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Crossover reverse calculation?

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Young Croc
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    Posted: 23 November 2014 at 12:31pm
found a random homemade crossover, seems to be bi-amped, luckily its labelled (hand written on the wodden board), can somebody please tell what freq and slopes its set to, found lots of crossover calculators online but none that will reverse the calculation, thanks in advance Smile

circuit 1. UF 0.82 - MH 0.10

circuit 2. UF 8.2 - MH 2.20
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 23 November 2014 at 2:10pm
Formula is:  f = 1/(2*pi*(square root(L*C))

Simple.  Smile


So I get   1:  17575Hz

               2:   1185Hz


EDIT: Slopes will be 2nd order, ie 12dB/octave.

RE-EDIT:  Ooops - just realised I´d misread the values in (1).   Embarrassed





Edited by Earplug - 23 November 2014 at 2:30pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 23 November 2014 at 2:13pm
It would depend entirely on the speakers it was connected to. The impedance of the driver terminates the filter and defines its turnover frequency and damping.

Assuming an 8 ohm speaker, the 8.2 uf/2.2mH combo lowpass filters somewhere around 1000-1500Hz with a 12dB slope. Closest match I could get is 2nd order Bessel for a 10 ohm termination which would be a reasonable impedance to expect at 1200Hz for an average hi-fi woofer.

The other combo would highpass filter somewhere around 10000-15000Hz for an 8 ohm driver. SO not sure why they are on the same board. 

There are free circuit simulation websites where you could draw out the circuit and then examine its frequency response.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 23 November 2014 at 3:02pm
Ok, just put my brain in gear a bit...  Embarrassed

Circuit (1) is a strange one, but could be for a xover between a 16ohm tweeter and 8 ohm 2", xover point around 12kHz.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tweeter_Box Quote  Post ReplyReply Direct Link To This Post Posted: 24 November 2014 at 12:21pm
thanks guys Big smile

i tried em yesterday n it would seem one is a low pass (pretty nice sounding actually) using a 600v cap, n the other is a veeery high pass using a 400v cap, dunno how to measure the coils specs though,
the high pass only gave real high sizle when put on a 1" but sounded good on a 2" (toned down the vocaly bits nicely)


Originally posted by studio45 studio45 wrote:


There are free circuit simulation websites where you could draw out the circuit and then examine its frequency response.


can you recomend a site please , had a look on my fone n couldnt find much Confused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 24 November 2014 at 11:50pm
http://www.speakerwizard.co.uk/category/speaker-design/2nd-order-crossover-calculator/
 
Im sure you'll figure out where to put the numbers, once you have worked out which component is which on the diagram, it will do the reverse calculation..
 
but your numbers seem weird, if they are correct, it looks like they are putting in a massive hole in the response. If your Compression Drive is around 12-15dB more sensitive than the woofer, that will compensate for some of the hole, but effectively give you about 12-15 db boost around 15-20 Khz
 
If there are no attenuation resistors on the HF, this may be part of the design. Bit crude, but it works to give the Boom Tsss disco sound without much mid-range. Kind of creating the smiley face EQ without a graphic.


Edited by Andy Kos - 24 November 2014 at 11:58pm
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2014 at 12:20pm
Originally posted by Andy Kos Andy Kos wrote:

but your numbers seem weird, if they are correct, it looks like they are putting in a massive hole in the response. If your Compression Drive is around 12-15dB more sensitive than the woofer, that will compensate for some of the hole, but effectively give you about 12-15 db boost around 15-20 Khz
 
If there are no attenuation resistors on the HF, this may be part of the design. Bit crude, but it works to give the Boom Tsss disco sound without much mid-range. Kind of creating the smiley face EQ without a graphic.
 
CD EQ for a driver/horn combo with quite a sharp HF rolloff?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2014 at 1:39pm
Originally posted by DMorison DMorison wrote:

Originally posted by Andy Kos Andy Kos wrote:

but your numbers seem weird, if they are correct, it looks like they are putting in a massive hole in the response. If your Compression Drive is around 12-15dB more sensitive than the woofer, that will compensate for some of the hole, but effectively give you about 12-15 db boost around 15-20 Khz
 
If there are no attenuation resistors on the HF, this may be part of the design. Bit crude, but it works to give the Boom Tsss disco sound without much mid-range. Kind of creating the smiley face EQ without a graphic.
 
CD EQ for a driver/horn combo with quite a sharp HF rolloff?
It could well be that, but quite an extreme one looking at the numbers.
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KidCreole Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2014 at 2:41pm
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Shouldn't the title be. Reverse engineering? What anies cabinets are you cloning now
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andy Kos Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2014 at 2:43pm
Originally posted by Tweeter_Box Tweeter_Box wrote:

luckily its labelled (hand written on the wodden board),
 
Very few manufacturers write inductor values on wooden boards...
just a guy with a warehouse and a few speakers... www.bluearan.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tweeter_Box Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2014 at 4:16pm
Originally posted by Andy Kos Andy Kos wrote:

http://www.speakerwizard.co.uk/category/speaker-design/2nd-order-crossover-calculator/
 
Im sure you'll figure out where to put the numbers, once you have worked out which component is which on the diagram, it will do the reverse calculation..
 
but your numbers seem weird, if they are correct, it looks like they are putting in a massive hole in the response. If your Compression Drive is around 12-15dB more sensitive than the woofer, that will compensate for some of the hole, but effectively give you about 12-15 db boost around 15-20 Khz
 
If there are no attenuation resistors on the HF, this may be part of the design. Bit crude, but it works to give the Boom Tsss disco sound without much mid-range. Kind of creating the smiley face EQ without a graphic.


thanks Andy Star

no attenuation on the board, probs coz its bi amped Confused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tweeter_Box Quote  Post ReplyReply Direct Link To This Post Posted: 25 November 2014 at 4:20pm
Originally posted by Andy Kos Andy Kos wrote:

Originally posted by Tweeter_Box Tweeter_Box wrote:

luckily its labelled (hand written on the wodden board),
 
Very few manufacturers write inductor values on wooden boards...


soldering and glue makes me assume its home made, values hand written in pencil on the wood, got 2 diff martin crossovers here to mess around with now aswell, pretty sure one of them was out of the phillishaves i used to own, hopefully i can find some use for them
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