Radial(Tangerine) versus the regular circumcerential phase plug

[Steve Mac]

All I can say is after listening to a 288H, I forgot all about the argument and the measurements and the testing and started enjoying the music. BTW the high end on my 288Hs with the tangerine style had more sparkle and coherence than the 802D(modded 808A) 1" drivers. I was quite surprised when the high end cleaned up...wasn't actually expecting that.

It's difficult for some to compare the quality of the upper frequencies because lots of people's ears aren't to acute up there and I've heard a lot of amps that turn the quality of the upper frequencies into hash.

[voice of the theater]

OK guys, many of you are absolutely positive that 416s and 515s go down to 8Hz and that the 802A HF driver can go out to 102kHz. I know it is hard to believe that you might be wrong. However, here are a few thoughts. Please be nice and don't put out a "hit" on me. This is the truth as I understand it after working for Altec over 15 years;

All of the 1.75" voice-coil HF drivers with aluminum diaphragms (800/900 series) have very similar frequency responses. The smaller magnets (806) simply have a couple dB less output. Diaphragms are interchangeable in all of these drivers. There is virtually no sonic difference between the 802/902 diaphragm and the 909. The 909 simply handles more power.

The early horns will "beam" on-axis (coverage narrows) as frequency increases. Frequency response measurements on-axis (directly in front) will seem better above 5kHz compared to an MR horn because of the beaming. These early horns did not do a good job in the install markets due to the relatively poor coverage. Please keep in mind that Altec's primary market was installed sound, not home hi-fi.

Electro-Voice engineers developed the constant-directivity horn in the mid-70s and Altec had their version by the later 70s (Mantaray). The advantage with the constant-directivity horn is better coverage. The disadvantage is the on-axis output is spread over a larger area and frequency response "droops" above 5kHz. Crossovers (passive and electronic) required a "horn correction" boost to flatten the response of an MR horn. Please review the 909-8A data sheet from around 1989. No "horn correction" has been applied for these measurements. Figure 1 (plan wave tube) clearly shows the "hump" that I mentioned. This hump is also obvious in figure 3 (MR944A horn) and figure 4 (511B horn). Speakers using these same horns will have "horn correction" applied in the crossover and response curves will be flatter. The generic crossovers (N500, N800, N1209, etc) will have less correction versus a Model 19 crossover.

Remember what I said, all of these drivers have similar measured frequency response. Now, let's talk about published frequency response. Looking again at figure 4 of the 909-8A data sheet, response is not flat. If we select the peak output as a reference, the output at 500Hz and 20kHz is over 10dB down from the peak. Yet the text of this same data sheet says "Frequency Response: 500Hz to 20kHz". Gentlemen, this is called marketing and it is abundant in all speakers and speaker products. The data sheet is saying that this driver can deliver 500Hz or 20kHz information at a usable level. When I equalize a HF horn, I cut the "hump" until the the response is where I want it.

whitebroncoii--thanks for the response--this makes sense to me. I'm aware that the Model 19 crossover is a better crossover than the older crossovers n500,n800 etc. and I figured (as Old Guy said) that it was also an important part of the equation as far as why the 19's have a better hf response compared to Valencias etc. I wondered if the tangerine drivers have a flatter hf response in general than the circumferential drivers--I knew they weren't flat--just wondered if they were flatter. If they do have a flatter response, I would still think the Tangerine is a significant improvement/contributor to the improved h.f. response of Model 19's and other Altecs that use the tangerine plug.

...(see if there's a trend that the tangerine drivers all have flatter/extended hf responses compared to the circumferential phase plug drivers). If I could see the (officially published?) frequency response curves and compare for myself it would go a long ways to either confirm what I've believed about how great the Tangerine phase plug is or to refute it as as mainly marketing hype.....

I noticed on the spec sheet for the 902-8T it says "Frequency response uniform....from 500 Hz to 20kHz (902-8T)." and on the spec sheet for the 909-8A it just says frequency response 500 Hz to 20kHz without the word "uniform". I know this doesn't really mean anything without seeing an actual frequency response curve for the 902-8T, but I still wonder if the 802-8G or the 902 drivers might have more of a uniform/flatter hf response than circumferential drivers.

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

IMHO the Tangerine is slightly better then the better crossover, so 1+1=2, a noticeable improvement.

...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.

As someone else has said; there is likely a measurable improvement with the Tangerine phase plug. It is probably not sonically noticeable.

I'm re-reading the posts in this thread and it seems most people agree that the Tangerine is probably responsible for at least some degree of a (measurable) improvement in h.f. response--I guess the question is now one of degree--is it enough to be noticeable. I'm sure that depends on the listener's ears, acoustics in their room, and other factors. If we had some frequency response curves for Tangerine drivers that we could compare to similar circumferential drivers, it would shed some light on Ronald's original question that started this thread. If we look at the curves and see only a very slight (or no) improvement in the Tangerine's response, that would suggest that there may be no audible improvement. On the other hand, if we see a "significant" (whatever that is) improvement in the "audible" part of the h.f. spectrum (under 20 kHz), then there are probably board members with good hearing and good acoustics in their room etc. that can hear the difference......

Maybe we should just measure a few?

So Pano, or others out there with measuring equipment, if you want to measure a few drivers it could still go a long way to debunk (or bunk?) Altec's claims about the Tangerine (this is starting to remind me of the TV show "Mythbusters" without all the cool explosions!)..... The Tangerine is an important part of Altec "lore" and I think Ronald posed a really interesting question when he started this thread. I think it would be nice to finally shed some light on Altec's 30+ year old claims about the Tangerine. If anyone out there finds links to published frequency response curves on some of these drivers (for comparative purposes), that would still help as well......

OK guys, many of you are absolutely positive that 416s and 515s go down to 8Hz and that the 802A HF driver can go out to 102kHz. I know it is hard to believe that you might be wrong. However, here are a few thoughts. Please be nice and don't put out a "hit" on me......

Do you mean "don't shoot the messenger"? Personally, I guess I can take it as long as you don't try to tell me there's also no Santa Claus......

[Panomaniac]

What? Next you'll be after the Easter Bunny.

I'd be glad to measure some. Do I have and 1" tangerines? Dunno. I agree with Bfish that it should be the same diaphragm. And I think the drivers should be remagged to be fair.

[voice of the theater]

Yeah, I would say you and Bfish are right--it has to be a "fair" test/comparison if we're going to learn anything meaningful....

[Ronald Lee]

So Pano, or others out there with measuring equipment, if you want to measure a few drivers it could still go a long way to debunk (or bunk?) Altec's claims about the Tangerine (this is starting to remind me of the TV show "Mythbusters" without all the cool explosions!)..... The Tangerine is an important part of Altec "lore" and I think Ronald posed a really interesting question when he started this thread. I think it would be nice to finally shed some light on Altec's 30+ year old claims about the Tangerine. If anyone out there finds links to published frequency response curves on some of these drivers (for comparative purposes), that would still help as well......



Do you mean "don't shoot the messenger"? Personally, I guess I can take it as long as you don't try to tell me there's also no Santa Claus......

Well, just kind of curious. What else would the typical of us old fogies think about while sitting around with their finger in their ears," literally, no pun intended.

Actually, today ordinary people have the means to do this stuff. 30+ years ago, the instrumentation required would have been in the realm of labs at Altec, JBL, & universities etc. The only thing we lack is one of those true anechoic chambers, but I bet someone out there has something that is pretty close.

Okay, "bring it on."

[Panomaniac]

At the frequencies measured, I don't think anechoic is needed for the horns. Gating would be enough.

[Baaronj]

Gents - I'm reviving this very old thread as I've been wondering the same as the OP about the differences between the radial and circumferential phase plugs.

I'm in a unique position to take some measurements here, as I've got a pair of 604-8gs, one with the radial "tangerine" phase plug, and one with the older circumferential.

After swapping crossovers and diaphragms between the two speakers, and swapping the speaker positions and rearranging the room, I have to say there is an audible difference between the two that I can't attribute to anything but the different phase plugs.

If y'all are interested, I could take some quick and dirty measurements of the two speakers using the same diaphragm and crossover. After that I'm sending one to Bill at GPA...he said he could install a tangerine in the older model for me (not sure if he can do the opposite).

Anyone care to guess the differences I hear between the two? They're clear and consistent....

I hate to admit to myself or the public that the differences are down to the phase plugs, but I've swapped everything I can think of between these two drivers. They've also both been refurbed/remagged by Bill somewhat recently, so demagging isn't an issue here.

Anyway, let me know if anyone is curious enough to want to see measurements and I'll do it.

I dont want to wait long though, the difference between the two is enough to my ears to be annoying. I have great hearing, but I think these differences would be audible to most anyone with decent hearing and a trained ear.

[mattvandyke]

I would be interested in the testing that you would be doing. It would be great to understand the difference in output between the two. Most of my drivers have the tangerine but not all of them.

Thanks
Matt

[BillWojo]

I too would be interested. What sort of measuring gear will you be using?

BillWojo

[wweigle]

I would be very interested in your comparison. Have a pair of both Altec 802-8g and 802d, both with GPA diaphragms. I never have been able to really hear the difference, but I have also never really spent the time to try to do a real comparison. This would be good stuff!