DIY Tweeter horns - 2404 based?

[Dave Zan]

I currently have 2405's but think that it would be better to have tweeeters whose directivity was more constant with frequency.
I want approx. 1 radian horizontal and .67 vertical (60 x 40 for the metrically impaired).
I have examined a dismantled 2404 and it looks reasonably easy to keep the back 2/3 and just replace the plastic "baby butt" with a new home made horn - any one here tried this?
The current horn preference is for a short exponential transition to a more or less parallel sided pyramidal horn ("conical" expansion rate)
- any one here tried this horn shape?

TIA

[Robh3606]

Hmm that's an idea doesn't sound easy though to make it really work well. Black magic to me! Just a thought the 076 had an eliptical horn. Maybe that would work as a stating point. Problem is I don't know what the coverage is and have never seen a spec sheet to cover it.


Rob:)

[Zilch]

076 is a good suggestion, but finding them's another matter. Member Steve Gonzales loaded 076 horns on 2404 motors with apparent success recently.

2405 is not far off from what you're wanting, actually:


Dispersion (6 dB down points, 1/3-octave band, pink noise):


140° horizontal x 40° vertical at 10 kHz

90° horizontal x 35° vertical at I6 kHz

65° horizontal x 30° vertical at 20 kHz


If that's too "beamy" for your preference, I'd just go directly to 2404.


OR look at what JBL does for UHF in some of their 60 x 40 controlled directivity offerings, if anything....

[Alex Lancaster]

:) I have looked at factory specs for over 25 Years, still the 2405 sounds better to me; ???-

[ralphs99]

Hi Dave,

I’m wondering what you mean by wanting constant directivity. As I’m sure you know a CD horn has a similar polar response with varying frequency. So for a horn to exhibit constant directivity, it must cover a reasonably wide frequency range. ie you could measure polar response at 1/2 octave centre frequencies to see how constant the directivity appears. (Have a look at the directivity index graphs for the 2344). As the 2405 only covers one-and-a-bit octaves, the concept of constant directivity is less meaningful than for a midrange horn that covers several octaves. I personally think it is sufficient to simply match the approximate polar response of the tweeter in the horizontal plane with the polar response of your mid-range device. As the polar response of a 2404 and 2405 are similar in the horizontal plane, ~100 degrees at 15kHz as Zilch pointed out, I feel there will be little benefit in switching to a 2404. Having said that, you may simply prefer the sound of the 2404 or need the extra dispersion in the vertical plane.
Maybe you fill us in on the rest of your system….

Cheers,
Ralph.