Small box for Fi Q 12"... can I go ported?

[Ozzuneoj 0]

I've had a Fi Q 12" for several years now... I think I got it in 2008, maybe 2009, but it was before they changed some of the options available. At the time there weren't many options and I went with the most basic setup available.

 

Basically, I've had to reduce my trunk space consumption by moving my audio gear (wife and I had a baby in September!). Last summer I managed to move my Kicker ZX200.2 amp which is powering my front speakers (Eclipse SC6500 6.5" components with passive crossovers) and attach it to an accessible metal panel in my trunk, and I actually completely removed my Fi Q 12" in a 1.25cuft (gross, not net) box, and my Kicker ZX750.1 amp that Kicker rated for around 890 watts RMS (according to the paper they sent with it). It has certainly been interesting testing out the capabilities of my components running off of around 70 watts each... they put out a lot more bass than I gave them credit for originally. They sound fantastic crossed at 40Hz, or just playing open with no crossover... no distortion at the volumes I listen to.

 

... but after having a sub in my vehicle since 2006, and being exposed to large, loud systems in cars since the early '90s, I certainly notice the lack of "kick" in all of the kick drums, and the lack of rib cage rattling in deep bass tones.

 

I miss it, and I want it back, but I want to do it with minimal trunk space used.

 

Basically, I'll be building a box that makes better use of the available space in my trunk. There is a decently sized nook in the side of the trunk, behind the left wheel well, and I'd like a box that utilizes that space, to accomodate the depth of the woofer. It will also stretch out along the wheel well toward the back of the rear seats. This is a basic sketch of what I'm going for.

 

 

The dotted line is the trunk interior, the arrow points to where I could put the port if I go ported.

 

Basically, how small can I go with a ported enclosure for this sub?  When I put the numbers into WinISD, sealed compared to ported shows what looks like a decent response curve and much deeper low end (F3 around 30Hz) for the Fi Q 12 in boxes as small as 1cuft ported, tuned to 30hz. Compare this to an F3 of around 70hz for the sealed box at 1.09cuft (net). Is WinISD just not doing things properly, or can I actually get decent response out of a box this size ported? I don't need competition level volume here, I just figured if I'm going to build a new box, I might as well see if ported would be a good option.

 

I mostly listen rock and metal, but with some newer bass-heavy stuff thrown in, like Glitch Mob, Daft Punk, Owl City and some others.

[lithium 358]

probably best to keep it sealed. low end output wont be as strong as a ported enclosure but thats the trade off (a bit of eq to flatten any peaks would be best of course). unless you can find ~2 cu ft net somewhere. need that spare  tire? 

 

 

alternatively you could consider either trading it for a 10" or reconing to a 10"

 

another idea, if you need to save space is to consider an infinite baffle set up.  

[Ozzuneoj 0]

Thank you very much for the input. What exactly would be the downside to just going ported in the smaller box? Again, when calculated in WinISD, the response curve seems to be more consistent even in a tiny ported box compared to sealed.

 

Other than the recommendations from Fi (which I assume prioritize performance over box size), why do you recommend going sealed unless I can manage 2 cu ft net?

 

I don't have a lot of hands on experience with all of this, but I've done a lot of reading and research related to car audio and home audio, which is why I have WinISD. The software tells me that a smallish ported box can manage an F3 of 30Hz, with a much flatter response down to there compared to a sealed design, and the two tend to meet around the 20Hz mark, so I wouldn't be losing anything within the audible range (sealed drops off more gradually under 20Hz). But then, there has to be more to it than that, or people would be making tons of tiny ported boxes for these things. I can't be the only person that is willing to spend $250 on a hand made subwoofer but doesn't want 50% of their trunk taken up to use it.

 

Are there any really technical downsides as far as the mechanics of the speaker that make it a bad idea to use a small ported box?

 

I trust the opinions of the more experienced builders, I just like to know specifics so that I don't have to think about "what if I had gone ported..." once I get done building a sealed box and plan on using it for several years.

probably best to keep it sealed. low end output wont be as strong as a ported enclosure but thats the trade off (a bit of eq to flatten any peaks would be best of course). unless you can find ~2 cu ft net somewhere. need that spare  tire? 

 

 

alternatively you could consider either trading it for a 10" or reconing to a 10"

 

another idea, if you need to save space is to consider an infinite baffle set up.  

Edited March 29, 2014 by Ozzuneoj

[Ozzuneoj 0]

I did just have a bit of a revelation here. I nearly forgot that my Fi Q is from 2008 or so, and the specs have apparently changed since then. I did find an old picture of the 2007 model's Thiele-Small parameters. After plugging these into WinISD, its pretty clear that the newer models have improved the low end response a bit in most situations, compared to the 2007 model that I have. Also, the sealed vs. ported response curve seems much closer with the old specs put in. The difference isn't nearly as significant, but ported still shows a much lower F3 (31Hz vs 44Hz in a 1.2cuft box, tuned to 30Hz).

 

Is there any reason to believe that this information reported by WinISD wouldn't be accurate?

 

[lithium 358]

I did just have a bit of a revelation here. I nearly forgot that my Fi Q is from 2008 or so, and the specs have apparently changed since then. I did find an old picture of the 2007 model's Thiele-Small parameters. After plugging these into WinISD, its pretty clear that the newer models have improved the low end response a bit in most situations, compared to the 2007 model that I have. Also, the sealed vs. ported response curve seems much closer with the old specs put in. The difference isn't nearly as significant, but ported still shows a much lower F3 (31Hz vs 44Hz in a 1.2cuft box, tuned to 30Hz).

 

Is there any reason to believe that this information reported by WinISD wouldn't be accurate?

 

when you're modeling sealed vs ported remember that the volume is NET not gross. so that ported box will actually be much larger when you include port displacement. 

 

here are a few things to compare, 

1. sealed 12"

2. small ported 12" 

3. recommended ported for the 12" (for comparison)

4. 10" ported (because you should have gotten a 10" if you need the low end but dont actualy have room)

 

take a look at the spl graph with the subs seeing the same power.  

[lithium 358]

you could alway try ported on with the small enclosure and if it sounds bad just seal the port up. 

 

consider an external port, perhaps

[Ozzuneoj 0]

 

I did just have a bit of a revelation here. I nearly forgot that my Fi Q is from 2008 or so, and the specs have apparently changed since then. I did find an old picture of the 2007 model's Thiele-Small parameters. After plugging these into WinISD, its pretty clear that the newer models have improved the low end response a bit in most situations, compared to the 2007 model that I have. Also, the sealed vs. ported response curve seems much closer with the old specs put in. The difference isn't nearly as significant, but ported still shows a much lower F3 (31Hz vs 44Hz in a 1.2cuft box, tuned to 30Hz).

 

Is there any reason to believe that this information reported by WinISD wouldn't be accurate?

 

when you're modeling sealed vs ported remember that the volume is NET not gross. so that ported box will actually be much larger when you include port displacement. 

 

here are a few things to compare, 

1. sealed 12"

2. small ported 12" 

3. recommended ported for the 12" (for comparison)

4. 10" ported (because you should have gotten a 10" if you need the low end but dont actualy have room)

 

take a look at the spl graph with the subs seeing the same power.  

 

 

Yeah, I've compared them, and it seems like ported will go consistently lower, even with smallish boxes.

 

I've done some more measuring and poking around and it looks like I should be able to get a bit more space than I thought. If I do it just right, I should be able to get around 1.75 cuft net (counting for port displacement and .16cuft of displacement for the woofer).  So, that gives me considerably more low end. In WinISD shows an F3 of around 26Hz, which is awesome.

 

Also, as I said I've had this sub for almost 7 years... to say I should have gotten a 10 would involve predicting meeting someone, getting married and having a child. The 12 worked great before, and it still works great. I'm just trying to adapt it to my new space requirements (which are for more reasonable).

 

I will probably just build the ported box to see how it sounds and just convert it if it doesn't work out.

 

Thanks for the input guys!

[lithium 358]

gl with the build