Low FS

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What is a good choice for a subwoofer with an FS below 20 hz, because my main towers (dual 10"), can go well into the 30s, so I was thinking an X-over of 40-50hz, so upper bass is not needed at all, but I'd like it if I could get usable output in the 10-15's.

Oh and this needs to be on a budget too :).
I know these are mentioned a lot anymore, but the Atlas 12 and 15 are extremely nice drivers for $145 and $160 respectively. Their Fs is higher than 20 Hz at around 23.2 Hz for the 12 and 21.5 for the 15, but they really dig down deep, and have XBL^2. Also, you may still want to consider having the crossover somewhat higher than 40-50 Hz, depending on the levels that you intend to play at, and depending on the SPL capabilities of those mains. Personally, if I were on a budget I'd go with the Atlas 15, probably in a sealed box. Instead...I broke out the CC and bought a pair of Avalanche 18s, so now I'm in debt but have infinite bass at my hands :)
Basically a linkwitz transform is an EQ, which is what I am trying to avoid, because it uses a LOT of amplifier power, and gets to the limits of excursion faster, AFAIK.

I'd rather have something under 20 because I am looking for something that has deep full bass on a budget that integrates well with my towers which will have dual 10" woofers. and should have good output to 30hz anechonic. Maybe 250 or 500 watts, because any room I can think of using it in is quite small (12' x 10' x 7.5') or thereabouts, the largest I can think of is (22' x 12' x 6').

I am just batting around ideas right now, and trying to find a woofer with a really low FS, and the best I have seen in 15, but I'd love to find 10-13hz, which probably doesn't exist.
Why such an emphasis on Low FS? There are only two factors that effect the Fs and they are the suspension spring constant(well it might not be perfectly constant) and the mass of the moving assembly (aka, the cone and voicecoil). If you have a tighter spring, you will have a higher Fs, with a looser one, lower Fs. More cone mass will lower Fs while less mass will producea higher Fs. Cone mass will have a tremedous effect on efficiency,but I believe the springiness of the suspension will not so much.

In most cases, however, neither cone mass nor the spring constant will have a significant effect on the maximum low frequency output(below 20hz) because at these low frequencys the speakers act as a pressure source where displacement is key. Therefore you need high excursion and surface area to create the most swept volume enabling the maximum sound pressure.

Try this out, open up WinISD and model up two of the same enclosure/woofer. Then using the parameter bar on the bottom of the project window change the Fs of one driver to double the original value. The transfer fucntion WILL change, but ignore this and go to the SPL graph. Imput equal power to both drivers and look at the low frequency response(below30hz) and they will be nearly identical.

This idea that having a low Fs will make your subs play any lower is proposterous. YOU NEED DISPLACEMENT!
Usually, they add some mass instead of adding a looser suspension. Trading some efficiency to lower Fs instead of trading SQ.

But yes, to an extent, the suspension is not that stiff, it's foam, but rubber for 10+ mm of Xmax is not a good idea...

The suspension doesn't have much effect on the sound above Fs, it's the Le that's slowing down the transient response, because the magnet is fully in control. So a stiff or a loose suspension is not that important.
bjackson said:
trying to find a woofer with a really low FS, and the best I have seen in 15, but I'd love to find 10-13hz, which probably doesn't exist.

It does exist, but you need to pay for it. The Parthenon motor got a Fs of 7 Hz. It would cost around 5k$ to get one.

You could also hunt for a old Phoenix Gold Cyclone, the Fs is 10 Hz. You could probably fit this into your budget if you are lucky.

There's also the new Maelstrom drivers from Adire Audio, the dual 2 ohms version got a Fs of 14 Hz but the price is quite high.

It seems that Adire Audio is moving in the high end. No budget drivers anymore if dealers respect new MSRP prices.

You're left with Ascendant Audio my friend!
Masters thesis on ultra low Freq. mic.

So to calibrate mic. I need a extremely low freq. speaker. I ended up with 2 design. One was a dual Swan TA 305's in a dual B4 arrangement. First box tuned to 30ish hz. second box tuned to about 15hz. In actually with some stuffing in it and a nice preamp filter i go down to about 11hz. It was more of a burp though (1w/1m=89 db). But the down side, the box was about 12cf. When I was running these speakers with a 100w signal, running through the freq. range, I found out later I was pinging the FS of the building I was in! :D

The second design was a modified NHT 12" in a 9-12cf box tuned to about 18hz. It would get down to about 16-17hz just fine and then have a nice gradual -3db roll off. Again, not too much music around there.
I did have a nice time when I built two speakers at home with the Swan 305 setup. They really shined in the home threatre when I played "EARTHQUAKE". Or any really low frequency speakers....
Anyways have a good one
having a stiffer or looser suspension will have little effect on the actual impulse, but the decay will be effected dramatically.

So what if we created a speaker without a Fs?

The speaker would have no spider or surround, it could simply use a cylinder with the cone set inside as a piston with rings, just like the pistons in a car. then voice coil could be centered using the same concept adire uses to center their coil assembly on parthenon.(That white plastic thing that the moving assembly slides on)

Xmax would need to be an insane value because the coil would eventually move out of the gap if a DC signal was applied or one side of the waveform was consistantly higher in level than the other. But perhaps a feedback loop could be employed that would use a low level DC signal to slowly recenter the coil in the magnetic gap when it moves close to the XMax point.

any thoughts?
low fs.

This is an interesting subject. I have always wondered why they say you cannot work a driver below it's Fs. If you took a large driver with a high Fs (say 15 inch Fs of 45hz) why would it not work well below that frequency? It would still move air. It may not be as efficient below res. but I have always questioned this. Any input? regards, Steve
Adire amazes me. Its such a strange audio company. They have a diverse product line, yet there are many things they do not offer to the basic consumer. It doesnt really seem like they have the marketing priorities of "we want everyone to own a product of ours," but more like "we want everyone to have heard a product of ours" which I personally think might not work out the best for them. But what do I know, I'm no buisness expert. When it all boils down to it though I truely believe marketing is what will make or break a company.

Not to say that a company will always do good if they have good marketing, but they have alot better chance at it.
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