Has anyone carried out or seen any distortion measurements in crossover networks using bipolar electrolytic caps?
I've just been simulating a crossover for a project and thought I would try including the capacitor dissipation factors. Setting the DF to 6% (as specified for Jantzen electrolytics) gave no discernible change to the filter responses. However, I have no idea whether the distortion would be unacceptable or not.
(Such caps are considerably smaller and cheaper than their poly counterparts).
I've just been simulating a crossover for a project and thought I would try including the capacitor dissipation factors. Setting the DF to 6% (as specified for Jantzen electrolytics) gave no discernible change to the filter responses. However, I have no idea whether the distortion would be unacceptable or not.
(Such caps are considerably smaller and cheaper than their poly counterparts).
Have a look at distortion graphs in post#3 and post#7. I removed an input electrolytic (a cheap one) and replaced it with a polypropylene. Budget active subwoofer lowpass, buy, eval, mod
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You just have to avoid sufficient and prolonged reverse DC that will damage them. However in this case because there is no DC, and the AC levels are small w.r.t cap rating, it can be used. It's just not very good.
There are some better biplor electrolyics like Nichicon Muse. I have some on order, (for another low budget project) when I receive them I can run A-B test against a poly and post it. The motivation is higher capacitance for lower cost vs degree of performance loss.
There are some better biplor electrolyics like Nichicon Muse. I have some on order, (for another low budget project) when I receive them I can run A-B test against a poly and post it. The motivation is higher capacitance for lower cost vs degree of performance loss.
Dissipation factor and distortion are not necessarily related. Dissipation factor of a capacitor is simply the real component of its impedance, which can be the result of something as simple as a linear resistance, which does not require distortion in order to exist.
I have measured the distortion of electrolytic capacitors by driving them really hard with a sine wave signal and examining with a sensitive distortion analyzer. Typically, electrolytic capacitors have very low distortion, especially when compared to numbers like 0.6% that you quoted for a cap's DF. So, the simple answer is that a capacitor can distort or not, but the dissipation factor is not necessarily an indication of that. Further, if a cap has some amount of dissipation factor, the great bulk of it will be linear resistance or resistive type losses.
I have measured the distortion of electrolytic capacitors by driving them really hard with a sine wave signal and examining with a sensitive distortion analyzer. Typically, electrolytic capacitors have very low distortion, especially when compared to numbers like 0.6% that you quoted for a cap's DF. So, the simple answer is that a capacitor can distort or not, but the dissipation factor is not necessarily an indication of that. Further, if a cap has some amount of dissipation factor, the great bulk of it will be linear resistance or resistive type losses.
Very useful measurements. The bipolar cap distortion is remarkably low.
It will be interesting to see DonVK's results.
Finally got parts and time to do this test. It's connected to another thread to make a budget speaker silk purse from sows ear contest?
I think the cap quality is less important for LP shunt caps and have used good bipolars for shunts in an LR4 without issue. That same LR4 used polys for all series HP caps. I have a bias to use polys for all series caps.
This test (pics below) used a 2nd order XO (from my budget project) and I compared the measured responses for the HP series cap used for the tweeter. The poly cap is a Solen 2x 2.2uF (4.4uf) and the bipolar is Nichicon Muse 4.7uF. The comparable cost for a single 4.7uF is $4 poly and $1 bipolar. The $$ difference grows very quickly for larger values and voltages.
I don't see any significant measurement differences between them and they sound the same to me.
I think the cap quality is less important for LP shunt caps and have used good bipolars for shunts in an LR4 without issue. That same LR4 used polys for all series HP caps. I have a bias to use polys for all series caps.
This test (pics below) used a 2nd order XO (from my budget project) and I compared the measured responses for the HP series cap used for the tweeter. The poly cap is a Solen 2x 2.2uF (4.4uf) and the bipolar is Nichicon Muse 4.7uF. The comparable cost for a single 4.7uF is $4 poly and $1 bipolar. The $$ difference grows very quickly for larger values and voltages.
I don't see any significant measurement differences between them and they sound the same to me.
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Finally got parts and time to do this test. It's connected to another thread to make a budget speaker silk purse from sows ear contest?
I think the cap quality is less important for LP shunt caps and have used good bipolars for shunts in an LR4 without issue. That same LR4 used polys for all series HP caps. I have a bias to use polys for all series caps.
This test (pics below) used a 2nd order XO (from my budget project) and I compared the measured responses for the HP series cap used for the tweeter. The poly cap is a Solen 2x 2.2uF (4.4uf) and the bipolar is Nichicon Muse 4.7uF. The comparable cost for a single 4.7uF is $4 poly and $1 bipolar. The $$ difference grows very quickly for larger values and voltages.
I don't see any significant measurement differences between them and they sound the same to me.
FYI, the Nichicon UES is not meant for crossover networks and dangerous at higher power levels. The Nichicon UDB series is made for crossover networks and might yield better results due to its lower ESR at higher frequency.
This thread has the ESR values for different bipolar capacitors.
Very interesting results.
The bipolar caps would really come into their own when using 4 ohm drivers. I've recently done a crossover design for some 4 ohm SB drivers, and the largest cap was 27uF.
This is the LR4 that used Solen's bipolar caps OmniDirectional - work in progress Same issue, the larger caps (18uf, 27uf) are pricey in a poly.
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