Nordo's Dual T39 Build

[Nordo]

Hey Nordo,

I hope we are referring to the same thing, the mouth braces, but I guess it applies to all braces.
Ok, horns pretty much eliminate harmonics, so that's not an issue, and the same can be said about nodes.
Panel vibration however is a problem.
It may not be able to be felt by hand, but if it's there, it robs you of output, around 3dB IIRC.

It should say in your plans that nominal bracing width is 6 to 9".
So for the mouth braces, with a 27" wide panel that should mean exactly 9" from each panel edge should be a line, being the centre for that brace, and the measurement from brace to brace centre to centre would also be exactly 9". Sorry about the imperial measurements, but 9 x 3 = 27 lol, so it's a great example.

9" is 228.6mm, so your bracing space of 318mm is in the order of 75mm to wide. I hope it's not going to display itself as a problem for you.

It makes sense to, and says to in the plans, offset braces where they double up, eg panel 2/5, 5/8.
When I built mine (for other than the mouth braces), I simply drew the line, then offset the brace by the thickness of the material so I could get a screw into either side...

I say "throat", you say "mouth". Mouth is probably the better word.
When I was talking about nodes and harmonics, I meant in the panels when they are vibrating.

Panel 6 is well braced (from each side), so probably panel 10 could be my only problem.
If it is a problem, I could run a 75mm high stiffening rib in the middle of panel 10, from front to back (also being fixed to panel 11).
Is there any way of telling if panel movement is a problem?
Being 3dB down isn't a real indicator when I don't know what I'm comparing it against.

BTW, I do intend to test my T39s when completed, using a free program called REW (Room Eq Wizard) and a calibrated Dayton EMM6 mic.
The program is meant for room testing, but should be fine for testing the output of a T39.
Was going to have a look in the forum on the recommended setup for testing. I have fairly open areas near the house where I could get minimal reflections.

[Nordo]

Guys, I have a question.

My tub of Duratex has arrived.
I estimate that, for two coats, I will just have enough to cover both T39s IF I don't paint the mouth and associated braces with Duratex (use ordinary matt black instead).
My fault I guess, for making the boxes so wide.

Has anyone else done a similar finish (painted the mouth area with a different coating than the Duratex)?

I intend to water the Duratex down a little bit (any comments on how much?). This will definitely make it go further, so maybe I could coat some of the mouth (say panel 6) with Duratex.

Any suggestions?

[Ryan A]

I'd just paint the mouth in black paint or whatever color. The mouth won't take punishment like the outside will.

I wouldn't water it down unless it says you can...can't remember.

[Bruce Weldy]

Guys, I have a question.

My tub of Duratex has arrived.
I estimate that, for two coats, I will just have enough to cover both T39s IF I don't paint the mouth and associated braces with Duratex (use ordinary matt black instead).
My fault I guess, for making the boxes so wide.

Has anyone else done a similar finish (painted the mouth area with a different coating than the Duratex)?

I intend to water the Duratex down a little bit (any comments on how much?). This will definitely make it go further, so maybe I could coat some of the mouth (say panel 6) with Duratex.

Any suggestions?

A gallon of duratex will do several cabinets. Do not water it down.

Paint the cabs with a couple of coats of flat black latex...then roll on the duratex. Two coats will do pretty good and you'll have 80% of the gallon left. That stuff goes a long way.

[ripNdeb]

Paint the cabs with a couple of coats of flat black latex...then roll on the duratex. Two coats will do pretty good and you'll have 80% of the gallon left. That stuff goes a long way.

+1 I did almost everything in my sig with ONE gallon - except the last 4 T39s and some of the WHs left to do. So, that's two pretty wide T39s, two OTop 112s, FOUR DR250s, and an XF212!

[Nordo]

A gallon of duratex will do several cabinets. Do not water it down.

Paint the cabs with a couple of coats of flat black latex...then roll on the duratex. Two coats will do pretty good and you'll have 80% of the gallon left. That stuff goes a long way.

Hi Bruce
When you say "latex", what paint are you referring to?
Did you use an acrylic latex, like Dulux's Weatherguard? Or something cheaper?
And when you say "two coats will do pretty good", are you saying one coat of latex and one coat of Duratex? Or one coat of latex and two coats of Duratex?

I have already bought a couple of cans of matt black enamel spray to do areas such as inside the handholds, and possibly the mouth. But I hadn't thought of "priming" the whole exterior before applying the Duratex.

[Bruce Weldy]

A gallon of duratex will do several cabinets. Do not water it down.

Paint the cabs with a couple of coats of flat black latex...then roll on the duratex. Two coats will do pretty good and you'll have 80% of the gallon left. That stuff goes a long way.

Hi Bruce
When you say "latex", what paint are you referring to?
Did you use an acrylic latex, like Dulux's Weatherguard? Or something cheaper?
And when you say "two coats will do pretty good", are you saying one coat of latex and one coat of Duratex? Or one coat of latex and two coats of Duratex?

I have already bought a couple of cans of matt black enamel spray to do areas such as inside the handholds, and possibly the mouth. But I hadn't thought of "priming" the whole exterior before applying the Duratex.

Just any flat black paint off the shelf by the gallon is fine.....I usually pay less that $20 a gallon. Put on two coats of the flat black. It dries so fast that by the time you finish one coat, you can start right over again. I usually just brush on the flat black reaching as far up the mouth as I can. Save the spray for inside the handles, etc like you mentioned.

Then, roll on 2 coats of the duratex. Again, I re-coat as soon as I've finished the first coat....it dries up pretty quick. Then just let it sit for a day. If you feel the need to add another coat - go ahead....you'll still have plenty left over. Seriously, this stuff goes a long way.

[Nordo]

Just any flat black paint off the shelf by the gallon is fine.....I usually pay less that $20 a gallon. Put on two coats of the flat black. It dries so fast that by the time you finish one coat, you can start right over again. I usually just brush on the flat black reaching as far up the mouth as I can. Save the spray for inside the handles, etc like you mentioned.

Then, roll on 2 coats of the duratex. Again, I re-coat as soon as I've finished the first coat....it dries up pretty quick. Then just let it sit for a day. If you feel the need to add another coat - go ahead....you'll still have plenty left over. Seriously, this stuff goes a long way.

Thanks Bruce, that's great information.

If I stand each box on, say, a couple of long pieces of 45x90 (2"x4") to raise them off the ground as I'm painting, how long (with the flat black and Duratex) can I wait before I can flip the boxes over and stand them on the new painted sides. I guess the same question applies to handling the boxes.

[Bill Fitzmaurice]

how long (with the flat black and Duratex) can I wait before I can flip the boxes over and stand them on the new painted sides. I guess the same question applies to handling the boxes.

DuraTex takes a good long while to cure, best done by letting cabs sit in the sun. If you can't hang the box to paint it you'll need to put feet on it to keep it off surfaces.

[Bruce Weldy]

how long (with the flat black and Duratex) can I wait before I can flip the boxes over and stand them on the new painted sides. I guess the same question applies to handling the boxes.

DuraTex takes a good long while to cure, best done by letting cabs sit in the sun. If you can't hang the box to paint it you'll need to put feet on it to keep it off surfaces.

For the primer.....Turn 'em upside down first....paint the bottoms and sides. Flip 'em and paint the top and sides..


For the duratex....back upside down, paint bottom and sides (couple of coats). Put on the rubber feet, turn right side up and do the top and sides. This way the sides get a little more protection as they get beat up the most.

I always do mine on saw horses just to make it easier to get to...

[Nordo]

FINALLY got my Titans painted!!!!!

For those following this thread, sorry about the delay, but the instructions from Duratex say that you must apply when humidity is below 70%. We've had well over 90% since before Christmas.
I applied a coating of matt black just after Christmas, but had to wait until last week before finally being able to apply the Duratex.
I could have risked using the Duratex in the high humidity, but having got this far, I didn't want to stuff it all up in the final straight.

This is a trial installation of one of my Lab12s. Note the amount I had to trim from the flange around the opening to be able to slide the speaker in.
Note also the piece of temporary wire I had put through one of the holes, to help with pulling the speaker back out again.

These are my two Titans with their one coat of matt black and their two coats of Duratex applied.
I found the Duratex quite easy to apply.
I didn't dip the roller into the pot, like the instructional video shows, but used a small roller tray. I didn't buy the rollers from Duratex, but found some similar sponge rollers locally.
The Duratex was very thick in the pot so I did water it down slightly, because I wanted an orange peel finish and not a rough texture.
Even then, the texture is still quite rough - like black sand paper.
One point I only found through reading everything I could on Duratex was that, after you finish, spray the surface of the left over Duratex in the pot with water before putting the lid on. This increases the shelf life of the left-over Duratex.

The application of the Duratex was done in four stages :-
1. Top and four sides of both boxes.
2. Flipped them over and painted the remaining side.
3. Repeated 1 and 2.
I had bought four rollers, but they washed out so well in water, that I re-used them and still have two left over.
Note that I didn't apply the Duratex in the mouth of each cabinet. I didn't think I could get an even coat, and the mouths should receive very little knocks and abuse.

Now I'll be adding the castors, corner protectors, Speakon plugs and the Lab12s.

[Nordo]

Got a good day in yesterday.
The Titans are now finished.

Haven't actually fired them up yet, but hopefully will try and do that today.
The one thing I meant to do but forgot, was to make a cardboard template of the stiffener on the inside of the speaker cover, and use it to make sure the speaker cone will never come in contact with it.
However, there has been very little feedback on people having this problem, so I'm hoping all will be well.

I also want to test the Titans using a test program and calibrated mic I have. I will add the SPL charts to this thread when done.

One thing I do have to say regarding my build - I bought the kit for each T39 from Speaker Hardware.
I cannot say enough about Speaker Hardware.
Everything was supplied. The kit is exactly what they describe - "everything you need except the plywood".
Leyland was exceptionally helpful, and returns emails very promptly.
I opened an account with Shipito, and Speaker Hardware sent the kits to them and they sent them to me.
It's always a worry when you are spending a lot of money, buying stuff unseen from the other side of the world, and not knowing if it will arrive in one piece, or even arrive at all.
But it all arrived safely, thanks to the way Speaker Hardware pack the kits.

All I can say to anyone contemplating building a BFM speaker, buy the kit from Speaker Hardware, and your only worry is your ability to cut and glue plywood (and there's plenty of help to walk you through that on this forum )

[Tom Smit]

FINALLY got my Titans painted!!!!!

For those following this thread, sorry about the delay, but the instructions from Duratex say that you must apply when humidity is below 70%. We've had well over 90% since before Christmas.
I applied a coating of matt black just after Christmas, but had to wait until last week before finally being able to apply the Duratex.
I could have risked using the Duratex in the high humidity, but having got this far, I didn't want to stuff it all up in the final straight.

Oh, that would have been frustrating! Kudos for waiting.

[Bruce Weldy]

FINALLY got my Titans painted!!!!!

For those following this thread, sorry about the delay, but the instructions from Duratex say that you must apply when humidity is below 70%.

I've never noticed that .......just as well, if I was to wait for the humidity to get below 70%, my cabs would still be unfinished.

[ctmullins]

They look great! We are no strangers to high humidity levels here; thankfully I got my T39s painted a few months back; winter in the northern hemisphere and therefore lower humidity, but I'll need to bear that in mind as I finish up my OTs... Anyway, they look great!