[CZ Eddie]

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]

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]

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

 

[Aaron Gilbert]

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. :yay:

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.]

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]

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]

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]

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 ? :scratch:

 

[thxgoon]

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]

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.

 

[Aaron Gilbert]

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.

Ah, there's the difference. I always make my sealed boxes shoot for a Qtc = 0.707, which is what I modeled. I do use smaller boxes when the situation calls for it. If using 5-6 cubic feet sealed then indeed, your power handling becomes much higher than the 13 cubic feet needed for a maximally flat alignment. Man this new Tempest-X sure likes a gargantuan box compared to the original Tempest...:blink:

You're right, with enough power, larger boxes certainly make it easier to damage the drivers. To that I say, use less power. :T You'd think that would be more popular, what with the 'green' movement and all. :cunning: Small is popular these days too, no arguments there, and that definitely ups the power requirements. It just doesn't make sense to me to use tons of power per driver and a giant box, though. Why build big if you aren't going to use one of the primary advantages to doing so?

 

[Ricci]

I'd usually go for that alignment too with a sealed box, but sometimes I'd fudge if the box ends up too big and the driver is ok with it. Like in this case. I'm getting a bit over 8cu ft for a 0.707q:scratchhead: You are getting 13ft? Is that right? If that's the case then one of us has something entered a bit off. It does like a big box but dang...



Eddie,
You a cranker, or a reservist with the volume?

 

[CZ Eddie]

I never listen at anything less than reference volume. Volume is always at -5 or louder. And I like my bass a bit on the heavy side as well. Maybe +5 to +10, depending on the source I'm using. My room is 3500 cu.ft. and opens up to other areas of the house, making the room size effectively much larger.

My current 2x Tempest-X in a 12.5 cu.ft sealed enclosure with 60-70% polyfill is not loud or low enough for me. I need something that plays lower, with authority. But I don't like the loose rumbly sound I get sometimes with any of the ported enclosures I've ever built in the past.

So if two sealed Tempest-X aren't enough, then I worry that four won't be enough either. Btw, my single 18" 19Ov.w 18hz tuned enclosure sounded louder and much lower in comparison.

I played with WinISD for about an hour tonight but I just ended up frustrated because nothing that WinISD comes up with, matches anything in the Tempest-X PDF for enclosure designs. I feel like I'm wasting time because anything I model in WinISD is just going to sound completely different in real life.

 

[thxgoon]

I played with WinISD for about an hour tonight but I just ended up frustrated because nothing that WinISD comes up with, matches anything in the Tempest-X PDF for enclosure designs. I feel like I'm wasting time because anything I model in WinISD is just going to sound completely different in real life.

I'm not sure what you mean by this. Don't forget about eq.

LLT vs sealed is not even a comparison ifyou're looking for high output and deep extension. You should get close to 10db near tuning from the LLT over the sealed design, which is more than adding additional sealed units. If you had bad sounding ported subs in the past it was due to bad design, not ported design. Don't get too frustrated, this is supposed to be fun! You won't be disappointed in LLT.

What exactly are you unsure about?

 

[Mike P.]

I'm getting a bit over 8cu ft for a 0.707q:scratchhead: You are getting 13ft? Is that right? If that's the case then one of us has something entered a bit off. It does like a big box but dang...

I'm also getting 13 cu.ft. for a 0.707q. The file I'm using was created with the "Auto Calculate" feature and is on the downloads page. Compare the file to yours and see if there are any differences.

http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html

 

[CZ Eddie]

If you had bad sounding ported subs in the past it was due to bad design, not ported design.

No, it wasn't. But I know that's what everyone says whenever somebody complains about ported enclosure sounds.

Mike, I get 13 cu.ft. also. See my related thread about this anomoly here:

http://www.avsforum.com/avs-vb/showthread.php?t=1082853&highlight=tempest

 

[Ricci]

Exodus took the Tempest X off of the site.

Can somebody post the factory parameters?

I'm using this.

MMS 165g
CMS 450um/n
BL 11.8
RE 3.6
SD 791cm
LE 0.49
FS 18.47
VAS 399.4L
QES 0.405
QTS 0.422
QMS 2.86
PE 600w
xmax 27mm

 

[CZ Eddie]

Ricci,

The WinISD files are available for download here:

http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html

Or if you want to use one based on a Dumax test of the Tempest-X that Jimstewart posted over on AVS, then I attached that one to this post. I created it myself, based on the figures in that Dumax report. It models similar to the published Tempest-X found in the link above.

 

[SteveCallas]

It's unclear as to whether you will be porting both drivers or just one. When you port one, you gain a clean 6db advantage over the sealed at and around tuning. When you port more the one, that advantage grows.

I would not tune to 12hz. A 15" driver only has so much displacement and you don't want to use much of it chasing single digits. A tuning around 15hz seems more appropriate and will definitely still provide much better low end than its sealed counterpart.

Don't be afraid if the simulation exceeds xmax a bit with full rated power.

No, it wasn't

I bet it was. What was the design?

 

[thxgoon]

No, it wasn't. But I know that's what everyone says whenever somebody complains about ported enclosure sounds.

I used to think exactly the same thing... until I built a pair of good ones.

Edit: Have you read through Steve's LLT Explained thread? Page one has great information about sealed vs ported and the perceived lack of quality of ported boxes.