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Giant Subwoofer?
Giant Subwoofer?
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Old 9th July 2006, 08:55 AM   #21
zenmasterbrian is offline zenmasterbrian  United States
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BobEllis, Thank you. Are you saying that you do run regularly below fs?

I understand about the concrete walls, and why spacing the subwoofers out is good.

But can you say more about crossing below fs?
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Old 9th July 2006, 05:24 PM   #22
BobEllis is offline BobEllis  United States
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I'm not really operating below Fs the way Bag End does it. My alignment is more of an EBS (Extended Bass Shelf). If you look at the response of a typical EBS system you'll see that it droops a bit, and depending on tuning it will have a flat section before rolling off.

If you went for a QB3 alignment with my drivers, you'd end up with 8 cubic feet tuned to 28 Hz. This would give you an F3 of 35 Hz. My enclosure is 8.5 cubic feet tuned to 24 Hz. Without EQ, this gives pretty close to a 12 dB/octave rolloff from 40 Hz down to 20, with a 24 dB/octave drop below. If the room gain matched theory, no EQ would be required for flat in room response to 20 Hz.

My room has a set of French doors, windows and a large opening to the rest of the house, so I don't get full theoretical room gain. I use an adjustable Q second order 20 Hz high pass filter to compensate for the missing room gain. For Flat anechoic response I'd need 10 db of gain, and would have an F3 of 19 Hz. I ended up with about 5 dB of gain to get flat in room response.

If you look at the response modeled in WinISD you might think I really don't have a subwoofer if you forget about room gain. That is exactly the point - you probably don't need flat anechoic response to meet your goals. Just remember that to apply a lot of EQ down low you'll need drivers with lots of displacement capability.
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Old 9th July 2006, 05:50 PM   #23
SteveCallas is offline SteveCallas  United States
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How low exactly are you looking to go? If you want high output flat to 10hz (possibly a bit lower) in room, you don't need a 30" woofer, a capable 18" in a large and low tuned ported enclosure will do. Take mine for instance:

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And that's without any EQ.
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Old 9th July 2006, 06:16 PM   #24
BobEllis is offline BobEllis  United States
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Which does an outstanding job of illustrating one of the engineering tradeoffs in the quest for deep bass - size vs. efficiency. I probably need more power than Steve for the same output, even though I start with 94 db/W drivers. (500W each for 105 dB at 20 Hz)
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Old 9th July 2006, 10:13 PM   #25
BassAwdyO is offline BassAwdyO  United States
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My suggestion...

Two 18" adire tumult drivers with anything that fully powers them(without a subsonic filter). Two huge enclosures tuned to the lowest frequency you desire and there you go....

My sub(adire tumult 15" tuned to 16hz via two 18" PRs) produces quite adequate infrasound for my liking... I've played around a fair bit with infrasound and I find that below 18hz its impossible to tell pitch. Different frequencys might make different things rattle, but essentially it's the same feeling you will get in your body.

Anyhow....If you find a pipe organ recording with <15hz content at greater than -10db from reference you'd suprise me
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Old 9th July 2006, 10:45 PM   #26
zenmasterbrian is offline zenmasterbrian  United States
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BenVos,
Might you tell us more about your 32" Clarion?
Is 17hz the published fs?
How did you get it from Clarion, they don't list it.
Rumor has it that such is made by Misubishi. True?
Is the driver's frame rigid enough, won't warp and cause voice coil binding?

May I ask, how much did it cost?

What kind of enclosure do you have it in, sealed, ported, transmission line, other?

Is your enclosure built-in or movable? How big is it? How heavy is it?

How much amp power do you have for it?

tc_60quy,
The conventional wisdom is that while more drivers and an enclosure can go louder, you still can't go below fs.
Most large church organs go to 16hz. Two go to 8hz.

I'm interested in experimenting electronically with this range.

Generally it has been assumed that you can't go under fs. Now, I'm seeing some people call that into question. Do you have any experience with specifically trying to go under fs?

phase_accurate,
Thank for that European patent. I am fascinated with it and still studying it. I knew that by feedback methods you could go under fs. But that is fairly exotic and requires a special driver.

It looks like this Bag End does not use feedback. I still need to look at this further.

Bag End says they can go down to 8hz. Do they explain why they want to do this? I want to understand more about how they are pitching their product.
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Old 9th July 2006, 10:59 PM   #27
zenmasterbrian is offline zenmasterbrian  United States
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Skramstad, I'm very interested in understanding what you are saying. Might you know of any text which describes what you are saying, being able to build an enclosure to go under fs?

The most theoretical loudspeaker book I know of is by Martin Coloumbs.

fs is the driver resonance in free space. If you enclose it in any way, the resonance goes higher.

If you try to slew you signal done into the resonance and below, the sound goes away.

The only way I can think of to have an enclosure that gives a lower resonance, would be to do something like Bose does with their real tiny subwoofers.

The design of such is covered in the Coloumbs book. We can copy a patented design if it is for personal research.

Bose uses real tiny drivers. Say I built the same type of thing with an 18" driver?

The Bose design, as I remember, has three chambers. One is on one side of the driver. The other two are on the other side of the driver. These second and third chambers are connected by a tube, and a tube connects the third chamber to the outside.

Such a box could have its own resonance, below the driver fs.

Maybe then you could go under fs. I'm not sure. I don't know what the practical limits of such a design are.

Personally I've never cared for Bose, because it seems like they mostly want to make it small. What they accomplish is impressive, but I don't share their objective.

But if their approach could also be used to go under fs, then I could be interested. I fear that their design is quite complex to realize, and probably does have some real limitations.

I know that in the 1970's the Allen electonic organ company developed some big coffin like speaker box to do the 16hz or 32 foot organ octave. Maybe it worked something like this?
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Old 9th July 2006, 11:04 PM   #28
zenmasterbrian is offline zenmasterbrian  United States
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Mashaffer,

Transmission line enclosures are favored by many because you can get very close to fs, but not below.

If you are saying you can go below, then I feel that it must be with massive amounts of power.

Of course the cone will move no matter how low you want to go, but the efficiency is real low.

Are you actually driving your system with a signal generator, and starting at like 200 hz, and then going down below its resonance?

I don't see how you could make this work in a musical application?

Tell me more. It does seem that BagEnd has something. I need to study it.
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Old 9th July 2006, 11:11 PM   #29
zenmasterbrian is offline zenmasterbrian  United States
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phase_accurate, post #13, Thank you for that link to Elliot Sound Products. I am going to have to study it. They say it drops 12dB/Octave below resonance.

Lots of subwoofer drivers have fs from 30hz to 25hz. I wish there were more that were lower. So to get to 8hz will be real tough.

I had wanted info about giant low fs drivers. But it seems there is more interest in ways to go under fs. I'm finding this fascinating.

Along with eq schemes to go under fs, there can also be eq for finite room size considerations. The room becomes the front part of the speaker enclosure when you go that low.

Thanks to all of your I'm still trying to read and understand your posts and fascinating links.
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Old 9th July 2006, 11:28 PM   #30
zenmasterbrian is offline zenmasterbrian  United States
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Steve Callas #23, What is that you've got a picture of there? Did you make that? Who makes that? Please tell us more about its design.

You say it works to 10hz. Have you actually driven it with a sign wave generator, and slewed down from say 200hz, down to 10?
And are you sure you are hearing the fundamental, and not overtones or some kind of rattles?

Rob Wells #17, I would ask you the same kind of question. And what exactly are tempests, do you have a web link, or give me a specific post number.

badman #18, What kind of subwoofers are you referring to exactly?
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