Axiom Home Page Forums General Discussion Home Theater sub in custom box not sounding right :(

Hi all, new user and have a little question, i have a fusion 12" subwoofer in a 44litre sealed box, it sounds good but doesnt go very loud, its powere by a 240w RMS power module, now should this box be ported? and will i get a different sound if the subwoofer faces the other direction? also on my pre amp i have a switch that says 0 or 180, its the frequency of the sin wave, can someone tell me what this does and what it shoud be set to?
Thankyou

Hi Kevin; and welcome!

A 12" in that size box may work just fine

.....or it may not

A couple of questions:

Do you have the White Paper for the driver? Or at least the Thiele Small parameters for the thing? If you have the specs we can plug the numbers into the formulas and find out what kind of box and alignment is best.

The 0-180 question probably has to do with the phase that the driver sees.(Kinda like changing the leads going to the driver) Set it so that the speaker is loudest!!

When you say "not very loud" are you talking about just not enough volume, or is it "bottoming"; Actually "Hitting the Stops"? Having the specs will help with answering that question as well!

Just having the name and model number would help

Factory Specifications
Magnet Structure – 200 Oz
Power Handling – 900 Watts
Voice Coil – 2.5” Black Alloy DVC
Impedance (per coil) – 4 Ohms
Free Space Resonance (Fs) – 28.5Hz
Efficiency (1W/1M) – 94.5dB
Frequency Response – 22Hz ­ 1.2kHz
Mounting Diameter – 11.22” / 285mm
Mounting Depth – 5.82” / 148mm
outside Diameter – 12.56” / 319mm

These are all the specs i could get, will this help?
The speaker seems to be moving a very long way for the volume that it is at, i cant hear or feel the bass very much but the fittings in the room vibrate so it must be doing something. Originally i thought bigger box = better. I made the box 122litres but it sounded dodge and would "bottom out" so i put a divider in reducing the box down to 44litres. Some audio technician that was jabbering [censored] to me said that i should add some sound dampering material, such as poly insulation or something, what effect would this have on it, im thinking the sub would have to work harder so thus creating a bigger box for the sub.

Here's a good place to get started. Unfortunately, it doesn't look like we've got enough info to plug into the equations just yet.

Hi again Kevin;

Well, it's a start; but we're not there yet.

A few good numbers are still missing, I'm afraid. Like Qts, Qes, Xmax, and like that

You're halfway right about what the polyfill does in the box! What happens is, the sound takes a bit longer to find it's way thru the stuff out to the enclosure walls, and then back again, so the sound is fooled into thinking the walls are farther away, ergo, the driver thinks it's in a bigger box

Generally speaking; a bigger sealed box IS a better box(to a point)normaly a bigger box will give a cleaner, dryer sound with less "Boominess"

You may want to check and see if your impedance is set properly. Having a DVC(dual voice coil)driver does complicate things a bit. If the voice coils are connected in series, the amp will see 8 ohms, if in parallel; only 2.

If you're getting low volume, but lots of travel, you may also want to check what cross-over point you have. If you're crossed down around 40hz or below, with a big bass boost dialed in, the driver may not be seeing much other than the real low stuff, and with an SPL of 94.5 db, you should be gettin' lots of noise

I'm gonna sneak off now and do a little Googling for a Fusion 12 with numbers that match what you currently have, and see what we can come up with!

If you should find out any more info, let me know!!
Rich.

Well;.....found the rest of the needed info!

Don't know who told you 44 liters for the sealed box size; but that's what the factory recomends

Here's where my knowledge of subwoofers breaks down.....maybe car subs operate under different rules due to car interior sizes vs average home listening room areas

If you plot the driver, you end up with a .707 Qtc for a nice average sound in a box of around 20 liters; a whole lot smaller than what you have now.

I could see why you were bottoming though: At 240 W you're dangerously close to being at the limit of what the driver excursion/power inputs ratio can handle at 44 liters(no problem at anything less than about 40)

Anyway, the numbers I come up with suggest a sealed box size of closer to 20 to 40 liters as being safe in the home.

The company also lists the driver as being acceptable in ported enclosures as well(49.1 liters with a four in. port 16.8 in. long)

Good luck with your troubleshooting, and be sure to let us know how things work out