Let's talk Tweeters!

sorry I didn't say... to your question,  yes, it is because their inherent capacitance, without a crossover, they come in on their own at 1800 hz. 

@erik_squires
  "Well, We're far off topic now" 
I was hearing a discussion of trying to blend ribbons with heavier mass drivers and how speed affected the blend with @asvjerry.  You said that you could blend 15 inch woofers.  I was giving a basic explanation of mass vs motor and driver speed isn't necessarily based on the size of a driver, but the balance of the total design.  That theory hold true on all traditional drivers tweeters to subwoofers. 

Hi Guys,   Looking at the last few comments about mixing light mass drivers with heavy mass drivers,  speed and matching. I recently was on another thread where there was an argument going on about mass and speed.  A lot of folks out there just don't understand what it takes in drivers.... I guess I'm going to tackle it by comparing it to 2 cars...Lets take a 1970 Cadillac Deville with a 472 cubic inch engine and a 1970 Volkswagen bug with a 97 cubic inch engine...  Put the Volkswagen engine in caddy,  will it move?  it sure wouldn't move well, how would it accelerate?  what about if you down shifted and had to slow down? The engine could not properly power this automobile without some serious souping up.   Lets put the Cadillac engine in the bug.... Well, It'll be fast for sure,  but the bugs suspension would not handle the big engine, if you stomped on the accelerator the car would be all over the road.  You would have to seriously beef this automobiles suspension to have any chance of handling this engine.... Speaker Drivers aren't a whole lot different. A certain amount of mass requires enough motor to move it.  We can tune the suspension to help,  or turbo charge the engine (maybe neodymium) to improve performance but in every case matching mass & motor is what its all about.... On any driver,  add mass and sensitivity will drop, MMS/QMS/QTS  will rise,  as you add motor the driver moves easier,  get too much motor and the QMS/QTS get so low that the driver will no longer go down to its lower frequencies, a real problem on a woofer, but accurate for all traditional drivers.
Ribbons are a different beast, very light I have a pair of Founteks here at my house now as well as a pair of the old ESS Folded horns that were mentioned above... They are fast,  but with careful selection they can be matched....I also love how wonderful impedance and phase are on ribbons.  I'd love the Ess with a well matched 15. I really like ribbons, but you know,  I still love a good dome too.  
Tim 

Hi   @erik_squires    over the years, at Marcof we heavily modified the old Motorola Piezo's... In the end, a tweeter with the reputation of being harsh and brittle ended up being pretty good.  They are amazingly fast, they remind me of a dryer version of a ribbon after mods... The best current single current model available now is the CTS KSN-1141.....If you ever end up wanting to try them, private message me and I'll send you mods for them.  Tim

@erik_squires

Hi Erik, I have a pair of the Original Big Ess folded horns at home also and agree, its a nice animal, but much larger than a dome. What sets this tweeter apart is its size and what it does.
It has about a real world sensitivity of about 93 @ 8 ohms. It has a Xmas of over 3mm! Linear 1 way travel is 1.5mm.
If you use their spec of 2.83v input and an average sensitivity of 95, it is plus or minus about 1 db for its operating range.
With this Xmax, it can be crossed very low, they have tested it at 1.3k. This construction should have very low distortion. This tweeter should be able to compare with just about any dome out there.... And YES EXPENSIVE. But, you should be able to come up with some world class MTM’s in to 90 to 95db sensitivity.

A friend sent me this to take a look at several months ago.  On Paper, it is one of the best tweeters that I have seen.  It appears to come from one of Morel/Accuton  designers.  Has anyone tried or even heard this?  They are fairly expensive. I'd love some info on real life experience. 

http://hificompass.com/en/content/bliesma-t34a-4-34mm-alumag-dome-tweeter

@erik_squires
Hi Erik, I have never heard the Lansche plasma’s so this comment isn’t directly for that speaker, but why couldn’t it be the worlds best tweeter, May not be at all, but something is.
You speak of measurements specifically frequency response. As you know it is completely possible for a tubed amp and a solid state amp to have identical fr, yet, we all know that they will not sound the same.
I say all of this because I remember Mr. Hill dragging in his plasma tanks and Hill Plasmatronics to Marcof/SpeakerCraft. That tweeter was fast, airy, yet rich, detailed yet smooth. For me, it was the best tweeter that I have ever heard.... Although the rest of the speaker certainly was not.

I don’t know what technology Lansche speakers use, but I’d love to hear a pair.