How 2 figure out xover freq of unknown xovers?

[Bull]

got given and have various x overs, but all of them the xover point is unknown.

1st is an active mains plug in RCF high pass filter with RCA outputs for the RCF monitor series [I think 8] anyone know it's cut off point?

2nd is a 12/db octave subwoofer passive xover. How would I work out the xover point?

3rd is 3x 12/db octave 2 way[I think] xovers, with a resistor, cap and inductor.

4th is 2x high quality Link Dynamics 2 way xovers, with 5 caps[polyester type] and 2 inductors per crossover board. I swear that would be a 24/db octave one.

Want to use at least the last ones, so need to know.

Thanks.

 

[Cal Weldon]

Hi Bull,

It will be difficult to analyze the XO points without more info. Are there no numbers on any of the components?

Are you trying to fit an existing XO into a design? That's very hard to do and not recommended. Every XO is matched to the system and can't just be swapped over at will.

A fourth order, 24 dB requires four coils and four caps per board. You have enough components for an 18 dB cut off for the high pass but only a 12dB cut off of the woofer, plus a couple extra caps. Can you draw a schematic and show us a pic?

EDIT: Moved to loudspeakers

 

[Cloth Ears]

Photos of front and back might give us an indication of what sort of set-up they are. But, as Cal said, we really need some figures (numbers) from the components or we're simply guessing (badly).

 

[Ron E]

for a 12dB crossover:

Find the L and C that resonate,
Put L in Henries and C in Farads
e.g 1mH = 0.001 Henries
50uF = 5e-5 Farads

Fc = sqrt(1/(L*C))/(2*pi)

for the example
Fc= sqrt(1/5e-8)/(2*pi) = 712Hz

 

[Bull]

Hi Bull,

It will be difficult to analyze the XO points without more info. Are there no numbers on any of the components?

Are you trying to fit an existing XO into a design? That's very hard to do and not recommended. Every XO is matched to the system and can't just be swapped over at will.

A fourth order, 24 dB requires four coils and four caps per board. You have enough components for an 18 dB cut off for the high pass but only a 12dB cut off of the woofer, plus a couple extra caps. Can you draw a schematic and show us a pic?

EDIT: Moved to loudspeakers

Nope, just want to find it's xover point. To [a] see if I can use it with the enclosures I want to build.
And if I can't, then will know what xover point it has if I need to sell them.

Will dig out my camera tommorrow and take some pics.

Also I don't think I half any inductor measuring equipment.



I just checked my Fluke multimeter, and it doesn't do inductor measuring, a shame. Ain't got an oscilloscope either.
As it's got a capacitor tester, transistor tester and the rest of the normal multimeter type functions though.

My friend thinks I can connect the xover to an amp and drivers and run a low level swept frequency through them with like a freeware signal generator on the PC. And tells me to listen to where the signal starts to roll off.

That seems ok, but I don't recognise very close frequencies to each other to make an accurate guess. I'm not that good at all at recognizing different frequencies apart from random quessing.

If I use the wrong xover in project, it would definatly blow the compression driver if the xover point is too low.

So need an accurate way of testing the unknown xovers.

 

[augerpro]

The true crossover frequency will dependent on the response of the drivers. So knowing the crossover frequency of just the filter is of limited usefulness.

 

[Bull]

The true crossover frequency will dependent on the response of the drivers. So knowing the crossover frequency of just the filter is of limited usefulness.

Well the plan says use a xover point of 1.6khz, 18db/octave.

And a high pass at 200hz.

It's basically a plan for horn loaded mid/high. Will find a suitable bass bin for it, when built.


Drivers I wish to use are the Fane Studio 8M[ Fs 81hz] and Selenium D205Ti [800hz-18khz].
The xover I use might have to built from scratch I just thought.

Selenium D205Ti has an SPL of 108 dB at 1W/1m and 75w rms handling.

Fane Studio 8M has an SPL of 101db at 1W/1m and 100w rms handling.

So definatly some dampening resistors on the HF would be needed.

 

[ZilchLab]

My friend thinks I can connect the xover to an amp and drivers and run a low level swept frequency through them with like a freeware signal generator on the PC. And tells me to listen to where the signal starts to roll off.

Don't hafta listen; use the appropriate load resistors and measure the voltage drives.

First determine what frequency range your Fluke can accurately measure AC from its specs....