Subwoofer was jipped!?!?

Clob

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I was sitting at my desk listening to some tunes when I started to think. What is inside my subwoffer? I started to unscrew my Creative Inspire 5700 Digital's sub-box and I put my hand over the spaker to gently dump out the whole piece, but to my surprise! a little flimsy peice of foamy speaker-looking thing fell out that only weighed a few ounces! I was like WTF! When ever I watch my subwoofer thump, I see this thing hit and its not my actual speaker! I take my awstruck face from this flimsy POS and look inside the sub box and I see the actual speaker that is about 25% smaller! I had a "no way" expression on my face and I thaught I was ripped off and that Creative lied to me or somthing!

I knoticed one thing though. The sub sounded very hollow and had half the thump than before! I placed the foam piece on and it returned to its normal thump and volume! I have never seen such a thing before! From what I can tell is that this extra "speaker-thing" (knotice that I havnt the slightest clue on what it is called) actually helps the sub to produce sound! My real question is, Would it be better if the actual sub speaker was that much larger? or am I getting the same effects either way?


Thanks

Edit: I took some measurements on the sub and the front is 8" and the atucal driver is 5"! a 35.7% difference!!!

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
<P ID="edit"><FONT SIZE=-1><EM>Edited by Clob on 06/20/04 01:12 PM.</EM></FONT></P>
 

Clob

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LMFAO! I just knoticed a few other things! I took apart my center and surround speakers! The center is supposed to be a 21W speaker and it clearly says 12W on it! The surround speakers are supposed to be 7W and they clearly say 10W on it! HA!! What else can I find!

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

Crashman

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OMG you're so clueless! That flimsy thing is passive radiator, it's used INSTEAD of a PORT on a bass reflex settup! It's SUPPOSED to be a little bigger, that was part of the tuning!

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Clob

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LoL. I figured as much. I'm no speaker guru here. Honestly. But whats better when it comes down to it?

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

blah

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I did not know about Philips' wOOx a few years ago (was too poor for good speakers) so I made my own from the old dual 10 inch drive speaker. Just yanked the top speaker out, disconnected buttom one and put new speaker into the top hole. Was very pleased by the deeeeeeep and feelly sound of "my creation". But when I started to feel money in my pocket (paper can be heavy too;) I bought MS's SS-80 because it had that same design I had home. And guess what, 4 inch drive and passive reflector make it sound like at least 8 inch in it.

Advantage of woox is that at low valumes it makes bass more feelly and deepper (because of the amplitude the reflector can travel is longer than the drive's as it is just a piece of rubber) than with closed or open design, especially on cheap smaller speakers.

..this is very useful and helpful place for information...
 

Clob

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Ahh ok. thanks. I understand now.

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

Crashman

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As far as I know (because I'm not willing to do the physics), a larger passive radiator takes the air movement of a small, long-throw woofer and converts it to a large, short-throw cone, making it sound like a larger speaker at lower volume. As for me, I liked building fairly small enclosures, never made room for a passive radiator, and was therefor constrained to the use of port tubes.

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Crashman

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Nope, I'm sure I can fit a port into a smaller enclosure than a passive radiator. My last case project was pro grade, used 10" woofers in a 12" wide enclosure with a piano-black finish and rounded edges, looked like a solid block of laquor hollowed out for the speakers! Couldn't fit a passive radiator on that!

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Clob

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Hmm... Any good websights that explain all of that with good pictures? Mabie some good skeaker how-to should help.

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

Crashman

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Mental picture: OK, I choose drivers based on 3 main factors: Frequency response, SPL, and enclosure size. I built boxes that were 24" high, 12" wide, and 8" deep.
1.) The woofer was 10" diameter, requiring a 12" passive radiator
2.) A 12" passive radiator wouldn't fit the back, because it would have gone "edge to edge". The box was only 10.5" wide inside because the wood was 3/4 inch thick.
3.) I would have had to make the box 14" wide to fit a 12" passive radiator on the back.

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Clob

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AHH! www.howstuffworks.com provides some great information on the matter. Thanks guys for clearing this up for me! One again you two come through for me again! Thanks

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wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

Crashman

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I just looked at Howstuffworks.com and don't agree with what they said about bass reflex speakers being less accurate because they lack air pressure to spring the speaker back! You see, adding VARIABLE RESISTANCE to the speaker will basically muffle the hard hits! As far as I know from my former speaker building, the main reasons bass reflex speakers are perceived as being less accurate are harder to explain: The first being that a front port cancels out some of the air pressure from the speaker because the air is moving in the oposite direction, the second reason being that the front port receives it's sound wave as a reflection from the rear wall, putting the sound emitted by the port slightly out of phase.

I don't always agree with Howstuffworks on automotive technology either, it seems they often give inaccurate descriptions in order to make complex ideas seem simple, and some of that simplification/innacuracy results in the answer bearing little if any relavence to the truth.

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Clob

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Ohh. I understand. I plan on getting some Promedia ultra's soon. Would the ported subwoofer perform well? From what I understand is that when the box has a "hole" in it, generally it would have twice the volume output. correct?

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

Crashman

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Wow, no, but it seems like it would!

OK, first thing is, doubling the number of speakers increases the volume by 3db (same as doubling the power of your amplifier). But it takes 10 fold increase to double volume, it's a logorythmic scale!

OK, so you still get a 3db increase, which sounds like you just doubled the power output of the amp, but it's not twice as loud, only 30% louder. And that's before you consider the noise cancelation effect caused by the port moving air in the oposite direction of the woofer.

I can't tell you how MUCH louder it is, but it's 3db minus some loss.

On to my theory: Sealed enclosures, by offering variable resistance to woofer movement, reduce the volume of the "loud parts" of your song, making the volume flatter. But many people consider them more "accurate" sounding, probably due to the drawbacks for ported enclosures I mentioned earlier. I personally prefer the sound of a well-tuned ported enclosure because bass hits...hit harder.

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Clob

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:) Sounds like what im looking for. Thanks.

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 

Clob

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Would a passive radiator have a limit as to the force behind it? If I was to box a 250W 6" with a 10" radiator (example only) would the speaker behind it have to much power and blow or distort the radiator? Also I hear that radiators have bad/messy tuning. Hmm... I would like to look into building speaker cabinets. Seems like a neat little time consumer to draw me away from life.

mabie that 10k Watt Kicker would be a nice starting point LMFAO!

"If youre paddling upstream in a canoe and a
wheel falls off, how many pancakes fit in a doghouse? None! Icecream doesn't have bones!!!"
 
I got started by buying a Logitech 2.1 set and thought my bass was good. But after a while I wanted the same sound that comes from the 15's in my trunk, and ended up purchasing a powered 12 inch subwoofer. I ended up getting it for around $100, most likely by the time you build the cabinet and get the speaker, and find a proper ampilifer you will probably be over that price.

WinISD is a good freeware program you might look for, it is handy for designing speaker box setups, and shows results, calculates optimal demensions and such.

The link in my signature, near the bottom, there are some pictures, you'll see the sub setting there, with the baby sub (logitech) sitting on top, sort of looks like a paper weight!

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Crashman

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Ah, tuning...

There are MANY books written on it, and even though it IS an exact science, there are so many options and each with its comprimizes that what actually happens is some OPINION is used to determine the best configuration. That is to say, you could build 3 different designs, all scientifically sound, but one user might prefer one sound over the other.

The nice thing about passive radiators is that they replace ports. A problem with ports can occur in extremely small enclosures where the port length exceeds the available dimensions of the case.

Ports can add 3db over sealed enclosures. That doesn't sound like a lot, but since it takes 10x the power to make 2x the sound (10db), it's equivalent to DOUBLING YOUR AMPLIFIER OUTPUT! And don't forget that speakers can range from 87db/w at 1m to 98! So imagine this: My accustics (sp?) enthusiast friend said Carnigie Hall had at one time a 40w speaker system! A speaker with 98db sensitivity will produce as much sound as a speaker with 88db sensitivity at 10x the power!

I'll treat Ports and Radiators as equivalent for a minute when speaking of placement: Most experts agree that front firing ports give you more sound than rear facing ports because they actually face the listener. The problem is that the air movement OPPOSES the direction of the speaker, so there's some cancelation. If you have an ideal placement for your speaker you might be better off with REAR placement so the air travel is in the same direction. The problem there is the sound faces away from you, the solution is a room with high density walls having the speaker placed an ideal distance from the wall, so that you hear REFLECTIVE accustics from the port nearly simultanious to the sound coming from the driver. And now getting to passive radiators, that allows you to put the radiator directly behind the driver for great space savings.

I had some 4.25" woofers on a 5x7" plate (included 1.25" tweeters) that were leftover stock for some high end RCA big screen TV's. These things did something amazing: They hit very low frequencies, I think as low as 41Hz, which doesn't sound incredible until you consider they were only 4.25"! And they had around 1.5" of travel! I put them on a 100W sound system (they were rated at 20W I think) to see how far they'd go, yes, the bobbin bottomed out, but any volume just lower than that sounded great!

I think that's the concept of a lot of compact subs, they use enclosures that make the speaker sound much bigger than it is. Messy tuning on passive radiators? I can only suggest you try them, and figure it out. Bad internal accoustics can often be minimized by increasing the amount of insulation inside the enclosure to minimize reflective waves that would distort the speaker.

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