Another OT12 build

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DJPhatman
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Re: Another OT12 build

#31 Post by DJPhatman »

LelandCrooks wrote:I really like the grilles. Nicely done.
+1. A question, though. Do you plan to glue fabric or foam as a backer to the grilles?
I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#32 Post by ctmullins »

DJPhatman wrote:
LelandCrooks wrote:I really like the grilles. Nicely done.
+1. A question, though. Do you plan to glue fabric or foam as a backer to the grilles?
Thanks fellas!

I hadn't planned on a backer, just a bit of adhesive foam on each cleat for anti-rattle.
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

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

Re: Another OT12 build

#33 Post by Bruce Weldy »

ctmullins wrote:
DJPhatman wrote:
LelandCrooks wrote:I really like the grilles. Nicely done.
+1. A question, though. Do you plan to glue fabric or foam as a backer to the grilles?
Thanks fellas!

I hadn't planned on a backer, just a bit of adhesive foam on each cleat for anti-rattle.
Looks way better with the foam backer. Just use A/C filter foam (for window units). You can get it at Wal-Mart. Cut it to size, spray the grill with adhesive, then put the foam on. Stack up however many grills you have, put a board on top of 'em, then add some weight. After a few hours, they are ready to install.


OT12 Build 091 small.JPG

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."

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#34 Post by ctmullins »

Thanks, I'll check into it. As long as I don't actually have to go to Wal-Mart... :wink:
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

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

Re: Another OT12 build

#35 Post by Bruce Weldy »

ctmullins wrote:Thanks, I'll check into it. As long as I don't actually have to go to Wal-Mart... :wink:
Or, you can go to a HVAC company and pay 5 times as much.

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."

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LelandCrooks
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Re: Another OT12 build

#36 Post by LelandCrooks »

Hardware store. They might even have the bulk roll and cut it to length. I know I used to.
If it's too loud, you're even older than me! Like me.
http://www.speakerhardware.com

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#37 Post by ctmullins »

All Duratex'ed and corners and top hats installed. Have one more melded array to make, then it's wiring time!

Image
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#38 Post by ctmullins »

Decided to go forward with the two straight-array cabs. Got the first one finished up (except for the grille) this afternoon. Smoke tested it with Spotify running through the Aux In on my little GK MB200.

Image

All of the tweeters work, the woofer works, both Speakons work, and a tone sweep shows no obvious issues at the crossover point. Yay!
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#39 Post by ctmullins »

Two straight-array cabs done! I hooked them up along with one T39 and listened to various tracks for a couple hours last night. Played around with EQ some too, just to get a feel for them. Very mid-forward, like the Jacks. Very shy on the low end, no surprise there. The very top end I thought was also a bit shy, not sure if that's due to the lower sensitivity of just six piezos instead of twelve? Nothing a little EQ can't fix. LOUD! :evil:

Image

The two melded cabs will be done soon, then I can drag 'em outside and try some RTA.
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

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DJPhatman
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Re: Another OT12 build

#40 Post by DJPhatman »

Check your wiring scheme at both the filters and the tweeters themselves. If they are still a little "shy in the high", change the array wiring to 3 parallel pairs of series, or even parallel them all. But, I would do some testing first, just to make sure all are working. Also, reverse the polarity on the array. If you search around, there's also a recommendation by Bill to move a resistor, I think. Bill?
I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#41 Post by ctmullins »

Thanks my friend, great suggestions. I checked Bill's plans, and the resistor mod is designed to reduce output from 2.5k to 5k, so that's not going to help.

I suspect another culprit altogether, though - I have a Behringer XR18 in my rack, running off an Apple Airport Express. Since I have the Express, I have an audio cable running from its analog audio output into the Aux in (channels 17/18) on the XR18. That way I can play prerecorded music over AirPlay.

I did a quick Google search just now, and discovered this article in which the frequency response (and lots of other nerdy things) of the Express' AirPlay is measured - the graphs show a high-freq rolloff starting at about 3k, winding up 1.5db down at 20k. Not terrible, but it might be contributing. I need to test with my source physically cabled into the XR18.
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#42 Post by ctmullins »

First melded cab assembled and successfully tested. I do think the melded array has a bit more shimmer in the top end, again, makes sense having twice as many tweeters.

I tried gluing the diffuser on but it came off after a few days. So I deviated from the plans. :shock: Very slightly! I drilled a top and bottom hole in the array and screwed the diffuser on. I like having a firm mechanical fastener here.

Image

Image
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

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DJPhatman
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Re: Another OT12 build

#43 Post by DJPhatman »

I thought about something very similar. Just be sure to use something at every array joint to absorb rattling between the diffuser and the array.

Getting back to the flat array, did you confirm all the elements are working, using a paper towel core as a listening tube? There could be a non-working element, or some that are low output, causing your lack of shimmer. Usually, piezos give too much highs, being called bright or harsh.
I know money often seals the deal, but seriously, quality is an investment, not an expense... Grant Bunter
Accept the fact that airtight and well-braced are more important than pretty on the inside. Bill Fitzmaurice

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#44 Post by ctmullins »

I did. They're all working, but not all at the same level. One or two are noticeably lower output. Not sure how many spares I have, but I should be able to swap out the elements, right?

I stacked the melded and straight cabs on a pole last night and just played music through them for a couple of hours while I relaxed. With some EQ they sound really good, very detailed. Running both of them I felt like I had enough crisp top end.

Hopefully I'll have time tomorrow to set them up outside and do a pink noise RTA. I don't have a reference mic; I'll just be using the built-in iPhone mic. I know it won't be perfect, but it'll give me something to start with. I already set up a baseline EQ by reversing the SPL chart, and have been tweaking the higher frequencies a bit by ear indoors. We'll see how different outdoors is. It will also be an opportunity to piss off the neighbors by running them wide open for a bit...
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#45 Post by ctmullins »

This was gratifying. :twisted:

Image

Ran it as loud as I dared, given the close proximity of elderly neighbors. Wow!
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

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