mboxler
-
Posts
574 -
Joined
-
Last visited
Content Type
Forums
Events
Gallery
Posts posted by mboxler
-
-
My take on this is more mathematical. I'll update this post with an example soon.
-
Danny Richie of GR Research says yes. He discusses this 7:20 into this video...
https://www.youtube.com/watch?v=RrpIBQ7gW5Q
I think the extra voltage comes from the amp, not from the shunt capacitor.
Thoughts?
-
1
-
-
I decided to leave my Heresy E2 crossovers alone, so selling the JEM kit.
$30 shipped.
Mike
-
1
-
-
On 2/9/2022 at 1:45 PM, StevePaul said:
Voice coil inductance also affects how well the lower sensitivity woofers match up to the higher sensitivitysquawkers in the 400hz-800hz range. Take a woofer with an Le of 1.6 compared to a woofer with an Le of 0.6, ....and the 1.6 Le woofer is going to be general sloping down of several db's in that 400-800 zone compared to the 0.6 Le woofer. The presence region becomes more difficult to control/maintain with a high inductance woofer voice coil, without a zobel. Or...use a woofer that has a low voice coil inductance..mabye 1.0mH or less. Of course once you add in baffle step and other factors, it is more involved; but voice coil inductance is an important aspect to consider.
I measured Le on my Hersey K-22-R's (Rola, I believe), and got 2.2mH @ 1000hz 😮. I realize voice coils are not true inductors, but is it okay to measure them this way? Using a DER EE DE-5000 LCR meter.
-
13 hours ago, captainbeefheart said:
Certainly could be.
What amp are you using to drive the bass bin? Amps with a high output impedance will track the impedance plot of a driver and 60Hz is about where the impedance dips down to it's lowest spot around 4 ohms. It continues to track along with the high impedance resonance area below it.
Nice idea, but I decided to measure my other Khorn, and came up with this plot. Red is the left speaker, green the right. Way different up to 75hz. When my back recovers from shoveling the snow coming in later, I think I'll swap the two speakers and re-measure. This will tell me if it's the room or the speakers???
-
Well, measuring voltages is a lot easier than SPL 🙁. This is what I get measuring my Khorn bass bin only, no crossover. I assume the big suck out at 60hz is my room? 1/24 smoothing.
-
On 2/11/2022 at 10:24 PM, DrWho said:
I think there are a few reasons...
1) The goal of a xover design includes more than the voltage response at the transducer. You're trying to blend the acoustic output of two drivers together, AND you're trying to offset the power response of the speaker. The ideal voltage response will therefore be different than the ideal filter calculators compute.
2) A Zobel requires extra parts, which adds cost. For the same price, you could go to a higher order filter and get more frequency shaping.... Whereas a Zobel doesn't necessarily move you in the right direction (although sometimes it does). The Zobel is just one of many filter tools to achieving a desired result.
3) A Zobel consumes power, although it depends on how it was designed. High power dissipation tends to be a recipe for injecting distortion.
I agree with all your points. In my case, much of what I'm doing is educational. When I first started this "hobby", I knew nothing about crossovers. I then built ALK's Universal kit, and had no idea what the components were doing. The schematic called for a 1.3mh woofer inductor. Al's point was that the 1mh voice coil should be subtracted from the normal 2.5mh inductor used in, say, the Type AA. A couple of years ago I replaced the 1.3mh with a 2.5mh. I soon began to wonder what was really going on.
Attached are plots of various lowpass filters (voltages are across a K-33-E in my Khorn).
Blue is 1.3mh
Green is 2.5mH
Black is AK-3
Red is AK-4 (I only have a 5.4mH inductor, so I used 200uf to arrive at the same resonance frequency)Next step is to measure SPL using these filters.
-
1
-
-
2 hours ago, Crankysoldermeister said:
Wouldn't swapping electrolytics with polyesters also "change" the transfer function?
Any change impacts the transfer function, but do minute changes actually translate to significant changes in frequency response?
Looking for 3 cents.
Apologies to the OP, but Dean made me do it!
I realize I don't have the most sophisticated equipment, but here are my findings.
This is the transfer function of a 4.1mh inductor with a 6 ohm resistor load. A capacitor is across the resistor to create a 2nd order filter.
The blue plot is a 33uf electrolytic that measure 29.9uf and .44 ohm ESR.
The red plot is a 30uf Solen polypropylene (I don't have a polyester) that measures 30.25uf and .01 ohm ESR.
It's hard to see, but the max difference is around .3db. Not sure how audible this would be.
-
1
-
-
51 minutes ago, Edgar said:
Thanks for the links! My searches didn't help much.
-
I realize I'm one of very few that finds this interesting, but at least I have a handy way of documenting my results. Apologies to all that view this, only to immediately press the back button.
My experiments have revealed some interesting things (to me anyway) regarding low pass filters, in my case, to a K-33-E installed in my Khorns.
I never realized how much the voice coil influences a passive crossover.
On the attached plot, the yellow represents the voltage across the K33 in series with a 2.5mh inductor. Notice how the voltage starts to drop very early and continues to drop, eventually at a 3db per octave rate.
I've never used a zobel network, and decided to give it a try. I settled on a 4 ohm resistor in series with an 80uf capacitor, in parallel with the K-33. Since this gives me a pretty constant impedance of around 4 ohms from 200hz on up, I chose a 1.6mh inductor for the next test. A 1.6mh inductor is around 4 ohms at 400hz. The purple represents the K33 voltage. As you can see, it looks more like a first order low pass at 400hz.
I'm curious why zobels aren't used more often. With one, it's easier to shape the woofer voltage knowing that the voice coil inductance isn't messing with the frequency response of the crossover.
-
6 hours ago, Rolox said:
Thanks a lot! I used to have the attenuation values, but not the polarities 😉
Just in case that document doesn't address your question directly...An autoformer has no polarity.
The taps on the 3619 are 5, 4, 3, 2, 1, X, and 0. If you connect input + to tap 5, and input - to tap 0, then tap 4 will be + and tap X will be -. In fact, given that input configuration, the output tap closest to tap 5 will be +, and the output tap closest to tap 0 will be -.
Now, if you were to connect tap 4 to the driver - and tap X to the driver +, the polarity to the driver will be reversed. Al does this with his Universal to help correct the phase shift created by the 2nd order low pass ahead of the autoformer.
-
1
-
-
10 hours ago, attanasio666 said:
Hello guys. I decided I'm gonna build this network but there's just one thing I'm not sure I understand. In the Woofer section of the schematics, the "0.66mh" and the "6.8 ohms". Are those the measurements for the woofer coil or are they parts I need to add?
I believe that's how Al simulates the K-25-K woofer. Don't include those components.
-
According to this old thread, the early AL crossovers did not have zener diodes.
https://community.klipsch.com/index.php?/topic/73232-schematic-for-type-al-crossoveranyone/
-
1
-
-
50 minutes ago, Defacto said:
I was waiting to see if there were objections. I'll do that today since there were none.
If this is what it takes, I'll be sending them in:
I'm sure your back will object, but if it were me, I would rule out as much as possible before doing anything. I am curious, though. When you say "volume at 80" is that 80 out of 100 or -80db?
-
1
-
-
3 hours ago, Defacto said:
I welcome suggestions on how to proceed.
At this point, my best plan is to replace one R26F with a Forte II, one at a time, and turn the volume to 80.
How did this test go?
-
5 hours ago, Defacto said:
The probes I used were defective it seems. Another set of probes show both speakers around 7 ohms. Sorry for the bad info.
Even this doesn't seem correct to me. Isn't the Forte II K-25 woofer 4 ohms? I just read another post that said the DC resistance at the speaker terminals measured 4.3 ohms, which sounds right if you add in the DC resistance of the inductor. He also noted that the impedance of the speaker drops below 4 ohms between 100 and 200hz. That's a lot of current!
Might be interesting to remove the wires from the woofer and measure the DC resistance across the K-25 terminals.
-
1
-
-
2 hours ago, Defacto said:
This looks bad.
I would describe it more as scuffed or untidy.
Can you take a picture from the other side? Perhaps the 110uf electrolytic capacitor has failed, but we can guide you through some further measurements.
-
1
-
-
Even though I'm not a Sonos user, I still found this kinda cool. Each Symfonisk contains multiple chips, including a PCM5102A DAC and TPA3116D2 class D amp. All set up to stream, bi-amp, and apply room correction for the two internal drivers.
This gentleman bypasses the internal Symfonisk drivers and connects the amps directly to the KG4 drivers. Around 14 minutes.
-
1
-
-
1 hour ago, John Warren said:
Useful to measure voltage across a load resistor for amplifiers under test.
Nice! I assume you can also measure voltage across crossover outputs? I'm going to build a new crossover for my Heresy's, but was curious what the current E2 crossover was doing. I'm using REW to do the sweep/measure, and this is what I got. Would be nice to have one of those devices to verify my results.
Red amp, upper green woofer, blue squawker, lower green tweeter.
-
1
-
-
It's a stereo version though...
https://www.ebay.com/itm/313680365069?hash=item4908ce860d:g:APsAAOSw-QthR2CA
-
2 hours ago, Klipschtastic said:
I had no idea how much i have attenuated mine but I'm curious to actually measure.
Hey Jon
The best way would be with a true rms multimeter. I'd actually measure a few things...
Play a test tone, say 1000hz. It doesn't have to be real loud, as you are just creating a voltage that can be measured.
Measure the voltage across taps 0-5 of the T7A autofomer (input).
Measure the voltage across taps 0-2 of the T7A autoformer (output). This should measure around .316 times the voltage across taps 0-5, or -10db.
Measure the voltage across the wires connected to the squawker. The difference between this voltage and the voltage across taps 0-2 is the attenuation created by the lpad.
If you are curious about the difference in db, you can enter the measurements here...
http://www.sengpielaudio.com/calculator-amplification.htm
I hope this is what you are after.
Mike
-
Stumbled across an old thread where Bob Crites posted several autoformer PDF's. The T4A was one of them, so I now know the specs.
https://community.klipsch.com/index.php?/topic/87280-heresy-ii-crossover-schematic-cleaned-up/
-
I thought I'd use this technique to see what, if any, effect the inductance of an autoformer (in this case a T2A) had on the frequency response.
I ran two measurements.
First (red) was a 27.2uh capacitor in series with a 14.62 ohm resistor.
The second (green) was a 6.8uf capacitor connected to tap 5 of a T2A. I then connected tap 3 to the same resistor. Since the load on the capacitor now 4 times the resistor, I used a 27.2 / 4 capacitor. I then added 6db to the green plot.
As I thought, the inductance between taps 0 and 3 of the T2A does contribute to the frequency response.
Trying to figure out how to run this same test on a K-55M/K-400 to get a real world plot.Mike
-
2 hours ago, Toz said:
"Phase issue"?
The mid level is 2db higher on the AK3 if I'm remembering right.
Oct 1989: The AK-3 network was introduced to correct for a shift in the output of the K-55-M mid-range driver.
I assume that meant phase shift, but maybe not???
It's only 1 db higher, but the woofer capacitor and squawker inductor were changed as well.
.jpg.081b1079aac5b282abe5f32f971be121.jpg)
.png.aa79f66274aa68656cfdb9118019f433.png)
.png.1d51d064deb89401ee0b3e50baebc5fc.png)
.png.cb7467c0f5ba7e0159d7d3e5cf6d7f5f.png)
.png.551ee4941afac18a32d183d6b44ada97.png)
.png.7d499ace0426cd87aec050466a5bc0c3.png)
.png.ed6be4a643b376b23ca334f02505d944.png)
.png.89ff6a79a1051d83a55750a2aba14301.png)
.png.aad77bee77baabcdd7242ce2bce972d7.png)
Are Shunt Capacitors in the Signal Path?
in Technical/Restorations
Posted
A circuit consists of a 4mH inductor in series with a 6 ohm resistor. A 100uf capacitor is across the resistor. Frequency is 170Hz.
At that frequency, the impedance of the parallel resistor capacitor is 5.05 ohms @ -32.65 degrees, and the impedance of the inductor is 4.273 ohms @ +90 degrees. Add the two together and you get 4.525618 ohms @ +19.99 degrees for the entire circuit.
2.83 volts (amplifier) into 4.525618 ohms (circuit impedance) equals 0.62532896 amps.
0.62532896 amps into 5.05 ohms (capacitor/resistor impedance) equals 3.1579 volts.
The voltage across the resistor is higher than the amplifier voltage.
Danny would say the extra voltage comes from the capacitor(?). I think it's because the impedance of the capacitor/resistor (5.05) is greater than the impedance of the entire circuit (4.525618). Or are we both saying the same thing in a different way?