60ndown's Merged Subwoofer Thread

[60ndown]

ive built maybe 30-40 subs in the last 25 years, all seem to perform better when the driver/s are facing away from me, it seems to me that listening to the reflected wave makes the bass/sub bass smoother/deeper.

im talking typically about 60 hz and down

i want to build a new sub, but i want to have the output aimed directly at me, not reflected.

ill be using (4) 6" subs i pulled from some thrift store speakers i have

im good with a tape measure and tools, and am not afraid of scaling a design intended for 18s

anyone know of a 'great' design and a link to some plans i can build?

[janneman]

Originally Posted by 60ndown

ive built maybe 30-40 subs in the last 25 years, all seem to perform better when the driver/s are facing away from me, it seems to me that listening to the reflected wave makes the bass/sub bass smoother/deeper.

im talking typically about 60 hz and down

i want to build a new sub, but i want to have the output aimed directly at me, not reflected.

ill be using (4) 6" subs i pulled from some thrift store speakers i have

im good with a tape measure and tools, and am not afraid of scaling a design intended for 18s

anyone know of a 'great' design and a link to some plans i can build?

I don't know whether it is physically possible. At bass frequency wavelengths, the driver acts as a point source so will always tend to be omni.
Baffles and reflectors to 'channel' the radiation will necessarily have to have dimensions related to those wavelengths, ie several/many meters. Look at a bass horn: the mouth area is huge.

jan didden

[60ndown]

Originally Posted by janneman

I don't know whether it is physically possible. At bass frequency wavelengths, the driver acts as a point source so will always tend to be omni.
Baffles and reflectors to 'channel' the radiation will necessarily have to have dimensions related to those wavelengths, ie several/many meters. Look at a bass horn: the mouth area is huge.

jan didden

i see subwoofers designed for rock concerts, where all the sound is projected forward,

and subs for the corner in an HT system.

I want to build a small rock concert sub

[60ndown]

interesting page


subwoofer horn plans - Google Search

[janneman]

Originally Posted by 60ndown

i see subwoofers designed for rock concerts, where all the sound is projected forward, [snip]

So, how do they do that then? IF they do?
I assume you realize that the fact that the opening is facing forward has nothing to do with the radiation pattern (at sub frequencies)?

jan didden

[Peter M.]

I don`t think it is possible to have directivity in the modal region of a room, regardless of how large the horn is.

I suggest you read about Gedlee`s multisub approach:
Multiple Small Subs - Geddes Approach

[godfrey]

Originally Posted by 60ndown

...subs... all seem to perform better when the driver/s are facing away from me...

Interesting.

Originally Posted by janneman

At bass frequency wavelengths, the driver acts as a point source so will always tend to be omni.

Yes, the deep bass will be omni-directional. However the speaker also creates distortion and noise ("chuffing" from ports etc) at higher frequencies where radiation is more directional.

So although speaker orientation may not affect the bass itself, it may well be a good idea to have the distortion and noise aimed away from you rather than towards you.

[Zero D]

@ janneman

So, how do they do that then?

Science & Physics

Offset rear facing, out of phase, time delayed sub for every 2 forward firing subs. Variations on the theme are possible & also implemented. Works a treat to reduce bass going backwards, & annoying people, especially outdoors.

[Xoc1]

This article on the Void Accoustics website will help explain about directional bass arrays.
http://www.voidaudio.com//pdf/bass%20guide.pdf
As mentioned by Zero D this involes using drivers in groups of 3.
Some bass arrays use bins in groups of 3 (for example Martin Audio)
Some use 3 drivers in one box with 2 facing forward and one facing to the rear such as D&B Audio
d&b audiotechnik -J-SUB.
To get these arrays to work they use digital speaker management systems.

[Zero D]

@ Xoc1

Dems da ones