Need help modeling a few subs. Am I doing this right?

[alfa147x]

I'm trying to compare a few subs so I figured I would I would model them using WinISD.

So to get more familiar with the application I started with the Dayton Audio TIT280C-4 10" Titanic Mk III.

So I plugged in the Goldwood E-10SP 10" Vented Box:
Approximately 1.1 ft³.
Dimensions: 16" H x 12" W x 14.25" D.
Port: 10-3/4" W x 1-15/16" H x 10-1/4" D.

Which I'm guessing this box is much too small. Right?
Is there a better way to compare subs?

Thanks for the help!

I got this:

 

[Anubis]

your port tune looks wrong, 100Hz is way too high

 

[Plugers]

FS is 29.22hz. I'd start port tuning at 30hz. Move it around from there.

Is this for home theater? You would probably want to keep tuning low if it is.

For music it would be good too, but may sound a little "punchier" with it a tad higher.

It's all personal preference though. Watch port velocity and cone displacement at the amps RMS rating.

 

[kornphlake]

The non-pro version of win-isd is probably easier to use for a beginner. What you should be looking for is a plot that is fairly flat between say 30hz and 120hz with no massive peaks or valleys on either end of that range, an even curve to zero is fine on either end, but not a peak or valley. A 1cuft box is too small for just about any sub.

 

[Ophir]

To expand on what the other posters mentioned, it's really a balancing act between frequency response, frequency extension, output, box size, port air velocity, port length, power handling (cone excursion), and 1st port resonance.

You need to find a set of parameters you want to build around (frequency response, box size) and model around those.

Couple of rules of thumb:
- Frequency will roll off at 24dB/octave and cone excursion increases dramaticaly below tuning, so you generally want to tune just below your target freq as system performance decreases rapidly below tuning. For movies, response should extend to 25Hz or lower, music 30Hz or lower. For movies many tune below 20Hz, even to 10-12Hz, 14-18Hz is a good target unless you want a huge box.
- Port air speed should be kept below 25m/s at max power (raise port cross-sectional area to lower port air speed)
- 1st port resonance should be above 2X your crossover frequency, preferably 2.5X (raise box volume and/or decrease port area to increase)
- Increasing port size will mean the 1st port resonance decreases so box size will need to increase to maintain a given tuning freq.

As you can see, it's a balancing act you reach through trial and error; however, if designed properly, a ported sub offers nearly unparalleled driver efficiency and system response above tuning.

 

[Howard]

I wasn't even aware that there was a non-pro version. Just use the pro version.

I've heard 17 m/s bandied about as a rule of thumb for port velocity. Make sure the input power is > 1 W when checking this curve. Anyway, Ophir knows what he's talking about.

 

[kornphlake]

The non-pro version has fewer variables to get confused with, once you enter the driver parameters it will recommend an enclosure size and port configuration that is usually a very good starting point, from there you can tweak the size or tuning a little bit. If you don't know what all the extra parameters in the pro version mean, it's easier to use the non-pro version as the software somehow figures out a near optimal configuration without the user's awareness.

 

[Ophir]

I've heard 17 m/s bandied about as a rule of thumb for port velocity.

Yeah, it's probably safer to aim lower on the port velocity to totally prevent chuffing. It'd be awful to build the box then realize you should have been more conservative on the port velocity. That said, my understanding is that with a correctly flared port 25m/s is still low enough to maintain laminar flow through the port.

Make sure the input power is > 1 W when checking this curve.

I generally enter the amp's max RMS power into WinISD and model around that. You may even want to enter the max peak power if you want to be conservative, that way you can design around max cone excursion and port velocity.

 

[alfa147x]

Real quick I did a comparison of ported vs sealed. I'm sure I missed something but here it is:

 

[Howard]

What's the point of a comparison like that? Are they both the same volume?

 

[alfa147x]

What's the point of a comparison like that? Are they both the same volume?

I was trying to compare the driver in a sealed enclosure vs ported

 

[Howard]

I was trying to compare the driver in a sealed enclosure vs ported

With what criteria?

 

[alfa147x]

With what criteria?

With every thing but enclosure type set the same. Did I miss something?

 

[Howard]

With every thing but enclosure type set the same. Did I miss something?

Yes. Vented is tuned way too high.

 

[Ophir]

With every thing but enclosure type set the same. Did I miss something?

Please read my 1st post in this thread. To answer your question, 1 cu. ft. is small for a ported driver, even a 10" one. Try starting at 2 cu. ft. As Howard said 42Hz tune is also high, try tuning to ~20 - 30Hz. Also, look at using two 3" ports.

 

[kornphlake]

Please read my 1st post in this thread. To answer your question, 1 cu. ft. is small for a ported driver, even a 10" one. Try starting at 2 cu. ft. As Howard said 42Hz tune is also high, try tuning to ~20 - 30Hz. Also, look at using two 3" ports.

two 3" ports might be too long to fit in the box, I'm calculating about 19" length ports to tune at 30hz in a 2ft^3 enclosure, a cube shaped box would be about 15" on each side, it wouldn't be impossible to alter the box to be rectangular, a 23x10x15 box would have approximately the same volume if that doesn't interfere with space or aesthetic constraints. As the size of the box increases the port length decreases, which makes it easier to find an attractive port to install in the box.

 

[Plugers]

Ran it through BBPro real quick:

at 400w it will have a bit of port noise at 20hz. you would want to slot port it and wrap it around 2 sides.

How much power are you using?

 

[kornphlake]

Hang on guys, I ran the sim in winisd non pro using the TS parameters from PE's website and I'm getting a very different looking plot. I'm guessing the OP made a mistake converting units or used the wrong units for one or more parameters.

This is the kind of plot you're looking for, nice and flat with a gentle roll off at the lower frequencies.

 

[mazeroth]

A guy I know on the Parts Express Tech Talk Forum just posted this tutorial:

http://gonecatfishin.net/Winisd.htm