W15gti used to make DIY 2269 clone

[OB-1]

Hi all, I have recently got my hands on a W15gti with a perished surround, as these are impossible to get parts for I was thinking about trying to cobble together the parts to make a 2269 copy (also impossible to get).
My plan was to use the W15gti magnet and attach it to a TC sounds 18 basket:
http://www.ebay.com.au/itm/18-TC-SOU...item1e797e9dac
I would then use the W15gti voice coil and a 2268 cone with a 10 inch spider firmness to be determined.
This would be used in a 3 way system
- Low 18 sealed bass
- Mid jbl 225ij
- High Beyma tpl150H
I have experience reconing speakers and have the skills and equipment to build what would be necessary.
It would be greatly appreciated if I could get some tips and opinions, along the way.

Thanks OB-1

[Mr. Widget]

I would say that those are deep and uncharted waters... Personally I prefer projects where I can predict the outcome before spending time and money, but if it is the journey you are after; Good Luck and keep us posted.

You might want to send a PM to forum member GordonW. He rarely posts here these days, but he may respond to your questions if you send him a note. He has jumped into the deep end more than a few times and may be able to offer useful cautions and tips.


Widget

[Lee in Montreal]

18" cone in a 15" basket might prove a challenge ;-)

[OB-1]

Thanks for the reply and suggestion widget,

I like a challenge, I did read that the cone / spider where beefed up in the 2269 to handle the excursion, it would be great if anybody could post a picture of there 2269
surround, cone, front and back with a look at the spider.
My thinking is to use the 2268 cone as it has a 3" voicecoil same as the w15gti. I have a 2268 and the cone on that when pushed by hand only moves in or out 1.0" so it would seem that the surround would need to be replaced with a m-roll with more excursion or a large half round.
As for the spider, because the w15gti voice coil is so long it might be prudent to use a double spider to help with excursion and to keep things aligned in the gap, feel free to offer suggestions for spider firmness.
Hopefully the efficiency will be around 96db.

[hlaari]

this is a interesting project!

are you sure at you can use 2268 cone?
that cone are much ligher than the W15gti/2256g cone and not as strong also


Ari

[OB-1]

this is a interesting project!

are you sure at you can use 2268 cone?
that cone are much ligher than the W15gti/2256g cone and not as strong also


Ari

the problem is getting a 18" cone with a 3" voice coil cut out which the 2268 cone does have.
The 2268 cone that I have is ridged enough to get a working prototype, after measurements this may indicate a change to a heavier more ridge cone. I can always add weight to the cone as well to see what happens to the parameters.
On the advice of a fellow member I have modelled the w15 gti magnet motor with TC sounds 18" basket voice coil and cone in 3d cad it looks like this will work.

[OB-1]

At last some progress has been made, ordered the parts and a Dats V2 measuring system and waited for them to show up.
While I was waiting for things to arrive I used bass box pro and modified the parameters for a w15gti with the 2268 cone sd and lighter weight to get a idea of what might happen.
Once all the parts arrived I got busy unfortunately in my hast I forgot to weigh the coil, cone and spider assembled, but the dats system does allow for this with added mass.
* This data was exported from the Dayton Audio Test System: DATS
*
* Manufacturer: NBF
* Model: W18GTI
D 400 [mm]
Re 3.02 [Ohms]
Fs 25.57 [Hz]
Zm 73.31 [Ohms]
BL 16.07 [N/A]
Qms 10.59
Qes 0.455
Qts 0.4362
Vas 355 [liters]
L10k 0.541 [mH]
n0 1.244 [%]
dBSPL 93.05 [1W/1m]
Ms 242 [grams]
Cms 0.16 [mm/N]

This is a huge beast as you can see from the tiny 2268 beside it, REW measurement has w18gti red +4db and 2268 green mic 1cm from cone free air no smoothing.
looking at the results what could be a suitable box for this, I'm open to suggestions

[OB-1]

attachments

[cpwfx]

Wow! That looks mighty impressive, well done! How does it sound?

[OB-1]

Thanks for your response. I have it in a 245Lt bass reflex box tuned to 30hz and another identical 245Lt box tuned to 30hz with the 2268.
The W18gti (as I am calling it) is noticeably lower and more powerful, although it could just be the box tuning. I was hoping someone with more experience might chime in with possible alignments using the DATS measurements.
Playing 20 hz tones with about 25mm one way excursion is no problem for this thing, I did modify the voice coil collar so that the old spider is removed and the new spider is 15mm down from the top of the voice coil.
It could now do a one way xmax of 40mm without damage (although the first coil which is 35mm would be out of the gap) this is off course providing the spider and surround could handle this much travel and I had a 5000w amp to drive it.
REW measurements show that like all differential drive units distortion is very low, in fact so good it makes me wonder if my measurements are accurate or if I am doing something wrong.