Help with building box for 1st time

[Nick7]

Hi,

having a new car, would like to build a sub box for it (a bit on budget).

I'm not looking to make something to wake neighbors, but to have nice, low bass.

Speaker I have for this is quite old, but in good shape - Kenwood KFC-WS302.

It took some time to find info, and this is what I got:

KFC-WS302

12" Small Enclosure Woofer

GENERAL FEATURES

- Butyl Rubber Surround

- Concave Dust Cap

- Designed for Use in Small Enclosures

- Free-Air Resonance: 21Hz

- Frequency Response: 18Hz - 3kHz

- Gold-Plated, 2-Way SB Speaker Terminals

- Impedance: 4 ohms

- Magnet Protection Cover

- Magnet Weight: 64.1 oz

- Power Handling: 750 Watts

- Sensitivity: 93dB

- Speaker Displacement (cu ft): 0.147

- Vented Voice Coil: 2-Layer

AUDIO SPECIFICATIONS

- Frequency Response: 18Hz - 3kHz

SPEAKER SPECIFICATIONS

- Diameter: 12"

- Magnet Weight: 64 oz

- Mounting Depth: 5-5/8"

- Power Handling: 750 Watts

- RMS Power Handling: 250 Watts

- Sensitivity (1w/1m): 93dB

- Speaker Displacement (cu. ft.): 0.147

Recommended Sealed Box Vol: .88 cubic feet (vented not recommended)

For Amplifier, also an old Alpine 3544.

Now, what interests me most - in this info it says recommended box sealed box size is .88 cubic feet (aka 24.9liter).

I could easily use more volume for box (around 50liter = 1.66 cubic feet) - however, what i wonder what would happen with sound?

Will I get a bit better low-end bass, and a bit 'softer'?

I'm looking for a 'soft' deep bass with hopefully good SQ (don't care about SPL).

Any help is welcome //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

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[Trixter 10+ year member]

you can make it larger...i don't think i would almost double it though.....88 i'd do a no more than 1.25. you will get better low end response, but you will increase the chance of the driver bottoming out more easily...depending on the power your giving it. if you amp does under the rms of the sub, then you can get away with making it larger...the less power the bigger the box.

even at rms power, i'd probably do something like 1.0cu' and some polyfil

BTW: welcome to the board. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Nick7]

Tnx for info&welcome //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I'll prolly go with ~1.25 and fill with poly.

Btw, Alpine 3544 has 400W in bridged mode at 4ohm. I'll just prolly stick lower amp fuse (like 30amp), so in case something blows, it's fuse 1st //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Trixter 10+ year member]

umm...that's not really the sure way to do it. that fuse protects the amp from being over loaded for the electrical source. i guess you could put like a 100w (or whatever) in-line fuse on your + going to the sub....never heard of it before but it would work.

just keep you gains down, bass boost off, and set your eq or x-over (if you have one) so they don't over power.

you can build it large and if you find that the sub looks like it wants to jump out of the box, just screw some 2x4's inside it to take up space.

 

[BrianChia 10+ year member]

Yeah you probably won't blow the sub with that amp, but you may bottom it out at low frequencies if your enclosure is too big. There is no need to use a lower current fuse. When the sub starts to bottom out you will be able to tell and there won't be any danger to the sub if you don't turn it up past that point. Just set the gain properly and/or use the subsonic filter on your amp to limit overexcursion.

If you want good sound quality then a Qtc of 0.7 should work fine and the car's interior will boost the low end and give you a more flat response. There's no reason to make it bigger than it has to be. If you make the box bigger it will roll off the lower frequencies a little slower and shallower, lowering the F3. But as stated by Trixter you will reduce your power handling and may lose some tightness in the response.