First BFM build: SLA PRO 4x6

[Line92]

Hi im Linus, first of all you have to excuse my bad spelling, choise of words and letters
Im 28, live in Sweden and like most other on this forum i love speakers and everything about them.

For now i have a pair of home built 12/1" passive tops with Eminence Kappa12a and B&C DE16 in ME45 horn.
Two 186 horns (rog mogale design) loaded with RCF L18P300.
Powered with two bridged LabGruppen Lab1000 for subs, two bridged Lab500 for tops and one Lab500 for CD. All amps are from between 2005-2007. Controlled by DBX Driverack PA2.

I have finally decided to build a pair of SLA PRO 4x6 with 6 tweeter option after reading and going through build threads here for more than a year
I intend to use these instead of my 12" tops. Mostly for fun/learn to build, and be able to expand later on in a better way, with small easy cabs that isnt so heavy.
I use this for some private partys now and then, and also scare people that want to hear them in my 40m² garage

The piezos i ordered is Rila. Just another very cheap copy from the original. 12pc of Monacors would cost me over 150$ if everyone works, so i will try these at first, if they dont sound as i please i will order the Monacors.

I tested the piezos with a 4ohm resistor series with positive signal to the piezo, i only used the ones that was loud, clear and bright, some were weak and tonally darker, didnt use those.
Is that the correct easy way to test them?

First i made the tweeter array, came out in total like 1/4 inch shorter than it should be according to the plans, but i think that will be ok? I will adjust the baffle cuts to my arrays.

Then i built the crossovers, first time doing that and i am very happy with the result, they also seem to work properly.

Just realized that this post is becoming very long, i actually started the build two weeks ago but got the plywood today!
I will attach some pictures and continue later

[Seth]

Welcome to the forums Linus. I'm Seth.

Looking good so far. Noticed the series resistors to get your 30ohms... clever. Is that a 3ohm or 3.9 in series with the tweeters? I know the plans call far a 4 ohm resistor there. When I was shopping for crossover parts for the 2x6 SLA Pro's I built, the 4 ohm resistors were sold out/out of stock. If I recall correctly, Bill said to get the next size up, which was a 4.1 (I think). I have very little idea what the effect of changing that value would be, but I think it's just there to give the amplifier some resistive load.

Thank you for sharing your build process with us.

[Line92]

Thank you Seth!
Yes, i couldnt get any 30ohm resistors so i went with two 15ohm in series. That is a 3.9ohm resistor, next step up i could find was 4.7ohm, i just guessed that the closest would be best, pretty easy to change later on if i would need a higher resistance, i will screw the crossover inside the cab so i should be able to get it out later.

I used standard wood glue only on the jack plate, just to make sure it will look good from the outside, guaranteed airtight!
For the rest of the cab i use Polyurethane Wood glue, it expands really well and is water/air tight and super strong.
Should that glue/adhesive be OK for a horn loaded cab like DRs or Titans aswell?

I did a couple of small braces with a perfect 90° angle mounted to align the edge of the back piece only to help me screw the side to the back easier. Any input of these? Are they going to be a problem in any way?

I dont get pics over 3mb attached, please excuse me, i will try to change resolution on my camera

[Line92]

This is the small braces, and the glue

[Line92]

The glue looks like this when it is cured

[Bill Fitzmaurice]

The 4 ohm resistor value isn't critical. It's only there to provide a minimum impedance load to the amp at ultra-sonic frequencies, where the piezo impedance goes very low.

[Line92]

Thank you for input Bill, and super good plans that are easy to follow, i will make sure to do a good review later when they are done
Going to be really intresting to hear them. Going for the Alpha 6a, but i have not ordered them yet.

Sorry i did a edit before, asking again if Bill or anyone can make a "go or no" on the Polyurethane wood glue for DR horns / Titans / Tubas.
Polyurethane construction adhesive like the PL Premium is not allowed here in Sweden that i could find. Maybe order from elsewere in EU?

[Bill Fitzmaurice]

The ooze of your adhesive looks good, so it should be fine. Most urethane glues, like Gorilla, are too thin.

[Line92]

Perfect! Thank you Bill

This morning i glued the side to the back on the other cab.
And also found out a mistake, that i have centered the handle/ports on the sides so my main brace covered parts of the handle
Quick fix tho, i hope the brace is still enough, should be?

Tomorrow i will get some damping material.

[Line92]

AHA! I found out that i had alot of this 1/2 inch foam stuff for speaker grille or something. Will this do a good job as damping material?

[Bill Fitzmaurice]

That foam is good.

[Bruce Weldy]

And also found out a mistake, that i have centered the handle/ports on the sides so my main brace covered parts of the handle

I almost did the same thing.....already had it marked and ready to cut when I realized that my actual measurements weren't the same as the plans - I thought the plans had a typo until I started figuring where the brace goes.

It's easy to assume the hole would be centered....

[Line92]

So true Bruce, i rushed and had to pay the price haha!
Looking at your powered SLA PRO build and i feel jelous, you make easy things look so good and easy, or wait, maybe its also just me that tend to make easy things difficult and with a bad result... My ports denifitly did not look as good as yours
Neither do the rest, but i do as good as i can haha!

[Bruce Weldy]

So true Bruce, i rushed and had to pay the price haha!
Looking at your powered SLA PRO build and i feel jelous, you make easy things look so good and easy, or wait, maybe its also just me that tend to make easy things difficult and with a bad result... My ports denifitly did not look as good as yours
Neither do the rest, but i do as good as i can haha!

At least yours will work when you plug it in......I rushed in before I knew exactly what my "powered" solution could actually do....

Woodworking is about having the right tools, taking your time, and probably most importantly thinking a few steps ahead and prepping each step before you execute it. Taking a few extra minutes to build a jig or make sure your setup is straight, etc. make a huge difference.

Believe me, I've made all the mistakes. It always takes longer to fix a mistake than to get it right the first time. But, even knowing that - I still make mistakes. Fortunately, it's always been the wood that suffers and not my fingers.

[Line92]

Haha hopefully it will!
Im happy as long as i have all my fingers left. Its been close alot of times before... stress, bad knowledge and poor judgement is not a good combination.

Some progress made during the day