Radial(Tangerine) versus the regular circumcerential phase plug

[Ronald Lee]

I am not an engineer, but I've read a bit of the technical stuff from Altec that it is supposed to be better, to extend the high freq response etc.

When I first got my 806 drivers, I was curious what the phase plug actually looked like; and so I opened the back and remove the 'phram and looked at the phase plug, it was a piece of machined steel, with semi-circular groves, no biggie, and replaced all of the parts and button it up.

I haven't actually taken apart a radial/Tangerine phase plug driver, but the newer phase plug is a piece of molded plastic that is held in place by glue. One thing for sure, the new radial phase plug is a lot cheaper to make because it is cheaper to mold a piece of plastic than to machine a piece of metal(of course once you recovered the cost of making the mold.)

Can we actually hear a sonic difference between the two phase plug designs, I know they can measure it with instruments. I am not against the new plug, I am all for cheaper, without any performance degradation. I am just curious.

[Old Guy]

I kinda agree, cost was part of the equation.

In theory the radial plug is better, but hard to machine. So it's molded.

Personally would like to see the Tangerine type made in something like obsidian, very hard and smooth. Might shatter in portable apps. Perhaps Pyrex?

But I'd always rather think about what could be rather than what is. Lots more freedom that way.

[Ronald Lee]

Old Guy: Making a mold is not cheap, I believe you have to have a die maker do it, and those folks don't work cheap. What is the point of making the phase plug out of obsidian? Might was well be out of steel if you are going through all of that trouble to begin with.

Does GPA have a radial version for their small format compression drivers? What about their large format drivers?

[Old Guy]

Old Guy: Making a mold is not cheap, I believe you have to have a die maker do it, and those folks don't work cheap. What is the point of making the phase plug out of obsidian? Might was well be out of steel if you are going through all of that trouble to begin with.

Steel is magnetic is an obvious point. I was thinking of a hard moldable non-magnetic material.

You are correct about start-up being expensive on a mold, but completely wrong after that.

Once you have paid for the mold parts are much cheaper than machined.

I'm an ex-business owner remember...I ran numbers all the time.

[whitebroncoii]

I am not an engineer, but I've read a bit of the technical stuff from Altec that it is supposed to be better, to extend the high freq response etc.

When I first got my 806 drivers, I was curious what the phase plug actually looked like; and so I opened the back and remove the 'phram and looked at the phase plug, it was a piece of machined steel, with semi-circular groves, no biggie, and replaced all of the parts and button it up.

I haven't actually taken apart a radial/Tangerine phase plug driver, but the newer phase plug is a piece of molded plastic that is held in place by glue. One thing for sure, the new radial phase plug is a lot cheaper to make because it is cheaper to mold a piece of plastic than to machine a piece of metal(of course once you recovered the cost of making the mold.)

Can we actually hear a sonic difference between the two phase plug designs, I know they can measure it with instruments. I am not against the new plug, I am all for cheaper, without any performance degradation. I am just curious.

My opinion:
The phase plug material is not an issue and makes no difference. A phase plug helps make a smooth transition into the throat of the horn. The original Altec phase plug (circumferential) was designed to work on the horns of the day (multi-cells/311/511/811). The Tangerine phase plug was designed for MR horns.

There is a sonic difference. The difference is not great. The difference is probably no greater than different manufacturing batches of diaphragms. Your listening space will have more effect on the sound of your horns. I simply select matching diaphragms and don't worry about it.

[Steve Schell]

Just to work a bit of history into the discussion, I'll mention that the Lansing 801, the grandfather of all the small format drivers, used a fourteen section radial slit phasing plug. We discovered this several years ago, and it is discussed here:

Lansing discovery- WHOA!

A few years ago I spoke with a fellow here in southern CA who told me that Altec engineer Cliff Henricksen had worked on prototypes of the Tangerine radial slit phasing plug in his garage. He mentioned that Mr. Henricksen was disappointed later when he found that Altec had reduced the number of slits compared to his prototypes when they put the Tangerine into production.

I haven't messed much with the Tangerines, but have found that there is very little if any difference in the measuring or listening with the original Lansing 801 (radial) and 801b (circumferential) drivers. They seem to be different ways of accomplishing the same result.

[Old Guy]

My opinion:
The phase plug material is not an issue and makes no difference. A phase plug helps make a smooth transition into the throat of the horn. The original Altec phase plug (circumferential) was designed to work on the horns of the day (multi-cells/311/511/811). The Tangerine phase plug was designed for MR horns.

There is a sonic difference. The difference is not great. The difference is probably no greater than different manufacturing batches of diaphragms. Your listening space will have more effect on the sound of your horns. I simply select matching diaphragms and don't worry about it.

I'm' just thinking a harder material would perform better....maybe insignificant.

A magnetic material is going to affect the field...

BTW are not the 806 plugs aluminum? I don't recall steel, but I haven't been inside one in ten or 15 years..

[voice of the theater]

There is a sonic difference. The difference is not great. The difference is probably no greater than different manufacturing batches of diaphragms. Your listening space will have more effect on the sound of your horns. I simply select matching diaphragms and don't worry about it.

I haven't messed much with the Tangerines, but have found that there is very little if any difference in the measuring or listening with the original Lansing 801 (radial) and 801b (circumferential) drivers. They seem to be different ways of accomplishing the same result.

I always assumed that the primary reason that my model 19's have a significantly/noticeably "better" extended high frequency response than my Valencias is because of the radial phase plug design incorporated into the 802 driver compared to the circumferential design used with the 806 (Valencia) driver (the 19's seem to have a flatter h.f. response than the Valencias--they don't start to drop off at 13k). Are you guys saying that the radial/tangerine phase plug design makes little (or no) difference? Even though the 802 itself is a superior driver to the 806 and the original Model 19 diaphragms that I have are 10 years newer than the original Valencia diaphragms that I use, isn't the tangerine design primarily responsible for the significant audible difference in the extended high frequency response between "stock" Valencias and Model 19's in general (particularly above 13k--hopefully, most of us here can hear sound at 13k and at least some of the frequencies above it)?

I'm reading this quote from the Altec Library http://www.lansingheritage.org/images/altec/specs/home-systems/model-14/page3.jpg

"In the past, compression drivers had all been equipped with circumferential phase plugs. These older devices forced their high-frequency energy through two equidistant circular slots. But because of the design of these plugs, some of the higher frequencies were lost. Our radial phase plug, which we've nicknamed the Tangerine, utilizes a unique radial slot design which allows a free flow of high-frequency energy and results in an honest frequency response to beyond 20 kHz."

I read this quote quite a while ago and since then have attributed the significant improvement in h.f. response in the 19's compared to the Valencias to the "Tangerine". I add "extra" treble to my Valencias with my equalizer (mainly 13k and up) to get them to sound similarly bright to the 19's so it seems they do start to drop off after 13k whereas the 19's seem to have "an honest frequency response to beyond 20 kHz." I would think that diaphragms and crossovers etc. play a role, but I've always been convinced that it was the radial phase plug design itself that was primarily responsible for the 19's being able to play all the way up to 20 kHz as shown in their specs. In fact, when I was shopping for vintage Altecs on ebay I called Bill at GPA to ask him about the availability of diaphragms and recone kits for some of the older Altecs and at the time I asked him about the radial phase plugs and he told me they DO significantly extend the high frequency response in the highest frequencies. I'm not argumentative by nature so please don't take this the wrong way but it seems like either you two guys are underestimating the effect of the "improved" phase plug design or I'm over-estimating it and Altec was over "hyping" it?

[Altec Best]

I read this quote quite a while ago and since then have attributed the significant improvement in h.f. response in the 19's compared to the Valencias to the "Tangerine".

You got to remember too that the 19 got a much better driver than Valencia.The 802G got a bigger Alnico Magnet and different 23744 diaghram along with the Tangerines.All these combined improvements is why they sound better and extend much higher than the Valencia IMHO

[voice of the theater]

Makes sense, AB. But you would agree that the Tangerine is responsible for a significant part of the improvement/extension as Altec stated in their literature or would you say it makes little (to no) difference? I think that was the gist of Ron's original question.

....Can we actually hear a sonic difference between the two phase plug designs, I know they can measure it with instruments.....