Purpose of Dome on Tweeter...


What is the purpose of the "Dome" on a dome tweeter? Will a dented or dimpled dome effect the sound dispersion coming from the tweeter? If not, why aren't they just pushed in at the factory? Better yet, if a dented dome doesn't effect the sound, it would seem as if it's a non important part in a tweeter so why not just build a tweeter without the dome at all?
b_limo
It depends on how the tweeter is designed. A lot of tweeter models will use the dome (dust cap) for dispersion. It also keeps dust and dirt out of the voice coil and motor assembly.

I get a chuckle out of some ads that have all of the dust caps pushed in and the owner states; "this doesn't affect the sound at all". Yeah, right.
Tweeters come in many types: Cone,Dome,Horn,Ribbon,Electrostatic,etc.
Why would the factory push in the Dome?
Would you buy a watch with no lens?
Like Mofi states,it's the design.
The dome of a dome tweeter is the diaphragm, the part that moves the air to create high frequency sound. It is driven by current moving through the voice coil which is in contact with the dome just behind it. Without the dome in place the voice coil itself would not be effective at moving enough air to make the sound level audible. The shape of the dome does affect its dispersion, so having a dent in it will affect its performance to some degree. There are soft and hard dome designs, and neither operates ideally as a perfect piston. At certain frequencies the dome will resonate, and its shape is important at those frequencies since breakup modes occur.
If not, why aren't they just pushed in at the factory?
That would be the inverted dome tweeter like Wilson Audio uses.
"03-13-15: Tls49

If not, why aren't they just pushed in at the factory?

That would be the inverted dome tweeter like Wilson Audio uses."

Its only inverted because they installed the tweeter backwards. Its a quality control issue.
Its only inverted because they installed the tweeter backwards. Its a quality control issue.
What? Are you serious or is that suppose to be a joke.

Focal also uses inverted dome tweeters, and you can see the differences in design here,

[url]http://www.focal.com/en/content/17-inverted-dome-tweeter[/url]
"Focal also uses inverted dome tweeters, and you can see the differences in design here,"

Wilson uses Focal tweeters.
"03-13-15: Tls49

If not, why aren't they just pushed in at the factory?

That would be the inverted dome tweeter like Wilson Audio uses."

I thought that was a joke. Pushing the domes in at the factory? How could it not be a joke?

Sorry Zd, slept late this morning, let's get another cup of coffee.

As far as jokes, the best one was what a wife of a potential speaker buyer said when the grill was removed exposing the woofer with a substantial phase plug,

"Oh, little boy speakers"

Myself and the rest of the guys were speechless.
I figured as much. Even I was joking when I was asking why they don't push the domes in from the factory; it was basically for those people who might respond that it has no effect on sound.

I figured that the dispersion would have to be changed when the domes are dimpled and halfway pushed in. I don't get why these sellers disclaim the nicks on the cabinets but say nothing about the dimpled and dented tweeters. I've actually read ads where the seller will claim that the speakers are in excellent shape besides the scuffed and scratched (and nicked) cabinets but I can clearly see that the tweeters look dented in. When I ask about the tweeters being dented the seller will respond that "yes, the tweeters are dimpled / dented but it in no way effects the sound"...

In another ad for a pair of unknown speakers with a mtm arrangement (dynaudio looking drivers) the seller states that he's an audiophile who's had many speakers but these are the best sounding speakers he's heard apart from a blown midrange driver.

I've got an incredible sports car for sale that runs great and is in excellent shape apart from the knocking motor and dents in the hood, doors and trunk. The roof is in nearly perfect condition and the torn seats are an easy fix. Buyer will have to tow the car because it currently won't start because of a dead battery which is an $80 fix and 10 minute repair that I just don't have time to do!
I do believe EPI had the first inverted dome tweeter that was not attached to a horn
The purpose of the dome shape is rigidity. Domes are very strong for their weight.

At frequencies where the dome is effectively rigid, the dispersion is essentially that of a piston of the same diameter. The dome shape does not improve dispersion in and of itself because it's not a pulsating dome, it's a moving-back-and-forth dome.

At frequencies where the dome is in breakup mode, the dispersion tends towards that of a ring radiator, with the diameter of the ring being the diameter of the voice coil. Some of the inverted dome tweeters have a voice coil that is smaller in diameter than the perimeter of the dome, and therefore have a little bit better dispersion when they go into breakup mode.

A pushed-in tweeter dome no longer has the geometric rigidity it was intended to have, and even if you manage to pop it back into shape, the material may have been weaked where it was creased and so its behavior may be degraded.

Duke
dealer/manufacturer/occasional user of dome tweeters
Duke,

Would there be an advantage to domed woofers?
"Would there be an advantage to domed woofers"?

If it gave the behavior the designer wanted, then yes.

My guess is that there would be a tradeoff, where the dome diaphragm is probably stiffer and remains pistonic to a higher frequency, but then has nastier behavior when breakup finally does set in, compared to a more traditional curvilinear cone. Few choices in loudspeaker design are without tradeoffs.

Morel and Dynaudio make woofers whose voice coils are quite large in diameter relative to their cone diameter, so they end up being quasi-dome woofers. Both companies also specialize in tweeters that can be crossed over unusually low, and this may be an adaptation to the characteristics of quasi-dome woofers made from paper or polymers.

I think Accuton uses a concave dome profile for their ceramic-diaphragm woofers, and this would be consistent with their philosophy of maintaining pistonic behavior as high up as possible. I think Cabasse used to make shallow-dome-profile honeycomb-sandwich woofer cones, but I don't know what material they used.

Duke
As Duke mentioned above, Dynaudio & Morel mid/bass drivers with 3 inch voice coils basically have a 3 inch dome type dust cap. I myself am a big fan of the 6 inch Morel doped paper cone. Great controlled bass from the 3 inch VC and that raised dome acts like a 3 inch dome midrange. Check out the ATC monitors, they also have raised dome dust caps.

Fritz, builder of FritzSpeakers
Speaking of domed woofers, has anyone else noticed how much the whizzer cone vibrates and buzzes? That's obviously due to higher frequencies that get in through the crossover filter. But has anyone tried to damp the woofer whizzer cone and prevent this rude distortion? I have. I used one of those little triple stacked discs Acoustic Disc thingies from Golden Sound. Surprisingly efficacious.
Addendum. I meant dust cap not whizzer cone. Oopsy daisy. It's the dust cap on woofers that buzzes and vibrates.
Duke Fostex Foster made a dome 10 inch woofer FF7