Building a Subwoofer

Slappy :

This can be a very rewarding project!! Go for it. Some hints :

1. Some auto subs CAN make good home subs. Go for those with an Xmax over 10mm, Fs between 18-25 HZ, Qts of .30-.45, Vas of 3 cubic feet or less and a BL of over 10. Check out the Titanic subs at www.partsexpress.com.

2. Go for a sealed configuration (and I mean SEALED, more on that later)as they are much easier to design, perform great and are vastly less sensitive to small goofs in driver parameters and cabinet volume than a vented alignment. A system Q of .5(tight) to .7 ("musical.???")is quite achievable. I like a system Q of .5-.6 because with digital EQ you can pump the level below 40 HZ up a few DB and get scary, thrilling & TIGHT deep bass without it intruding on the midbass (plus a kidney massage if you play loud enough). And believe it or not, you can get this with an internal volume of 3 cubic feet or less (sometimes much less). A system resonnance frequency (F3)between 40-45 HZ is quite acceptable as "room gain" will prop up the response below 40 HZ with solid in room extension to 20-25 HZ..easy.

3. Make the walls thick & braced. A sandwich of two pieces of 5/8" MDF with a layer of 3/8" plywood in between works great. With internal bracing you'll end up with an extremely rigid & inert enclosure. Umm..and heavy too. Get a hand truck to move it around as each one will easily weigh over 100 pounds when finished.

4. SEAL IT. The drivers you will use have extremely high excursions and place tremendous pressure differentials on the enclosures. Any air leaks will degrade performance, especially impact & speed.

5. Some "plate amps" out there are quite good and are nifty packages if you want to mount them in the enclosure or in a seperate, small sub enclosure (no pun intended). The 250 watt jobber at parts express is excellent and cheap. A GREAT nitch amp for subs is the ADCOM 555 & 555 MKII stereo amp or the 565 mono blocks.

6. Use a good quality, external electronic x-over and slopes of 24 DBper octave, especially when cutting off the top end of the sub. Most sub drivers SUCK above 80-100 HZ. The DBX drive rack PA is a steal!!(Does everything in the digital domain, including EQ...a poor mans TACT...good sounding too as long as you don't push the DSP engine into clipping). The Marchand units are excellent as well.

Good Luck!!!

Slappy, good luck with your diy sub.

I am building my own sub with most of the suggestions stated earlier. I am on my third and final prototype before I make the final box. A useful tool you can get is Granite Audio "Super Bass CD" from Quest for Sound on A'gon. Go to the site for info.

I did find out that an external amp and crossover are better than plate amps. I did try both. With external you get more air volume, less chance of an air leak and most likely a better quality amp and crossover.

Also, couple it to the floor as best as you can so it does not move when played. If you have carpet, use spikes, hardwood, as in my case, 1" squares from scrap wood angled down a bit glued to the box with blu-tac on the bottom of the squares.

Get some good wiring, posts and solder. Try Cardas out.

Last, you will need a hand truck to move this around. I do not know why, but diy subs tend to weigh a hellava lot more for some reason.

Again, good luck with your project and new career.

Eldulcesol's suggestion is an excellent one. I sometimes use an NAD 2600A as a subwoofer amplifier with good result. This was their biggest amplifier of that iteration of the Monitor Series. 150 wpc continuous, rated extremely conservatively with the NAD Power Envelope that had either 4 or 6(?) of headroom. I have driven any speaker I have thrown at it, and in the late 80's, there were some extremely difficult loudspeaker loads out there.

The best thing about these are the low cost you can find them for, often under $200. And, if you ever want to use it as a full range amp, it makes very good sound.

Trelja: I've owned 2600's before and don't think it's too bad of an amp either. They do work quite well with Klipsch speakers from my experience. While it might work out reasonably for a sub amp, i don't know where you are going to find one for anywhere near $200. The lowest i've ever seen one go for was $275. They typically go for between $300 - $350 from what i've seen. I didn't have any problem selling the ones that i had at $325.

As a side note, ANY amp that is driving a sub(s) can be improved by increasing the power supply reserve i.e. adding filter capacitance. This can really tighten and stiffen the bass, especially on amps that are noticeably "loose & sloppy" to begin with. Sean
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