Advice for a RLA-inspired crossover

[efinque]

Hello DJF,

during the cold weather I came up with an idea of building a RLA-inspired crossover.

Now, I have previous experience of building one, it was a 2-band with mono sub out and a compressor in the LF. It had 2nd order RC filters and the resistors were also sweepable.





But I scrapped it for parts and built a DJ mixer instead.

Now, afaik the original RLA unit had RCA in/out, active 24db/oct filters and a fullrange "mid" band. I saw one modded with XLR inputs/outputs on Reverb.

I envisioned mine to be 1RU with mono 6,3mm jacks (unbalanced) powered by SMPS and have first order filters. The "mid" band would be fullrange as in the original unit. It would also have a preamp section. The LF freq would be 150-200Hz and the HF somewhere around 1-1,5kHz.

I already ordered the parts and they should arrive tomorrow if everything goes well, including an assortment of resistors/capacitors so I can experiment with different values.

Any thoughts?

-ef

[KLH]

Woah. That's amazing. Unfortunately I'm not qualified to give an opinion on this as I've not used an outboard crossover.

[efinque]

Woah. That's amazing.

Thanks!

The parts arrived today, here's what I got so far.



There's the inputs and the preamps on the top left, top right is the DC in and a fusebox. Near the front panel is the splitter for the frequency bands.

[efinque]

Here's a pic with the potentiometers in place.



I've yet to wire the outputs.

[Alex Murphy]

That's not bad, I notice you have loads of space left unused, do you have any sort of expansion plans? Those two boards could be made a little larger and be easier to build regarding space between components.

[efinque]

That's not bad, I notice you have loads of space left unused, do you have any sort of expansion plans? Those two boards could be made a little larger and be easier to build regarding space between components.

They're built from kit. I could do 2nd order filters but I'm content with the build for now.

Here's a front/rear pic :



The back panel is a bit sketchy.. but I gave it a listen (without preamps) and it sounds sweet.

[Alex Murphy]

That's nice and tidy - I can't imagine the price difference between that and something you get from the shop.

[efinque]

That's nice and tidy

Thanks!

I can't imagine the price difference between that and something you get from the shop.

Yeah, it's an "el cheapo", a poor mans RLA. But the one on Reverb went for 5k USD or something. Integral Sound SDX3500 sets you back around 2k.

The crossover points are 400Hz and 800Hz, the only viable configuration I could make using resistors and caps I could find.

[Alex Murphy]

That's about right for low mids - I remember tinkering between different component values on caps for some filters, going blind took me ages as I experienced with different sets until it felt right.

Keep in mind you have to run yours in as it's fairly new, a few dozen hours will see it sound better.

[efinque]

That's about right for low mids - I remember tinkering between different component values on caps for some filters, going blind took me ages as I experienced with different sets until it felt right.

Keep in mind you have to run yours in as it's fairly new, a few dozen hours will see it sound better.

Going through strips of 480 resistors with a colour code cheatsheet and a DMM was a pain.. in this build I used four 100 ohms.

Same for 120 capacitors all mixed up.. I picked 4,7uF for the lows and 2,2uF for the highs.