I need help with subwoofer deisign: HUGE inexpensive subwoofer

[hottyson]

I originaly was going to build a JBL 2242H subwoofer until I found out how much the driver cost! So now I want to build an inexpensive subwoofer/shelf to hold my three full range front speakers (3-way 15/8/horn) behind a screen for home theater. It will be about 3 feet high, 9 feet wide and 16 inches deep. I have a THX Kenwood amp to bridge to over 300 watts and I only want to put an eight ohm load on it. The Kenwood receiver THX processing crossover is at 80 hz.

I have more than enough space for a huge sub. About 30 ft3. I don't want a ported design. I was thinking a sealed enclosure might be simple to build and sound good. A dipole design would be cool too but it will be placed against a wall so I don't know if that is possible. I want it to play deep to at least somewhere in the upper 20 hz at - 3db.

What do you guys suggest I build? [SIZE=3]

Thanks for your help.

[RobWells]

Budget ?

Rob

[hottyson]

Originally posted by RobWells
Budget ?

I would prefer to spend around $100 for driver/s. I can spend up to $300 for drivers if there is a killer setup for the money.

For the wood I will mostly be recycling wood and buying whatever sheets of MDF or Plywood that the project calls for.

[Mudge]

Your enclosure volume works out to about 1000 litres (if you include the amount of bracing needed). At that sort of size you could throw in almost any driver of a reasonable size (15" or high excursion 12") and expect to get decent bass out of it, possibly with a bit of EQ. A naturally low F3 is a bit more difficult though.

[tool49]

OUCH that box is HHHUUUUGGGEEE. You will have a rather hard time finding drivers that will make that box play loud and deep within your budget. I would rather go with a smaller box (around 11 cubic feet) and throw in two NHT1259 from Madisound. You could also try some drivers from Parts-Express such as the Infinite Baffle series of subwoofer that would work in your 35 cubic feet box as if they were in an infinite baffle setup.

Hope this helps!
Sébastien

[xplod1236]

off topic--what is F3?

[Mudge]

The frequency where the efficiency (for want of a better term) is -3dB below the passband.

[TNT]

maybe something likethis ??

http://www.hififorum.nu/forum/topic.asp?TOPIC_ID=28336

Translation on request ;-)

He seems very happy with the result.

/

PS He burnt them in by connecting all drivers in series and then into the wall socket (220V/50hz) 12x6 ohm = 72ohm, P=U^2/R, 230*230/72= 730Watt

The driver is MGR:

http://www.ljudia.se/cgi-bin/se/onli...25%20&cart_id=

[johninCR]

You've got enough room for dipole. Use lots of cheap drivers with small magnets. I've used some cheap nippon 12"ers to good effect. Bring some cardboard and a knife to audition them, to find the ones that get the best bass on OB in the $5-$15 range. You want to listen to the ones with the smaller magnets which indicates higher Qts.

If you don't want to go dipole, then lot's of the cheap one's iso loaded in a push/pull sealed box although you probably only want to use part of the shelf as the box.

Or 2 clamshelled pairs in a 6th order bandpass, or 4 clamshelled pairs in 2 6th order bandpass. You'd lose some SQ, but you can have real in your face HT effects.

Those are 3 ways to get real bang for $100 in drivers. Most of the guys here don't believe in the cheapies, but 1 you can listen before buying and they can be 1/10th the price but 1/2 the quality and when you put them working together, you can get more and better sound.

[Dave Jones]

Originally posted by tool49
OUCH that box is HHHUUUUGGGEEE. You will have a rather hard time finding drivers that will make that box play loud and deep within your budget. I would rather go with a smaller box (around 11 cubic feet) and throw in two NHT1259 from Madisound. You could also try some drivers from Parts-Express such as the Infinite Baffle series of subwoofer that would work in your 35 cubic feet box as if they were in an infinite baffle setup.

Hope this helps!
Sébastien

This one has a Qts of .65 in a 1000 L box:

http://www.partsexpress.com/pe/showd...number=295-450

... and it costs 85 bucks. Nominal F3 would be about 30Hz. That's some way deep bass. Someone who knows something about this stuff would have to say whether that would be too boomy in the particular room the setup is going into.