Sealed versus Ported Bass, can the difference be measured?

[Paul McNeil]

Are “chimney loaded” subwoofers not “a thing”?
(Sort of like a horn loaded, just done in brick.)

A chimney loaded subwoofer is 'infinite baffle', which is no joke, according so some.

The problem is cutting a hole in the brick (in my case) that fits the driver. This is a joke.

 

[levimax]

From http://ibsubwoofers.x10host.com/

19a) I have an unused fireplace. Can I use the firebox and chimney for an IB?

Unless you live in a castle from the 12th century the firebox won't be large enough for a Qts=Qtc IB sub. Filling the firebox with insulation will likely create something analogous leaky sealed box or strangely tuned vented box. People putting drivers in a firebox have reported pleasing performance. That's fine, but it's not a Qts=Qtc IB subwoofer and that's what this FAQ is about.

 

[Flaesh]

A chimney loaded subwoofer is 'infinite baffle',

Nope. Chimney is tube.

 

[Paul McNeil]

From http://ibsubwoofers.x10host.com/

19a) I have an unused fireplace. Can I use the firebox and chimney for an IB?

Unless you live in a castle from the 12th century the firebox won't be large enough for a Qts=Qtc IB sub. Filling the firebox with insulation will likely create something analogous leaky sealed box or strangely tuned vented box. People putting drivers in a firebox have reported pleasing performance. That's fine, but it's not a Qts=Qtc IB subwoofer and that's what this FAQ is about.

I think I said this was a JOKE! But you have no idea how large my firebox is, but ti is open to the outside world via a new, pristine chimney, one requrement for open baffle.

 

[Paul McNeil]

Nope. Chimney is tube.

View attachment 463830

Thanks!

 

[Paul McNeil]

Thanks so much!

I think I said this was a JOKE! But you have no idea how large my firebox is, but ti is open to the outside world via a new, pristine chimney, one requrement for open baffle.

I think this analysis is beyond us, since I have offered no parameters, such as how long and wide is the chimney!

 

[Salt]

Thanks so much!

I think this analysis is beyond us, since I have offered no parameters, such as how long and wide is the chimney!

How to redirect the line towards your listening place ?

 

[Paul McNeil]

How to redirect the line towards your listening place ?

???

 

[levimax]

I think I said this was a JOKE! But you have no idea how large my firebox is, but ti is open to the outside world via a new, pristine chimney, one requrement for open baffle.

Infinite Baffle is no joke for some people, although my response kind of was. I don't know anything about your firebox and was just quoting the best know IB website about their comments on chimneys and apparently some people do try it.

 

[Salt]

???

A chimney is like a transmission line with defined resonance frequency, and that is used to support a speaker at lower end ...

 

[levimax]

A chimney is like a transmission line with defined resonance frequency, and that is used to support a speaker at lower end ...

So like a pipe organ? Sounds like "one note bass" could be an issue with a chimney IB.

 

[Paul McNeil]

Thanks so much!

I think this analysis is beyond us, since I have offered no parameters, such as how long and wide is the chimne

A chimney is like a transmission line with defined resonance frequency, and that is used to support a speaker at lower end ...

Hmmm, can you guys offer references or mathematical analysis based on physics, for a 16 meter long chimney, open to the outside, and not, like a port on a subwoofer, resonating in the interior space?! I will await your reply!

 

[Paul McNeil]

Infinite Baffle is no joke for some people, although my response kind of was. I don't know anything about your firebox and was just quoting the best know IB website about their comments on chimneys and apparently some people do try it.

IB happens when there is no resistance, or in room input, from the output generated by a drivers movement on the other side of the room being loaded, no port, certainly not a sealed inclosure. A fireplace with a chimney, loaded with a driver, well that's not a simple situation.

 

[Paul McNeil]

I'm resigning from this conversation, not qualified, I think.

 

[Flaesh]

Thanks!

The picture above is a simplified simulation of a straight pipe for an open half-space. The dips may be less noticeable.
In a real room there will be significant differences due to room modes and room gain.

I used to have woofers and then subwoofers in an infinite baffle. Now it's just closed boxes, but the room is almost twice as long).

 

[Flaesh]

16 meter long chimney, open to the outside, and not, like a port on a subwoofer, resonating in the interior space?

The port\tube output goes outside. Inside, only the direct radiator output with dips remains.

 

[Salt]

With 16 meters the resonance f would be around 20 Hz. If redirecting at half of pipe length into listening room this would add some sub bass .
(Or 4 + 4 meter with 30 Hz).

 

[Flaesh]

- direct radiator, 16 m pipe

 

[Salt]

View attachment 464058
- direct radiator, 16 m pipe

Can you add the response of the 'horn' (here: line), meaning the backfired energy, with hornresp?

 

[Flaesh]