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Old 6th July 2006, 10:29 AM   #1
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Default Giant Subwoofer?

Where can I get a raw driver for a Giant Subwoofer? I'm talking about something that has a very low free space resonance. Some pipe organs go real low. Both the Radio City Music Hall one and the Wannamaker's one have 64' stops. This means they have the C note two octaves below the lowest C on a piano. Its about 8hz.

Some would say this is not sound. I don't know. But I want to experiement. I want to make a large built in subwoofer with a highpower amp hardwired to 220VAC.

I have heard rumors of 32" and even 60", and of frequencies as low as 5hz.

What raw drivers do you know of bigger than 15" or 18", and with very very low free space resonances.

I think this an ideal feature in a media room.

You can get away with this so long as you cross over low enough, and the rest of the program material goes to your channel speakers, and if your channel speakers go low enough themselves.

Think of this as an InfraWoofer.

Who knows of giant raw drivers?? How much $$$? Specs? Anyone else done anything like this?
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Old 6th July 2006, 11:21 AM   #2
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Fostex has a GIANT woofer.

http://www.fostexinternational.com/d...pdf/fw800n.pdf

I think Clarion also has a similar sized behemoth.
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Old 6th July 2006, 12:05 PM   #3
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You don't need that size woofers to get to 8 hz. I think you need something like Bagend-woofers (www.bagend.com)

Have fun

Thomas
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Old 6th July 2006, 10:49 PM   #4
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With a correctly designed large format basshorn you can go an entire octave below the drivers fs without pushing it beyond xmax even at full power.

I have not any experience with other subwoofer systems than horns, but I would guess that a small bandwith helmholtz resonator system could be designed with the right amount of acoustic impedance to do a similar job one octave below fs.
Maybe someone has done some research on the subject?
If this could be a solution it should be possible to reach your 8Hz goal with ordinary 18" carwoofers with an fs of 16Hz.
The larger exotic woofers tend to be very expensive compared to the results you get.
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Old 7th July 2006, 10:13 AM   #5
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Mikael, I've heard rumors about Clarion. Some years ago someone from Cerwin-Vega told me. But I can't confirm it. They say the drivers are made by mitsubishi, and that they are used for car audio competitions.

Of course I have no interest in such car audio.

I'll look at your other link.
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Old 7th July 2006, 10:59 AM   #6
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skramstad

Thank you. As I know, you really can't go below Fs. Of course the speaker cone will still move. But the efficiency goes to almost zero.

Any enclosure only raises such resonance. This applies to both front and back loading. So it applies to horns. It applies to transmission line enclosures, everything.

This is my understanding. So, please elaborate.

tlmadsen

thank you for telling me about bagend. It is interesting. They seem to be using somekind of a feed back approach. That is, you use something else to tell where the cone of the speaker is, or at least how fast it is moving.

I've heard of this being done with a laser beam reflecting off of something near the center.

I've heard of this being done with a second voice coil used to sense velocity.

I believe that Bagends INFRA technology must be something like this. I couldn't see on their web page a specific description.

A company in San Jose, Velodyne, makes something like this. I think their subs go down way below Fs.

This is another way to do it.

I'd like to explore all the posibilities.

Mikael

I looked at the Fostex driver. Giant it certainly is, 31"
They say it goes to 18hz. Not bad, but I'd like to try and go lower.

Of course a driver that big should be crossed over much lower than say a 12" or 15". But that is ok.

Any ideas about cost?


Any body got any other ideas in general?
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Old 7th July 2006, 11:03 AM   #7
sreten is offline sreten  United Kingdom
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Hi,

Search on a guy called graham holliman.
Designed some sort of infrasonic generator.
And mass loaded arms for a cut-off of 3Hz.

/sreten.
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Old 7th July 2006, 11:36 AM   #8
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Efficiency going to almost zero is a bit of an exaggeration but you will need lots of power to go significantly below Fs.

Take a look at Servo-Drive subs - at one point there was some DIY support, but I think Tom is strictly commercial now. Tom used something like this for sonic boom simulators for the USAF, IIRC.

If your room is fairly small and solid, you can gets lots of low end boost from room effects like the car guys do. Sprinkle some low Fs 18" drivers liberally around a room with four concrete walls and a concrete floor and and enjoy.

I'm in the mid teens in room with a pair of JBL2245Hs in a quasi 6th order alignment tuned to 20 Hz (the driver's Fs) 500W each is enough for over 105 dB. The cannons on Telarc's 1812 Overture CD sound quite realistic. (supposedly lots of info down to 5 Hz.)
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Old 7th July 2006, 01:08 PM   #9
BenVos is offline BenVos  Netherlands
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Quote:
Originally posted by zenmasterbrian
Mikael, I've heard rumors about Clarion. Some years ago someone from Cerwin-Vega told me. But I can't confirm it. They say the drivers are made by mitsubishi, and that they are used for car audio competitions.

Of course I have no interest in such car audio.

I'll look at your other link.
I am using the 32" Clarion woofer in my DIY dipole Sub.
FS is about 17 HZ
I am using it up to 80 Hz max.

The normal speakers (DIY) are 5 http://www.metrum-acoustics.nl/ dipole hybrid ESL's with 2 scanspeak woofers.

Verry good and deep bass.
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Old 7th July 2006, 01:47 PM   #10
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Howdy! If your going big, why not put 4 15 inchers in a box and use active eq to flaten the response?
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