Midrange drivers dips above 1Khz...

[critofur]

Seems like almost every midrange driver has a dip somewhere between 1-2Khz, even very good ones. Anybody know what's the consistent cause for that from driver to driver?

[LaMa]

what kind of midrange? If you are referring to a cone (i.e. 4" midbass), then you see the visible effect of beaming. The wavelength becomes smaller than the cone diameter (6" around 1.8 kHz, 5.25" around 2.3 kHz).

[tinitus]

I believe its true that most drivers have a problem around 1khz, and noone can say exactly why...or else problem would be solved
It may be visible at impedance too
Some think its related to cone/surround interaction

[ShinOBIWAN]

Are you talking about when mounted to a baffle? If so then diffraction would be the first thing that springs to mind particularly as the average baffle width->wavelength would be somewhere in that range.

[crazyhub]

Originally posted by ShinOBIWAN
Are you talking about when mounted to a baffle?

No, he is talking about floppy polypro drivers, haha. Straight line for ceramics!

[ShinOBIWAN]

Originally posted by crazyhub
No, he is talking about floppy polypro drivers, haha. Straight line for ceramics!

Yeah, straight line and then a break up peak the size of Dirk Digglers package. Personally I'm not really into that sort of thing.

[crazyhub]

Originally posted by ShinOBIWAN


Yeah, straight line and then a break up peak the size of Dirk Digglers package. Personally I'm not really into that sort of thing.

Your reply is much faster than your drivers!

[crazyhub]

IMHO:
On axis dips: Baffle step
Off axis dips: Beaming

[Jay_WJ]

Originally posted by critofur
Seems like almost every midrange driver has a dip somewhere between 1-2Khz, even very good ones. Anybody know what's the consistent cause for that from driver to driver?

It is called cone surround dip---tinitus is right. In practice, it isn't that audible since it's usually very narrow.

[critofur]

The dip I'm talking about is the one you see on manufacturer's charts, sometimes followed by a bump. This would typically be measured on-axis on a large baffle in an anechoic chamber.

When I was working with someone who designs and builds his own custom drivers for his company, I referred to it as the dipbump, with our drivers it was around 2Khz and not as severe as in some of the nice Vifa, Peerless, and Audax drivers I'd been looking at.

Having a dip right next to the bump made it less desirable to try to use a notch filter on the bump

I hadn't done much testing to see if the dip is audible, because, it's so hard to eliminate mechanically. When we did finally succeed in getting a flat response (by spending hours attaching bits of sticky tar in various shapes to the cone) it sounded surprisingly bad.

"cone surround dip" eh? I guess accordion cloth surrounds don't have that issue as much? Maybe the double roll rubber surrounds are little better than the single roll ones also? We even tried cutting the edge of the cone in a zig-zag pattern to see if that would help, it didn't