Woofer enclosure help?

[kentrol]

Kay, I've been trying to figure out how to make the best sealed (I'd prefer ported honestly...) woofer enclosure for a 6.5" woofer.

Here are the specs written on the Speaker:

4ohms
20 oz mag
100Wrms
200Wp
1" voice coil
Freq : 50-6000Hz
resonant frequency: 50Hz
(sensitivity i think) - 90Db
thanks for any help.

 

[kentrol]

this would be great cause i need to submit a proposal tomorrow

 

[kentrol]

No one has any help?

 

[ronv]

There are lots of calculators. How about this one?
**broken link removed**

 

[unix60959]

the best way to do this is to figure out the manufacturer of the woofer and see what dimensions and internal volume they suggest for a sealed enclosure. although if you cant find the best specifications you can just make an enclosure that fits the woofer, say 8" x 8" x 8". Note that you can pretty much put it into any size sealed enclosure and it will still sound fine, as long as your box is not significantly large, like 4' x 4' x 4' or something. also note that a sealed box is louder than a ported one but the ported box has slightly better quality. but port size is very tedious if its off by a little it can sound like crap

 

[crutschow]

also note that a sealed box is louder than a ported one but the ported box has slightly better quality. but port size is very tedious if its off by a little it can sound like crap

You have it backwards. A ported enclosure, since it has sound coming from both the speaker and the port, will be louder than a sealed enclosure. But sealed boxes tend to have better transient response so are usually considered preferable for accurate music reproduction. Since most people are looking for maximum bass for home theater sound effects and not particularly worried about accurate music reproduction, they go for the ported subwoofers.

 

[crutschow]

I Googled "subwoofer enclosure design" and got many hits such as this.

 

[cr0sh]

Something that I've had pretty good success with in the past is a 3:1 ratio bass tube - basically, a tube on the front of the woofer 3 times longer than a tube on the back of the woofer; this can be easily built as an enclosure. For a 6.5" woofer, I would take the size of the woofer, and multiply it by the ratio; so the front tube/path should be about 19.5" long, and the rear tube/path 6.5" long (don't go crazy here - a 21 foot by 7 foot tube won't make it sound better).

 

[ronv]

Something that I've had pretty good success with in the past is a 3:1 ratio bass tube - basically, a tube on the front of the woofer 3 times longer than a tube on the back of the woofer; this can be easily built as an enclosure. For a 6.5" woofer, I would take the size of the woofer, and multiply it by the ratio; so the front tube/path should be about 19.5" long, and the rear tube/path 6.5" long (don't go crazy here - a 21 foot by 7 foot tube won't make it sound better).

Is this the same as you see Bose use?

 

[cr0sh]

I was wondering if somebody would catch it - yeah; I first read about it when I was a kid in high school in an old pop sci magazine (forget which issue) - I've tried it in different configs, it seems to work rather well. Probably still protected by patents or something, so you couldn't sell it, of course. Fun to play around with - easy and cheap to build (my first version was done with a old 3.5 inch midrange and a carpet tube). Heh.

 

[ronv]

I gotta try it! Is it a tight fit front and rear of the speaker? Maybe a little picture??? Bet I could use PVC pipe?

 

[cr0sh]

Yes - tight fit; PVC or ABS (as thick a wall as you can find) is best. You can also make an enclosure if you can route the "straight line" path of the tube (basically you fold the tube on itself); You could also fold the PVC/ABS pipe using fittings, if you wanted - just keep the straight-line path in the 3:1 ratio, with the front of the speaker toward the the longer path. IIRC, the rear path should fire away from the the front path - the outputs of front and back should face 180 degrees opposite each other (I think it has to do with phasing or something). Good luck, let us know how it turns out (I know mine turned out pretty well; I just placed the speaker between the carpet tubes after I had cut them with a coping saw, and duct-taped it together, running the speaker wire out a small hole - I think I drove the contraption with an old car audio amp which had one channel blown that someone gave me; this was over two decades ago).

 

[cr0sh]

Here's a very bad drawing of the layout - I really need some CAD software - lol...

**broken link removed**

Note that the speaker doesn't need to go "edge-to-edge" of the tube, just get it close; the front and back do need to be acoustically separate (imagine the speaker is mounted to a baffle inside the tube). The tube can be round (PVC/ABS), or square, or any other shape; you can also set up multiple drivers in the same tube provided they are all in phase, of course. Once again, while the above image shows a straight tube, you can fold the tube, provided the centerline distance ratio remains 3:1 (remember to take into account any bend lengths, etc).

Hope this helps your understanding - its pretty basic, really...

 

[audioguru]

The enclosure for a woofer is suposed to be designed by using the very important missing Q spec's of the woofer so it does not resonate too strongly which will make it sound like a cheap boom-box.

The tube enclosure guarantees "one-note bass" which you probably do not want.

The resonant frequency of the woofer is so high that when it is increased (to maybe 100Hz or 150Hz) by the volume of the enclosure then deep bass frequencies will not be produced. It might be a car woofer that is designed for a huge enclosure (the entire trunk (boot?)) of the car. When the enclosure is too small then the speaker becomes very boomy at a fairly high bass frequency.

 

[ronv]

I'll try it when I get back from vacation. Maybe it will sound like the Bose.

 

[audioguru]

Bose home sound systems used to be very expensive for what they were:
1) Two cheap little 2.5" satellite speakers. The low power amplifier peaked the high frequencies so that the little speakers sounded something like tweeters.
2) A cheap little 4.5" woofer in a ported enclosure. It boomed at about 100Hz but did not produce deep bass frequencies. People seemed to like the boomy sound.

Their new sound systems have no specs.

Their expensive 901 speaker uses nine cheap little 4.5" speakers and an equalizer that boosts highs and lows and its response cureve looks like a "happy face". Some people like the way the little speakers double deep bass frequencies (feed it 50Hz but hear 100Hz) and the way the "full-range" speakers modulate and distort high frequencies with the bass frequencies.

 

[ronv]

Still expensive but you know how it is now days -- If it fells good just do it!

 

[bountyhunter]

No one has any help?

It's been a while since I designed speakers, but you are missing a bunch of specs. I recall something like "VAS" and "Q" which tell what internal volume the enclosure has to be to get the quoted lower cutoff frequency. The speakers "Q" tells whether it is best in a sealed (acoustic suspension) enclosure or ported (bass reflex) enclosure. Low Q speakers typically work best in bass reflex.

I do know a speaker with a resonance of 50 Hz is useless as a good woofer. The resonance frequency is slightly below the usable range of the speaker. I recall good woofers (like 15 - 18") would have resonance frequencies of like 18 Hz. You could build a speaker with usable response down to maybe 25 Hz with one, but the enclosures were huge.