T48 Build

[gammagoblin]

Hello Forum
As already threatened, i will show you my building process. First i start with the T48.
First i want to thank for the recomendations i got on this forum. (In this thread: http://billfitzmaurice.info/forum/viewt ... 28&t=22072)

So i got my wood, my speakers, all wires, etc.
I allready made the cutouts and finished the speaker mounting panel.

[gammagoblin]

Almost finished with the assembly

[gammagoblin]

Almost finished the Subs

[Tom Smit]

Oooo. Fancy!

[bitSmasher]

Nice! will you continue the theme on other boxes?

[gammagoblin]

Yes on the Dr's will get the HF section, colored the same way. The Black is the RAL Code 9005 (Deep Black) silk glossy, the orange is a MTN Mars orange. It isn't as pale as on the picture (shitty cellphone cam), its slightly darker.
Here ist the color:

Actually its just a grafitti can, but it behaves really good, dries well, and if you use one of those "astro-fat-caps" you won't have to struggle with running paint (don't know the right english expression but you know those drops).
It also doesn't peel off or something like this.
Actually i frist wantet to paint the cabs in a dark grey, but as the Plastic corners and the jackplates are black i, just took black for convinience reasons. But i still wanted to give it something special. It should have a slight touch of some strange outerspace vehicle. Even if the combination forces some "eye-cancer" its not that common black in black.

[Chris_Allen]

How can you not love the piezo array? Especially when it's orange!

[gammagoblin]

But what i realized, when i did fire them up: I have a massive dip @62Hz, something, that can't be threatened by EQ, and to be room related its too much i think. Its around 12dB measured. What could that be? As far as i could test, there are no airleaks.
Measured by ear with a sine-sweep, and by CARMA also with a sine sweep.
If i have the time, i will mesure it again today, but outdoors. So i can run it on higer power and wont have any room relatet influence.

[Chris_Allen]

To eliminate the room, I'd move the mic to a different location and measure again but outside is your best bet.

[Bill Fitzmaurice]

But what i realized, when i did fire them up: I have a massive dip @62Hz, something, that can't be threatened by EQ, and to be room related its too much i think. Its around 12dB measured.

Room sourced dips can be as much as 24dB deep. I guarantee that moving either the sub or the mic position will give a different result. You can't get an accurate measurement indoors.

[gammagoblin]

Ahhh, i am so happy now. Just moved the cabs outdoors (just 2 of them) and measured it again. They had a much better response. On axis it showed almost the same response as the chart on the website. offaxis (i just stacked them vertically, side by side) it had a little dip at 60Hz. I will, if i have the time and space (couldn't go beyond 30% because of the neighbourhood), test all four of them stacked as recomendet.
Well, they are really loud and nice sounding, and i have now a grin in my face, that has to be removed by a plastic surgeon.
I got the wood for the top's today. Can't wait to "set the whole system on fire".

Have a nice day and thanks for all the advices.

[Bill Fitzmaurice]

it had a little dip at 60Hz..

Where was the mic? If it was a few feet above the ground you'll get a ground bounce reflection that will cause a response dip. When measuring subs the mic should be an inch or so off the ground.

[gammagoblin]

Ok din't know that, had the mic almost on ear level.

[gammagoblin]

hy Forum
I finished my bulid, yesterday:


But when testing, i had massive Problems with the Bass. The 30hz Lowcut on the Amp is activated, but we had a lot of "mud" in the lows. Something was possible equilize, but i am still not happy.
The other thing is, that at more than 40% of the volume-poti, the Titans start to resonate somewhere, and the driver has something like a very dull delay. Its hard to explain, a friend of mine described it as breathing.
Does anyone know the problem? And can anyone help me out?
Because at the moment i wouldn't play that system for more than 100 pax with a good conscience.

[Grant Bunter]

hy Forum
I finished my bulid, yesterday:


The cabs look great
How wide are the subs?
Did you put in all the required braces?

But when testing, i had massive Problems with the Bass.
The 30hz Lowcut on the Amp is activated,

You should not use an amp based subsonic filter, at all. Most of them are only a 12dB/octave slope.
If I have misunderstood what you are saying, please explain some more.

IIRC, in the thread mentioned up top, you have a driverack.
That's what you should be using!
If so, the High pass for the sub output channel on the driverack should be set to 35Hz for 4 x T48's, with a 24dB/octave slope, either linkwitz reilly or butterworth filters.


but we had a lot of "mud" in the lows. Something was possible equilize, but i am still not happy.

Is it in the lows or the mids?
It could be EQ.
What is your crossover point?
If you haven't set up your driverack, both your subs and your tops/mains could be trying to deliver the same content, which would be muddy.


The other thing is, that at more than 40% of the volume-poti, the Titans start to resonate somewhere, and the driver has something like a very dull delay. Its hard to explain, a friend of mine described it as breathing.
Does anyone know the problem? And can anyone help me out?
Because at the moment i wouldn't play that system for more than 100 pax with a good conscience.

Again, how wide are your subs and did you put in enough braces?
Also, did you test the driver for slap against the access panel braces as explained in the plans?
And did you leak test both driver/chamber, and the access panel once put on?

The picture you show suggests you do not have at least 17 metres of free space around the system.
The slap/delay you are hearing could be bass bouncing off the fence and nearby building...