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-   -   large value capacitors for chr 70 high pass (http://www.diyaudio.com/forums/markaudio/188220-large-value-capacitors-chr-70-high-pass.html)

Bill poster 1st May 2011 05:54 PM

large value capacitors for chr 70 high pass
 
Chr 70 crossed at 350-400 hz.. can't find much at those values! What would you recommend?

Andrew Eckhardt 1st May 2011 06:01 PM

This might be useful:

Passive Crossover Design Equations Formulas Calculator - Two Way First Order Network Butterworth

Bill poster 1st May 2011 11:21 PM

Quote:

Originally Posted by Andrew Eckhardt (Post 2557941)

Thanks. I've got this result.
C1 = 5.3E-5 farads (so I need a cap value of 5.3?)
L1 = 0.0033970276008493 henries



Excuse my ignorance but with the butterworth diagram that means no bi wiring?

Andrew Eckhardt 2nd May 2011 12:08 AM

5.3e-5=53e-6= 56uF.

You can bi-wire, not that it will make a difference anything like a well tuned crossover. The diagram just shows the high and low pass tapped on to the usual single feed.

For tuning pick off the driver impedance from the published or measured curves at the crossover frequency. Buy some slightly undersized caps for the main unit and a few smaller values to parallel on if needed. Same for the inductor, only series to increase value. You can rerun calculations at different turnover points to get a smarter idea about what values to buy..

Bill poster 2nd May 2011 01:00 AM

Thanks for the sensible advice.
Yes, thats the figure I got on the Erse site, I thought I'd made a mistake. I'm assuming the ohm inputs are the overall driver rating and not the ohm level at point of crossover?

so that value is going to be expensive if i choose a decent cap..:(

chrisb 2nd May 2011 09:26 PM

Quote:

Originally Posted by Bill poster (Post 2558285)
Thanks for the sensible advice.
Yes, thats the figure I got on the Erse site, I thought I'd made a mistake. I'm assuming the ohm inputs are the overall driver rating and not the ohm level at point of crossover?

so that value is going to be expensive if i choose a decent cap..:(


Passive line level XO and active start to look really attractive when parts for speaker level XO cost more than the drivers

TLS.org | Passive Line-Level Crossover

Bill poster 2nd May 2011 10:34 PM

Quote:

Originally Posted by chrisb (Post 2559324)
Passive line level XO and active start to look really attractive when parts for speaker level XO cost more than the drivers

TLS.org | Passive Line-Level Crossover

chris, I'm looking at the link .. for me anything like this is..well, its a bit like the swedish chef making a pastilla

could you explain it in very simple terms?:o

btw I was thinking to either go for pulse x's (true film and foil 50uf caps are crazy prices)or try a big fat industrial oil type capacitor. both are inexpensive and it might be interesting to see which is preferable with the alpair. cd I bypass with a nice low value cap if needed?

chrisb 3rd May 2011 04:59 PM

Quote:

Originally Posted by Bill poster (Post 2559375)
chris, I'm looking at the link .. for me anything like this is..well, its a bit like the swedish chef making a pastilla

could you explain it in very simple terms?:o

btw I was thinking to either go for pulse x's (true film and foil 50uf caps are crazy prices)or try a big fat industrial oil type capacitor. both are inexpensive and it might be interesting to see which is preferable with the alpair. cd I bypass with a nice low value cap if needed?


well if you're anything like me, even an explanation in simple enough terms that I fool myself that I understand it will soon evaporate from my memory

this type of filter uses the amplifiers' input impedance as one of the formula's operands, any changes in amps might require new parts values

however, there is a calculator included - you enter the amp's input impedance and desired XO frequency, and it does the rest



http://homepage.mac.com/planet10/TLS...ulator.xls.zip

FWIW, the calculated parts are small enough that they can easily be installed at the amp's input jacks - I did exactly that about 10 years ago during some mods to a pair of Decware Zen C amps for a simple 2 way active system - one was filtered LP and the other HP

This particular model had 2 pairs of RCAs and a toggle switch for adjusting the bias of driver tube by adding cathode load resistors. It was easy to re-purpose these parts to allow for bypass of the input filters to run full range.

Worked like a charm, and without getting silly exotic, the cost of parts for the 2 amps was under $50.

kipman725 18th May 2011 03:38 PM

Just use 4*56uf Electrolitics in non polarised confiiguration. Make sure they are low esr >0.5ohm and >50V rating. Works fine don't belive that just because a signal is an audio waveform capacitors stop working corectly. Total cost <2$ so worth trying.

chrisb 18th May 2011 05:08 PM

Quote:

Originally Posted by kipman725 (Post 2575986)
Just use 4*56uf Electrolitics in non polarised confiiguration. Make sure they are low esr >0.5ohm and >50V rating. Works fine don't belive that just because a signal is an audio waveform capacitors stop working corectly. Total cost <2$ so worth trying.



respectfully - certainly valid to test for optimal C value, but I don't believe the difference wouldn't be audible between cheap ELs and decent film types when used at speaker level


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