3" foam for Otop12's ?

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wbredin
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Joined: Thu Jun 17, 2010 9:36 pm

3" foam for Otop12's ?

#1 Post by wbredin » Wed Apr 01, 2020 12:56 pm

Guys, just about to button up my 4 Otops but i'm not sure about my internal damping foam. Given the pandemic, all I could come up with is a used mattress topper that's 3" thick. I know 1 to 2"'s is more ideal.

Will this work? Or is it just too thick? Probably splitting hairs but after all this effort, just figured I should ask.

One more thing, what's the best method for attaching it to the internal wood surfaces? Is hot glue sufficient? Maybe a bit of PL?

Thanks
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Grant Bunter
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Re: 3" foam for Otop12's ?

#2 Post by Grant Bunter » Wed Apr 01, 2020 1:24 pm

Hey, that would be “mattress” rather than “topper”!
It is a bit to thick, you might not get it to fit in some spots,

Cut it to size, for say the access panel (a jigsaw will make that nice and clean), then carefully halve the thickness with say a bread knife or large sharp kitchen knife. Suddenly you have the material for both boxes.

Hot melt glue is perfect...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

wbredin
Posts: 27
Joined: Thu Jun 17, 2010 9:36 pm

Re: 3" foam for Otop12's ?

#3 Post by wbredin » Wed Apr 01, 2020 2:19 pm

yea that's true, might as well be mattress...

So sonically, it won't make any difference, correct? If it's a fitment issue, I can manage that part. I just wanted to made double sure it wasn't going to have a sonic impact.

Hot glue it is. thanks!

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Bill Fitzmaurice
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Re: 3" foam for Otop12's ?

#4 Post by Bill Fitzmaurice » Wed Apr 01, 2020 2:29 pm

If it's too thick it will over-damp the cab, which will cause a loss of low end response. The same if it's too dense, which that appears to be.

wbredin
Posts: 27
Joined: Thu Jun 17, 2010 9:36 pm

Re: 3" foam for Otop12's ?

#5 Post by wbredin » Wed Apr 01, 2020 2:46 pm

Bill, thank you for the response. So would you recommend I search out something else? Or how about I just cut it all in half so it's 1.5" thick instead?

Density is the same as standard issue 'egg crate' foam...so my guess that's ok. The thickness might be a bit much though.

Thanks for the help!

himhimself
Posts: 562
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Location: Bloomington IN

Re: 3" foam for Otop12's ?

#6 Post by himhimself » Wed Apr 01, 2020 3:03 pm

An electric knife, like the kind you can carve a turkey with, works wonders on cutting foam. You'd be able to easily split your pieces into half thickness. A few little blobs of pl strategically placed is all it takes to hold secure them, provided you cut them for a slight squeeze when fitting them in.
2xT30 (20", 3012LF)
2xT30 (21", 3012LF)
4xOtop J-array (Beta12, melded/straight piezos)
Truck Tuba (MCM)
Next up: 2xJack12 or family of table tubas

jimbo7
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Location: St. Louis

Re: 3" foam for Otop12's ?

#7 Post by jimbo7 » Wed Apr 01, 2020 5:48 pm

3M spray glue is the best for foam. Just don't spray it outside when it's windy.
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

wbredin
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Joined: Thu Jun 17, 2010 9:36 pm

Re: 3" foam for Otop12's ?

#8 Post by wbredin » Wed Apr 01, 2020 10:05 pm

So just as an update, I cut the 3" in half and it worked just fine. Hot glue also worked very well.

Finally just got a second to hook up one box and demo it. It's impressively loud for sure, but, it sounds 'boxy' and there isn't much low end. I'm wondering, how much EQ these boxes require to sound decent? I'm going to use a Venue 360 so I can tweak as needed. Anyone have some recommended eq profiles for Otop 12's?

I have 12 T48's, so, bass won't be an issue. But I just figured these would get a bit deeper, more like a commercial speaker. I rechecked the phase between woofer and horn and everything seems fine. I"m also just using a home receiver to test this out, so it's not optimized.

Anyway, excited to finish up the other 3 and see what this all sounds like :) Thanks for the help guys!

Grant Bunter
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Re: 3" foam for Otop12's ?

#9 Post by Grant Bunter » Thu Apr 02, 2020 3:14 am

You're not going to get a lot of content below say 80-90Hz with an Otop 12, it's a top box.

You need to tell people how you built them in regards to HF in order to get some advice about EQ...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Bill Fitzmaurice
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Re: 3" foam for Otop12's ?

#10 Post by Bill Fitzmaurice » Thu Apr 02, 2020 7:26 am

wbredin wrote:
Wed Apr 01, 2020 10:05 pm
I just figured these would get a bit deeper, more like a commercial speaker.
Commercial speakers on the whole go an octave or so lower than they need to. If you're not using subs that's useful, but if you have subs all that gets you is cabs that are larger, heavier and more expensive than they need to be to do their job.

wbredin
Posts: 27
Joined: Thu Jun 17, 2010 9:36 pm

Re: 3" foam for Otop12's ?

#11 Post by wbredin » Thu Apr 02, 2020 12:36 pm

Bill, yea after listening to it more, I agree. The Otops have their role and the titans have theirs. I guess it just sounds strange initially because of what my ears are accustomed to.

Grant, i'm using PDS 2013 horns and 3012HO drivers all crossed at 1.2khz.

Grant Bunter
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Re: 3" foam for Otop12's ?

#12 Post by Grant Bunter » Thu Apr 02, 2020 4:21 pm

Unfortunately, all the Otop12 threads in the EQ settings sub forum don't seem that helpful.
If no one else gets back to you with their settings, I can at least tell you a fairly simple way to get you cabs "flat";
The easiest way to get a flat EQ is a technique called mirror imaging.

Print out a copy of the Otop12/NSD SPL chart, draw a pencil line across it that represents an "average" response.
If your SPL chart shows a hump of +3dB at 1K, then in your EQ, bring down 1K by 3dB.
If it's minus 3dB at 2K, adjust EQ up at 2K by 3dB. Examples only.

Go through the spectrum, then tweak as you think is necessary for your ears.

That will get you started at least...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

himhimself
Posts: 562
Joined: Fri Nov 13, 2015 9:34 pm
Location: Bloomington IN

Re: 3" foam for Otop12's ?

#13 Post by himhimself » Thu Apr 02, 2020 9:08 pm

I just plug a ref mic into my driverack (PA2) and run the autoeq wizard. It's never had an issue getting them pretty flat, then I just season to taste with the graphic eq on my mixer. BTW that's the only wizard function I use on the driverack. Had some weird stuff happen when I tried using the level adjust, and usually am too pressed on time to want and tempt fate again. Maybe others have better advice for using the wizards.
As you've seen, the otops have no low end and need to run with subs. It's always fun when bringing the system on line after running the eq sweeps to turn up the otops first, which gets everyone's attention cuz they're loud, and then roll in the thunder from the subs. Always brings a smile to my face.
2xT30 (20", 3012LF)
2xT30 (21", 3012LF)
4xOtop J-array (Beta12, melded/straight piezos)
Truck Tuba (MCM)
Next up: 2xJack12 or family of table tubas

Bruce Weldy
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Location: New Braunfels, TX

Re: 3" foam for Otop12's ?

#14 Post by Bruce Weldy » Fri Apr 03, 2020 8:36 am

himhimself wrote:
Thu Apr 02, 2020 9:08 pm
Had some weird stuff happen when I tried using the level adjust, and usually am too pressed on time to want and tempt fate again.
Don't let the driverack do the leveling for you - it will have you turning down the levels on your amps.....and you should run 'em all the way up. When you run the EQ - if the bottom end needs way too much adjustment either up or down below your crossover point, then adjust the sub output and re-run the EQ.....Or, you can do the same with the tops.....doesn't matter, just get 'em balanced better, then there will be less EQ adjustment.

And remember that you can choose the EQ curve you want inside the Driverack. I always use the one that says music or band....there's a little boost on the low end and dipping in the low mids - if you start there, there will be less trying to fix those issue when EQing the room.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
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."

himhimself
Posts: 562
Joined: Fri Nov 13, 2015 9:34 pm
Location: Bloomington IN

Re: 3" foam for Otop12's ?

#15 Post by himhimself » Fri Apr 03, 2020 8:50 am

Good advice, Bruce. I feel even more justified not using the auto-level function now. I always run my amps wide open, as well. I do like the anti-feedback function. Especially when I'm providing a mic for announcements to someone who doesn't know good mic handling technique. Notching out those trouble zones before shattering eardrums can be a lifesaver!
2xT30 (20", 3012LF)
2xT30 (21", 3012LF)
4xOtop J-array (Beta12, melded/straight piezos)
Truck Tuba (MCM)
Next up: 2xJack12 or family of table tubas

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