First BFM build: SLA PRO 4x6

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Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

First BFM build: SLA PRO 4x6

#1 Post by Line92 »

Hi im Linus, first of all you have to excuse my bad spelling, choise of words and letters :lol:
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 :lol:
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 :D

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 :D
Attachments
20201114_001559.jpg
20201114_001547.jpg
20201116_211717.jpg
20201116_182908.jpg
20201114_223133.jpg
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

User avatar
Seth
Posts: 2733
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: First BFM build: SLA PRO 4x6

#2 Post by 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.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#3 Post by Line92 »

Thank you Seth! :hyper:
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! :wink:
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 :)
Attachments
20201121_121954.jpg
20201121_121004.jpg
20201121_115738.jpg
20201121_115614.jpg
20201121_115542.jpg
20201121_113735.jpg
20201121_103440.jpg
20201121_103350.jpg
20201121_103234.jpg
20201121_101157.jpg
Last edited by Line92 on Sat Nov 21, 2020 4:01 pm, edited 1 time in total.
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#4 Post by Line92 »

This is the small braces, and the glue
Attachments
20201121_094701.jpg
20201121_155345.jpg
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#5 Post by Line92 »

The glue looks like this when it is cured
Attachments
20201121_143757.jpg
20201121_174633.jpg
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: First BFM build: SLA PRO 4x6

#6 Post by 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
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#7 Post by 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?
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: First BFM build: SLA PRO 4x6

#8 Post by Bill Fitzmaurice »

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

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#9 Post by 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? :fingers:

Tomorrow i will get some damping material.
Attachments
20201122_092059.jpg
20201122_092042.jpg
20201122_092002.jpg
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#10 Post by Line92 »

AHA! :hyper: 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? :fingers:
Attachments
20201122_095828.jpg
20201122_100220.jpg
20201122_100133.jpg
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: First BFM build: SLA PRO 4x6

#11 Post by Bill Fitzmaurice »

That foam is good.

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

Re: First BFM build: SLA PRO 4x6

#12 Post by Bruce Weldy »

Line92 wrote: Sun Nov 22, 2020 3:29 am
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....

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."

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#13 Post by 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!
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

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

Re: First BFM build: SLA PRO 4x6

#14 Post by Bruce Weldy »

Line92 wrote: Sun Nov 22, 2020 10:04 am 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.

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."

Line92
Posts: 48
Joined: Wed Apr 15, 2020 12:54 am
Location: Sweden

Re: First BFM build: SLA PRO 4x6

#15 Post by Line92 »

Haha hopefully it will! :lol:
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
Attachments
20201122_162824.jpg
20201122_124219.jpg
20201122_122355.jpg
SLA PRO 4X6
T60 2x20"
Labgruppen fP6400. fP2400Q. DBX Driverack PA2
TLAH
AT 20"
TRT

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