High ESR Effect On Crossover Frequency And Slope ?

[ka7niq]

Ok, lets say we have a 30 year old Mylar Cap that still measures it's rated Capacitance. Now, lets just assume it has high ESR, say from .5 up to maybe 1 ohm ? What does this do to a crossover ? does it shift the crossover frequency UP or Down, does it mess with the slope ?

[DrWho]

The effects of ESR depend on how the capacitor is used in the circuit...

But in both cases, it will cause the slope to become slightly less steep and shift the frequency slightly.

[ka7niq]

The effects of ESR depend on how the capacitor is used in the circuit...

But in both cases, it will cause the slope to become slightly less steep and shift the frequency slightly.

Thanks Mike, will it shift UP or DOWN in crossover frequency

[DrWho]

The lowpass moves lower and the highpass moves higher. I also forgot to mention that the highpass results in some attenuation too.

I went ahead and modelled the behavior of a normal 2kHz butterworth xover into an 8ohm load (purple and teal), and then plotted the behavior of the same xover with 1 ohm of ESR on the capacitor (red and blue):

[DrWho]

And then here's the schematic:

[ka7niq]

And then here's the schematic:

Very Interesting ..... I changed the 36 year old caps all out in my E/V Sentry III's, actually twice, with not good results! Tried several different combo's of new Mylar and electrolytic caps, can't seem to duplicat the magic they once had. So, I have replaced one speaker with all it's old caps Except the 2 uf old mylar on the tweeters, I clipped the leads too short on the old cap, unable to repai it. I listened, seems like the magic is returning. I will go back out there and re do the other speaker. Since the old tweeter caps are unusable, I went to rat shack and got some 2.2 u NPE Caps 20% caps. I figured thes will have ESR perhaps approaching the old 2uf Mylars? They will have to do, for now.I also have enough Motor Run Caps to re do my speakers, but installing them will be a *****.

This is my project for the day Mike. I know in theory, it is bad to use old high ESR caps, and an electrolytic on the ST 350 tweeters in the Sentry III's. But I must trust my ears. Let me go re do the second speaker, and we will see where I am at, as far as sound goes ? I wish I had a crossover schematic for the sentry 3's, it crosses at 600 and 3.5 k, and one slope is 18 db, it uses 3 - 30uf caps, one 17.5 and 1 - 2uf on the tweeter 2 of the 30uf caps are in parallel, be back in a few

[Al Klappenberger]

ka7niq,

Low Q components cause loss in the passband of a filter. This will normally show up as a slope in the passband of the filter as it gets near the passband edge. It seems to be most noticeable at the point of maximum phase shift with frequency change (maximum group delay). The crossover will change slightly, but that's not a major factor. As stopband skirts are normally defined as the number of dB attenuation from the defined passband corner frequency (usually the 3 dB down point), the stopband tends to suffer in relation. The fact is, the attenuation in the deep stopband is not effected much by low Q, only the passband suffers noticeably. So.. The main thing you loose with high ESR components is forward energy going to your drivers. That's why putting god caps with low ESR in a tweeter filter results in a crisper sound. More energy is getting to the tweeter.

Al K.

[ka7niq]

First, Happy Birthday again AL ! I threw the old caps back in, all except for the 36 year old Paktron 2uf Mylar Tweeter cap. I had a new ERSE 2uf Mylar in there, I probably should have left it. With all the old caps back in the Sentry III's, the sound is warm and almost romantic compared to the new Mylar and High Quality ERSE Electrolytics that were in there. I was forced to go to Radio Shack to get a 2.2uf Non Polar Electrolytic, since the old tweeter cap is no longer usable.I wanted a high esr tweeter cap, to duplicate the ESR of the 36 yerar old mylar tweeter cap as close as possible. THIS cap must go! It has almost muffled the ST 350 tweeters! it took the sheen off of cymbals, and the bite out of Trumpets. It is a 2.2 vs the called for 2.0 UF, and a 20 percent vs a 5 percent cap as well. God only knows what it's value is, and it's ESR must be sky high, since it has muffled the tweeters. We measured every one of the 36 year old caps, and they are right on the money, as far as capacitance, ESR is unknown, suspect it may be high. The speakers seem to "want this" AL. I think if I just play with the 2uf tweeter cap, I may be done ? It seems a shame to have all these motor run caps I ordered not get used, but they are a SOB to mount, and make room for. I fear they may be more of the same sound as the ERSE Mylars. Yes, with the new caps, the speakers were more detailed, but they were also far brighter too. Not bright like many Klipsch Speakers, but just a tad too "in your face' for my tastes. IS it possible AL, that over a 36 year period the drivers themselves may have changed a little, and the speakers want these high ESR caps ? As a fellow ham, you are aware we can computer model a Yagi Antenna, and it will yield good performance. But there is no subsitute for tuning an antenna in place. The computer modeling programs are great, they just can't account for every variable. Perhaps the old caps are compensating for my equipment, or room, or perhaps my ears ? Since I put the old caps back in, I love the E/V Sentry III's again, except the performance of the tweeters is crippled by the Radio Shack Electrolytic. I think I will just try a bunch of 2uf tweeter caps, till I get my sound ? The old Paktron 2uf Mylars may be re usable, but my eyes are not so good to re solder leads to them again. I clipped em too short. I am driving my girlfriend crazy, she is bitching all I do is fool with speakers, or on computer. I told her "Honey, I am almost 56, sorry if women are not the priority for me they once were' I offered to buy her a plane ticket back home ! Good Lord, they complain if you are out fishing or hunting, or out in a bar, but when you are home, they complain too ! I just dont understand Women, do they not realize how important it is for us men to have good sound? Geez

[ZAKO]

Just tell her little willy is,nt in nesting mood any more,,,She,l be out there in a flash

[ka7niq]

Just tell her little willy is,nt in nesting mood any more,,,She,l be out there in a flash

Hey Maron, did I ever tell you I picked up some Tannoy's ? Yep, a pair of Tannoy D 50's, the 8 inch dual concentric in a small floor standing cabinet. Musical little bastards they sure are, imaging fools too. Their crossovers are "safe" from me, encased in Epoxy. Quite fond of them I am, no real bass in my 24 by 20 foot room, but there is just "something about" the dual concentric driver. I can see why people are fond of these, can only imagine what the big brothers to these must sound like ?

[DrWho]

You could always throw in your new low ESR caps and then play around with a resistor in series to create the same effect as more ESR. You might also try measuring the actual speaker response to help quantify what you're hearing...

[djk]

Better caps sound better, but may require some adjustment, especially replacing electrolytics.

I first ran into this on some older Thiel speakers. The fix was simple, as DrWho suggests, a small resistor was added.

My crossover box of goodies has two of every mid-value value of cap, inductor, and resistor (with a couple of L-pads thrown in for good measure) offered by Madisound, a couple of dozen clips leads, and an LCR meter that measures Q/ESR. A spectrum analyzer gets me in the ballpark, ±1dB or so, final tuning is always done by ear with music. If the result is more musicality at the sacrifice of 1dB of accuracy, so be it. A lot of audible changes are so small as to defy measurement, on the order of ±1/4dB (calculated).

[ka7niq]

You could always throw in your new low ESR caps and then play around with a resistor in series to create the same effect as more ESR. You might also try measuring the actual speaker response to help quantify what you're hearing...

No measuring equipm,ent Mike, but your idea sounds good. what side of cap does resistor go on ?

[ka7niq]

Better caps sound better, but may require some adjustment, especially replacing electrolytics.

I first ran into this on some older Thiel speakers. The fix was simple, as DrWho suggests, a small resistor was added.

My crossover box of goodies has two of every mid-value value of cap, inductor, and resistor (with a couple of L-pads thrown in for good measure) offered by Madisound, a couple of dozen clips leads, and an LCR meter that measures Q/ESR. A spectrum analyzer gets me in the ballpark, ±1dB or so, final tuning is always done by ear with music. If the result is more musicality at the sacrifice of 1dB of accuracy, so be it. A lot of audible changes are so small as to defy measurement, on the order of ±1/4dB (calculated).

I wonder what wattage this resistor must be ?

[djk]

Unless the resistor is a very high value, a 10W part is usually enough.

[ka7niq]

Ok, on what side of capacitor ?

[DrWho]

Ok, on what side of capacitor ?

It doesn't really matter...just be consistent with it.

[ka7niq]

Ok, on what side of capacitor ?

It doesn't really matter...just be consistent with it.

Shall it be a non inductive resistor,or will it matter ? Or, play with both ?

[DrWho]

Non-inductive

[ka7niq]

Non-inductive

It may not be easy to find non inductive at .25ohms, so what does your cool program say about what a little inductance will do ? Hey Mike, since my speakers are 36 years old, and I think Alnico, could some of the speakers have lost magnetism/efficiency over the years, and the resistive old caps are compensating for this ? The midrange horn is running hotter then I care for with the new caps, just how MUCH resistance can I get away with on a capacitor w/o totally screwing the crossover up ? I still have the old caps, wish I had an ESR meter. They are 36 year old Mylars, except the unknown type 30uf caps are very large black caps with pink end caps, and say NP on them. The caps all measure the called for capacitance, even after 36 years, ESR is unknown. Is there a correlation between added resistance and DB of lost output of a driver ? IOW, will a .5 ohm resistor on the midrange cap attenuate the driver .5 db, more, or less ?