The making of: The Two Towers (a 25 driver Full Range line array)

[wesayso]

The massaplaat translates into mass loaded sheet. Probably something similar to Mass Loaded Vinyl.

I think I'm good with my current enclosures but could gain from (partly covered) CLD dampening.

 

[wesayso]

Just ordered Silent Coat 4mm product. Tested very well (among the top of the list) in the "Sound Deadening (CLD) Testing - Car Audio" thread on DIYMobileAudio. I got a sneak preview at the results as they are not up yet. Probably will be soon.
The link to the whole thread I mentioned above: Sound Deadening (CLD) Testing - Car Audio | DiyMobileAudio.com | Car Stereo Forum

Now I need to figure out how to use it on the wavy shaped chamber . It is very flexible however, not like bitumen mats.

 

[Halair]

Now I need to figure out how to use it on the wavy shaped chamber

What? You just cut out a gazillion meters of 17mm wide strips and start gluin'??

 

[wesayso]

25% coverage, no more

 

[niffy]

Spray on automotive under-seal ? Might need a lot of coats to get it as thick as your silent coat and will probably be less compliant but would give 100% coverage.

 

[wesayso]

I actually considered that stuff. I even have it from restoring my car. But I'm only looking at dampening the vibrations of the enclosure. For that, 25% coverage with a good CLD will be enough.

 

[niffy]

Ah ha. That makes sense. I thought you were saying you could only get 25% coverage with CLD due to the internal structure of the cabinet.

 

[Slothrop]

Wes, I'm curious, how much cabinet volume does each driver have? Hope the project is going well, I'm excited to see them finished in your listening room.

 

[wesayso]

Wes, I'm curious, how much cabinet volume does each driver have? Hope the project is going well, I'm excited to see them finished in your listening room.

A rough figure after deadening would be about 2 liter per driver, maybe a little more. Driver volume is subtracted from that total. Second baffle is almost ready, just a few holes to redo in the rubber layer. Next up is dampening material tests and wiring. Not much else really.
Just want to make sure to think each step trough, There is enough time involved in this project not to mess it up.

Just got my amplifier back from service, ready to roll. (a 24 year old Pioneer amp, hope it's up for this job. It's a Pioneer A757 Mark II. 20 Kg of old-fashioned power. But it rates at ~ 100 watts RMS at 8 ohm. I sure do hope that's enough. Bought this amp new all those years ago and would hate to let it go.

 

[wesayso]

Moving along for the second tower, lining up the baffle/drivers:

 

[Halair]

It's a Pioneer A757 Mark II. 20 Kg of old-fashioned power. But it rates at ~ 100 watts RMS at 8 ohm. I sure do hope that's enough. Bought this amp new all those years ago and would hate to let it go.

I have a 125W 8ohm amp on mine so I'm certain you'll have fun with 100W
I'm going for 25W Class A for mine, another DIY project

 

[wesayso]

I expect that as well...Should be plenty for now.
Second tower standing tall:

Done for the day... need to clean up before my family arrives.

 

[Slothrop]

Looking really good! How much longer till you can give them a listen?

 

[wesayso]

That depends on how crazy I get with the rest of my plans
Still some things to do but hope to get there within 3 weeks.

 

[barackuda]

Wes...
looking really great!!!
Hope for a detailed review how they turn out sonicaly

Danny

 

[wesayso]

Rigged up a testing wire for impedance testing in REW.
Here's a few first results:

So what do you guys think...

(test enclosure, one speaker)

 

[esgigt]

nothing a few passive components can't fix

Did you measure the DC resistance?

 

[Greebster]

Fiberglass/angel hair looks best. Lets see distortion measurements.

 

[wesayso]

Very little difference between fiberglass and fiberglass/angel hair...

The wool felt was only used on the vertical walls, I want to try that with fiberglass with all walls covered with wool felt. I ran out of time to be able to seriously test more combinations. The wiggle at 400 seemed lowest on the fiberglass/wool felt combo.
Compared to the speaker on baffle without box:

 

[wesayso]

Another day of testing with various materials and placement of those materials.

Fiberglass stuffing enclosed in wool felt gave the smoothest curve (again).
Very small trace left of the wiggle just before 400 Hz. It is in the empty chamber plot but not on the baffle alone.
Can't find a sweet spot to remove it entirely yet.