BillFitzmaurice.info

Those look really, really good! Just wait until you hear them!

Hi Everyone

Sorry it's taken so long to update this thread.
My personal interests have been pushed down the family's priority list of late.
Well, I finally got to test the T39s.
I wanted to graph the Frequency Response so that could work out how to best integrate them with the mains using my Behringer DCX2496.

To conduct the tests, I used a free program called REW (Room Equaliser Wizard) http://www.roomeqwizard.com/ .
As the name implies, this program is to help equalise a system in a room (usually a home theatre system).
The program measures SPL, impulse responses, distortion, phase, group delay, spectral decay plots, waterfalls, etc.
No, I don't understand all that. But if you do, then give this program a try.

I used the program to do Ground Plane Measurements.
To do this, I went to a large open field (150m of flat playing fields in all directions except directly behind the speaker).
I placed my calibrated testing mic on the ground 1m in front of the T39 I was testing.
I meant to take some photos of the set-up, but it was looking as if it wanted to rain, so I was pushed for time.

I took two sets of tests of each T39. They were almost the same, so I've only shown one set from each T39 below.
I don't know the amp voltage I was using, as the program wanted me to adjust to a test tone of 75dB.

I am really happy with the results (see below). Ignore the volume, as I was probably testing well below 1v, but look at the shape of the curve. For both subs, the curve is similar to the curve that Bill shows in his T39 (12"Lab, 30"wide) (ignore the blue line ). However, I don't seem to have the shelf at 40Hz that Bill achieved.


Now these are my results (T39-A and T39-B). Remember, mine are 27" wide.




Now all I have to do is integrate them with their PA and crank them up.
Next project I guess will be improving their mains (Would love to do some DR250s, but may have to settle for some OmniTops).

Wow! For "no smoothing", they are pretty smooth!

Grats on finally getting your titans done.

That's a beautiful graph; I think that's the real graph of what a t39 should be. Also, while similar, the graph you posted is a completely different driver and is basically like comparing the s2010 to the bp102, both are 10" but produce quite different response. Your graph will be close to this (the 3012LF in a 30" cab)


That graph really makes me want build a pair just like yours, but I know my otops won't be able to handle them.

As for the smoothing, that's usually what I get with subs too. Once you go past 500, it starts getting crazy.

Thanks guys.
I'm pretty happy with the graphs (BTW, the sweep stopped at 200Hz).
Would you believe that I still haven't fired them up in angry yet.
They are for my daughter's band which are touring interstate at the moment.

To integrate them with their existing system (speakers-on-sticks), I have bought an analogue mixer, a DCX2496, a DEQ2496 and a Europower EP4000 - all second hand.
It's all a bit of a hobby as most of the large venues have their own sound system.
Still, I know the band are keen on hearing them.
Actually, I should say three bands, as she is the drummer in three local bands, but only one does serious touring.

When I give them a serious onstage test, I'll update this thread with my (and the bands') feelings.
Cheers

Nordo wrote: Note the amount I had to trim from the flange around the opening to be able to slide the speaker in.

Did you have to do this to the top flange as well?
Couldn't quite see in your pics...

Grant Bunter wrote:

Nordo wrote: Note the amount I had to trim from the flange around the opening to be able to slide the speaker in.

Did you have to do this to the top flange as well?
Couldn't quite see in your pics...

Hi Grant
Bit green out your way I believe.

No, I only trimmed the flange at the bottom.
I slid the top edge of the driver in first, then scribed how much I had to trim off the bottom flange.
I don't think it comes up very well in the photo, but I undercut the piece of flange I removed, so that the shape of the cut followed the arc of the driver as I was lowering it in (does that make sense?).
The flange of the driver was just scraping the timber flange as it was being installed.
This meant that I had trimmed away the absolute minimum amount of the cabinet's flange, as I didn't want any chance of leakage.

The Lab12 drivers came with a loose gasket which went between the driver and the cabinet's mounting flange which made sure there was no leakage at that interface.

My next small job is mounting my mixer in the cheap little rack cabinet I bought.
I will fix the mixer to the cabinet with hinges. I just have to open up the mixer to make sure the mounting screws don't end up mangling a circuit board or something.

Cheers

Nordo wrote: No, I only trimmed the flange at the bottom.
I slid the top edge of the driver in first, then scribed how much I had to trim off the bottom flange.
I don't think it comes up very well in the photo, but I undercut the piece of flange I removed, so that the shape of the cut followed the arc of the driver as I was lowering it in (does that make sense?).

Makes great sense

The flange of the driver was just scraping the timber flange as it was being installed.
This meant that I had trimmed away the absolute minimum amount of the cabinet's flange, as I didn't want any chance of leakage.

The Lab12 drivers came with a loose gasket which went between the driver and the cabinet's mounting flange which made sure there was no leakage at that interface.

My next small job is mounting my mixer in the cheap little rack cabinet I bought.
I will fix the mixer to the cabinet with hinges. I just have to open up the mixer to make sure the mounting screws don't end up mangling a circuit board or something.

I would use pop rivets rather than screws, much lower profile.
And I'd be more inclined to build a square frame to attach the mixer to, bolt the sides of the frame to the rack to act as a pivot at the front. That way, if you ever need to sell on the mixer, it's not full of holes in the mixer case.
Cheers

Yes mate, it is a bit green out here at the moment
It's a refreshing change to see some green after years of drought, even if it is only weeds, and, as such, isn't good value fodder for the farmers and their stock.

Hi Grant
Sorry the feed isn't as good as the news broadcasts make it out to be.

I'll definitely take a look at building a frame for the mixer.
I can buy lengths of alloy angle in various sizes and colours from Bunnings (also lengths of small SHS).
I should be able to make something out of that.
I used to have a rivet gun but it disappeared some years ago.