Need help with crossover/limiting omni top 12

High power and fidelity from an easy to build cabinet.
Post Reply
Message
Author
Bigrob1234
Posts: 33
Joined: Sun Feb 05, 2023 4:56 am

Need help with crossover/limiting omni top 12

#1 Post by Bigrob1234 »

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!
Attachments
Screenshot_20230402_111626_Amazon Shopping.jpg

Grant Bunter
Posts: 6915
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: Need help with crossover/limiting omni top 12

#2 Post by Grant Bunter »

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...
Last edited by Grant Bunter on Sun Apr 02, 2023 3:29 pm, edited 1 time in total.
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Bigrob1234
Posts: 33
Joined: Sun Feb 05, 2023 4:56 am

Re: Need help with crossover/limiting omni top 12

#3 Post by Bigrob1234 »

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 :(

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: Need help with crossover/limiting omni top 12

#4 Post by Bill Fitzmaurice »

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.

Bigrob1234
Posts: 33
Joined: Sun Feb 05, 2023 4:56 am

Re: Need help with crossover/limiting omni top 12

#5 Post by Bigrob1234 »

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 :wall:

Bigrob1234
Posts: 33
Joined: Sun Feb 05, 2023 4:56 am

Re: Need help with crossover/limiting omni top 12

#6 Post by Bigrob1234 »

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

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Need help with crossover/limiting omni top 12

#7 Post by Bruce Weldy »

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.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: Need help with crossover/limiting omni top 12

#8 Post by Bill Fitzmaurice »

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.

Image

From OTop 12 sketchup.

Grant Bunter
Posts: 6915
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: Need help with crossover/limiting omni top 12

#9 Post by Grant Bunter »

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...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Bigrob1234
Posts: 33
Joined: Sun Feb 05, 2023 4:56 am

Re: Need help with crossover/limiting omni top 12

#10 Post by Bigrob1234 »

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 :wink:

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!

Bigrob1234
Posts: 33
Joined: Sun Feb 05, 2023 4:56 am

Re: Need help with crossover/limiting omni top 12

#11 Post by Bigrob1234 »

How's this looking?
Attachments
20230409_135948.jpg

Grant Bunter
Posts: 6915
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: Need help with crossover/limiting omni top 12

#12 Post by Grant Bunter »

Looks good to me.

Next time, no need for such a heavy gauge inductor on the HF board...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Post Reply