Smallest tweeter available?

[Ed LaFontaine]

I'm looking for tweeters which allow center to center spacing on the order of ~2 cm.
Are there any such as might be found in laptop computers that would meet this?

[dave_gerecke]

Hello Ed, did you happen to see Parts Express SKU 264-841?

Peace,

Dave

[Ed LaFontaine]

Dave,

I had not. The fs of 4K is a killer, though.
I've heard of drivers which are installed in laptops which have a ~500 hz fs. That would be the ticket. I'm trying to find a source for them.

[Pano]

Maybe Don Keele can get you some of those he uses. You can always ask.
I think I heard the P.E. crew talking about carrying them. So maybe...

[Andrew Eckhardt]

Projects Unlimited, CUI, and of course Tang Band make mini speakers. If you want a tweeter that small that goes down that low, you're probably looking for a mini/laptop speaker. PE has the 3/4" listed in "extended range",

http://www.parts-express.com/pe/show...number=264-882

Most of them are not so flat.

[chris661]

AUTOMOTIVE TWEETERS from Parts Express ship same day and come with 45 day money back guarantee. Free Shipping Available. Order free 10,000 product catalog.

Seems like what you're after.

[sreten]

Originally Posted by Ed LaFontaine

Dave,

I had not. The fs of 4K is a killer, though.
I've heard of drivers which are installed in laptops which have a ~500 hz fs. That would be the ticket. I'm trying to find a source for them.

Hi,

The laptop drivers due to the Fs will have pathetic sensistivity and output.
See the HiVi B1S here : Zaph|Audio
Use in multiples will solve both problems but your heading towards line arrays.

High Fs is part and parcel of very small tweeters, it typically allows 3rd
order rolloffs with a single capacitor, or 4th order with an added inductor.
It makes the c/o far cheaper to implement for correct power handling,
to be more correct for avoiding distortion due to overexcursion low down.

If you want a lot of them Apex Jr do a nice Audax made
(the best) mini tweeter for $1 each or $85 for a 100,
It allows very tight spacing, Fs I'd say around 2KHz.

/Sreten.

[Andrew Eckhardt]

Alright. I grabbed a Dayton ND20FA and bored a 13/64" hole in the center of the magnet structure, then ran a countersink a little more than halfway into the pole material on both sides. I had to completely disassemble the tweeter to get it done. Put it back together, after quite a gap cleaning job, and with the bottom of the tweeter suspended off the bench with some blocks I got 575 Hz resonant frequency.

This is something I've been wanting to do on my own anyway..

I also got a chance to seriously inspect the construction. I noticed the coil former was not glued quite colinear with suspension travel, in hifi terms you could call it way off.

A simple plug is probably cheaper than a cylinder magnet, possibly the reason for using the former aside from the fact that it wasn't to be a vented design anyway. The pole material, judging by leakage, is still highly saturated and the removal of a small volume of material in the center probably will not reduce gap flux very much. The gap is pretty large, probably too large to run without ferrofluid. I didn't measure.

Long story short, you might be looking for a vented neo tweeter. I've never seen one so can't recommend any production models. The ND20FA could be redesigned with one but maybe the lead wires would have to come off the coil more at a tangent than somewhat perpendicular as they do. They are tinsel at least. Power handling would be further limited. Ferrofluid wont help trying to hit minimum Fs. Of course lower Fs means less efficiency.

[planet10]

Originally Posted by sreten

If you want a lot of them Apex Jr do a nice Audax made
(the best) mini tweeter for $1 each or $85 for a 100,
It allows very tight spacing, Fs I'd say around 2KHz.

That tweeter has to be one of the bargains of the century... it can outperform units 10x the cost. (reminds me that i need to get another batch -- i've gone thru probably 100 so far).

It is hard to say where the Fs of this tweeter actually is, as the ferrofluid seems to be removing any hint of an impedance spike (see attachment). Limitations are excursion limited... i usually XOed them (singly) at 10k + 1st order, but there is more to be had down low i'm sure.

dave

[Andrew Eckhardt]

I was thinking maybe Ed had an actual application for a 500 Hz Fs tweeter at around 20mm diameter. You'll never get one of those little mylar tweeters to resonate that low unless you drill a bunch of holes around the suspension and then it will probably have severely limited excursion capability.

FWIW I replaced the ferrofluid with whatever grade it is that I have and the Fs didn't move much at all, it's just much lower Q.

I doubt it would be very linear for much drive level in the ~1kHz range, if that's the idea. By eye the coil seems to be about as tall as the gap. It would be impossible to actually measure this without total destruction.

The OD of the diaphram frame, which can't reasonably be minimized, is about 30mm.

If 20mm is a more critical design driver you could possibly start with the 5/8" dome. Though if you need more than 2 I don't think modification would be the way to go.