DIY Subwoofer Help (Amplifier & Crossover)

[annunaki]

Point well taken Chris. That is a really low F3. What is the Q alignment for the driver in that size enclosure? I typically do not like many drivers I heard much above .83 or so as you get blooming in the upper bass frequency range. The Q on the W6v2 would be .75 I believe in the 1.5 cu.ft. enclosure. Depending upon placement in the room, the F3 on the W6v2 could be negated some. That is only if one knows the rooms characteristics and how much gain one would receive from 40hz and down.

The room in question is 4000 cu.ft. so it is not entirely large but is of good size.

I do like the option on the Infinity of having the F3 that low.

 

[cbraver]

I need to make sure my box isn't cut bigger than 11 1/4" ... if it is, I'll have to use JL Audio. Again, I won't know that until I get home Monday or Tuesday. If it isn't, I'll use the Kappa. If it is bigger, I'll use the JL 13". Unless there is some sort of bracket I could use without being redneck.

How about in terms of output? The W6 would be the loudest and the W3 and Kappa would be comparable?

 

[annunaki]

Overall output is tough to gauge. I would give a slight edge to the W6v2 as it has the most excursion capability there. The W3v3 and the Infinity will be similar for output. They have similar excursion and surface area.

If you bump up to the 13W3v3 the Q alignment will change a bit. The 13" tends to use a bit bigger enclosure. It will have the most output but may be boomier than the others. I will have to model it to see where it is at in 1.5 cu.ft.

 

[cbraver]

If the hole is 12" and I want to use the Kappa (11 1/4"), is there some sort of bracket I could use that wouldn't screw up the sound and solid-nature of the box?

Now I just need to wait until next week to measure the exact cabinet volume and hole size. Based off of the valueable information you guys have given me, I'll be able to finalize a decision. I'll for sure post the exact box volume as soon as I have it (from my Blackberry, haha, since back home I don't even have a computer hooked up...this site actually looks pretty good on a Blackberry though).

I'm sure I'll have to make some compromises based on the box. (After this project is complete, I might model a box based off whatever driver I choose and then build it out of Ipe wood. Very heavy, higher than 1 specific gravity, dense wood.. I bet it would be awesome to use for a subwoofer box. Pain in the *** to cut, but, it'd be worth it. )

 

[annunaki]

If you are going to build an enclosure, it opens up a bunch more possibilities.

As for the opening, you can simply make a 15" ring out of mdf and laminate it to the enclosure over the existing hole. You can paint it to match, and cut the hole of proper size.

 

[cbraver]

If you are going to build an enclosure, it opens up a bunch more possibilities.

Yeah, I'll use this one for this summer. Then, when time permits, build another subwoofer and start the design work from scratch. I have a feeling this could get addicting. I plan on downloading WinIsd at some point too. Epi wood would be really cool, but it would be cool to play around with a composite constructed box. Like a Kelvar and honeycomb sandwich construction... which would have really good vibration dampening properties, but I'm not sure if that would make it sound different/worse/better/horrible.

As for the opening, you can simply make a 15" ring out of mdf and laminate it to the enclosure over the existing hole. You can paint it to match, and cut the hole of proper size.

Good idea. I kinda wanted to keep the wood finish, but, worst comes to worst that's what I'll do. I could always just paint the face or laminate some plain-weave carbon fiber around it ... then leave the rest of the panels wood finish.

 

[WmAx]

I should point out that I realized that the Kappa Perfect VQ in High Q mode works best in very small sealed enclosures, about 1.5 cubic feet is just about perfect for cbraver's application. If you use a substantially larger sealed volume with the High Q mode, the excursion limits are exceeded for full input power rating, thus effectively lowering power handling. Natural response in a 1.5 cubic foot enclosure is about -3 in the 28-29 Hz range. However, this is with a peak, as the qtc is about 1.25. Application of a single parametric EQ band of Center Frequency=51Hz, Q=0.7,Gain=-3.0, will provide a flat response with removal of said peak. This will end up with -3dB at about 33Hz and -6dB at 28Hz and -10dB at 22Hz. Excursion limits are never exceeded in a 1.5 cubic foot enclosure with full 400 watts input at any frequency.

If you ever wanted to make another enclosure in the future, for lowest distortion/highest output/lowest extension - of course a larger enclosure(around 4-5 cubic feet would be optimal) using a large cross sectional dimension port would be required - and the driver would be used in Mid Q mode.

-Chris

 

[WmAx]

I typically do not like many drivers I heard much above .83 or so as you get blooming in the upper bass frequency range.

Of course, all it takes is a single parametric EQ band to fix any bass peaks causing said 'blooming' sound.

-Chris

 

[annunaki]

Understood Chris, great point, but having the natural response smoother with a lower Q will typically lower the F3 as well. Obviously I am sure you are already aware of that.