View Full Version : 8 12's in a bandpass question

08-15-2011, 06:41 PM
I have 8 12's that are very efficient and I was told would work well in a 4th order. However I was told to run them in 0.9per sub @ 42hz and 1.75cu per sub sealed side. Supposedly the useable range would be 26.8-65hz and flat all they through.

I am really only needing to be between 26-50hz. I dont know if there is a trade by being a flat response but I was told thats only for sq systems. All I'm wanting is audible loudness.

Any info?

08-15-2011, 06:55 PM
well, i would ask the guy again, but you could go to a 2:1 ratio, maybe a tad more, which it almost is, and drop to 41-40hz, but i think you are close to peak already.... this is just quick guestimates. did the guy run the numbers, know from experience, or just pass on hear-say? imo, i wouldn't be sure about it being flat all the way through, but that's me.. and a sq system would be more flat from the bottom all the way to the mid-bass , which could be upwards of 120-200hz

08-15-2011, 06:57 PM
so what is the difference between flat sounding and somewhat peaky response? I know I just want boomy loud and low.

08-15-2011, 07:23 PM
Well.. what woofers do you have? That would be a good starting point..
post TSPs

08-15-2011, 07:37 PM
klippel accurate

Fs 28
Qts 0.47
Vas 1.6
Sens 85.6
xmax is 25mm one way linear

box suggestions 1.7 cubes @32hz - 2.2 cubes @27
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08-15-2011, 07:49 PM
Do you have the rest of the specs?.

Like 1.6.. 1.6 what? Liters? Cubic feet? Slimjims?

08-15-2011, 07:49 PM
will try to get asap.

08-15-2011, 07:59 PM

08-15-2011, 08:35 PM
EBP isnt all that great. VAS appears workable.. let me take a look.

08-15-2011, 08:42 PM
Itll be a big toss up for the vehicle you put it in.. but I think the specs you listed will give you a heavy low end but not much top end. I know you arent asking for much, but unless your vehicle gets good upper end gain (unlikely for this setup) youll falloff around 40hz normally.
42hz is a very low tuning. The specs the person gave you work well on paper from 26-50hz, but at 40hz you still are at full output/0db down reference point. At 26hz you hit your F3/3db down point. That is not quite an octave but close enough to it.. you car will add a ton of low end and overpower the messily 3db loss of the enclosure.
Youll probably see a good 6-10db gain slop from 40 down to 30hz..

Edit - I guess the point is. If youre OK with not much top end at all really, and songs like jeezy - thug motivation or air forces is as high as you want to play, and you like a nice heavy low end, then it should work well for you.

Also, guessing this is a wall you may want to go a slightly larger front chamber still. Port forward like that, depending on placement, will normally give you a smooth low end gain and not the two-point gain slops/humps like having sub and port orientation in play. You still have fine possibility for low end. Just make sure you set your SSF accordingly as the power handling wont be too great.

08-15-2011, 08:48 PM
yeah I was told the ebp isn't that bad though. An ebp of 60 isnt bad.

edit, i was planning a wall in a bronco. I was wanting some top end but nothing above 50hz. And as for the power handling, why would it not be so great? I have nearly 10k on tap to use. The 25hz region really doesn't bother me as I probably wont play much of anything with that. So 30-50hz would be a good point i'd like to stay around and be as audibly loud as possible. Playing to the high 20 region would be cool but I doubt I would hardly do it.

I'm looking for opinions though so what would you suggest I do?

08-17-2011, 03:40 AM
If you have the space, a 6th order would be your best option - though not your easiest.
A 4th order doesnt have the best power handling. A 6th order will be considerably better. But theres more detail to it, as in what range youll actually play, etc for if youll actually hit the displacement limits. This can all be predicted/modeled to check and make sure.

08-17-2011, 03:58 AM
Idk why people do 2:1 when they want a flat response... :confused:

08-17-2011, 04:02 AM
Kang, are you talking front:rear? Depending on the sub, it can work out well in-car for a flat response. Otherway around, it may as well.. but normally thats in the area of modeled flat response.