AR-3a Response Curves and Test Reports

[administrator]

Yes, and that will leave the AR section to be about information, restoration and other brand-specific things of use and value to many visitors here. As it should be.

-k

Well said... and here it goes!

Guys, a good rule of thumb for the AR forum is to leave personal stuff out of your posts. I don't have the time to remove individual posts from these threads and it's unfortunate that some really interesting first posts have gotten dragged into their new home here. I really loathe censorship anyway, so I'll continue to move entire threads into the Kitchen.

Ideally at some point in the future I'll work with a bunch of volunteers to go through the entire AR forum to perform the cleaning and organizing that are well overdue... but for now I'm just concentrating on keeping flame wars out.

Thanks,

Mark

[Zilch]

I don't have the time to remove individual posts from these threads and it's unfortunate that some really interesting first posts have gotten dragged into their new home here.

Mark, may I respectfully suggest that the new information Tom has posted in this thread, or at least links to it, since it's already in the database, might find residence in the Library? Howard and others have contributed some, as well.

Thank you for providing a place where we can discuss and debate what it means....

[kkantor]

It is not unusual to see a dome tweeter built in such a way that it is shooting out of a shallow horn. (One advantage of this is that the recession reduces the change of dome damage.) In that case, the dispersion will mostly be dependent upon the horn-mouth diameter, and that diameter will be larger than the dome itself.

Howard Ferstler

Yes, this degree of protection from damage was a huge benefit, especially for speakers sold in larger retailers, where salespeople are not always around.

So here's my story on the 3/4" vs. 1".

1- The very first NHT's were made with a small diaphragm tweeter, the (in)famous Audax polycarbonate. I think it was a 12mm dome. Along with great dispersion, it had an excellent axial response and was very inexpensive. Very inexpensive.

2- Unfortunately, due to the very small voice coil diameter, and the low efficiency of a small diaphragm, it blew out too easily. NHT, and almost everyone else in the world, replaced the Audax with the similar Foster/Tonegen unit, that had a different construction and a slightly larger size. Big improvement. Still, <3/4" domes don't hold up to loud music, especially if you try to cross them over low enough to make a 2-way. I doubt that 20% of those old NHT tweeters are still operational.

3- When Tonegen lowered the price on its fantastic 1" soft dome tweeter, the one with the recessed dome in a "semi-horn", I jumped on it. (Early 90's.) This tweeter platform had been developed in collaboration with AR, and worked extremely well. The axial response was superb. The tweeter could eat 2,000W peaks, polars were good, Fs was usable and the units from Japan were almost spookily consistent. What was not to like? A few dB at 60 degress off axis above 15 KHz?

4- The main advantage of the driver's construction, besides the finger damage control, was that it added a couple of dB to the sensitivity. Thus, it could be padded down in the xover. This, combined with the 1" VC and good motor design, meant the unit rarely failed.

5- 3/4" domes just couldn't survive in the age of big power amps, 2-way speakers and loud music with low crest factor. As excellent 1" domes appeared, 3/4" domes disappeared. You can see this happen in historical brand product roadmaps and in the catalogs of suppliers like Audax, Peerless, Foster, etc. Top octave dispersion had never been proved to be an important factor, but reliability and power handling is utterly crucial in the marketplace.

-k