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DIY Proscenium Subwoofer (1 Viewer)

ThomasW

Senior HTF Member
Joined
Nov 6, 1999
Messages
2,282
That shelving filter was just a generic trial to see if it could be done, it wasn't specific to any sub. And LT circuits are really intended for someone with an overly small box, that's certainly not your situation. So I'm not sure you really need or want either.

when you have time post a plot without any EQ.
 

Joe L.

Stunt Coordinator
Joined
Oct 18, 2003
Messages
104
Thomas,

Thanks again. I'll post a frequency response run when I get a bit more time.

At this point, I need to get a last minute errand done... before Santa gets here.. (I've been good... honest...)

Top black velvet fabric is in place, but not yet attached. That will come next week.
There are just about NO reflections from the screen and the fabric covering makes the sub seem so much smaller.
(Not too easy to hide a 25 cu ft subwoofer in a room, but I did it. ;))

 

Scott_Vonhof

Agent
Joined
Apr 11, 2002
Messages
44
Joe, I haven't been on this forum for a while, I didn't know you were this active on this forum. You didn't post that many pictures on the DIY speaker thread on AVS!

Glad to see my rendering made it onto this forum as well though!
 

Bud Huey

Stunt Coordinator
Joined
Jan 11, 2006
Messages
73
Great Thread! I never realized how little I knew about subwoofers! I am designing/building my HT and I plan to install a stage. The height can vary according to my needs, but I would like to keep it below 24". Can anyone point me to some good reference material if I wanted to build the subs into the stage? Is there a "subwoofer design for dummies" available online?

Also, as a side note, I plan to use the stage as a platform for my daughters to sing and dance, so the stage has to support at least a couple of hundred pounds.

Any suggestions would be appreciated!

Thanks,
Bud
 

Joe L.

Stunt Coordinator
Joined
Oct 18, 2003
Messages
104
As far as I know, there is not a lot of "reference material" on building a subwoofer into a stage out there.

There are many ways to build a subwoofer enclosure, two of the most common are a "sealed" enclosure and a "ported" enclosure. Each has its own advantages... for the most part, the one thing you need to be most concerned about is the internal volume of the enclosure and, if "ported" the tuning frequency of the port.

The closest page to the "dummies guide" is http://www.diysubwoofers.org/ Lots there to read and absorb.

If you have 24 inches of space you have a lot more flexibility than I did in how you build your enclosure... you could easily put your drivers front-facing.

You can pretty much use any "box" modeling program and plug in your driver T/S parameters and see the resulting predicted frequency response based on the enclosure type and size. (I used "unibox")

As far as being able to support several hundred pounds, if you look at the pictures in this thread you will see my enclosures have tons of internal bracing and I would think they could easily support just about anything short of a full sized elephant.

Joe L.
 

Broadcast Eng

Auditioning
Joined
Apr 19, 2011
Messages
1
Real Name
Mike Collis
Joe,


Although your question was a few years ago, perhaps you may find my design helpful. My front stage subwoofer is very easy to build no tuning after the build and performance is above 130db at 20Hz (My Radio shack analog sound meter showed 139db but calibration is not spected below 30 Hz). This was not even at full power because dual pane window glass was hitting (inside to outside glass sheet) so I stopped at that point.

Most of the modern 7.1 receivers allow you to select the crossover from main to LFE channel. I use full size mains so I cross at 50Hz. The LFE channel is amplified by a 1000 watt Dayton sub amplifier but other manufactures have amplifiers in this area of power. The Daytom amplifier has EQ and phasing built it so it was a easy choice.


Now for the Sub, I chose Beyma 18G40 drivers, two of them 8 ohm and wired in parallel. My stage is 2ft x2ft and 11 feet long for the part that is the sub, another part to the right of the drivers holds the electronics. The box is made with 13 ply 3/4 inch thick baltic birch plywood that is glued and screwed into 2x2 in each corner the full length of the box. I covered the box with another 3/4 inch thick hardwood cabinet grade plywood and the covering is glued to the birth and screwed from inside the box.


This makes for a tight dead box that will not color the bass. The design is a low Q 90 degree delay acoustical waveguide at 20 Hz. this allows full use of the back wave from both drivers to be used. Simular to a TL but full size waveguide. This cannot be used above 70 Hz becase you are getting near to a 360 degree delay were the front wave and rear wave will try to cancel. That is why the full size main speakers and cross over at 50Hz.


I get as much bass out the front of the drivers as the full size opening of the box. The bass is clean and tight. Response is good to about 12 Hz then drops noticeably below that. Works good up to about 65 Hz but is reduced above 50Hz because of the electronic cross over in the 7.1 receiver.


The box has used rubber floor matt material on the all surfaces in contact with the floor and walls of the room to make sure no bass is transfered to the walls and floor but the box is so dead anyway, you may not need to bother with it. The drivers have 3rd harmonic shorting rings and the bass is clean without significant harmonics so I did not find stuffing was needed at all. Most stuffing is not affective in the low bass and subsonic region anyway.
 

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