World's smallest subwoofer?

[ByronInLawrence]

I found someone was having a special on a pair of Peerless 830855s (don't remember who). It's the smallest driver I've ever seen described, by the manufacturer, as a subwoofer - 4"!
http://www.tymphany.com/files/SDS-P830855%20Rev1_0.pdf
The idea of a 4" subwoofer intrigued me and I figured I could use them for my computer.

I measured impedance with Dayton's WT3, and modeled them with Audua's Speaker Workshop (I never trust manufacturer's specs). Even though Tympani's data sheet said they're ideal for sealed boxes, SW modeled a much better response for a pair in a 14.3 liter ported enclosure tuned to 53Hz. As you can see in the photo, I put them on opposite ends of the same 14.3 liter cube with a single port, even though they will be driven by separate amplifier channels. After building it I was disappointed with the very loud chuffing, and a loud resonance when playing a 45Hz test tone.

Next day, I did some nearfield measurements of both drivers, and of the port with Holm Impulse. The two drivers were driven by separate channels being fed the same signal. I had to take time-aligned measurements of the two drivers separately, sum them, then sum that response with the time-aligned port response, all in Impulse. I then taped an extra 1cm, 2cm and 3cm on the end of port and repeated the measurements. I got a much nicer response with an additional 2cm on the port. I was a bit surprised because usually SW's calculations are spot-on.

All-in-all I'm impressed with what Peerless can get a 4" woofer to do. Some people may be wondering whether or not they can be used as a full range driver. I would not recommend it. I listened to some music, and thought the mids were pretty muffled.

This project got me wondering just what a subwoofer is. That is: how does a driver described as a "subwoofer" differ from the same size driver described as just a "woofer". Is it their inability to play mid bass, and a need for a low X-over point? Just wondering if anyone has any ideas.

[GloBug]

Yes, thicker cone, heavier, generally more excursion etc, things that rob it of accuracy help bolster it's performance at a lower frequency.

[NEO Dan]

Hey Byron,
Is the (Volume of Sealed Box) 35.311'³ used in the VAS calculation?

[ByronInLawrence]

Neo Dan,

That's a curious glitch that Speaker Workshop has. I didn't use the sealed box method for calculations. I used the added weight method. But SW puts that value in the driver description anyway. I didn't build a 35^3 speaker cabinet.

-Byron

[NEO Dan]

you interested in ~35hz?

[revboden]

Originally Posted by ByronInLawrence

This project got me wondering just what a subwoofer is. That is: how does a driver described as a "subwoofer" differ from the same size driver described as just a "woofer". Is it their inability to play mid bass, and a need for a low X-over point? Just wondering if anyone has any ideas.

I think it depends on what the marketing department needs to sell more of.

I always thought of sub-woofers as just that, a driver with a Fs 20-30Hz that filled in below the woofers (~60Hz). But I'm just an old IATSE sound engineer, most of my career I only used Subwoofers for "effects" so what would i know.

later,
rev.

[NEO Dan]

No to 35hz eh? How about 40hz, it's smaller and a bit more efficient.

This is 1/2" sheet stock.
~17-5/16" x 6" x ~29-7/16" hwd

[ByronInLawrence]

Hi NEO Dan,

I don't understand the question. I'm not planning on building any more subwoofers for a long time.

-Byron

[sofaspud]

Hey Byron, I remembered seeing these Tang Band subs in a PE flyer and thought you might be interested. Maybe it's the upper freq response that is used to categorize subwoofers? I'm also intrigued by little subs that can provide usable output <50Hz. Looks like a neat PC multimedia box you've put together. Where did you set the LPF?

[bjorno]

Originally Posted by sofaspud

.. a neat PC multimedia box ..

Hi,

FYI, A less than 1 liter box suggestion using two TB-W2-1625SA:

b