Is this practical ? Sonotube subwoofers for medium sized PA

[Nut]

Heya.

I'm very interested in constructing a medium sized PA that kicks really hard... The only real requirement is it has to be as power efficient as possible as we run most of our gear off a battery pack charged via solar energy.

Recent research has shown me the funky thing that is the subwoofer constructed out of sonotube. I've only come across tutorials for subs intended for small hi-fi rigs... I'm much more interested in putting some ~1000W plus subs together for rocking warehouse parties.

So, my main questions are:

Drivers. Is if worth going bonkers and using 24inch drivers ? ALso, what brands are worth looking at ? I'm totally keen on Precision Devices drivers, but there are obviously many more options.

Sonotube desgin. Is it practical ? I'm attracted to its simplicity. I realise they're hardly space efficient, but i'm not SO worried about that if it means I can avoid some serious woodworking that would come with a folded horn design.

Power efficiency. Digital amps all the way, but what brands ? I'm having troubles coming up with a decent list of maunfacturers and models to consider.

All help muchly appreciated.

[tINY]

Digital amps help, but for really efficient transducer designs, you need big boxes for subs.

Sonotube is a little hard to flair - which you need in a horn design.

Usually more, smaller drivers are more efficient than fewer, bigger ones. Especially if you have a way to add some delay to individual drivers in a large horn design.



-tINY

[Wavebourn]

Here is mine:

www.wavebourn.com :: View topic - Horn loaded isobaric subwoofer

I would not going anymore with isobaric design since partial cancellation of 2'nd order distortions don't worth loss of efficiency.

[Nut]

Is flaring essential ? Can I not just have ports within the tube ?

The tubes would end up being quite large, as in several meters high. So they'll be big boxes.

I dig the idea of having more smaller drivers. I've been looking at the idea of two drivers working in a push pull fashion, one at each end of the tube.

I'm most intrigued by the way those drivers are mounted in the wavebourne design. Could you explain a little more about that concept ? Does it have a name ?

[tINY]

Yes, flairing of some sort is essential. a horn is an impedance transformer.

It allows a driver to move a smaller amount of air at a higher pressure and transforms that motion into a larger amount of air at a lower pressure at the horn mouth.




-tINY

[Wavebourn]

Originally Posted by Nut

I'm most intrigued by the way those drivers are mounted in the wavebourne design. Could you explain a little more about that concept ? Does it have a name ?

There are 3 concepts:
1. Low-Q horn
2. Isobaric
3. Well damped surfaces and volume.
The first means an acoustical transformers as tiNY said, the second means connecting speakers face-to-face (push-pull) to partially cancel 2'nd order distortions and shift down the main resonance frequency. Most probably I would like better the same drivers moving twice bigger square. In such case I would need less power for the same loudness, it means less distortions of 2'nd, 3'rd and so on order. Anyway, the device is finished, so let it live as born.
The third one means lower Q of resonances of surfaces and of air inside the box. You can not avoid them completely, you may damp them using Dynamat, linoleum, memory-foam, etc... Metal ribs help to shift their frequencies up and "de-tune", making more resonances of lower Q on random frequencies instead of less stronger resonances of lower frequencies.
I used such design because I wanted less errors of reproduction, i.e. flat frequency response and less distortions on frequencies it reproduces.
In order to impress listeners you may prefer ported boxes, long tubes, and similar designs that highlight some frequencies and create impression of more bass than recorded. For example, BOSE engineers use such approach to impress housewives: "Such small box but so much bass!"

[tINY]

Originally Posted by Wavebourn

For example, BOSE engineers use such approach to impress housewives: "Such small box but so much bass!"

No need to talk of the devil....

But that is an interesting way of getting efficiency. A band-pass enclosure is quite efficient.

You simply need to build a box with two ported chambers and put the drivers between the chambers. You can even mount them in opposite directions (but I doubt many of the distortion components will make it out of the ports).



-tINY

[Wavebourn]

Originally Posted by tINY

But that is an interesting way of getting efficiency. A band-pass enclosure is quite efficient.

Indeed!


http://www.waynet.org/waynet/spotlig...pipe-organ.jpg

[tINY]

Nice organ - your church or you tune it?


-tINY

[Wavebourn]

Originally Posted by tINY

Nice organ - your church or you tune it?

Here is mine:

http://wavebourn.com/images/pyramid/..._speaker_1.jpg

http://wavebourn.com/images/linearray.gif