PLLXO (v AXO v PXO) benefits/ Model?

[rick57]

If you go active xo (my base line thinking), you can use the very cost effective gainclones (refer the Solid State forum).

I’m just about to start a (number of) speaker projects, starting with modest components in a passive 2 way as quick training wheels, and by end of year, the real goal of a Linkwitz Phoenix based/ thylantar type updated active 3-way using eg ribbons & PHL.
(At this stage, am thinking of Linkwitz 4th order for them, but by then maybe series xo).

The advantages/ costs of AXO are well known.

For PXO, Speaker Workshop can be used.

But PLLXO:
Searching Passive AND line AND level AND crossovers
Didn’t yield much

What is it? Cost/ benefits? How to model? What speakers use it?

TIA

[rick57]

Marchand claim for their kit:
http://www.marchandelec.com/xm46.htm
"noise generated by the crossover is much lover than for the electronic crossovers"

and in a Maggie:
http://www.audioasylum.com/forums/mu...ges/12885.html
"clear improvement in resolution"

and the one and only Linkwitz at
http://www.linkwitzlab.com/proto.htm
"The disadvantages of this solution are
1) a high insertion loss, and
2) the exact transfer function can only be approximated"
I wonder what that means?

[peterr]

Look here PLLXO for the basics.

[vdi_nenna]

Look here PLLXO for the basics.

I don't get the calculations. 1 / 2*Pi*F*R1=C1

Going for 1st order- F=2300hz, 5K=R1

What size is C1 expected to be?

2*3.14*2300*5000= 72220000

1 / 72220000= 1.3846579894765992799778454721684e-8

C1 is 1.3846579894765992799778454721684e-8

How does that convert into nF or uF? Am I not calculating this correctly?

Thannks,

Vince

[Davey]

That's capacitance in farads. Move the decimal point nine places to convert from farads to nanofarads. Your calculation is correct and yields a result 13.8 nF.

That's an OLD thread you replied to.

Dave.

[vdi_nenna]

Thanks Dave!

Old thread, but yielded results. I'm sure someone else will need it eventually!

Thanks!

Vince

[vdi_nenna]

Sorry. I spoke too soon. Which way do you move the decimal point?
I tried moving it both direction and converting it to nF, but the numbers in the examples don't match.

Still don't understand how you get 13.8 nF from 1.3846579894765992799778454721684e-8 Farads. Are you converting the Farads to a real number first, then to nF?

Don't mean to be thick, I'm just not good at math.

[planet10]

a nF is 1 x 10^-9 farads. so 1.38x10^-8 F = 13.8 x10^0 nF = 13.8 nF

The advantages of PLLXO are, simplicity, cost, and no added active devices.

Disadvantages are limited set of slopes and -- in the case of the low pass, insertion loss. In the case of a 2nd order HP, one has to be very concerned with the input impedance of the power amplifier (usually needs to be 50k or greater)

In the simpliest HP case, with as an example your gainclone, a 1st order PLLXO can be executed simply by appropriately decreasing the size of the unput coupling capacitor.

dave

[vdi_nenna]

On a 2 way, 2nd order passive XO, to adjust levels where would you place a pot?
I was thinking 5k at the outputs of the passive XO. Yes/No?

The amps are 22k and 100k at the input.

Thanks,

vince

[planet10]

You need to have a gain control on at least one of the power amplifiers (the one that needs turning down to be at the right level)

dave