Infinite-baffle sub-woofer using pipes

[RomfordNavy]

Any thoughts on making an effectively infinite-baffle sub-woofer using a small back-box but a long pipe leading from that to increase the air volume?

That pipe could be upwards towards the ceiling, downwards out throught the floorboards, through wall or just out the side. Maybe one large pipe or perhaps a number of smaller diameter ones.

I presume if they are long enough, whatever length that is, whether they are sealed or open will make no difference due to the mass of the air in the tube damping the sound transmitted.

Intention is for 18" cones in around a 40l enclosure. I know I have mentioned these triangular sub-woofers before on another thread but now I have a better understanding of the theory and the idea of infinite-baffle.

 

[Everett T]

Any thoughts on making an effectively infinite-baffle sub-woofer using a small back-box but a long pipe leading from that to increase the air volume?

That pipe could be upwards towards the ceiling, downwards out throught the floorboards, through wall or just out the side. Maybe one large pipe or perhaps a number of smaller diameter ones.

I presume if they are long enough, whatever length that is, whether they are sealed or open will make no difference due to the mass of the air in the tube damping the sound transmitted.

Intention is for 18" cones in around a 40l enclosure. I know I have mentioned these triangular sub-woofers before on another thread but now I have a better understanding of the theory and the idea of infinite-baffle.

How far apart are your studs?

 

[RomfordNavy]

How far apart are your studs?

No studs as brick walls. Floor beams are 18" apart but don't line up perfectly with the subs.

 

[DVDdoug]

You might end-up with a transmission line design.

 

[kyuu]

I'm curious how you're planning on achieving an infinite baffle with a small back box on a brick wall.

 

[Everett T]

No studs as brick walls. Floor beams are 18" apart but don't line up perfectly with the subs.

What type of ceiling and is there crawl space?

 

[Everett T]

You might end-up with a transmission line design.

That was my thought originally but with an 18" driver that's a lot of small pipes or one massive one. A 10 or 12" would be more suitable for a TL, it reminded me of this older Sono Tube design.

Steve's Compounded, Super-Duper Shiva/Sonotube(R) T-line Subwoofers

If he can fit the Sonotube underneath the floor or use the ceiling (more possibilities if possible) it would be an interesting project.

 

[kemmler3D]

I'm not sure exactly how the pipes will be configured, but isn't IB also about not having any diffraction around the sides and back? Not sure how much this matters for a sub up against the wall, but it can't be totally irrelevant?

 

[levimax]

People successfully use fireplaces for IB which is a similar concept.

 

[RomfordNavy]

I'm curious how you're planning on achieving an infinite baffle with a small back box on a brick wall.

By pipeing the back box to either the ceiling or through floor.

 

[RomfordNavy]

What type of ceiling and is there crawl space?

One has loft above so is fine but the other is below a flat roof so no access there.

 

[audio_tony]

This guy did some a crazy thing with a sub - removed a window in his garage and replaced it with a woofer mounted on a board.

Worth a watch just for the entertainment value (he's a bit 'crazy') but also an interesting experiment!

 

[kemmler3D]

This guy did some a crazy thing with a sub - removed a window in his garage and replaced it with a woofer mounted on a board.

Worth a watch just for the entertainment value (he's a bit 'crazy') but also an interesting experiment!

A little goofy for obvious reasons but this is more like what I have in mind when someone says "infinite baffle..." it's about the front as well as the back, right?

 

[OldHvyMec]

The biggest thing to understand is that the air on either side of the driver is "Infinite"; neither side can permit compression. As long as the tubing you add permits that on the back side of the driver, you have accomplished what you need.

As soon as you limit the space on the back side of the driver by use of a sealed space, you have built a TUNED sealed space. In this case, the "speaker" includes the driver and enclosure, and the predetermined space also limits rear excursion by compressing the air in the chamber.

Sometimes people conflate the two concepts. A Sealed box can be an Infinite Baffle, IF the space is big enough. BUT when that space causes air compression, it is a sealed enclosure, not an IB.

The question is, what are you trying to do?

Regards

 

[kyuu]

By pipeing the back box to either the ceiling or through floor.

My question is about the baffle, which is the front. You're talking about the enclosure. To get an "infinite" baffle, you need some amount of the wall/enclosure where the driver is mounted to be flat. Generally if you can get that, then you can get enough space to not need to worry about doing pipe work in an effort to enlarge the enclosure. Also, as pointed out above, if the "enclosure" is leaky, then you effectively have an enclosure the size of the room (or more-or-less "infinite"). This is common for in-wall installations since the drywall and studs generally don't form an airtight container with normal construction practice. As long as the sound from the rear of the driver can't meaningfully escape to interfere with the sound from the front (it would then be an open baffle speaker), then it's not a problem.

 

[Salt]

Infinitive Baffle is a description of the conditions the face of the driver encounters, not what the rear of the driver 'sees‘.

 

[RomfordNavy]

My question is about the baffle, which is the front. You're talking about the enclosure. To get an "infinite" baffle, you need some amount of the wall/enclosure where the driver is mounted to be flat. Generally if you can get that, then you can get enough space to not need to worry about doing pipe work in an effort to enlarge the enclosure. Also, as pointed out above, if the "enclosure" is leaky, then you effectively have an enclosure the size of the room (or more-or-less "infinite"). This is common for in-wall installations since the drywall and studs generally don't form an airtight container with normal construction practice. As long as the sound from the rear of the driver can't meaningfully escape to interfere with the sound from the front (it would then be an open baffle speaker), then it's not a problem.

ok so lets say the back box is vented to the outside somehow so no significant compression as the driver moves apart from that created by the weight of the air and no sound escaping from the back box to interfere with the forward sound waves. Apparently then this is not called infinite baffle but what is it called.

 

[Salt]

This would be open baffle with the baffles size of the room wall.

 

[Timcognito]

Not sure your neighbors would be digging this window embodiment

 

[Titurel]

You might end-up with a transmission line design.

Very much on point. Back when TLs were very much "the thing", there was some debate as to whether the TL was a special case of infinite baffle or of bass reflex. If I remember correctly, when the load presented to both sides of the speaker cone was essentially equal, the design leaned toward being an infinite baffle, if the loading was significantly unequal, the design leaned towards being bass reflex.