# Custom Neo 8" w/ 3" Coil



## HiloDB1 (Feb 25, 2011)

Well I have this posted on another forum but there seems to be little interest in my build. So I'm going to post up what I have here and see what stirs up.

Here is whats going on.

Motor is a custom job that I got a while back only 2 were produced (I did not design/build them I bought them from a manufacturer). Its built with 1010 steel and has 9 1"x1"x2" columns of N42 NeFb between the top and back plates.










I did a model of the motor in FEMM for fun 










Looks pretty good 

Coils are a 4 layer round aluminum wire affair. Dual 4 ohm nominal (2.7 DCR). They are actually PG Ti12D Elite coils.










Spiders are from Sundown Audio SA-8 V.2. I was told by Jacob that he has tested them at 1" linear each way.










Also made adapters/spacers for the basket. I needed a little extra space for clearance reasons and also to match bolt patterns from basket to motor.










Also made a few other parts to go with this build. In this picture the part is white.










And in this picture its now black . Took a while for it to take the dye to the point where the color was ok with me.










So this is where the project stands right now. All parts are made and ready for assembly. Just need to finish cleaning up the motors and painting. Weather here has been raining so its not an ideal time to paint. I'm hoping for a few days of sun so I can have them done :worried:. Need to sew the tinsels to the spiders and cut my voice coil formers to length. Couple other small items that need to be worked out but its close.

I took some measurements and did some math and looks like Ill be around 25mm linear Xmax (WW-TP/2) and have about 32mm Xmech before it destroys itself  give or take a few mm. At that point the coil will be out of the gap anyway so I'm not too worried.

If there is interest I will continue to update this thread as progress is made. Otherwise I will let it die like the other one


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## Infinity (Jun 28, 2005)

What kind of T/S are you expecting?


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## HiloDB1 (Feb 25, 2011)

Infinity said:


> What kind of T/S are you expecting?


This is still kind of up in the air at the moment. All depends on the spider pack I use. I know my Mms is going to be high for an 8" as there is a lot of stuff going on with the reducer for the coil and the collars for the spiders and cone. If I go with my original plan Id probably end up with a low Fs but I may decide to go with a stiffer spider pack and make it more SPL oriented.


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## Infinity (Jun 28, 2005)

See, I was thinking low Fs monster, just because that's my personal preference in a sub. I ALWAYS use substantial midbass. Looks like a fun project to me


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## HiloDB1 (Feb 25, 2011)

Decided to go with a slightly stiffer spider pack. So expecting Fs in the mid 40's before break in. Went with the higher Fs due to the enclosure I'm going to put it in. More oriented towards SPL but still capable of some low end output.



















Motors aren't perfect but oh well


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## Inferno333 (Mar 29, 2006)

Still looking sharp bud.


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## HiloDB1 (Feb 25, 2011)

So they are alive 

After a short break in.

* f(s)= 40.37 Hz
* R(e)= 1.47 Ohms
* Z(max)= 20.41 Ohms
* Q(ms)= 5.105
* Q(es)= 0.397
* Q(ts)= 0.368
* V(as)= 9.269 liters (0.327 cubic feet)
* L(e)= 1.59 mH
* n(0)= 0.15 %
* SPL= 83.76 1W/1m
* M(ms)= 135.10 grams
* C(ms)= 0.12 mm/N
* BL= 11.27 

* f(s)= 39.03 Hz
* R(e)= 1.56 Ohms
* Z(max)= 20.71 Ohms
* Q(ms)= 4.575
* Q(es)= 0.373
* Q(ts)= 0.345
* V(as)= 6.317 liters (0.223 cubic feet)
* L(e)= 1.56 mH
* n(0)= 0.10 %
* SPL= 81.92 1W/1m
* M(ms)= 212.00 grams
* C(ms)= 0.08 mm/N
* BL= 14.76

Not sure why the large BL difference but I think it has to do with one not having the coil perfectly aligned. There is some mechanical noise in that driver, well more than the other one anyway. These both make a lot of mechanical noise once they start moving 25mm one way 

Sorry but no pics ATM or vids. Going to keep this hush hush until after the 21st as there is a comp. Ill be posting up some numbers though when I get some time to do some testing.


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## cajunner (Apr 13, 2007)

funny how the stronger motor is almost 2 db less efficient and how you have 78 grams difference in Mms.


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## HiloDB1 (Feb 25, 2011)

Pretty sure all the anomalies are due to the coil misalignment.


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## mrazandrewm (Feb 28, 2011)

Any update. Would like to read up on how to make a custom subwoofer. Would be a fun side project to do.


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