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There are few tweeters that can play to ~1.5khz or so. As said above, it's all about compromise. Most of the tweeters that can play that low are those designed specifically for it. Most of your european manufacturers, like SEAS, Dynaudio, etc. have at least one tweeter designed to play well down low. The Morel Supremo is another example, but it doesn't quite handle lower frequencies as well as a lot of the other dedicated home audio tweets. The sacrifice, of course, is high volume output and the resultant increase in distortion from the tweeter. At lower output levels it isn't an issue, but if you're looking to crank it really high it's going to sound pretty strained.

Most tweeters that are capable of this are 1 1/8" domes with larger motor designs and added mass to the diaphragm. The SEAS Crescendo would be an example. Most are designed in order to meet with a tricky midwoofer in a 2 way application.

damn double posts... thought it was my slow connection. :o

Well, there are always compromises with speaker engineering.

There's a lot of truth that as you narrow the bandwidth of any particular speaker, narrowing in on where it is truly excellent, the better that individual speaker will perform.

So trying to extend a tweeter to play all the way from up above 20,000hz, down to 1khz is going to compromise the performance of the speaker...
...in other words, the things you need to do to make that speaker able to handle the increased excursion involved in playing frequencies that low will compromise the detail in the upper ranges.

I've got a 3" Aura speaker that I'm using in my Pathfinder that's a great example of this. I wanted a speaker that could handle an extended range of frequencies, so that I could build a true phase-aligned array out of them. So I have six total in the install.
And from the standpoint of my experiment - the phase-aligned array - the experiment was a success.
But from the standpoint of listening to detail - yes, the Auras reach all the way up to 18khz. But they don't have the fantastic detail of say, a nice Focal TN52 tweeter - in fact, they don't have the detail of a ho-hum soft dome tweeter. Even with the phase plugs onboard (which help extend the response of the driver up higher).

Personally, I'd suggets this:
Rather than trying to extend the tweeter response way down low - I'd suggest running a 3-way setup, with a high crossover point on the tweeter - really relegating it to "ambiance and staging" duties. Maybe above 5khz if you can accomplish it.
A small midrange driver that's easy to mount and aim in a custom location (kickpanels are the traditional "ideal"), to handle all of the midrange duties - where most of the 'easily locatable' material exists.
A midbass driver crossed over around 200hz-250hz or so, to handle the bass duties. Don't think a 6.5" can't do it either.
And of course, a sub.

I always liked the DLS 3-ways - that dome midrange is small and easy to mount in all sorts of places - I wanted to experiment in my wife's VW Beetle, with those big A-pillars way out over the dash... mmmm... :D

[quote="Rivers"]Also, what tweeters actually get low to 1.2khz? I have a morel supremo that will supposedly do 1.5khz but I can't get it to sound good at anything below 3khz.[/quote]

Other than HLCDs, not much. At least not well anyway.

Wow interesting stuff. So in the case of detailed (as opposed to loud) what would your verdict be?

Also, what tweeters actually get low to 1.2khz? I have a morel supremo that will supposedly do 1.5khz but I can't get it to sound good at anything below 3khz.

Side note on directionality:

It isn't so much that tweeters (or high frequencies) are "more directional" - that's a function of the wavelength vs. the width of the speaker cone...

With my 3" Aura mids, playing them all the way up to 18K - it ends up where the wavelength is smaller than the cone diameter, and that brings on high directionality.

If the wavelength on the other hand is very large, and the cone very small, you'll have a more omnidirectional speaker.

Generally, tweeter domes are pretty small - 1" or under - so directionality hopefully won't onset too much until you REALLY get up there - to the point where your hearing might be better than mine, if you can actually HEAR things up there still... the real "top half octave" stuff... :p

The debate involves a few things, IMO:

1) human capability to perceive distortion varies with frequency
2) how many "octaves" of music are handled by each driver
3) where most of the musical energy exists in a recording of normal music
4) where the crossover frequency is set

[b]1)[/b] Simply put - the lower you go in frequency, the less sensitive the ears are to distortions in the signal. Pretty much, as soon as you come out of the midbass octaves, perception is pretty clear - so IMO not as much of a "mid vs. tweet" issue - but technically, perception is still increasing as you cross that crossover frequency into the tweeter range. ;)

[b]2)[/b] This of course varies depending on where your crossover frequency is set to - but usually, that's somewhere in the 3Khz-5kHz range - meaning your tweeter is handling about 2-3 octaves worth, where the midrange is handling somewhere between 5-6 octaves worth (or more, if there's no sub!).

However:

[b]3)[/b] There's WAY more musical material in just about any recording in the range around 100hz through 2000hz or so... and lots of the musical material that exists outside that range (ie. tweeter and sub) are harmonics and ambient elements that more or less give the music energy and define ambiance and reality, as opposed to the "core" content - which is why so many clock radios and computer speakers that can't play outside that range still play the song - but don't sound "great" by any means. ;)
So - one question becomes whether your priority is "loud", vs "detail" (like all this ambiance, imaging, detail, and reality ;) ).

[b]4) [/b] The crossover point usually more or less is just a matter of how much material the tweeter handles vs the mid, how many octaves each get to split... but it's really at a critical point, and it can really affect the install. ;)
For example - one "extreme case" - in my pathfinder, I'm currently running NO tweeters. Why? I have six midrange units that can play all the way up to 18kHz (Aura 3" neos). In this case, the priority of "which driver is more important" falls completely on my mids - so I need to angle and arrange them properly, since they are fully defining the soundstage and imaging.

However, in another extreme case, you might find someone with a 3-way component set, with a midbass driver playing all the way up to maybe 300hz, and a midrange only playing up to about 1200hz - only two octaves. And then, a tweeter playing from there up - four octaves.
This may be done intentionally (with a tweeter that can DO it!), putting more of the musical content on the tweeter, because the tweeter is smaller, easier to mount, easier to angle, not requiring a baffle or enclosure, etc - and in that case, would define more of the soundstage, particularly with regard to imaging and ambiance.

So it's not a debate that's got a "winning side" - that's my point. :cool:

It's a debate that changes back and forth, as you change all these parameters and priorities. ;)

And a great reason for a thread!

[quote="Rivers"]Jonathan are you using a W18NX001?[/quote]

Not at the moment. I've considered using some in either a car audio application or for home audio use down the road, but right now we're about to put up another MBO line and I'm stuck with the engineering at the moment. Not a lot of time for fun when you put in 96 hours in a week *sigh*.

I was going to say pretty much what John said. Every speaker and component of the system is important (my chain analogy again..) but tweeters are the most directional of the speakers, so their placement can be vital. Midrange covers most of your audio spectrum for music and nearly all of your vocals, while still being fairly directional so their placement and signal path length compared to the tweeters is also vital, as is their absolute phasing. Remember 70% of your music is covered by the front stage of your system as far as frequency range goes.

Blending the tweeters and midranges is vital as well. If the two don't match well, and if the crossover you choose doesn't do the job of blending them together well, the quality of each speaker isn't going to matter in the least. Same goes for the installation and choice of mounting locations for those speakers.

Never get so focused on one thing that you neglect other equally important factors. Never miss the forest for the trees.

As are mine Jeremy.