large value capacitors for chr 70 high pass

[Bill poster]

Chr 70 crossed at 350-400 hz.. can't find much at those values! What would you recommend?

[Andrew Eckhardt]

This might be useful:

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

[Bill poster]

Originally Posted by Andrew Eckhardt

This might be useful:

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

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]

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]

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]

Originally Posted by Bill poster

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]

Originally Posted by chrisb

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?

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]

Originally Posted by Bill poster

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?

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]

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]

Originally Posted by kipman725

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