Is Sonotube really the ultimate? (1 Viewer)

[Matthew Will]

Hello everyone,
I have read up on the use of Sonotubes in construction of home theater enclosures and I have the following question.
The main reason sonotubes work well is that because of their cylindrical shape the pressure of the sub is evenly dispersed around the enclosure because it is a circle. Even then though there is still the edge connecting the top and bottom caps of the cylinder. My question then is.

Would an egg shape enclosure prove an even greater enclosure shape? Eggs have been proven to be able to withstand great pressures because the pressure is evely distributed around the shell. If someone were to build this egg shape with no seams could that produce the ultimate in home entertainment subwoofer enclosures? Let me know what you guys think. Thanks. Matt

 

[Joel X]

The two major advantages to a sonsub are that the shape is great and it is very very easy to make an enclosure with, there is also the side benefit of light weight... I think it would be fun to have an egg shaped sub though, good luck on construction.

 

[Dustin B]

Why wouldn't you just use a sphere then. Making a driver and amp fit a sphere or egg without compromising the integrity of the structure will be the real trick though.

 

[Pete Mazz]

Shape would have little effect for a sub enclosure unless it gets very large. Speaker enclosures are a whole nother ballgame. An egg shape would probably be very desireable in that case.

Pete

 

[Dustin B]

I don't think we are going from the idea of eliminating standing waves, but from shapes that are very strong. For with standing even pressure I don't think anything is stronger than a sphere. Which is why the submarines that can go very very deep use spheres for the capsule.

 

[ThomasW]

Fortunately we're building subwoofers not submarines
A sphere like any other symetrical shape will create standing waves. As to whether or not they are problem will be dependent on the passband involved.
There are 2 fundametal problems with sonotube subs. One is the fact that they are fragile and easily dent. The other is SAF. Other than that, they are pretty much the 'best' enclosures available.
Waveform not to be confused with Newform Research made an egg shaped top module for it's speakers. For many years they received very good reviews

 

[Brett DiMichele]

Tom,
LOL that speaker is funny lookin! ahaha
I can just see having a pair of those with gold lettering
on the base module "Le Grande Egg`e"

 

[Matthew Will]

So then the egg shape would prove better than a sphere, cylindrical, or any rectangular enclosure? The man on the mentioned website took the idea of exactly what I was thinking of doing. That is, forming a mold and pouring the cast in there to form one solid enclosure piece. If I were to produce casts would anyone be interested in purchasing any? Lemmeno if this sounds like a nice side business opportunity. Thanks. Matt

 

[ThomasW]

The choice of enclosure shapes isn't as intuitive as one might think. And as I stated previously, the choice of shapes can be dependent on the passband involved.

There was a study of different midbass/midrange enclosure shapes published a while back in "Speaker Builder/Audio-X-Press" magazine. Those articles make for interesting reading..

 

[Brett DiMichele]

Tom,

I was thinking about this last night. You said that a
complete sphere shaped cabinent would not be immune to
the problems that your typical perpendicular internal
surfaces go up against (Standing Waves) But I thought
about this and I can't understand why a sphere would
suffer from this? There are no perpendicular surfaces
on the inside of a true sphere and it seems that standing
waves would be a non issue in such an enclosure.

What am I overlooking?

 

[ThomasW]

What am I overlooking?

You're missing the fact that standing waves can occur in all symetrical enclosures, including those with curved surfaces. Generally speaking asymetrical enclosures are best for avoiding standing waves.

 

[Brett DiMichele]

Tom,

Ok point well taken but I can't get over this mental image
where you have a driver that is verticaly aligned and the
sound waves eminating from the backside of the driver are
traveling perpendicular towards the back of the cabinent
which in this case is a complete sphere. And those sound
waves are striking a non symmetrical surface. There are
many differnt angles the sound would be redispursed at
wouldn't there?

Please understand I am not arguing I am just asking out
of curiosity.

Thanks for sharing the knowledge.

 

[Anthony_Gomez]

An egg shape is anctually not nearly as strong as a sphere or cylinder. The "objective" of any flexing action is to create a circular pressure field along the walls. A sonotube does this easily along the length since it is a circle with uniform longitudinal construction. Any cross section (with the exception of the end cap intersection) forms either a circular or eliptical boundary. With an egg, you only get this along axial cuts. On any oblique cross section, you get a "egg shaped" cross section. This creates area where flex will "want" to preferentially occur even more so than with an eliptical cross section. This non uniform "flex point" is EXACLY what we avoiding with a cylinder (instead of using a box).

 

[Anthony_Gomez]

An asymetrical enclosure does NOT avoid standing waves. Rather it smears the standing waves in a fashion that is MUCH MUCH harder for the average person to try and predict. With parallel walls, the standing waves are more "peaky", but they are also much easier to predict and thus it is easier to attinuate.

IOW, parallel walls make it easier to predict the harsh peaks and you then try to nulify the peaks, while asymetrical walls attempt to smear the waves over various frequencies thus avoiding peaking and then you try to nullify the smear.

 

[Pete Mazz]

I would guess a sphere would actually be the worst shape as far as standing waves. All interior surfaces are exactly the same distance from each other.

The egg shape would probably be great for baffle diffraction effects.

Pete

 

[Dan Pawlowski]

I agree with anthony.

And to quote Tom Nousaine (I hate typing, copy paste is much easier)

Nonparallel surfaces don’t eliminate standing waves at all; they just shift their frequency in a way that’s hard to predict. All surfaces, even nonparallel ones, reflect sound. Making a cabinet without right angles and without parallel panels isn’t going to eliminate or control standing waves. Neither the shape of an enclosure nor the shape of a speaker has much—if any—effect on the standing waves in an enclosure.

Eliminate the reflections, and you eliminate any possibilities of standing waves. Hence, acoustic stuffing like polyfil or fibreglass…etc.