9844 8B HF driver

[leifchristensen]

hello folks
got hold of a pair of 9844 8Bs without HF drivers,otherwise they´re intact.
I know they normally are equipped with the 902s,but what version?
8A or 8B ?
can´t find it in the superlong 9844 thread here on the forum or elsewhere on the web

best
Leif
Norway

[Earl K]

hello folks
got hold of a pair of 9844 8Bs without HF drivers,otherwise they´re intact.
I know they normally are equipped with the 902s,but what version?
8A or 8B ?
can´t find it in the superlong 9844 thread here on the forum or elsewhere on the web

- Skywaves' 9844-8b(s) came equipped with Altec 902-8B(s) .
- His drivers came with 35480 diaphragms loaded into them .
- His 902s also came with plastic "loading caps" installed / but / with no metal back-caps.
- Skywave bought ( & installed ) the metal back-caps ( from GPA ) .

- This is the HFR ( high-frequency response ) one can expect from the 902/811b combo when using a Model 19 crossover ( instead of the stock 800f ) .
- This was measured by Zilch .
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=32400&stc=1&d=1209961283

- Here's the FR of the 9844 with the original crossover , as measured by SW-R ( Skywave ) using "FuzzMeasure" on his Mac computer .

Re-measured Atec 9844-8Bs with stock crossover and HF driver (902-8B) with Fuzzmeasure, 1 meter:
- funny how the 2300hz "bump" appears to be the same as what is found in the M19 network .
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=39184&d=1241907204

- Here's the HFR of the 802-8G on the 811b horn ( also with the M19 network ) as measured by Zilch ( these were Gary Ls' 802-8Gs with 23744 diaphragms )


http://audioheritage.org/vbulletin/attachment.php?attachmentid=24142&stc=1&d=1175669096
- Following is the response that JackGiff achieved when using BMS 4550 drivers on Altec 811b horns . ( I forget which network he used at the time .)
- He achieved almost ruler flat HF response with little effort ( on the 811b horn ) . :thmbsup:

http://audioheritage.org/vbulletin/attachment.php?attachmentid=24851&stc=1&d=1178422000

- Below is a measurement of mine of an 802-8D Alnico body loaded with the ( now obsolete ) 35480 diaphragm ( mounted onto a Sammi PH-230 BiRadial horn ) .
- I believe the network loss was @ 10db ( necessary, to flatten down the midrange ) .
- The plastic loading cap is in place . ( Sorry, I don't own any Altec horns ) .
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=39309&stc=1&d=1242576691

- Finally, is another FR of a 802-8T ( loading cap in place ) with a custom network .
- Network loss is a tad less than the previous pic ( here,, it's 7 to 8 db, due to midrange flattening ) .
- This driver has the 34647 diaphragm loaded into it ( this is the "soft aluminum" diaphragm that GPA presently sells ) .


http://www.audioheritage.org/photopost/data//500/Altec_802-8t_on_PH230_with-EQ_LCR_2.PNG


<> cheers :)

[leifchristensen]

whow great graphs!
interesting with the BMS drivers.....hmmmmm
it´s probably like swearing in the church, but...
thxs
best
Leif

[Earl K]

Hi Leif,

http://www.audioheritage.org/vbulletin/image.php?u=9046&dateline=1256993856 (http://www.audioheritage.org/vbulletin/showpost.php?p=208085&postcount=189)

- It's worth reading ( quite closely ) SWRs' conclusions, as contained within the single post that I've linked to ( click the above picture ) .

- This line ( from his post ) stands out ( to me ) .

" Generally the ( ALTEC ) 902 has more air. The ( BMS ) 4552 is drier ."

- That closely mirrors my own experence listening to drivers that have plastic/mylar domed diaphragms ( ie; the B&C brand in my case ) .

<> EarlK

[leifchristensen]

thxs Earl K
I went through that new quote several times
I´m expecting the 9844 8Bs at my door in a couple of days
then I´ll do some testing of the HF drivers on my own
I´ve got 902-8As and Bs,908-8Bs and 808-8Bs, so I´ve got work to do
In the meantime I´m playing on my Trio´s
best
Leif