Ported Subwoofer Build Projects

**CZ Eddie** · **12-03-08, 12:01 AM**

Guys,

I am still learning WinISD. I recently discovered the Excursion tab and I'm trying to model a Tempest-X "LLT" enclosure using it. But whenever I go larger & lower than DIYcable's recommended 12 cu.ft. 16hz enclosure, I start to exceed Xmax.

My goal is an enclosure that has low decay like a sealed enclosure (quicker sounding). But that offers more SPL than a large sealed enclosure. So that has led me to try the "LLT" to see if it's the compromise I've been looking for.

Is what's indicated in the chart below going to cause me problems for Xmax? This is with 600 watts of input power. It looks pretty bad to me. But I just can't get any decent LLT to model without exceeding Xmax somewhere?

The Tempest-X is rated at 27mm of "physical" Xmax.

**thxgoon** · **12-03-08, 01:36 AM**

You won't be disappointed with an LLT.

Don't worry about exceeding xmax. If the response looks good and the max spl looks good then just build the subwoofer. You can either use an amp that isn't powerfull enough to exceed xmax, or you can take the risk and use common sense to turn things down when it gets harry. After xmax, there's xmech which is the distance where the voice coil actually smacks the sub and gets damaged. I don't know what xmech is on the Tempest.

The good news is you're getting a lot of performance for not a lot of power.

**thxgoon** · **12-03-08, 01:41 AM**

Just modeled your design and response looks pretty good. Are you limited to 16 cubes?

**Aaron Gilbert** · **12-03-08, 02:09 AM**

I'm with thxgoon, design looks good to me. That's the beauty of a larger enclosure (some might say the downfall), it takes less power to reach your excursion limits. Don't think of it as being easily overdriven - think of it as a reduction on your power bill.

Back in the old days of speaker design (ok well late 80's anyhow), it was understood that a larger woofer and/or a larger enclosure are more efficient than smaller when it comes to reproducing frequencies in the bottom two octaves. Nowadays, it seems some people are under the mistaken impression that a larger diameter woofer inherently takes more power to drive than a smaller woofer, or that it will cease to function if your amplifier doesn't have power equal to the thermal rating of the voice coil. Not saying you are one of these people, I'm just saying...

My Tempest-X is also tuned to 12Hz and has only about 11 cubic feet. My amplifier is only 400 watts, and that's more than enough for me. 16 cubic feet is huge! I'd suggest looking beyond the almost universal 'Get a EP2500!' amplifier recommendation and look for something a little more sane. In a box that large, even 300w would mean gobs of output, 500w would be the limit I'd go. 400w would keep you just under 27mm excursion from 10Hz and up.

**Mike P.** · **12-03-08, 02:59 AM**

Raise the tuning to 15 hz and input 500 watts. You'll get more output from 14 hz to 25 hz and still be within Xmax compared to what you modeled.

**CZ Eddie** · **12-03-08, 07:48 AM**

Thanks, guys. I already have an EP2500. The 600 watts is the x4 multiplier for a quad set of Tempest-X. I'm not limited to 16cu.ft.

I've had sealed boxes and 18hz tuned boxes among others. I want to try a lower tune box this time around.
Though what Mike just said sounds good, so I'll have to model that later tonight when I get home.

**Ricci** · **12-03-08, 02:07 PM**

I would not tune that low (12hz) with a single Tempest X or even a single of most 18" for that matter. You'll be sacrificing some output in the bass rich 20-30hz area with movies by doing so because your single driver will be asked for huge excursion levels right in that range. I think 13ft tuned to 16hz with an 8" port is a better idea. This should be good down to 14hz.

If you are going to run 4 Tempest X's just run them all sealed.

**Aaron Gilbert** · **12-03-08, 04:25 PM**

Quote:

Ricci wrote:

I would not tune that low (12hz) with a single Tempest X or even a single of most 18" for that matter. You'll be sacrificing some output in the bass rich 20-30hz area with movies by doing so because your single driver will be asked for huge excursion levels right in that range. I think 13ft tuned to 16hz with an 8" port is a better idea. This should be good down to 14hz.
...

Well, that's exactly what I'm doing, and I love it. I haven't had excursion problems yet, nor do I ned more output, and it sounds great. To each his/her own.

A vented Tempest-X in 16ft^3, tuned to 12Hz, still has considerably better power handling than a sealed Tempest-X, all the way down to 10Hz. And, it has significantly more output capability than the sealed box from about 9Hz to 30Hz. Would you also recommend against ever using a single sealed Tempest-X ?

**thxgoon** · **12-03-08, 04:45 PM**

Quote:

CZ Eddie wrote:

The 600 watts is the x4 multiplier for a quad set of Tempest-X. I'm not limited to 16cu.ft.

The real world continuous output of the 2500 is about 1600 watts. Model with 400 watts per driver.

**Ricci** · **12-03-08, 05:22 PM**

Exactly. To each their own. I'm glad you are happy with yours. I am just stating my opinion and I still feel the same way that I did earlier. I myself would probably damage a Tempest X in that 16 cu ft alignment. If the OP decides to watch a movie a bit too loud there is a possibility that he could mechanically damage the driver. He will have a lot of power on tap and one loud 20hz note could be bad with that much juice. I'm pretty sure Kevin would back that up.

The 16cu ft box has less power handling around 20hz and below 10hz than the sealed box that I would run. 5cu ft maybe 6. Of course the ported has more output 30hz down to 10hz. I just did an entire series of tests on just that subject. Plus you are comparing a 24" cube to a behemoth sized box. I wasn't recommending sealed unless the OP is running 4 drivers at which point probably 80cu ft of external enclosure volume would seem a bit much.

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