Hey everybody, I just finished putting together a 2 way crossover design in Xsim. I have generated my own .frd files with the drivers installed in the cabin, and traced the .zma files from the manufacturer's specs.
Overall I am satisfied with the outcome. But before I give it a go, I'd like to hear your remarks for I am an absolute beginner. I am especially curious about how you would interpret the impedance graph, given the peaks are rather high up on the scale. Should I be worried or is this fine?
.
For reference, I am attaching the manufacturer's graphs for both drivers:
sb15nrxc30 (8 ohm)
Morel MDT29 (8 ohm)
.
Thank you!
Overall I am satisfied with the outcome. But before I give it a go, I'd like to hear your remarks for I am an absolute beginner. I am especially curious about how you would interpret the impedance graph, given the peaks are rather high up on the scale. Should I be worried or is this fine?
For reference, I am attaching the manufacturer's graphs for both drivers:
sb15nrxc30 (8 ohm)
Morel MDT29 (8 ohm)
.
Thank you!
Last edited:
I think the bass peak is exactly what you have input via your copying the the impedance trace to make your zma file.
It will change when mounted in a sealed box, and you will have two bass peaks if you build a reflex box, typically modern drivers work optimally with a bass reflex box.
Depending on your baffle dimensions unless they are the same as the iec baffle that the SB acoustics spec sheet shows you will have slightly differing Inductor and capacitor values for the bass 2nd order filter components L2 and C3.
This is due to the baffle size altering of a typical speaker box being smaller than the iec baffle dimensions, and thus suffering more diffraction loss.
This means in practice you have to use probably larger values of inductance to reduce the midrange output in the 500-approx 1.5 KHz region ( Depending on baffle dimensions and where you place the woofer on the baffle.
The tweeter response maybe ok, but again may not fully represent the response in the cabinet due to diffraction effects.
In terms of the crossover you have managed to achieve a null when you invert the phase to one of the drivers, so the filter slopes are a good match in the crossover region.
I think it will sound reasonable . We all have to start somewhere and it is a good attempt for a first timer.
Nice touch is C6 across the bass inductor to help with woofer break up peaks.
Maybe do some more reading and investigate VituixCad software it is a more powerful solution allowing you design a better speaker, it will take some time to learn the basics and then you can progress from there. Alternatively build this in a suitably sized box and start tweaking the crossover by ear. It can be done.
It will change when mounted in a sealed box, and you will have two bass peaks if you build a reflex box, typically modern drivers work optimally with a bass reflex box.
Depending on your baffle dimensions unless they are the same as the iec baffle that the SB acoustics spec sheet shows you will have slightly differing Inductor and capacitor values for the bass 2nd order filter components L2 and C3.
This is due to the baffle size altering of a typical speaker box being smaller than the iec baffle dimensions, and thus suffering more diffraction loss.
This means in practice you have to use probably larger values of inductance to reduce the midrange output in the 500-approx 1.5 KHz region ( Depending on baffle dimensions and where you place the woofer on the baffle.
The tweeter response maybe ok, but again may not fully represent the response in the cabinet due to diffraction effects.
In terms of the crossover you have managed to achieve a null when you invert the phase to one of the drivers, so the filter slopes are a good match in the crossover region.
I think it will sound reasonable . We all have to start somewhere and it is a good attempt for a first timer.
Nice touch is C6 across the bass inductor to help with woofer break up peaks.
Maybe do some more reading and investigate VituixCad software it is a more powerful solution allowing you design a better speaker, it will take some time to learn the basics and then you can progress from there. Alternatively build this in a suitably sized box and start tweaking the crossover by ear. It can be done.
I don't understand what you mean, it stays at 10ohms untill the very end.
That is not the case for the tweeter since it's a closed back unit, my unit probably wouldn't match with that exact impedance curve but I'll take my chances. As far as I know the woofer's impedance peak shouldn't alter the crossover design since it's way below the crossover point.
Thanks for your detailed answer. As I mentioned I use my own .frd files measured in the actual cabinet, and there is quite some compensation for the baffle loss, here is the graph of the raw responses:
As you can see the woofer (yellow) is at 87-88db around 1k-2k before the crossover is applied (Btw the tweeter is waveguide loaded, that's the reason of that huge bump)
I couldn't agree more, I am not having much fun with xsim tbh
Last edited:
I think you are probably right. But you can put the Thiel-Small parameters in a box modeling program (for example WinISD or VituixCAD) and simulate the impedance in your sealed or ported cabinet. In VituixCAD I think you can export it, in WinISD I think you would have to take a screenshot and trace it. As you said, it probably does not matter, but it might be nice to be more accurate.
Damping or stuffing the cabinet will also affect the impedance peaks. Measuring impedance in the cabinet would capture this, and so would the simulation programs.
But at even higher frequencies you short the amp via C6 and C3.
I don't think you need C3.
Thanks for pointing that out. I observe a lot of people do that, so I thought it would be convenient to share the reverse null.
I actually thought about doing that, but I got overwhelmed by vituix cad. I know it is a very powerful tool and I'll definitely invest my time to understanding it a.s.a.p.
hmmm, is there a way to see that in xsim? Because if I remove the C3 the slope will become 1st order no? I couldn't get a good response with that configuration, especially with that nasty break up.
The measurement is gated and it starts from about 260hz I think. So, below that doesn't represent the actual response of the cabinet.
@AllenB
This issue of a short at high frequencies came up on another forum recently but did not get explained. My understanding is that it is at high enough frequencies that we aren't necessarily going to see it in Xsim or VituisCAD simulations.
One remedy is to put a resistor in series with C6 - maybe 2 or 4 ohms??? But does the notch filter that he already has remedy this anyways???
@hautparlurker
This is the remedy that was proposed on another forum (I ignored your notch filter for simplicity). Putting this 4 ohm resistor in series with C6 does not change any of the graphs that I can see in VituixCAD, presumably because the potential short is beyond 40Khz which is the max that can be displayed.
This issue of a short at high frequencies came up on another forum recently but did not get explained. My understanding is that it is at high enough frequencies that we aren't necessarily going to see it in Xsim or VituisCAD simulations.
One remedy is to put a resistor in series with C6 - maybe 2 or 4 ohms??? But does the notch filter that he already has remedy this anyways???
@hautparlurker
This is the remedy that was proposed on another forum (I ignored your notch filter for simplicity). Putting this 4 ohm resistor in series with C6 does not change any of the graphs that I can see in VituixCAD, presumably because the potential short is beyond 40Khz which is the max that can be displayed.
I just checked, xsim doesn't show beyond 20k. So do I neglect that resistor? Also, afaik most amps don't play beyond 20k (mine certainly does not), even if it was shorted beyond 40k, would that create a problem?
The 4 ohm resistor, with the 0.33 microfarad cap, helps to squash the cone resonance of the woofer.
Usually its value is 8 or 10 ohms, I've used either value. This doesn't affect the simmed frequency response so it must be performing some other function. I read somewhere in another forum that it's important to add a resistor to that small cap for some technical reason which I don't understand, but some similar filters don't use it.
Geoff
Usually its value is 8 or 10 ohms, I've used either value. This doesn't affect the simmed frequency response so it must be performing some other function. I read somewhere in another forum that it's important to add a resistor to that small cap for some technical reason which I don't understand, but some similar filters don't use it.
Geoff
Last edited:
Many amplifiers go unstable at very high frequencies when driving a capacitive load. This will likely occur well outside the audio band. Best case, your amplifier will distort, worst case it will destroy itself.
1) In the particular case of post #1, does the notch filter with a 10 ohm resistor in series to ground avoid the problem?
2) In my circuit of post #13, what resistor value would you typically use?
3) How real is the problem?
I can find several well know designs with that circuit. Below is the Overnight Sensations, almost surely the most frequently built DIY speaker of all time.
Sorry, i mixed the caps up! It should have been: you don't need C6!
but the suggestions above with an additional resistor seem reasonable.