Idea for speaker cabinet design

[audiology]

I'm keen to get some feedback on an idea, I am relatively nooby with loudspeaker box design, though I have built my own subs and speakers, they were always a simple design copied from plans.

I was thinking - is there any reason why you couldn't use a relatively thin tube(say around 1 to 2 inch inside diameter), with some 'pods' that the mid/bass driver sits in that is all in the same air volume? If this thin tube attached straight into a larger volume of air - could this act like a large cabinet? See the images below - I am a designer and in my spare time mocked these up in 3D CAD. I think they could look very elegant, and is a fusion of the bose concept but with minisubwoofers at the bottom of each speaker. Obviously with quality drivers and crossover these would sound far superior to Bose.

To clarify - the pod behind the mid/bass, the tube that holds it up and the box below it are all the same volume of air, I'd imagine this would give the air volume of a large bookshelf speaker, but in a more elegant design.

What I need to know is, would such a long/thin tube be able to act as the box volume for the driver? I have a feeling there are cabinet designs such as transmission line that use a long,narrow convoluted path that the air takes before being vented to atmosphere. Perhaps a box modelling program would be the best place to start.

Any thoughts/comments? This is really only a concept for aesthetic reasons, or for those who want compact speakers, as you can see from a purely front-on view the speaker they virtually dissapear. The tweeter could be mounted in the end of the tube(ie a compact neodymium magnet model) and the mid/bass would be approx 6".

 

[Sheep]

Well, A for effort, but if that driver is 6.5 inches in diameter, that speaker is roughly a billion feet tall. Also, the 2 inch tube with those sharp bends would be VERY restrictive, and make the enclosure useless.

I think with maybe a larger tube, and less bends, it could work. Lots of physics that you're have to work out though, and I am in no position to help in that area.

SheepStar

 

[audiology]

Thanks - Yes excuse the details as I have CAD modelled - no doubt the scale is all wrong, and the tube bends tighter than the need to be.

But, assuming even if the tube was straight, I wonder if it's a feasible box design concept. Quite possibly it's already been done before. I think it could be nifty because it also acts as a speaker stand, so it is like having floor standing speakers, but with the appearance more like BOSE or one of those horrible HT-in -a-box systems.

 

[no. 5]

Hay! those look like they were made with SolidWorks.

I am not qualified to offer real advice in this area, but it looks to me like the tube would act something like a pipe in a pipe organ.

 

[audiology]

Well picked, yes Solidworks is what I use. I spend a significant part of my (work)life using that program, it does come in handy for little projects like this. As you can see I just used the bog-standard room scene for rendering.

Yes I am worried that the length of the tube may act as a port - and a port that long may end up tuning the box down to like 5hz or something.

 

[Swerd]

To clarify - the pod behind the mid/bass, the tube that holds it up and the box below it are all the same volume of air, I'd imagine this would give the air volume of a large bookshelf speaker, but in a more elegant design.

What I need to know is, would such a long/thin tube be able to act as the box volume for the driver? I have a feeling there are cabinet designs such as transmission line that use a long,narrow convoluted path that the air takes before being vented to atmosphere. Perhaps a box modelling program would be the best place to start.

I'm confused by what is what in your design.

Is the driver at the top end of the tube the tweeter or the woofer? If its the woofer, how is it connected to the air inside the tube and the box below? The diameter of the tube would have to be at least as large as the diameter of the woofer.

Is the tube open or closed?

And where does the tweeter go?

 

[audiology]

Have a look at the following image, this should explain what does what.

The small driver at the very top is the tweeter.

The larger driver is the woofer, which has a compact chamber it sits in, which is in the same air volume as the tube and large box at the bottom.

The tube is closed at the top.

 

[stratman]

Check out Linkwitzlab.com you might be surprised

 

[j_garcia]

I think it would work, however the problem you are going to have is resonance on the supporting beam. It is a great concept though. If you use a sealed midbass, you don't need a chamber for it. Here is one that I did for a thread at AV123 that is also an open baffle concept.

 

[stratman]

The model I was refering to over at Linkwitz is the PLUTO, I believe it's the same principle of what you're proposing. Their's is not as nice looking, but it works.

 

[jonnythan]

I estimate that your speaker is a bit over 8 feet tall. Not good.

Furthermore, your tube will probably ultimately be acting like a port [in other words, it will be tuning to a certain frequency and go a long way towards isolating the speaker assembly from your larger enclosure below, just like the port on a subwoofer or conventional cabinet]. It will severely restrict air flow. your tube needs to be much larger, which will probably ruin the effect that you're going for.

 

[audiology]

Stratman - Yes I did look at the Pluto and it is a slightly similar principle - perhaps that will be the smallest tube that is possible without tuning the port down. I guess what I'm trying to do is 'cheat' a little and try giving a compact speaker appearance but without the dissadvantages of a micro driver in a 0.2 litre box.

J_garcia I see your point about resonance - the tube would definately need to be thicker and constructed from resonation-resistant materials. Obviously a tube that thin would need to be metal to have any real strength - otherwise carbon fibre could work, but would need to be lined with a good bitumen liner and perhaps a small amount of acoustic damping material.

Jonnythan - yes I think that'd be right, the tube just acts like a port, which at that length would tune the system too low. Another thought I had was that a tube that thin could not contain the wires to run to two drivers, as well as damping materials and a useful air volume inside it!

Perhaps I'd have to simplify the concept and just make the mid/bass sealed and place another driver in the bottom cabinet, making a 3 way system, that's probably the only way to go. Only trouble with that though is the huge gap between the bottom driver and mid/bass, may create a bit of sound separation. I'd imagine the mid/bass would go down to say, 100hz(assuming it is 6.5", not approx 4" as the scale of the speaker shows), the bottom driver picks up from there and goes all the way down. Perhaps an 8" driver would be best for that.

 

[LucasG]

I think the tube would need to be larger in ID as to not cause port noise but the bends are definatly possible, just difficult. However as others have stated, there will probably be some screwy resonace since the tube is so long. With no support the tube will probably vibrate to a resonant frequency and really mess with the responce curve.
But hey it just might sound good enough for what you want to use it for, as I am not quite sure how to acustically model the tube, not quite sure what will happen.

Just my .02