Custom subs, no TSP's, help please

[Krakin]

So I saved this before the site went down

For determining Thiele/Small parameters you need to find a very quiet room with no wind so as to not affect the results of the testing. Ideally you should find a way to secure the subwoofer to a frame or suspend it in free air, but it will most likely be that people won't be able to easily do this so putting the sub on a very sturdy table magnet down is okay to work with. If the motor design has a vent in the T-yoke you need to allow room underneath the drive as to allow air to flow in and out properly.

First I want to state that there are many variables and chances for things to go wrong when finding measurements. Speakers are at best variable clusterfucks, and you will NEVER find perfect results in practice.

Now let's start out with figuring out some of the easier parameters.

Re:

This simply measuring the DC resistance of the coil(s).

Fs:

Set up a frequency generator to your amp/subwoofer and connect a DMM to the sub. Start the sine wave generator at 100 Hz and slowly lower the frequency being played. As your sub gets closer to its free air resonance (Fs) there will be a large increase in the impedance. At the largest value of impedance you have found the Fs of the driver.

When the frequency being played has reached the sub's Fs the impedance of the speaker is 100% resistance with no inductance. While the frequencies below the resonance of the driver are inductive and the frequencies above resonance are capacitive until you hit the speaker's linear region, and then finally followed by another inductance rise.

Sd:

Sd is possibly one of the easiest parameters to find as it is just the cone area of the speaker, you pretty much just need a ruler. First measure the diameter of the speaker cone including one third of the surround on either side. To calculate the area you divide the diameter by two to find the radius. Then square the radius and multiply by Pi or 3.142.

Final equation should look like this, Sd=r2 x 3.142.

I'll post more on how to find parameters later, but I have gotten bored typing this so I'll continue later with some more complicated examples as it is 1:30am here.

[CleanSierra]

Wouldn't buy a sub without t/s specs.

Did you see those bitches? I would have bought if I were wanting something beastly. How stiff is it to push the cone down?

[ParDeus]

There pretty stiff, lol, but not as bad as my DD's.

[ParDeus]

Wouldn't buy a sub without t/s specs.

Are you aware that most manufacturers just pull one random sub and test it?

Many of the TSP's change after break in, so technically you ARE buying a sub without TSP's. I've seen the manufacturers numbers be off in the past, according to a shop in FL that I dealt with.

[never knows best]

maybe one of these-

http://www.parts-express.com/dayton-audio-dats-dayton-audio-test-system--390-806

[CleanSierra]

maybe one of these-

http://www.parts-express.com/dayton-audio-dats-dayton-audio-test-system--390-806

I believe he already bought that ^^

[never knows best]

[Joe X]

You need no more than some free phone or PC software a resistor, multimeter, cable and your amp to get some reasonably close numbers at least if your subs have some break in.

Care to expand on this, sir? I'm liking where this is going...

Ok check this out:

http://sound.westhost.com/tsp.htm

The audio oscillator device shown in figure 2 can be implemented with phone / pc software, for calculating Vas you get to choose between a sealed box or (if you don't have one) through mass loading the cone.

I have not tested their spreadsheet though so I recommend testing it and your setup with a driver with known parameters first.

[kirill007]

So, I've got 2 Corey Dean specials- 12", Havoc motors with Zv4 softies, dual 10" spiders, titanium baskets, 4 layer flatwound with the black high temp coating.

My computer doesn't work with my DATS, so I'm sort of lost. It looks like these will be coming out of my car, and going in the Tundra.

Now, I wanted to do a 4th, but that is pretty hard without the TSP's.

Does anyone with custom sub experience have any ideas on what parameters tend to remain constant with a custom sub?

Taking this into account, could I get some ideals specs on an enclosure? (it's ok if you get some on your shoes, as pissing in the wind sucks)

I'd like to build a ported enclosure and a 4th, to start testing with. Size is, well, behind the front seats of an extended cab Tundra. Power will be around 2200-3k for now.

Also, what would you rate the power handling of these at? I'm anal about not clipping, and do my best to only play clean music.

Thanks guys...

Figure out why DATS won't work on your computer, or use someone elses.

The only thing you can be sure of with a custom subwoofer is that everything is unknown.

[Borris The Blade]

Those are some sexy ass subs! I just love fat surrounds and TI baskets.