W5-1611SA - not underhung? - diyAudio
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Old 20th October 2012, 08:13 PM   #1
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Default W5-1611SA - not underhung?

According to the data sheet, this driver has an underhung motor with 10 mm gap depth. The x-max is given as 3 mm, so the coil should be 4 mm in height.

However, I have just acquired a pair of these drivers, and the top end of the coil definitely sits a few mm (2-3?) above the top plate. The spider is perfectly flat, so this is not a driver the suspension of which has deformed in storage.

What's going on here?
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Old 20th October 2012, 08:37 PM   #2
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are both drivers identical? if yes then just listen
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Old 21st October 2012, 02:34 AM   #3
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Default TB 1611sa

Quote:
Originally Posted by capslock View Post
According to the data sheet, this driver has an underhung motor with 10 mm gap depth. The x-max is given as 3 mm, so the coil should be 4 mm in height.

However, I have just acquired a pair of these drivers, and the top end of the coil definitely sits a few mm (2-3?) above the top plate. The spider is perfectly flat, so this is not a driver the suspension of which has deformed in storage.What's going on here?
Hi there: (Lvc-Gair)/2=Xm, (Lvc-10)/2=3mm, Lvc=16mm, Looked at one of my TB 1611sa, and I'm not sure that the position of the Vc with regard to the top plate is visable. Yes the spider is flat. Both of these sound excelent and do require some hours of brake-in..... regards, Michael

Last edited by j.michael droke; 21st October 2012 at 02:39 AM. Reason: added calculation
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Old 21st October 2012, 06:12 AM   #4
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Michael, do you have a data sheet that states 16 mm Lvc?

The one I have states heigt of gap 10 mm, xmax = 3 mm but not explicitly the length of the coil. It does say its underhung though, so out of the two possible solutions, it should be 4 rather than 16 mm.

I can move the coil completely out of the gap, and it is definitely not 16 mm long.

I am just trying to figure out if my drivers are from a malassembled batch...
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Old 21st October 2012, 11:09 AM   #5
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Ok, I have taken some pics. The first one shows the voice coil in its rest position. I have inserted a 2 mm hex key for comparison. The top plate has a bevel, so the top of the voice coil extends only 0.5-1 mm above the top plate (but about 2 mm above the lower end of the bevel).

The second picture shows the voice coil with the cone pushed up (out). One can actually push the cone a little further (maybe half a mm vs. the picture) to see the lower end of the coil leave the gap. I just couldn't push hard and take a picture at the same time.

The coil is roughly 4 mm in length, seems to consist of three or rather four layers, and is missing the last few turns of the topmost layer. I have seen a similar coil in the Peerless CSC217 driver where it serves to symmetrize the Bxl(x) curve.

Now the edge of the top plate is covered by the basket, and with the heat sink firmly glued to the motor, it is difficult to measure its thickness. There is no way it is 10 mm high, more like 3 mm. It is theoretically possible that the top plate consists of two parts, and there is a smaller diameter portion insided the motor assembly - there is simply no way to tell with the heat sink in place.

So this leaves to possibilities:

1. The gap is really 10 mm high (i.e. there is another 7 mm attached below the large diameter part) as the data sheet states. Then there must have been a mistake in assembling this driver, and the coil has an offset about 4 mm.

2. The top plate is really 3 or 4 mm thick, but the motor is of a highly unconventional design, such as no iron pole piece but two neo disks of opposing polarity in its place. The results in HobbyHifi are excellent (probably lowest distortion of any 5 in. driver, with the exception of a few second harmonic peaks that seem to be due to cone modes). There is no problem with stating the coil is 4 mm high (which they don't) and determining the xmax from the Bxl curve. However to state the motor is underhung and the gap is 10 mm high is stretching the border of creative marketing...
Attached Images
File Type: jpg w5-1611_rest_pos.jpg (88.3 KB, 127 views)
File Type: jpg W5-1611_coil_out.jpg (98.5 KB, 129 views)
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Old 23rd October 2012, 04:28 AM   #6
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Default TB 1611sa

Quote:
Originally Posted by capslock View Post
Michael, do you have a data sheet that states 16 mm Lvc?

The one I have states heigt of gap 10 mm, xmax = 3 mm but not explicitly the length of the coil. It does say its underhung though, so out of the two possible solutions, it should be 4 rather than 16 mm.I can move the coil completely out of the gap, and it is definitely not 16 mm long.I am just trying to figure out if my drivers are from a malassembled batch...
Hi there: Negative, data sheet I downloaded states "air gap" is 10mm, Xm=3mm. Your examination (4mm coil) indicates that the coil is not overhung. ....regards, Michael
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Old 26th November 2012, 10:24 AM   #7
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Quote:
Originally Posted by j.michael droke View Post
Hi there: Negative, data sheet I downloaded states "air gap" is 10mm, Xm=3mm. Your examination (4mm coil) indicates that the coil is not overhung. ....regards, Michael
But why is the top end then sticking out by at least 0.5 mm in rest position? Two Possible explanations:

1. Top plate is really only 3 mm thick (maybe in combination with a super-extended pole piece, but I wouldn't call that a 10 mm gap).

2. Voice coil rest position is mal-centered by a full 3.5 mm!
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