Finally! Omni 12 Tall Boy build

High power and fidelity from an easy to build cabinet.
Post Reply
Message
Author
CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#76 Post by CarterKraft »

Playing with the tuning some...
Here is a shot of the as built 3 way crossover.
defualt crossover.JPG
layoutv1.JPG
Weldon Carter

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

Re: Finally! Omni 12 Tall Boy build

#77 Post by Grant Bunter »

Hmmm.
I think perhaps you're doing your drivers a disservice with the choices you have made for cross points.

To explain a little better:
The 3012HO has a rising response to at least 2K.
In my older plans, it doesn't give the cross point values of the passive filters (and I'm not going to reverse engineer them), but does say in the introduction that mid driver duties take over from 400Hz.
That makes some sense, the 3012HO will do 400Hz +2-2.5dB better than the LA6CMBR.

Similarly, the APT will do HF much better than the mid driver.
You've selected 3K, but at 2K the APT is a massive +7.5dB compared to the mid driver at the same value.
So maybe it might be worthwhile trying 400Hz and 2k.

Hope that makes sense...
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...

CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#78 Post by CarterKraft »

Grant Bunter wrote: Sun Sep 18, 2022 4:10 am Hmmm.
I think perhaps you're doing your drivers a disservice with the choices you have made for cross points.

To explain a little better:
The 3012HO has a rising response to at least 2K.
In my older plans, it doesn't give the cross point values of the passive filters (and I'm not going to reverse engineer them), but does say in the introduction that mid driver duties take over from 400Hz.
That makes some sense, the 3012HO will do 400Hz +2-2.5dB better than the LA6CMBR.

Similarly, the APT will do HF much better than the mid driver.
You've selected 3K, but at 2K the APT is a massive +7.5dB compared to the mid driver at the same value.
So maybe it might be worthwhile trying 400Hz and 2k.

Hope that makes sense...
Absolutely it does and I did move the low up to 400 after recording the "as-built" values. The top end though I have not messed with.
This is my first blank sheet tuning excersize and it's a little like drinking from a fire hose.
There is full equalization of each channel but it's more complicated than moving dials or sliders so I haven't messed with it yet. I will probably get a omnimic and attempt some Auto EQ functions of the DSP software.
Weldon Carter

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: Finally! Omni 12 Tall Boy build

#79 Post by Bill Fitzmaurice »

Grant Bunter wrote: Sun Sep 18, 2022 4:10 am The 3012HO has a rising response to at least 2K.
On axis. There is no on axis from the woofer with the O12 baffle configuration. The stock crossover to the tweeter is 2.5kHz, as the midrange works well to that.

CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#80 Post by CarterKraft »

I will make that adjustment to 2.5k, thanks for clarifying that detail.
Weldon Carter

CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#81 Post by CarterKraft »

I am thinking I want to try and EQ this setup.
I can get the IMM-6 mic and use my tablet to record the response from some sweeps or tones but what specifically tones/sweeps do I test, many frequencies from 50 up to?

So if the source unit is at a fixed volume and the gain on the amps is fixed then I can EQ each frequency to flat response accross the board.
Do I do one driver at a time, all together? Since it is tri-amped with no passive crossover parts (outside of the protection caps) that would be best?
Then do them all together to check my work?

I am looking for a teach a man to fish type guide, not free lunch.
Weldon Carter

CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#82 Post by CarterKraft »

Grant mentioned in another thread the RED marked post on the APT is not + oh man I missed that detail for sure.
So does it matter if the protection cap is on the negative if just reverse the polarity at the amp?
I think they are in phase but I will test this to be sure.
Weldon Carter

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

Re: Finally! Omni 12 Tall Boy build

#83 Post by Bruce Weldy »

CarterKraft wrote: Wed Sep 21, 2022 12:35 pm Grant mentioned in another thread the RED marked post on the APT is not + oh man I missed that detail for sure.
Not sure that is still true or occurs on all Eminence drivers. Certainly you can test the polarity just by switching back and forth and see which sounds louder.

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: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: Finally! Omni 12 Tall Boy build

#84 Post by Bill Fitzmaurice »

CarterKraft wrote: Wed Sep 21, 2022 12:35 pm Grant mentioned in another thread the RED marked post on the APT is not + oh man I missed that detail for sure.
So does it matter if the protection cap is on the negative if just reverse the polarity at the amp?
I think they are in phase but I will test this to be sure.
Read my reply. The same procedure to test polarity is in your plans.

User avatar
Seth
Posts: 2730
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: Finally! Omni 12 Tall Boy build

#85 Post by Seth »

This is gonna be a fun set up! Gimme a few and I'll do a little writeup.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#86 Post by CarterKraft »

Its easy enough to switch in the DSP, just check the box but if I did wire it backwards the protection cap will be on the wrong post, I wager it doesn't matter?

Seth wrote: Wed Sep 21, 2022 12:52 pm This is gonna be a fun set up! Gimme a few and I'll do a little writeup.
It has the output, you guys were right about that.
The Dynamic bass fattens up the bottom nicely for easy listening.
There is still A LOT to learn in regards to the DSP but I really like the functionality.

I also need to figure out how to set the gains for each driver, right now it's sort of mid to LOUD, then match the tweeter and woofer to it by ear, sounds good to me and my son but no idea if its right.
Weldon Carter

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

Re: Finally! Omni 12 Tall Boy build

#87 Post by Bruce Weldy »

CarterKraft wrote: Wed Sep 21, 2022 1:10 pm sounds good to me and my son but no idea if its right.
If it sounds good - it's right!

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
Seth
Posts: 2730
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: Finally! Omni 12 Tall Boy build

#88 Post by Seth »

I completely agree. But, if you wanna geek out and do it by the numbers...


Image

I'd like to suggest a few changes to the layout...

- Add a Parametric EQ with at least 4 bands between the Stereo to Mono Mixer and the 3-way X-over
- Remove the second delays on the woofer and mid
- Add a delay to the Tweeter
- Move the individual trim/volume sliders to the right and place them between the phase inversion and output meters
- Add a trim/volume slider in the same location for the tweeter



- Tuning steps are best done outdoors away from reflective surfaces. A park or football field would be great. But, if that's unreasonable, as far away from reflective surfaces as possible and aimed diagonally at the least reflective surface.

EQ the individual Drivers
- Use Pink Noise
- Disable and factory reset any filters, EQ, dynamic bass, etc. you may have played with already. Ensure the pre crossover EQ is completely flat and also ensure your pink noise source has no audio enhancements enabled.
- With the woofer and midrange completely off, set the tweeters high pass filter to 300ish Hz (we'll put it back up to 2.5kHz later), turn the volume up to 10-20dB above ambient noise in the 2500-16,000Hz spectrum, and use the post crossover tweeter EQ to flatten response to within ±3dB if possible. If response dips down above 16kHz, no need to bring it up with EQ. We're not going to hear it and the kids don't need to.
- Set the tweeter highpass filter to 2.5kHz and mute the tweeter.
- Adjust the crossover settings for the midrange driver to about 100Hz for the highpass and 20kHz for the lowpass. Turn the mid on and turn it up so that it's about 10-20dB above ambient noise in the 400Hz to 2.5kHz range and use the post crossover EQ to flatten the response the best you can to within ±3dB.
- Set the midrange crossover filters back to the recommended settings (I'd personally recommend you start with 24dB LR filters) and mute the midrange driver.
- Disable the crossover for the woofer and turn the woofer on. Bring the volume up to 10-20dB above ambient noise in the 50 to 400Hz range and use the Post crossover EQ to flatten the response to within ±3dB in that spectrum, as best you reasonably can.
- Set the woofers crossover to the recommended settings and mute the woofer.
- Turn the pink noise off.


Gain Balancing, Driver Polarity, and Phase Delay Testing
- Play a 400Hz sinewave
- Master volume all the way down, turn on the woofer and turn it's trim slider all the way up. Slowly bring up the master volume until you read about 84dB, write down the exact dB reading.
- Do not change the master volume until these steps are completed. Once set, do not change the individual driver trims either.
- Mute the woofer
- Turn the midrange driver on and slowly adjust it's trim up until it reads as close as possible to the same dB reading you got on the woofer, measured from the exact same spot. Write down the exact dB reading and also the exact trim slider position.
- Turn on the woofer so that the woofer and midrange are both playing at the same time. If the volume has gone down, invert the polarity on the midrange. Write down the exact dB of them both playing together and also notate if inversion was required.
- Mute both, woofer and midrange
- Play a 2500Hz sinewave
- Turn the midrange driver on and write down the exact dB reading. It should be within 6db of the 400Hz reading for the same driver.
- Mute the midrange driver
- Turn on the tweeter and slowly raise the trim until it reads as close as possible to the midrange reading, write down the exact dB level and the exact position of the tweeter trim slider.
- Turn on the midrange driver. If the SPL has gone down, invert the polarity on the Tweeter. Write down the exact dB of them both playing together and also notate if inversion was required.
- Turn off the signal generator
- Unmute all three drivers

Post all of your exact dB measurements (along with any adjustments made in the next step) and I'll calculate the required phase delay times needed for you.

Adjustments, Tune to a Target Curve, and Finishing Touches
At this point in the process you can play some pink noise and view the entire 50-16k spectrum. It should be relatively flat all the way across. I wouldn't worry too much about little blips here and there that stick out. If one of the low/mid/high bands looks to be overall above or below the other two, you can simply adjust the trim in 0.5dB increments until you're satisfied. Write down any adjustments made.

If you listen to music at this point, it'll sound very very bottomless. We now need to EQ the system pre crossover to achieve a desired system response. As a starting point, using the pre crossover PEQ, adjust the filters so they resemble the curve indicated by the orange trace in the response graph below.

Image

This is a good place to start. It may or may not require more tinkering to meet your expectations.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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

Re: Finally! Omni 12 Tall Boy build

#89 Post by Grant Bunter »

Seth wrote: Wed Sep 21, 2022 3:03 pm
Image
Very comprehensive Seth!
Your target curve:
You trot it out reasonably regularly.
I don't think I've seen you explain to anyone what cabs it's based on, how many cabs, (subs or no) and in what environment.

I wish there was a target curve panacea, but there isn't, so fill us in on the details!

@CarterKraft:
Seth's point is a good one.
For some strange reason, there seems to be some idea that the best speaker response is flat.
I can mostly guarantee that any speaker cab measured flat at testing will not be flat when used out of the environment in which it was tested.
And flat sounds sterile.
So, tweak by ear, do it Seth's way, whatever sounds best to you is where need to get to...
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...

CarterKraft
Posts: 255
Joined: Thu Oct 22, 2020 1:46 pm
Location: DFW

Re: Finally! Omni 12 Tall Boy build

#90 Post by CarterKraft »

Wow Seth you are a true gentlemen for putting that together. I think I even follow what you are intending (Famous last words haha).
The layout will be easy to modify and honestly it's a work in progress after the pre-made config failed to have any output on the woofer at all...
For a raw volts test I just need to play a 400hz tone and check the max voltage before clipping? I have a labscope to measure with.

I will get the mic coming, this should be fun.
Weldon Carter

Post Reply