Omnitop12, my first

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ACUA
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Omnitop12, my first

#1 Post by ACUA »

I finally am building up some otop12s. The main cabinet was easy enough but the cd horn was not fun, with out a proper sled on table saw I struggled to succeed. I did not lose my fingers but the horn is a mess!! I tried the 8x stronger version of PL and really like it. It’s thicker and sets faster too. It’s a third more money but worth it to me.
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ACUA
Posts: 552
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Re: Omnitop12, my first

#2 Post by ACUA »

Goodwood GM-500PB 1”
https://www.parts-express.com/goldwood- ... i--270-099

This horn measures 15 3/16”T x 5 1/8”W x 6”D and would fit pretty darn well in a omnitop12, just sand the 3/32” off either end and it fits. Looks like a viable option to me.
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Bill Fitzmaurice
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Re: Omnitop12, my first

#3 Post by Bill Fitzmaurice »

It's not a diffraction horn, the wider angle of dispersion is on the wrong axis.

jimbo7
Posts: 848
Joined: Fri Dec 28, 2012 10:45 am
Location: St. Louis

Re: Omnitop12, my first

#4 Post by jimbo7 »

Birch ply would've made life easier. But most my other builds are with auraco ply. Still looks good all the way from the other side of the internets. Didn't want the hassle of building the CD version so I went flat tweeter. My next pair will use a foam phase plug and be cut with a CNC. I've started a SLA Pro build using CNC cut holes. :mrgreen:
BFM builds:
XF212
T24 BP102 24"
2x SLA's 6-5" mids, 9- gt-302's
2x AT 14" MCM 55-2421
TrT 5" MCM 55-2421
AT 18" JBL GTO804
2x OT12 flat array
2x SLA Pro 2-Alpha 6's 2-Goldwoods
2x T39 24" 3012lf
Simplex 10 BP102

ACUA
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Location: Tucson Arizona

Re: Omnitop12, my first

#5 Post by ACUA »

Not bad for my first pair, perhaps I will get better over time. Did the whole rough wood stained thing to match my subs. I just about built these ot12s on a single $25 sheet of cheap 5ply plywood. It bows and is real crude but with enough glue it works out well.

I may buy one of those goldwood horns and see how it does just for fun. I mean it would save time in the build. We will see!

These took me about the same amount of time as a pair of t45s with all the small angled cuts and pieces involved, less wood by 2/3s but same over all time.

I went with the eminence delta pro 12-450a and asd-1001, total cost per cabinet is under $250.

I really like building speakers.
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ACUA
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Re: Omnitop12, my first

#6 Post by ACUA »

I only had the drivers for one cabinet. So for now one completed. I pulled out my dremmel tool and cleaned up the horn and I am pretty well pleased with it. I have not tested it out yet but it looks good to me.
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ACUA
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Re: Omnitop12, my first

#7 Post by ACUA »

I like it I think I will keep it!!!
So today I set up my ot12 and a t45 to test it out, I found that like the picture shows 7.40ft of delay did the trick and 7.49ft did the high freq horn. I I did a low pass on the sub at 70hz 12db slope. Ot12 100hz 24db, 2k 24db for high/low pass. Pictured with room eq wizard no eq applies and with some eq applied.

Here is my opinion, they sound good. And 45v is going to be damn loud. I have never pushed my peavey 215s over like 25v now that I am investigating it. These rival my old peaveys and are way smaller.

I need to learn how to properly limit my CDriver.
I researched diffraction and I see how the above mentioned goldwood horn is not as viable as I was hoping.
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With eq applied
With eq applied
No eq
No eq
Ot12 Placed in house with one t45.
Ot12 Placed in house with one t45.
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Grant Bunter
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Re: Omnitop12, my first

#8 Post by Grant Bunter »

You did your testing indoors?

If yes, retest, outside, with at least 50 feet of space to the nearest "obstruction"/structure...
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...

ACUA
Posts: 552
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Location: Tucson Arizona

Re: Omnitop12, my first

#9 Post by ACUA »

I tested in my living room, because it is 105 degrees outside here in Arizona and it was easy. I am not trying to get perfection just wanted to test it out to see how it would do.

It did well, :hyper:

I compared it to my peavey 215 which I removed the filter to run active biamp. Here is a graph no eq applied just plugging each in and measuring it.

Basically I need about the same or less eq in my living room on the Omnitop12 than the peavey cabinet. Efficiency is similar but the ot12 is way smaller foot print and I can build it cheaper.
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Green trace is the ot12
Green trace is the ot12
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CoronaOperator
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Location: Medicine Hat, Alberta, Canada

Re: Omnitop12, my first

#10 Post by CoronaOperator »

That dip at 2k could possibly be the polarity of the tweeter backwards, have you tried it both ways and compare?
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

ACUA
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Location: Tucson Arizona

Re: Omnitop12, my first

#11 Post by ACUA »

:noob: that’s what I thought!!! I set up the rta and played 2khz sine and adjusted delay until I got highest level. While searching for summation I observed about 2 dB variation while scanning. Then if I polarity flip I see a 1-2db drop across an octave or so. I sort of wish I saw a 10db drop when I flip polarity it would make it easier!!!

I can blast my house well beyond my wife’s allowance at under one volt to the mid woofer which is cool, the above graph shows the ot12 6db louder in the midrange using one 12” driver against 2 15” drivers that’s cool.

I was running the sub 60hz 12dbslope then tried 80hz 24dbslope both pretty good ended up running the top high passed at 120hz.

I was running in mono which was messing with me being used to hearing in stereo and I was not real happy with a lot of what I was hearing but I attest it to the mono operation not sound quality.
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CoronaOperator
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Re: Omnitop12, my first

#12 Post by CoronaOperator »

ACUA wrote: Thu Jul 19, 2018 8:28 am I was running in mono which was messing with me being used to hearing in stereo and I was not real happy with a lot of what I was hearing but I attest it to the mono operation not sound quality.
Using an RTA indoors to set EQ can cause more harm than good as it is time blind. It is like looking at a photograph of a public swimming pool and trying to determine what ripples are from the guy that just jumped in vs. the 10 kids that just did 5 seconds earlier. Your microphone doesn't know which sound is direct and which is a reflection or 10 reflections previous. You really need to use your ears to adjust EQ indoors. Boosting can really make an annoying freq pop out, then once you identify it by boosting it, you can bring it back down and tame it. Not that RTA's indoors are useless, they are good at identifying feedback frequencies and issues with placement (cancellations) or x-over phase problems. They just aren't good at using to set eq to sound good. Chasing that computer screen will never sound good because move the mic 5 feet over and you will chase a new rabbit on that screen.

You probably couldn't hear the difference but ... While your delay times on your horn look like they have the peaks and troughs lined up with woofer, due to the summation, you probable need another foot or slightly more delay on the horn to get it time delayed right. It might seem excessive compared to the distance the CD is to the woofer but sound doesn't come out of the woofer right away compared to the CD. In an AC circuit: current lags voltage in an inductor (phase lag aka time delay) and the woofer has a larger inductor (voice coil) than the CD so it is electrically delayed more than the CD is from the get go. Of course find max summation over the x-over range to phase align again. Same with your sub, you are probably a wavelength off on your delay there, you probably need another 10 foot delay on your tops (closer to 17 ft total) to get them in perfect sync time wise. Again, probably more academic than audible.

edit/ps: If this is live sound I wouldn't delay my tops 17 ms ( 17 feet), that is crossing the threshold of throwing you off your timing, that last paragraph was just for reference. For just listening to prerecorded music then go nuts on your settings.
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

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Bill Fitzmaurice
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Re: Omnitop12, my first

#13 Post by Bill Fitzmaurice »

ACUA wrote: Wed Jul 18, 2018 10:41 pm I compared it to my peavey 215 which I removed the filter to run active biamp. Here is a graph no eq applied just plugging each in and measuring it.
The nearly identical results below 150Hz indicates that you're measuring the room, not the speakers.

ACUA
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Re: Omnitop12, my first

#14 Post by ACUA »

The results below 150hz are the same because the mic position never changed and I was always running the t45 with same filters on it. Yes I am measuring the room for sure that is why the 54hz huge dip and 88hz peak I think.

How do you properly time align then? Do you not for a 2k filter from mids and highs play 2k sine and adjust until you get peak summation which is loudest point. Yes you can be in phase a few waves off and that is the trick. Problem is my driverack only delays up to 11ft. And so with my tools I can only seek out the closest summation based upon those limitations. If I use my ears to verify and use my spl meter or an rta while playing a sine I can scan the delay and sort out where the phase is. For 80hz crossover a full Wave is 14ft and I can only delay to 11ft but I can basically scan almost all the way through the Wave length and see or hear summation and max cancelation. For 2k Wave is .56ft so in like three clicks on the dial of the delay I get full phase shift. I figured because the plans don’t require delay that little if any is needed. So I simply moved the high to where the mid matched the sub and tuned from there which seemed to be .9 ft more delay than the mid which makes sense seeing how the high driver is physically more forward. But I will admit to being potentially wrong. If there is a better way then I need schooled.

My point was to compare a peavey tower to a ot12 even if in doors the test still stands. from my perspective I am happy with what the ot12 does.
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Bill Fitzmaurice
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Re: Omnitop12, my first

#15 Post by Bill Fitzmaurice »

ACUA wrote: Fri Jul 20, 2018 8:40 am Do you not for a 2k filter from mids and highs play 2k sine and adjust until you get peak summation which is loudest point.
Not necessarily. What you're trying to do is to avoid a 180 degree difference between the woofer and tweeter outputs in the crossover region. The best way to do that is to first test the tweeter with no delay with regular and inverted polarity. Whichever of those that gives the best result is what you go with as the normal. Reverse the tweeter polarity from that and vary the delay until you get the deepest null at the crossover frequency. Put the tweeter polarity back to normal and you're done. Note that 1/2 wavelength at 2kHz is only about 4 inches, so the delay between the woofer and tweeter would never be more than 4 inches. You're not trying to avoid 180 degrees across the entire pass band, only at and near the crossover frequency, which never takes more than 1/2 wavelength of delay.

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