's thread, and Al had no business trolling in it. Though subtle and veiled, the personal attacks on John started almost immediately. There was a reason Amy banned Al, and it doesn't look like he learned anything during his absence.

Best plot in the thread.

  • Like 1

Share this post


Link to post
Share on other sites

This has gotten BORING!! You guys that sell these "networks" need to just list your website and go there. GEESH!

Thank you Bonehead!

 

Mark

Share this post


Link to post
Share on other sites

I'd say that is some obvious first order harmonic distortion!

Looks like an "Impulse Response" plot :-)

Share this post


Link to post
Share on other sites

You should put it back. John earned the use of that response.

  • Like 1

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

×
×
  • Create New...