Home theater box design

[alexj01_83 6]

I have Dayton Audio spa 500 plate amp for power, and the sub I will be using is a sa-12 I have lying around. This will be used in my home theater. My questions are, what is the typical tunning freq with home audio. (I will also listen to some music occasionally) I have also noticed that in home theater that the boxes are larger than typically used in a car audio setup. This will be my first ht project and I was wondering if some one could point me in the right direction. ( box designing literature/software) Thanks in advance.

[///M5 2,833]

If it's for movies the box is completely different than for music. Movies you should port somewhere in the low teens. Have to model the driver and watch output, extension, excursion, port velocity, and use of power to really make recommendations.

I'd also HIGHLY recommend an SSF for Home Theater use otherwise the ultra low stuff can easily send you beyond xmax.

[95Honda 486]

Design your box with the goal of low end extension and tune around 20Hz if you can. This will make for a bigger box, but you will have a flatter response with less ripple and better low end extension.

You have enough power that the overall alignment efficiency won't be a huge deal.

I haven't looked at the SA12 T/S parameters, but most "car audio" subs will work fine as long as the Fs isn't absurdly high and they have a usable Vas (usable that the box will be large enough to accomodate an appropriate size vent and not have a huge bump in response)...

[95Honda 486]

Yes SSF like M5 said.

I ruined a pair of Tumults (triple joint failure) in boxes tuned in the high teens for the simple reason I didn't have a SSF. And I was watching "The Polar Express" of all things... And these were drivers with almost 3" of linear stroke...

[alexj01_83 6]

"Have to model the driver and watch output, extension, excursion, port velocity, and use of power to really make recommendations." How would I go about doing that.

"SSF" Please explain.

[95Honda 486]

SSF = Sub Sonic Filter.

It is a highpass filter. In alignments that do not provide enough loading to the driver below resonance, this filter reduces output to prevent mechanical failures.

[///M5 2,833]

Otherwise ported and HT = driver death.

[alexj01_83 6]

SSF = Sub Sonic Filter.

It is a highpass filter. In alignments that do not provide enough loading to the driver below resonance, this filter reduces output to prevent mechanical failures.

OK thanks.. How would I model that into my plate amp? I will check if my receiver has the capability to perform this function.

[alexj01_83 6]

Otherwise ported and HT = driver death.

Ha ha

[///M5 2,833]

Neither your plate amp or receiver have that option. You need to buy something like a miniDSP or if you want something pre-configured a Reckhorn B-2.

[alexj01_83 6]

box designing literature/software ????

[///M5 2,833]

WinISD is what I would use, but don't consider it design software but modeling software. IE, don't let it pick the port, box size, power, eq and such. That is a job for the user.

[alexj01_83 6]

what do i need to look for in the graph, what am I trying to achieve

[95Honda 486]

Wherever you tune your are going to see a drop in response below resonance. It will be somewhere around 24/db per octave (so if response starts to drop at 20Hz @ 90db it will be be 76db by 10Hz) and you will need to mirror the inverse of this with your SSF. So if it were textbook you could just apply a 24/db per octave highpass filter that starts rooling off right below your resonance point.

Or, just pick a highpass filter like a Harris F-Mod that is roughly the same (or slightly less than) cutoff of your enclosure tuning.

Or tune real low liek we said (teens) and don't give it a ton of power and be happy with it.

Or go sealed and never worry about it...

[///M5 2,833]

what do i need to look for in the graph, what am I trying to achieve

As low as extension as possible while maintaining output and not sending your driver into over excursion. At some point tuning lower will no longer buy you anything which you'll see as you start to play around. Best way is to make a few different designs and put them on the screen all at once. I sort of pick both extremes and then use the third to tinker in between and see what compromises I'll choose versus others.

[edouble101 314]

I prefer sealed enclosures for my home. Infrasonic freqs are of no concern then. I wouldnt use an SA-12 for home theatre either but thats just my opinion.

[alexj01_83 6]

I wouldnt use an SA-12 for home theatre either but thats just my opinion.

Why so?

[Shogen 325]

I prefer sealed enclosures for my home. Infrasonic freqs are of no concern then. I wouldnt use an SA-12 for home theatre either but thats just my opinion.

I wouldnt use an SA-12 for home theatre either but thats just my opinion.

Why so?

Higher FS plus they excel more within a ported alignment and he prefers sealed....

Look into Dayton Audio woofers...

Or any of these..... http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=835

I didn't read fully so I don't know if you specifically need a 12 or already own an SA12 .... But check out the link...

Usually bigger cone has a slight advantage in the lower-end department (by design limitations) ...

[edouble101 314]

I wouldnt use an SA-12 for home theatre either but thats just my opinion.

Why so?

Shogen summed it up. Dayton Audio Titanic series would be an excellent option.

[///M5 2,833]

I don't understand the sealed part, in particular for HT.

If box size is a concern, then IB would be the choice IMO.

[alexj01_83 6]

I don't understand the sealed part, in particular for HT.

If box size is a concern, then IB would be the choice IMO.

Me nethier this is what I got out of winisd. All ported boxes are 4 ft^3 Light blue tuned @ 12hz, Green tuned @ 18hz, Red tuned @ 26hz, and for giggles Dark blue is sealed @ 2 ft^3. Me personaly I liked the line @ 18 hz. The sealed box started droping off at 44hz. I noticed that the larger the ported box the more it peaked at the tuning freq (to a certain point). Also do I need alot of port area tuned low, it seemed the more port area I had the longer the port needed to be, but with a smaller diam port it didnt need to be so long But I had a small amount of port area. M5 am i on the right track am i missing somthing??

[///M5 2,833]

Close, but I wouldn't pick the 18Hz. Do realize that 3dB is barely audible and that movies have plenty of notes all the way down to 10Hz. You need to also start playing with box size, power, port velocity, and of course eq. Much of the roll off or anomalies can be steered with eq. Seeing how "nice" you can make it without exceeding the woofers throw is key.

Definitely crank UP the enclosure size. There is a reason that people build large low tuned enclosures for movies.

[///M5 2,833]

Oh, and don't worry about tuning below Fs. With some processing it really is NOT a big deal.

[alexj01_83 6]

When does the box get " TO BIG"? Is there a program for port velocity? With "power" do you mean the gain knob?

[///M5 2,833]

It gets too big when the power you have and your settings kill the woofer. You can view port velocity in WinISD. And by power I mean your amplifier. Input the signal you have into WinISD, it will compute excursion, port velocity etc... based on it. Don't forget the EQ tab either. It does a lot of stuff and you should look at it all before making a decision.

You've just found why most people fail at modeling programs. They don't ask the questions or try like you are. Keep it up! Your doing better than 99.9% of car audio forum goers!