Hi Guys

[Brian Steeves]

Just wanted to say hi to you all. This is my first time here. Looks like a great site Lex!




She said,"you're gonna put that thing WHERE!"

[Pat]

Welcome aboard Brian.

Did you decide on a design for your Tempest yet?




Pat's Page

[Bing Fung]

Welcome Brian!




Bing

[Brian Steeves]

Pat,

I think so. I'm pretty sure I'm gonna go with a 240l 17hz tune. The only thing I am concerned about it Xmax. It seems that some others are concerned about this as well. The LspCAD program shows huge amounts of excursion between 25-40hz.




She said,"you're gonna put that thing WHERE!"

[Andrew Pratt]

Welcome to the guide. I'm not sure if you've seen my site or not but I built a 250 liter sonosub using the PE 15" driver which is a clone of the tempest. There's an SPL plot on the site that might interest you given the similarity b/t our subs. (link to my site is below)

[JonMarsh]

Brian and others;

Whenever you use an extremely low tuning in order to optimize the output in the 20Hz and below region, (say an Fb of 15-17 Hz)the problem you have is that 1 octave above that frequency the system is acting for all intents and purposes like a sealed box. That means there's little to no port contribution, and in the range from 32 - 45 Hz, the driver has to do all the work. Without the port involved, there's simply no replacement for displacement- a single 12" driver is going to have to work very hard if you're trying to feed it several hundred watts and get 110 dB or so out. Not really practicle. That's why in my mains, the box Fb is 26 Hz, and useful port output doesn't go away until above 50 Hz. This translates into 118 dB per cabinet from 28 Hz to 200 Hz in the bass system, which is an Audax 13" pro and Audax 15.5" pro (it's a bit bigger than a std. 15") driver. When the Tempest's are available (some day, some day!!), then the dual subs with 2 Tempests per cabinet will get built; they'll be crossed over about 35 - 40 Hz, so that there is adequate overlap. Yeah, this is going to look a bit too much like a Greatful Dead PA system when it's done, but when you're not married, and can build odd shaped cabinets (plannig on two corner cabinets with beveled front panels), you have a few more options.

Regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[ThomasW]

Brian

Also see the large signal vs small signal answer I place after your "Thomas you've got mail" post on HTF




theAudioWorx
Klone-Audio

[KennyG]

Hi Brian, nice to have you on board, for such a small site we alot of DIYers, and beginning DIYers (that's me!) KennyG

[Brian Steeves]

John,
Not sure if you realize it or not but I have a Tempest driver for this project, not a Shiva.
What's wrong with the idea that in the 40-80hz range the sub acting like a sealed enclosure? I mean wouldn't that be a good thing? And if the amp power is available, and I think it is (850 watts into 4 ohms) this would be the best of both worlds. Good low end extension and tight midbass.
Now this is my first attempt at a ported sub, I have made several sealed ones over the years. I have always had good results with them.
Dan Wiggins is the one that suggested the volume and tune I mentioned.
What would you recommend if you were going to make one and why?




She said,"you're gonna put that thing WHERE!"

[Brian Steeves]

Patrick,

Why 3 4" ports? Dan says 1-4" flared or 1-6" non flared flared port is enough.

I am getting so confused with this port thing!




She said,"you're gonna put that thing WHERE!"

[ThomasW]

Brian,

Jon is talking about 3 different systems

1)

Whenever you use an extremely low tuning in order to optimize the output in the 20Hz and below region, (say an Fb of 15-17 Hz)the problem you have is that 1 octave above that frequency the system is acting for all intents and purposes like a sealed box. That means there's little to no port contribution, and in the range from 32 - 45 Hz, the driver has to do all the work. Without the port involved, there's simply no replacement for displacement- a single 12" driver is going to have to work very hard if you're trying to feed it several hundred watts and get 110 dB or so out. Not really practical.

Here he's discussing generic sub design, and what happens with low FB tunings and the effect they have on driver workload

2)

That's why in my mains, the box Fb is 26 Hz, and useful port output doesn't go away until above 50 Hz. This translates into 118 dB per cabinet from 28 Hz to 200 Hz in the bass system, which is an Audax 13" pro and Audax 15.5" pro (it's a bit bigger than a std. 15") driver.

Here he talking about the bass bins for his Wilson Audio X1-SLAMM clones

3)

When the Tempest's are available (some day, some day!!), then the dual subs with 2 Tempests per cabinet will get built; they'll be crossed over about 35 - 40 Hz, so that there is adequate overlap. Yeah, this is going to look a bit too much like a Greatful Dead PA system when it's done, but when you're not married, and can build odd shaped cabinets (plannig on two corner cabinets with beveled front panels), you have a few more options.

Here he's talking about a corner loaded ported box using 2 Tempests. These will be his subs.

The references to "The Grateful Dead" are a result of when Jon custom designed and built equipment for several members of that band.

Sorry for any confusion.




theAudioWorx
Klone-Audio

[Brian Steeves]

Thomas,

I figured he was. But like he said,"Whenever you use an extremely low tuning in order to optimize the output in the 20Hz and below region, (say an Fb of 15-17 Hz)the problem you have is that 1 octave above that frequency the system is acting for all intents and purposes like a sealed box. That means there's little to no port contribution, and in the range from 32 - 45 Hz, the driver has to do all the work. Without the port involved, there's simply no replacement for displacement- a single 12" driver is going to have to work very hard if you're trying to feed it several hundred watts and get 110 dB or so out. Not really practical."

Does this apply to a "Tempest" based sub with the design I mentioned?

My question,"What's wrong with the idea that in the 40-80hz range the sub acting like a sealed enclosure? I mean wouldn't that be a good thing? And if the amp power is available, and I think it is (850 watts into 4 ohms) this would be the best of both worlds. Good low end extension and tight midbass."

Like I said before this will be my first vented sub so all the experience you advanced guys have to offer is very appreciated! I an trying to learn the advantages and disadvantages.

"That's why in my mains, the box Fb is 26 Hz, and useful port output doesn't go away until above 50 Hz. This translates into 118 dB per cabinet from 28 Hz to 200 Hz in the bass system"

Ok since I will be crossing my Mirage OM10 mains to this sub at the standard 80THX crossover(no other choice at this point) why would the above statement apply to me?

[Andrew Pratt]

Brian I'll let the thomas and jon handle the volume questions but I will say that a single 4" vent flared or not is not nearly enough for a tempest driver unless you are only planning on providing it 2-300 watts...even thats a stretch. If you limit the porting it will compress the sub forcing it to act more like a sealed sub so SPL's are limited and you may get nasty chuffing sounds as huge amounts of air try to get through that tiny hole

[John Holmes]

Hello Brian,
I am not a technical guy so I have nothing to add to this discussion but good luck

I haven't had the chance to say welcome to the forum so, Welcome!




"I came here, to chew bubble gum and kickass. And I'm all out of bubble gum!!!" My DVD's

[JonMarsh]

Hi Brian,

If you're doing a tempest system, using a single 4" port would be selling the 15" driver WAY short on the port output- TEMPEST and SHIVA drivers have long excursion, can really work a port hard, and the port velocity and losses will be too high. For a 15" driver, I usually use a 6-1/2" diameter port minium, which is a lot more area than a 4". Otherwise, if you want to tune real low, a PR may be an option to consider. I'm not personally big on PR's, that's just one of my prejudices.
If you have a box simulation program, you can look at the driver excusion and power handling, which is a function of thermal effects but especially the excursion limitations of the drive. Everyone seems to want 115 dB plus, but when you tune very low, you have to recognize the limitation in power handling that results if port output goes away for all purposes above 25 Hz. What will happen is a "saddle" in the power handling curve, with a dip in the 25-40 Hz region, and higher cone excursion. Not saying that's a bad tradeoff, but be aware of the ramifications. When goin to sealed or IB type approaches, you can sometimes expect to realistically use 2X to 4X the drivers. That's why ThomasW's "12 Shiva's Dancing" isn't such a totally over the top system- it makes a lot of sense, if you want uniform output down to 15 Hz.

Regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Brian Steeves]

What would you guys recommend if you were going to make one and why? i.e. volume, tuning, port size, etc...?




She said,"you're gonna put that thing WHERE!"

[ThomasW]

Brian

If you look at the plots in the link below, you'll see the "notch" or "saddle", Jon is referring to in #2&4

http://users.t-three.com/ttriff/page29.html

theAudioWorx
Klone-Audio

[Lexman]

Thanks Brian! Hope you enjoy our little hideout.

Sorry for being late here, but just saw it. It's been a rocky road with PCs at home and very busy at work.

Lex