subwoofer requirements

guys, i need help. a friend wants me to build him a sealed 12" sub for his 05 dodge regular cab truck. i've built home audio for years but haven't ventured into car audio before. due to room gain in a small cab dickenson's cookbook suggests a low Qts of around .25 in a small box will be a fairly flat response. a cursory look thru the pages of a parts express catalogue tell me there are no subs any where near that. the dayton quattro is in the low to mid .30's and car audio brand names are well in excess of .5. what is a suggested box Q(warm but not boomy) and what driver specifics do you guys look for here?
i have up to 1cu.ft. to work with preferably.
david
 

jol50

Member
2007-11-08 2:14 am
If you need a small box you need a low Q, it is roughly how stiff the cone movement is so smaller box you need a looser cone to still move against the air cushion. Vas also applies to this....if you play with a model program like winISD you can see how the low Q gives more bass in a little box...or the manufacturer should recommend smaller size for their lower Q drivers.
 

jpruden

Member
2007-09-13 4:57 pm
jol50 is right... try to shoot a little low with the Qts as there is a pretty huge peak at the lower frequencies. Any Qts over about .9 will give you a gnarly peak in a car at Fs.

You certainly don't have to go really low with the Qts on the driver... but you probably want the Vas to be relatively low if you plan on your design being a real sub.

From Parts-Express, you can use one of these drivers:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-555

In a 1 cubic foot box for some serious boom... the Qts is about .7.
 
thanks guys, that's great info! i was wondering about the lower Q because while some local builders told me awhile ago about building sealed car boxes in excess of 1.0 for the 'warmth', the ones that i heard were terrible. but now that i am understanding cab gain i can see that they would've had a noticible boomy peak. the peerless sounds like it makes everyone happy- HT, home audio, and car audio but i think it's out of his range.
thanks again guys
david
 

jol50

Member
2007-11-08 2:14 am
There are ones that will work in the .3-.5 area depending on cf and how you want it tuned, just have to look around for them. You kind of have to put them in software to see, or if they show a chart like PE often does. Some are car subs some not. Ones I am running IB are Infinity and think .49 or so but I can tell you one sounded nasty in a 1.25cf box in my trunk. I like more SQ though, thought it sounded boomy to me. Pretty sure a little larger box would have worked a lot better. I have to have good output down to 30 to be happy, screw cabin gain. It only changes the sound of the sub so much IMO, excepting some cars that do more than others. If I get a peak at about 50 or more I don't like it. I ran an audiobahn clone in that box and it was a little better, but they only have a 10" size cone with that huge surround in a 12. Also ran a sony P5 12 in a 1.15cf stuffed and it was better but not right. It hit hard at 50-60 but went soft above and below. Ran a mtx 4500 10 too, it sounded nice IMO though had less output than a 12. It was in recommened mtx box, .9cf I think it was. My IB hit everywhere plus now I have a parametric EQ and now have to rework my high side up to snuff I'm so happy with them. Except, 4 of them weigh a ton so I might try some lighter subs. These have more output than I need.

One thing I have thought about is those passive radiators. Take a single 10 or 12 paired up with one and they have good output in a small package.