Need help with bi-amping

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One of my active bi-amped studio reference monitors has gone out of order.
I am trying to rebuild it from scratch. I bought 2 X TDA7294 power amplifier kits and Power supply units.

But I got stuck at making the 2 way 24dB Linkwitz-Riley Crossover.

The original 2 way 24 dB crossover was tuned at 3kHz( approximately).

I cannot buy the readily available ones online since my bank card does not support international purchase.

I looked at the project 09 page of Rod Elliot. It is difficult for me to calculate and optimize the values.

I looked for other posts on the forum too.

But not very sure on how to advance further.

Any kind help/guidance/ advice/ handholding is much appreciated.

Here is my restoration progress so far:
HYrlQ1C.jpg


Warm regards.
 
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This site allows Sallen/Key filters to be designed to specification: Sallen-Key Low-pass Filter Design Tool
(I link to the low-pass, there's a high pass page too if you look around)

A 4th order Linkwitz/Riley cross over can be conveniently implemented as a cascade of two identical 2nd order Butterworth stages (Q=sqrt(0.5)).

Better still there's an actual circuit at Active Filters
You just need to scale the R's for a different frequency.


The Rod Elliot circuit is basically the same but for 310Hz, that could be easily scaled by 10.
 
This site allows Sallen/Key filters to be designed to specification: Sallen-Key Low-pass Filter Design Tool
(I link to the low-pass, there's a high pass page too if you look around)
Thank you a ton! I checked both the low-pass and high-pass design tools. I decided to set the crossover frequency at 2900Hz and found this can be achieved with commonly available values like R1, R2= 5.6K and C1,C2 = 0.01uF.
Could you kindly confirm if it did it right or not ?

A 4th order Linkwitz/Riley cross over can be conveniently implemented as a cascade of two identical 2nd order Butterworth stages (Q=sqrt(0.5)).
Better still there's an actual circuit at Active Filters
You just need to scale the R's for a different frequency.

I will check out more about cascading those 12 dB filters and report you back with my findings.

The Rod Elliot circuit is basically the same but for 310Hz, that could be easily scaled by 10.
I need to learn more about these up-scaling. I saw in the documentation of the readily available kits on the international shops that they mentioned this scaling by 10 option. Could you kindly elaborate on this?

I posted two images in the attachments about my findings and progress. Could you kindly have a look at them and correct me if needed ?
 

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On his website, Rod Elliott has a downloadable calculator for his crossovers;
https://sound-au.com/software/esp-lr13.exe

I used it for the P09s I bought and use.

Thank you so much!
I tried that as per your recommendation and obtained some values for my desired x-over frequency @ 2900Hz. I have some confusion which I mentioned in that image. Is 2900Hz a good value or I should go up a bit higher? But my concern is the availability of the components. Kindly have a look at the attachments of this post and my previous post.
 

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I also need a good, user-friendly and free software to draw and simulate the circuit of this x-over project and then make the PCB layout with onboard connectors and sockets so that I can use the toner transfer method to make my own PCB at home.

Could you kindly recommend one?
 
This site allows Sallen/Key filters to be designed to specification: Sallen-Key Low-pass Filter Design Tool
(I link to the low-pass, there's a high pass page too if you look around)

I was checking out the Sallen-Key Filters at this page :
(Sample)Sallen-Key Low-pass Filter Design Tool - Result -

Here is what I got :
1. Sallen-Key Low-pass Filter:
Crossover Frequency = 2900Hz
R1, R2 = 5.6K
C1, C2 = 0.01uf

2. Sallen-Key High-pass Filter:
Crossover Frequency = 2900Hz
R1, R2 = 5.6K
C1, C2 = 0.01uf

In both the cases I didn't touch the following parameters.
Q Factor = 0.707
Damping ratio = 1

Could you kindly check at your convenience if it is okay or not?
 
………….
Better still there's an actual circuit at Active Filters
You just need to scale the R's for a different frequency.


The Rod Elliot circuit is basically the same but for 310Hz, that could be easily scaled by 10.

I used Rod Elliot's Cross Over Calculator to obtain the R values in the Linkwitzlab actual circuit.
Here is what I got:

Crossover Frequency = 3000Hz


1. Low Pass Filter :
R = 1.71K
C = 22nF
2C = 44nF

2. High Pass Filter :
R = 1.71K
2R = 3.41K
C = 22nF

Kindly check this too and give your much needed valuable advice.
 
In fact that was my first choice.
But I faced a couple of issues.
1. My bank card doesn't support international purchase.
2. Even if I appeal to someone possessing an international credit bank card ( which is very difficult to find in my vicinity) in my country to do the purchase for me it will cost me a real lot.
The original price on the xkitz website is some 44.95 USD. If I import a single piece it will cost me some 70 USD, if not more, including Basic Custom Duty, CESS, International Goods and Services Tax and some other hidden taxes plus some profit for the person who purchased it for me. I am not that rich. :D

So not an easy thing to do.

And once a person listens to an active system and realizes its potential, he/she usually will never go back to the passive system. Long ago I read an article by Rod Elliot regarding bi-amping and attempted some with readily available circuits and I can feel that that was the wisest investment of time and money on my part to build my active 3 way system with LM3886TF.

When my studio reference monitor died, I thought it would be good idea to learn from you all and build that cross-over at home so that I can fix the other one (which is still working ) when it is needed. For me, with my limited knowledge, this crossover is the trickiest part. Rest of the circuitry can easily be manageable, imho. :)
 
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One of my active bi-amped studio reference monitors has gone out of order.
I am trying to rebuild it from scratch. I bought 2 X TDA7294 power amplifier kits and Power supply units.

But I got stuck at making the 2 way 24dB Linkwitz-Riley Crossover.

The original 2 way 24 dB crossover was tuned at 3kHz( approximately).

I cannot buy the readily available ones online since my bank card does not support international purchase.

I looked at the project 09 page of Rod Elliot. It is difficult for me to calculate and optimize the values.

I looked for other posts on the forum too.

But not very sure on how to advance further.

Any kind help/guidance/ advice/ handholding is much appreciated.

Here is my restoration progress so far:
HYrlQ1C.jpg


Warm regards.

You really should rebuild BOTH speakers.
The chances to have a good match between them, if you rebuild only ONE, is close to zero.
 
If you are looking for a simple to build and easy to tune crossover, the circuit below might just do your job. But do note this is not a production circuit, it will need a bit of debugging to get it perfect.

The woofer out is an active low pass filter.
The tweeter out is developed by subtracting the woofer out from the input.
The overall circuit is unity gain.

To change the crossover frequency simply change C3 and C4 keeping them equal.

Frequency response curves are in the lower panel.

Note that depending on driver time alignment it might be necessary to reverse the tweeter connections after amplification.


The LTSpice file is included.
 

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