A couple days ago, I picked up a new tweeter to test for potential installation in my truck. This Vifa D26NC55-06 was run alongside a Focal TN46 just for the sake of comparison, and were done quickly. The Focal tweeters are generally regarded as reasonably high-quality but some find them harsh directly on-axis. Well, here's why:



There are a total of four plots in there.
Red = TN46 with phase plug, with intended crossover
Maroon = TN46 without phase plug, no crossover
Green = TN46 with phase plug, no crossover
Blue = Vifa D26NC05, no crossover
It might be hard to differentiate the Red and Maroon lines. The Red line is the one starting off all alone and it remains smooth through the 13k region. The Maroon line is the one that drops in the 13k area, then screams upward.

Notice the awful breakup around 17-20k in all the TN46 plots. Notice the notch depression without the phase plug in place (maroon line). Notice the relative smoothness of the Vifa trace. The reasons for these things become evident when you look at the impulse responses.



The above plot should have a smooth series of well-defined ripples immediately following the initial rise, and they should fall off in magnitude very soon after. The Focal Impulse is terrible. It has little definition and lasts too log. It *should* look like this from the Vifa:



This is one of the ways you can tell what's a good loudspeaker and what's not. The Focal isn't bad. It's just not in the same class as the Vifa.

 

Looks greek to me . What does it mean in layment terms ?

 

In direct frequency response measurements like this, what you want to see is a flat or nearly flat line. What that corresponds to is the speaker's ability to play each frequency equally as loud as the others. When someone describes a speaker as "harsh" or "ringing" it means certain areas of this curve are being played louder than the others. Flat is a good thing. Peaks and valleys are not. The more peaks and valleys there are or the larger they are, the worse the speaker performs.

As far as the impulse response plots are concerned, what you want to see there is a "clean" impulse. There should be a clearly defined line upward at the beginning of the speaker's movement and then downward past the neutral line. That's the cone or dome settling back to it's rest position. The slight movement after that is the cone or dome settling back in. Think of it as a measurement of how well the speaker responds to a quick burst. When it's ragged like the Focal's, it translates into a frequency response that's not smooth and has undesirable distortions.

That help?

 

Yes, that helps a lot. So basically, a speaker that progressively moves with sound increases is more desirable than one that flutters with higher and lower extremes.

But can your ears actually hear the difference ? and if so to what point ?

BTW, I have a thread over hear asking about a stereo system that I am trying to put together. Do you mine taking a look.

Thanks.

http://forums.corvetteforum.com/show...56&postcount=7

 

You can absolutely tell the difference, and most times it's not small. It takes experience to see a plot and imagine how it would sound, but it's certainly true that anything you hear can be measured, and the differences shown.

Those guys have you on the right path for a system. I'm not an ED fan, but the rest looks OK. Definitely listen to any speakers first. It's the most important part of any system.