First time subwoofer

[rudypoochris]

I decided to go ahead and make a DIY sub. I wanted to buy a Mackie SWA1801 originally, but realized it would not really compliment my living room, nor go as low as I wanted frequency wise. Also I find them to be quite expensive. I wanted the SPL's it outputted though as I frequently throw dance parties in my living room (college living room I should add?).

I originally was looking at doing a 4 x 15" or a 4 x 18" setup, but soon realized after running through a couple sub programs, that I would have quite a difficult time finding inexpensive (reads very inexpensive) drivers that would hit low frequencies. All of a sudden I decided to peruse and start plugging into some programs woofers in the 10-12" range, and voila... I found that I could much easier find cheap woofers with low end, most likely due to the larger selection. Unfortunately though this low end came from massive cabinet sizes.

In any case, I went nuts and stuck 8 x 10" woofers in a 96x24x30" box (approx 980 liters interior volume). The choice of 8x10" woofers reflects approximately 2.5 times the surface area of an 18" woofer. This should deliver the SPL's I want while keeping tight bass. The woofers were also cheap which is a plus. Two sub design software programs indicate that this combination will hold within -3db down to 26hz with an RMS output of 130.6-db. If the ideal 1800 liters had been reached 24hz -1db would of been obtained). These calculations are not including room gain or any effect that the poly fill has on the subwoofer's freq. range. This is merely what the programs indicated, that doesn't mean reality reflects this. I still have yet to test it with a DB meter.

The box is packed with 24# of polyfill and an HPSA1000 amp (this is a good amp, but I would in retrospect just harvest a Sunfire 2700w amp, but then my house circuits would be blowing all the time anyway...). The box is constructed of 3/4" MDF on the face, back, and top. The sides and bottom are 1/2" MDF due to availability at time of purchase. 4 handles are also present, two at each end, as this thing probably weighs around 400lbs. While building this I realized that I did not actually have a center speaker in my 7.1 system, since I was adding so much bass to the room I decided to go ahead and turn the sub into a center channel as well. Installed in the sub are a set of 4 x 4" mids and 4 x 4" tweeters with a 4500hz 300w x-over from Dayton. The frequency range should be 100-20000+ hz for those bits. The center speaker is really just an after thought and is mainly there for adding some SPL in the mids and highs when needed - I highly doubt it is beautiful sounding, although it does sound 'nice' to my ears.

All in all I would say I am quite happy for a first project. I learned a lot and would concede that there are things I would change if I did this again. Next sub I build will probably be much smaller though as it will be for PA use. I will probably do a 4 x 15" setup and suck up the fact that I will have not so beautiful looking DB curves down low.

Let me know what you think/questions/future advice. Sorry for the gigantic pictures. Also I guess my camera lens is dirty... Total cost ~$750 not counting mistaken purchases and what not. It should be cheaper than the Mackie, louder, wider freq range, so I am happy. That being said it is physically huge. It really rumbles though! =]

There is bracing inside it by the way... I just did not CAD it in.

[marchel]

Hi, Nice project you got,

But I would advice that you add 3/4" materials on the panels that are only 1/2" thick. And dont buy Pro audio amps with fans to power any speakers in your room, cause the fans on those amps are very noisy in a home condition.

[rudypoochris]

Any particular reason why I should double back with 3/4" MDF? Just wondering. I know it is IDEAL, but in all honesty I don't notice a difference. Any insight would be appreciated!

Additionally I am running a class D amp at around 1140 watts, it is a plate amp for a subwoofer, no fan. =]

IT DOES rattle though at specific low frequencies... I have been thinking about running some of that foamy adhesive speaker tape underneath its back edge, do you think this will fix it - or is the resonant frequency just going to move somewhere else within the sub's operating range.

[rudypoochris]

The "IT" I am referring to in the previous post, is the subwoofer amplifier. It is a plate amplifier and it seems to rattle around 40-50hz or so on high load.

[marchel]

There are many causes or rattling sound.

Adding weather sealing foam between the amp and the box could reduce the rattling sound, adding re-enforcement around the area of the plate amp could reduce the rattling too.

Adding 3/4" to the thin areas might reduce the vibrations all throughout the box, which might help in reducing any rattling sound.

[Sweden]

nice building

[form109]

Impressive.

[chris661]

My number one source of rattle is Everything Else in my room. Usually, it's the furnature, or other things like that.

Must be said - a very impressive bass unit, especially for a first go.