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Lynx4

Crossover help

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The  impedance ( plus phase  )  correction circuit, consisting  of the 4.5 ohm resistor  in series with the 36 mFd capacitor needs to be connected  across the bass speaker terminals. Put another way, the speaker positive terminal should go to the junction of the 0.3mH inductor  with the  9.4mFd capacitor    (and the L.H. point of the 4.5 ohm resistor).

The attenuator pad  needs to be shifted to a position after the  capacitor inductor junction. To clarify this, the 1.3 ohm resistor connects from that junction to the ' top' terminal of the tweeter and the 10 ohm resistor is connected across the neg. and positive terminals of the tweeter. It should be noted that it is normal for second order crossovers  ( two-way)   to have  the tweeter connected out of phase with the bass section.  I believe your crossover cct. does this , presuming 1 is the positive input and 2 is the negative return terminal 

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1 hour ago, Lynx4 said:

Sorry I'm not very smart I guess lol.

You'll get there.   A simulator makes it easy to tinker, but doing a good original design takes a lot of experience.

 

Here's how the impedance correction bit of the woofer needs to be (approx values).    ie.  Both parts across the driver (in series with each other)

 

See how it flattens the impedance out at higher frequencies.

This means that if you add a "textbook" crossover filter (which is designed to work on constant impedance) that it will work as expected.

 

As mentioned earlier, it can often be simplified by combining elements of the impedance correct and XO.... but don't worry about that for now.

 

image.thumb.png.98bb529155ce2feca0ee9565727c5ce7.png

 

 

 

Probably the best advice I can give, is don't fall into the trap of adding parts tinkering to get the response you want, without also looking at the impedance.   You want to keep the impedance generally either high, or flat .... if it both low, and with peaks and dips, then it's probably bad.

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10 hours ago, davewantsmoore said:

You'll get there.   A simulator makes it easy to tinker, but doing a good original design takes a lot of experience.

 

Here's how the impedance correction bit of the woofer needs to be (approx values).    ie.  Both parts across the driver (in series with each other)

 

See how it flattens the impedance out at higher frequencies.

This means that if you add a "textbook" crossover filter (which is designed to work on constant impedance) that it will work as expected.

 

As mentioned earlier, it can often be simplified by combining elements of the impedance correct and XO.... but don't worry about that for now.

 

image.thumb.png.98bb529155ce2feca0ee9565727c5ce7.png

 

 

 

Probably the best advice I can give, is don't fall into the trap of adding parts tinkering to get the response you want, without also looking at the impedance.   You want to keep the impedance generally either high, or flat .... if it both low, and with peaks and dips, then it's probably bad.

Ok ok I have done this now I think only issue is my SIM won't allow me to place resistor on the other side of the capacitor for the correction. This is what I'm looking at now. Still have a spike in impedance at the top end of frequency is this the crossover network? To me it's looking good and seems to work? 

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It does not matter which way, the impedance correction network  is connected to the bass speaker terminals. However you have an error in the placement of the tweeter attenuation pad.

The inductor should be shifted to connect between the 9.4 mFd capacitor and the return line ( tweeter negative ). The attenuator 'L' pad is for the tweeter to drop  its' sensitivity to  match that of the bass speaker while  keeping the impedance at  4 ohm throughout the crossover region. It can  only  be connected at the tweeter  for it to work as intended.

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3 hours ago, VanArn said:

It does not matter which way, the impedance correction network  is connected to the bass speaker terminals. However you have an error in the placement of the tweeter attenuation pad.

The inductor should be shifted to connect between the 9.4 mFd capacitor and the return line ( tweeter negative ). The attenuator 'L' pad is for the tweeter to drop  its' sensitivity to  match that of the bass speaker while  keeping the impedance at  4 ohm throughout the crossover region. It can  only  be connected at the tweeter  for it to work as intended.

So should the L pad go before or after the crossover (capacitor and Inductor) 

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 The 'L' pad is fitted after the  crossover components. 

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1 hour ago, VanArn said:

 The 'L' pad is fitted after the  crossover components. 

Awesome so this looks 100% better to me at least. Would you agree?

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  Bravo, Lynx4!

   The impedance curve is what I would expect of a crossover designed to suit specific speaker units. In this case the manufacturer's data has been relied on and  this information can be inaccurate  as there can be  production changes and material variability can  also effect results.  It is a good starting point for your speaker build project .

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3 minutes ago, VanArn said:

  Bravo, Lynx4!

   The impedance curve is what I would expect of a crossover designed to suit specific speaker units. In this case the manufacturer's data has been relied on and  this information can be inaccurate  as there can be  production changes and material variability can  also effect results.  It is a good starting point for your speaker build project .

Now the only trouble is finding parts to suit i have tried to match everything up best I could but it has slightly changed the impedance will this be much of an effect? Or would it be alright?

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For prototyping a speaker crossover, especially when you have access to many components, the values can be tightly controlled by selection with the aid of an RLC meter . The better the instrument, the tighter  the  tolerance limits for the crossover network . If you are prepared to buy a few extra resistors, it is possible to make up or select from a batch, an exact match (at least to within 5% or better) of the calculated  design values.  For example, two 2.7 ohm resistors in parallel can be used to make up the 1.3 ohm value and you can use the lower cost 5 watt wire wound types , which should be cheaper than a 10 watt rated resistor.  The 4.5 ohm resistor can be made up of  10 and 8.2 ohm resistors in parallel and again the 5 watt wire wound types can be used.The 9.4 mFd capacitors can be made up of two 4.7 mFd caps. connected in parallel (Polypropylene capacitors of at least  a 250 volt DC rating).  I would prefer the inductors to have a lower DC resistance ,but this would mean a heavier gauge wire and of course, a higher cost.

What components do you have already ? It is  a simple task to adjust  to other values by the addition of other parts as shown in the  forgoing discussion.

 In any case, using the values that are shown in your schematic are  very close and the results may not be distinguishable from a more  rigorous assembly.

Edited by VanArn
additional material

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4 hours ago, VanArn said:

  Bravo, Lynx4!

   The impedance curve is what I would expect of a crossover designed to suit specific speaker units. In this case the manufacturer's data has been relied on and  this information can be inaccurate  as there can be  production changes and material variability can  also effect results.  It is a good starting point for your speaker build project .

... and the biggest issue, is that it doesn't take into account the response on the intended cabinet shape.... everything > 1 khz is going to look a lot different when mounted on a small box, vs the (assumed) IEC baffle or similar that the datasheet measurements were done on.

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That's alright I'm not after an audiophile grade set of bookshelfs this was just a project to introduce myself into the world and already I have learnt a tone thanks to all you guys helping out I can not thank enough! 🥰

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2 hours ago, VanArn said:

For prototyping a speaker crossover, especially when you have access to many components, the values can be tightly controlled by selection with the aid of an RLC meter . The better the instrument, the tighter  the  tolerance limits for the crossover network . If you are prepared to buy a few extra resistors, it is possible to make up or select from a batch, an exact match (at least to within 5% or better) of the calculated  design values.  For example, two 2.7 ohm resistors in parallel can be bused to make up the 1.3 ohm value and you can use the lower cost 5 watt wire wound types , which should be cheaper than a 10 watt rated resistor.  The 4.5 ohm resistor can be made up of  10 and 8.2 ohm resistors in parallel and again the 5 watt wire wound types can be used.The 9.4 mFd capacitors can be made up of two 4.7 mFd caps. connected in parallel (Polypropylene capacitors of at least  a 250 volt DC rating).  I would prefer the inductors to have a lower DC resistance ,but this would mean a heavier gauge wire and of course, a higher cost.

What components do you have already ? It is  a simple task to adjust  to other values by the addition of other parts as shown in the  forgoing discussion.

 In any case, using the values that are shown in your schematic are  very close and the results may not be distinguishable from a more  rigorous assembly.

That was the other way I was thinking but space as well as cost is an issue already with the componates listed in the above crossover I'm totalling about 100bucks and I'I'nmot chasing something that is mind blowing just a good sound in a great looking cabinet. Once I have more experience and knowledge behind me then I'll probably attempt to make great sounding set of speakers but most likely a few years away as I do have alot to learn still! Haha. 

I think I'll go ahead and purchase what I have now at least then I should have some alright sounding bookshelfs by the weekend. 

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