BillFitzmaurice.info

Hey all, after building my tuba 30s, I'm now in the process of building 2 omni top 12s. I'm using a faital pro 12fh520 as the woofer and 6 of the Goodwood piezos as the tweeters. The woofer is rated for 600w rms and the tweeters at 50w rms each. How would I go about limiting the cabs? Altogether the cab should be able to handle 900w? Or am I wrong in assuming this. Also I've seriously struggled to find crossover parts in perth, Australia after visiting multiple shops. I didn't want to pay 5 billion in shipping all the individual components from the USA so I've had to settle on a pre-built crossover I have found which has the same 2khz crossover point and 12db/octave filtering characteristics. The crossover comes with 2 woofer outputs but once again I'm assuming I can just use one of the outputs and not compromise power output and what not. I've attached a picture if that helps. Thank you!

Hey Bigrob,
The forum is here to ask before. Bit hard after.
Never be afraid to ask.
I've been searching for components here in Australia for decades now, so have a pretty good idea what's around.

The crossover/filters are custom designed by Bill to improve the performance of the cab they are in.
Off the shelf units don't do that, they have the wrong slopes and filter types.
All the parts required for the filters are readily available in Australia.

Dayton is available through Wagner electronics, for capacitors, inductors and ceramic resistors in the right values.
Jantzen inductors are available through Speakerbug.

The cab will distort before it reaches it's limit. If you hear distortion, you turned up to much, turn it down again.
Then build another cab for next time...

Thanks for the reply Grant, the crossover is rated for 1000w watts though and has the exact same filter characteristics and crossover point as the one in the build plans. Are you saying it will distort because of the crossover? The trouble was that I'm not all too confident with wiring up the crossover myself and I couldn't find a pcb to wire it up on. The bloke at altronics said i would have trouble building such a crossover after i showed him what I needed. Or should I just use a bit of scrap wood to attach components to? Would you be able to give me some advice on limiting as I'll probably stuff this up aswell

That crossover will not work. Off the shelf crossovers are designed to work with the resistive load of a dynamic driver. Piezos are capacitive loads. There are no off the shelf crossovers that will work with them.

Bill Fitzmaurice wrote: ↑Sun Apr 02, 2023 7:03 am That crossover will not work. Off the shelf crossovers are designed to work with the resistive load of a dynamic driver. Piezos are capacitive loads. There are no off the shelf crossovers that will work with them.

Looks like I'm gonna build my own crossover after all

Do you guys recommend I assemble the crossover on a scrap piece of wood?

Bigrob1234 wrote: ↑Sun Apr 02, 2023 8:54 am Do you guys recommend I assemble the crossover on a scrap piece of wood?

Yep. Go to the build threads and check out some of the builds of OT12s, Jacks, etc. You'll see some various ways that people have built their crossovers and get some ideas.

Bigrob1234 wrote: ↑Sun Apr 02, 2023 8:54 am Do you guys recommend I assemble the crossover on a scrap piece of wood?

The crossover sections are called low pass (LP) and high pass (HP) filters. Mount each filter separately on its own ¼” plywood board, screwed to the cab sides, bottom or back. OTop 12 plans, page 18.



From OTop 12 sketchup.

Bigrob1234 wrote: ↑Sun Apr 02, 2023 4:19 am Thanks for the reply Grant, the crossover is rated for 1000w watts though and has the exact same filter characteristics and crossover point as the one in the build plans. Are you saying it will distort because of the crossover? The trouble was that I'm not all too confident with wiring up the crossover myself and I couldn't find a pcb to wire it up on. The bloke at altronics said i would have trouble building such a crossover after i showed him what I needed. Or should I just use a bit of scrap wood to attach components to? Would you be able to give me some advice on limiting as I'll probably stuff this up aswell

Nope, wasn't saying it will distort because of the crossover. What I'm saying is you will hear distortion before you reach the limits of the speakers in the cabs. So, in essence, you don't need to limit Otops, because if you hear them producing distortion, you are already pushing them too hard.

I use scraps of wood. Check out my DR250 build thread on page 2 of Build threads. About half way through.

Before you solder, lay stuff out on the wood and post up pics here to check that it fits and it's right.
There's also a How to Solder primer in Tips and Techniques section of the forum, sticky on page 1.

The bloke at Altronics wanted to sell you something, that's his job

edit: Sing out if you need a hand...

Thanks so much, once again guys!

I ordered all the crossover components yesterday, hopefully they'll come soon! Looks like I'll be returning the one off Amazon. Thanks for once again opening my eyes folks, I guess that's how we learn though

I'll send a pic through once I have the crossovers ready to proof check. I'm quite good at soldering, I've been messing around with random electronics since I was born ahah.

Cheers guys!

How's this looking?

Looks good to me.

Next time, no need for such a heavy gauge inductor on the HF board...