Mini Subwoofer

I'm wanting to build a mini portable sound system for work, home, or whereever. I want it to have good sound for the size, and most small speaker lack in bass. I'll be using a 4 channel BTL Car Radio IC to drive the front speakers and sub.

I found this small sub at Parts Express:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-831

The idea, was to use a pair of rare 2 1/4" 5W drivers for L & R and use the sub inside the box for bottom end.

Anyone here use this sub before. I'm not going for really loud output, but the low 82db efficiency has my attention, and I'm wondering if it will still be louder than an avg boombox.

Also, are there any other small subs out there that may do as well? I'd rather have a 2 ohm sub if I can find one.
 
y8s said:
use 4? that'd raise your sensitivity :)

And also won't be so mini anymore :)

I was thinking about two of them, but I'm really wanting this to be small, so I want to stick with one sub. I want the box to be 7 or 8 inch cube max, just big enough for a portable FM/CD player to fit on top.

The sub has over 9mm of Xmax, so I'm thinking even if it's not loud, it should still add some much needed bass. I've never seen a 5 inch sub like that before.
 
That's cool. Glad you have had good experience with their small subs.

I don't need it super loud, just good sound. It will mainly be used at work for portable sound, or at home for sound at my spare computer. Or to have sound in one of my cars that has no stereo. I'm hoping this type of sub will sound good. I want at least a good 50-60hz bass note from this thing. Lower is a bonus, but not necessary.

That sub is rated close to 0.25 cu ft, so my small box should be fine. I want to make sealed on the backside of the woofer, with a small vented chamber on the front side, kind of like a bandpass, but open, for the bass to come out of. This is to protect the woofer, and try to get some more output. Feel free to comment on the box needed for a small subwoofer.

I want to stick with the 14.4V NiCd battery, to get good output. I'll just have a 12V 4A (17V unreg) transformer providing the charge for the battery, and to provide mains power for the amp. I'll use the batteries like big filter caps for the DC power coming in, and it will keep the batteries slowly charged and topped off at the right volts.

The Car Radio the IC amp come from had max power rating at 4 ohms a channel of 40W x 4 @ 14.4V (16W RMS x 4) So using 2 8 ohm speakers (8WRMS x 2) and a single 4 ohm subwoofer (16WRMS) should use about 1/2 the total wattage of the IC (32W RMS) with IMO should still be pretty loud, but not kill my batteries.

IC HA13158A is the amplifier.
 
Have Them In My Car

EWorkshop1708 - for what it's worth, I have a pair of W5-1138SMs in my car, a Ford Focus 3-door. I put them on the rear two channels in the factory locations.

The efficiency is an issue, so I've adjusted the amp gain, but I can say that they are very clean and accurate - I listen to a lot of classical music and they have no trouble with pipe organ and bass drum, etc. - they don't seem to miss anything down in the low end. I may put an 8" third sub in my trunk area (5-channel amp) to see what difference it makes, just as an experiment.

I wouldn't recommend them for high SPLs with things like rap music and synthesized base, but for small systems and limited space applications they are quite appropriate.
 
EWorkshop1708 said:


That sub is rated close to 0.25 cu ft, so my small box should be fine.
I want to make sealed on the backside of the woofer, with a small vented chamber on the front side, kind of like a bandpass, but open, for the bass to come out of. This is to protect the woofer, and try to get some more output. Feel free to comment on the box needed for a small subwoofer.



Hi,

An 8" cube of 1/2" stock is 0.2 cuft Q=0.75, 3/4" 0.16cuft Q=0.8.
Bass in boombox context is very good, f6 at 50Hz, f10 at 40Hz.

Given this I cannot see why the volume penalty of a bandpass
arrangement, especially as the sub might need to go quite high
presuming that the 2 1/4" drivers will not do low.

:)/sreten.
 
I have a W6-1139S0 that was installed in the factory location of the sub in a camaro BOSE system. The driver played very loud and clean, but the camaro is :angel:no longer with us:angel: so the driver was given to me.

Eventually I plan on making a small cube like the one mentioned above but with a built in amp and linkwitz transform circuit. I think flat to 30hz is a reasonable goal considering how much xmax this little thing has.
 
Wow, imagine a 30 hz mini portable sub :D hehehe

BTW some good news. I got a 1.7AH 14.4V NiCd battery, and it seems that fully charged, it puts out over 16V! If I leave the battery charging with the 12V transformer, the battery stays cool, because I'm not charging with an elevated voltage, so hopefully overcharging wont be an issue.

I'm hoping that 16V, even if it sags, gives a better RMS power at full charge than planned - to help better drive that sub. Datasheet says max 18V. :eek: I get a little under 18.8V when charging, so I think it will be ok, because I'm using a better heatsink, and running the chip at 1/2 power. That little sub looks beefy, so I hope it will last long at being used under the RMS power.

What's the best arrangement is for a small portable sub? I planned on a down-firing sub.
 
That's what I said back in post #8 but nobody seem to look... The ED driver should kill that Tang band and only for a few more $$ Dave:)

Tang Band 5.25'' 7kv.2 ED 6.5''
40w rms 80w max 200/400w rms
4ohms dual 2 or dual 4 ohms
fs 45hz fs 28hz
spl 82db spl 85db
vas .24cu ft vas 22l
qms 2.68 qms 10.5
qes .61 qes .30
qts .49 qts .29
xmax 9.25mm xmax 13 mm Sealed small 0.2 cuft
Sealed ideal .25 cuft
 
...The ED driver should kill that Tang band...

Not in my opinion if the prerequisites are followed: A box max 7-8" cube i.e. about 5 L and the use of the given 4-channel BTL Car Radio IC.
Actually, for this case the ED driver would be wasted. See the picture: 1(1)

b

1(1)
 

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bjorno said:


Not in my opinion if the prerequisites are followed: A box max 7-8" cube i.e. about 5 L and the use of the given 4-channel BTL Car Radio IC.
Actually, for this case the ED driver would be wasted. See the picture: 1(1)

b

1(1)

Wow :eek:

Excellent job on the document, graphs, and cutouts from the PDF for the amp chip!

I'd hate to waste such a nice high-powered 6.5 woofer on such low power. Also the smaller 5 inch woofer makes more room inside the box for electronics because it doesn't have a huge magnet.
 
BTW, I finished the 4 channel BTL IC amp for this subwoofer project!

I followed the datasheet, used a few other components from the car stereo PCB to save me on parts, and use what's available.

Used 100uf instead of 10uf for the filter :D
Used 47uf instead of 4.7 for the mute.

Used cat 5 wire for inputs, used all 8 wires, 4 inputs, 4 grounds, works well.

It was NOT easy to connect those 23 pins on the IC. Anyone here that does PTP with IC's I give my congrats. Instead, I just used 3 inch wires from each pin into the circuit board. Also the circuit board makes it easy to mount the additional parts. I used a heavy 2 x 3 inch heatsink, and used a bar to press the IC to the sink.

It's very loud. I only used a 12V Nicd battery for testing, and when I drove it into clipping with a 3W 8 ohm speaker, the coil started to smell like it was burning :hot:

If that 5 inch sub is 40W, it's probably sufficient to not burn the coil in case its driven into hard clipping. For the highs, I'm blocking the bass to prevent blown speakers. I'm also hoping that bi-amping highs and lows like this will make it sound louder and clearer without bass distoring the smaller speakers.

Thanks for all your input so far, this could be a very interesting project......
 
...If that 5 inch sub is 40W, it's probably sufficient to not burn the coil in case its driven into hard clipping...

Hi,

Agree, and for close range listening you might also consider LT for slightly more extension on the lower FR end as well. See picture 1(2)

Im curious about the rare 2 1/4" 5W drivers for L & R you mentioned, can you post a picture and what brand?

b

1(2)
 

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