3in. vs. 4in. coils

[Seattle206 10+ year member]

What are the major structural differences between motors using 4in. and 3in. coils?

What are the benefits and drawbacks of using a 4in. coil over 3in.?

Why aren't 4in. coils more common and whats holding back even bigger coils?

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[jmanpc 5,000+ posts]

One inch.

 

[Seattle206 10+ year member]

One inch.

haha touche

 

[jmanpc 5,000+ posts]

Actually, the main reason you don't see many 4" coils is because there are restrictions when it comes to suspension. Most baskets can't handle spiders big enough to make it work. Most companies don't have the money needed to custom-tool a basket to handle a larger spider. That's why you see companies like RF and Orion making subs with 4" coils-- they can afford it. That's why the RE destroyer was a failure. 4" coil + 12 spoke = fail

 

[Seattle206 10+ year member]

Actually, the main reason you don't see many 4" coils is because there are restrictions when it comes to suspension. Most baskets can't handle spiders big enough to make it work. Most companies don't have the money needed to custom-tool a basket to handle a larger spider.

What are the benefits of a 4 inch coil? I'd assume the bigger surface area increases power handling..Is there a drawback in sound quality? Or is it simply because production is harder and more complex?

 

[jmanpc 5,000+ posts]

Its just more effort than's worth it. 3" coils are fine for your typical 18" woofer.

 

[Cravingbass123]

my treo ssx 18 has a 4 inch coil

and thanks to mostly that, it takes 3200 rms daily in mah jeep

 

[Seattle206 10+ year member]

What size spiders are needed to make a 4in. coil feasible and why can't the 12 spoke handle it?

 

[kovemaster559 5,000+ posts]

big *** beefy *** spider like a black widow

 

[jmanpc 5,000+ posts]

What size spiders are needed to make a 4in. coil feasible and why can't the 12 spoke handle it?

the 12 spoke can't handle a big enough spider.

 

[Seattle206 10+ year member]

so besides production costs and additional size and weight of motor(im assuming) the 4in. coil outdoes the 3in.?

 

[MEMPHISFLEX 10+ year member]

Your 4" coils will take more power than a 3" coil in most aplications, thats why some of your bigger spl subs have 4" coils, most daily/spl subs have 3" coils, a 4" coils is not nessasary in a everyday driver, and your 3" coils will take almost any power levels, the 4" coils is just a step better, but not needed!

 

[DJ Nitrous 427 10+ year member]

Look at your RE MT....3" coil...i forget who...sundownz I believe...posted a picture of an MT he had where the cone was destroyed but the coil still looked new...the coil took the power and outlasted the rest of the softparts...4" coils will absorb more heat but when the 3" coil outlasts the rest of the speaker...whats the use?

I've heard alot of different reasons why 4" coils aren't used too often. I head something about haveing alot of area inside the coil or something which resulted in a weaker motor than one that used a 3" or something...but the main thing is the suspension.

RE Destroyer vs. Concept CSP (same motors)

The Destroyer used an 8" spider because that is the largest the 12-spoke basket would fit, the CSP on the otherhand used a 6-spoke basket wich would accept a 10" spider. The 8" spiders are built for 3" coils and had to be cut to accomidate the 4" coil...this limited the ammount of travel the sub move, and also gave a less than perfect edge to be glued to the former

...subs that do use them..

TC5400, Cactus Sounds, Rockford T2, RD Audio SHW, Concept CSP/RE Destroyer, OLD Rockford Power HX2 and RFR-1812, RE MX and more that I can't think of right now

As far as bigger coils...I've heard PrecisionPower had a 5" coil and Audiobahn had a 6" at one time...just dont expect much travel out of them

 

[newusername 10+ year member]

Well, first we must make the distinction that just having a larger OD coil doesn't mean it has better power handling. If we assume the same winding height, number of windings, coil material, and convection cooling, a 4" coil will, indeed, handle more power. Otherwise, it may be a different story. It's a "sum of the parts" kinda thing.

Keeping with that same assumption....a 4" coil will have more moving mass. It will have more coil in the gap, increasing BL. Although slightly offset by the increase in mass, this results in higher efficiency. Although a larger diameter coil generally has lower inductance, a 4" coil with the same winding height will actually have higher inductance than an equivalent 3" coil because the winding length is higher. This generally means earlier rolloff on upper frequency response.

As mentioned above, the implementation of a larger OD coil has a challenge when integrating with the spider. A wider diameter coil means that, in a given basket, there is less spider area. This means that your stroke, particularly linear stroke, can be limited. You can minimize this by increasing the height of the corrugations in the spider, but you eventually need a wider diameter spider, meaning wider basket, meaning custom tooling, meaning $$$$. With large displacement systems, the suspension is almost always the limiting factor.

 

[snoopdan 5,000+ posts]

Here are some 4" coils I have lying around my office, just for some eye candy in this thread //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

Also notice that not all 4" coils stack up one against each other in windings/material.