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Old 14th February 2003, 02:00 AM   #1
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Default driver modifications to double the excursion

I have two pyramid 1295's which are basicaly ugly cheap car subwoofers which were good for a first learning experience on designing out a ported box and building it, but are realy crappy for any sort of listening. I was considering the idea of taking them apart as gently as I could, and then using the two magnets and pole pieces and welding / gluing them together, and then using one voice coil mounted in the middle of this double length magnetic field in order to have a muich longer linear excursion range. I figure the paper pulp cone, foam surround, plastic dust cap, etc are all pretty much trashable. Then using this new asembly and prob the 2nd voilce coil as a spacer mount a new smaller cone with a bycicle inner tube as a big surround , and maybe do a double surround like mentioned in the pasive radiator thread in order to get arond the issue of a spyder to handle that excursion. Does this sound at all possible to anyone or a complete waste of time to even attempt? I dont care if it is "musical" or very accurate, Im mainly interested in this as a project since it is nearly free and the coolness factor f I can create something with incredible excursion capabilities.
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Old 14th February 2003, 12:09 PM   #2
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As nobody else seems to want to answer, i'll start.

It sounds to me like a waste of time to attempt. I cant see it working full stop.

Having said that, I have taken on some stupid/impossible projects myself in the past so If you feel that you want to try anyway then go for it. You have nothnig to lose except some crap drivers and time. And you are bound to learn a little (or a lot) which will be of future benefit.

If you do try, let us know how it goes.
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Old 14th February 2003, 02:22 PM   #3
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do you mind elaborating as to why you think it would not work?? Like are parts of it sound but has somehting glaring that I could alter maybe?
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Old 14th February 2003, 03:09 PM   #4
JBL is offline JBL  Canada
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Designing and building a speaker is no simple task. Their is a critical balance between mechanical and electrical caracteristic affecte by an infinite number of factor. By modifing a driver you will probably not get satisfactory result and any imperfection will greatly reflect in the final sound.
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Old 14th February 2003, 03:40 PM   #5
Bobken is offline Bobken  United Kingdom
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Hi,

Unless your existing arrangement is already excursion-limited due to weak magnets i.e. nowhere near 'hits the end stops', I don't think you have much to gain here. There is only so much extension any driver will accomodate for due to the cone, surround and depth of gap etc., and trying to exceed this is likely to give rather poor results, I would guess.

However, as has already been said, if you are only doing it out of curiosity, there is little to lose, but you may have a job lining up the annular rings within which the voice coil resides and moves, depending on how close tolerances they are.
Any misalignment here will produce some odd results, and a lot of unwanted scraping noises!

Finally, I wouldn't try your welding suggestion, as (most) magnets don't like heat very much, and you can destroy (or at least substantially reduce) the magnetism with a lot of heat.

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Old 14th February 2003, 06:32 PM   #6
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Default 28 inch woofers :-)

How about leaving your drivers intact but adding a *much* larger cone? The existing roll surround would be like a secondary spider and you could use your rubber bicycle tube as your new surround as you suggested. Still some tricky mechanical issues but you are much more likely to have some measure of success (and fun) if you don't pull the magnet and coil assembly apart. Let us know how you go if you decide this way.


/Circlotron - plants seed of idea in someone else's head so they do the hard work of his experiment.
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Old 14th February 2003, 06:40 PM   #7
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Default 28 inch woofers :-)

How about leaving your drivers intact but adding a *much* larger cone? The existing roll surround would be like a secondary spider and you could use your rubber bicycle tube as your new surround as you suggested. Still some tricky mechanical issues but you are much more likely to have some measure of success (and fun) if you don't pull the magnet and coil assembly apart. Let us know how you go if you decide this way.


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Old 14th February 2003, 07:19 PM   #8
Bull is offline Bull  United Kingdom
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Taking apart a absolute crap speaker completely,will distroy it.
And there's no point re-coning some crap make of speaker.

A lot of car audio subwoofers are poor quality,except a few which i like[but are expensive] [JL Audio,Rockford Fosgate,Atomic,Focal,Fusion,and the more expensive Pioneer]

A could just carefully cut away the foam or rubber surround on the awful woofers.But the way to get the most excersion is longer voice coil,deep double dampener,and very thick ,very flexible rubber.But i guess the voice coil former on your really cheap and nasty speaker drivers,won't take much physical or themal abuse,if you modify it.

I've only modifyed one odd speaker,but not the surround,but the dustcap[because it was badly torn].

I advice you to sell the pair of these subwoofers,depending on whether they don't buzz[ don't distort on bass notes],and get 1 better subwoofer.
The advice for bigger excersion is measured in Xmax and X Mech,if you don't have a clue what i'm talking about;then look for maximum linear excersion when buying some new or 2nd hand drivers.If maximum linear excersion is not printed on the speaker packaging,then at least a speaker with a deep basket[deep frame] and thick large surround [or cone edge].A speaker having more excersion peak to peak than the other doesn't make it a better sounding speaker,but the more excersion the speaker can handle the more mechanical abuse it can take.
A speaker that can take a lot of thermal abuse has a big voice coil 4 inch diameter,kapton coil former,vented pole piece,high temperature copper voice coil which is made of thicker copper wire.
A combination of both these makes a good strong subwoofer,but it still can sound unnatural and have a more limited frequency
range.
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Old 14th February 2003, 07:39 PM   #9
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Quote:
Originally posted by Bull
And there's no point re-coning some crap make of speaker.
FWIW, I meant leave the existing cone etc. in place and simply extend it to a greater diameter with some suitable material. The results won't be as certain as simply buying a different driver, but it is grass-roots diy. You'll learn more too.
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Old 14th February 2003, 09:50 PM   #10
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Jared

I would go with Circlotron's idea, sounds like fun.

You will need to think of a way of extending the basket though, as the driver will need suppport around the edge. Maybe that's where your welding skills could come in!
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