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Multi-Way Conventional loudspeakers with crossovers

comp driver zobel help!
comp driver zobel help!
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Old 2nd January 2018, 07:02 PM   #11
Drummer 35 is offline Drummer 35  Spain
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Erik,

Been playing with the simulation you sent me. Man, this is addictive!

As you suggested, removed the first notch filter, and increased the cutoff freq for the hpf to 1,7kHz.

Added a bypass capacitor to pad down the driver and it seems pretty good. What do you think?

Now I have to figure out how to add the FRDs/ZMAs for the woofers.

Thanks again for your help.
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Old 2nd January 2018, 07:03 PM   #12
Drummer 35 is offline Drummer 35  Spain
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forgot the screenshot.
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File Type: jpg xover test.jpg (671.8 KB, 71 views)
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Old 2nd January 2018, 07:56 PM   #13
Lojzek is offline Lojzek  Croatia
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Remember what you were told by others, it may not be needed to design these networks at all. First start with a high pass and padding resistors, then observe if there is anything wrong with FR in the impedance peaks regions and if there really is, then consider to include some.
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Old 2nd January 2018, 08:39 PM   #14
eriksquires is offline eriksquires  United States
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A - Lojzek is 100% correct.

B - If we are just playing, the cap is a bad idea for two reasons:

1 - If you notice the transfer function wtihout it, the response is flat, so no reason to flatten the impedance.

2 - Notice the minimum impedance has now dropped to nearly 2 Ohms! If you were trying to get a flat impedance, you have gone too far the opposite direction.

Remove your high pass filter, and examine the impedance again and the problem will become more obvious. This is why Zobel's have a resistor in series.

Best,


E
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Old 2nd January 2018, 08:48 PM   #15
eriksquires is offline eriksquires  United States
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Put another way, the main purpose of any impedance compensating network is not a flat impedance, but well-behaved electrical transfer function once the filters are in place. They help the high pass or low-pass filters work ideally.

If you didn't have high pass/low pass filters and worked exclusively with solid state amps, then this work is unnecessary. Indeed, active speakers don't bother with this at all.

The secondary purpose, and it is a big cheat, is to nudge driver phase a little bit.

Best,


E
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Last edited by eriksquires; 2nd January 2018 at 08:51 PM.
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Old 2nd January 2018, 09:53 PM   #16
Drummer 35 is offline Drummer 35  Spain
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Erik, you´re right, there is not a flat impedance curve with the bypass cap, but I thought it could work since the freq response graph showed it flat with no peaks.

Anyway tried what Icg, Earl and Lojzek said. An L pad made the humps disappear.

The problem is that I dont know yet how much padding I´ll need and playing with the resistors values changes the whole circuit.

This xover is simpler and can use smaller coils for the same crossover freq but wont the resistors affect sound? I have read somewhere that padding resistors made some drivers to sound dull.

This is the schematic I got now.

Thanks again!
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File Type: jpg xover test 6.jpg (681.0 KB, 55 views)

Last edited by Drummer 35; 2nd January 2018 at 09:57 PM.
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Old 2nd January 2018, 10:09 PM   #17
eriksquires is offline eriksquires  United States
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I think there's something about over damped woofers, with low Qms or something like that. Forgot.

Yep. Please keep in mind this is all purely electrical until you add the driver's actual FR!

One thing to notice is the rise in output at the top octave. This is caused by the rising inductance in the coil. Well, take a look at the driver. The natural top octave is supressed, so you actually WANT the impedance to rise, and get a boost there. It won't fully make up for it, but this is a case where the Zobel is actually counter productive.

Best,

E
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Old 2nd January 2018, 10:31 PM   #18
rickmcinnis is offline rickmcinnis  United States
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eriksquires is probably the only person who loves Xsim even more than I do.

Mr. Waslo is an audio god in my most unhumble opinion. So my bias is made clear.

I have learned the hard way: you may find an optimal sounding crossover by just doing it by ear or simple level measurements but what you will learn by using XSim will show you, as it did for me, what you think will work, what everyone tells you to use, will not be optimal.

If you want to get it right and learn lots of very interesting things along the way, get REW, or something like it, that allows to you take impedance measurements. I would recommend mounted in the horn along with any other drivers you will use in the network.

Measure the frequency response of each driver, both near-field and at your listening position. I have found I got better insights into what to do with listening chair measurements. The predictions were closer since the full system measurement is taken from the listening chair.

Load these files into Xsim and have some real audio kook fun playing around with configurations. Running through values so you can see the trends in that position. But then I still enjoy playing FREECELL so I may be easily hypnotized by crude video games. But you learn something from XSim. You will develop a conception of what is really going on in your crossover. It will be a collaboration. Xsim is a great audio friend to have around.

I found getting the system flat, and this may be characteristic of compression drivers, that it would not sound right at all. I am using John Inlow's very large mouth horns for the 2441. It must concentrate the intensity, at the listening position, which seems to be ignored by the microphone. I am using the "calibrated" (USB stick), I think it is the DAYTON, sold by people who offer this service at a reasonable price.

When I stand in the room while a measurement is being made, even with a downward slope from 3 kHz, it sounds even in level to my ears. I know I am not the first person to notice this! You can make it measure (I am speaking only of compression drivers, since that is all I know) "flat" but you will not like it unless you have an overly damped room.

There is no question the parallel resistor is the great leveler. I have read folks who say this will decrease the dynamics. If there is a reduction it is minimal. One thing for sure you can hear this quite clearly! It is close to magic.

If you think you are going to, with one try, come across the best values for your network you are going to be disappointed. You will find that what you end up with is quite different from what you started with. And you will be glad you stuck with it.

As Herb Reichert said in an article in SOUND PRACTICES; he was told to "remember the loudspeaker plays the room" so you have to tailor your loudspeaker/crossover to the room and improve your room to get great sound. The advantage the DIYer has is that one can get sound that cannot be brought home in boxes.
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Old 3rd January 2018, 10:50 AM   #19
Drummer 35 is offline Drummer 35  Spain
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Hi Rick.

I know it wont be the optimal filter and dont know how accurate are those simulations, but I want to make a filter to start with, and then modify or "fine tune" it.

I'll take a look to REW too, never used it.

Anyway Im beginning to think that it could be a too ambitious project since I never built an speaker with parallel woofers and with a diy horn+comp driver.

Id like to make it work, but have tons of questions.

The more I read, the more questions I have.

Nos im not sure if this is a good xover freq to start with ir if I should start líder (around 1kHz). What tune freq for the horn?

Thanks for your patience...
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Old 3rd January 2018, 09:28 PM   #20
Drummer 35 is offline Drummer 35  Spain
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Hi again!

I have some updates:

Captured the manufacturers impedance and freq response curves using VituixCAD. So finally got the needed .zma and .frd files for my drivers. (Thanks Erik!)

After some hours I got the attached schematic. I have almost all components for those values.

Please, let me know if it seems like a reasonable xover circuit for those drivers.

Thanks!
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File Type: jpg test xover dual woofer.jpg (717.1 KB, 43 views)
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