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MRV
12-16-1998, 09:00 PM
Is there a difference between a 25oz. magnet to a 100oz. magnet for example besides size and weight?

Is Bigger Better?????

JAYZ
12-17-1998, 12:24 AM
yes a bigger magnet is a lot better. it moves the cone easier but also requires more power. my RF 10" DVC has a huge magnet it is almost the size of the sub, and its loud too.

MTXGMC
12-17-1998, 12:34 AM
Its a matter of opinion . A big magnet doesn't always make a good speaker.
Ex. My 2 12" MTX Black Golds w/60oz. mags can out blast 4 12"JL w-6 with something like a 110oz. Mag useing the same amp!!!!!!!
Some speakers are just desiged better!!

big K
12-17-1998, 02:16 AM
Whoah there slammin on different subs.....they are made different for a reason. The W6 and RF DVC have massive magnets b/c their cone weighs prolly 4times that of your MTX's. The bigger thicker stronger magnet yeilds a stronger motor structure to move the heavier cone which makes more solid sound and better SQ..less cone flex. Also when the magnets are deeper, it usually means the sub has a deeper linear xmax which is very important since the amount of sound is that of which what you get when you do the math between cone size/weight and xmax. I'm not dissing MTX in any way, but saying that yes JL W6 subs are very ineffecient but very good sounding when powered properly. I personally use 4 JL10W6's in a common sealed enclosure and love them but I want an even better sub with an even bigger magnet structure, and the cone is much heavier than that of the W6 too. Just my $.02.

big K
12-17-1998, 02:16 AM
Whoah there slammin on different subs.....they are made different for a reason. The W6 and RF DVC have massive magnets b/c their cone weighs prolly 4times that of your MTX's. The bigger thicker stronger magnet yeilds a stronger motor structure to move the heavier cone which makes more solid sound and better SQ..less cone flex. Also when the magnets are deeper, it usually means the sub has a deeper linear xmax which is very important since the amount of sound is that of which what you get when you do the math between cone size/weight and xmax. I'm not dissing MTX in any way, but saying that yes JL W6 subs are very ineffecient but very good sounding when powered properly. I personally use 4 JL10W6's in a common sealed enclosure and love them but I want an even better sub with an even bigger magnet structure, and the cone is much heavier than that of the W6 too. Just my $.02.

175DB
12-17-1998, 02:35 AM
Magnet size does not make any difference. It all depends on what the magnet is made out of. I know subs with 75oz magnets that are 800watts rms. I also know of subs with over 100oz magnets that are only 350 watts rms. Don't judge a sub by the size of it's magnet. Use it's magnet size as a tool to figure out where you can mount it. I have a box that is built only three inches back from the sub but is the width of my whole trunk (big trunk too). I used the magnet size to give me an idea of how far back the sub reaches and how much trunk space I was going to have to lose.

Mr Bentwrench
12-17-1998, 03:09 AM
What the magnet is made out of hits it right on the head. Reguardless of size and material, the motor's stregnth is listed in the specs as "Bl" (in the Tesla scale for force/current... I think)

Warbleed
12-18-1998, 01:49 AM
Which is why a huge ferrite magnet wouldn't be as good as a rather modest neodymium magnet, but the neo is more expesnive, and usually considered too expensive for subs.

Mr Bentwrench
12-18-1998, 06:22 AM
Check the Bl. It has just as much to do with the windings. Its just a motor.

Mr Bentwrench
12-18-1998, 06:36 AM
Of course the motor must move the cone mass (Mms, in grams) and overcome the speakers compliane (Cms, in mm/newton). ****, JL won't even list their sensitivity!

mfr
12-18-1998, 05:49 PM
What really matters is "motor strength", which depends on the size and quality of the magnet. Speakers with high motor strength tend to have low Qts values.

The bottom line is that you should be looking for good T/S parameters (fs, Qts, Vas), NOT big magnets or even high motor strength.

How do you look for good T/S parameters? Here's an exerpt from the CAR STEREO COOKBOOK (pp 77-79) on that subject:
=============================================
INTRODUCTION TO T/S PARAMETERS
When you want to compare the bass response potential of various drivers (or
later, design a subwoofer box), there are three magic numbers which tell you
everything you need to know about a driver. These are called the Thiele/Small,
or T/S, parameters.

T/S parameters are normally provided in mail order catalogs or printed right on
the box in stores. If you can't find them, ask the retailer - you can't do anything
without them. The table below lists the T/S parameters:

T/S parameter units meaning
fs Hz resonant frequency of driver
Qts - total Q at the resonant frequency
Vas ft3
(see note below) volume of air having the same
compliance as driver
Note: Some manufacturers provide Vas in liters rather than ft3. Divide
the number of liters by 28.3 to convert to ft3.

The problem with T/S parameters is that they don't tell you much in their raw
form. You need to use your calculator or computer to do something useful with
them.

COMPARING WOOFERS FOR SEALED, PORTED AND BANDPASS
APPLICATIONS
To compare woofers for sealed, ported and bandpass applications, here's the
calculation you need to perform:



Ffb indicates how low the bass response would be for that driver in a reference-
size evaluation box. (Lower numbers are better.) Suppose you are trying to
decide between the following two 10" subwoofers:

model fs Qts Vas
Ultimate AU1050 29 Hz .43 3.50 ft3
Jensen JSW104 31.3 Hz .40 2.40 ft3

Calculating ffb for each driver provides the following results:

model ffb
Ultimate AU1050 54.3
Jensen JSW104 48.5

This shows that the Jensen driver provides bass response which is about ten
percent lower than the Ultimate driver. (This would come as a big surprise if you
used fs to judge bass potential.) This holds true regardless of what the box
volume is, so long as you are comparing both drivers using the same box
volume. This simple calculation lets you compare woofers without knowing the
size or type of your box.

If you know your box size and type, the actual cutoff frequencies for sealed and
ported systems can be estimated using these equations:

sealed box

ported box

where f3 is the cutoff frequency
and Vb is the box volume in ft3

These equations show that a larger box provides a lower cutoff frequency.
Furthermore, it takes a box which is four times larger to lower the cutoff
frequency by a factor of two. Suppose you have space for a 0.75 ft3 box behind
the seat of your truck and you have chosen to use a sealed box. The
approximate cutoff frequencies for the above subwoofers would be:


model cutoff frequency in
0.75 ft3 sealed box
Ultimate AU1050 50.1 Hz
Jensen JSW104 44.8 Hz

Tip: Avoid drivers with unusually high Qts values - anything above 0.8 is too high.
High values are caused by undersized magnet structures and usually result in
frequency responses with a large resonant peak.

mfr
12-18-1998, 05:51 PM
sorry, the tables didn't come out right