[Sprint]

Hello everyone, hoping those gifted with experience and knowledge of electronics can help spec components needed to build a high pass for my 1970 Dovedale 3 mains.

A little background; My simple setup is a reconditioned and upgraded NAD 3020, driving the Dovedales, and both channels parallel feeding a hi level input to 2x BK XLS200 subwoofers.

It’s a very simple but lovely effective setup, the problem I have is there’s to much db in the 70hz range, from the Dovedales.

I’m completely against any Mini DSP or other modern source modifying, not only because I don’t like messing with the source, but because the input to the subs would be affected too.

So I would like to make 2x 80hz high pass filters for the Dovedales, in the best possible way so as not to muddy them in the process.

The Dovedales are 6 ohm, I’ve attached a diagram of the internal circuits.



Any input and advice much appreciated!

[FullRangeMan]

Hello everyone, hoping those gifted with experience and knowledge of electronics can help spec components needed to build a high pass for my 1970 Dovedale 3 mains.

A little background; My simple setup is a reconditioned and upgraded NAD 3020, driving the Dovedales, and both channels parallel feeding a hi level input to 2x BK XLS200 subwoofers.

It’s a very simple but lovely effective setup, the problem I have is there’s to much db in the 70hz range, from the Dovedales.

I’m completely against any Mini DSP or other modern source modifying, not only because I don’t like messing with the source, but because the input to the subs would be affected too.

So I would like to make 2x 80hz high pass filters for the Dovedales, in the best possible way so as not to muddy them in the process.

The Dovedales are 6 ohm, I’ve attached a diagram of the internal circuits.



Any input and advice much appreciated!

This is a crossover question not a mains line filter for your home electric network as you mentioned in the Starting Block Circle, so the Admin will move this topic to the Lab Circle.

[nlitworld]

So your best bet would be to place the filter between the preamp out and the power amp input since that has the vintage connectors separating each section of the unit. Then, run your subs with line level input from the bypass section of your inline filter. You'd only need to measure the input impedance of the power amp section to know where to match for 80hz crossover. Once you find that impedance value, pop onto https://www.omnicalculator.com/physics/high-pass-filter and plug in values to know what size capacitor.

Required parts would be 3 sets of rca female jacks, two nice caps, two rca cables (3 if you need for subs too), and two small project boxes.

If you were to place a high-pass filter between your amp and speaker, you'd need 330uf of capacitance for an 80hz mark. That's either stupid $$$ money for anything decent, or using hot garbage electrolytic caps in the main signal path. 

Food for thought. Keep us posted what you come up with. Also, don't judge sound until you have like 100hrs funding the capacitors. Good film caps need time to open up and get the wiggles out.

[Sprint]

Hello, thankyou for that very logical and informative response, I spoke to my guy that rebuilt my amp and he said it’s 11Kohm.
So need a 0.18.

Is there a specific brand or source of Cap you’d recommend?

Looking at the schematic on Omni do I just need to plumb the Cap in series on the positive?
Assume the resistor is my amp input.

[Bill Baker]

If you have the original 3020, you can place the capacitor between pre out and main in and power your subs from pre out as well as nlitworl mentioned. You can use a simple Y-connector out from the preamp out to drive the amp and subwoofer. I have a pair of Linton 85s and run high pass filters in our preamp. When removing some of the lower frequencies, the amp will run more efficiently and the speakers will be cleaner in the regions above the filter frequency.