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car audio newbie, subwoofers?

post #1 of 8
3/20/05 at 11:50pm
Thread Starter 
I know absolutely zip about car audio, and especially puzzling is subs. I was in a car audio store and spotted 10inch woofers for $15 each! I was very tempted to buy them just for kicks (literally). They had cones from 10-20 inches and all were surprisingly inexpensive. So this got me thinking, why not spend ~ 50 bucks on a pair of 12 inch car woofers, mount them in a simple sealed enclosure, and use them in my HT for non-hifi listening such as movies? Would this work, and are these cheap car subs any good? I can live with them as long as they can put sub-30hz at respectable volumes.
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post #2 of 8
3/21/05 at 1:06am
Quote:
Originally Posted by pne
I was in a car audio store and spotted 10inch woofers for $15 each! I was very tempted to buy them just for kicks (literally). Would this work, and are these cheap car subs any good? I can live with them as long as they can put sub-30hz at respectable volumes.
Well, decent sub will run more than $15. I doubt that a sub that cheap could even put out any real low bass. My 10" Image Dynamics IDQ sub was $170. It is really well made and put out clean bass down to 25Hz. If you bought a sub and built an enclosure for it, you will need a mono amp to drive it. This amp also would require some sort of low pass filter to block out the high frequencies from going to the sub.

Actually, subs with built in amps can be had for under $100. Sony makes a decent unit...
http://www.crutchfield.com/S-Kf1jt8K...0&I=158SAWM250
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post #3 of 8
3/21/05 at 12:58pm
You would want to port it if anything, sealed boxes have a natural ~12dB/oct rolloff starting at their F3, which is normally around 50-60hz. This means that no matter what sub (or how many subs) you got, the response would start falling off right around the crossover point, if your F3 was say 50hz, 25hz would actually be a full 15dB lower than the upper bass. In a car this isn't a problem because you have something called "cabin gain" which increases the sound's amplitude according to the car's transfer function, in a sedan you normally get a ~12dB/oct boost starting around 55hz which matches very well with a sealed box's natural rolloff, and the final result is normally a very flat response into the 20's or even the teens. In a room you have some gain but it's not nearly as drastic, so in order to get a solid response down to the 20's it's almost a necessity to port it. Luckily in a room you have plenty of space to port a sub, and the sacrificed upper end of its response isn't really a problem because most home speakers can go plenty low enough to take up the slack. If you want to build a ported box check out WinISD, for home use you normally want to tune it very low, if you'll be using it for movies then a tuning frequency in the high teens would be optimal, but the low to mid 20's wouldn't be bad. And you're going to want a much better sub than $15 can provide, that I promise you.
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post #4 of 8
3/21/05 at 1:16pm
If you're looking for sub companies (car), don't miss elementaldesigns -- great products, great service for very good money, imho.
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post #5 of 8
3/21/05 at 1:44pm
Quote:
Originally Posted by pne
mount them in a simple sealed enclosure, and use them in my HT for non-hifi listening such as movies? Would this work, and are these cheap car subs any good?
As long as you have a spare power amp to drive them, why not. Good experiments for not much money.

While I've been a strong critics to price = quality comments, I think $15 would be kind of low to get decent sounding woofer. I once bought very cheap woofers "just for the kick of it" and damn there's no bass coming out of that woofer at all ! Only mids and midbass. Filtered, they will put out very soft sub bass despite cone almost thrown out off basket.

If forced to say price cutoff, I'd say $100 each for decent 10 or 12" woofer. Add car amp with built in crossover to the cost and you'll appreciate some of active subwoofer offerings.

Having said that, I've gotten good results with used focal sub in a sealed enclosure that beats an old velodyne on musicality, at roughly 1/2 the price. Second runners on musicality are boston and a/d/s subs. For non musical HT: JL, JBL or kicker will shake the room. Some can be had for unbelievably low price on ebay.

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post #6 of 8
3/21/05 at 6:36pm
Well, the enclosure is very important to frequency response, but also, the driver must be reasonably designed to extend down to the true bass frequencies. If there is excursion and you don't hear anything, you have a box that isn't properly speced for the driver, most likely.

Look for something that has a fair amount of excursion, and a decent sensitivity. Usually the larger the driver, the less excursion you will need to achieve decent sound. And you will obviously need a bigger enclosure with a bigger driver, but I wouldn't go with anything smaller than 12" for a bass unit.

Also, you don't need a kilowatt amp to put out serious bass. If you get a sensitive driver, 1 watt will put out serious sound in a small room. It seems many subs aren't rated for music power, but actual thermal power.

Magnet size is important too, a voice coil that is too small means sloppy bass.
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post #7 of 8
3/21/05 at 6:56pm
Quote:
Originally Posted by JeffL
Well, the enclosure is very important to frequency response, but also, the driver must be reasonably designed to extend down to the true bass frequencies. If there is excursion and you don't hear anything, you have a box that isn't properly speced for the driver, most likely.

Look for something that has a fair amount of excursion, and a decent sensitivity. Usually the larger the driver, the less excursion you will need to achieve decent sound. And you will obviously need a bigger enclosure with a bigger driver, but I wouldn't go with anything smaller than 12" for a bass unit.

Also, you don't need a kilowatt amp to put out serious bass. If you get a sensitive driver, 1 watt will put out serious sound in a small room. It seems many subs aren't rated for music power, but actual thermal power.

Magnet size is important too, a voice coil that is too small means sloppy bass.

I agreed with you up to the end. Magnet size doesn't have much to do with sound quality. By having a large diameter magnet you gain flux which increases your BL, but a high BL definitely isn't necessary for good sound. By having a deep magnet you don't really add anything to flux but you help to flatten out the BL curve which helps with IM distortion at high SPL, but that's a whole other discussion. A large diameter voice coil helps with heat dissipation and power handling, but it also increases the inductance (hurts transient and frequency response) and moving mass (lowers efficiency). It's all a combination of tradeoffs, a company can design an amazing SQ sub with a small voice coil and tiny magnet with a low power handling and very high efficiency (adire shiva), or they can design an amazing SQ sub with a huge voice coil, massive magnet, high power handling, and low efficiency (acoupower). Don't judge a speaker based solely on the size of its motor, it's the inside that counts
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post #8 of 8
3/21/05 at 9:49pm
eD has really become a joke for the past few months. Lots of people aren't getting service/products/or money back.

I'd wait until they showed improvement.


Check out Ascendant Audio.

For 145/160 (12"/15", respectively), very effecient and small box requirements due to an adjustable Q from a second small coil. XBL^2 enabled which means a much flatter BL curve (range of magnet power through stroke). Light moving mass (120g for 12"), 18mm xmax, low inductance. What else could you want for 145 smackers? Nifty carbon-fiber cone, okay!

While it's a new company, i've only heard good things about these guys and their woofers. Call and ask for Chad, great guy to talk to (or check 'em out on forum.soundillusions.net)
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