291-A or 288-C in 511E, WTB?

[hifidiot]

Hello,

I have another question for this helpful forum: I am looking for a 1,4" ALNICO driver for my 511E horns.

Dispite the better clarity, HF response and lower colouration I prefer the 808 ALNICO+throat adapter above the ferrite 288-K. I believe this has much to do with the 'tone' of alnico adding something a friend called 'mushroom factor' to the sound. Looking at ebay prices for vintage alnico drivers I am probably not the only one.

Now I am faced with the challenge finding a suitable pair within the 'vintage' Altec catalog. I zeroed in on the 288-C and 291-A appearing to have a price within budget and having the desired design (radial phaseplug + alnico). I could find no specs on the 288-C although I can imagine they are similar drivers.

Am I right? Is there a reason to opt for another model?

I found this distributor on the net that seems to ask fair prices (compared to ebay):
Jammin Jersey. Might I be better off at some other place?

Thank you in advance,

regards, Coen

[Steve Mac]

I'm in the same boat.
I believe that the best route to audio nirvana may be through the Great Plains Audio Vintage Series. My understanding is, is that Bill at GPA can make a 288 alnico driver with the tangerine radial phase plug. I can't help but think this is a very good direction to pursue. Information is scant on the great plains audio website. I'm wondering if Todd White might chime in here and clarify developments in re-introducing vintage series products. I am very interested in compression driver development. I remember a post concerning the high price of alnico magnet...but I thought that even at the higher price...that you get new for a better price than trying to play the "I bought it on eBay for 50 bucks and it works perfectly...then I found out it's going to cost x amount of dollars to fix and ENSURE perfection". I haven't been that lucky....and I'd like to see gpa make more money.

[hifidiot]

Steve,

I have to limit my budget to keep out of a personal 'credit crisis', since there are too many wonderfull toys and gadgets around I like to own and explore.

If GPA is moving on with its classic series it has my fiat. I'd rather save a little and buy a new unit than taking the risk of discovering that the units need a fix after all. Otoh all in proper price perspective.

Regarding the 288 K (with the tangerine(r) phaseplug slots), I assumed that the reason I liked the 808 better was ALNICO, still it could be the phaseplug as well...

I am not sure if in my situation (hifi application) the extra HF is desirable. The Jean Hiraga loudpeaker book I own has a paragraph about the law of 400.000. This is not an exact law, but it illustrates that you can maintain a perceived frequency balance if the produkt of the lower Fc and higher Fc remains 400.000 (20Hz X 20 K Hz = 400.000 but also 40Hz X 10 KHz). With a 828/515G cut off of 50Hz the 'law' will result in 8KHz highs. I remember an extra table with experimental values stating you can go higher without serious offset. I won't mourn on a couple of Khz extra HF bandwidth.

regards, Coen

[Vathek]

The 288-C and the 291-A are actually identical except for the diaphragm. I don't know where you got your prices from, but 291's are not that expensive on ebay, certainly cheaper than what jammin jersey is asking. I paid 260$ for a pair of 291-Bs on ebay just recently. With the GPA remag and new diaphragms, they'll become a perfect pair of 288-Gs up to spec for about 500$. If that ain't cheap for what is usually considered the best large format driver altec ever made, I don't know what is (not considering the massive shipping costs, I'm also in Europe).
Just keep looking, prices seem to vary considerably, and maybe go for blown ones, since you'll want to ship them to GPA anyway for at least a remag - unless you were running a museum and just had to have that bakelite ring of your vintage diaphragms on display...
Good luck hunting

PS: with this 808 vs 288 you're making a comparison between quite different drivers, where the material of the magnet most likely hast the least influence.

[GM]

Well, he adapted the old rule-of-thumb of 25*20 kHz = 500,000 to suit a 20*20 kHz BW, so under the original 'law' it would be 40-12.5 kHz. If you only listened to BW limited FM, then the factor would be 30*15 kHz = 450,000, so if you're going to use this, calc the one that best fits the source BW.

GM

[speakerdave]

Originally posted by hifidiot:
. . . . I zeroed in on the 288-C and 291-A appearing to have a price within budget and having the desired design (radial phaseplug + alnico). I could find no specs on the 288-C although I can imagine they are similar drivers. . . . .

<font size="2" face="Verdana, Helvetica, sans-serif">Perhaps you meant the 288-G, I dunno. The 288C is an older member of the series with a smaller magnet. The 288-G and the 291 are of the same era and are identical except for original diaphragm, I believe.

<font color="#FFFFFF" size="1">[ October 21, 2008 08:53 PM: Message edited by: speakerdave ]</font>

[Old Guy]

Originally posted by speakerdave:
[

<font size="2" face="Verdana, Helvetica, sans-serif">Perhaps you meant the 288-G, I dunno. The 288C is an older member of the series with a smaller magnet. The 288-G and the 291 are of the same era and are identical except for original diaphragm, I believe.

<font color="#FFFFFF"><font size="1">[ October 21, 2008 08:53 PM: Message edited by: speakerdave ]</font></font>[/QB][/QUOTE]


Sort of right Dave.

The 291A is the same vintage as 288C and D. Identical except the pragm, which has a mylar surround on the 291 and aluminum on the 288.

The 291- 16B and the 288G are essentially the same driver, with the same difference. Later models of these can have tangerines.

288H is kinda by itself...Tangerine and Aluminum, and Alnico.

Then came the ceramic versions, no 291 though. Was supplanted by the 299, which has a higher power diaphragm, and improved HF vs the 291 series.

Alnico
291A
288c or D

then (big Alnico)
291B
288G then H with Tangerine

Ceramic
299
288K etc.

HTH.

[hifidiot]

Thanx all!

I allready thought the pre tangerine drivers are very similar save the magnet type and mass. I will keep an eye on blown 291 B's on ebay. I guess I can have them shipped directly to GPA for full service.

Regarding the Hiraga 'fidelity' rule, this is the actual table of 'excellent tonal balance':

low high perceived loss of fidelity
20 20K 0%
40 15K 1%
70 12K 3%
80 9K 6%
100 6K 14%
220 3K5 50%
270 3K 60%

This concurs with my own experience with full range drivers and the fine balance I attain with the A7 without eq-ing the high and low end (I eq the 150Hz horn step though).

regards, Coen

[oface1]

O G,

I am a little confused by your post, are you saying there wasn't any 291's mud magnet types with the tnagerine phase plug?

I have some 291-16k's that are mud magnets and have the tangerine phase plug.

Here's a link to mine.

101_0021 on Flickr - Photo Sharing!@@AMEPARAM@@http://farm4.static.flickr.com/3259/2691360440_720b3ee4a8.jpg?v=0@@AMEPARAM@@269136044 0@@AMEPARAM@@720b3ee4a8

Just curious......

-chris

<font color="#FFFFFF" size="1">[ October 22, 2008 08:45 AM: Message edited by: oface1 ]</font>

[Steve Mac]

291b's were the last of the 291 alnicos I believe.
http://www.wmeckle.com/INTRO/LARGE/Altec.htm