2 Way speakers - Suggestions on improvements?

[Sultanen]

Here are the pics. You won't get agreement with the FR because you don't have my impedance file. I'll send it all to you when I figure out how to upload.

WOW that curve looks awesome! Im soo looking forward to hearing these speakers IRL in the future! 😀 How does it look below 100Hz? Steep dropoff like usual?

To upload the FRD file you have to rename it to .txt, i guess thats the issue you see? Otherwise just ask and we should figure that out, im a software developer after all ^^

 

[eriksquires]

By phony, you mean that they should not be there in the final design?

I could try to get an impedance curve if its important, i have made so many measurements on these drivers now, a few more cant be to bad 😛 But i love your comparison 😀

Yes, phony means I am just using them to trick XSim into thinking it has the right driver data, instead of the "ideal" 8 Ohm purely resistive driver that you get without ZMA files.

Adding the 56 Ohm resistor and 0.1 mH inductor forces XSim to calculate the final FR more accurately, but in real life these qualities are encapsulated in the tweeter already.

That's one alternative for the woofer too. If we knew the actual R and L values, we could compensate for that instead of attempting to use a substitute file like I did. Not sure which would be more exact.

Ideally we want a ZMA file like the output of Dayton DATS V2. Then you just load it up in XSim. 🙂

Best,


Erik

 

[eriksquires]

WOW that curve looks awesome! Im soo looking forward to hearing these speakers IRL in the future! 😀 How does it look below 100Hz? Steep dropoff like usual?

To upload the FRD file you have to rename it to .txt, i guess thats the issue you see? Otherwise just ask and we should figure that out, im a software developer after all ^^

No, I want to send you the entire XSim file, zipped.

Erik

 

[Sultanen]

You need to re-take the FRD for the woofer alone, and it needs to be at least from 40 Hz.

Your measurement tool should allow you to export it. If not, oh well. 🙂

I will redo the woofer measurements! I have the speakers in a slight angle towards the listening position, is this an issue or should i measure it like i usually have them?

The crossover design I came up with was for the FR you had, which is in the middle of the room. And if you will listen with the speaker there it will be fine. 🙂 But the problem is you are listening with the speaker against the wall.

The wall will re-inforce the bass and there will be less to compensate for. That will have a cascading effect on the Baffle step, the second pole, and the tweeter level.

I mentioned this many pages ago, that to actually design the crossover you'd want to get the FR for the woofer in it's normal place. When you re-measure you'll see how big a difference this is.

Best,


Erik

Sorry for forgetting about this, is the woofer in its normal position the only FRD i need to redo?

 

[eriksquires]

By phony, you mean that they should not be there in the final design?

I could try to get an impedance curve if its important, i have made so many measurements on these drivers now, a few more cant be to bad 😛 But i love your comparison 😀

Yes, the impedance of the woofer IN THE CABINET is critical to getting the right FR. Especially with some of those inductors, it's going to be more expensive, so if you are going to spend the money on parts, you need to be sure to have the right one's. We'll also use that to guage the benefit of a Zobel, if any, so you'll want to be sure to measure up to around 5k if you can. This may be limited by your meter's max F. You can test it by doing a frequency sweep of the amp's output. Your amp is going to be nearly flat compared to your meter. Tune the frequency up until you see the meter V start to drop off. This is your meter's maximum effective measurement frequency. Of course, you could compensate for this a little if you wanted by figuring out exactly how it rolls off, but let's not go there. 🙂 Of course, if you have a scope, almost any of them have accurate measurements well beyond the limits of human hearing. Personally, I use DATS, hit "measure impedance curve" and then "Export..." and I'm done.

Again, we need you to get JUST the woofer in place. The original measurements were to get the driver to driver distance AND the most accurate tweeter FR. If you did that right, there's no need to do it again.

Compare your woofer measurements in free-air and against the wall and you'll see how big a deal this is. 🙂

Best,


Erik

 

[Sultanen]

No, I want to send you the entire XSim file, zipped.

Erik

Aha, there should be no issue uploading zip files to the forum. If you keep having issues maby you can sent it to my email?

 

[Sultanen]

Yes, phony means I am just using them to trick XSim into thinking it has the right driver data, instead of the "ideal" 8 Ohm purely resistive driver that you get without ZMA files.

Adding the 56 Ohm resistor and 0.1 mH inductor forces XSim to calculate the final FR more accurately, but in real life these qualities are encapsulated in the tweeter already.

Okey, thanks for explaining 🙂

That's one alternative for the woofer too. If we knew the actual R and L values, we could compensate for that instead of attempting to use a substitute file like I did. Not sure which would be more exact.

Ideally we want a ZMA file like the output of Dayton DATS V2. Then you just load it up in XSim. 🙂

Best,
Erik

Unfortunately i dont have a Dayton DATS V2 so we will have to make do with my new fancy multimeter and my computer, i hope thats enought even if it will be more work for me 😛

How would you go about measuring R and L? Is R just the DC resistance across the Woofer?

Yes, the impedance of the woofer IN THE CABINET is critical to getting the right FR. Especially with some of those inductors, it's going to be more expensive, so if you are going to spend the money on parts, you need to be sure to have the right one's. We'll also use that to guage the benefit of a Zobel, if any, so you'll want to be sure to measure up to around 5k if you can. This may be limited by your meter's max F. You can test it by doing a frequency sweep of the amp's output. Your amp is going to be nearly flat compared to your meter. Tune the frequency up until you see the meter V start to drop off. This is your meter's maximum effective measurement frequency. Of course, you could compensate for this a little if you wanted by figuring out exactly how it rolls off, but let's not go there. 🙂 Of course, if you have a scope, almost any of them have accurate measurements well beyond the limits of human hearing. Personally, I use DATS, hit "measure impedance curve" and then "Export..." and I'm done.

I love it that you care both about the speaker and my wallet 😉
If its critical to get the right FR then i think that we need to get the impedance curve some way! How would you suggest measuring it with the equipment i have? I did the frequency measurement of the woofer in and outside the box by this method:
https://www.youtube.com/watch?v=EMhmVmtQ4BI
Just sweeped the frequency until i found the peak. I guess i can do something similar and just note the values at each frequency measurement point?

I don't have a scope.. yet.. it's something that ive been eager to buy for some time now but it will have to wait a bit longer i think..

Again, we need you to get JUST the woofer in place. The original measurements were to get the driver to driver distance AND the most accurate tweeter FR. If you did that right, there's no need to do it again.

Compare your woofer measurements in free-air and against the wall and you'll see how big a deal this is. 🙂

Best,

Erik

I think i did that right at least, apart from with the tweeter where i may have had the mic a little bit missaligned but thats hopefully corrected in the curve a posted earlier today.

 

[eriksquires]

So you found the resonant frequency. What we want is at multiple frequencies, what is the impedance at each one? 🙂

So, you sweep from 20 to 5kHz using a resistor of a known R, say around 4 - 10 Ohms. You put that resistor in series with your woofer and measure the voltage at the resistor. As the voltage drops at the R, the impedance is at maximum in the woofer, and vice versa.

I'm afraid I'm having a terrible allergy and cold right now, this is just the principle. I'm sure some one else can help you.

Part of this however is knowing the limitations of your meter. See if you can find the max AC frequency or something like that. Otherwise you will have to:

1- Get signal generator
2 - Calibrate at 60 Hz. Increase the volume on your amp until it says 1.00 V
3- Sweep from 20 Hz up wards. Yo'll notice that at 60 Hz and for a while it will read 1.00 V.
4 - Notice when meter's V starts to drop. It should be really good up until 60Hz, then at some point, maybe 100Hz, maybe 10kHz, the V reading will start to get lower and lower. That's how you know the limit of your meter.
5 - Now measure the V across an R of a known value. Sweep from 20 Hz up to your meter's frequency limit, which you found above. Use your own judgement. Below 100Hz, maybe do every 5 Hz, then every 100Hz after that or something. Most critical part is the area around the resonant frequency, then after that a general idea of the shape and magnitute of the impedance is all we need. You don't have to be very careful below and above that peak.

I'd use a voltage that's comfortably in the meter's range, like 1V or something like that. When you see it go from 1.0V to 0.9 then 0.4 you'll know you hit the "Knee" it just depends on your meter's design.

What we'll miss is the phase of the impedance, i'm sorry I don't remember how to get that, but you should be able to find some online guide.

Best,


Erik

 

[Sultanen]

This would be much more accurate if we had real impedance curves instead of the one I borrowed from a Focal driver. It matters most for the woofer, but the tweeter as well.

Let's go over the schematic.

Tweeter
I used two "CircuitBlocks", a High Pass 2nd Order and an L-Pad. R2 and L3 are just there to make XSim pretend the tweeter is closer to the real one. R2 makes the effective 8 Ohms 7. The 0.1mH inductor is straight from the spec sheet. In real life, you would not buy these, they are part of your tweeter already.

C4 is an equalizer that's helping to boost the top end of the tweeter. It's essentially a high-pass filter around that resistor. We're cheating because that resistor is both part of the L Pad and part of the EQ circuit. It happened to work, but in some cases you'll need to break that resistor down into 2 and bypass only one of them. Examine the FR as you remove it and add it back in. Also examine the Component Voltage graph for S1. You will see the voltage at the tweeter change as this value changes.

Woofer
This one is not going to match real life very well for two reasons. One, we are using phony impedance curves, and two, I suspect the FR was from free-space. We need the FR from the speaker against the wall for the woofer to be accurate. Still it's a good example.

L1/R1 are the Baffle Step Compensation, but also part of the low pass network. C1 is the second pole. C3/R6 are a Zobel network I threw in. It keeps the impedance of the woofer low despite the inductance. To see the effect, pull out the tweeter high pass block, and add and remove the ground at R6. Look especially at the impedance curve. It has the end result of helping to keep the downward woofer slope stay consistent, but also changes the overall phase of the woofer, so sometimes this circuit can be played with to get better phase matching.

I will just acknowledge your great post here! I think that i will have to play around with the circuit in Xsim to actually understand your explanation!

R5 is an impedance compensating circuit. When I looked at the impedance plot there were some very high numbers. If you were using tubes it would be mandatory. With solid state it's optional, but it can prevent ultrasonic ringing, keeping your amp from working extra and some say makes it sound better. Again, try adding and removing it while looking at the impedance plot.

Im not using tubes atm but i may verry well be in the future so if we can make the crossover adopted to tubes then why not? 🙂 Its so cool!

 

[eriksquires]

Exactly HOW do you attach ANY file besides a picture?

I've attached the ZMA file for the Focal 6W4456, which is oddly similar to your driver.

Erik

 

[robotc]

How did you measure the resonance frequencies you posted? Did you use REW?

Robert

 

[eriksquires]

1.029 5.374 -0.978
1.059 5.374 -0.978
1.091 5.374 -0.978
1.122 5.374 -0.978
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1.335 5.182 2.312
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1.456 5.182 2.312
1.498 5.182 2.312
1.542 5.182 2.312
1.587 5.182 2.312
1.634 5.182 2.312
1.682 5.182 2.312
1.731 5.182 2.312
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1.834 5.182 2.312
1.888 5.182 2.312
1.943 5.182 2.312
2.000 5.099 4.605
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2.448 5.099 4.605
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2.670 5.141 5.372
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2.911 5.141 5.372
2.997 5.141 5.372
3.084 5.141 5.372
3.175 5.141 5.372
3.268 5.141 5.372
3.364 5.156 6.719
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3.668 5.156 6.719
3.775 5.156 6.719
3.886 5.156 6.719
4.000 5.183 7.872
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4.362 5.183 7.872
4.490 5.183 7.872
4.621 5.183 7.872
4.757 5.216 9.224
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5.040 5.216 9.224
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5.339 5.244 10.542
5.496 5.244 10.542
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5.823 5.244 10.542
5.993 5.293 11.905
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35.919 14.757 58.997
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39.170 20.362 59.554
40.317 22.149 58.764
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49.351 60.691 16.677
50.797 64.499 0.869
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1933.055 14.873 43.781
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20642.546 70.370 57.884

 

[Sultanen]

Exactly HOW do you attach ANY file besides a picture?

I've attached the ZMA file for the Focal 6W4456, which is oddly similar to your driver.

Erik

Below the response textbox you have a "Go advanced" button, click that and you get into an extended reply form, scroll down the page and you get a "Manage Attachments" button. Click that and a popup will appear where you can browse for files and then click "upload". You can then close that popup.
Make sure that the file extension is one of the listed:
"asc bmp doc gif jpe jpeg jpg pdf png psd txt zip" otherwise you have to rename the file to attach it 🙂

 

[Sultanen]

How did you measure the resonance frequencies you posted? Did you use REW?

Robert

I used rev to give me a frequency but i used a 10ohm resistor connected as in this video:
https://www.youtube.com/watch?v=EMhmVmtQ4BI
When i got to the peak voltage i read the Hz in REW.

 

[Sultanen]

On page 36 they show a circuit to connect to REW in order to measure the impedance curve. My issue is that i have a Macbook Pro. The headphone jack has GND, left, right, mic so i don't have stereo input as required by this drawing:
http://www.roomeqwizard.com/REWhelp.pdf or here http://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html

 

[eriksquires]

Alright, let's see if it worked this time, I've attempted to attach the XSim project I was working on.

 

[eriksquires]

Yes, phony means I am just using them to trick XSim into thinking it has the right driver data, instead of the "ideal" 8 Ohm purely resistive driver that you get without ZMA files.

Adding the 56 Ohm resistor and 0.1 mH inductor forces XSim to calculate the final FR more accurately, but in real life these qualities are encapsulated in the tweeter already.

My mistake. The 0.1mH inductor will make the impedance of the coil+ tweeter circuit be more accurate but since the FR is not taken from the inductor the tweeter will actually be a little off itself.

If you think about it, what is the shape of the wiring inside a driver that makes it work? It's just a coil, exactly like the coils you use in the crossover. That's where the R and L of a driver come from.

If you can get REW working and automate the whole thing, it's worth getting the tweeter impedance curve as well.

Best,


Erik

 

[5th element]

Here is a measurement guide I made a while ago for ARTA that is fairly easy to follow. Just dropping this in case a different perspective from a different program would be useful. From the quick peruse of this thread it seems like Sultanen is being guided in the correct way but the measurements seem a little lacking.

measurement guide

This may help! So good luck 🙂

 

[eriksquires]

I will redo the woofer measurements! I have the speakers in a slight angle towards the listening position, is this an issue or should i measure it like i usually have them?

Measure the speakers like you listen to them. Just make sure the microphone is on tweeter axis and at the same distance to be consistent. Also, is the tweeter normally in line with your ear? If not, you might want to flip the speaker around when you listen. Also, if the tweeter is near reflective surfaces you probably don't want to measure like that either. 🙂

Usually, but not always, we put the tweeter at the ear axis and then adjust the woofer relative to it. Some designers do the opposite, putting the center of the mid-woofer at ear axis and adjusting the tweeter. This probably has something to do with the tweeter being better sounding off axis. Not a problem with yours though, I'm pretty sure given it's geometry you'll want to listen with your ears straight in front of them. IT also may help get near-perfect timing. If you listen on the woofer axis, and the tweeter is delayed relative to it, you might actually get close to simultaneous arrival at your seat. A neat trick! 🙂 If your tweeter weren't so big I'd suggest it, but given it's size, it beams fairly low in the frequency spectrum.

Sorry for forgetting about this, is the woofer in its normal position the only FRD i need to redo?

Yep.

Why? Because we assume the tweeter's output will be heavily driectional and independent of the wall behind it. However the woofer's output for a while will be omnidirectional. Until the woofer becomes directional, the signal will travel all around the speaker and be supported by the wall behind it.

This is why Baffle Step happens.


Best,

Erik

 

[Sultanen]

Hi again,
Sorry for responding immediately.
I had to give up getting impedance measurements with the built in soundcard of any of the 6 laptops i tried with so yesterday i bought myself the little USB soundcard UCA202! Amazing a great little thing that gave me the impedance measurements in just a few minutes 🙂