E145 air gap / voice coil dimensions

[jerv]

Do anyone know the depth of the air gap and the height of the voice coil winding in the E145 driver?

[Lee in Montreal]

Do anyone know the depth of the air gap and the height of the voice coil winding in the E145 driver?

Isn't it the same as the 2225 and 2235? If so, I am pretty sure it is very well documented on this forum.

[ratitifb]

Isn't it the same as the 2225 and 2235?

The magnetic motor of the E145 is oversized compared to other JBL 15" drivers and was based on LE15H with its underhung coil topology while the 2235H is based on an overhung design.

2235 VC compared to E145 VC

Do anyone know the height of the voice coil winding in the E145 driver?

Regarding the gap (from DD55000 Tech Doc) :



Unfortunately the gap depth but Xmax is 7mm with its underhung coil design

and generaly speaking the top-plate thickness of the underhung motor is longer than the voice coil by a factor of 1.8.

[jerv]

Unfortunately the gap depth but Xmax is 7mm with its underhung coil design
and generaly speaking the top-plate thickness of the underhung motor is longer than the voice coil by a factor of 1.8.

Excellent. After some searching, I found data on gap depth in this old post: http://www.audioheritage.org/vbullet...ull=1#post4549

Then, according to my arithmetics, the VC height is 7,4 mm and the gap depth is 15,1 mm. What I then don't understand, is the specified Xmax of 7 mm. Shouldn't it be more like 3,8 mm: (Gap depth - VC height) / 2 ?

[ratitifb]

coil height is 7.4mm and Xmax is 7mm so top plate thickness should be 21.4 mm

[1audiohack]

In the transducer list the coil length is stated as 0.290"

With a stated Xmax of 0.280" I would guess the top plate to be 0.570", I thought the plate was 0.500" like the 2220 but in a 2003 thread titled Gaps and Depths (copied below) subwoof has listed the top plate thicknesses of the E145 and 2220 as ≈0.593"

Edit: To give credit where credit is due, the information below is a gift from subwoof, thanks buddy!

The list - gaps and all..

OK guys - here is the accumulated info...A few caveats:

(1) measurements were made in a dusty woodshop with an old set of ( now magnetized ) calipers
(2) Some variations of magnet structures ( bolt thru vs plate screws ) *might* be found.
(3) MOST magnets have a casting number that may or may not match others?? I'd bet JBL would know...
(4) JBL has a "goes into" checklist that applies to 10% of their items so use with a grain of salt...
(5) Some magnet structures use a thicker ring of ferrite - these WILL allow longer excursion ( wow - a whole 1/16 in.... )
(6) The earlier Alnico magnetic gap depths are the same as the ferrite if the model number is the same.
(7) Some variations of magnetic intensity are found in the published JBL literature - no attempt was made to confirm.
(8) The vented gap types are in a different league - NOT interchangeable.
(9) There are TOO MANY variations of magnets + cones on the smaller / consumer sizes so little info was compiled
(10) The 18 ferrite magnet structures are larger in diameter than the others
(110 Yeah I probably missed a bunch but I needs da sleep...

MODEL NUMBER GAP DEPTH FERRITE THICKNESS

E120 / 130 / 140 9 / 32 7 / 8
E145 19 / 32 7 / 8
E155 / 2240 / 2245 11 / 32 7 / 8
2220 11 / 32 3 / 4

2205 / 2230 / 2231
2135 / 2202 / 2130
2203 / 2204 / 2234
2235 / LE14H / etc 9 / 32 3 / 4
( most common type by far )

sub

[Eaulive]

Excellent. After some searching, I found data on gap depth in this old post: http://www.audioheritage.org/vbullet...ull=1#post4549

Then, according to my arithmetics, the VC height is 7,4 mm and the gap depth is 15,1 mm. What I then don't understand, is the specified Xmax of 7 mm. Shouldn't it be more like 3,8 mm: (Gap depth - VC height) / 2 ?

15.1mm - 7.4mm = 7.7mm Xmax. That's the total value of the displacement. If you measure the displacement from the resting point towards both directions, you will have +/- 3.8mm, yes.

[ratitifb]

15.1mm - 7.4mm = 7.7mm Xmax. That's the total value of the displacement. If you measure the displacement from the resting point towards both directions, you will have +/- 3.8mm, yes.

according to JBL tech doc http://www.jblproservice.com/pdf/thi...parameters.pdf

and the definition of Xmax JBL has written is the following "Xmax is the peak linear displacement" (not peak to peak)

The E145 Xmax is 7,1mm peak

[ivica]

Excellent. After some searching, I found data on gap depth in this old post: http://www.audioheritage.org/vbullet...ull=1#post4549

Then, according to my arithmetics, the VC height is 7,4 mm and the gap depth is 15,1 mm. What I then don't understand, is the specified Xmax of 7 mm. Shouldn't it be more like 3,8 mm: (Gap depth - VC height) / 2 ?

I believe that mentioned 3.8mm corresponds to the very low distortion on one side, and on another side there is some amount of magnetic flux (I think about 15% ~20% of total) that is out of the gap, so it cab be "used" for almost linear coil movement, and third there is some amount of non-linearity that is acceptable, that are influenced by lower magnetic flux (a kind of 'movements saturation'), so I believe that all are the reasons that Xmax is different then suggested formula : Xmax=(Gap depth - VC height) / 2

[Eaulive]

according to JBL tech doc http://www.jblproservice.com/pdf/thi...parameters.pdf

and the definition of Xmax JBL has written is the following "Xmax is the peak linear displacement" (not peak to peak)

True, I was tired yesterday apparently

But if we follow this logic, the E145 should have an Xmax of 3.8mm since it has a VC of 7.4mm and a top plate of 15mm according to 1audioshack.