Box Frequency , Subsonic Filter , and Low Pass Filter

[Alien Mantis]

Good information.

I have been studying graphs like these. If you understand specs and graphs, you can predict how a certain setup will perform.

I was looking at Xmax when choosing a sub. That is one reason I went with the Type R. It has an 18mm Xmax, which is pretty good for a sub that costs around $100, and can handle 500watts RMS +.

I understand that cone diameter + Xmax = SPL.
The more air you can move, the louder the sound.
The faster you can move it, the more controlled it will be.
A 12" sub that has an Xmax of 10mm, is roughly equal to a 10" sub with 16mm Xmax.
Then you factor in the box type and volume, and the power you are putting to it, and you have your setup.

I understand what you mean about the SS filter. If your setup has a SS filter, you can cut all the freq's below that setting, and you don't run the risk of over-excursion on your cone due to it trying to play those super low freq's, even though they drop off sharply anyway on their own.
( This is what "roll-off" refers to. Or sometimes they call it "drop-off". )

Sealed boxes control roll-off much better than ported boxes.
It's always best to just cut those freq's, then the signal never even gets to the subwoofer, but my amp does not have an SS filter on it.
I wish it did, but if you don't try to overdrive your sub, roll-off should keep you safe.
The other benefit of the SS filter is: since the amp isn't even trying to push those freq's, more of the amps power can go towards driving the signals it is supposed to be pushing.

I totally love SS filters.
But my amp doesn't have one.
I also love subs with long linear excursion numbers, because I know I can drive them harder and they will take it and ask for seconds.
A sub with a small Xmax number is easy to bottom out.
They are tight, fast, and responsive, but they don't move as much air, and can bottom out easier.
Less air = less SPL.

It's always a trade-off.

The setup I am running now seems to be good. It's a nice compromise between SPL and SQ. I was thinking about trying the sealed box, but I think I will just stick with this setup. The more I listen to it, the more I like it. So it's all good.

[talnlnky]

Originally Posted by Alien Mantis

Good information.

I have been studying graphs like these. If you understand specs and graphs, you can predict how a certain setup will perform.

I was looking at Xmax when choosing a sub. That is one reason I went with the Type R. It has an 18mm Xmax, which is pretty good for a sub that costs around $100, and can handle 500watts RMS +.

I understand that cone diameter + Xmax = SPL.
The more air you can move, the louder the sound.
The faster you can move it, the more controlled it will be.
A 12" sub that has an Xmax of 10mm, is roughly equal to a 10" sub with 16mm Xmax.
Then you factor in the box type and volume, and the power you are putting to it, and you have your setup.

I understand what you mean about the SS filter. If your setup has a SS filter, you can cut all the freq's below that setting, and you don't run the risk of over-excursion on your cone due to it trying to play those super low freq's, even though they drop off sharply anyway on their own.
( This is what "roll-off" refers to. Or sometimes they call it "drop-off". )

Sealed boxes control roll-off much better than ported boxes.
It's always best to just cut those freq's, then the signal never even gets to the subwoofer, but my amp does not have an SS filter on it.
I wish it did, but if you don't try to overdrive your sub, roll-off should keep you safe.
The other benefit of the SS filter is: since the amp isn't even trying to push those freq's, more of the amps power can go towards driving the signals it is supposed to be pushing.

I totally love SS filters.
But my amp doesn't have one.
I also love subs with long linear excursion numbers, because I know I can drive them harder and they will take it and ask for seconds.
A sub with a small Xmax number is easy to bottom out.
They are tight, fast, and responsive, but they don't move as much air, and can bottom out easier.
Less air = less SPL.

It's always a trade-off.

The setup I am running now seems to be good. It's a nice compromise between SPL and SQ. I was thinking about trying the sealed box, but I think I will just stick with this setup. The more I listen to it, the more I like it. So it's all good.

there is more to SPL than total cone displacement... get two 12" subs, put one in a 1cuft sealed box, the other in a 2cuft @ 35hz box, and then play 35hz tones... the Ported box will be a lot louder, but it'll move about 1/4 as much.

The Original Cerwin Vega Stroker subs had a very small x-max... and they were always present at dB Drags World Finals (spl competitions).

If you can cause there to be a lot of resistence on the cone, and still move the cone... you'll have more spl... ported & bandpass boxes do this.

I've only once ran a subsonic filter, I know my installs inside and out, i know what I can get away with, and what I can't. I know that with a given ported setup I can give two, three, or even four times the rms value as long as I keep it limited to a few tones, and only for short burst of time. I've setup installs for people before, told them exactly what they could and couldn't do... and then watch them go to a competition, and try to push the limits.. and BAM... blew the subs because they "thought it could take more".

Best thing anybody can ever do to increase their knowledge of stereo, is to download WinISD, begine designed ported boxes with it, and then make some of those boxes and test them with test tones... you learn a lot fairly quickly.

[Alien Mantis]

I was actually looking at a Cerwin Vega before I bought the Type R.

I had my choices narrowed down to 3 subs:

The Type R, a Cerwin Vega, and an Infinity Kappa.

The Infinity looked nice, had an Xmax of 17mm, could switch between 2 and 4 ohms, but only handled 350watts RMS max.
I'm sure it could handle a 400 watt amp on it, if I was careful to set the gain correctly on the amp, which I always do.

The Cerwin V was nice too, but it only had like a 14mm Xmax.

The Cerwin and the Infinity were both $10 to $20 more.

So in the end... the Type R won.
The Type R had the Xmax, the power handling, the reputation, and it was the cheapest.

I'm sure ANY one of those subs would have worked just fine, and I probably wouldn't even be able to tell much difference between them, if any.

Like you pro's say: the magic happens in the "mid-range".

[_S7V7N_]

Nice info guys, I'm enjoying reading all the Knowledge.