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Multi-Way Conventional loudspeakers with crossovers

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Old 13th February 2009, 06:38 AM   #21
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Default Missing attachments Fig1

It seems that only the last of the series of 6 images I tried to attach to the last posting actually were attached. I will do them one at a time here, starting with #1.
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Old 13th February 2009, 06:38 AM   #22
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Default Missing Fig2

Fig2
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Old 13th February 2009, 06:38 AM   #23
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Default Missing Fig3

Fig3
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Old 13th February 2009, 06:38 AM   #24
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Default Missing Fig4

Fig4
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Old 13th February 2009, 06:38 AM   #25
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Default Missing Fig5

Fig5

There has to be a better way. ;^)
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Old 13th February 2009, 06:47 AM   #26
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Default You have to be careful

don,t tweek the disk and also the dampening device has to be correctly cut for it will affect the frequency range by how much you restrict the disk
they have to have a certain amount of room to freely move I would suggest to go to ebay and find some D25NC-55-06 DOME TWEETERS! for there have been a bunch suddenly out there and they are a very good deal I bought some
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Old 13th February 2009, 06:52 AM   #27
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Default simple way too simple but way too good for inside

you are now see why people do like using them indoors they are just way too bright and hard to tame due to the very small area to work with or to modify
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Old 13th February 2009, 07:23 AM   #28
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As to the underlying piezo principle in the speaker operation, this is very similar to the 'electronic' igniters you see in butane lighters and other places.

In this case, you flex a ceramic crystal, and it produces electricity, as in an igniter spark.

But they work exactly the opposite as well. Instead of flexing the crystal to produce electricity, you apply electricity and it flexes the crystal. Flex it fast enough, and connect the crystal to a diaphragm, and sound comes out.

I think that is the underlying principle in a nutshell.

Steve/bluewizard
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Old 13th February 2009, 11:26 AM   #29
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Quote:
All I/we need to complete the picture is knowing how that motion is transferred to the diaphragm. I took some pictures of the unit as I was taking it apart and made these 6 figures to refer to.
It is actually the disc's inertia that is responible for mechanically coupling (maybe "grounding" would be a good expression) the bending motion to the diaphragm.

This is building some sort of mechanical highpass and therefore it is possible (though not advisible in the interest of good sound) to use this drivers without an electrical crossover.
The second mechanical highpass in this tweeters is the horn of course.

Regards

Charles
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Old 13th February 2009, 02:24 PM   #30
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Quote:
Originally posted by phase_accurate


It is actually the disc's inertia that is responible for mechanically coupling (maybe "grounding" would be a good expression) the bending motion to the diaphragm.

This is building some sort of mechanical highpass and therefore it is possible (though not advisible in the interest of good sound) to use this drivers without an electrical crossover.
The second mechanical highpass in this tweeters is the horn of course.

Regards

Charles

Yes, it appears to be simply the disk's inertia that works against the diaphragm. In fact I found that you get the same level of sound out of the horn by simply rubbing your finger about on the back of the bimorph disk. So, I do not think the diaphragm really moves in and out at all. Rather it just vibrates like a tin can does with a tuning fork placed against it. Which would mean that the timbre of the sound would greatly depend on the material the diaphragm is made of. And it would explain why this device can work with such a small gap between the diaphragm and the cone on the back of the horn.

As for what this means for the DIY tweaker, I would say that mods to the stiffness and dampness of the diaphragm material itself would pay off the most. And probably mods intended to reduce reflected sound from the rear chamber would be worthwhile. The ENAbl patterning still seems applicable as well. Anything that touches the disk to try and control or damp larger motions would have to be done with great care to avoid adverse effects on sound quality. Something light and rubber which touches only the rim of the disk might make sense to try, but it would have to be mounted in a "neutral" fashion. Meaning it should not press the disk in either direction, forward or backward. It would have to allow the disk center to vibrate freely while a signal is applied but help kill the vibration quickly when the signal ends.

Oh, thanks mcmahon48 for the tip about the D25NC-55-06 domes on E-Bay. I will have a look at that.
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