Selenium HM17-25

[badman]

Selenium HM17-25

The Datasheet

Interesting horn, this Selenium. It looks like a nice, cheap way of getting a smoothly terminated horn without a diffraction slot, basically an adapted JBL 2404 with the dispersion characteristic traded for smoother throat contouring. I've not seen these used in any projects, but have ordered a quad for testing (I plan to hack 2 of them to get the driver mounting piece for use in DIY OS waveguides).

Anyone have any thoughts on this itty-bitty bi-radial? With a little care, it looks to be a very good candidate for a geddes-styled 2-way with a 12", XO at 2.5k.

[MethMan]

Maybe this you will find helpful. Polars per 10deg, 1/3oct smoothed. No idea about any 12" reaching 2K5 without serious break-up issues.

[Inductor]

The horn is problematic in the back (to be airtight) against the box. Not a flat surface. I'm using it in a 3-way.

[wg_ski]

The 17-25 sounds really nice in the horizontal plane. Go up or down, and it goes south in a hurry. The 25-25 metal horn degrades a bit more gracefully on the vertical axis, but won't get up as high regardless of the driver used.

In either case, they work better paired with 10's than 12's when crossed at 2-2.5k.

Wolf (from the PE board) has used the 17-25 and thought well enough of them to pair them with some really expensive Morel midranges. I think he used the cheap Selenium driver, too.

[Pano]

I've had these for years. Driven with the Selem D210Ti. Not bad.
Strange frequency response at the top, but that may be the driver.

I did modify mine a little. I filed down the ridge in the throat at the start of the horn flare. Removed the bug screens from the driver. Used putty to fill the gap between the horn throat and the the driver throat. As mine don't screw all the way in, there is a nasty gap.

Guess I should post before and after measurements to see if there is any merit to my mods.

[badman]

Originally Posted by MethMan

Maybe this you will find helpful. Polars per 10deg, 1/3oct smoothed. No idea about any 12" reaching 2K5 without serious break-up issues.

Wow, yes, that's extremely helpful! Very nice polars. Looks like 1k5 IS a viable crossover target, assuming a very steep applied slope. I was thinking 2k5 as I was assuming such a small horn to have very limited pattern control at the lower end, looks like the tight pattern works better than I thought.

It would indeed be interesting to see your before and after, pano. I'm enthusiastic about trying this horn now

[Pano]

I'll do some after mod FR plots then.

No idea if I did any good.

[MethMan]

Originally Posted by badman

Wow, yes, that's extremely helpful! Very nice polars. Looks like 1k5 IS a viable crossover target, assuming a very steep applied slope. I was thinking 2k5 as I was assuming such a small horn to have very limited pattern control at the lower end, looks like the tight pattern works better than I thougt.

It is smaller because it relies on edge diffraction. Take care, polars are 1/3oct. smoothed, so don't expect world-class performance.

[badman]

Originally Posted by MethMan

It is smaller because it relies on edge diffraction. Take care, polars are 1/3oct. smoothed, so don't expect world-class performance.

It doesn't seem to have any throat roughness in the examples I have here, which is BONUS!

[badman]

Originally Posted by panomaniac

I've had these for years. Driven with the Selem D210Ti. Not bad.
Strange frequency response at the top, but that may be the driver.

I did modify mine a little. I filed down the ridge in the throat at the start of the horn flare. Removed the bug screens from the driver. Used putty to fill the gap between the horn throat and the the driver throat. As mine don't screw all the way in, there is a nasty gap.

Guess I should post before and after measurements to see if there is any merit to my mods.

That ridge seems to have likely been an apparent ridge, if the ones I have are any indication- apparent in that it was there because of the gap between driver and horn.