Are radial phase plugs really that good?

[Steve Schell]

Hi Todd,

Yes, I think you are correct that Dr. Hilliard wanted to avoid the touchy patent issue in desribing the radial vs. circumferential phasing plug issue. It also seems that Lansing reverted to the manufacture of circumferential plugs as soon as the patent issue was resolved.

I'm not so sure about the superiority of the Tangerine phasing plug vs. the Blackburn/Lansing radial plug, though. Your comments are the first I've heard of the shelf between the thin and wide slit portions being a problem. What seems to be a measure of quality though, in radial designs, is the number of slits. In theory, a greater number of slits should yield a superior high frequency response. The Blackburn plug employs 20 slits. I'm not certain how many slits the Tangerine plug employs, but I believe that it is fewer than this- don't have any on hand to check.

Perhaps one of these days we can compare plane wave tube measurements of a Lansing 285 driver and an Altec 288 Tangerine equipped driver. I have no problem with the sound of the Tangerines- my nephew's system uses 288-16Ks, and sounds mighty good to me.

[gearjammer]

I count 11 slits on the small format tangerine
phase plug

[thevott]

I have a correction to make: I stated earlier that my Model Nineteen phase plugs were black. In fact they are orange. It is my newer 902 drivers that have the black ones. Also, no centering pins on the 902s! The diaphram assembly actually has a small amount of side to side play until the screws are tight. What's up with that Altec?

As for the orange 802 plugs, one came un-glued inside the driver once. Sounded terrible. I removed the diaphram and re-glued the plug with epoxy, setting the weight of the driver and 811B assembly on the phase plug while the glue set. No problems with it since. It was pretty cool to observe the plug out of the unit though.

MP

[Mirrophonic Sound System]

I was going to comment on the phase plug in Tannoys
but I now feel it is worthy of a separate thread.

[cclark65]

Earlier in this conversation I mentioned that I had read somewhere that the phase plug had something to do with the sound depending on the horn. I finally stumbled across that information. It is on the old Altec message board, hosted by this same site.
http://members3.boardhost.com/AltecU.../msg/3935.html
Maybe ideas have changed from a year or so ago, but I knew I had read it somewhere!