Crossover capacitor choice

Crossover capacitor choise

I want to upgrade the capacitors in my crossover network.

After searching over the net I found that Auricaps are one of the better capacitors for crossover networks.
For the tweeter part in my crossover are two capacitors in the signal path. So it will make sense to choose expensive Auricap capasitors.

But in the woofer part of the crossover is a 12 micro farad capacitor in parallel over the woofer (with a 1 ohm serial resistor, I don't know what the function of this resistor is). This means that the capacitor in not in the signal path.

Does make it sense to choose also an expensive capasitor for the woofer part in de crossover? :hot:
 
heartfelt advice

Jonasa,
You should test and listen to various capacitors before you decide on a costly upgrade. Also, you should treat the replacement of "old" caps as a different issue than an upgrade.

I felt that I became a member of a club when I included costly caps in my x-over. Later I participated in a double-blind test of caps and could not tell the difference between mylar and Solen metalized polypropylene.

You may be able to hear the difference...some (about 10%) could hear the difference. Here is a link to one such discussion:

http://www.pesupport.com/cgi-bin/config.pl?read=223650

If you really investigate this consider a variety of combinations:
electrolytic with poly bypass
mylar
polypropylene film, metalised(standard grade)
polyester film, metalised
and the poly film with metal foil

Now, to answer your question. Placing more emphasis on the higher frequency x-over points is wise IMHO. Let us know what you find.

Regards
 

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Re: Crossover capacitor choise

Jonasa said:
Does make it sense to choose also an expensive capasitor for the woofer part in de crossover? :hot:

I tried Auricaps in my tweeter crossover and I think you've made a great choice. I could hear a siginificant difference between Auricaps and Solen PPE.

Upgrading the cap in the woofer conjugate circuit OTOH is not so clear. If the existing cap is an electrolytic, an upgrade would be a good idea. Personally I would use a Solen PPE, because I think the effect of an Auricap would be subtle and a 12uF Auri is very expensive.
 
I both agree and disagree.
Being a born skeptic I firmly held there was little audible difference between Cap type/brands,
at least inna Crossover.. (in Coupling the differences are not Subtle:)
Well.. after a couple of years of 'dicking' about with crossovwers.. i'm forced to change my views.
There IS audible difference.. but it's a correleation to the quality of the Drivers themselves.. ones that are far more capable than the average ..do.. exhibit a sonic difference. with different caps... sometimes this is rather Obvious, sometimes it's v subtle, or possibly nonexistant :)
Having said all that ..Solens are a V good starting Point.. buy 'em install them, then listen.. for weeks ,not days, let alone hours.... then decide if you want to risk more (sometimes Exotic Caps sound noticeably inferior to Solens :).
Be Aware though that this is "voicing" territory.. essential for 'getting' it eactly right' for yr tastes. But that's an adventure best saved for later in your learning curve
Yes .. you could just bypass the electrolytics but Bypassed Caps give Odd and often unpleasant Audible effects.. Spend the Few $ and avoid the issue entirely.
Seriously suggest you Do Not fool with the Xover design.. unless you have significant knowledge/experiences.. that's a really tough road.
 
Crossover

Many thanks to all for the reply's.
So I can conclude that the signal path to the tweeter is more important but only good listening test will make the final choise.
Many people don't hear any difference but it depents also of your configuration.
The capacitor for the woofer is less important but it is possible that in some cases a special (expensive) capacitor can improve sound.

Does anyone knows what the function is of a resistor in serial with the capacitor for the woofer? It is just a second order low pass filter.
 

jomor

Member
2004-02-20 1:36 pm
Athens
Re: Crossover

Jonasa said:

Does anyone knows what the function is of a resistor in serial with the capacitor for the woofer? It is just a second order low pass filter.

If you mean something like the example above, then there are two cases:

1) if the resistor has a low value ( 0.22 ohm - 3 ohm ) it is used to alter the Q of the low pass filter and THE PHASE of the woofer, to match the tweeter's phase. Its a great trick to match the phases of both drivers in the crossover region.

2) if the resistor has a higher value ( 5 ohm - 15 ohm ), the RC in parallel with the driver is called a Zobel network and its used to compensate the driver's impedance rise. Thus the impedance shown to the low pass filter gets flattened and the filter works as it is supposed to.



[IMGDEAD]http://www.avforum.gr/uplds/6389_example.gif[/IMGDEAD]


About capacitor choice, whoever chooses electrolytic caps for crossovers commits a crime. These caps have large ESR, they have variable capacitance with frequency and variable capacitance with time (changes after some years of use).
The only reason that the manufacturers choose them for their products is their extremely low cost. Polypropylene caps are recommended for crossover usage, especially to be in the signal path (tweeter). You can put MKT caps in the woofer's filter, they re not as good as the MKP (polypropylene) but they re far far better than the electrolytics.
 
Re schematic

This is a nice schematic of the woofer low pass filter.
The resistor in my case is 1 ohm. So the function is to correct the phase.
Does the resistor have an infuence on the resonance or the -3 dB frequentie of the filter?
Where comes the R in the formula. 1/2.pie.square root(L.C)?

I don't think it make sense to change the coil. One question:
When you place two coils in parallel then the resistance is divided by 2, but has it also disadvantages? Ofcourse you must turn the coils 90 degrees so that the magnetic field don't influence each other.
 
Re: Good quality resistors

Jonasa said:
I don't think it make sense to change the coil.

If your coils are iron or steel cored, then it definitely makes sense to change them for air cores. But you need to consider the DCR of the existing coil. The Solen hepta-litz are pricey but amazingly good.


Jonasa said:
Does anyone know where I can find non inductive resistors of first class quality. Is there a special type or name for it?:clown:

Caddock metal films sound best, but Mills are very good. Both are available at Parts Connexion or Michael Percy.
 

jomor

Member
2004-02-20 1:36 pm
Athens
Re: Re schematic

Jonasa said:
This is a nice schematic of the woofer low pass filter.
The resistor in my case is 1 ohm. So the function is to correct the phase.
Does the resistor have an infuence on the resonance or the -3 dB frequentie of the filter?

Yes it does.. The resistor actually determines how much the capacitor participates in the low pass filter.
 
mix and match

Some people add the expensive (low mfd) cap in parellel with the lower cost (higher mfd) one. Audio express had an article with tests about this. My guess is that the better cap picks up where the lower cost cap acts like an inductor? But the dielectric hash would still be there from the lower cost cap....

-Linc
 
Re: mix and match

lcholke said:
Some people add the expensive (low mfd) cap in parellel with the lower cost (higher mfd) one. Audio express had an article with tests about this.

I agree with what Bare said earlier in this thread:

"Bypassed Caps give Odd and often unpleasant Audible effects.'

Bypassing can work, but you need lots of caps on hand to find a suitable combination. I never found a combo that couldn't be beaten by a single high quality cap.
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
Re: Re: mix and match

audiobomber said:


I agree with what Bare said earlier in this thread:

"Bypassed Caps give Odd and often unpleasant Audible effects.'

Bypassing can work, but you need lots of caps on hand to find a suitable combination. I never found a combo that couldn't be beaten by a single high quality cap.
You got one more vote on this. Especially in speaker application. The high frequencies sound like they have more harmonics that the original instrument.