T48 Build

[gammagoblin]

Hey Grant

1. The cabs are 66cm wide (inside) I made all the bracing as shown in the plans/sketchup.

2. The HP filter on the crossover (Driverack 260) was set to around 40hz i think (24db/o Linkwiz)
But for safety-reasons i had also the 30hz lowcut on the amp activated.
3. The mud was in the lows. A friend of mine, who knows a lot more about PA-systems than me, was able to get a good sounding kickdrum, out of the subs but what was below the kick, was just mud.
4. I dint check the acess panel for slap, i dont know, how i could miss that part.
5. I sealed the driverchamber, an couldnt find any leaks with the "tube-method" I also had to seal the acesspanel because i was not able to get it fully airtight with the sealing tape. But with the silicone it was airtight.

Yes they look good, and that was also what people said. But for me at the moment its a little bit like: "at least they look good".

I will test them again, but for that i need another place, because i think i neighbours will shoot me if i do another test session in the garden.

ah and what i forgot:
I know it was outdoors, but is it normal, to run the Subs on the amp on full while the Dr280s run on around 30% to match? Because there was almost no bass.

[Bill Fitzmaurice]

I know it was outdoors, but is it normal, to run the Subs on the amp on full while the Dr280s run on around 30% to match? Because there was almost no bass.

Outdoors you have no boundary reinforcement. That results in at least 6dB less sensitivity from subs than indoors, with 9dB less sensitivity being not unusual. The DR280s are unaffected. That's why we recommend using twice the sub count outdoors versus indoors.
To be any more definitive we'd have to see a picture of your RTA response chart.

[Ryan A]

The mud was in the lows. A friend of mine, who knows a lot more about PA-systems than me, was able to get a good sounding kickdrum, out of the subs but what was below the kick, was just mud.

Interesting I just had the same problem on a very different cab. That is not microphone distortion in the video, its actually what I hear for the most part. It only sounds bad on high voltage kick as well, not on sine. Most apparent from 0:10 - 1:10 in the video. Is that similar to what you hear or not?

https://www.youtube.com/watch?v=7yqxOUCDdhI

[gammagoblin]

Had some similarities, i will record, when i get the chance to setup again, without disturbing my neighbourhood. Then i will also save the measurement data.

[Grant Bunter]

Had some similarities, i will record, when i get the chance to setup again, without disturbing my neighbourhood. Then i will also save the measurement data.

Are you EQing using the Driverack?
Or with a standalone 31 band?

You should be able to give us a picture of that.

@Ryan,
Is that an Export or MLX or BLX kit?

[Ryan A]

@Ryan,
Is that an Export or MLX or BLX kit?

Export

[gammagoblin]

Hello friends of the circular saw

I didn't answer in a long time. I managed to get almost everything correct now. Had to reglue the mouthbracing, and do some EQ work.
The PA is now standing at an Outdoor festival (around 300pax expected). Tomorow mornig will be soundcheck. It will mainly be used for Livebands. The subs are separated, because of the view/stage (they wanted it that way). But i am quiet statisfied with the results now. Still need to do some eq work to get it sounding how i want. The rest will be the work of the "FOH" guy. I belive i can get drunk tomorrow without remorse. I will post pictures later.

Thanks to all of you who helped me during the bulid and in advance.

[DJPhatman]

The subs are separated, because of the view/stage (they wanted it that way).

Then make sure there is at least 56 feet (A bit over 17 meters) between them, or you will get bass nulls in the listening area! This is proven science, not a "been doin' it this way forever" kind of thing.

[Bruce Weldy]

Then make sure there is at least 56 feet (A bit over 17 meters) between them, or you will get bass nulls in the listening area! This is proven science, not a "been doin' it this way forever" kind of thing.

That's if you are high passed at 40. I high pass at 50 and can get away with about 42 feet of separation with just a couple of tiny bad spots.....not enough for most to notice.

[DJPhatman]

Then make sure there is at least 56 feet (A bit over 17 meters) between them, or you will get bass nulls in the listening area! This is proven science, not a "been doin' it this way forever" kind of thing.

That's if you are high passed at 40. I high pass at 50 and can get away with about 42 feet of separation with just a couple of tiny bad spots.....not enough for most to notice.

17.1 meters (2.5 x wavelength @ 21*C) is at 50Hz. That is why you are still getting nulls.

[Bruce Weldy]

2.5 x wavelength .

Since when is it 2.5 times the wavelength? I thought it was 2 times.

From the sticky...

Sub Placement:
While it’s customary with PA to have speakers to either side of the stage, that’s usually not the best way to place subs. Subs work best when they’re placed either close together for mutual coupling, or spread very wide to cover large areas. The basic rule is to have them either less than a quarter-wavelength apart or more than two wavelengths apart for their pass band, which for 40 to 100 Hz means less than 2.8 feet or more than 56 feet. To understand why click on this link, which demonstrates the destructive interference between subs that are separated:
http://www.falstad.com/wavebox/

[gammagoblin]

It was bult up this way:
https://scontent-fra3-1.xx.fbcdn.net/hp ... e=561E56C0
https://scontent-fra3-1.xx.fbcdn.net/hp ... e=55E7A930
There have been some cancelations, but we tested a bit with the placement, and got the optimum between soundquality and space/rainproofing etc.
People seemed to be happy, of course a real soundingeneer would have got a stroke, but the PA accomplished its mission.
I lost the fear of using it because i wasnt really shure how the performance would be. I was especially afraid of the bass performance, because i had massive cancellations when i tested it stacked as recomended.
Next time i will have more time and confidence to tune it to even better results.

[Chris_Allen]

of course a real soundingeneer would have got a stroke

..and a rigger!

[gammagoblin]

..and a rigger!

A think i real rigger wouldn't have gotten a stroke, he would have just beaten us to death.
I know the beam on top seems a bit criminal, but at least it was all saved with tiedown straps and anchored to the ground.
The stage itself was quiet stable. You have to see that this Festival was realized by app. 20 year old guys and girls, with no budget, no knowledge but a lot of love for the cause (damn' hippies ).
Thats why i provided the PA.

[DJPhatman]

I was especially afraid of the bass performance, because i had massive cancellations when i tested it stacked as recomended.

This tells me there is some other problem, either with wiring or phase. If you stacked all the subs together, and got cancellations in an open field, there is a problem.