This is an extension of a thread Giant Subwoofer.
I had asked about drivers bigger than 18". But a great deal was said about running below fs.
So, I want to separate these two issues so they both can be explored more fully.
Some folks have been extremely helpful here already.
But still, who is running below fs now, or has thought about it, or has some information about it?
I had asked about drivers bigger than 18". But a great deal was said about running below fs.
So, I want to separate these two issues so they both can be explored more fully.
Some folks have been extremely helpful here already.
But still, who is running below fs now, or has thought about it, or has some information about it?
http://sound.westhost.com/project48.htm
I am especially intriqued by the above. He uses a small sealed box enclosure to raise the resonance of a sub woofer.
So he operates only below fs, never above or at it.
He uses eq to contend with the downward slope.
I find this approach very intriquing.
It solves one issue. Previously, you could add more drivers and more power, but it does not lower fs.
Here, he starts below fs. So more drivers and more power do help.
I am especially intriqued by the above. He uses a small sealed box enclosure to raise the resonance of a sub woofer.
So he operates only below fs, never above or at it.
He uses eq to contend with the downward slope.
I find this approach very intriquing.
It solves one issue. Previously, you could add more drivers and more power, but it does not lower fs.
Here, he starts below fs. So more drivers and more power do help.
This may be of interrest:
http://www.speakerbuilding.com/content/1014/
http://www.speakerbuilding.com/content/1017/
Btw, sorry to say that speakerbuilding.com seems to be lifeless nowdays but there is still some good stuff there.
http://www.speakerbuilding.com/content/1014/
http://www.speakerbuilding.com/content/1017/
Btw, sorry to say that speakerbuilding.com seems to be lifeless nowdays but there is still some good stuff there.
Subwoofer operation below fs
There are several listing of giant subwoofer systems that operate below Fs.
http://home.comcast.net/~infinitelybaffled/page1IB-NousaineIB1.html
http://home.comcast.net/~infinitelybaffled/page2IB-Gallery.html
http://home.comcast.net/~klone-audio/page13-12Shiva1.html
http://home.comcast.net/~infinitelybaffled/page2IB-IBmanifold.html
They are called infinitely baffled subwoofer, and work this way: If you measure the free air resonance (impedance peak) of a subwoofer, in my case an 18” JBL Professional 2245H, it is approximately 20Hz. When you mount the sub in a manifold, as pictured above, and measure the impedance plot of the system, the impedance peak goes down, in my case to 12.5Hz. This is using 4 of the 2245H’s in a 41” wide by 55” high by 12” deep box, with the top opening in the first floor living room covered by a 12” by 42” open mesh iron grate, and the backs of the subwoofers opening into the basement, hence the name “Infinite Baffle”. The basement is 28’ by 33’ and almost 8’ high, so it is reasonably large. The system is powered by an Ampzilla power amp, feeding two of the 2245’s in parallel on each channel that delivers nearly 400 Watts per channel into 4 Ohms. The system in capable of providing 126dB SPL at 16Hz, at less than 10% THD, at the listening position in the living room, which is 14’ by 22’ by 9’, and has several open doorways into other parts of the house. As mentioned in a previous post, Tom Nousaine wrote up this system in Audio Magazine, in December 1999, in an article. Incidentally, the first link above is on his Infinite Baffle Subwoofer system that Tom Nousaine installed in his house.
There are several listing of giant subwoofer systems that operate below Fs.
http://home.comcast.net/~infinitelybaffled/page1IB-NousaineIB1.html
http://home.comcast.net/~infinitelybaffled/page2IB-Gallery.html
http://home.comcast.net/~klone-audio/page13-12Shiva1.html
http://home.comcast.net/~infinitelybaffled/page2IB-IBmanifold.html
They are called infinitely baffled subwoofer, and work this way: If you measure the free air resonance (impedance peak) of a subwoofer, in my case an 18” JBL Professional 2245H, it is approximately 20Hz. When you mount the sub in a manifold, as pictured above, and measure the impedance plot of the system, the impedance peak goes down, in my case to 12.5Hz. This is using 4 of the 2245H’s in a 41” wide by 55” high by 12” deep box, with the top opening in the first floor living room covered by a 12” by 42” open mesh iron grate, and the backs of the subwoofers opening into the basement, hence the name “Infinite Baffle”. The basement is 28’ by 33’ and almost 8’ high, so it is reasonably large. The system is powered by an Ampzilla power amp, feeding two of the 2245’s in parallel on each channel that delivers nearly 400 Watts per channel into 4 Ohms. The system in capable of providing 126dB SPL at 16Hz, at less than 10% THD, at the listening position in the living room, which is 14’ by 22’ by 9’, and has several open doorways into other parts of the house. As mentioned in a previous post, Tom Nousaine wrote up this system in Audio Magazine, in December 1999, in an article. Incidentally, the first link above is on his Infinite Baffle Subwoofer system that Tom Nousaine installed in his house.
I'm going to check out all the links posted.
Richie00boy, might you have a link for yours? It does sound highly relevant.
We all talked about this on the Giant Subwoofer thread. I'm intriqued, but I'm still reluctant to beleive you can slew through it with no problems.
So I like the Elliot sound approach. But of course I understand that if you don't have to push the resonance up with a small box, then the possibilities are still greater.
Richie00boy, might you have a link for yours? It does sound highly relevant.
We all talked about this on the Giant Subwoofer thread. I'm intriqued, but I'm still reluctant to beleive you can slew through it with no problems.
So I like the Elliot sound approach. But of course I understand that if you don't have to push the resonance up with a small box, then the possibilities are still greater.
I don't understand what you are looking for? There is a 12db/octave roll-off under Fs. These effects can be negated by EQ, in the form of enclosure size and tuning, or electronic signal manipulation.
EBS and IB subs use the enclosure method. They use large enclosures, which decrease the air spring pressures on the drivers, and drastically increase the power to SPL ratio. Enabling increased output below Fs, with little power needed. The trade-off is max SPL achievable per sweep area, which is why you want high xmas 15"s or greater in this application.
ELF, EAS, and LT circuits electronically modify the input signal. In this case you add EQ to negate the drivers natural roll-off. These designs use smaller enclosures to increase the air spring, which lowers the power to SPL ratio. Massive amounts of power and EQ are used to produce SPL level near a normal sealed sub. The lower you try to go the more power required. +1K levels of power for high SPL applications. A driver with high power handling and high xmas is needed to make the most of these types of subs.
There is nothing special about running a driver under Fs. You just have to pick your poison. A large enclosure or huge amps and extra electronics.
EBS and IB subs use the enclosure method. They use large enclosures, which decrease the air spring pressures on the drivers, and drastically increase the power to SPL ratio. Enabling increased output below Fs, with little power needed. The trade-off is max SPL achievable per sweep area, which is why you want high xmas 15"s or greater in this application.
ELF, EAS, and LT circuits electronically modify the input signal. In this case you add EQ to negate the drivers natural roll-off. These designs use smaller enclosures to increase the air spring, which lowers the power to SPL ratio. Massive amounts of power and EQ are used to produce SPL level near a normal sealed sub. The lower you try to go the more power required. +1K levels of power for high SPL applications. A driver with high power handling and high xmas is needed to make the most of these types of subs.
There is nothing special about running a driver under Fs. You just have to pick your poison. A large enclosure or huge amps and extra electronics.
I do not understand this. The Fs is not lowered in a EAS sub either. You just use a box with an Fsc above the passband. That way you know the roll-off will be 12db/octave, and you can just use the generic EQ for any box and driver combo. The EAS method is the easy way of creating LT like gains.
More drivers always help with output above and below the drivers Fs.
You can accept a sub operating below an abnormally high Fsc, but not at normal levels?
EDIT: Not trying to flame you. I'm trying to understand where you are coming from.
Those are some great links.
After reading that Nousaine article, I do wonder why he doesn't consider horn loaded. My simulations indicated you could exceed 120 dB easily @ 20 Hz with two high excursion 12" drivers with much less power than all but the cheapest of plate amps. Required footprint is only about 2 x 0.5m with a large floor to ceiling box. Not that bad really. If I had room I would have done it by now.
When I was working on the design, another who had built a smaller bass horn suggested that it could go well below 20 Hz due to the corner expansion. Given a spare basement, you could also build some very large vented boxes or bandpass boxes to get high SPL @ 10 Hz if unhappy with the extension of the horn.
The horn could actually match the SPL of the IB on the low end, given the same number of drivers. Not that you would pull this off since the horn would be huge then with that many drivers.
After reading that Nousaine article, I do wonder why he doesn't consider horn loaded. My simulations indicated you could exceed 120 dB easily @ 20 Hz with two high excursion 12" drivers with much less power than all but the cheapest of plate amps. Required footprint is only about 2 x 0.5m with a large floor to ceiling box. Not that bad really. If I had room I would have done it by now.
When I was working on the design, another who had built a smaller bass horn suggested that it could go well below 20 Hz due to the corner expansion. Given a spare basement, you could also build some very large vented boxes or bandpass boxes to get high SPL @ 10 Hz if unhappy with the extension of the horn.
The horn could actually match the SPL of the IB on the low end, given the same number of drivers. Not that you would pull this off since the horn would be huge then with that many drivers.
I've played 7Hz test tones on my 4-18" Avalanche IB with no problem and still quite strong on the SPL, but the electronics brick wall there and as far as I know you wont find many combinations of electronics that wont stop you somewhere before 5Hz. Also if your looking for any measurements or want to do some real experimenting here I don’t know how you would as I don’t know of any test equipment readably available that will test anything accurately down this low. BTW, why?
The why is to experiement with infrasonics in music. This thread is a continuation of the Giant Subwoofer thread where this was first broached.
There are 3 pipe organs in the world that have the 64' octave, which has its lowest note, C at 8hz. Is that music, or is it a sound effect?
I am not sure, but I'd like to experiment . I think it is a fascinating subject. If its possible to go lower, OK.
Do you have a link for that 18" Avalanche? I tried to find that once and could not.
There are 3 pipe organs in the world that have the 64' octave, which has its lowest note, C at 8hz. Is that music, or is it a sound effect?
I am not sure, but I'd like to experiment . I think it is a fascinating subject. If its possible to go lower, OK.
Do you have a link for that 18" Avalanche? I tried to find that once and could not.
Have you heard of GOOGLE?
I found it in like 30 seconds...
http://www.frappr.com/?a=photo&gid=31196&pid=451730&src=flash_slideticker
AndrewT said:
He has active correction.
Quote:
"The first two sections are the equalizer. The two last 2nd order filters are in combination a 4th order Linkwitz-Riley filter"
The woofer he is using has Qtc around 0.3 so it is possible to have sufficient gain from BR. Tuning is also low. Resulting in a shelf response that he is EQing flat.
The site seems to have lost all pictures that backed up his article.
Edit:
Here's one sim i made with JBL 2226 in 220L box tuned to 22Hz. Not impossible to EQ flat.
Attachments
Enough woofs, with enough surface area, and enough xmax, and with a little judicious equalization, you're there. Granted, with a single one, you're not going to be able to rumble loud, but you _can_ rumble... And when you get into the folks who build walls out of them, well...
The limiting factors are construction of the chamber (the listening room) and how much $$$ you can throw at it.
The limiting factors are construction of the chamber (the listening room) and how much $$$ you can throw at it.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.