Hey guys, I just joined here with hopes that you can lead me in the right direction.I have been researching subs for my daily driver (Chrysler 300C). I listen to primarily hip hop and love very deep loud bass. I was pleased with my last system that consisted of (1) JL12W7 (1) RF BD1000. Ported box tuned to specs.
I am attempting to setup a budget system. I will be purchasing an amp @ 1000rms. I have narrowed it down to:
(2) 12" RE Audio SE
(2) 12" DD 1500
(2) 12" Alpine Type-R
(1) 15" AE AV
(1) 15" Fi Q 15
What subs will perform the best with only 1000 watts continuous? A good SQL sub is my goal.
I would like it to be as loud as my W7 while still maintaining some good musical accuracy! And please keep in mind that I will only be running 1000rms!!
I like this comparison because these are woofers we often are asked about in comparison to our AV15's. The comparison also can easily show how unique our woofers are, and why they are used in million dollar recording studios, some of the most high end home theaters, high end front of house PA systems, and some extremely high end music only systems. Our woofers aren't mass produced. They are individually handcrafted for each customer once they are ordered. Every steel piece is machined by hand to extremely tight tolerances. Every cone is hand finished or treated. Every driver is broken in, tested, and parameters measured before ever being packaged up. We stress over every detail from the engineering behind the design to the adhesives used and the efforts we go to QC the woofers.
That said, lets look at the comparison and what makes a woofer sound good. When you talk about sound quality, what is really being referred to is how accurately the woofer can reproduce what it is being asked to play. Obviously the type of enclosure, Q of the enclosure, tuning in a vented enclosure, etc will have an effect on this, but that applies to all drivers. It's important to realize that a woofer doesn't sound good or bad just by accident. There is no voodoo or magical qualities that make this happen, but real engineering principles based on electromagnetics and thermodynamics that determines the ability to accurately reproduce sound. For all practical purposes the motor is the determining factor for this. A cone, surround, spider, etc have virtually no effect on response below 100hz.
So what makes a low distortion motor? If you want you can check out our paper on the Lambda 001 motor
http://www.aespeakers.com/Lambda001-1.php I will summarize here though with the 4 things that a motor should have.
(1) Linear magnetic flux levels across the entire VC movement range.
(2) The flux should be fixed permanently and not move, this is however not the case in 99% of speakers.
(3) High heat absorption properties as close to the VC as possible.
(4) Low and Linear inductance as the VC moves through its entire range
For part 1, the first issue is symmetry. You want the flux to be symmetrical on the inward and outward stroke. The first step in doing this is an extended pole. All of the drivers that are typically considered good SQ woofers will have this. Symmetry will set a driver apart from others, but this is as far as most woofers go. There is much more to look at. Secondly you want to make the BL curve more flat or broader. A very long coil can do this to some extent like the JL. XBL can get flatter BL curve. An underhung design gives the flattest BL curve and we discuss that possibility in our paper. With an overhung coil, a taller gap also distributes flux over a longer range and helps to flatten the curve. We go with the tall gap option as it is really approaching what an underhung design can do.
Then we get to number 2. 99% of woofers to not address the flux modulation issue. This is where our drivers greatly excel. As a coil is energized it becomes an electromagnet with the pole being it's core. Much like the little electromagnetic crane I built back for the science fair in middle school. As this electromagnet moves through the gap it's own field moves or modulates the permanent field. As this happens the symmetry and flatness to the BL curve that was mentioned above is totally changed. This can greatly distort the waveform and the driver is no longer accurately producing what it was supposed to. The flux modulation also contributes to the "slow" sound that people often describe. For the coil to reverse direction it has to push against the permanent magnetic field. As this field is now continually moving the ability for the coil to push against it and change direction is hindered. The fix to this is to have a highly electrically conductive layer permanently mounted to the pole piece. This is called a shorting ring and it "shorts" the flux in position so it cannot move. The closer to the coil and the more surface area it has, the better it's effect. This is why we go with the full copper sleeve on the pole. This simple piece of copper is what sets our drivers apart from all the others in terms of their ability to accurately reproduce output.
Next are the high heat absorption properties. For the coil to not heat up it needs to be able to get rid of heat quickly. Air is very poor at absorbing heat. You want to keep the gap as tight as possible so the coil can dump heat to the top plate and pole. The more surface area the better which is another reason we go with a very thick top plate to increase the heat sinking area. Steel absorbs a lot of heat but it doesn't do it very quickly. You will often have a coil fail not because the steel is too hot, but just because the heat doesn't go to the steel quick enough. This is another benefit to the full copper sleeve. It is much more thermally conductive than steel and pulls heat away much faster. The same premise is used on frying pans where the bottom has a layer of copper to warm the pan up quicker.
Finally is the issue of inductance and distortion created by varying inductance. The coil is basically and inductor. An inductor with an iron core (the pole) is much higher inductance than an air core inductor. As the coil goes forward, out of the gap and past the end of the pole, it transitions to air core. As it goes inward it transitions to full iron core. As this happens the upper response of the driver greatly changes from the inward to outward stroke. This is another issue that leads to great distortion. The key to fixing this issue is to force the coil to act like an air core throughout it's entire range. This means extremely low inductance and low variance in this inductance value. This is again done by the copper sleeve on the pole.
Most others ignore these issues for the car audio world because they are "just car woofers" so who cares. We address them all in every driver we make. The high end recording studios demand the absolute most accurate reproduction for the mixing and mastering process. Our OEM customers in the hifi realm demand this as well. Our pro audio customers demand the most accurate output with lowest power compression and want the assurance of quick heat transfer so the drivers will be nearly bulletproof when running thousands of watts for hours on end.
When I designed the AV series for the car industry and DIY home theater industry, I kept in mind every one of these issues. Every detail was stressed over and needed to be perfected before the drivers were released. This meant an 18 month delay in the release, but the results were well worth it. I wanted to keep nearly every part made here in the US to keep control of quality. This wasn't easy and it meant doing a lot of work in house. A LOT more than I had planned for and probably more than any other manufacturer. We bring in steel from china but they don't do tolerances well so I bought 2 lathes to finish machine every piece to within .003" tolerances. I had the copper sleeves custom made by a company in lower Michigan and we machine every pole to that tight tolerance to properly apply the sleeve. VC's are wound in Florida to the highest standards. Spiders come from a company in Illinois and we bought a sewing machine to attach all the lead wires to the spiders in house. The alum cones are spun in California but we needed to be able to control the finish process for aesthetic reasons. We made tooling to hand sand each one to 220grit texture and then clear coat them with a special aerospace coating in our own paint booth. Surrounds are thermoformed in Illinois with tooling we designed. We then trim and glue every surround to the cones in house. I spent 6 months evaluating adhesives to assure that every bond was made the absolute strongest it could be without regard for the cost of the adhesive. There were literally no corners cut throughout the entire process.
Both the engineering behind the AV woofers and the attention to detail during production are what will set them apart from all the others. You will not find a driver anywhere in the car audio realm that addresses these issues with distortion and accurate reproduction like the AV woofers do.
John
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