tubesub configurations

[jimbowley]

Ahhhh I lost my carefully crafted questions. So briefly > Atlas 15" ported tube, for low low HT bass. My starting point is 250l tuned to 19Hz with 250W.

What differences would there be between a tall thin top ported tube, and a short fat bottom vented one?

thanks in advance.

[jimbowley]

awwww c'mon. Someone must have some knowledge or opinion on this?

Removing the shape of the tube from the equation, there must be a difference between having the ports exiting next to the driver versus having them exit at the other end of the tube?

[Dennis H]

Hi Jim and welcome to HTGuide! I guess your question kind of fell through the cracks the first time.

I've never built a tube sub but I'll take a crack at it. There will be a quarter wave pipe resonance inside the tube. The frequency will be something like 280/height in feet. So a tall skinny one may drop that into the range where you want the sub to play. A port on the bottom will couple to the floor and give you more bass. However, it's possible that port (or driver) on the top might give you smoother in-room response because it wouldn't be stimulating the floor-ceiling room mode.

Maybe someone with actual experience will speak up.

[ThomasW]

That's pretty weird, I don't recall seeing this thread before today.

Here's an optimized tube sub design for a high excursion 15" driver, I created for my friend Pete. I suggest you simply copy it..

Pete's ported 1503 tube sub

[jimbowley]

OK. I have seen lots of designs around this size. I have some tube that diameter, but was planning to push the length up by 50%. What will happen around the 1/4wave frequency? (~60Hz for my design).

I make it about 85Hz for your design, so was it designed for a 80Hz crossover? or can you get away with it. Did you audition/test those subs after Pete built them?

[ThomasW]

Pete didn't build this sub, I designed and built it for him. It's just a tube sub variant of this box sub which I also designed and built.

Yes the design has been extensively tested. There are currently more than 1/2 dozen versions (tube and box) of this design in operation.

You don't really gain much of anything by using a lot bigger enclosure, other than living with an imposing corn silo in the room.

Also one should keep ports themselves as short as possible, so as to avoid pipe resonances.

It wasn't designed for any specific 1/4 wave frequency or crossover point. It was designed to provide the maximum output from the smallest reasonable enclosure. And to have absolutely no effects from port compression

[jimbowley]

I've just put an HE15 design into WinISDPro, and as you say there is very little to be had by increasing from 160l to 240l.

But for drivers such as Adire Tempest, Ascendant Atlas, Dayton Titanic there seems to be quite a lot to gain across the 15-35Hz range. Is Vas the relevant parameter here? ( 100 for HE15, 200 to 300 for the others).

Assuming you agree that there are benefits to a bigger enclosure for these drivers, I'd still like to know if standing waves will be a problem, and if anything can be done about them.

Did you notice anything around 85Hz with your tube? If you had no problems around 85Hz is there any reason I should have problems around 60Hz ?

[Bent]

I would hope that your mains are capable of reaching "down" to 80 Hz, (lower is better).
You wouldn't need to run the sub this high if that were the case.

[jimbowley]

Don't say things like that, I'm trying to get my sub to go as low as possible. But now you're going to make me worry about a gap between the sub and mains.

DIY mains will be my next project. Currently I've got Linn Index IIs (6" driver, 750cu inches?), any idea what they reach down to?

[ThomasW]

Room gain is going to fill in those lower frequencies with drivers like the Atlas 15, Tempest, etc. But hey, if you want to create and live with an EBS design that's fine.

No there are no standing waves in any normal subwoofer. The wavelengths involved are simply too long for standing waves to occur.

Did you notice anything around 85Hz with your tube? If you had no problems around 85Hz is there any reason I should have problems around 60Hz ?

I have no idea what you're asking with this question. IF this is back to the statement that Dennis made about 1/4 wave pipe resonances, I don't think it's a issue for either design.

[Bent]

I mentioened this, because although my AS-15 type can get pretty low, it doen'y like it much above 80 Hz...

[ThomasW]

AS-15 type can get pretty low, it doen'y like it much above 80 Hz...

Yeap that's a function of the BP-1503's relatively high voice coil inductance

[Bent]

I imagine the amp is seeing a pretty good inductive load at that frequency.

When I tried selecting 100 Hz (or even 120 Hz...), not only could I locate the sub by it's sound, but it sounded thin and sorta "wonky". I can't think of a better way to describe it better than wonky.