Dome tweeter evolution

[davidsrsb]

I have noticed that many two way speakers now use 28mm soft dome tweeters.
Not that long ago 25mm was the norm and at one time even 19mm was seen on two way designs. 19mm was probably not a good idea, the crossover was going to be problematic for both the midbass and the tweeter.

28mm obviously allows a better integration with the woofer, but what has happened at the top end? Have tweeters really conquered breakup or is it that most of us cannot even hear much above 15 kHz?

 

[Michael J]

Size isn't everything. Fashions change. Advertisers seldom know anything. There usually isn't much above 15kHz anyway.

 

[kc5819w]

Several Genelec active 2 way monitors use small 19mm metal tweeters.

 

[darrenyeats]

Most tweeters have narrowing dispersion above 10kHz, but you only need enough for some toe-in/out above 10kHz.
- boundaries are anyway increasingly absorptive above 10kHz
- so reverberant field and even off-axis response are important below 10kHz

For reference: Floyd Toole 30:15 to 31:00 here https://www.youtube.com/watch?v=zrpUDuUtxPM.

BTW this is why the Beolab 90s have controlled directivity up to 10kHz.

 

[davidsrsb]

28mm allows the crossover at around 2kHz without high distortion levels. 19mm tweeters in a two way must be responsible for all kind of trouble from overstretched mid bass and the tweeter too close to resonance

 

[kc5819w]

19mm tweeters in a two way must be responsible for all kind of trouble from overstretched mid bass and the tweeter too close to resonance

Not necessarily. If you have a crossover of around 3KHz as with many medium size two ways, you can use one like this.

http://www.falconacoustics.co.uk/downloads/Seas/h1283_datasheet.pdf


Ones with larger drivers tend to use 1" tweeters at lower crossover.

Additionally wave guides can be used to couple with the woofer properly.

 

[RustyB]

It's got naff all to do with 25 or 28, to get a low XO point you need a low Fs, and that requires the tweeter to have a rear chamber.

 

[James]

19mm tweeters in a two way must be responsible for all kind of trouble from overstretched mid bass and the tweeter too close to resonance

That accounts for a lot of the SBL's character.

 

[davidsrsb]

It's got naff all to do with 25 or 28, to get a low XO point you need a low Fs, and that requires the tweeter to have a rear chamber.

Surely a 28 has ~25% more area than a 25 so excursion will be less at the low end?

 

[Fatmarley]

Surely a 28 has ~25% more area than a 25 so excursion will be less at the low end?

Yes, the more xmax and sd, the lower you can cross over. The vifa xt25 ring radiator has a very low fs of around 450hz but wont cross very low.

 

[RustyB]

Surely a 28 has ~25% more area than a 25 so excursion will be less at the low end?

Moving mass depends on the size of the coil former and depth of windings.

 

[demotivated]

I don't know the pros and cons of modern tweeters, but the old audax tweeters in the 70s [that were about the only game in town for small manufacturers] were awful - although they usually sounded better than their paper spec. They made coil and gap equal length so excursion was technically zero. The cheap 19mm mylar that audax and others sold was their best tweeter product in the 80s if it was crossed high up.