Q about throat shape on 511b horn

[atilsley]

I'm currently enjoying a 511 with 902 driver on top of 625 bass with 416.

I noticed the throat shape of the 511 as being a little odd (this is my first 511, so nothing to compare with). It seems the throat opens for 2-3 inches, then actually reduces somewhat before the main horn expansion starts. Is this normal?

Kind regards

Andrew

[fpitas]

If you mean the vertical "pinch-in", yes, that's normal for radial horns. If you look closely, you'll notice that the main horizontal flare starts right where the throat begins to pinch down, so the area doesn't change suddenly, but still follows an exponential expansion. The idea is to induce the wavefront to start expanding in the horizontal direction, without causing a sudden change in the area progression (flare rate). Sudden changes in the expansion would cause a reflection back to the driver, resulting in ragged frequency response and phase anomalies. Altec didn't invent the radial horn, they borrowed older technology. I once found an article describing it. Give me a few hours and I'll find it and post a link.

Edit: found it: http://www.aes.org/aeshc/pdf/how.the...dispersion.pdf

[atilsley]

If you mean the vertical "pinch-in", yes, that's normal for radial horns. If you look closely, you'll notice that the main horizontal flare starts right where the throat begins to pinch down, so the area doesn't change suddenly, but still follows an exponential expansion. The idea is to induce the wavefront to start expanding in the horizontal direction, without causing a sudden change in the area progression (flare rate). Sudden changes in the expansion would cause a reflection back to the driver, resulting in ragged frequency response and phase anomalies. Altec didn't invent the radial horn, they borrowed older technology. I once found an article describing it. Give me a few hours and I'll find it and post a link.

Edit: found it: http://www.aes.org/aeshc/pdf/how.the...dispersion.pdf

Great, thanks...I thought for a moment that perhaps the horn had been bent or crushed down accidently.

Here's my rig.

http://www.hostboard.com/forums/f700...-a/index2.html